bluuebunny/crossref_metadata_2025 huggingface dataset:
Serca1 Truncated Proteins Unable to Pump Calcium Reduce the Endoplasmic Reticulum Calcium Concentration and Induce Apoptosis
Authors: Chami Mounia , Gozuacik Devrim , Lagorce David , Brini Marisa , Falson Pierre , Peaucellier Gérard , Pinton Paolo , Lecoeur Hervé , Gougeon Marie-Lyse , le Maire Marc , Rizzuto Rosario , Bréchot Christian , Paterlini-Bréchot Patrizia
Published: July 2002

By pumping calcium from the cytosol to the ER, sarco/endoplasmic reticulum calcium ATPases (SERCAs) play a major role in the control of calcium signaling. We describe two SERCA1 splice variants (S1Ts) characterized by exon 4 and/or exon 11 splicing, encoding COOH terminally truncated proteins, having only one of the seven calcium-binding residues, and thus unable to pump calcium. As shown by semiquantitative RT-PCR, S1T transcripts are differentially expressed in several adult and fetal human tissues, but not in skeletal muscle and heart. S1T proteins expression was detected by Western blot in nontransfected cell lines. In transiently transfected cells, S1T homodimers were revealed by Western blot using mildly denaturing conditions. S1T proteins were shown, by confocal scanning microscopy, to colocalize with endogenous SERCA2b into the ER membrane. Using ER-targeted aequorin (erAEQ), we have found that S1T proteins reduce ER calcium and reverse elevation of ER calcium loading induced by SERCA1 and SERCA2b. Our results also show that SERCA1 variants increase ER calcium leakage and are consistent with the hypothesis of a cation channel formed by S1T homodimers. Finally, when overexpressed in liver-derived cells, S1T proteins significantly induce apoptosis. These data reveal a further mechanism modulating Ca2+ accumulation into the ER of nonmuscle cells and highlight the relevance of S1T proteins to the control of apoptosis.
Sec6/8 complexes on trans-Golgi network and plasma membrane regulate late stages of exocytosis in mammalian cells
Authors: Yeaman Charles , Grindstaff Kent K. , Wright Jessica R. , Nelson W. James
Published: July 2002

Sec6/8 complex regulates delivery of exocytic vesicles to plasma membrane docking sites, but how it is recruited to specific sites in the exocytic pathway is poorly understood. We identified an Sec6/8 complex on trans-Golgi network (TGN) and plasma membrane in normal rat kidney (NRK) cells that formed either fibroblast- (NRK-49F) or epithelial-like (NRK-52E) intercellular junctions. At both TGN and plasma membrane, Sec6/8 complex colocalizes with exocytic cargo protein, vesicular stomatitis virus G protein (VSVG)-tsO45. Newly synthesized Sec6/8 complex is simultaneously recruited from the cytosol to both sites. However, brefeldin A treatment inhibits recruitment to the plasma membrane and other treatments that block exocytosis (e.g., expression of kinase-inactive protein kinase D and low temperature incubation) cause accumulation of Sec6/8 on the TGN, indicating that steady-state distribution of Sec6/8 complex depends on continuous exocytic vesicle trafficking. Addition of antibodies specific for TGN- or plasma membrane–bound Sec6/8 complexes to semiintact NRK cells results in cargo accumulation in a perinuclear region or near the plasma membrane, respectively. These results indicate that Sec6/8 complex is required for several steps in exocytic transport of vesicles between TGN and plasma membrane.
Costimulation of T Cell Activation by Integrin-associated Protein (CD47) Is an Adhesion-dependent, CD28-independent Signaling Pathway
Authors: Reinhold Martina I. , Lindberg Frederik P. , Kersh Gilbert J. , Allen Paul M. , Brown Eric J.
Published: July 2002

The integrin-associated protein (IAP, CD47) is a 50-kD plasma membrane protein with a single extracellular immunoglobulin variable (IgV)-like domain, a multiply membrane-spanning segment, and alternatively spliced short cytoplasmic tails. On neutrophils, IAP has been shown to function in a signaling complex with β3 integrins. However, the function of IAP on T cells, which express little or no β3 integrin, is not yet defined. Here, we show that mAbs recognizing IAP can enhance proliferation of primary human T cells in the presence of low levels of antiCD3, but have no effect on T cell proliferation on their own. Together with suboptimal concentrations of anti-CD3, engagement of IAP also enhances IL-2 production in Jurkat cells, an apparently integrin-independent function of IAP. Nonetheless, costimulation by IAP ligation requires cell adhesion. IAP costimulation does not require CD28. Furthermore, anti-IAP, but not anti-CD28, synergizes with suboptimal anti-CD3 to enhance tyrosine phosphorylation of the CD3 ζ chain and the T cell–specific tyrosine kinase Zap70. Ligation of human IAP transfected into the hemoglobin-specific 3.L2 murine T cell hybridoma costimulates activation for IL-2 secretion both with anti-CD3 and with antigenic peptides on antigen-presenting cells (APCs). Moreover, ligation of IAP but not CD28 can convert antagonist peptides into agonists in 3.L2 cells. Using costimulation by IAP ligation as an assay to analyze the structure–function relationships in IAP signaling, we find that both the extracellular and multiply membrane-spanning domains of IAP are necessary for synergy with the antigen receptor, but the alternatively spliced cytoplasmic tails are not. These data demonstrate that IAP ligation initiates an adhesiondependent costimulatory pathway distinct from CD28. We hypothesize that anti-IAP generates the costimulatory signal because it modulates interactions of the IgV domain with other plasma membrane molecules; this in turn activates effector functions of the multiply membrane-spanning domain of IAP. This model may have general significance for how IAP functions in cell activation.
Mutants in the ADP-ribosyltransferase Cleft of Cholera Toxin Lack Diarrheagenicity but Retain Adjuvanticity
Authors: Yamamoto Shingo , Takeda Yoshifumi , Yamamoto Masafumi , Kurazono Hisao , Imaoka Koichi , Yamamoto Miho , Fujihashi Kohtaro , Noda Masatoshi , Kiyono Hiroshi , McGhee Jerry R.
Published: July 2002

Cholera toxin (CT), the most commonly used mucosal adjuvant in experimental animals, is unsuitable for humans because of potent diarrhea-inducing properties. We have constructed two CT-A subunit mutants, e.g., serine→ phenylalanine at position 61 (S61F), and glutamic acid→ lysine at 112 (E112K) by site-directed mutagenesis. Neither mutant CT (mCT), in contrast to native CT (nCT), induced adenosine diphosphate-ribosylation, cyclic adenosine monophosphate formation, or fluid accumulation in ligated mouse ileal loops. Both mCTs retained adjuvant properties, since mice given ovalbumin (OVA) subcutaneously with mCTs or nCT, but not OVA alone developed high-titered serum anti-OVA immunoglobulin G (IgG) antibodies (Abs) which were largely of IgG1 and IgG2b subclasses. Although nCT induced brisk IgE Ab responses, both mCTs elicited lower anti-OVA IgE Abs. OVA-specific CD4+ T cells were induced by nCT and by mCTs, and quantitative analysis of secreted cytokines and mRNA revealed a T helper cell 2 (Th2)-type response. These results now show that the toxic properties of CT can be separated from adjuvanticity, and the mCTs induce Ab responses via a Th2 cell pathway.
Qualitative Regulation of B Cell Antigen Receptor Signaling by CD19: Selective Requirement for PI3-Kinase Activation, Inositol-1,4,5-Trisphosphate Production and Ca2+ Mobilization
Authors: Buhl Anne Mette , Pleiman Christopher M. , Rickert Robert C. , Cambier John C.
Published: July 2002

Genetic ablation of the B cell surface glycoprotein CD19 severely impairs the humoral immune response. This requirement is thought to reflect a critical role of CD19 in signal transduction that occurs upon antigen C3dg coligation of antigen receptors with CD19 containing type 2 complement receptors (CR2). Here we show that CD19 plays a key accessory role in B cell antigen receptor signaling independent of CR2 coligation and define molecular circuitry by which this function is mediated. While CD19 is not required for antigen-mediated activation of receptor proximal tyrosines kinases, it is critical for activation of phosphatidylinositol 3-kinase (PI3-kinase). PI3-Kinase activation is dependent on phosphorylation of CD19 Y484 and Y515. Antigen-induced CD19-dependent PI3-kinase activation is required for normal phosphoinositide hydrolysis and Ca2+ mobilization responses. Thus, CD19 functions as a B cell antigen receptor accessory molecule that modifies antigen receptor signaling in a qualitative manner.
Vascular Adhesion Protein 1 (VAP-1) Mediates Lymphocyte Subtype-specific, Selectin-independent Recognition of Vascular Endothelium in Human Lymph Nodes
Authors: Salmi Marko , Tohka Sami , Berg Ellen L. , Butcher Eugene C. , Jalkanen Sirpa
Published: July 2002

Interactions between lymphocyte surface receptors and their ligands on vascular endothelial cells regulate the exit of lymphocytes from the circulation. Distinct subsets of mononuclear cells bind to high endothelial venules (HEVs) in different lymphoid organs to a different extent, but the molecular mechanisms behind this selectivity have remained poorly characterized. Here we show that vascular adhesion protein-1 (VAP-1) mediates subtype-specific binding of CD8-positive T cells and natural killer cells to human endothelium. VAP-1–dependent, oligosaccharide-dependent peripheral lymph node (PLN) HEV adhesion under shear was independent of L-selectin, P-selectin glycoprotein ligand 1, and α4 integrins, the known lymphocyte receptors involved in the initial recognition of endothelial cells. PLN HEV adhesion was also critically dependent on peripheral lymph node vascular addressins (PNAds), but lymphocyte L-selectin was absolutely required for PNAd binding. Most lymphocytes relied on both PNAd and VAP-1 in HEV binding. The overlapping function of L-selectin ligands and VAP-1 in PLN introduces a new control point into the lymphocyte extravasation process. Finally, intravital microscopy revealed that VAP-1 is involved in initial interactions between human lymphocytes and endothelial cells in inflamed rabbit mesenterial venules in vivo. In conclusion, VAP-1 is a novel contact-initiating ligand that discriminates between different subpopulations of mononuclear cells and is an appealing target for selective modulation of adhesion of CD8- and CD16-positive effector cells.
Endogenous Myelin Basic Protein Inactivates the High Avidity T Cell Repertoire
Authors: Targoni Oleg S. , Lehmann Paul V.
Published: July 2002

To study the contribution of endogenous myelin basic protein (MBP) to the positive and/or negative selection of the MBP-specific T cell repertoire, we studied the T cell response to MBP in MBP-deficient shiverer and MBP-expressing congenic C3H mice. Immunization with MBP induced a vigorous T cell response in shiverer mice directed against a single I-Ak– restricted immunodominant determinant, the core of which is peptide MBP:79-87 (DENPVVHFF). Injection of this peptide induced a high avidity T cell repertoire in shiverer mice that primarily consisted of clones capable of recognizing the native MBP protein in addition to the peptide itself. These data show that endogenous MBP is not required for the positive selection of an MBP-specific T cell repertoire. C3H mice, in contrast, were selectively unresponsive to the MBP protein and injection of MBP:79-87 peptide induced a low avidity repertoire that could be stimulated only by the peptide, not by the protein. Therefore, endogenous MBP induced profound inactivation of high avidity clones specific for the immunodominant determinant making that determinant appear cryptic.
Interleukin (IL)-1 Receptor–associated Kinase (IRAK) Requirement for Optimal Induction of Multiple IL-1 Signaling Pathways and IL-6 Production
Authors: Kanakaraj Palanisamy , Schafer Peter H. , Cavender Druie E. , Wu Ying , Ngo Karen , Grealish Patrick F. , Wadsworth Scott A. , Peterson Per A. , Siekierka John J. , Harris Crafford A. , Fung-Leung Wai-Ping
Published: July 2002

Interleukin (IL)-1 is a proinflammatory cytokine with pleiotropic effects in inflammation. IL-1 binding to its receptor triggers a cascade of signaling events, including activation of the stress-activated mitogen-activated protein (MAP) kinases, c-Jun NH2-terminal kinase (JNK) and p38 MAP kinase, as well as transcription factor nuclear factor κB (NF-κB). IL-1 signaling results in cellular responses through induction of inflammatory gene products such as IL-6. One of the earliest events in IL-1 signaling is the rapid interaction of IL-1 receptor–associated kinases, IRAK and IRAK-2, with the receptor complex. The relative roles of IRAK and IRAK-2 in IL-1 signaling pathways and subsequent cellular responses have not been previously determined. To evaluate the importance of IRAK in IL-1 signaling, IRAK-deficient mouse fibroblast cells were prepared and studied. Here we report that IL-1–mediated activation of JNK, p38, and NF-κB were all reduced in embryonic fibroblasts deficient in IRAK expression. In addition, IL-6 production in response to IL-1 was also dramatically reduced in IRAK-deficient embryonic fibroblasts and in skin fibroblasts prepared from IRAK-deficient mice. Our results demonstrate that IRAK plays an essential proximal role in coordinating multiple IL-1 signaling pathways for optimal induction of cellular responses.
Production of Mice Deficient in Genes for Interleukin (IL)-1α, IL-1β, IL-1α/β, and IL-1 Receptor Antagonist Shows that IL-1β Is Crucial in Turpentine-induced Fever Development and Glucocorticoid Secretion
Authors: Horai Reiko , Asano Masahide , Sudo Katsuko , Kanuka Hirotaka , Suzuki Masatoshi , Nishihara Masugi , Takahashi Michio , Iwakura Yoichiro
Published: July 2002

Interleukin (IL)-1 is a major mediator of inflammation and exerts pleiotropic effects on the neuro-immuno-endocrine system. To elucidate pathophysiological roles of IL-1, we have first produced IL-1α/β doubly deficient (KO) mice together with mice deficient in either the IL-1α, IL-1β, or IL-1 receptor antagonist (IL-1ra) genes. These mice were born healthy, and their growth was normal except for IL-1ra KO mice, which showed growth retardation after weaning. Fever development upon injection with turpentine was suppressed in IL-1β as well as IL-1α/β KO mice, but not in IL-1α KO mice, whereas IL-1ra KO mice showed an elevated response. At this time, expression of IL-1β mRNA in the diencephalon decreased 1.5-fold in IL-1α KO mice, whereas expression of IL-1α mRNA decreased >30-fold in IL-1β KO mice, suggesting mutual induction between IL-1α and IL-1β. This mutual induction was also suggested in peritoneal macrophages stimulated with lipopolysaccharide in vitro. In IL-1β KO mice treated with turpentine, the induction of cyclooxygenase-2 (EC 1.14.99.1) in the diencephalon was suppressed, whereas it was enhanced in IL-1ra KO mice. We also found that glucocorticoid induction 8 h after turpentine treatment was suppressed in IL-1β but not IL-1α KO mice. These observations suggest that IL-1β but not IL-1α is crucial in febrile and neuro-immuno-endocrine responses, and that this is because IL-1α expression in the brain is dependent on IL-1β. The importance of IL-1ra both in normal physiology and under stress is also suggested.
A Critical Role of the p75 Tumor Necrosis Factor Receptor (p75TNF-R) in Organ Inflammation Independent of  TNF, Lymphotoxin α, or the p55TNF-R
Authors: Douni Eleni , Kollias George
Published: July 2002

Despite overwhelming evidence that enhanced production of the p75 tumor necrosis factor receptor (p75TNF-R) accompanies development of specific human inflammatory pathologies such as multi-organ failure during sepsis, inflammatory liver disease, pancreatitis, respiratory distress syndrome, or AIDS, the function of this receptor remains poorly defined in vivo. We show here that at levels relevant to human disease, production of the human p75TNF-R in transgenic mice results in a severe inflammatory syndrome involving mainly the pancreas, liver, kidney, and lung, and characterized by constitutively increased NF-κB activity in the peripheral blood mononuclear cell compartment. This process is shown to evolve independently of the presence of TNF, lymphotoxin α, or the p55TNF-R, although coexpression of a human TNF transgene accelerated pathology. These results establish an independent role for enhanced p75TNF-R production in the pathogenesis of inflammatory disease and implicate the direct involvement of this receptor in a wide range of human inflammatory pathologies.
An Invariant T Cell Receptor α Chain Defines a Novel TAP-independent Major Histocompatibility Complex Class Ib–restricted α/β T Cell Subpopulation in Mammals
Authors: Tilloy Florence , Treiner Emmanuel , Park Se-Ho , Garcia Corinne , Lemonnier François , de la Salle Henri , Bendelac Albert , Bonneville Marc , Lantz Olivier
Published: July 2002

We describe here a new subset of T cells, found in humans, mice, and cattle. These cells bear a canonical T cell receptor (TCR) α chain containing hAV7S2 and AJ33 in humans and the homologous AV19-AJ33 in mice and cattle with a CDR3 of constant length. These T cells are CD4−CD8− double-negative (DN) T cells in the three species and also CD8αα in humans. In humans, their frequency was ∼1/10 in DN, 1/50 in CD8α+, and 1/6,000 in CD4+ lymphocytes, and they display an activated/memory phenotype (CD45RAloCD45RO+). They preferentially use hBV2S1 and hBV13 segments and have an oligoclonal Vβ repertoire suggesting peripheral expansions. These cells were present in major histocompatibility complex (MHC) class II– and transporter associated with antigen processing (TAP)-deficient humans and mice and also in classical MHC class I– and CD1-deficient mice but were absent from β2-microglobulin–deficient mice, indicating their probable selection by a nonclassical MHC class Ib molecule distinct from CD1. The conservation between mammalian species, the abundance, and the unique selection pattern suggest an important role for cells using this novel canonical TCR α chain.
Signal Transducer and Activator of  Transcription (STAT)5 Activation by BCR/ABL Is Dependent on Intact Src Homology (SH)3 and SH2 Domains of BCR/ABL and Is Required for Leukemogenesis
Authors: Nieborowska-Skorska Malgorzata , Wasik Mariusz A. , Slupianek Artur , Salomoni Paolo , Kitamura Toshio , Calabretta Bruno , Skorski Tomasz
Published: July 2002

Signal transducer and activator of transcription (STAT)5 is constitutively activated in BCR/ ABL-expressing cells, but the mechanisms and functional consequences of such activation are unknown. We show here that BCR/ABL induces phosphorylation and activation of STAT5 by a mechanism that requires the BCR/ABL Src homology (SH)2 domain and the proline-rich binding site of the SH3 domain. Upon expression in 32Dcl3 growth factor–dependent myeloid precursor cells, STAT5 activation–deficient BCR/ABL SH3+SH2 domain mutants functioned as tyrosine kinase and activated Ras, but failed to protect from apoptosis induced by withdrawal of interleukin 3 and/or serum and did not induce leukemia in severe combined immunodeficiency mice. In complementation assays, expression of a dominant-active STAT5B mutant (STAT5B-DAM), but not wild-type STAT5B (STAT5B-WT), in 32Dcl3 cells transfected with STAT5 activation–deficient BCR/ABL SH3+SH2 mutants restored protection from apoptosis, stimulated growth factor–independent cell cycle progression, and rescued the leukemogenic potential in mice. Moreover, expression of a dominant-negative STAT5B mutant (STAT5B-DNM) in 32Dcl3 cells transfected with wild-type BCR/ABL inhibited apoptosis resistance, growth factor–independent proliferation, and the leukemogenic potential of these cells. In retrovirally infected mouse bone marrow cells, expression of STAT5B-DNM inhibited BCR/ABL-dependent transformation. Moreover, STAT5B-DAM, but not STAT5B-WT, markedly enhanced the ability of STAT5 activation–defective BCR/ABL SH3+SH2 mutants to induce growth factor–independent colony formation of primary mouse bone marrow progenitor cells. However, STAT5B-DAM did not rescue the growth factor–independent colony formation of kinase-deficient K1172R BCR/ABL or the triple mutant Y177F+R522L+ Y793F BCR/ABL, both of which also fail to activate STAT5. Together, these data demonstrate that STAT5 activation by BCR/ABL is dependent on signaling from more than one domain and document the important role of STAT5-regulated pathways in BCR/ABL leukemogenesis.
The Inhibitor of Death Receptor Signaling, Flice-Inhibitory Protein Defines a New Class of Tumor Progression Factors
Authors: Djerbi Mounira , Screpanti Valentina , Catrina Anca Irinel , Bogen Bjarne , Biberfeld Peter , Grandien Alf
Published: July 2002

Death receptor–mediated apoptosis can be modulated by several antiapoptotic proteins, such as the FLICE (FADD [Fas-associated death domain]-like IL-1β–converting enzyme)-inhibitory proteins (FLIPs). The FLIP family includes both cellular and viral members. The Kaposi's sarcoma–associated herpesvirus protein (KSHV)-FLIP is expressed by human herpesvirus 8 (HHV-8), which is associated with malignancies such as Kaposi's sarcoma and certain lymphomas. In this paper, we demonstrate that KSHV-FLIP protects cells from Fas-mediated apoptosis by inhibiting caspase activation and permits clonal growth in the presence of death stimuli in vitro. Furthermore, we show that KSHV-FLIP can act as a tumor progression factor by promoting tumor establishment and growth in vivo. When injected into immunocompetent recipient mouse strains, murine B lymphoma cells (A20) transduced with KSHV-FLIP rapidly develop into aggressive tumors showing a high rate of survival and growth. The tumor-progressive activity of KSHV-FLIP is mediated by prevention of death receptor–induced apoptosis triggered by conventional T cells. Consequently, inhibitors of death receptor signaling can be regarded as a new class of tumor progression factors, and HHV-8–associated tumors may represent naturally occurring examples of the tumorigenic effect of such inhibitors.
The Formation of Immunogenic Major Histocompatibility Complex Class II–Peptide Ligands in Lysosomal Compartments of Dendritic Cells Is Regulated by Inflammatory Stimuli
Authors: Inaba Kayo , Turley Shannon , Iyoda Tomonori , Yamaide Fumiya , Shimoyama Susumu , e Sousa Caetano Reis , Germain Ronald N. , Mellman Ira , Steinman Ralph M.
Published: July 2002

During their final differentiation or maturation, dendritic cells (DCs) redistribute their major histocompatibility complex (MHC) class II products from intracellular compartments to the plasma membrane. Using cells arrested in the immature state, we now find that DCs also regulate the initial intracellular formation of immunogenic MHC class II–peptide complexes. Immature DCs internalize the protein antigen, hen egg lysozyme (HEL), into late endosomes and lysosomes rich in MHC class II molecules. There, despite extensive colocalization of HEL protein and MHC class II products, MHC class II–peptide complexes do not form unless the DCs are exposed to inflammatory mediators such as tumor necrosis factor α, CD40 ligand, or lipoplolysaccharide. The control of T cell receptor (TCR) ligand formation was observed using the C4H3 monoclonal antibody to detect MHC class II–HEL peptide complexes by flow cytometry and confocal microscopy, and with HEL-specific 3A9 transgenic T cells to detect downregulation of the TCR upon MHC–peptide encounter. Even the binding of preprocessed HEL peptide to MHC class II is blocked in immature DCs, including the formation of C4H3 epitope in MHC class II compartments, suggesting an arrest to antigen presentation at the peptide-loading step, rather than an enhanced degradation of MHC class II–peptide complexes at the cell surface, as described in previous work. Therefore, the capacity of late endosomes and lysosomes to produce MHC class II–peptide complexes can be strictly controlled during DC differentiation, helping to coordinate antigen acquisition and inflammatory stimuli with formation of TCR ligands. The increased ability of maturing DCs to load MHC class II molecules with antigenic cargo contributes to the >100-fold enhancement of the subsequent primary immune response observed when immature and mature DCs are compared as immune adjuvants in culture and in mice.
Complement Receptor 1/Cd35 Is a Receptor for Mannan-Binding Lectin
Authors: Ghiran Ionita , Barbashov Sergi F. , Klickstein Lloyd B. , Tas Sander W. , Jensenius Jens C. , Nicholson-Weller Anne
Published: July 2002

Mannan-binding lectin (MBL), a member of the collectin family, is known to have opsonic function, although identification of its cellular receptor has been elusive. Complement C1q, which is homologous to MBL, binds to complement receptor 1 (CR1/CD35), and thus we investigated whether CR1 also functions as the MBL receptor. Radioiodinated MBL bound to recombinant soluble CR1 (sCR1) that had been immobilized on plastic with an apparent equilibrium dissociation constant of 5 nM. N-acetyl-d-glucosamine did not inhibit sCR1–MBL binding, indicating that the carbohydrate binding site of MBL is not involved in binding CR1. C1q inhibited MBL binding to immobilized sCR1, suggesting that MBL and C1q might bind to the same or adjacent sites on CR1. MBL binding to polymorphonuclear leukocytes (PMNs) was associated positively with changes in CR1 expression induced by phorbol myristate acetate. Finally, CR1 mediated the adhesion of human erythrocytes to immobilized MBL and functioned as a phagocytic receptor on PMNs for MBL–immunoglobulin G opsonized bacteria. Thus, MBL binds to both recombinant sCR1 and cellular CR1, which supports the role of CR1 as a cellular receptor for the collectin MBL.
Epitope-specific Evolution of Human CD8+ T Cell Responses from Primary to Persistent Phases of Epstein-Barr Virus Infection
Authors: Hislop Andrew D. , Annels Nicola E. , Gudgeon Nancy H. , Leese Alison M. , Rickinson Alan B.
Published: July 2002

Primary virus infection often elicits a large CD8+ T cell response which subsequently contracts to a smaller memory T cell pool; the relationship between these two virus-specific populations is not well understood. Here we follow the human CD8+ T cell response to Epstein-Barr virus (EBV) from its primary phase in infectious mononucleosis (IM) through to the persistent carrier state. Using HLA-A2.1 or B8 tetramers specific for four lytic cycle and three latent cycle epitopes, we find marked differences in the epitope-specific composition of the T cell populations between the two phases of infection. The primary response is dominated by lytic epitope specificities which are severely culled (and in one case extinguished) with resolution of the acute infection; in contrast latent epitope specificities are less abundant, if present at all, in acute IM but often then increase their percentage representation in the CD8 pool. Even comparing epitopes of the same type, the relative size of responses seen in primary infection does not necessarily correlate with that seen in the longer term. We also follow the evolution of phenotypic change in these populations and show that, from a uniform CD45RA−RO+CCR7− phenotype in IM, lytic epitope responses show greater reversion to a CD45RA+RO− phenotype whereas latent epitope responses remain CD45RA−RO+ with a greater tendency to acquire CCR7. Interestingly these phenotypic distinctions reflect the source of the epitope as lytic or latent, and not the extent to which the response has been amplified in vivo.
The Ligand-binding Domain of CD22 Is Needed for Inhibition of the B Cell Receptor Signal, as Demonstrated by a Novel Human CD22-specific Inhibitor Compound
Authors: Kelm Soerge , Gerlach Judith , Brossmer Reinhard , Danzer Claus-Peter , Nitschke Lars
Published: July 2002

CD22 is a B cell–specific transmembrane protein of the Siglec family. It binds specifically to α2,6-linked sialic acid (Sia) residues, which are also present on glycoproteins on the B cell surface. CD22 acts as a negative regulator in B cell receptor–mediated signaling by recruitment of Src homology 2 domain–containing tyrosine phosphatase (SHP)-1 to its intracellular tail. To analyze how ligand-binding of CD22 influences its intracellular signaling domain, we designed synthetic sialosides as inhibitors for the lectin domain of CD22. One of these compounds inhibited binding of human CD22-Fc to target cells over 200-fold better than Sia and was highly selective for human CD22. When Daudi cells or primary B cells were stimulated with anti-immunoglobulin (Ig)M in presence of this sialoside inhibitor, a higher Ca2+ response was observed, similar to CD22-deficient B cells. Accordingly, a lower tyrosine-phosphorylation of CD22 and SHP-1 recruitment was demonstrated in presence of the sialoside. Thus, by interfering with ligand binding of CD22 on the B cell surface, we have shown for the first time that the lectin domain of CD22 has a direct, positive influence on its intracellular inhibitory domain. Also, we have developed a novel low molecular weight compound which can enhance the response of human B cells.
The 𝐿_{𝑝} version of Newman’s Inequality for lacunary polynomials
Authors: Borwein Peter , Erdélyi Tamás
Published: July 2002

The principal result of this paper is the establishment of the essentially sharp Markov-type inequality
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="double-vertical-bar x upper P prime left-parenthesis x right-parenthesis double-vertical-bar Subscript upper L Sub Subscript p Subscript left-bracket 0 comma 1 right-bracket Baseline less-than-or-equal-to left-parenthesis 1 slash p plus 12 left-parenthesis sigma-summation Underscript j equals 0 Overscript n Endscripts left-parenthesis lamda Subscript j Baseline plus 1 slash p right-parenthesis right-parenthesis right-parenthesis double-vertical-bar upper P double-vertical-bar Subscript upper L Sub Subscript p Subscript left-bracket 0 comma 1 right-bracket">

‖
x

P
′

(
x
)

‖

L
p

[
0
,
1
]

≤

(
1

/

p
+
12

(

∑

j
=
0

n

(

λ
j

+
1

/

p
)
)

)

‖
P

‖

L
p

[
0
,
1
]

\|xP’ (x)\|_{L_p[0,1]} \leq \left (1/p+12 \left ({\sum ^n_{j=0}}(\lambda _j + 1/p)\right )\right ) \|P\|_{L_p[0,1]}

\]
for every

P
∈
span
⁡
{

x

λ
0

,

x

λ
1

,
…
,

x

λ
n

}

P \in \operatorname {span}\{x^{\lambda _0}, x^{\lambda _1}, \ldots , x^{\lambda _n}\}

with distinct real exponents

λ
j

\lambda _j

greater than

−
1

/

p

-1/p

and for every

p
∈
[
1
,
∞
]

p \in [1, \infty ]

. A remarkable corollary of the above is the Nikolskii-type inequality
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="double-vertical-bar y Superscript 1 slash p Baseline upper P left-parenthesis y right-parenthesis double-vertical-bar Subscript upper L Sub Subscript normal infinity Subscript left-bracket 0 comma 1 right-bracket Baseline less-than-or-equal-to 13 left-parenthesis sigma-summation Underscript j equals 0 Overscript n Endscripts left-parenthesis lamda Subscript j Baseline plus 1 slash p right-parenthesis right-parenthesis Superscript 1 slash p Baseline double-vertical-bar upper P double-vertical-bar Subscript upper L Sub Subscript p Subscript left-bracket 0 comma 1 right-bracket">

‖

y

1

/

p

P
(
y
)

‖

L
∞

[
0
,
1
]

≤
13

(

∑

j
=
0

n

(

λ
j

+
1

/

p
)
)

1

/

p

‖
P

‖

L
p

[
0
,
1
]

\|y^{1/p}P(y)\|_{L_\infty [0,1]} \leq 13 \left ({\sum ^n_{j=0}}(\lambda _j + 1/p)\right )^{1/p} \|P\|_{L_p[0,1]}

\]
for every

P
∈
span
⁡
{

x

λ
0

,

x

λ
1

,
…
,

x

λ
n

}

P \in \operatorname {span}\{x^{\lambda _0}, x^{\lambda _1}, \ldots , x^{\lambda _n}\}

with distinct real exponents

λ
j

\lambda _j

greater than

−
1

/

p

-1/p

and for every

p
∈
[
1
,
∞
]

p \in [1, \infty ]

. Some related results are also discussed.
Weak separation properties for self-similar sets
Authors: Zerner Martin
Published: July 2002

We develop a theory for self-similar sets in

R

s

\mathbb R^s

that fulfil the weak separation property of Lau and Ngai, which is weaker than the open set condition of Hutchinson.
The toric ℎ-vectors of partially ordered sets
Authors: Bayer Margaret , Ehrenborg Richard
Published: July 2002

An explicit formula for the toric

h
h

-vector of an Eulerian poset in terms of the

c
d

\mathbf {cd}

-index is developed using coalgebra techniques. The same techniques produce a formula in terms of the flag

h
h

-vector. For this, another proof based on Fine’s algorithm and lattice-path counts is given. As a consequence, it is shown that the Kalai relation on dual posets,

g

n

/

2

(
P
)
=

g

n

/

2

(

P
∗

)

g_{n/2}(P)=g_{n/2}(P^*)

, is the only equation relating the

h
h

-vectors of posets and their duals. A result on the

h
h

-vectors of oriented matroids is given. A simple formula for the

c
d

\mathbf {cd}

-index in terms of the flag

h
h

-vector is derived.
The possible orders of solutions of linear differential equations with polynomial coefficients
Authors: Gundersen Gary , Steinbart Enid , Wang Shupei
Published: July 2002

We find specific information about the possible orders of transcendental solutions of equations of the form
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="f Superscript left-parenthesis n right-parenthesis Baseline plus p Subscript n minus 1 Baseline left-parenthesis z right-parenthesis f Superscript left-parenthesis n minus 1 right-parenthesis Baseline plus midline-horizontal-ellipsis plus p 0 left-parenthesis z right-parenthesis f equals 0">

f

(
n
)

+

p

n
−
1

(
z
)

f

(
n
−
1
)

+
⋯
+

p

0

(
z
)
f
=
0

f^{(n)}+p_{n-1}(z)f^{(n-1)}+\cdots +p_{0}(z)f=0

, where

p
0

(
z
)
,

p
1

(
z
)
,
…
,

p

n
−
1

(
z
)

p_0(z), p_1(z),\dots , p_{n-1}(z)

are polynomials with

p
0

(
z
)
≢
0

p_0(z) \not \equiv 0

. Several examples are given.
Dense admissible sequences
Authors: Clark David , Jarvis Norman
Published: July 2002

A sequence of integers in an interval of length

x
x

is called admissible if for each prime there is a residue class modulo the prime which contains no elements of the sequence. The maximum number of elements in an admissible sequence in an interval of length

x
x

is denoted by

ϱ

∗

(
x
)

\varrho ^{*}(x)

. Hensley and Richards showed that

ϱ

∗

(
x
)
>
π
(
x
)

\varrho ^{*}(x)>\pi (x)

for large enough

x
x

. We increase the known bounds on the set of

x
x

satisfying

ϱ

∗

(
x
)
≤
π
(
x
)

\varrho ^{*}(x)\le \pi (x)

and find smaller values of

x
x

such that

ϱ

∗

(
x
)
>
π
(
x
)

\varrho ^{*}(x)>\pi (x)

. We also find values of

x
x

satisfying

ϱ

∗

(
x
)
>
2
π
(
x

/

2
)

\varrho ^{*}(x)>2\pi (x/2)

. This shows the incompatibility of the conjecture

π
(
x
+
y
)
−
π
(
y
)
≤
2
π
(
x

/

2
)

\pi (x+y)-\pi (y)\le 2\pi (x/2)

with the prime

k
k

-tuples conjecture.
On the non-existence of 𝜀-uniform finite difference methods on uniform meshes for semilinear two-point boundary value problems
Authors: Farrell Paul , Miller John , O’Riordan Eugene , Shishkin Grigorii
Published: July 2002

In this paper fitted finite difference methods on a uniform mesh with internodal spacing

h
h

, are considered for a singularly perturbed semilinear two-point boundary value problem. It is proved that a scheme of this type with a frozen fitting factor cannot converge

ε
\varepsilon

-uniformly in the maximum norm to the solution of the differential equation as the mesh spacing

h
h

goes to zero. Numerical experiments are presented which show that the same result is true for a number of schemes with variable fitting factors.
A comparison of regularizations for an ill-posed problem
Authors: Ames Karen , Clark Gordon , Epperson James , Oppenheimer Seth
Published: July 2002

We consider numerical methods for a “quasi-boundary value” regularization of the backward parabolic problem given by
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartLayout Enlarged left-brace 1st Row 1st Column u Subscript t Baseline plus upper A u equals 0 comma 2nd Column a m p semicolon 0 greater-than t greater-than upper T 2nd Row 1st Column u left-parenthesis upper T right-parenthesis equals f comma 2nd Column a m p semicolon EndLayout">

{

u
t

+
A
u
=
0
,

a
m
p
;
0
>
t
>
T

u
(
T
)
=
f
,

a
m
p
;

\begin {cases} u_t+Au=0, & 0>t>T \\ u(T)=f, & \end {cases}

\]
where

A
A

is positive self-adjoint and unbounded. The regularization, due to Clark and Oppenheimer, perturbs the final value

u
(
T
)

u(T)

by adding

α
u
(
0
)

\alpha u(0)

, where

α
\alpha

is a small parameter. We show how this leads very naturally to a reformulation of the problem as a second-kind Fredholm integral equation, which can be very easily approximated using methods previously developed by Ames and Epperson. Error estimates and examples are provided. We also compare the regularization used here with that from Ames and Epperson.
Examples of genus two CM curves defined over the rationals
Authors: van Wamelen Paul
Published: July 2002

We present the results of a systematic numerical search for genus two curves defined over the rationals such that their Jacobians are simple and have endomorphism ring equal to the ring of integers of a quartic CM field. Including the well-known example

y
2

=

x
5

−
1

y^2 = x^5 - 1

we find 19 non-isomorphic such curves. We believe that these are the only such curves.
Large character sums
Authors: Granville Andrew , Soundararajan K.
Published: July 2002

We make conjectures and give estimates for how large character sums can be as we vary over all characters mod

q
q

, and as we vary over real, quadratic characters. In particular we show that the largest sums seem to depend on the value of the character at “smooth numbers”.
Construction of tame supercuspidal representations
Authors: Yu Jiu-Kang
Published: July 2002

We give a quite general construction of irreducible supercuspidal representations and supercuspidal types (in the sense of Bushnell and Kutzko) of

p
p

-adic groups. In the tame case, the construction should include all known constructions, and it is expected that this gives all supercuspidal representations. We also give a conjectural Hecke algebra isomorphism, which can be used to analyze arbitrary irreducible admissible representations, following the ideas of Howe and Moy.
Caveolae Are Highly Immobile Plasma Membrane Microdomains, Which Are not Involved in Constitutive Endocytic Trafficking
Authors: Thomsen Peter , Roepstorff Kirstine , Stahlhut Martin , van Deurs Bo
Published: July 2002

To investigate whether caveolae are involved in constitutive endocytic trafficking, we expressed N- and C- terminally green fluorescent protein (GFP)-tagged caveolin- 1 fusion proteins in HeLa, A431, and Madin-Darby canine kidney cells. The fusion proteins were shown by immunogold labeling to be sorted correctly to caveolae. By using confocal microscopy and photobleaching techniques, it was found that although intracellular structures labeled with GFP-tagged caveolin were dynamic, GFP-labeled caveolae were very immobile. However, after incubation with methyl- β-cyclodextrin, distinct caveolae disappeared and the mobility of GFP-tagged caveolin in the plasma membrane increased. Treatment of cells with cytochalasin D caused lateral movement and aggregation of GFP-labeled caveolae. Therefore, both cholesterol and an intact actin cytoskeleton are required for the integrity of GFP-labeled caveolae. Moreover, stimulation with okadaic acid caused increased mobility and internalization of the labeled caveolae. Although the calculated mobile fraction (for t = ∞) of intracellular, GFP-tagged caveolin- associated structures was 70–90%, GFP-labeled caveolae in unstimulated cells had a mobile fraction of <20%, a value comparable to that previously reported for E-cadherin in junctional complexes. We therefore conclude that caveolae are not involved in constitutive endocytosis but represent a highly stable plasma membrane compartment anchored by the actin cytoskeleton.
EVA: continuous automatic evaluation of protein structure
prediction servers
Authors: Eyrich Volker A. , Martı́-Renom Marc
A. , Przybylski Dariusz , Madhusudhan Mallur S. , Fiser András , Pazos Florencio , Valencia Alfonso , Sali Andrej , Rost Burkhard
Published: July 2002

Summary: Evaluation of protein structure prediction methods is difficult and time-consuming. Here, we describe EVA, a web server for assessing protein structure prediction methods, in an automated, continuous and large-scale fashion. Currently, EVA evaluates the performance of a variety of prediction methods available through the internet. Every week, the sequences of the latest experimentally determined protein structures are sent to prediction servers, results are collected, performance is evaluated, and a summary is published on the web. EVA has so far collected data for more than 3000 protein chains. These results may provide valuable insight to both developers and users of prediction methods.

Availability: http://cubic.bioc.columbia.edu/eva.

Contact: eva@cubic.bioc.columbia.edu

* To whom correspondence should be addressed.
HIV-1 receptors and cell tropism
Authors: Clapham Paul R , McKnight Áine
Published: July 2002

HIV virus particles interact with several receptors on cell surfaces. Two receptors, CD4 and a co-receptor act sequentially to trigger fusion of viral and cellular membranes and confer virus entry into cells. For HIV-1, the chemokine receptor CCR5 is the predominant co-receptor exploited for transmission and replication in vivo. Variants that switch to use CXCR4 and perhaps other co-receptors evolve in some infected individuals and have altered tropism and pathogenic properties. Other cell surface receptors including mannose binding protein on macrophages and DC-SIGN on dendritic cells also interact with gp120 on virus particles but do not actively promote fusion and virus entry. These receptors may tether virus particles to cells enabling interactions with suboptimal concentrations of CD4 and/or co-receptors. Alternatively such receptors may transport cell surface trapped virions into lymph nodes before transmitting them to susceptible cells. Therapeutic strategies that prevent HIV from interacting with receptors are currently being developed. This review describes how the interaction and use of different cellular receptors influences HIV tropism and pathogenesis in vivo.
Reprogrammed gene expression in a somatic cell‐free extract
Authors: Landsverk Helga B , Håkelien Anne‐Mari , Küntziger Thomas , Robl James M , Skålhegg Bjørn S , Collas Philippe
Published: July 2002

We have developed a somatic cell‐free system that remodels chromatin and activates gene expression in heterologous differentiated nuclei. Extracts of stimulated human T cells elicit chromatin binding of transcriptional activators of the interleukin‐2 (IL‐2) gene, anchoring and activity of a chromatin‐remodeling complex and hyperacetylation of the IL‐2 promoter in purified exogenous resting T‐cell nuclei. The normally repressed IL‐2 gene is transcribed in nuclei from quiescent human T cells and from various non‐T‐cell lines. This demonstrates that somatic cell extracts can be used to reprogram gene expression in differentiated nuclei. In vitro reprogramming may be useful for investigating regulation of gene expression and for producing replacement cells for the treatment of a wide variety of diseases.
Genetic manipulation of insulin signaling, action and secretion in mice
Authors: Baudry Anne , Leroux Loïc , Jackerott Malene , Joshi Rajiv L
Published: July 2002

Non‐insulin‐dependent diabetes mellitus (NIDDM) is a complex heterogeneous polygenic disease characterized mainly by insulin resistance and pancreatic β‐cell dysfunction. In recent years, several genetically engineered mouse models have been developed for the study of the pathophysiological consequences of defined alterations in a single gene or in a set of candidate diabetogenes. These represent new tools that are providing invaluable insights into NIDDM pathogenesis. In this review, we highlight the lessons emerging from the study of some of the transgenic or knockout mice in which the expression of key actors in insulin signaling, action or secretion has been manipulated. In addition to contributing to our knowledge of the specific roles of individual genes in the control of glucose homeostasis, these studies have made it possible to address several crucial issues in NIDDM that have remained controversial or unanswered for a number of years.
Regulation of monocyte chemoattractant protein (MCP)‐1 transcription by interferon‐gamma (IFN‐γ) in human astrocytoma cells: postinduction refractory state of the gene, governed by its upstream elements
Authors: ZHOU Z.‐H. LUCY , HAN YULONG , WEI TAO , ARAS SUMER , CHATURVEDI PRIYA , TYLER SARAH , RANI M. R SANDHYA , RANSOHOFF RICHARD M.
Published: July 2002

Monocyte chemoattractant protein (MCP)‐1 is expressed by astrocytes in diverse inflammatory states and is a key regulator of monocyte recruitment to the central nervous system (CNS). In the current study, we addressed mechanisms by which transcription of the human MCP‐1 gene (hMCP‐1) was terminated, after induction by interferon (IFN)‐γ. Our results demonstrated that IFN‐γ‐induced transcription of hMCP‐1 was followed by a refractory state, during which hMCP‐1 was resistant to restimulation by either IFN‐γ or heterologous activators such as TNF‐α. This refractory state affected the hMCP‐1 gene selectively, as other IFN‐γ‐inducible genes remained responsive to restimulation. The IFN‐γ‐induced hMCP‐1 refractory state was governed at the transcriptional level and was sensitive to protein synthesis inhibitors, suggesting a requirement for newly expressed components. A minimal 213 base pair hMCP‐1 regulatory element directed both IFN‐γ‐mediated transcription and the subsequent refractory state. We previously demonstrated that IFN‐γ treatment resulted in coordinate protein occupancy in vivo of two hMCP‐1 promoter elements, a gamma‐activated site (GAS) and a GC‐rich element. During the refractory state, IFN‐γ treatment failed to induce protection of either the hMCP‐1 GAS element or the GC box. These results furnish insight into the expression of hMCP‐1 during CNS inflammation and provide the first delineation of an IFN‐γ‐induced transcriptional refractory state.—Zhou, Z.‐H. L., Han, Y., Wei, T., Aras, S., Chaturvedi, P., Tyler, S., Rani, M. R. S., Ransohoff, R. M. Regulation of monocyte chemoattractant protein (MCP)‐1 transcription by interferon‐gamma (IFN‐γ) in human astrocytoma cells: postinduction refractory state of the gene, governed by its upstream elements. FASEB J. 15, 383‐392 (2001)
THE CROONIAN LECTURE 1997. The phosphorylation of proteins on tyrosine: its role in cell growth and disease
Authors: Hunter Tony
Published: July 2002

The reversible phosphorylation of tyrosines in proteins plays a key role in regulating many different processes in eukaryotic organisms, such as growth control, cell cycle control, differentiation, cell shape and movement, gene transcription, synaptic transmission, and insulin action. Phosphorylation of proteins is brought about by enzymes called protein–tyrosine kinases that add phosphate to specific tyrosines in target proteins; phosphate is removed from phosphorylated tyrosines by enzymes called protein–tyrosine phosphatases. Phosphorylated tyrosines are recognized by specialized binding domains on other proteins, and such interactions are used to initiate intracellular signalling pathways. Currently, more than 95 protein–tyrosine kinases and more than 55 protein–tyrosine phosphatase genes are known inHomo sapiens. Aberrant tyrosine phosphorylation is a hallmark of many types of cancer and other human diseases. Drugs are being developed that antagonize the responsible protein–tyrosine kinases and phosphatases in order to combat these diseases.