CAVEOLIN IS PALMITOYLATED ON MULTIPLE CYSTEINE RESIDUES - PALMITOYLATION IS NOT NECESSARY FOR LOCALIZATION OF CAVEOLIN TO CAVEOLAE

Caveolae are subdomains of the plasma membrane which concentrate chole sterol, glycosphingolipids, and glycosylphosphatidylinositol-linked pr oteins. It has recently been demonstrated that specific members of the Src family of protein tyrosine kinases require palmitoylation of NH2- terminal cysteine residues to localize in caveolae. Here we report tha t caveolin, an integral membrane protein which forms part of the coat of caveolae, also incorporates palmitate through linkage to cysteine r esidues. Caveolin contains only three cysteine residues which are all located on the COOH-terminal side of the hydrophobic transmembrane reg ion. Immunofluorescent staining of cells transfected with caveolin ind icated that, like the NH2 terminus, this COOH-terminal region is locat ed on the cytoplasmic side of the plasma membrane. Studies of cysteine substitution mutants showed that all three cysteines are capable of i ncorporating palmitate and that the juxtamembrane Cys(133) residue is the predominant site of palmitoylation. Simultaneous mutation of all t hree cysteine residues in caveolin resulted in the loss of ability to incorporate palmitate; however, this did not affect localization of th e protein. Thus, palmitoylation of cysteine residues in nonmembrane sp anning Src family protein tyrosine kinases has different consequences than in the transmembrane protein caveolin.