Abstract

Regulator of G protein signaling (RGS) proteins modulate G protein signaling by acting as GTPase-activating proteins for G protein α-subunits. RGS7 belongs to a subfamily of RGS proteins that exist as dimers with the G protein β₅-subunit. In this report, we addressed the mechanisms of plasma membrane localization of β₅RGS7. When expressed in human embryonic kidney 293 cells, β₅RGS7 was found to be cytoplasmic and soluble. Expression of α_o promoted a strong redistribution of β₅RGS7 to the plasma membrane. Expression of α_q, however, failed to affect the subcellular localization of β₅RGS7. The constitutively active mutant α_oR179C, like wild-type α_o, strongly recruited β₅RGS7 to plasma membranes; however, inactive α_oG204A, RGS-insensitive α_oG184S, and lipidation-deficient α_oG2A were all defective in the ability to promote plasma membrane localization of β₅RGS7. In addition, palmitoylation of RGS7 was demonstrated, and palmitoylation required expression of α_o or α_oR179C. To examine potential palmitoylation sites of RGS7, several cysteines were substituted with serines. β₅RGS7C133S failed to localize to plasma membranes when coexpressed with α_o, suggesting cysteine 133 of RGS7 as a putative palmitoylation site. Finally, deletion of amino acids 76 to 128 of RGS7, which includes part of the disheveled, EGL-10, pleckstrin (DEP) domain, prevented α_o-mediated plasma membrane recruitment of β₅RGS7. These findings are the first to demonstrate Gα-regulated plasma membrane localization and palmitoylation of β₅RGS7 and suggest that membrane targeting of β₅RGS7 is a complex process requiring at least RGS domain-mediated interaction with α_o and RGS7 palmitoylation.