INCREASED PALMITOYLATION OF THE G(S) PROTEIN-ALPHA SUBUNIT AFTER ACTIVATION BY THE BETA-ADRENERGIC-RECEPTOR OR CHOLERA-TOXIN

The alpha subunit of the heterotrimeric G(s) protein that couples the beta-adrenergic receptor to adenylyl cyclase undergoes post-translatio nal palmitoylation. We examined the dynamics of this modification of a lpha(s) by metabolic labeling of COS and S49 lymphoma cells under diff erent conditions. The endogenous alpha(s) proteins were immunoprecipit ated with a peptide-specific antibody, separated by SDS-polyacrylamide gel electrophoresis, and analyzed by fluorography and densitometry. A pulse-chase study of COS cells incubated with [H-3]palmitate or [S-35 ]methionine showed that for alpha(s) the palmitate turnover (t1/2 almo st-equal-to 50 min) was significantly faster than the protein degradat ion. Treatment of cells with 10 muM isoproterenol, a beta-adrenergic r eceptor agonist, in the presence of [H-3]palmitate led to a rapid 4-10 -fold increase in the palmitoylation of alpha(s). This increase in pal mitoylation was concentration-dependent (EC50 almost-equal-to 0.9 muM) and blocked by the antagonist propranolol. The mutant alpha(s) protei ns in the unc and H21a S49 cell lines did not show an increase in [H-3 ]palmitate incorporation with isoproterenol treatment. Cholera toxin t reatment of COS cells increased the [H-3]palmitate incorporation into the alpha(s) subunits. These data indicate that palmitoylation of the alpha(s) subunit is dynamic and regulated by activation of the alpha(s ) subunit.