Palmitoylation of caveolin-1 at a single site (Cys-156) controls its coupling to the c-Src tyrosine kinase: targeting of dually acylated molecules (GPI-linked, transmembrane, or cytoplasmic) to caveolae effectively uncouples c-Src and caveolin-1 (TYR-14).
Caveolin-1 was initially identified as a phosphoprotein in Rous sarcoma virus-transformed cells. Previous studies have shown that caveolin-1 is phosphorylated on tyrosine 14 by c-Src and that lipid modification of c-Src is required for this phosphorylation event to occur in vivo. Phosphocaveolin-1 (Tyr(P)-14) localizes within caveolae near focal adhesions and, through its interaction with Grb7, augments anchorage-independent growth and epidermal growth factor-stimulated cell migration. However, the cellular factors that govern the coupling of caveolin-1 to the c-Src tyrosine kinase remain largely unknown. Here, we show that palmitoylation of caveolin-1 at a single site (Cys-156) is required for coupling caveolin-1 to the c-Src tyrosine kinase. Furthermore, upon evaluating a battery of nonreceptor and receptor tyrosine kinases, we demonstrate that the tyrosine phosphorylation of caveolin-1 by c-Src is a highly selective event. We show that Src-induced tyrosine phosphorylation of caveolin-1 can be inhibited or uncoupled by targeting dually acylated proteins (namely carcinoembryonic antigen (CEA), CD36, and the NH(2)-terminal domain of Galpha(i1)) to the exoplasmic, transmembrane, and cytoplasmic regions of the caveolae membrane, respectively. Conversely, when these proteins are not properly targeted or lipid-modified, the ability of c-Src to phosphorylate caveolin-1 remains unaffected. In addition, when purified caveolae preparations are preincubated with a myristoylated peptide derived from the extreme N terminus of c-Src, the tyrosine phosphorylation of caveolin-1 is abrogated; the same peptide lacking myristoylation has no inhibitory activity. However, an analogous myristoylated peptide derived from c-Yes also has no inhibitory activity. Thus, the inhibitory effects of the myristoylated c-Src peptide are both myristoylation-dependent and sequence-specific. Finally, we investigated whether phosphocaveolin-1 (Tyr(P)-14) interacts with the Src homology 2 and/or phosphotyrosine binding domains of Grb7, the only characterized downstream mediator of its function. Taken together, our data identify a series of novel lipid-lipid-based interactions as important regulatory factors for coupling caveolin-1 to the c-Src tyrosine kinase in vivo.
Lee
H
H
Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Woodman
S E
SE
Engelman
J A
JA
Volonté
D
D
Galbiati
F
F
Kaufman
H L
HL
Lublin
D M
DM
Lisanti
M P
MP
D000818:Animals; D018955:CD36 Antigens / Q000378:metabolism; D019556:COS Cells; D000081247:CSK Tyrosine-Protein Kinase; D051242:Caveolin 1; D022461:Caveolins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D019814:Myristic Acid / Q000378:metabolism; D019308:Palmitic Acid / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains; D019061:src-Family Kinases
D018955:CD36 Antigens; D051242:Caveolin 1; D022461:Caveolins; D017261:Glycosylphosphatidylinositols; D019814:Myristic Acid; D019308:Palmitic Acid; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D020962:Heterotrimeric GTP-Binding Proteins