RGS proteins: more than just GAPs for heterotrimeric G proteins

Members of the newly described RGS family of proteins have a common RGS domain that contains GTPase-activating activity for many G alpha subunits of heterotrimeric G proteins. Their ability to dampen siganlling via G alpha(i)-, G alpha(q)- and G alpha(12/13)-coupled pathways makes them crucial players in mediating the multitude of cellular processes controlled by heterotrimeric G proteins. Some RGS proteins also contain additional motifs that link them to other signalling networks, where they constitute effector-type molecules. This review summarizes recent findings on RGS proteins, especially those that implicate RGS proteins in more than just enhancing the GTPase activity of their G alpha subunit targets.