CAVEOLAE, TRANSMEMBRANE SIGNALING AND CELLULAR-TRANSFORMATION

Caveolae are similar to 50-100 nm membrane micro-invaginations associa ted with the plasma membrane of a wide variety of cells. Although they were first identified in transmission electron micrographs similar to 40 years ago, their exact function(s) has remained controversial. Two well-established functions include: (1) the transcytosis of both larg e and small molecules across capillary endothelial cells and (2) the u tilization of GPI-linked proteins to concentrate small molecules in ca veolae for translocation to the cytoplasm (termed potocytosis). Recent ly, interest in a 'third' proposed caveolar function, namely transmemb rane signalling, has been revived by the identification of caveolin - a transformation-dependent v-Src substrate and caveolar marker protein - and the isolation of caveolin-rich membrane domains from cultured c ells. Here we will discuss existing evidence that suggests a role for caveolae in signalling events.