# Patent

## Title
Human somatostatin-like receptor

## Abstract

This application is a division of co-pending application Ser. No. 08/311,703 filed Sep. 23, 1994, which is a File Wrapper Continuation of Ser. No. 07/786,063, filed Oct. 31, 1991, now abandoned.

## Background
Transforming growth factor-beta (TGF-.beta.) is a member of a family of structurally related cytokines that elicit a variety of responses, including growth, differentiation, and morphogenesis, in many different cell types. (Roberts, A. B. and M. B. Sporn, In: Peptide Growth Factors and Their Receptors, Springer-Verlag, Heidelberg, pp. 421-472 (1990); Massague, J., Annu. Rev. Cell. Biol. 6:597-641 (1990)). In vertebrates at least five different forms of TGF-.beta., termed TGF-.beta.1 to TGF-.beta.5, have been identified; they all share a high degree (60%-80%) of amino-acid sequence identity. While TGF-.beta.1 was initially characterized by its ability to induce anchorage-independent growth of normal rat kidney cells, its effects on most cell types are anti-mitogenic. (Altschul, S. F. et al., J. Mol. Biol. 215:403-410 (1990); Andres, J. L. et al., J. Cell. Biol. 109:3137-3145 (1989)). It is strongly growth-inhibitory for many types of cells, including both normal and transformed epithelial, endothelial, fibroblast, neuronal, lymphoid, and hematopoietic cells. In addition, TGF-.beta. plays a central role in regulating the formation of extracellular matrix and cell-matrix adhesion processes.

In spite of its widespread effects on cell phenotype and physiology, little is known about the biochemical mechanisms that enable TGF-.beta. family members to elicit these varied responses. Three distinct high-affinity cell-surface TGF-.beta.-binding proteins, termed type I, II and III, have been identified by incubating cells with radiolabelled TGF-.beta.1, cross-linking bound TGF-.beta.1 to cell surface molecules, and analyzing the labelled complexes by polyacrylamide gel electrophoresis. (Massague, J. and B. Like, J. Biol. Chem. 260:2636-2645 (1985); Cheifetz, S. et al. J. Biol. Chem. 261:9972-9978 (1986).) The binding constants are about 5-50 pM for the type I and II receptor and 30-300 pM for the type III receptor. (Boyd, F. T. and J. Massague, J. Biol. Chem. 264:2272-2278 (1989)).

The type I and II receptors, of estimated 53 and 70-100 kilodaltons mass respectively, are N-glycosylated transmembrane proteins that are similar in many respects. Each of these receptors has a distinct affinity for each member of the TGF-.beta. family of ligands. (Boyd, F. T. and J. Massague, J. Biol. Chem. 264:2272-2278 (1989)). In contrast, the type III receptor shows comparable affinities for all TGF-.beta. isotypes; the type III receptor is the most abundant cell-surface receptor for TGF-.beta. in many cell lines (upwards of 200,000 per cell), and is an integral membrane proteoglycan. It is heavily modified by glycosaminoglycan (GAG) groups, and migrates heterogeneously upon gel electrophoresis as proteins of 280 to 330 kilodaltons. When deglycosylated with heparitinase and chondrontinase, the protein core migrates as a 100-110 kilodalton protein. The TGF-.beta. binding site resides in this protein core, as non-glycosylated forms of this receptor that are produced in cell mutants defective in GAG synthesis are capable of ligand binding with affinities comparable to those of the natural receptor. (Cheifetz, S. and J. Massague, J. Biol. Chem., 264:12025-12028 (1989). A variant form of type III receptor is secreted by some types of cells as a soluble molecule that apparently lacks a membrane anchor. This soluble species is found in low amounts in serum and in extracellular matrix.

The type III receptor, also called betaglycan, has a biological function distinct from that of the type I and II receptors. Some mutant mink lung epithelial cell (Mv1Lu) selected for loss of TGF-.beta. responsiveness no longer express type I receptors; others, similarly selected, lose expression of both the type I and II receptors. However, all these variants continue to express the type III receptor. (Boyd, F. T. and J. Massague, J. Biol. Chem. 264:2272-2278 (1989); Laiho, M. et al., J. Biol. Chem. 265:18518-18524 (1990)). This has led to the proposal that types I and II receptors are signal-transducing molecules while the type III receptor, may subserve some other function, such as in concentrating ligand before presentation to the bona fide signal-transducing receptors. The secreted form of type III receptor, on the other hand, may act as a reservoir or clearance system for bioactive TGF-.beta..

Additional information about each of these TGF-.beta. receptor types would enhance our understanding of their roles and make it possible, if desired, to alter their functions.

The present invention relates to isolation, sequencing and characterization of DNA encoding the TGF-.beta. type III receptor of mammalian origin and DNA encoding the TGF-.beta. type II receptor of mammalian origin. It also relates to the encoded TGF-.beta. type III and type II receptors, as well as to the soluble form of each; uses of the receptor-encoding genes and of the receptors themselves; antibodies specific for TGF-.beta. type III receptor and antibodies specific for TGF-.beta. type II receptor. In particular, it relates to DNA encoding the TGF-.beta. type III receptor of rat and human origin, DNA encoding the TGF-.beta. type II receptor of human origin and homologues of each.

The TGF-.beta. receptor-encoding DNA of the present invention can be used to identify equivalent TGF-.beta. receptor type III and type II genes from other sources, using, for example, known hybridization-based methods or the polymerase chain reaction. The type III receptor gene, the type II receptor gene or their respective encoded products can be used to alter the effects of TGF-.beta. (e.g., by altering receptivity of cells to TGF-.beta. or interfering with binding of TGF-.beta. to its receptor), such as its effects on cell proliferation or growth, cell adhesion and cell phenotype. For example, the TGF-.beta. receptor type III gene, the TGF-.beta. receptor type II gene, or a truncated gene which encodes less than the entire receptor (e.g., soluble TGF-.beta. type III receptor, soluble TGF-.beta. type II receptor or the TGF-.beta. type III or type II binding site) can be administered to an individual in whom TGF-.beta. effects are to be altered. Alternatively, the TGF-.beta. type III receptor, the TGF-.beta. type II receptor, a soluble form thereof (i.e., a form lacking the membrane anchor) or an active binding site of the TGF-.beta. type III or the type II receptor can be administered to an individual to alter the effects of TGF-.beta..

Because of the many roles TGF-.beta. has in the body, availability of the TGF-.beta. receptors described herein makes it possible to further assess TGF-.beta. function and to alter (enhance or diminish) its effects.

FIGS. 1A-1C (SEQ ID NOS: 5 and 6) is the DNA sequence and the translated amino acid sequence of type III TGF-.beta.1 receptor cDNA clone R3-OFF (full insert size 6 kb), in which the open reading frame with flanking sequences of the clone are shown. The transmembrane domain is indicated by a single underline. Peptide sequences from purified type III receptor, mentioned in text, that correspond to the derived sequence, are in italics and underlined. Potential N-linked glycosylation sites are indicated by #, and extracellular cysteines by &. A consensus protein kinase C phosphorylation site is indicated by $. The last non-vectorencoded amino acid of Clone R3-OF (2.9 kb) is indicated by @. Consensus proteoglycan attachment site is indicated by +++. Other potential glycosaminoglycan attachment sites are indicated by +. The upstream in-frame stop codon (-42 to -44) is indicated by a wavy line. Signal peptide cleavage site predicted by vonHeijne's algorithm (von Heijne, G., Nucl. Acid. Res. 14:4683-4690 (1986) is indicated by an arrow.

The subject invention is based on the isolation and sequencing of DNA of vertebrate, particularly mammalian, origin which encodes TGF-.beta. type III receptor and DNA of mammalian origin which encodes TGF-.beta. type II receptor, expression of the encoded products and characterization of the expressed products. As described, a full-length cDNA which encodes TGF-.beta. receptor type III has been isolated from a cDNA library constructed from a rat vascular smooth muscle cell line and a full-length cDNA which encodes TGF-.beta. type II receptor has been isolated from a human cDNA library. The human homologue of the type III gene has also been cloned. A deposit of human TGF-.beta. type III cDNA in the plasmid pBSK has been made under the terms of the Budapest Treaty at the American Type Culture Collection (Oct. 21, 1991) under Accession Number 75127. All restrictions upon the availability of the deposited material will be irrevocably removed upon granting of a U.S. patent based on the subject application.

Isolation and Characterization of TGF-.beta. Type III Receptor

As described herein, two separate strategies were pursued for the isolation of the TGF-.beta. type III receptor cDNA. In one approach, monoclonal antibodies were generated against the type III receptor protein and used to purify the receptor, which was then subjected to microsequencing. (See Example 1) Microsequencing of several peptides resulting from partial proteolysis of the purified receptor produced four oligopeptide sequences, which were used to construct degenerate oligonucleotides. The degenerate oligonucleotides were used either as primers in a cloning strategy using the polymerase chain reaction (PCR) or as probes in screening cDNA libraries. Although this strategy did not prove to be productive, the oligopeptide sequences were useful in verifying the identity of the receptor clones isolated by the second strategy.

In the second approach to isolating TGF-.beta. receptor-encoding clones, an expression cloning strategy was used in COS cells; direct visualization of receptor positive cells was used to isolate receptor cDNAs. (See Example 2) In this approach, a cDNA library was constructed from A-10 cells, a rat vascular smooth muscle cell line which expresses all three TGF-.beta. receptors (type I, II and III). COS cells transfected with cDNA components of this library in a vector carrying the cytomegalovirus (CMV) transcriptional promoter and the SV40 origin of replication were screened to identify cells expressing substantially higher than normal levels of TGF-.beta. receptor. One transfectant expressing such high levels of a TGF-.beta. binding protein was identified and the original pool of expression constructs from which it was derived was split into subpools, which were subjected to a second round of screening. Two further rounds of sib-selection resulted in isolation of one cDNA clone (R3-OF) with a 2.9 kb insert which induced high levels of TGF-.beta.-binding proteins in approximately 10% of cells into which it was introduced. The specificity of the TGF-.beta. binding was validated by showing that addition of a 200-fold excess unlabeled competitor TGF-.beta.1 strongly reduced binding of 125 I-TGF-.beta. to transfected cells.

The R3-OF cDNA encoded an open reading frame of 817 amino acid residues, but did not contain a stop codon. R3-OF was used as a probe to isolate a full-length cDNA from a rat 208F library. The resulting clone, R3-OFF, is 6 kb in length and encodes a protein of 853 amino acids, which is colinear with clone R3-OF. The nucleotide sequence of R3-OFF is shown in FIGS. 1A-1C, along with the translated amino acid sequence.

Characterization of the receptor encoded by R3-OFF was carried out, as described in Example 3. Results showed three distinct TGF-.beta. binding protein species of TGF-.beta. on the surface of mock-transfected COS cells, which is in accord with results reported by others. (Massague, J. et al., Ann. NY Acad. Sci. 593:59-72 (1990)). These included the two lower molecular weight type I and II receptors (65 and 85 kD) and the higher molecular weight type III proteoglycan, which migrates as a diffuse band of 280-330 kd. Enzymatic removal of the proteoglycan yielded a core protein of approximately 100 kd. Binding to all three receptor types is specific in that it was competed by 200-fold excess of unlabeled TGF-.beta.1.

Transfecting the isolated cDNA caused a two-fold increase in expression of the type III receptor. When a cell lysate derived from COS cells transfected with clone R3-OFF was treated with deglycosylating enzymes, the heterogeneous 280-330 kd band was converted to a protein core which co-migrates with the type III protein core seen in parental A10 cells. Importantly, the recombinant protein core migrated differently from the endogenous COS cell type III protein core.

These observations were confirmed and extended using stably transfected cells expressing the type III cDNA. L6 rat skeleton muscle myoblasts do not express any detectable type III mRNA and no endogeneous surface type III receptor (Massague et al., 1986; Segarini et al., 1989). These cells were transfected with the isolated cDNA in the vector pcDNA-neo. Cell clones stably expressing this clone in both the forward and reverse orientations with respect to the CMV promoter were isolated and analyzed by ligand binding assay.

Introduction of either the full-length clone R3-OFF or the partial clone R3-OF in the forward orientation resulted in expression of type III receptor. L6 cells transfected with the cDNA clones in the reverse orientation did not express this protein. Importantly, the apparent size of the protein core of the type III receptor in cells transformed with the R3-OF clone is smaller than that from R3-OFF transformed cells, consistent with the difference in the sizes of the protein cores predicted from their nucleic acid sequences.

Surprisingly, binding of radio-labeled ligand to the type II receptor was increased by 2.5 fold in cells expressing the type III cDNA. Binding to the type I receptor was unchanged. This apparently specific up-regulation of ligand-binding to the type II receptor was evident in all of the 15 stably transfected L6 cell lines analyzed to date. Furthermore, this effect seems to be mediated equally well by the full-length clone or a truncated clone (R3-OF) that lacks the cytoplasmic domain of TGF-.beta. type III receptor was expressed.

Expression of type III receptor mRNA was assessed by Northern blot analysis and RNA blot analysis. Northern gel analysis showed that the type III receptor mRNA is expressed as a single 6 kb message in several rat tissues. RNA dot blot analysis of several different tissue culture cell lines was also carried out. Cells of mouse origin (MEL and YHl6) appear to express a smaller (.about.5.5 kb) message for the type III mRNA than those of pig, rat and human origin. In all of these cells, expression or absence of the type III mRNA is consistent with the expression or absence of detectable cell surface type III receptors, with the notable exception of the retinoblastoma cell lines (Y79, Weri-1, Weri-24, and Weri-27). These cells lack detectable surface expression of type III receptor, which confirms an earlier report. (Kimchi, A. et al., Science 240:196-198 (1988)). It is striking that the type III receptor mRNA is expressed in these cells at a level comparable to that of other cells that do indeed express type III receptor proteins at readily detectable levels. It appears that TGF-.beta. receptor III expression, which is substantial in normal retinoblasts (AD12), has been down-regulated in these retinoblastoma tumor cells, perhaps through post-transcriptional mechanisms.

The nucleotide sequence full reading frame along with flanking sequences of the full-length cDNA clone R3-OFF was determined and is presented in FIGS. 1A-1C. The reading frame encodes a protein of 853 amino acid residues, which is compatible with the 100 kD size observed for the fully deglycosylated TGF-.beta.1 type III receptor. The identity of the receptor as TGF-.beta. type III was verified by searching for segments of the putative transcription product which included the peptide sequences determined by microsequencing of the isolated type III receptor. (See Example 1) As indicated in FIGS. 1A-1C, two segments of derived protein (underlined and italicized, residues 378-388 and 427-434) precisely match with the amino acid sequences of two peptides (I and III) determined from direct biochemical analysis of the purified type III receptor.

Further analysis showed that TGF-.beta. type III binding protein has an unusual structure for a cytokine receptor. Hydropathy analysis indicates that the protein includes a N-terminal signal sequence, followed by a long, hydrophilic N-terminal region. A 27 residue region of strong hydrophobicity (underlined in FIGS. 1A-1C, residues 786-812) toward the C-terminus represents the single putative transmembrane domain. This suggests that nearly all of the receptor which is an N-terminal extracellular domain is anchored to the plasma membrane near its C-terminus. A relatively small C-terminal tail of 41 residues represents the cytoplasmic domain.

Analysis of related sequences provides few clues to function of TGF-.beta. type III protein. Only one other gene described to date, a glycoprotein expressed in high quantities by endothelial cells and termed endoglin, contains a related amino acid sequence. The most homologous regions between the sequences of the type III receptor and endoglin (74%) falls primarily in the putative transmembrane and cytoplasmic domains. Similar to the general structure of type III receptor, endoglin is a glycoprotein which contains a large hydrophilic N-terminal domain which is presumably extracellular, followed by a putative transmembrane domain and a short cytoplasmic tail of 47 amino acid residues. The biological role of endoglin is still unclear at present, although it has been suggested that it may involved in cell-cell recognition through interactions of an "RGD" sequence on its ectodomain with other adhesion molecules. Unlike the TGF-.beta. type III receptor, endoglin does not carry GAG groups.

Isolation of TGF-.beta. Type II Receptor

The cDNA encoding the type II TGF-.beta. receptor was also isolated, using expression cloning in COS cells. A full-length cDNA (designated clone 3FF) was isolated by high stringency hybridization from a human HepG2 cell cDNA library. Analysis showed that the corresponding message is a 5 kb message which is expressed in different cell lines and tissues. Sequence analysis indicated that the cDNA has an open reading frame encoding a core 567 amino acid residue protein. The nucleotide sequence of the full-length type II TGF-.beta. receptor cDNA clone 3FF is shown in SEQ ID NO: 7; the amino acid sequence is represented in SEQ ID NO: 8.

The 567 amino acid residue protein has a single putative transmembrane domain, several consensus glycosylation sites, and a putative intracellular serine/threonine kinase domain. The predicted size of the encoded protein core is .about.60 kd, which is too large for a type I TGF-.beta. receptor. Instead, crosslinking experiments using iodinated TGF-.beta. and COS cells transiently transfected with clone 3FF shows over-expression of a protein approximately 70-80 kd which corresponds to the size of type II TGF-.beta. receptors. Thus, clone 3FF encodes a protein that specifically binds TGF-.beta. and has an expressed protein size of 70-80 kd, both characteristic of the type II TGF-.beta. receptor.

Plasmid 3FF was deposited in accordance with the provisions of the Budapest Treaty at the American Type Culture Collection (ATCC), 12301 Parklawn Drive, Rockville, Md. 20852, U.S.A. on Nov. 12, 1997, and assigned Accession Number ATCC 209455.

Uses of the Cloned TGF-.beta. Receptors and Related Products

For the first time, as a result of the work described herein, DNAs encoding two of the three high affinity cell-surface TGF-.beta. receptors have been isolated, their sequences and expression patterns determined and the encoded proteins characterized. Expression of the TGF-.beta. type III receptor in cells which do not normally express the receptor, followed by ligand binding assay, verified that the cloned type III receptor-encoding DNA (i.e., either the full-length clone R3-OFF or the partial clone R3-OF) encoded the receptor. In addition, the work described herein resulted in the surprising finding that binding of TGF-.beta. to type II receptors in cells expressing the type III DNA was increased by 2.5 fold.

Additional insight into the role of the TGF-.beta. type III receptor and its interaction with TGF-.beta. type II receptor is a result of the work described. For example, the role of TGF-.beta. type III receptor is unclear, but it has been proposed that it serves a most unusual function of attracting and concentrating TGF-.beta.s for eventual transfer to closely situated signal-transducing receptors. While most cytokines bind to a single cell surface receptor, members of the TGF-.beta. family bind with greater or lesser affinity to three distinct cell surface proteins. This has raised the question of why these three receptors are displayed by most cell types and whether they subserve distinct functions. Evidence obtained to date suggests that the type III receptor may perform functions quite different from those of types I and II. Thus, type III is substantially modified by GAGs while types I and II appear to carry primarily the N-linked (and perhaps O-linked) sidechains that are characteristic of most growth factor receptors. In addition, variant cells that have been selected for their ability to resist TGF-.beta.-induced growth inhibition show the absence of Type I or Type II receptors while continuing to display Type III receptors. Together, these data have caused some to propose that the Type I and II receptors represent bona fide signal-transducing receptors while the type III receptor, described here, plays another distinct role in the cell.

It remains possible that the type III receptor serves a most unusual function of attracting and concentrating TGF-.beta.s on the cell surface for eventual transfer to closely situated signal-transducing receptors. Such a function would be unprecedented for a proteinaceous receptor, although heparin sulfate has been shown to activate basic FGF by binding to this growth factor prior to FGF association with its receptor (Yayon, A. et al., Cell 64:841-848 (1991)). Parenthetically, since the type III receptor also contains large quantities of heparan sulfate side-chains, it may also bind and present basic FGF to its receptor.

Evidence that is consistent with the role for the type III receptor comes from the work with L6 rat myoblast cells which is described herein. As described above, in L6 cells overexpressing type III receptor, the binding of radiolabelled TGF-.beta. to the type II receptor is increased several fold when compared with that seen with parental cells. Further assessment of TGF-.beta. type III function and interaction with type II and type I receptors will be needed to answer these questions and can be carried out using the materials and methods described here.

TGF-.beta. receptors, both type III and type II, can be identified in other species, using all or a portion of the DNA encoding the receptor to be identified as a probe and methods described herein. For example, all or a portion of the DNA sequence encoding TGF-.beta. type III receptor (shown in FIGS. 1A-1C) or all or a portion of the DNA sequence encoding TGF-.beta. type II receptor (shown in SEQ ID NO: 7) can be used to identify equivalent sequences in other animals. Stringency conditions used can be varied, as needed, to identify equivalent sequences in other species. Once a putative TGF-.beta. receptor type III or type II-encoding sequence has been identified, whether it encodes the respective receptor type can be determined using known methods, such as described herein for verification that the cDNA insert of full-length clone R3-OFF and the cDNA insert of partial clone R3-OF encode the type III receptor. For example, DNA isolated in this manner can be expressed in an appropriate host cell which does not express the receptor mRNA or the surface receptor (e.g., L6 rat skeleton muscle myoblasts) and analyzed by ligand binding (TGF-.beta. binding) assay, as described herein.

Also as a result of the work described herein, antibodies (polyclonal or monoclonal) specific for the cloned TGF-.beta. type III or the clones TGF-.beta. type II receptor can be produced, using known methods. Such antibodies and host cells (e.g., hybridoma cells) producing the antibodies are also the subject of the present invention. Antibodies specific for the cloned TGF-.beta. receptor can be used to identify host cells expressing isolated DNA thought to encode a TGF-.beta. receptor. In addition, antibodies can be used to block or inhibit TGF-.beta. activity. For example, antibodies specific for the cloned TGF-.beta. type III receptor can be used to block binding of TGF-.beta. to the receptor. They can be administered to an individual for whom reduction of TGF-.beta. binding is desirable, such as in some fibrotic disease (e.g., of skin, kidney and lung).

DNA and RNA encoding TGF-.beta. type III receptor and DNA and RNA encoding TGF-.beta. type II receptor are now available. As used herein, the term DNA or RNA encoding the respective TGF-.beta. receptor includes any oligodeoxynucleotide or oligodeoxyribonucleotide sequence which, upon expression, results in production of a TGF-.beta. receptor having the functional characteristics of the TGF-.beta. receptor. That is, the present invention includes DNA and RNA which, upon expression in an appropriate host cell, produces a TGF-.beta. type III receptor which has an affinity for TGF-.beta. similar to that of the TGF-.beta. type III receptor on naturally occurring cell surfaces (e.g., it shows comparable affinities for all TGF-.beta. isotypes). Similarly, the present invention includes DNA and RNA which, upon expression in an appropriate host cell, produces a TGF-.beta. type II receptor which has an affinity for TGF-.beta. similar to that of TGF-.beta. type II receptor on naturally occurring cell surfaces (e.g., it has a distinctive affinity for each member of the TGF-.beta. family of ligands similar to that of the naturally occurring TGF-.beta. type II receptor). The DNA or RNA can be produced in an appropriate host cell or can be produced synthetically (e.g., by an amplification technique such as PCR) or chemically.

The present invention also includes the isolated TGF-.beta. type III receptor encoded by the nucleotide sequence of full-length R3-OFF, the isolated TGF-.beta. type III receptor encoded by the nucleotide sequence of partial clone R3-OF, the isolated TGF-.beta. type II receptor encoded by the nucleotide sequence of full-length clone 3FF and TGF-.beta. type III and type II receptors which bind TGF-.beta. isotypes with substantially the same affinity. The isolated TGF-.beta. type III and type II receptors can be produced by recombinant techniques, as described herein, or can be isolated from sources in which they occur naturally or synthesized chemically. As used herein, the terms cloned TGF-.beta. type III and cloned TGF-.beta. type II receptors include the respective receptors identified as described herein, and TGF-.beta. type III and type II receptors (e.g., from other species) which exhibit substantially the same affinity for the TGF-.beta. isotypes as the respective receptors.

As described previously, cells in which the cloned TGF-.beta. type III receptor is expressed bind TGF-.beta. in essentially the same manner as do cells on which the type III receptor occurs naturally. Further analysis of ligand interactions with the cloned TGF-.beta. type III receptor, based upon site-directed mutagenesis of both TGF-.beta. and the receptor, can be carried out to identify residues important for binding. For example, DNA having the sequence of FIGS. 1A-1C can be altered by adding, deleting or substituting at least one nucleotide, in order to produce a modified DNA sequence which encodes a modified cloned TGF-.beta. type III receptor. The functional characteristics of the modified receptor (e.g., its TGF-.beta.-binding ability and association of the binding with effects normally resulting from binding) can be assessed, using the methods described herein. Modification of the cloned TGF-.beta. type III receptor can be carried out to produce, for example, a form of the TGF-.beta. type III receptor, referred to herein as soluble TGF-.beta. receptor, which is not membrane bound and retains the ability to bind the TGF-.beta. isotypes with an affinity substantially the same as the naturally-occurring receptor. Such a TGF-.beta. type III receptor could be produced, using known genetic engineering or synthetic techniques; it could include none of the transmembrane region present in the naturally-occurring TGF-.beta. type III receptor or only a small portion of that region (i.e., small enough not to interfere with its soluble nature). For example, it can include amino acids 1 through 785 of the TGF-.beta. type III sequence of FIGS. 1A-1C or a portion of that sequence sufficient to retain TGF-.beta. binding ability (e.g., amino acids 24-785, which does not include the signal peptide cleavage site present in the first 23 amino acids). A soluble TGF-.beta. type II receptor (e.g., one which does not include the transmembrane and cytoplasmic domains) can also be produced. For example, it can include amino acids 1 through 166, inclusive, of SEQ ID NO: 8 or a sufficient portion thereof to retain TGF-.beta. binding ability substantially the same as that of TGF-.beta. type II receptor.

The TGF-.beta. type III receptor and/or type II receptor can be used for therapeutic purposes. As described above, the TGF-.beta. family of proteins mediate a wide variety of cellular activities, including regulation of cell growth, regulation of cell differentiation and control of cell metabolism. TGF-.beta. may be essential to cell function and most cells synthesize TGF-.beta. and have TGF-.beta. cell surface receptors. Depending on cell type and environment, the effects of TGF-.beta. vary: proliferation can be stimulated or inhibited, differentiation can be induced or interrupted and cell functions can be stimulated or suppressed. TGF-.beta. is present from embryonic stages through adult life and, thus, can affect these key processes throughout life. The similarities of a particular TGF-.beta. (e.g., TGF-.beta.1) across species and from cell to cell are considerable. For example, the amino acid sequence of a particular TGF-.beta. and the nucleotide sequence of the gene which encodes it regardless of source, are essentially identical across species. This further suggests that TGF-.beta. has a critical role in essential processes.

Specifically, TGF-.beta. has been shown to have anti-inflammatory and immune suppression capabilities, to play an important role in bone formation (by increasing osteoblast activity), inhibit cancer cell proliferation in culture, and control proliferation of glandular cells of the prostate. As a result, it has potential therapeutic applications in altering certain immune system responses (and possibly in modifying immune-mediated diseases); in treating systemic bone disease (e.g., osteoporosis) and conditions in which bone growth is to be enhanced (e.g., repair of broken bones) and in controlling growth and metastasis of cancer cells. In addition, TGF-.beta. appears to play a role in determining whether some cell types undergo or do not undergo mitosis. In this respect, TGF-.beta. may play an important role in tissue repair. Some diseases or conditions appear to involve low production or chronic overproduction of TGF-.beta.. (For example, results of animal studies suggest that there is a correlation between the over production of TGF-.beta. and diseases characterized by fibrosis in the lung, kidney, liver or in viral mediated immune expression.)

Clearly, TGF-.beta. has key roles in body processes and numerous related potential clinical or therapeutic applications in wound healing, cancer, immune therapy and bone therapy. Availability of TGF-.beta. receptor genes, the encoded products and methods of using them in vitro and in vivo provides an additional ability to control or regulate TGF-.beta. activity and effect in the body. For example, the TGF-.beta. type II or type III receptor encoded by the type II or the type III receptor genes of the subject invention can be used, as appropriate, to alter the effects of TGF-.beta. (e.g., to enhance the effect of TGF-.beta. in the body or to inhibit or reduce (totally or partially) its effects). It is also possible to administer to an individual in whom TGF-.beta. bound to TGF-.beta. type III receptor, such as soluble TGF-.beta. type III receptor. The present invention provides both a TGF-.beta. agonist and a TGF-.beta. antagonist. For these purposes, DNA gene encoding the entire TGF-.beta. type II or type III receptor, the encoded type II or type III receptor or a soluble form of either receptor can be used. Alternatively, antibodies or other ligands designed based upon these sequences or specific for them can be used for this purpose.

Knowledge of the amino acid sequences of TGF-.beta. type III and type II receptors makes it possible to better understand their structure and to design compounds which interfere with binding of the receptor with TGF-.beta.. It makes possible identification of existing compounds and design of new compounds which are type III and/or type II receptor antagonists.

Cells expressing the type III and/or type II receptors of the present invention can be used to screen compounds for their ability to interfere with (block totally or partially) TGF binding to the receptors. For example, cells which do not express TGF-.beta. type III receptor (e.g., L6 rat skeleton muscle myoblasts) but have been modified to do so by incorporation of the type III cDNA in an appropriate vector can be used for this purpose. A compound to be assessed is added, for example, to tissue culture dishes containing type III expressing cells, along with labeled TGF-.beta.. As a control, the same concentration of labeled TGF-.beta. is added to tissue culture dishes containing the same type of cells. After sufficient time for binding of TGF-.beta. to the receptor to occur, binding of labeled TGF-.beta. to the cells is assessed, using known methods (e.g., by means of a gamma counter) and the extent to which it occurred in the presence and in the absence of the compound to be assessed is determined. Comparison of the two values show whether the test compound blocked TGF-.beta. binding to the receptor (i.e., less binding in the presence of the compound than in its absence is evidence that the test compound has blocked binding of TGF-.beta. to the TGF-.beta. type III receptor).

Alternatively, a cell line expressing the TGF-.beta. receptor or cells expressing microinjected TGF-.beta. receptor RNA, can be used to assess compounds for their ability to block TGF-.beta. binding to the receptor. In this embodiment, a compound to be assessed is added to tissue culture dishes containing the cell line cells expressing microinjected TGF-.beta. receptor RNA, along with TGF-.beta.. As a control, TGF-.beta. alone is added to the same type of cells expressing microinjected endothelin receptor RNA. After sufficient time for binding of TGF-.beta. to the receptor to occur, the extent to which binding occurred is measured, both in the presence and in the absence of the compound to be assessed. Comparison of the two values shows whether the compound blocked TGF-.beta. binding to the receptor. The TGF-.beta. type III and type II receptors can also be used to identify TGF-.beta. -like substances, to purify TGF-.beta. and to identify TGF-.beta. regions which are responsible for binding to the respective receptors. For example, the type III receptor can be used in an affinity-based method to identify substances which bind the receptor in a manner similar to TGF-.beta..

The invention will now be illustrated by the following examples, which are not intended to be limiting in any way.

Materials and methods used in Examples 1-5 are described below.

Materials

The following is a description of materials used in the work described herein.

Recombinant human TGF-.beta.1 was provided by Rik Derynck of Genentech. COS-M6 cells were provided by Brian Seed of the Massachusetts General Hospital and Alejandro Aruffo of Bristol-Myers-Squibb. Heparitinase was provided by Tetsuhito Kojima and Robert Rosenberg of MIT. LLC-PK.sub.1 cells were a gift of Dennis Ausiello of the Massachusetts General Hospital. YH-16 cell were a gift of Edward Yeh of the Massachusetts General Hospital. 3-4 cells were a gift of Eugene Kaji of the Whitehead Institute for Biomedical Research. All other cell lines were purchased from ATCC and grown as specified by the supplier, except as noted.

Expression Cloning

Construction of cDNA Library and Generation of Plasmid Pools

10 .mu.g polyadenylated mRNA was prepared from A10 cells by the proteinase-K/SDS method (Gonda et al., Molec. Cell. Biol. 2:617-624 (1982)). Double stranded cDNA was synthesized and linkered to nonpalindromic BstX1 adaptors as described by Seed, B. and A. Aruffo, Proc. Natl. Acad. Sci. USA 84:3365-3369 (1987). Acaptored cDNA was size-fractionated on a 5 to 20% potassium acetate gradient, and inserts greater than 1 kb were ligated to the plasmid vector pcDNA-1, and electroporated in the E. coli MC1061/P3, yielding a primary library with a titer of >10.sup.7 recombinants. A portion of the cDNA was plated as pools of .about.1.times.10.sup.4 recombinant bacteria colonies grown on 15 cm petri dishes with Luria-broth agar containing 7.5 mg/ml tetracycline and 12.5 mg/ml ampicillin. Cells were scraped off the plates in 10 mls of Luria-broth, and glycerol stocks of pooled bacteria were stored at -70.degree. C. The remaining bacteria was used to purify plasmid DNA using the alkaline lysis mini-prep method (Sambrook, J. et al., Molecular Cloning: A Laboratory Manual, 2d Ed. (Cold Spring Harbor, N.Y., Cold Spring Harbor Laboratory Press (1989)).

COS Cell Transfections and Binding Assay

Plasmid pools (each representing .about.1.times.10.sup.4 clones) were transfected into COS-M6 (subclone of COS-7 cells) by the DEAE-dextran/chloroquine method described by Seed, B. and A. Aruffo, Proc. Natl. Acad. Sci. USA 84:3365-3369 (1987). Forty-eight hours after transfection, cells were incubated with 50 pM.sup.125 I-TGF-.beta.1 (100 to 200 Ci/mmol) for 4 hours at 4.degree. C.), autoradiographic analysis of transfected cells was performed using NT-B2 photographic emulsion (Kodak) essentially as described (Gearing, D. P. et al., EMBO J. 8:3667-3676 (1989)). After development of slides, cells were air-dried and mounted with mounting media and a glass coverslip. Slides were analyzed under an Olympus OM-T1 inverted phase-contrast microscope using a dissection trans-illuminator for darkfield illumination.

Subdivision of Positive Pool

Of 86 pools screened, one pool (#13) was identified as positive and a glycerol stock of bacteria corresponding to this pool was titered and 25 pools of 1000 clones were generated and miniprep plasmid from these pools were transfected into COS cells as described above. Several positive pools of 1000 were identified, and one was replated as 25 plates of 100 colonies. A replica was made of this positive plate and harvested. Once a positive pool was identified, individual colonies were picked from the corresponding master plate and grown overnight in 3 ml liquid culture. A 2-dimensional grid representing the 100 clones was generated and a single clone, R3-OF, was isolated.

Cloning of R3-OFF

A 208F rat fibroblast library in lambda ZAP II (Stratagene) was screened at high stringency with clone R3-OF insert, and several clones with .about.6 kb inserts were isolated, one of which is referred to as R3-OFF.

DNA Sequencing and Sequence Analysis

Double-stranded DNA was sequenced by the dideoxy chain termination method using Sequenase reagents (United States Biochemicals). Comparison of the sequence to the data bases was performed using BLAST (Altschcul, S. F. et al., J. Mol. Biol. 215:403-410 (1990)).

Iodination of TGF-.beta.

TGF-.beta.1 was iodinated using the chloramine-T method as described (Cheifetz, S. and J. L. Andres, J. Biol. Chem. 263:16984-16991 (1988)).

Chemical Cross-Linking

Transfected COS cells grown on 10 cm dishes or subconfluent L6 and A-10 cells grown on 3.5 cm dishes were incubated with .sup.125 I-TGF-.beta.1 in binding buffer (Frebs-Ringer buffered with 20 mM Hepes, pH 7.5, 5 mM MgSO.sub.4, 0.5% BSA), washed 4 times with ice-cold binding buffer without BSA, and incubated for 15 minutes with binding buffer without BSA containing 60 ng/ml disuccinimidyl suberate at 4.degree. C. under constant rotation. Crosslinking was terminated by addition of 7% sucrose in binding buffer. Cells were scraped, collected and pelleted by centrifugation, then resuspended in lysis buffer (10 mM Tris, pH 7.4, 1 mM EDTA, pH 8.0, 1% Triton-X 100, 10 .mu.g/ml of pepstatin, 10 .mu.g/ml leupeptin, 10 .mu.g/ml antipain, 100 .mu.g/m; benzamidine hydrochloride, 100 .mu.g/ml soybean trypsin inhibitor, 50 .mu.g/ml aprotonin, and 1 mM phenylmethylsulfonyl fluoride). Solubilized material was analyzed by 7% SDS-PAGE and subjected to autoradiographic analysis by exposure to X-AR film (Kodak) at -70.degree. C.

Enzymatic Digestion

Digestion of solubilized TGF-.beta. receptors with chondroitinase and heparitinase was performed as described (Cheifetz, S. and J. L. Andres, J. Biol. Chem. 263:16984-16991 (1988); Segarini, P. R. and S. M. Seyedin, J. Biol. Chem., 263: 8366-8370 (1988).

Generation of Stable Cell Lines

L6 myoblasts were split 1:10 into 10 cm dishes and transfected the following day by the calcium phosphate method (Chen, C. and H. Okayama, Molec. Cell. Biol. 7:2745-2752 (1987)) with clones R3-OF or R3-OFF in the forward and reverse orientations in the vector pcDNA-neo (InVitrogen). Cells were subjected to selection in the presence of G418 (Geneticin, GIBCO) for several weeks until individual colonies were visible by the naked eye. These clones were isolated and amplified.

RNA Blot Analyses

Rat tissue polyadenylated mRNA was prepared by the lithium chloride/urea method (Auffrey, C. and F. Raugeon, Eur. J. Biochemistry 107:303-313 (1980), followed by oligo-dT cellulose chromatography (Aviv and Leder, 1972). Polyadenylated mRNA from cell lines was prepared by the proteinase K/SDS method (Gonda, T. J. et al., Molec. Cell. Biol. 2:617-624 (1982)). Samples of mRNA were resolved by electrophoresis on 1% agarose-2.2M formaldehyde gels, blotted onto nylon membranes (Biotrns, ICN) and incubated with the 2.9 kb insert of clone Re-OF labeled with .sup.32 P by random priming as probe (Sambrook, J. et al., Molecular Cloning: A Laboratory Manual, 2d Ed., Cold Spring Harbor, N.Y., Cold Spring Harbor Laboratory Press, (1989). Hybridizations were performed at 42.degree. C. in hybridization buffer containing 50% formamide overnight, and blots were washed at 55.degree. C. in 0.2.times. SSC, 0.1% SDS, before exposure to X-AR film at -70.degree. C.

Production of Anti-Type III Receptor Protein Antibodies and Microsequencing and Microsequencing of Peptides Resulting from Partial Proteolysis of Purified Type III Receptor

Initially cellular proteoglycans were purified from human placenta and then subjected to enzymatic deglycosylation with heparitinase and chondroitinase. Protein cores in the molecular weight range of 100-130 kilodaltons were further purified by preparative gel electrophoresis; these should include the type III receptor. This partially purified material was used as an immunogen in mice. After screening 850 hybridoma lines developed from immunized mice, three lines were found to produce antibodies that specifically recognized and immunoprecipitated a deglycosylated polypeptide species of 100-120 kD. This species could be radiolabelled by incubation of whole cells with .sup.125 I-TGF-.beta. followed by covalent cross-linking. Its size is consistent with that of the protein core previously reported for the type III receptor. (Massague, J., Annu. Rev. Cell. Biol. 6:597-641 (1990)).

Monoclonal antibody 94 was used to purify the type III receptor from rat liver by affinity-chromatography. The purified receptor was subjected to partial proteolysis and the resulting peptides were resolved by high pressure liquid chromatography. Several peptides were subjected to microsequencing and yielded the following oligopeptide sequences: - Peptide II:  QAPFPINFMIA (SEQ ID NO:2) - Peptide III: QPIVPSVQ (SEQ ID NO:3) - Peptide IV:  FYVEQGYGR (SEQ ID NO:4)

These peptide sequences were used to construct degenerate oligonucleotides that served either as primers in a cloning strategy using the polymerase chain reaction (PCR) or as probes in screening cDNA libraries. While this strategy was not productive, the oligopeptide sequences proved useful in verifying the receptor clones isolated by the second, alternative strategy (see Example 2).

Expression Cloning of the Type III Receptor cDNA

An expression cloning strategy in COS cells, a procedure which takes advantage of the considerable amplification of individual cDNAs in transfected COS cells was used as an alternative means to isolate TGF-.beta. receptor clones. Such amplification is mediated by SV40 large T antigen expressed by the COS cells interacting with a SV40 origin of replication in the cDNA vector. Gearing, D. et al., EMBO J. 8:3667-3676 (1989); Lin, H. Y., et al., Proc. Natl. Acad. Sci. 88:3185-3189 (1991a); Lin, H. Y. et al., Science, in press (1991); Mathews, L. S. and Vale, W. W., Cell 65:973-982 (1991).

The strategy involved the construction of a cDNA library from A-10 cells, a rat vascular smooth muscle cell line that expresses all three high-affinity TGF-.beta. receptors. The resulting cDNAs were inserted into the vector pcDNA-1, which carries the CMV transcriptional promoter and the SV40 origin of replication. The resulting library was then divided into pools of 10,000 independent recombinants each and DNA from each pool was transfected into 1.5.times.10.sup.6 COS-7 cells grown on glass flaskettes by means of DEAE-dextran transfection procedure. Aruffo, A. and Seed, B., Proc. Natl. Acad. Sci. U.S.A. 84:8573-8577 (1987); Gearing, D. et al., EMBO J. 8:3667-3676 (1989); Mathews, L. S. and Vale, W. W., Cell 65:973-982 (1991). The transfected cells were cultured for 48-60 hours and then exposed to radiolabelled TGF-.beta.1 for four hours. Following this treatment, the glass slides carrying these cells were washed extensively and fixed. These slides were dipped in liquid photographic emulsion and examined by darkfield microscopy. While all of the receptor genes cloned to date by this procedure have undetectable or low constitutive levels of expression in COS cells, we were hindered by the fact that untransfected COS cells already express substantial amounts of type III TGF-.beta. receptor. Such expression, estimated to be approximately 2.times.10.sup.5 receptor molecules per cell, might well have generated an unacceptably high level of background binding. However, since the detection procedure involves visualizing radiolabelled ligand-binding on individual cells, it was hoped that identifying occasional cells expressing substantially higher levels of vector-encoded receptor would be possible. This hope was vindicated in the initial experiments.

After screening nearly one million cDNA clones in this manner, a glass slide containing 20 positive transfectants was identified. The original pool of expression constructs from which one such transfectant was derived was split into 25 subpools of 1000 clones each and these were subjected to a second round of screening. Two further rounds of sib-selection resulted in the isolation of a cDNA clone (R3-OF) with a 2.9 kb insert that induced high levels of TGF-.beta.-binding proteins in approximately 10% of COS cells into which it was transfected.

The specificity of this binding was validated by showing that addition of a 200-fold excess of unlabeled TGF-.beta. competitor strongly reduced binding of .sup.125 I-TGF-.beta. to transfected cells. By taking into account a transfection efficiency of 10% and the high background of endogenous receptor expression, we calculated that the level of total .sup.125 I-TGF-.beta. binding to each glass slide of cells transfected with this cDNA clone was only 2-fold above the level seen with mock transfectants (data not shown). Nonetheless, this marginal increase in ligand-binding was sufficient to identify rare transfectants amidst a large field of cells expressing this background level of receptor.

The R3-OF cDNA encoded an open reading frame of 836 amino acid residues of which the 3' most 18 were encoded by vector sequence, clearly indicating that clone R3-OF was an incomplete cDNA insert which ended prematurely at the codon specifying alanine 818 (FIG. 4). R3-OF was used as a probe to isolate a full-length cDNA from a rat 208F lambda phage library. This clone, termed R3-OFF, was 6 kb in length and encoded a protein of 853 amino acids; its sequence was co-linear with that of clone R3-OF.

Characterization of the Product of the Full Length Clone R3-OFF

Characterization of the product of the full length clone R3-OFF was undertaken in order to determine which of the three TGF-.beta. receptors it specified. To do so, COS transfectants were incubated with radioiodinated TGF-.beta., chemical crosslinker was added and the labelled receptors were resolved by polyacrylamide gel electrophoresis.

Labelling of cell surface TGF-.beta. receptors in this way resulted in the detection of three distinct species on the surface of COS cells, as documented extensively by others (Massague, J. et al., Ann. NY Acad. Sci. 593:59-72 (1990). These included the two lower molecular weight type I and II receptors (65 and 85 kD) and the higher molecular weight type III proteoglycan, which migrated as a diffuse band of 280-330 kd. Enzymatic treatment of the proteoglycan with chondroitinase and heparitinase yielded a core protein of approximately 100 kd. Binding to all three receptor types was specific, in that it was completed by 200-fold excess of unlabeled TGF-.beta.1.

Transfecting the R3-OFF cDNA caused a two-fold increase in expression of the type III receptor. When a cell lysate derived from COS cells transfected with clone R3-OFF was treated with deglycosylating enzymes, the heterogeneous 280-330 kd band was converted to a protein core which co-migrated with the type III protein core seen in untransfected A10 cells. Importantly, the recombinant protein core migrates differently from the endogenous COS cell type III protein core.

These observations were confirmed and extended in experiments using stably transfected cells expressing the R3-OFF cDNA. L6 rat skeleton muscle myoblasts normally do not express detectable type III mRNA or endogenous type III receptor (determined by radiolabelled ligand-binding assay). Such cells were transfected with the isolated cDNA in the vector pcDNA-neo. Cell clones stably expressing this clone in both the forward and reverse orientations with respect to the CMV promoter were isolated and analyzed by ligand binding assay.

Introduction of either the full length clone R3-OFF or the partial clone R3-OF in the forward orientation led to the de novo expression of the type III receptor. L6 cells transfected with the cDNA in reversed orientation did not express this protein. The apparent size of the protein core of the type III receptor in cells transfected with the R3-OF clone is smaller than that expressed by R3-OFF transfected cells, consistent with the difference in the sizes of the protein cores predicted from the respective nucleic acid sequences (FIGS. 1A-1C).

Unexpectedly the amount of radio-labelled ligand cross-linked to the type II receptor is increased by 2.5 fold in cells expressing the type III cDNA, while the amount cross-linked to the type I receptor remained unchanged. This apparent specific up-regulation of ligand-binding to the type II receptor could be detected with all of the 15 stably transfected L6 cell lines analyzed so far. This effect seems to be mediated by the truncated clone R3-OF which lacks the cytoplasmic domain as well as by the full-length clone R3-OFF.

Expression of Type III Receptor

Northern blot analysis demonstrated that the type III receptor mRNA is expressed as a single 6 kb message in several rat tissues. The level of mRNA expression in the liver was less than in other tissues, a result expected from earlier surveys of various tissues using radioiodinated TGF-.beta.1. Based on this information, it appears that the clone R3-OFF, with a .about.6 kb cDNA insert, represents a full length rat type III cDNA clone.

Cells of mouse origin (MEL and YH16) appear to express a smaller (.about.5.5 kb) message for the type III mRNA than those of pig, rat and human origin. In all of these cells, expression or absence of the type III mRNA is consistent with the expression of absence of detectable cell surface type III receptors with the notable exception of the retinoblastoma cell lines (Y79, Weri-1, Weri-24, and Weri-27). These cells have previously been shown to lack detectable surface expression of type III receptor, a result confirmed by our on unpublished work. It is striking that the type III receptor mRNA is expressed in these cells at a level comparable to that of other cells that do indeed express type III receptor proteins at readily detectable levels. At this moment, we can only conclude that TGF-.beta. receptor III expression, which is substantial in normal retinoblasts (AD12), has been down-regulated in these retinoblastoma tumor cells, perhaps through post-transcriptional mechanisms.

Sequence Analysis of the Full-Length Type III cDNA

The full-length cDNA clone (R3-OFF), described in Example 4, was subjected to sequence analysis. The full reading frame along with flanking sequences is presented in FIGS. 1A-1C. This reading frame encodes a protein of 853 amino acid residues, which is compatible with the 100 kD observed for the fully deglycosylated TGF-.beta. type III receptor.

Two segments of derived protein sequence (underlined and italicized, residues 378-388 and 427-434) precisely match those determined earlier from direct biochemical analysis of the purified receptor protein. This further secured the identity of this isolated cDNA clone as encoding the rat type III receptor.

This TGF-.beta. binding protein has an unusual structure for a cytokine receptor. Hydropathy analysis indicates a N-terminal signal sequence, followed by a long, hydrophilic N-terminal region (Kyte, J. and R. F. Doolittle, J. Mol. Biol. 157:105-132 (1982)). A 27 residue region of strong hydrophobicity (underlined, residues 786-812) toward the C-terminus represents the single putative transmembrane domain. This suggests that nearly all of the receptor is composed of an N-terminal extracellular domain that is anchored to the plasma membrane near its C-terminus. A relatively short C-terminal tail of 41 residues represents the putative cytoplasmic domain.

The clone R3-OF was also analyzed and found to be a truncated version of R3-OFF, with an identical open reading frame but whose last encoded residue is alanine 818 (FIGS. 1A-1C).

In R3-OFF there are six consensus N-linked glycosylation sites and 15 cysteines (indicated in FIGS. 1A-1C). There is at least one consensus glycosaminoglycan addition site at serine 535 (Bernfield, M. and K. C. Hooper, Ann. N.Y. Acad. Sci. in press (1991), and numerous Ser-Gly residues that are potential sites for GAG conjugation. A consensus protein kinase C site is also present at residue 817.

Only one other gene described to date, a glycoprotein expressed in high quantities by endothelial cells and termed endoglin (Gougos and Letarte, 1990), contains a related amino acid sequence. Overall, there is .about.30% identity with the type III receptor over the entire 645 amino acid residue length of endoglin. The most homologous regions between the sequences of the type III receptor and endoglin (74% identity) falls primarily in the putative transmembrane and cytoplasmic domains. Similar to the general structure of type III receptor, endoglin is a glycoprotein which contains a large hydrophilic and presumably extracellular N-terminal domain followed by a putative transmembrane domain and a short cytoplasmic tail of 47 amino acid residues. The biological role of endoglin is unclear, though it has been suggested that it may involve cell-cell recognition through interactions of an "RGD" sequence on its ectodomain with other adhesion molecules. Unlike the TGF-.beta. type III receptor, endoglin does not carry GAG groups.

Equivalents

Those skilled in the art will recognize, or be able to ascertain using not more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims. #             SEQUENCE LISTING - -  - - (1) GENERAL INFORMATION: - -    (iii) NUMBER OF SEQUENCES: 8 - -  - - (2) INFORMATION FOR SEQ ID NO:1: - -      (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 11 amino - #acids (B) TYPE: amino acid (C) STRANDEDNESS: double (D) TOPOLOGY: linear - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1: - - Ile Leu Leu Asp Pro Asp His Pro Pro Ala Le - #u 1               5   - #                10 - -  - - (2) INFORMATION FOR SEQ ID NO:2: - -      (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 11 amino - #acids (B) TYPE: amino acid (C) STRANDEDNESS: double (D) TOPOLOGY: linear - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2: - - Gln Ala Pro Phe Pro Ile Asn Phe Met Ile Al - #a 1               5   - #                10 - -  - - (2) INFORMATION FOR SEQ ID NO:3: - -      (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 8 amino - #acids (B) TYPE: amino acid (C) STRANDEDNESS: double (D) TOPOLOGY: linear - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3: - - Gln Pro Ile Val Pro Ser Val Gln 1               5 - -  - - (2) INFORMATION FOR SEQ ID NO:4: - -      (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 9 amino - #acids (B) TYPE: amino acid (C) STRANDEDNESS: double (D) TOPOLOGY: linear - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4: - - Phe Tyr Val Glu Gln Gly Tyr Gly Arg 1               5 - -  - - (2) INFORMATION FOR SEQ ID NO:5: - -      (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 3237 base - #pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: linear - -     (ii) MOLECULE TYPE: DNA (genomic) - -     (ix) FEATURE: (A) NAME/KEY: CDS (B) LOCATION: 241..2799 - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5: - - CAGGAGGTGA AAGTCCCCGG CGGTCCGGAT GGCGCAGTTG CACTGCGCTG CT - #GAGCTCGC     60 - - GGCCGCCTGC GCACACTGGG GGGACTCGCT TCGGCTAGTA ACTCCTCCAC CT - #CGCGGCGG    120 - - ACGACCGGTC CTGGACACGC TGCCTGCGAG GCAAGTTGAA CAGTGCAGAG AA - #GGATCTTA    180 - - AAGCTACACC CGACTTGCCA CGATTGCCTT CAATCTGAAG AACCAAAGGC TG - #TTGGAGAG    240 - - ATG GCA GTG ACA TCC CAC CAC ATG ATC CCG GT - #G ATG GTT GTC CTG ATG      288 Met Ala Val Thr Ser His His Met Ile Pro Va - #l Met Val Val Leu Met 1               5 - #                 10 - #                 15 - - AGC GCC TGC CTG GCC ACC GCC GGT CCA GAG CC - #C AGC ACC CGG TGT GAA 336 Ser Ala Cys Leu Ala Thr Ala Gly Pro Glu Pr - #o Ser Thr Arg Cys Glu 20     - #             25     - #             30 - - CTG TCA CCA ATC AAC GCC TCT CAC CCA GTC CA - #G GCC TTG ATG GAG AGC 384 Leu Ser Pro Ile Asn Ala Ser His Pro Val Gl - #n Ala Leu Met Glu Ser 35         - #         40         - #         45 - - TTC ACC GTT CTG TCT GGC TGT GCC AGC AGA GG - #C ACC ACC GGG CTG CCA 432 Phe Thr Val Leu Ser Gly Cys Ala Ser Arg Gl - #y Thr Thr Gly Leu Pro 50             - #     55             - #     60 - - AGG GAG GTC CAT GTC CTA AAC CTC CGA AGT AC - #A GAT CAG GGA CCA GGC 480 Arg Glu Val His Val Leu Asn Leu Arg Ser Th - #r Asp Gln Gly Pro Gly 65                 - # 70                 - # 75                 - # 80 - - CAG CGG CAG AGA GAG GTT ACC CTG CAC CTG AA - #C CCC ATT GCC TCG GTG 528 Gln Arg Gln Arg Glu Val Thr Leu His Leu As - #n Pro Ile Ala Ser Val 85 - #                 90 - #                 95 - - CAC ACT CAC CAC AAA CCT ATC GTG TTC CTG CT - #C AAC TCC CCC CAG CCC 576 His Thr His His Lys Pro Ile Val Phe Leu Le - #u Asn Ser Pro Gln Pro 100      - #           105      - #           110 - - CTG GTG TGG CAT CTG AAG ACG GAG AGA CTG GC - #C GCT GGT GTC CCC AGA 624 Leu Val Trp His Leu Lys Thr Glu Arg Leu Al - #a Ala Gly Val Pro Arg 115          - #       120          - #       125 - - CTC TTC CTG GTT TCG GAG GGT TCT GTG GTC CA - #G TTT CCA TCA GGA AAC 672 Leu Phe Leu Val Ser Glu Gly Ser Val Val Gl - #n Phe Pro Ser Gly Asn 130              - #   135              - #   140 - - TTC TCC TTG ACA GCA GAA ACA GAG GAA AGG AA - #T TTC CCT CAA GAA AAT 720 Phe Ser Leu Thr Ala Glu Thr Glu Glu Arg As - #n Phe Pro Gln Glu Asn 145                 1 - #50                 1 - #55                 1 - #60 - - GAA CAT CTC GTG CGC TGG GCC CAA AAG GAA TA - #T GGA GCA GTG ACT TCG      768 Glu His Leu Val Arg Trp Ala Gln Lys Glu Ty - #r Gly Ala Val Thr Ser 165  - #               170  - #               175 - - TTC ACT GAA CTC AAG ATA GCA AGA AAC ATC TA - #T ATT AAA GTG GGA GAA 816 Phe Thr Glu Leu Lys Ile Ala Arg Asn Ile Ty - #r Ile Lys Val Gly Glu 180      - #           185      - #           190 - - GAT CAA GTG TTT CCT CCT ACG TGT AAC ATA GG - #G AAG AAT TTC CTC TCA 864 Asp Gln Val Phe Pro Pro Thr Cys Asn Ile Gl - #y Lys Asn Phe Leu Ser 195          - #       200          - #       205 - - CTC AAT TAC CTT GCC GAG TAC CTT CAA CCC AA - #A GCC GCC GAA GGT TGT 912 Leu Asn Tyr Leu Ala Glu Tyr Leu Gln Pro Ly - #s Ala Ala Glu Gly Cys 210              - #   215              - #   220 - - GTC CTG CCC AGT CAG CCC CAT GAA AAG GAA GT - #A CAC ATC ATC GAG TTA 960 Val Leu Pro Ser Gln Pro His Glu Lys Glu Va - #l His Ile Ile Glu Leu 225                 2 - #30                 2 - #35                 2 - #40 - - ATT ACC CCC AGC TCG AAC CCT TAC AGC GCT TT - #C CAG GTG GAT ATA ATA     1008 Ile Thr Pro Ser Ser Asn Pro Tyr Ser Ala Ph - #e Gln Val Asp Ile Ile 245  - #               250  - #               255 - - GTT GAC ATA CGA CCT GCT CAA GAG GAT CCC GA - #G GTG GTC AAA AAC CTT 1056 Val Asp Ile Arg Pro Ala Gln Glu Asp Pro Gl - #u Val Val Lys Asn Leu 260      - #           265      - #           270 - - GTC CTG ATC TTG AAG TGC AAA AAG TCT GTC AA - #C TGG GTG ATC AAG TCT 1104 Val Leu Ile Leu Lys Cys Lys Lys Ser Val As - #n Trp Val Ile Lys Ser 275          - #       280          - #       285 - - TTT GAC GTC AAG GGA AAC TTG AAA GTC ATT GC - #T CCC AAC AGT ATC GGC 1152 Phe Asp Val Lys Gly Asn Leu Lys Val Ile Al - #a Pro Asn Ser Ile Gly 290              - #   295              - #   300 - - TTT GGA AAA GAG AGT GAA CGA TCC ATG ACA AT - #G ACC AAA TTG GTA AGA 1200 Phe Gly Lys Glu Ser Glu Arg Ser Met Thr Me - #t Thr Lys Leu Val Arg 305                 3 - #10                 3 - #15                 3 - #20 - - GAT GAC ATC CCT TCC ACC CAA GAG AAT CTG AT - #G AAG TGG GCA CTG GAC     1248 Asp Asp Ile Pro Ser Thr Gln Glu Asn Leu Me - #t Lys Trp Ala Leu Asp 325  - #               330  - #               335 - - AAT GGC TAC AGG CCA GTG ACG TCA TAC ACA AT - #G GCT CCC GTG GCT AAT 1296 Asn Gly Tyr Arg Pro Val Thr Ser Tyr Thr Me - #t Ala Pro Val Ala Asn 340      - #           345      - #           350 - - AGA TTT CAT CTT CGG CTT GAG AAC AAC GAG GA - #G ATG AGA GAT GAG GAA 1344 Arg Phe His Leu Arg Leu Glu Asn Asn Glu Gl - #u Met Arg Asp Glu Glu 355          - #       360          - #       365 - - GTC CAC ACC ATT CCT CCT GAG CTT CGT ATC CT - #G CTG GAC CCT GAC CAC 1392 Val His Thr Ile Pro Pro Glu Leu Arg Ile Le - #u Leu Asp Pro Asp His 370              - #   375              - #   380 - - CCG CCC GCC CTG GAC AAC CCA CTC TTC CCA GG - #A GAG GGA AGC CCA AAT 1440 Pro Pro Ala Leu Asp Asn Pro Leu Phe Pro Gl - #y Glu Gly Ser Pro Asn 385                 3 - #90                 3 - #95                 4 - #00 - - GGT GGT CTC CCC TTT CCA TTC CCG GAT ATC CC - #C AGG AGA GGC TGG AAG     1488 Gly Gly Leu Pro Phe Pro Phe Pro Asp Ile Pr - #o Arg Arg Gly Trp Lys 405  - #               410  - #               415 - - GAG GGC GAA GAT AGG ATC CCC CGG CCA AAG CA - #G CCC ATC GTT CCC AGT 1536 Glu Gly Glu Asp Arg Ile Pro Arg Pro Lys Gl - #n Pro Ile Val Pro Ser 420      - #           425      - #           430 - - GTT CAA CTG CTT CCT GAC CAC CGA GAA CCA GA - #A GAA GTG CAA GGG GGC 1584 Val Gln Leu Leu Pro Asp His Arg Glu Pro Gl - #u Glu Val Gln Gly Gly 435          - #       440          - #       445 - - GTG GAC ATC GCC CTG TCA GTC AAA TGT GAC CA - #T GAA AAG ATG GTC GTG 1632 Val Asp Ile Ala Leu Ser Val Lys Cys Asp Hi - #s Glu Lys Met Val Val 450              - #   455              - #   460 - - GCT GTA GAC AAA GAC TCT TTC CAG ACC AAT GG - #C TAC TCA GGG ATG GAG 1680 Ala Val Asp Lys Asp Ser Phe Gln Thr Asn Gl - #y Tyr Ser Gly Met Glu 465                 4 - #70                 4 - #75                 4 - #80 - - CTC ACC CTG TTG GAT CCT TCG TGT AAA GCC AA - #A ATG AAT GGT ACT CAC     1728 Leu Thr Leu Leu Asp Pro Ser Cys Lys Ala Ly - #s Met Asn Gly Thr His 485  - #               490  - #               495 - - TTT GTT CTC GAG TCT CCC CTG AAT GGC TGT GG - #T ACT CGA CAT CGG AGG 1776 Phe Val Leu Glu Ser Pro Leu Asn Gly Cys Gl - #y Thr Arg His Arg Arg 500      - #           505      - #           510 - - TCG ACC CCG GAT GGT GTG GTT TAC TAT AAC TC - #T ATT GTG GTG CAG GCT 1824 Ser Thr Pro Asp Gly Val Val Tyr Tyr Asn Se - #r Ile Val Val Gln Ala 515          - #       520          - #       525 - - CCG TCC CCT GGG GAT AGC AGT GGC TGG CCT GA - #T GGC TAT GAA GAC TTG 1872 Pro Ser Pro Gly Asp Ser Ser Gly Trp Pro As - #p Gly Tyr Glu Asp Leu 530              - #   535              - #   540 - - GAG TCA GGC GAT AAT GGA TTT CCT GGA GAC GG - #G GAT GAA GGA GAA ACT 1920 Glu Ser Gly Asp Asn Gly Phe Pro Gly Asp Gl - #y Asp Glu Gly Glu Thr 545                 5 - #50                 5 - #55                 5 - #60 - - GCC CCC CTG AGC CGA GCT GGA GTG GTG GTG TT - #T AAC TGC AGC TTG CGG     1968 Ala Pro Leu Ser Arg Ala Gly Val Val Val Ph - #e Asn Cys Ser Leu Arg 565  - #               570  - #               575 - - CAG CTG AGG AAT CCC AGT GGC TTC CAG GGC CA - #G CTC GAT GGA AAT GCT 2016 Gln Leu Arg Asn Pro Ser Gly Phe Gln Gly Gl - #n Leu Asp Gly Asn Ala 580      - #           585      - #           590 - - ACC TTC AAC ATG GAG CTG TAT AAC ACA GAC CT - #C TTT CTG GTG CCC TCC 2064 Thr Phe Asn Met Glu Leu Tyr Asn Thr Asp Le - #u Phe Leu Val Pro Ser 595          - #       600          - #       605 - - CCA GGG GTC TTC TCT GTG GCA GAG AAC GAG CA - #T GTT TAT GTT GAG GTG 2112 Pro Gly Val Phe Ser Val Ala Glu Asn Glu Hi - #s Val Tyr Val Glu Val 610              - #   615              - #   620 - - TCT GTC ACC AAG GCT GAC CAA GAT CTG GGA TT - #C GCC ATC CAA ACC TGC 2160 Ser Val Thr Lys Ala Asp Gln Asp Leu Gly Ph - #e Ala Ile Gln Thr Cys 625                 6 - #30                 6 - #35                 6 - #40 - - TTT CTC TCT CCA TAC TCC AAC CCA GAC AGA AT - #G TCT GAT TAC ACC ATC     2208 Phe Leu Ser Pro Tyr Ser Asn Pro Asp Arg Me - #t Ser Asp Tyr Thr Ile 645  - #               650  - #               655 - - ATC GAG AAC ATC TGT CCG AAA GAC GAC TCT GT - #G AAG TTC TAC AGC TCC 2256 Ile Glu Asn Ile Cys Pro Lys Asp Asp Ser Va - #l Lys Phe Tyr Ser Ser 660      - #           665      - #           670 - - AAG AGA GTG CAC TTT CCC ATC CCG CAT GCT GA - #G GTG GAC AAG AAG CGC 2304 Lys Arg Val His Phe Pro Ile Pro His Ala Gl - #u Val Asp Lys Lys Arg 675          - #       680          - #       685 - - TTC AGC TTC CTG TTC AAG TCT GTG TTC AAC AC - #C TCC CTG CTC TTC CTG 2352 Phe Ser Phe Leu Phe Lys Ser Val Phe Asn Th - #r Ser Leu Leu Phe Leu 690              - #   695              - #   700 - - CAC TGC GAG TTG ACT CTG TGC TCC AGG AAG AA - #G GGC TCC CTG AAG CTG 2400 His Cys Glu Leu Thr Leu Cys Ser Arg Lys Ly - #s Gly Ser Leu Lys Leu 705                 7 - #10                 7 - #15                 7 - #20 - - CCG AGG TGT GTG ACT CCT GAC GAC GCC TGC AC - #T TCT CTC GAT GCC ACC     2448 Pro Arg Cys Val Thr Pro Asp Asp Ala Cys Th - #r Ser Leu Asp Ala Thr 725  - #               730  - #               735 - - ATG ATC TGG ACC ATG ATG CAG AAT AAG AAG AC - #A TTC ACC AAG CCC CTG 2496 Met Ile Trp Thr Met Met Gln Asn Lys Lys Th - #r Phe Thr Lys Pro Leu 740      - #           745      - #           750 - - GCT GTG GTC CTC CAG GTA GAC TAT AAA GAA AA - #T GTT CCC AGC ACT AAG 2544 Ala Val Val Leu Gln Val Asp Tyr Lys Glu As - #n Val Pro Ser Thr Lys 755          - #       760          - #       765 - - GAT TCC AGT CCA ATT CCT CCT CCT CCT CCA CA - #G ATT TTC CAT GGC CTG 2592 Asp Ser Ser Pro Ile Pro Pro Pro Pro Pro Gl - #n Ile Phe His Gly Leu 770              - #   775              - #   780 - - GAC ACG CTC ACC GTG ATG GGC ATT GCA TTT GC - #A GCA TTT GTG ATC GGA 2640 Asp Thr Leu Thr Val Met Gly Ile Ala Phe Al - #a Ala Phe Val Ile Gly 785                 7 - #90                 7 - #95                 8 - #00 - - GCG CTC CTG ACG GGG GCC TTG TGG TAC ATC TA - #C TCC CAC ACA GGG GAG     2688 Ala Leu Leu Thr Gly Ala Leu Trp Tyr Ile Ty - #r Ser His Thr Gly Glu 805  - #               810  - #               815 - - ACA GCA CGA AGG CAG CAA GTC CCT ACC TCG CC - #G CCA GCC TCG GAG AAC 2736 Thr Ala Arg Arg Gln Gln Val Pro Thr Ser Pr - #o Pro Ala Ser Glu Asn 820      - #           825      - #           830 - - AGC AGC GCG GCC CAC AGC ATC GGC AGC ACT CA - #G AGT ACC CCC TGC TCT 2784 Ser Ser Ala Ala His Ser Ile Gly Ser Thr Gl - #n Ser Thr Pro Cys Ser 835          - #       840          - #       845 - - AGC AGC AGC ACA GCC TAGGTGGACA GACAGACGCC CGCCCACCG - #C AGCCAGGGCA 2839 Ser Ser Ser Thr Ala 850 - - GGGCCCGATG CCAGTGCTGC GTGTCCACAG TCAGAAGTCT TGATCTGGGC TC - #CCTGTAAA   2899 - - GAAAGAGTGA ATTTCAGTAT ACAGACAGCC AGTTCTACCC ACCCCTTACC AC - #GGCCCACA   2959 - - TAAATGTGAC CCTGGGCATC TGTCACACGA AAGCTAAGCT GGTGGCCTTC CC - #CACCAGCC   3019 - - CCTCGCAGGA TGGGGGTTTC AATGTGAAAC ATCTGCCAGT TTTGTTTTGT TT - #TTTTAATG   3079 - - CTGCTTTGTC CAGGTGTCCA AACATCCATC ATTTGGGGTG GTCTGTTTTA CA - #GAGTAAAG   3139 - - GAGGCGGTGA AGGGACGTCA GCTAGTGTGT AGAGCCAAGG GGAGACAGCT AG - #GATTCTCG   3199 - - CCTAGCTGAA CCAAGGTGTA AAATAGAAGA CACGCTCC      - # - #   3237 - -  - - (2) INFORMATION FOR SEQ ID NO:6: - -      (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 853 amino - #acids (B) TYPE: amino acid (D) TOPOLOGY: linear - -     (ii) MOLECULE TYPE: protein - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6: - - Met Ala Val Thr Ser His His Met Ile Pro Va - #l Met Val Val Leu Met 1               5 - #                 10 - #                 15 - - Ser Ala Cys Leu Ala Thr Ala Gly Pro Glu Pr - #o Ser Thr Arg Cys Glu 20     - #             25     - #             30 - - Leu Ser Pro Ile Asn Ala Ser His Pro Val Gl - #n Ala Leu Met Glu Ser 35         - #         40         - #         45 - - Phe Thr Val Leu Ser Gly Cys Ala Ser Arg Gl - #y Thr Thr Gly Leu Pro 50             - #     55             - #     60 - - Arg Glu Val His Val Leu Asn Leu Arg Ser Th - #r Asp Gln Gly Pro Gly 65                 - # 70                 - # 75                 - # 80 - - Gln Arg Gln Arg Glu Val Thr Leu His Leu As - #n Pro Ile Ala Ser Val 85 - #                 90 - #                 95 - - His Thr His His Lys Pro Ile Val Phe Leu Le - #u Asn Ser Pro Gln Pro 100      - #           105      - #           110 - - Leu Val Trp His Leu Lys Thr Glu Arg Leu Al - #a Ala Gly Val Pro Arg 115          - #       120          - #       125 - - Leu Phe Leu Val Ser Glu Gly Ser Val Val Gl - #n Phe Pro Ser Gly Asn 130              - #   135              - #   140 - - Phe Ser Leu Thr Ala Glu Thr Glu Glu Arg As - #n Phe Pro Gln Glu Asn 145                 1 - #50                 1 - #55                 1 - #60 - - Glu His Leu Val Arg Trp Ala Gln Lys Glu Ty - #r Gly Ala Val Thr Ser 165  - #               170  - #               175 - - Phe Thr Glu Leu Lys Ile Ala Arg Asn Ile Ty - #r Ile Lys Val Gly Glu 180      - #           185      - #           190 - - Asp Gln Val Phe Pro Pro Thr Cys Asn Ile Gl - #y Lys Asn Phe Leu Ser 195          - #       200          - #       205 - - Leu Asn Tyr Leu Ala Glu Tyr Leu Gln Pro Ly - #s Ala Ala Glu Gly Cys 210              - #   215              - #   220 - - Val Leu Pro Ser Gln Pro His Glu Lys Glu Va - #l His Ile Ile Glu Leu 225                 2 - #30                 2 - #35                 2 - #40 - - Ile Thr Pro Ser Ser Asn Pro Tyr Ser Ala Ph - #e Gln Val Asp Ile Ile 245  - #               250  - #               255 - - Val Asp Ile Arg Pro Ala Gln Glu Asp Pro Gl - #u Val Val Lys Asn Leu 260      - #           265      - #           270 - - Val Leu Ile Leu Lys Cys Lys Lys Ser Val As - #n Trp Val Ile Lys Ser 275          - #       280          - #       285 - - Phe Asp Val Lys Gly Asn Leu Lys Val Ile Al - #a Pro Asn Ser Ile Gly 290              - #   295              - #   300 - - Phe Gly Lys Glu Ser Glu Arg Ser Met Thr Me - #t Thr Lys Leu Val Arg 305                 3 - #10                 3 - #15                 3 - #20 - - Asp Asp Ile Pro Ser Thr Gln Glu Asn Leu Me - #t Lys Trp Ala Leu Asp 325  - #               330  - #               335 - - Asn Gly Tyr Arg Pro Val Thr Ser Tyr Thr Me - #t Ala Pro Val Ala Asn 340      - #           345      - #           350 - - Arg Phe His Leu Arg Leu Glu Asn Asn Glu Gl - #u Met Arg Asp Glu Glu 355          - #       360          - #       365 - - Val His Thr Ile Pro Pro Glu Leu Arg Ile Le - #u Leu Asp Pro Asp His 370              - #   375              - #   380 - - Pro Pro Ala Leu Asp Asn Pro Leu Phe Pro Gl - #y Glu Gly Ser Pro Asn 385                 3 - #90                 3 - #95                 4 - #00 - - Gly Gly Leu Pro Phe Pro Phe Pro Asp Ile Pr - #o Arg Arg Gly Trp Lys 405  - #               410  - #               415 - - Glu Gly Glu Asp Arg Ile Pro Arg Pro Lys Gl - #n Pro Ile Val Pro Ser 420      - #           425      - #           430 - - Val Gln Leu Leu Pro Asp His Arg Glu Pro Gl - #u Glu Val Gln Gly Gly 435          - #       440          - #       445 - - Val Asp Ile Ala Leu Ser Val Lys Cys Asp Hi - #s Glu Lys Met Val Val 450              - #   455              - #   460 - - Ala Val Asp Lys Asp Ser Phe Gln Thr Asn Gl - #y Tyr Ser Gly Met Glu 465                 4 - #70                 4 - #75                 4 - #80 - - Leu Thr Leu Leu Asp Pro Ser Cys Lys Ala Ly - #s Met Asn Gly Thr His 485  - #               490  - #               495 - - Phe Val Leu Glu Ser Pro Leu Asn Gly Cys Gl - #y Thr Arg His Arg Arg 500      - #           505      - #           510 - - Ser Thr Pro Asp Gly Val Val Tyr Tyr Asn Se - #r Ile Val Val Gln Ala 515          - #       520          - #       525 - - Pro Ser Pro Gly Asp Ser Ser Gly Trp Pro As - #p Gly Tyr Glu Asp Leu 530              - #   535              - #   540 - - Glu Ser Gly Asp Asn Gly Phe Pro Gly Asp Gl - #y Asp Glu Gly Glu Thr 545                 5 - #50                 5 - #55                 5 - #60 - - Ala Pro Leu Ser Arg Ala Gly Val Val Val Ph - #e Asn Cys Ser Leu Arg 565  - #               570  - #               575 - - Gln Leu Arg Asn Pro Ser Gly Phe Gln Gly Gl - #n Leu Asp Gly Asn Ala 580      - #           585      - #           590 - - Thr Phe Asn Met Glu Leu Tyr Asn Thr Asp Le - #u Phe Leu Val Pro Ser 595          - #       600          - #       605 - - Pro Gly Val Phe Ser Val Ala Glu Asn Glu Hi - #s Val Tyr Val Glu Val 610              - #   615              - #   620 - - Ser Val Thr Lys Ala Asp Gln Asp Leu Gly Ph - #e Ala Ile Gln Thr Cys 625                 6 - #30                 6 - #35                 6 - #40 - - Phe Leu Ser Pro Tyr Ser Asn Pro Asp Arg Me - #t Ser Asp Tyr Thr Ile 645  - #               650  - #               655 - - Ile Glu Asn Ile Cys Pro Lys Asp Asp Ser Va - #l Lys Phe Tyr Ser Ser 660      - #           665      - #           670 - - Lys Arg Val His Phe Pro Ile Pro His Ala Gl - #u Val Asp Lys Lys Arg 675          - #       680          - #       685 - - Phe Ser Phe Leu Phe Lys Ser Val Phe Asn Th - #r Ser Leu Leu Phe Leu 690              - #   695              - #   700 - - His Cys Glu Leu Thr Leu Cys Ser Arg Lys Ly - #s Gly Ser Leu Lys Leu 705                 7 - #10                 7 - #15                 7 - #20 - - Pro Arg Cys Val Thr Pro Asp Asp Ala Cys Th - #r Ser Leu Asp Ala Thr 725  - #               730  - #               735 - - Met Ile Trp Thr Met Met Gln Asn Lys Lys Th - #r Phe Thr Lys Pro Leu 740      - #           745      - #           750 - - Ala Val Val Leu Gln Val Asp Tyr Lys Glu As - #n Val Pro Ser Thr Lys 755          - #       760          - #       765 - - Asp Ser Ser Pro Ile Pro Pro Pro Pro Pro Gl - #n Ile Phe His Gly Leu 770              - #   775              - #   780 - - Asp Thr Leu Thr Val Met Gly Ile Ala Phe Al - #a Ala Phe Val Ile Gly 785                 7 - #90                 7 - #95                 8 - #00 - - Ala Leu Leu Thr Gly Ala Leu Trp Tyr Ile Ty - #r Ser His Thr Gly Glu 805  - #               810  - #               815 - - Thr Ala Arg Arg Gln Gln Val Pro Thr Ser Pr - #o Pro Ala Ser Glu Asn 820      - #           825      - #           830 - - Ser Ser Ala Ala His Ser Ile Gly Ser Thr Gl - #n Ser Thr Pro Cys Ser 835          - #       840          - #       845 - - Ser Ser Ser Thr Ala 850 - -  - - (2) INFORMATION FOR SEQ ID NO:7: - -      (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 2090 base - #pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: linear - -     (ii) MOLECULE TYPE: DNA (genomic) - -     (ix) FEATURE: (A) NAME/KEY: CDS (B) LOCATION: 336..2038 - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7: - - GTTGGCGAGG AGTTTCCTGT TTCCCCCGCA GCGCTGAGTT GAAGTTGAGT GA - #GTCACTCG     60 - - CGCGCACGGA GCGACGACAC CCCCGCGCGT GCACCCGCTC GGGACAGGAG CC - #GGACTCCT    120 - - GTGCAGCTTC CCTCGGCCGC CGGGGGCCTC CCCGCGCCTC GCCGGCCTCC AG - #GCCCCTCC    180 - - TGGCTGGCGA GCGGGCGCCA CATCTGGCCC GCACATCTGC GCTGCCGGCC CG - #GCGCGGGG    240 - - TCCGGAGAGG GCGCGGCGCG GAGCGCAGCC AGGGGTCCGG GAAGGCGCCG TC - #CGTGCGCT    300 - - GGGGGCTCGG TCTATGACGA GCAGCGGGGT CTGCC ATG GGT CGG - #GGG CTG CTC 353 - #                  - #   Met Gly Arg Gly Leu Leu - #                  - #     1             - #  5 - - AGG GGC CTG TGG CCG CTG CAC ATC GTC CTG TG - #G ACG CGT ATC GCC AGC 401 Arg Gly Leu Trp Pro Leu His Ile Val Leu Tr - #p Thr Arg Ile Ala Ser 10     - #             15     - #             20 - - ACG ATC CCA CCG CAC GTT CAG AAG TCG GTT AA - #T AAC GAC ATG ATA GTC 449 Thr Ile Pro Pro His Val Gln Lys Ser Val As - #n Asn Asp Met Ile Val 25         - #         30         - #         35 - - ACT GAC AAC AAC GGT GCA GTC AAG TTT CCA CA - #A CTG TGT AAA TTT TGT 497 Thr Asp Asn Asn Gly Ala Val Lys Phe Pro Gl - #n Leu Cys Lys Phe Cys 40             - #     45             - #     50 - - GAT GTG AGA TTT TCC ACC TGT GAC AAC CAG AA - #A TCC TGC ATG AGC AAC 545 Asp Val Arg Phe Ser Thr Cys Asp Asn Gln Ly - #s Ser Cys Met Ser Asn 55                 - # 60                 - # 65                 - # 70 - - TGC AGC ATC ACC TCC ATC TGT GAG AAG CCA CA - #G GAA GTC TGT GTG GCT 593 Cys Ser Ile Thr Ser Ile Cys Glu Lys Pro Gl - #n Glu Val Cys Val Ala 75 - #                 80 - #                 85 - - GTA TGG AGA AAG AAT GAC GAG AAC ATA ACA CT - #A GAG ACA GTT TGC CAT 641 Val Trp Arg Lys Asn Asp Glu Asn Ile Thr Le - #u Glu Thr Val Cys His 90     - #             95     - #            100 - - GAC CCC AAG CTC CCC TAC CAT GAC TTT ATT CT - #G GAA GAT GCT GCT TCT 689 Asp Pro Lys Leu Pro Tyr His Asp Phe Ile Le - #u Glu Asp Ala Ala Ser 105          - #       110          - #       115 - - CCA AAG TGC ATT ATG AAG GAA AAA AAA AAG CC - #T GGT GAG ACT TTC TTC 737 Pro Lys Cys Ile Met Lys Glu Lys Lys Lys Pr - #o Gly Glu Thr Phe Phe 120              - #   125              - #   130 - - ATG TGT TCC TGT AGC TCT GAT GAG TGC AAT GA - #C AAC ATC ATC TTC TCA 785 Met Cys Ser Cys Ser Ser Asp Glu Cys Asn As - #p Asn Ile Ile Phe Ser 135                 1 - #40                 1 - #45                 1 - #50 - - GAA GAA TAT AAC ACC AGC AAT CCT GAC TTG TT - #G CTA GTC ATA TTT CAA      833 Glu Glu Tyr Asn Thr Ser Asn Pro Asp Leu Le - #u Leu Val Ile Phe Gln 155  - #               160  - #               165 - - GTG ACA GGC ATC AGC CTC CTG CCA CCA CTG GG - #A GTT GCC ATA TCT GTC 881 Val Thr Gly Ile Ser Leu Leu Pro Pro Leu Gl - #y Val Ala Ile Ser Val 170      - #           175      - #           180 - - ATC ATC ATC TTC TAC TGC TAC CGC GTT AAC CG - #G CAG CAG AAG CTG AGT 929 Ile Ile Ile Phe Tyr Cys Tyr Arg Val Asn Ar - #g Gln Gln Lys Leu Ser 185          - #       190          - #       195 - - TCA ACC TGG GAA ACC GGC AAG ACG CGG AAG CT - #C ATG GAG TTC AGC GAG 977 Ser Thr Trp Glu Thr Gly Lys Thr Arg Lys Le - #u Met Glu Phe Ser Glu 200              - #   205              - #   210 - - CAC TGT GCC ATC ATC CTG GAA GAT GAC CGC TC - #T GAC ATC AGC TCC ACG 1025 His Cys Ala Ile Ile Leu Glu Asp Asp Arg Se - #r Asp Ile Ser Ser Thr 215                 2 - #20                 2 - #25                 2 - #30 - - TGT GCC AAC AAC ATC AAC CAC AAC ACA GAG CT - #G CTG CCC ATT GAG CTG     1073 Cys Ala Asn Asn Ile Asn His Asn Thr Glu Le - #u Leu Pro Ile Glu Leu 235  - #               240  - #               245 - - GAC ACC CTG GTG GGG AAA GGT CGC TTT GCT GA - #G GTC TAT AAG GCC AAG 1121 Asp Thr Leu Val Gly Lys Gly Arg Phe Ala Gl - #u Val Tyr Lys Ala Lys 250      - #           255      - #           260 - - CTG AAG CAG AAC ACT TCA GAG CAG TTT GAG AC - #A GTG GCA GTC AAG ATC 1169 Leu Lys Gln Asn Thr Ser Glu Gln Phe Glu Th - #r Val Ala Val Lys Ile 265          - #       270          - #       275 - - TTT CCC TAT GAG GAG TAT GCC TCT TGG AAG AC - #A GAG AAG GAC ATC TTC 1217 Phe Pro Tyr Glu Glu Tyr Ala Ser Trp Lys Th - #r Glu Lys Asp Ile Phe 280              - #   285              - #   290 - - TCA GAC ATC AAT CTG AAG CAT GAG AAC ATA CT - #C CAG TTC CTG ACG GCT 1265 Ser Asp Ile Asn Leu Lys His Glu Asn Ile Le - #u Gln Phe Leu Thr Ala 295                 3 - #00                 3 - #05                 3 - #10 - - GAG GAG CGG AAG ACG GAG TTG GGG AAA CAA TA - #C TGG CTG ATC ACC GCC     1313 Glu Glu Arg Lys Thr Glu Leu Gly Lys Gln Ty - #r Trp Leu Ile Thr Ala 315  - #               320  - #               325 - - TTC CAC GCC AAG GGC AAC CTA CAG GAG TAC CT - #G ACG CGG CAT GTC ATC 1361 Phe His Ala Lys Gly Asn Leu Gln Glu Tyr Le - #u Thr Arg His Val Ile 330      - #           335      - #           340 - - AGC TGG GAG GAC CTG CGC AAG CTG GGC AGC TC - #C CTC GCC CGG GGG ATT 1409 Ser Trp Glu Asp Leu Arg Lys Leu Gly Ser Se - #r Leu Ala Arg Gly Ile 345          - #       350          - #       355 - - GCT CAC CTC CAC AGT GAT CAC ACT CCA TGT GG - #G AGG CCC AAG ATG CCC 1457 Ala His Leu His Ser Asp His Thr Pro Cys Gl - #y Arg Pro Lys Met Pro 360              - #   365              - #   370 - - ATC GTG CAC AGG GAC CTC AAG AGC TCC AAT AT - #C CTC GTG AAG AAC GAC 1505 Ile Val His Arg Asp Leu Lys Ser Ser Asn Il - #e Leu Val Lys Asn Asp 375                 3 - #80                 3 - #85                 3 - #90 - - CTA ACC TGC TGC CTG TGT GAC TTT GGG CTT TC - #C CTG CGT CTG GAC CCT     1553 Leu Thr Cys Cys Leu Cys Asp Phe Gly Leu Se - #r Leu Arg Leu Asp Pro 395  - #               400  - #               405 - - ACT CTG TCT GTG GAT GAC CTG GCT AAC AGT GG - #G CAG GTG GGA ACT GCA 1601 Thr Leu Ser Val Asp Asp Leu Ala Asn Ser Gl - #y Gln Val Gly Thr Ala 410      - #           415      - #           420 - - AGA TAC ATG GCT CCA GAA GTC CTA GAA TCC AG - #G ATG AAT TTG GAG AAT 1649 Arg Tyr Met Ala Pro Glu Val Leu Glu Ser Ar - #g Met Asn Leu Glu Asn 425          - #       430          - #       435 - - GCT GAG TCC TTC AAG CAG ACC GAT GTC TAC TC - #C ATG GCT CTG GTG CTC 1697 Ala Glu Ser Phe Lys Gln Thr Asp Val Tyr Se - #r Met Ala Leu Val Leu 440              - #   445              - #   450 - - TGG GAA ATG ACA TCT CGC TGT AAT GCA GTG GG - #A GAA GTA AAA GAT TAT 1745 Trp Glu Met Thr Ser Arg Cys Asn Ala Val Gl - #y Glu Val Lys Asp Tyr 455                 4 - #60                 4 - #65                 4 - #70 - - GAG CCT CCA TTT GGT TCC AAG GTG CGG GAG CA - #C CCC TGT GTC GAA AGC     1793 Glu Pro Pro Phe Gly Ser Lys Val Arg Glu Hi - #s Pro Cys Val Glu Ser 475  - #               480  - #               485 - - ATG AAG GAC AAC GTG TTG AGA GAT CGA GGG CG - #A CCA GAA ATT CCC AGC 1841 Met Lys Asp Asn Val Leu Arg Asp Arg Gly Ar - #g Pro Glu Ile Pro Ser 490      - #           495      - #           500 - - TTC TGG CTC AAC CAC CAG GGC ATC CAG ATG GT - #G TGT GAG ACG TTG ACT 1889 Phe Trp Leu Asn His Gln Gly Ile Gln Met Va - #l Cys Glu Thr Leu Thr 505          - #       510          - #       515 - - GAG TGC TGG GAC CAC GAC CCA GAG GCC CGT CT - #C ACA GCC CAG TGT GTG 1937 Glu Cys Trp Asp His Asp Pro Glu Ala Arg Le - #u Thr Ala Gln Cys Val 520              - #   525              - #   530 - - GCA GAA CGC TTC AGT GAG CTG GAG CAT CTG GA - #C AGG CTC TCG GGG AGG 1985 Ala Glu Arg Phe Ser Glu Leu Glu His Leu As - #p Arg Leu Ser Gly Arg 535                 5 - #40                 5 - #45                 5 - #50 - - AGC TGC TCG GAG GAG AAG ATT CCT GAA GAC GG - #C TCC CTA AAC ACT ACC     2033 Ser Cys Ser Glu Glu Lys Ile Pro Glu Asp Gl - #y Ser Leu Asn Thr Thr 555  - #               560  - #               565 - - AAA TA GCTCTTATGG GGCAGGCTGG GCATGTCCAA AGAGGCTGCC CCT - #CTCACCA 2088 Lys - - AA                  - #                  - #                  - # 2090 - -  - - (2) INFORMATION FOR SEQ ID NO:8: - -      (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 567 amino - #acids (B) TYPE: amino acid (D) TOPOLOGY: linear - -     (ii) MOLECULE TYPE: protein - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8: - - Met Gly Arg Gly Leu Leu Arg Gly Leu Trp Pr - #o Leu His Ile Val Leu 1               5 - #                 10 - #                 15 - - Trp Thr Arg Ile Ala Ser Thr Ile Pro Pro Hi - #s Val Gln Lys Ser Val 20     - #             25     - #             30 - - Asn Asn Asp Met Ile Val Thr Asp Asn Asn Gl - #y Ala Val Lys Phe Pro 35         - #         40         - #         45 - - Gln Leu Cys Lys Phe Cys Asp Val Arg Phe Se - #r Thr Cys Asp Asn Gln 50             - #     55             - #     60 - - Lys Ser Cys Met Ser Asn Cys Ser Ile Thr Se - #r Ile Cys Glu Lys Pro 65                 - # 70                 - # 75                 - # 80 - - Gln Glu Val Cys Val Ala Val Trp Arg Lys As - #n Asp Glu Asn Ile Thr 85 - #                 90 - #                 95 - - Leu Glu Thr Val Cys His Asp Pro Lys Leu Pr - #o Tyr His Asp Phe Ile 100      - #           105      - #           110 - - Leu Glu Asp Ala Ala Ser Pro Lys Cys Ile Me - #t Lys Glu Lys Lys Lys 115          - #       120          - #       125 - - Pro Gly Glu Thr Phe Phe Met Cys Ser Cys Se - #r Ser Asp Glu Cys Asn 130              - #   135              - #   140 - - Asp Asn Ile Ile Phe Ser Glu Glu Tyr Asn Th - #r Ser Asn Pro Asp Leu 145                 1 - #50                 1 - #55                 1 - #60 - - Leu Leu Val Ile Phe Gln Val Thr Gly Ile Se - #r Leu Leu Pro Pro Leu 165  - #               170  - #               175 - - Gly Val Ala Ile Ser Val Ile Ile Ile Phe Ty - #r Cys Tyr Arg Val Asn 180      - #           185      - #           190 - - Arg Gln Gln Lys Leu Ser Ser Thr Trp Glu Th - #r Gly Lys Thr Arg Lys 195          - #       200          - #       205 - - Leu Met Glu Phe Ser Glu His Cys Ala Ile Il - #e Leu Glu Asp Asp Arg 210              - #   215              - #   220 - - Ser Asp Ile Ser Ser Thr Cys Ala Asn Asn Il - #e Asn His Asn Thr Glu 225                 2 - #30                 2 - #35                 2 - #40 - - Leu Leu Pro Ile Glu Leu Asp Thr Leu Val Gl - #y Lys Gly Arg Phe Ala 245  - #               250  - #               255 - - Glu Val Tyr Lys Ala Lys Leu Lys Gln Asn Th - #r Ser Glu Gln Phe Glu 260      - #           265      - #           270 - - Thr Val Ala Val Lys Ile Phe Pro Tyr Glu Gl - #u Tyr Ala Ser Trp Lys 275          - #       280          - #       285 - - Thr Glu Lys Asp Ile Phe Ser Asp Ile Asn Le - #u Lys His Glu Asn Ile 290              - #   295              - #   300 - - Leu Gln Phe Leu Thr Ala Glu Glu Arg Lys Th - #r Glu Leu Gly Lys Gln 305                 3 - #10                 3 - #15                 3 - #20 - - Tyr Trp Leu Ile Thr Ala Phe His Ala Lys Gl - #y Asn Leu Gln Glu Tyr 325  - #               330  - #               335 - - Leu Thr Arg His Val Ile Ser Trp Glu Asp Le - #u Arg Lys Leu Gly Ser 340      - #           345      - #           350 - - Ser Leu Ala Arg Gly Ile Ala His Leu His Se - #r Asp His Thr Pro Cys 355          - #       360          - #       365 - - Gly Arg Pro Lys Met Pro Ile Val His Arg As - #p Leu Lys Ser Ser Asn 370              - #   375              - #   380 - - Ile Leu Val Lys Asn Asp Leu Thr Cys Cys Le - #u Cys Asp Phe Gly Leu 385                 3 - #90                 3 - #95                 4 - #00 - - Ser Leu Arg Leu Asp Pro Thr Leu Ser Val As - #p Asp Leu Ala Asn Ser 405  - #               410  - #               415 - - Gly Gln Val Gly Thr Ala Arg Tyr Met Ala Pr - #o Glu Val Leu Glu Ser 420      - #           425      - #           430 - - Arg Met Asn Leu Glu Asn Ala Glu Ser Phe Ly - #s Gln Thr Asp Val Tyr 435          - #       440          - #       445 - - Ser Met Ala Leu Val Leu Trp Glu Met Thr Se - #r Arg Cys Asn Ala Val 450              - #   455              - #   460 - - Gly Glu Val Lys Asp Tyr Glu Pro Pro Phe Gl - #y Ser Lys Val Arg Glu 465                 4 - #70                 4 - #75                 4 - #80 - - His Pro Cys Val Glu Ser Met Lys Asp Asn Va - #l Leu Arg Asp Arg Gly 485  - #               490  - #               495 - - Arg Pro Glu Ile Pro Ser Phe Trp Leu Asn Hi - #s Gln Gly Ile Gln Met 500      - #           505      - #           510 - - Val Cys Glu Thr Leu Thr Glu Cys Trp Asp Hi - #s Asp Pro Glu Ala Arg 515          - #       520          - #       525 - - Leu Thr Ala Gln Cys Val Ala Glu Arg Phe Se - #r Glu Leu Glu His Leu 530              - #   535              - #   540 - - Asp Arg Leu Ser Gly Arg Ser Cys Ser Glu Gl - #u Lys Ile Pro Glu Asp 545                 5 - #50                 5 - #55                 5 - #60 - - Gly Ser Leu Asn Thr Thr Lys 565 __________________________________________________________________________

## Claims

1. An isolated nucleic acid molecule comprising a nucleotide sequence encoding a mammalian TGF-.beta. type II receptor, wherein the sequence is selected from the group consisting of: deposited under ATCC accession number 209455, wherein the DNA molecule hybridizes with a probe having the sequence of the complement of the coding sequence of the cDNA insert contained in the plasmid deposited under ATCC accession number 209455 under stringency conditions sufficient to specifically identify the cDNA molecule in the library, and

2. An isolated nucleic acid molecule according to claim 1, having the nucleotide sequence of a cDNA molecule present in a human cDNA library.

3. A nucleic acid molecule according to claim 1, wherein the molecule is DNA which hybridizes under high stringency conditions to the complement of the coding sequence of the cDNA insert contained in the plasmid deposited under ATCC accession number 209455.

4. An isolated nucleic acid molecule having a nucleotide sequence which comprises a contiguous fragment of the sequence of a molecule according to claim 1, wherein the fragment is isolated from its native chromosomal context and encodes a soluble TGF-.beta. type II receptor polypeptide capable of specifically binding to TGF-.beta..

5. A nucleic acid molecule comprising the nucleotide sequence of the cDNA insert contained in the plasmid deposited under ATCC accession number 209455.

6. Plasmid 3FF (ATCC 209455).

7. An isolated nucleic acid molecule comprising a nucleotide sequence encoding a mammalian TGF-.beta. type II receptor, wherein the nucleotide sequence is isolated from its native chromosomal context, and wherein the sequence is selected from the group consisting of: wherein the DNA molecule hybridizes with a probe having the sequence of the complement of the coding sequence set forth in SEQ ID NO: 7 under stringency conditions sufficient to specifically identify the DNA molecule in the library, and

8. A nucleic acid molecule according to claim 7, wherein the molecule is DNA which hybridizes under high stringency conditions to the complement of the coding sequence set forth in SEQ ID NO: 7.

9. An isolated nucleic acid molecule having a nucleotide sequence which comprises a contiguous fragment of a TGF-.beta. type II receptor-encoding sequence according to claim 7, wherein the fragment is isolated from its native chromosomal context, and encodes a soluble receptor polypeptide capable of specifically binding to TGF-.beta..

10. An isolated nucleic acid molecule encoding the amino acid sequence of a human TGF-.beta. type II receptor as set forth in SEQ ID NO: 8, wherein the nucleotide sequence of the molecule is isolated from its native chromosomal context.

11. An isolated nucleic acid molecule having a nucleotide sequence which comprises a contiguous fragment of the sequence of a molecule according to claim 10, wherein the fragment is isolated from its native chromosomal context, and encodes a soluble TGF-.beta. type II receptor polypeptide capable of specifically binding to TGF-.beta..

12. A nucleic acid molecule comprising the nucleotide sequence set forth in SEQ ID NO: 7.

13. A vector comprising the sequence of a nucleic acid molecule according to any one of claims 1-5 or -12.

14. A cultured host cell comprising a vector according to claim 13.

15. A host cell according to claim 14, wherein the cell is a COS cell or an L6 myoblast.

16. A process for modifying a cultured host cell, comprising the step of introducing a composition consisting essentially of a nucleic acid molecule according to any one of claims 1-13 into said cell.

17. A modified host cell prepared according to the process of claim 16.

18. A method of producing a TGF-.beta.-binding polypeptide, comprising the step of culturing the host cell of claim 14 under conditions suitable to effect the expression of said nucleic acid.

19. A method of producing a TGF-.beta.-binding polypeptide, comprising the step of culturing the modified host cell of claim 17 under conditions suitable to effect the expression of said nucleic acid.

20. A host cell according to claim 14, wherein the cell expresses a heterologous mammalian TGF-.beta. type II receptor.

21. A host cell according to claim 15, wherein the cell expresses a heterologous mammalian TGF-.beta. type II receptor.

22. A host cell according to claim 17, wherein the cell expresses a heterologous mammalian TGF-.beta. type II receptor.

23. An isolated nucleic acid molecule comprising a sequence selected from the group consisting of: and fragment according to (a); wherein the fragment is isolated from its native chromosomal context, and wherein a probe having the sequence of a fragment according to (a) hybridizes under conditions of high stringency to the complement of the sequence set forth in SEQ ID NO: 7.

24. An isolated nucleic acid molecule comprising a sequence selected from the group consisting of: ATCC accession number 209455, and fragment according to (a); wherein the fragment is isolated from its native chromosomal context, and wherein a probe having the sequence of a fragment according to (a) hybridizes under conditions of high stringency to the complementary strand of the cDNA insert in the plasmid deposited under ATCC accession number 209455.