CAVEOLIN-1 AND CAVEOLIN-2 IN THE EXOCYTIC PATHWAY OF MDCK CELLS

We have studied the biosynthesis and transport of the endogenous caveo lins in MDCK cells. We show that in addition to homooligomers of caveo lin-1, heterooligomeric complexes of caveolin-1 and -2 are formed in t he ER, The oligomers become larger, increasingly detergent insoluble, and phosphorylated on caveolin-2 during transport to the cell surface. In the TGN caveolin-1/-2 heterooligomers are sorted into basolateral vesicles, whereas larger caveolin-1 homooligomers are targeted to the apical side. Caveolin-1 is present on both the apical and basolateral plasma membrane, whereas caveolin-2 is enriched on the basolateral sur face where caveolae are present. This suggests that caveolin-1 and -2 heterooligomers are involved in caveolar biogenesis in the basolateral plasma membrane. Anti-caveolin-1 antibodies inhibit the apical delive ry of influenza virus hemagglutinin without affecting basolateral tran sport of vesicular stomatitis virus G protein. Thus, we suggest that c aveolin-1 homooligomers play a role in apical transport.