05-916 Sigma-AldrichAnti-P-Cadherin Antibody, clone 6A9

Adherens junctions consist of transmembrane cadherins, which interact intracellularly with p120ctn, beta-catenin and alpha-catenin. p120ctn is known to regulate cell-cell adhesion by increasing cadherin stability, but the effects of other adherens junction components on cell-cell adhesion have not been compared with that of p120ctn.We show that depletion of p120ctn by small interfering RNA (siRNA) in DU145 prostate cancer and MCF10A breast epithelial cells reduces the expression levels of the adherens junction proteins, E-cadherin, P-cadherin, beta-catenin and alpha-catenin, and induces loss of cell-cell adhesion. p120ctn-depleted cells also have increased migration speed and invasion, which correlates with increased Rap1 but not Rac1 or RhoA activity. Downregulation of P-cadherin, beta-catenin and alpha-catenin but not E-cadherin induces a loss of cell-cell adhesion, increased migration and enhanced invasion similar to p120ctn depletion. However, only p120ctn depletion leads to a decrease in the levels of other adherens junction proteins.Our data indicate that P-cadherin but not E-cadherin is important for maintaining adherens junctions in DU145 and MCF10A cells, and that depletion of any of the cadherin-associated proteins, p120ctn, beta-catenin or alpha-catenin, is sufficient to disrupt adherens junctions in DU145 cells and increase migration and cancer cell invasion.

Surface marker expression forms the basis for characterization and isolation of human embryonic stem cells (hESCs). Currently, there are few well-defined protein epitopes that definitively mark hESCs. Here we combine immunotranscriptional profiling of hESC lines with membrane-polysome translation state array analysis (TSAA) to determine the full set of genes encoding potential hESC surface marker proteins. Three independently isolated hESC lines (HES2, H9, and MEL1) grown under feeder and feeder-free conditions were sorted into subpopulations by fluorescence-activated cell sorting based on coimmunoreactivity to the hESC surface markers GCTM-2 and CD9. Colony-forming assays confirmed that cells displaying high coimmunoreactivity to GCTM-2 and CD9 constitute an enriched subpopulation displaying multiple stem cell properties. Following microarray profiling, 820 genes were identified that were common to the GCTM-2(high)/CD9(high) stem cell-like subpopulation. Membrane-polysome TSAA analysis of hESCs identified 1,492 mRNAs encoding actively translated plasma membrane and secreted proteins. Combining these data sets, 88 genes encode proteins that mark the pluripotent subpopulation, of which only four had been previously reported. Cell surface immunoreactivity was confirmed for two of these markers: TACSTD1/EPCAM and CDH3/P-Cadherin, with antibodies for EPCAM able to enrich for pluripotent hESCs. This comprehensive listing of both hESCs and spontaneous differentiation-associated transcripts and survey of translated membrane-bound and secreted proteins provides a valuable resource for future study into the role of the extracellular environment in both the maintenance of pluripotency and directed differentiation.

Cadherins are a large family of single-pass transmembrane proteins principally involved in Ca2+-dependent homotypic cell adhesion. The cadherin molecules comprise three domains, the intracellular domain, the transmembrane domain and the extracellular domain, and form large complexes with a vast array of binding partners (including cadherin molecules of the same type in homophilic interactions and cellular protein catenins), orchestrating biologically essential extracellular and intracellular signalling processes. While current, contrasting models for classic cadherin homophilic interaction involve varying numbers of specific repeats found in the extracellular domain, the structure of the domain itself clearly remains the main determinant of cell stability and binding specificity. Through intracellular interactions, cadherin enhances its adhesive properties binding the cytoskeleton via cytoplasmic associated factors alpha- catenin, beta-catenin and p120ctn. Recent structural studies on classic cadherins and these catenin molecules have provided new insight into the essential mechanisms underlying cadherin-mediated cell interaction and catenin-mediated cellular signalling. Remarkable structural diversity has been observed in beta-catenin recognition of other cellular factors including APC, Tcf and ICAT, proteins that contribute to or compete with cadherin/catenin functioning.

Cadherins are glycoproteins that are responsible for homophilic, Ca2+-dependent cell-cell adhesion and play crucial roles in many cellular adhesion processes ranging from embryogenesis to the formation of neuronal circuits in the central nervous system. Many different experimental approaches have been used to unravel the molecular basis for cadherin-mediated adhesion. In particular, several high-resolution structures have provided models for cadherin-cadherin interactions that are illuminative in many respects yet contradictory in others. This review gives an overview of the structural studies of cadherins over the past decade while focusing on recent developments that reconcile some of the earlier findings.

Breast cancers often show reduced expression of the transmembrane cell-cell adhesion protein, E-cadherin. In addition, approximately half of breast carcinomas express P-cadherin, which correlates with poor survival. A large fragment of the E-cadherin extracellular domain can be detected in serum, and it has been proposed that an increase in serum E-cadherin can denote the presence of a tumor. In this study, we tested the possibility that serum E- or P-cadherin levels might be useful diagnostic or prognostic indicators in breast cancer. However, we found no indication that the level of serum E-cadherin correlated with the presence of breast cancer. In addition, although we successfully detected a fragment of P-cadherin in serum, we found that its level was considerably lower than that of E-cadherin and did not correlate with the presence of P-cadherin-positive breast cancer.

The cadherin/catenin complex mediates Ca2+-dependent cell-cell interactions that are essential for normal developmental processes. It has been proposed that sorting of cells during embryonic development is due, at least in part, to expression of different cadherin family members or to expression of differing levels of a single family member. Expression of dominant-negative cadherins has been used experimentally to decrease cell-cell interactions in whole organisms and in cultured cells. In this study, we elucidated the mechanism of action of extracellular domain-deleted dominant-negative cadherin, showing that it is not cadherin isotype-specific, and that it must be membrane-associated but the orientation within the membrane does not matter. In addition, membrane-targeted cytoplasmic domain cadherin with the catenin-binding domain deleted does not function as a dominant-negative cadherin. Expression of extracellular domain-deleted dominant-negative cadherin results in down-regulation of endogenous cadherins which presumably contributes to the non-adhesive phenotype.