OLIGOMERIC STRUCTURE OF CAVEOLIN - IMPLICATIONS FOR CAVEOLAE MEMBRANEORGANIZATION

A 22-kDa protein, caveolin, is localized to the cytoplasmic surface of plasma membrane specializations called caveolae, We have proposed tha t caveolin may function as a scaffolding protein to organize and conce ntrate signaling molecules within caveolae. Here, we show that caveoli n interacts with itself to form homooligomers. Electron microscopic vi sualization of these purified caveolin homooligomers demonstrates that they appear as individual spherical particles. By using recombinant e xpression of caveolin as a glutathione S-transferase fusion protein, w e have defined a region of caveolin's cytoplasmic N-terminal domain th at mediates these caveolin-caveolin interactions. We suggest that cave olin homooligomers may function to concentrate caveolin-interacting mo lecules within caveolae. In this regard, it may be useful to think of caveolin hommoligomers as ''fishing lures'' with multiple ''hooks'' or attachment sites for caveolin-interacting molecules.