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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The endocrine cells of the pancreas develop from the endoderm and yet display several characteristics of a neuronal phenotype. During embryonic life, ductal epithelial cells give rise to first the glugagon-producing cells (alpha-cells) and then cells that express insulin (beta-cells), somatostatin (delta-cells), and pancreatic polypeptide (PP-cells) in a sequential order. The endocrine cells are believed to arise from a stem cell with neuronal traits. The developmental lineage from a common neuron-like progenitor is evidenced by: transient coexpression of more than one cell type-specific hormone in immature cells, expression of neuronal markers during islet cell development, and the pluripotentiality of clones of insulinoma cells to develop into cells expressing other islet cell hormones. The four mature endocrine cell types assume a particular organization within the islets of Langerhans in a process where cell adhesion molecules are involved. In this study we have analyzed the expression of neural cell adhesion molecule (NCAM) and cadherin molecules in neonatal, young, and adult rat islet cells as well as in glucagonomas and insulinomas derived from a pluripotent rat islet cell tumor. Whereas primary islet cells at all ages express unsialylated NCAM and E-cadherin, as do insulinomas, the glucagonomas express the polysialylated NCAM, which is characteristic for developing neurons. The glucagonomas also lose E-cadherin expression and instead express a cadherin which is similar to N-cadherin in brain. Insulinoma cells express E-cadherin but differ from primary islet cells by expressing a second cadherin molecule, which is similar to N-cadherin. The expression of NCAM and cadherin isoforms in the glucagonoma suggest that this transformed alpha-cell type has converted to an immature phenotype with strong neuronal traits, reflecting the early palce of glucagon-producing cells in the islet cell lineage. In contrast, insulinoma cells are more islet-like in their phenotype and show less neuronal traits.
Mol Endocrinol 1992 Aug
PMID:Differential expression of neural cell adhesion molecule and cadherins in pancreatic islets, glucagonomas, and insulinomas. 140 10

One of the consequences of increased intracellular calcium in response to a variety of physiological stimuli is the calcium activation of cytosolic proteases. Unlike lysosomal proteases with broad specificity, these calcium-activated neutral proteases show limited proteolysis of a restricted set of substrate proteins suggesting they may play a regulatory role in cellular physiology. In this study we show that the neural cell adhesion molecules NCAM-180 and N-cadherin are substrates for such endogenous calcium-activated neutral proteases. In contrast, a third neural cell adhesion molecule G4/L1 was not susceptible to calcium-activated proteolysis. The threshold for activation of NCAM and N-cadherin proteolysis is in the micromolar range of calcium suggesting that NCAM and N-cadherin are substrates for a mu-type calpain (calpain I). The site recognized by this protease is within intracellular domains of NCAM-180 and N-cadherin which are important for their interaction with cytoskeletal components. These results suggest that calcium-activated proteolysis at these sites in vivo could disrupt the linkage between extracellular ligand binding to these adhesion molecules and the normal intracellular effectors of such extracellular binding events.
Brain Res Mol Brain Res 1991 Aug
PMID:Calcium-activated proteolysis of intracellular domains in the cell adhesion molecules NCAM and N-cadherin. 166 41

We have used monolayers of parental 3T3 fibroblasts and 3T3 cells expressing transfected cell adhesion molecules (CAMs, NCAM, N-cadherin, or L1) as a culture substrate for cerebellar neurons. Previous studies suggest that the transfected CAMs promote neurite outgrowth by activating a second messenger pathway within the responding neuron that involves influx of calcium into neurons as a consequence of activation of an FGF receptor. The same neurite outgrowth response can be induced by FGF or a number of agents that directly activate defined steps in the CAM signaling pathway. In the present study we show that the neurite outgrowth stimulated by the above three CAMs, FGF, arachidonic acid (AA), and K+ depolarization can be abolished by the Ca2+/calmodulin-dependent (CaM) kinase inhibitor, KN-62. We also demonstrate that neurite outgrowth over astrocytes, which represent a more physiologically relevant cellular substrate, can be substantially inhibited by a number of agents that block the CAM signaling pathway, including KN-62. However, neurite outgrowth induced by activation of protein kinase A is unaffected by inhibition of CaM kinase activity as is basal neurite outgrowth over 3T3 monolayers or a polylysine/laminin substrate. These results suggest that CaM kinase activity is specifically required downstream of calcium influx in the CAM and FGF signaling pathway leading to axonal growth.
Mol Cell Neurosci 1995 Feb
PMID:A Ca2+/calmodulin kinase inhibitor, KN-62, inhibits neurite outgrowth stimulated by CAMs and FGF. 759 59

Desmocollins are cadherin-like adhesion molecules of desmosomes. We have determined the full cDNA sequence of a murine desmocollin, the homologue of human and bovine type 2 desmocollins (DSC2), and studied its tissue distribution and expression in stratified epithelia. An 8.5 day mouse embryo cDNA library was screened yielding overlapping clones which encoded the mouse DSC2. This gene has an open reading frame of 2710 base pairs (bp) encoding a polypeptide of 902 amino acids (aa). The polypeptide comprises a signal peptide, a precursor peptide, and a mature protein of 766 aa having an extracellular domain of 549 aa, a single transmembrane domain and a cytoplasmic domain of 184 aa. Like other desmocollins, murine DSC2 has two products, Dsc2a and Dsc2b, produced by alternative splicing of a 46 bp exon which encodes 11 COOH-terminal aa followed by an in-frame stop codon. Inclusion of this exon forms Dsc2b which is 54 aa shorter than Dsc2a. Mouse Dsc2a shows 75.7% amino acid identity to human and 63.3% identity to bovine Dsc2a. The mouse desmocollin is also homologous to the cadherins; 32.2% to the most closely related typical cadherin, human N-cadherin. DSC2 is ubiquitously expressed in epithelial tissues and the heart of adult mice and from the blastocyst stage of development. In situ hybridization shows that the gene is most strongly expressed suprabasally in stratified epithelia, similar to the expression of bovine DSC2.
Mol Membr Biol
PMID:Cloning, sequence analysis and expression pattern of mouse desmocollin 2 (DSC2), a cadherin-like adhesion molecule. 771 32

Cadherins, a family of transmembrane cell-cell adhesion receptors, require interactions with the cytoskeleton for normal function. To assess the mechanisms of these interactions, we studied the effect of exogenous expression of a mutant N-cadherin, cN390 delta; on epithelial cell-cell adhesion. The intracellular domain of cN390 delta was intact but its extracellular domain was largely deleted so that this molecule was not functional for cell adhesion. cDNA of cN390 delta was attached to the metallothionein promoter, and introduced into the keratinocyte line PAM212 expressing endogenous E- and P-cadherin. When the expression of cN390 delta was induced by Zn2+, cadherin-dependent adhesion of the transfected cells was inhibited, resulting in the dispersion of cell colonies, although their contacts were maintained under high cell density conditions. In these cultures, cN390 delta was expressed not only on the free surfaces of the cells but also at cell-cell junctions. The endogenous cadherins were concentrated at cell-cell junctions under normal conditions. As a result of cN390 delta expression, however, the endogenous cadherins localizing at the cell-cell junctions were largely diminished, suggesting that these molecules were replaced by the mutant molecules at these sites. As a control, we transfected the same cell line with cDNA of a truncated form of N-cadherin cadherin whose intracellular C terminus had been deleted leaving the extracellular domain intact. This molecule had no effect on cell-cell adhesion, nor did it localize to cell-cell contact sites. We also found that the association of the endogenous cadherins with alpha- and beta-catenins and plakoglobin was not affected by the expression of cN390 delta, which also formed a complex with these molecules, suggesting that no competition occurred between the endogenous and exogenous cadherins for these cytoplasmic proteins. These and other additional results suggest that the nonfunctional cadherins whose intracellular domain is intact occupy the sites where the endogenous cadherins should localize, through interactions with the cytoskeleton, and inhibit the cadherin adhesion system.
Mol Biol Cell 1993 Jan
PMID:Disruption of epithelial cell-cell adhesion by exogenous expression of a mutated nonfunctional N-cadherin. 844 8

When overexpressed in Xenopus embryos, Xwnt-1, -3A, -8 and -8b define a functional class of Wnts (the Wnt-1 class) that promotes duplication of the embryonic axis, whereas Xwnt-5A, -4, and -11 define a distinct class (the Wnt-5A class) that alters morphogenetic movements (Du, S., S. Purcell, J. Christian, L. McGrew, and R. Moon. 1995. Mol. Cell. Biol. 15:2625-2634). Since come embryonic cells may be exposed to signals from both functional classes of Wnt during vertebrate development, this raises the question of how the signaling pathways of these classes of Wnts might interact. To address this issue, we coexpressed various Xwnts and components of the Wnt-1 class signaling pathway in developing Xenopus embryos. Members of the Xwnt-5A class antagonized the ability of ectopic Wnt-1 class to induce goosecoid expression and a secondary axis. Interestingly, the Wnt-5A class did not block goosecoid expression or axis induction in response to overexpression of cytoplasmic components of the Wnt-1 signaling pathway, beta-catenin or a kinase-dead gsk-3, or to the unrelated secreted factor, BVg1. The ability of the Wnt-5A class to block responses to the Wnt-1 class may involve decreases in cell adhesion, since ectopic expression of Xwnt-5A leads to decreased Ca2+-dependent cell adhesion and the activity of Xwnt-5A to block Wnt-1 class signals is mimicked by a dominant negative N-cadherin. These data underscore the importance of cell adhesion in modulating the responses of embryonic cells to signaling molecules and suggest that the Wnt-5A functional class of signaling factors can interact with the Wnt-1 class in an antagonistic manner.
 ...
PMID:Activities of the Wnt-1 class of secreted signaling factors are antagonized by the Wnt-5A class and by a dominant negative cadherin in early Xenopus development. 865 84

The neural cell adhesion molecule (NCAM) promotes axonal growth via a homophilic binding mechanism by acting both as a neuronal receptor and a substratum ligand. We have previously shown that the GPI-linked 120-kDa isoform of NCAM, which lacks a cytoplasmic domain, is effective at promoting neurite outgrowth as a cellular ligand. To test its ability to function as a neuronal receptor, we have transfected PC12 cells with a cDNA encoding human GPI-linked NCAM and tested clones displaying stable cell surface expression of this isoform for their ability to respond to NCAM in a cellular substratum. Although they continued to express endogenous transmembrane rat isoforms of NCAM (140 and 180 kDa), PC12 cells expressing the GPI-linked NCAM lost their ability to extend neurites in response to substratum associated NCAM. However, their outgrowth response to N-cadherin and other activators of axonal growth was undiminished. Removal of GPI-linked NCAM from the surface of these clones using phosphatidylinositol-specific phospholipase C (PIPLC) fully restored their responsiveness to NCAM, indicating that the inhibition was a direct consequence of cell surface expression of this "dominant negative" isoform of NCAM. We have previously shown that expression of transfected 140- and 180-kDa isoforms of human NCAM in PC12 cells does not result in a loss of the neurite outgrowth response to NCAM. However, we show that deletion of the cytoplasmic domain of the 140-kDa isoform has the same effect as expression of GPI-linked NCAM. We conclude that the cytoplasmic domain of NCAM is required for an appropriate neurite outgrowth response.
Mol Cell Neurosci 1995 Dec
PMID:NCAM requires a cytoplasmic domain to function as a neurite outgrowth-promoting neuronal receptor. 874 69

Regulation of cell adhesion and cell signaling by beta-catenin occurs through a mechanism likely involving the targeted degradation of the protein. Deletional analysis was used to generate a beta-catenin refractory to rapid turnover and to examine its effects on complexes containing either cadherin or the adenomatous polyposis coli (APC) protein. The results show that amino-terminal deletion of beta-catenin results in a protein with increased stability that acts in a dominant fashion with respect to wild-type beta-catenin. Constitutive expression in AtT20 cells of a beta-catenin lacking 89 N-terminal amino acids (deltaN89beta-catenin) resulted in severely reduced levels of the more labile wild-type beta-catenin. The mutant beta-catenin was expressed at endogenous levels but displaced the vast majority of wild-type beta-catenin associated with N-cadherin. The deltaN89beta-catenin accumulated on the APC protein to a level 10-fold over that of wild-type beta-catenin and recruited a kinase into the APC complex. The kinase was highly active toward APC in vitro and promoted a sodium dodecyl sulfate gel band shift that was also evident for endogenous APC from cells expressing the mutant beta-catenin. Unlike wild-type beta-catenin, which partitions solely as part of a high-molecular-weight complex, the deltaN89 mutant protein also fractionated as a stable monomer, indicating that it had escaped the requirement to associate with other proteins. That similar N-terminal mutants of beta-catenin have been implicated in cellular transformation suggests that their abnormal association with APC may, in part, be responsible for this phenotype.
Mol Cell Biol 1996 Aug
PMID:Deletion of an amino-terminal sequence beta-catenin in vivo and promotes hyperphosporylation of the adenomatous polyposis coli tumor suppressor protein. 875 7

A number of experimental paradigms have been used to demonstrate that NCAM, N-cadherin, and L1 stimulate axonal growth. The molecular basis of this response has been extensively studied and a range of agents that inhibit neurite outgrowth stimulated by the above CAMs, but not integrins, have now been identified. These studies pointed to the activation of a tyrosine kinase-PLCgamma cascade as being important for the neurite outgrowth responses stimulated by all three CAMs, and this was substantiated by the identification of agents that could activate the cascade and mimic the growth response. In this review we will suggest that the neurite growth response stimulated by these CAMs is mediated by activation of the fibroblast growth factor receptor (FGFR) in neurons and that this results in the recruitment and activation of PLCgamma via interactions of its SH2 domain with the activated receptor. In this context the key events downstream from activation of PLCgamma required for neurite growth appear to be the conversion of diacylglycerol (DAG) to arachidonic acid (AA) via DAG lipase activity, followed by an increased influx of calcium into the neurons. The evolutionary conservation of putative binding motifs between the above CAMs and the FGFR suggests that activation of the FGFR-PLCgamma cascade by the CAMs might involve a direct CAM-FGFR interaction. The identification of the binding motifs also allows for predictions to be made concerning whether other CAMs might directly interact with the FGFR.
Mol Cell Neurosci 1996
PMID:CAM-FGF receptor interactions: a model for axonal growth. 891 27

During the early stages of development various cell adhesion molecules (CAMs) and fibroblast growth factor receptors (FGFR) are expressed throughout the retinal neuroepithelium. The ability of retinal ganglion cells to project their axons to the optic fissure depends, in part, on cell-cell interactions mediated by cell adhesion molecules. In the present study we show that the ability of the firstborn rat retinal ganglion cells to extend axons in vitro can be stimulated by NCAM and L1, but not N-cadherin. Both CAM responses can be fully inhibited by antibodies that block neuronal fibroblast growth factor receptor function and by agents that block defined steps in the FGFR signal transduction cascade. When added to living E13.5 rat retinal whole-mount preparations the same agents induced errors in the orderly establishment of young axon patterns in the retinal periphery and caused axons in the retinal center to defasciculate. These results suggest that the activation of the fibroblast growth factor receptor signal cascade not only promotes survival and proliferation of various cell types but can also mediate intraretinal axon guidance.
Mol Cell Neurosci 1996
PMID:Fibroblast growth factor receptor function is required for the orderly projection of ganglion cell axons in the developing mammalian retina. 891 29


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