RGS proteins act as GTPase  activating proteins or as effector antagonists for certain Gα subunits of heterotrimeric G-proteins, thus attenuating signaling through many G-protein-coupled receptors. A recent explosion of studies has revealed that RGS proteins interact with a variety of signaling molecules other than Gα subunits and that they are subjected to complex regulation. RGS proteins mediate cross talk between signaling pathways and fine-tune diverse cellular processes such as phototransduction, regulation of ion channels, chemotaxis, cardiac hypertrophic reponses, cellular proliferation, and cytoskeletal responses.