The α subunit of the heterotrimeric G(s) protein that couples the β- adrenergic receptor to adenylyl cyclase undergoes post-translational palmitoylation. We examined the dynamics of this modification of α(s) by metabolic labeling of COS and S49 lymphoma cells under different conditions. The endogenous α(s) proteins were immunoprecipitated 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 [3H]palmitate or [35S]methionine showed that for α(s) the palmitate turnover (t( 1/2 ) ≃ 50 min) was significantly faster than the protein degradation. Treatment of cells with 10 μM isoproterenol, a β-adrenergic receptor agonist, in the presence of [3H]palmitate led to a rapid 4-10-fold increase in the palmitoylation of α(s). This increase in palmitoylation was concentration-dependent (EC50 ≃ 0.9 μM) and blocked by the antagonist propranolol. The mutant α(s) proteins in the unc and H21a S49 cell lines did not show an increase in [3H]palmitate incorporation with isoproterenol treatment. Cholera toxin treatment of COS cells increased the [3H]palmitate incorporation into the α(s) subunits. These data indicate that palmitoylation of the α(s) subunit is dynamic and regulated by activation of the α(s) subunit.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of Biological Chemistry|
|State||Published - 1993|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology