Caveolae represent a prominent plasma membrane 'specialization' in many cell types. Although they were first identified in transmission electron micrographs 40 years ago, their function has remained uncertain. Two proposed functions are: I) the transcytosis of both large and small molecules across capillary endothelial cells; and 2) the potocytosis of concentrating small molecules in caveolae for translocation to the cytoplasm using GPI-linked protein. Over the last two years, Lisanti and colleagues have made rapid progress in molecular analysis of caveolae using caveolin as a marker for the organelle, and proposed a 'third' caveolar function-transmembrane signaling. Using caveolin as a molecular probe, this proposal focuses on using molecular biological approaches, such as protein micro- sequencing, a novel expression cloning strategy, and recombinant expression of caveolin as a bacterial fusion protein to: (a) identify caveolin-interacting signaling molecules; (b) purify caveolin- interacting proteins from total cellular extracts of tissues; (c) clone molecules that interact directly with caveolin. The information from this research will provide insight into the normal function of caveolae, which contain many known molecules that have been implicated in cellular transformation and oncogenesis. Therefore, these studies will contribute to an understanding of not only the function of caveolae in normal cells, but also the molecular basis of cell transformation.
