Search

Melanoma cell adhesion molecule (MCAM), an adhesion molecule belonging to the Ig superfamily, is an endothelial marker and is expressed in different epithelia. MCAM is expressed as two isoforms differing by their cytoplasmic domain: MCAM-l and MCAM-s (long and short). In order to identify the respective role of each MCAM isoform, we analyzed MCAM isoform targeting in polarized epithelial Madin-Darby canine kidney (MDCK) cells using MCAM-GFP chimeras. Confocal microscopy revealed that MCAM-s and MCAM-l were addressed to the apical and basolateral membranes, respectively. Transfection of MCAM-l mutants established that a single dileucine motif (41-42) of the cytoplasmic domain was required for MCAM-l basolateral targeting in MDCK cells. Although double labelling experiments showed that MCAM-l is not a component of adherens junctions and focal adhesions, its expression on basolateral membranes suggests that MCAM-l is involved in epithelium insuring.

The physiological role of the prion protein is largely unknown. Here, clustering of prion at the surface of GT1-7 cells was observed upon anti-prion antibody treatments. This clustering was associated with a rapid and transient phosphorylation of the mitogen activated protein kinases (MAPKs) extracellular receptor kinases 1 and 2 (ERK1/2), and also of the microtubule-destabilizing protein stathmin at serine 16. The specificity of this antibody-mediated activation was ascertained by its inhibition by prion small interfering RNA. The phosphorylation of ERK1/2 but not that of stathmin was abolished by the MAPK/ERK kinase 1 inhibitor U0126, whereas both signaling pathways were blocked by the specific inhibitor of the epidermal growth factor receptor AG1478, suggesting the likely recruitment of this receptor upon prion clustering., (Copyright 2004 Federation of European Biochemical Societies)

A synthetic HAV-containing decapeptide homologous to the amino acid sequence 44R-Q53 in rat extracellular superoxide dismutase B affects cadherin-dependent cell aggregation. Cell lines, some of them transfected, expressing different types of cadherins were tested using in vitro cell aggregation and cell dissociation assays. A concentration-dependent inhibition of aggregation by the EC-SOD-derived HAV-containing peptide was detected only in N-cadherin expressing cells. These results suggest the localisation and possible protective role of EC-SOD B for cells expressing N-cadherin.