OLIGOMERIZATION OF VIP21-CAVEOLIN IN-VITRO IS STABILIZED BY LONG-CHAIN FATTY ACYLATION OR CHOLESTEROL

VIP21-caveolin is one of the components which form the cytoplasmic sur face of caveolae, In vivo, this integral membrane protein is found in homo-oligomers with molecular masses of approximately 200, 400 and 600 kDa, These oligomers are also formed by the addition of cytosol to th e in vitro synthesized and membrane inserted VIP21-caveolin, Here we s how that long chain fatty acyl coenzyme A esters can completely substi tute for cytosol in inducing 200 kDa and 400 kDa complexes, whereas 25 -hydroxy-cholesterol can produce the 200 kDa oligomer. In order to und erstand whether acylation of VIP21-caveolin itself is a Prerequisite f or oligomerization, we studied a mutant protein lacking all three cyst eines, When analyzed by velocity sucrose gradient centrifugation in th e presence of the non-ionic detergent octylglucoside, both palmitoylat ed and non-palmitoylated VIP21-caveolin formed oligomers that were ind istinguishable. However, only the oligomers of the non-palmitoylated p rotein are disrupted when analyzed by SDS-PAGE without boiling, These data suggest that the protein domains of VIP21-caveolin are the primar y determinants of oligomerization, but that palmitoylation of cysteine residues can increase the stability of the oligomers.