bluuebunny/crossref_metadata_2025_split huggingface dataset:
Protocadherin Pcdh2 shows properties similar to, but distinct from, those of classical cadherins
Authors: Obata Shuichi , Sago Haruhiko , Mori Nozomu , Rochelle Julie M. , Seldin Michael F. , Davidson Mari , John Tom St , Taketani Shigeru , Suzuki Shintaro T. 
Published: April 2021

ABSTRACT
Cell adhesion and several other properties of a recently identified cadherin-related protein, protocadherin Pcdh2, were characterized. A chimeric Pcdh2 in which the original cytoplasmic domain was replaced with the cytoplasmic domain of E-cadherin was expressed in mouse L cells. The expressed protein had a molecular mass of about 150 kDa and was localized predominantly at the cell periphery, as was the wild-type Pcdh2. In a conventional cell aggregation assay, the transfectants showed cell aggregation activity comparable to that of classical cadherins. This activity was Ca2+-dependent and was inhibited by the addition of anti-Pcdh2 antibody, indicating that the chimeric Pcdh2, and probably the wild-type Pcdh2, has Ca2+-dependent cell aggregation activity. Mixed cell aggregation assay using L cells and different types of transfectants showed that the activity of Pcdh2 was homophilic and molecular type specific and that Pcdh2 transfectants did not aggregate with other types of transfectants or with L cells. In immunoprecipitation, the chimeric Pcdh2 co-precipitated with a 105 kDa and a 95 kDa protein, whereas wild-type Pcdh2 co-precipitated with no major protein. Pcdh2 was easily solubilized with non-ionic detergent, in contrast to the case of classical cadherins. On immunofluorescence microscopy, the somas of Purkinje cells were diffusely stained with anti-human Pcdh2 antibody. Mouse Pcdh1 and Pcdh2 were mapped to a small segment of chromosome 18, suggesting that various protocadherins form a gene cluster at this region. The present results suggest that Pcdh2, and possibly other protocadherins as well as proto-cadherin-related proteins such as Drosophila fat, mediate Ca2+-dependent and specific homophilic cell-cell interaction in vivo and play an important role in cell adhesion, cell recognition, and/or some other basic cell processes.
Integrin signaling: roles for the cytoplasmic tails of αIIbβ3 in the tyrosine phosphorylation of pp125FAK
Authors: Leong Lilley , Hughes Paul E. , Schwartz Martin A. , Ginsberg Mark H. , Shattil Sanford J. 
Published: April 2021

ABSTRACT
pp125FAK (focal adhesion kinase) a protein tyrosine kinase that may mediate cellular responses to adhesion, is activated and tyrosine-phosphorylated when platelets adhere to fibrinogen via the integrin, αIIbβ3. To determine whether either of the cytoplasmic tails of αIIbβ3 regulates FAK phosphorylation, CHO cells were stably transfected with αIIbβ3 or various cytoplasmic tail truncation mutants. Cells expressing wild-type αIIbβ3 or αIIbβ3 that lacked the COOH-terminal 13 or 18 residues of the 20 residue αIIb tail adhered to and spread on fibrinogen or on an anti-αIIb antibody, and FAK became tyrosine-phosphorylated. FAK also became phosphorylated in adherent cells lacking the COOH-terminal 35 or 39 residues of the 47 residue β3 tail, although the extent of phosphorylation was reduced by about 50% in the latter mutant. Little or no FAK phos-phorylation was observed if 46 residues were deleted from the β3 tail. None of these β3 truncation mutants spread on the anti-αIIb antibody. When cells with wild-type αIIbβ3 or truncated β3 were detached from a surface, FAK became rapidly dephosphorylated. In contrast, FAK remained phosphorylated in the two αIIb truncation mutants for up to 90 minutes in suspension. This persistent phosphoryla-tion was not due to occupancy of αIIbβ3 by adhesive ligands because it was also observed with an αIIb tail truncation mutant that contained an additional mutation in the extra-cellular portion of the receptor that prevents ligand binding. These studies demonstrate that: (1) the β3 cyto-plasmic tail, including the membrane-proximal portion, is involved in initiation of FAK phosphorylation; (2) FAK phosphorylation can be initiated by cell adhesion in the absence of cell spreading; and (3) the membrane-distal portion of the αIIb cytoplasmic tail may normally function to dampen FAK phosphorylation in non-anchored cells.
Control of N-cadherin-mediated intercellular adhesion in migrating neural crest cells in vitro
Authors: Monier-Gavelle Frédérique , Duband Jean-Loup 
Published: April 2021

ABSTRACT
Dispersion of neural crest cells and their ultimate regroup-ment into peripheral ganglia are associated with precisely coordinated regulations both in time and space of the expression and function of cell adhesion receptors. In par-ticular, the disappearance of N-cadherin from the cell surface at the onset of migration and its reexpression during cell aggregation suggest that, during migration, N-cadherin expression is repressed in neural crest cells. In the present study, we have analyzed in vitro the mechanism of control of N-cadherin expression and function in migrating neural crest cells. Although these cells moved as a dense popula-tion, each individual did not establish extensive and permanent intercellular contacts with its neighbors. However, cells synthesized and expressed mature N-cadherin molecules at levels comparable to those found in cells that exhibit stable intercellular contacts, but in contrast to them, the bulk of N-cadherin molecules was not connected with the cytoskeleton. We next determined which intracellular events are responsible for the instability of the N-cadherin junctions in neural crest cells using various chemical agents known to affect signal transduction processes. Agents that block a broad spectrum of serine-threonine kinases (6-dimethylaminopurine, H7 and stau-rosporine) or that affect selectively protein kinases C (bisin-dolylmaleimide and sphingosine), inhibitors of protein tyrosine kinases (erbstatin, herbimycin A, and tyrphostins), and inhibitors of phosphatases (vanadate) all restored tight cell-cell associations among neural crest cells, accompanied by a slight increase in the overall cellular content of N-cadherin and its accumulation to the regions of intercellu-lar contacts. The effect of the kinase and phosphatase blockers was inhibitable by agents known to affect protein synthesis (cycloheximide) and exportation (brefeldin A), indicating that the restored cell-cell contacts were mediated chiefly by an intracellular pool of N-cadherin molecules recruited to the membrane. Finally, N-cadherin molecules were constitutively phosphorylated in migrating neural crest cells, but their level and state of phosphorylation were apparently not modified in the presence of kinase and phosphatase inhibitors. These observations therefore suggest that N-cadherin-mediated cell-cell interactions are not stable in neural crest cells migrating in vitro, and that they are under the control of a complex cascade of intracellular signals involving kinases and phosphatases and probably elicited by surface receptors.
Message of nexin 1, a serine protease inhibitor, is accumulated in the follicular papilla during anagen of the hair cycle
Authors: Yu Da-Wen , Yang Tian , Sonoda Tadashige , Gaffney Kevin , Jensen Pamela J. , Dooley Tom , Ledbetter Steve , Freedberg Irwin M. , Lavker Robert , Sun Tung-Tien 
Published: April 2021

ABSTRACT
A group of specialized mesenchymal cells located at the root of the mammalian hair follicle, known as the follicu-lar or dermal papillary cells, are involved in regulating the hair cycle, during which keratinocytes of the lower follicle undergo proliferation, degeneration and regrowth. Using the arbitrarily primed-PCR approach, we have identified a 1.3 kb messenger RNA that is present in large quantities in cultured rat follicular papillary cells, but not in skin fibro-blasts. This mRNA encodes nexin 1, a potent protease inhibitor that can inactivate several growth-modulating serine proteases including thrombin, urokinase and tissue plasminogen activator. In situ hybridization showed that nexin 1 message is accumulated in the follicular papilla cells of anagen follicles, but is undetectable in keratinocytes or other skin mesenchymal cells. In addition, nexin 1 message level varies widely among several immortalized rat vibrissa papillary cell lines, and these levels correlate well with the reported abilities of these cell lines to support in vivo follicular reconstitution. These results suggest a possible role of nexin 1 in regulating hair follicular growth.
Hepatocyte growth factor stimulates extensive development of branching duct-like structures by cloned mammary gland epithelial cells
Authors: Soriano J. V. , Pepper M. S. , Nakamura T. , Orci L. , Montesano R. 
Published: April 2021

ABSTRACT
Although epithelial-mesenchymal (stromal) interactions are thought to play an important role in embryonic and postnatal development of the mammary gland, the underlying mechanisms are still poorly understood. To address this issue, we assessed the effect of fibroblast-derived diffusible factors on the growth and morphogenetic properties of a clonally derived subpopulation (clone TAC-2) of normal murine mammary gland (NMuMG) epithelial cells embedded in collagen gels. Under control conditions, TAC-2 mammary gland epithelial cells suspended within collagen gels formed either irregularly shaped cell aggregates or short branching cord-like structures. Addition of conditioned medium from Swiss 3T3 or MRC-5 fibroblasts dramatically stimulated cord formation by TAC-2 cells, resulting in the development of an extensive, highly arborized system of duct-like structures, which in appropriate sections were seen to contain a central lumen. The effect of fibroblast conditioned medium was completely abrogated by antibodies against hepatocyte growth factor (also known as scatter factor), a fibroblast-derived polypeptide that we have previously shown induces tubulogenesis by Madin-Darby canine kidney epithelial cells. Addition of exogenous recombinant human hepatocyte growth factor to collagen gel cultures of TAC-2 cells mimicked the tubulogenic activity of fibroblast conditioned medium by stimulating formation of branching duct-like structures in a dose-dependent manner, with a maximal 77-fold increase in cord length at 20 ng/ml. The effect of either fibroblast conditioned medium or hepatocyte growth factor was markedly potentiated by the simultaneous addition of hydrocortisone (1 μg/ml), which also enhanced lumen formation. These results demonstrate that hepatocyte growth factor promotes the formation of branching duct-like structures by mammary gland epithelial cells in vitro, and suggest that it may act as a mediator of the inducing effect of mesenchyme (or stroma) on mammary gland development.
Cytostatic factor inactivation is induced by a calcium-dependent mechanism present until the second cell cycle in fertilized but not in parthenogenetically activated mouse eggs
Authors: Zernicka-Goetz Magdalena , Ciemerych Maria A. , Kubiak Jacek Z. , Tarkowski Andrzej K. , Maro Bernard 
Published: April 2021

ABSTRACT
Cytostatic factor (CSF) is an activity responsible for the metaphase II arrest in vertebrate oocytes. This activity maintains a high level of maturation promoting factor (MPF) in the oocyte and both activities are destroyed after fertilization or parthenogenetic activation. To study some of the characteristics of the mechanism involved in MPF and CSF destruction, we constructed hybrid cells between metaphase II arrested oocytes and early embryos obtained after fertilization or artificial activation. We found that the behavior of hybrid cells differed depending upon the type of oocyte activation. Initially, the reaction of both types of hybrid cells was similar, the nuclear envelope broke down and chromatin condensation was induced. However, while metaphase II oocytes fused with parthenogenetic eggs remained arrested in M-phase, the oocytes fused with fertilized eggs underwent activation and passed into interphase. This ability of fertilized eggs to induce oocyte activation was still present at the beginning, but not at the end of the second embryonic cell cycle. Oocyte activation induced by fusion with a fertilized egg could be prevented when calcium was chelated by BAPTA. Thus, element(s) of the mechanism involved in calcium release triggered by a sperm component at fertilization remain(s) active until the second cell cycle and is (are) inactivated before the end of the 2-cell stage.
The glycophosphatidylinositol anchor affects the conformation of thy-1 protein
Authors: Barboni E. , Rivero B. Pliego , George A. J. T. , Martin S. R. , Renouf D. V. , Hounsell E. F. , Barber P. C. , Morris R. J. 
Published: April 2021

ABSTRACT
Thy-1 has the structure of a single variable-type immunoglobulin domain anchored to the external face of the plasma membrane via a glycophosphatidylinositol moiety. When the lipid is removed from this anchor by either phospholipase C or D, the reactivity of the delipidated Thy-1 for a range of antibodies, including those known to be determined by amino acid residues, is impaired. We have investigated in detail the effect of delipidation on the reaction with the OX7 monoclonal antibody, determined by the allelic variant residue Arg 89. Analysis of the kinetics of OX7 binding shows that delipidation affects primarily the dissociation of antibody, increasing the dissociation rate constant kdiss from 0.27×10−3 s−1 to 2.39×10−3 s−1. Addition of phospholipase to preformed antibody-antigen complex causes an immediate change from the slow to the faster dissociation rate, implying that delipidation induces a conformational change in the Thy-1 protein that is sufficiently strong to dissociate bound antibody. This conformational change can be demonstrated directly by the circular dichroism spectrum of human Thy-1 that detects changes in the environment of Tyr residues located near the antigenic epitopes. Molecular dynamics studies suggest that, on delipidation, a conformational change occurs in the glycan chain that affects the protein in the region of the antigenic epitopes. This study thus demonstrates that the glycophosphatidylinositol anchor strongly influences the conformation of Thy-1 protein by a mechanism that could occur generally with membrane proteins of this class.
Behavior of mitochondria in synchronized cells of Chlamydomonas Reinhardtii (chlorophyta)
Authors: Ehara Tomoko , Osafune Tetsuaki , Hase Eiji 
Published: April 2021

ABSTRACT
Cells of Chlamydomonas reinhardtii Dangeard were synchronized under a 12 hour:12 hour light:dark regimen. Behavior of mitochondria in these cells was studied by fluorescence microscopy using a mitochondrial membrane-binding fluorescent dye, dimethylaminostyrylmethylpyridiniumiodine (DASMPI), as well as by electron microscopy.
Following time courses of change in frequency of occurrence of five typical morphologies of mitochondria in synchronized cells, strikingly dynamic behavior of mitochondria was demonstrated. The five types are (A) a giant global mitochondrion with large matrix and peripherally localized cristae, a part of which is in close contact with the nucleus, (B) a mitochondrion composed of thick-corded bodies connected to each other, a part of which is in contact with the nucleus, (C) thin-corded forms with a few branches, (D) small lump forms scattered in the cytoplasm, and (E) stringy forms with intricate branchings extended throughout the cytoplasm. During the early half of the light period, changes of C→B→C→D occur, while the inversely sequential changes of D→C→B→C proceed during the later half of the light period. The appearance of the B-type mitochondrion is accompanied by a transient decrease of O2-uptake activity of cells. The early appearing B-type mitochondrion is temporarily turned into a giant A-type mitochondrion, concomitant with discharge of membranes into the cytoplasm and their retake by the A-type form in the process of reversion to B-type. In the reversion process, partitioning membranes are also formed in the large matrix of A-type mitochondrion. Toward the end of the light period, stringy E-type mitochondria are formed from C-type ones, and apportioned between two dividing protoplasts during an early phase of the dark period. The E-type forms are cut into D-type forms immediately prior to the following cell division into four daughters.
Possible significance of the formation of B- and A-type mitochondrion is discussed.
The organization of spliceosomal components in the nuclei of higher plants
Authors: Beven Alison F. , Simpson Gordon G. , Brown John W. S. , Shaw Peter J. 
Published: April 2021

ABSTRACT
To analyze the organization of spliceosomal snRNPs in plant nuclei, we have used both immunofluorescence labelling with the antibody 4G3, raised against the human snRNP-specific protein U2B′′, and in situ hybridization with anti-sense probes to conserved regions of U1, U2 and U6 snRNAs. The organization comprises a fibrous inter-chromatin network, which may include both interchromatin fibrils and granules, and very prominent nuclear and nucleolar-associated bodies. Double labelling with an anti-p80 coilin antibody shows that these are coiled bodies. Dynamic changes in the labelling pattern were observed through the cell cycle, and in response to and on recovery from heat shock. The similarity of this organization to that observed in mammalian nuclei is strong evidence that it is fundamental to the processing of pre-mRNA in eucaryotes in general.
Expression of Interstitial Collagenase is restricted to skeletal tissue during mouse embryogenesis
Authors: Mattot Virginie , Raes Marie Berthe , Henriet Patrick , Eeckhout Yves , Stehelin Dominique , Vandenbunder Bernard , Desbiens Xavier 
Published: April 2021

ABSTRACT
Collagenases are thought to be involved in physiological and pathological processes that require extracellular matrix remodeling. Using the in situ hybridization technique, we describe the expression of interstitial collagenase gene during mouse embryogenesis between E6.5 and E17. We demonstrate that interstitial collagenase expression is exclusively detected in one event, namely the onset of bone formation. Transcripts accumulate in hypertrophied chondrocytes, found in the mature cartilaginous matrix of long-bone growth plates or ribs, and in osteoblasts and/or in endothelial cells that have migrated into the shafts of developing long bones. The expression of the tissue inhibitor of metalloproteinases (TIMP-2) gene precedes the expression of interstitial collagenase in developing bones. These data suggest that interstitial collagenase plays a specific role in bone development and that the tight regulation of its activity during development is achieved not only by post-translational mechanisms with TIMPs, as previously suggested, but also at the transcriptional level.
The behavior of chick gastrula mesodermal cells under the unidirectional tractive force parallel to the substrata
Authors: Toyoizumi Ryuji , Takeuchi Shigeo 
Published: April 2021

ABSTRACT
Advancement of leading lamellae of a migratory cell inevitably causes a strain inside the cell body. We investigated the effect of the tension arisen inside a mesodermal cell on its behavior by pulling the cell body unidirectionally along the substratum.
Chick gastrula mesodermal cells, known as highly migratory, were dissociated into single cells in sodium citrate buffer, conjugated with paramagnetic beads activated by tosyl-residue (4.5 μm in diameter) and seeded onto coverglasses coated with fibronectin. After the cells spread on the substratum and protruded cellular processes in all directions, they were exposed to a non-uniform magnetic field by a magnet. Thus the cells bearing the beads were pulled with a force in the order of 10−10 N. The behavior of such cells was recorded with a time-lapse video taperecorder and assessed quantitatively.
Shortly after the magnetic force was applied, the beads stuck to the cells were aligned in tandem along the line of magnetic force at the site for the magnet. Subsequently, they frequently came to extend their leading lamella precisely counter to the traction on the line of the beads. Observation with scanning electron microscope revealed that a large part of the beads attached to the cells were wrapped in the cell membrane. In this condition, the cells were stretched locally between the attachment site of the beads and adhesion plaques beneath the leading edge, which was formed in a direction away from the traction. It was proved statistically that such cells tended to locomote away from the magnet at the 0.1% significance level with Hotelling’s T2-test. In contrast, the mesodermal cells free of the artificial traction in three kinds of control experiments did not show such a preference in the direction of locomotion.
These results proved that migratory cells tended to move in the direction away from the tractive force parallel to the substratum, suggesting that advancement of a leading lamella is accelerated when it is stretched along the direction of projection by a mechanical force of sufficient strength. Implication of this finding to the mechanism of cell locomotion will be discussed.
Stimulus-dependent alterations in macrophage microtubules: increased tubulin polymerization and detyrosination
Authors: Robinson John M. , Vandré Dale D. 
Published: April 2021

ABSTRACT
Murine macrophage microtubules are very dynamic. The majority of the microtubules (≈80%) exist in a rapidly depolymerizing pool ( ≈30 seconds). The remaining 20% of the microtubules are in a more slowly depolymerizing pool ( ≈7 minutes). Macrophage microtubules are responsive to cell stimulation with phorbol esters; upon cell stimulation there is a rapid increase in total microtubule polymer and number. In addition there is stimulus-induced detyrosination of α-tubulin in macrophage microtubules that is rapid and essentially complete, occurring in all microtubules rather than a subset of microtubules. Detyrosination of the macrophage microtubules in response to phorbol esters does not confer increased stability to these microtubules, since treated cells have nocodazole-induced depolymerization kinetics similar to that in non-stimulated macrophages. Regrowth of microtubules following washout of nocodazole is also rapid. Interestingly the regrown microtubules are initially in the tyrosinated form even in the presence of phorbol ester. These experiments provide in vivo support for the model that detyrosination of α-tubulin occurs in polymeric tubulin while retyrosination occurs in dimeric tubulin. Macrophage microtubules also demonstrate an unusually rapid response to extracellular stimuli and thus provide a unique model system in which to examine signal transduction events and modulation of microtubules.