Differential expression of the microspike-associated protein moesin in human tissues.

The protein moesin is a member of a gene family consisting of talin, ezrin, radixin, protein 4.1., and merlin. Proteins of this family are associated 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 carcinoma, mesothelioma and lymphoid origin. Moesin was metabolically labeled by [32P]orthophosphate and reacted with an antibody against phosphotyrosine. Moesin also contains carbohydrate residues as demonstrated by immunostainings of digoxigenin-labeled sugar residues. The antibody 38/87 in comparison to antisera against radixin and ezrin was applied in immunohistological stainings on various human tissues. As a prominent feature, moesin as strongly expressed in endothelium of vessels in contrast to radixin and ezrin. Moesin but not radixin was observed in T and B lymphocytes. Further, moesin was expressed in basal layers of squamous epithelium and glandular ducts and lymphocytes. Subcellular expression of moesin was studied on cultured human endothelial cells of umbilical cord veins and the mesothelioma cell line CH3LC by confocal laser scanning microscopy. In subconfluently growing cells moesin showed a characteristic expression on extending microspikes at the basal cell level. Moesin was coexpressed with actin in the cortical cytoskeleton and on microspikes but not in stress fibers. The differential cellular expression of moesin and its pronounced occurrence on microspikes of growing cells support the possibility that moesin is a protein involved in plasma membrane-cytoskeleton interactions in specialized tissues.