ANALYSIS OF MOLECULAR DOMAINS OF EPITOPE-TAGGED MERLIN ISOFORMS IN COS-7 CELLS AND PRIMARY RAT SCHWANN-CELLS

The Neurofibromatosis 2 gene product, merlin, has striking similarity to ezrin, radixin, and moesin (ERM), members of the protein 4.1 family which have been demonstrated to connect proteins in the plasma membra ne to the cytoskeletal components. The recent localization of merlin t o the motile regions in cultured cells such as membrane ruffles furthe r supports the notion that merlin represents a new class of tumor supp ressors. Here we describe the localization of full-length and truncate d polypeptides of merlin expressed as Flag-tagged proteins in transfec ted cells. Similar to endogenous merlin, the epitope-tagged full-lengt h merlin localizes to the membrane ruffles in transfected Cos-7 cells and rat Schwann cells. In addition, the overexpressed merlin localizes to other actin-rich cortical structures, such as microvilli and filop odia. The amino-terminal half of merlin is seen dispersed throughout t he cells and in membrane ruffles. Compared to the amino-terminal half of merlin, its carboxyterminal half localizes more distinctly to membr ane ruffles. The full-length and the carboxy-terminal portion of merli n co-localize with F-actin at the membrane ruffles. However, distinct from the ERM proteins, the carboxy-terminal-truncated merlin and F-act in do not co-localize with each other at the stress fibers. Our result s suggest that both the amino-and the carboxyterminal domains of merli n contribute to its membrane ruffle localization. (C) 1998 Academic Pr ess.