Both G_s and G_q are palmitoylated and both can move from a crude membrane fraction to a soluble fraction in response to stimulation with agonists. This response may be mediated through depalmitoylation. Previous studies have not demonstrated that endogenous guanine nucleotide-binding regulatory protein (G protein) -subunits are released directly from the plasma membrane. We have examined the effect of agonist stimulation on the location of G_q/11 immunoreactivity in Madin-Darby canine kidney (MDCK) cells. Bradykinin (BK; 0.1 µM) caused G_q/11, but not G_i, to rapidly translocate from purified plasma membranes to the supernatant. AlF and GTP also caused translocation of G_q/11 immunoreactivity from purified plasma membranes. BK caused translocation of G_q/11 immunoreactivity in intact cells from the basal and lateral plasma membranes to an intracellular compartment as assessed by confocal microscopy. Thus G_q/11 is released directly from the plasma membrane to an intracellular location in response to activation by an agonist and direct activation of G proteins. G protein translocation may be a mechanism for desensitization or for signaling specificity.

G protein; bradykinin; palmitoylation