Gβγ isoforms selectively rescue plasma membrane localization and palmitoylation of mutant Gαs and Gαq

Mutation of G alpha (q) or G alpha (s) N-terminal contact sites for G beta gamma resulted in alpha subunits that failed to localize at the plasma membrane or undergo palmitoylation when expressed in HEK293 cells. We now show that overexpression of specific py subunits can recover plasma membrane localization and palmitoylation of the beta gamma -binding-deficient mutants of alpha (s) or alpha (q). Thus, the beta gamma -binding-defective alpha is completely dependent on co-expression of exogenous beta gamma for proper membrane localization. In this report, we examined the ability of beta (1-5) in combination with gamma (2) or gamma (3) to promote proper localization and palmitoylation of mutant alpha (s) or alpha (q). Immunofluorescence localization, cellular fractionation, and palmitate labeling revealed distinct subtype-specific differences in beta gamma interactions with alpha subunits. These studies demonstrate that 1) alpha and beta gamma reciprocally promote the plasma membrane targeting of the other subunit; 2) beta (5), when coexpressed with gamma (2) or gamma (3), fails to localize to the plasma membrane or promote plasma membrane localization of mutant alpha (s) or alpha (q); 3) beta (3) is deficient in promoting plasma membrane localization of mutant alpha (s) and alpha (q), whereas beta (4) is deficient in promoting plasma membrane localization of mutant alpha (q); 4) both palmitoylation and interactions with beta gamma are required for plasma membrane localization of alpha.