A Novel Kind of G Protein Heterodimer: The Gβ5-RGS Complex

The fifth member of the G protein g the subunit family, G g 5, has been shown to bind exclusively to a subfamily of regulators of G protein signaling (RGS) including RGS6, RGS7, RGS9, and RGS11. This interaction occurs through a G protein gamma-like (GGL) domain present in members of this RGS subfamily and is the only reported instance in which a G g subunit is not bound to a G n subunit. The G g 5-RGS interaction has been demonstrated both in vitro and in vivo and has been shown to stabilize the dimer against proteolytic degradation. GTPase activating protein (GAP) assays suggest that G g 5-RGS7 acts specifically on G f o, however in cell-based assays it also inhibited G f i- and G f q-mediated signaling. The role of the dimer in signaling and the function of G g 5 moiety within the complex are poorly understood. This review summarizes the information about the assembly and function of G g 5-RGS dimers, as well as their posttranslational modifications and localization.