Identification of gelsolin as an actin regulatory component in a Triton insoluble law density fraction (raft) of newborn bovine brain

A membrane microdomain enriched in cholesterol and glycosphingolipids, or s o called 'raft' region, was found to contain many signal transducing protei ns such as GPI-anchored cell adhesion molecules, trimeric G proteins, and p rotein tyrosine kinases. In previous studies, we showed that the raft regio n obtained from rat brain contains two cytoskeletal proteins, tubulin and a ctin, as the major components in addition to these signal transducing prote ins. In this study, to know the biochemical mechanisms regulating the cytos keletal organization in this region, actin regulatory activities in raft we re surveyed. We found the presence of a Ca2+-dependent actin nucleation pro moting activity in raft. The solubilization and column fractionation of thi s activity combined with western blotting and immunoprecipitation showed th at gelsolin is one of the actin regulatory proteins in raft. (C) 2000 Publi shed by Elsevier Science Ireland Ltd and the Japan Neuroscience Society. Al l rights reserved.