DIFFERENTIAL EXPRESSION OF THE MICROSPIKE-ASSOCIATED PROTEIN MOESIN IN HUMAN TISSUES

The protein moesin is a member of a gene family consisting of talin, e zrin, radixin, protein 4.1., and merlin, Proteins of this family are a ssociated to the submenbranous cytoskeleton. Using monoclonal antibody 38/87 directed against moesin in immunochemical analysis, the 78 kDa moesin protein was demonstrated in endothelial cells and in cells of c arcinoma, mesothelioma and lymphoid origin, Moesin was metabolically l abeled by [P-32]orthophosphate and reacted with an antibody against ph osphotyrosine, Moesin also contains carbohydrate residues as demonstra ted by immunostainings of digoxigenin-labeled sugar residues, The anti body 38/87 in comparison to antisera against radixin and ezrin was app lied in immunohistological stainings on various human tissues, As a pr ominent feature, moesin was strongly expressed in endothelium of vesse ls in contrast to radixin and ezrin. Moesin but not radixin was observ ed in T and B lymphocytes. Further, moesin,vas expressed in basal laye rs of squamous epithelium and glandular ducts and lymphocytes. Subcell ular expression of moesin was studied on cultured human endothelial ce lls of umbilical cord veins and the mesothelioma cell line CH3LC by co nfocal laser scanning microscopy. In subconfluently growing cells moes in showed a characteristic expression on extending microspikes at the basal cell level. Moesin was coexpressed with actin in the cortical cy toskeleton and on microspikes but not in stress fibers. The differenti al cellular expression of moesin and its pronounced occurrence on micr ospikes of growing cells support the possibility that moesin is a prot ein involved in plasma membrane cytoskeleton interactions in specializ ed tissues,