Abstract
The G protein signaling cascade is a key player in cell signaling. Cascade activation leads to a redistribution of its members in various cellular compartments. These changes are likely related to the "second wave" of signaling from endosomes. Here, we set out to determine whether G(s) signaling cascade members expressed at very low levels exhibit altered mobility and localize in clathrin-coated structures (CCSs) or caveolae upon activation by β(2) -adrenergic receptors (β(2) AR). Activated β(2) AR showed decreased mobility and sustained accumulation in CCSs but not in caveolae. Arrestin 3 translocated to the plasma membrane after β(2) AR activation and showed very low mobility and pronounced accumulation in CCSs. In contrast, Gα(s) and Gγ(2) exhibited a modest reduction in mobility but no detectable accumulation in or exclusion from CCSs or caveolae. The effector adenylyl cyclase 5 (AC5) showed a slight mobility increase upon β(2) AR stimulation, no redistribution to CCSs, and weak activation-independent accumulation in caveolae. Our findings show an overall decrease in the mobility of most activated G(s) signaling cascade members and confirm that β(2) AR and arrestin 3 accumulate in CCSs, while Gα(s) , Gγ(2) and AC5 can transiently enter CCSs and caveolae but do not accumulate in and are not excluded from these domains.