Down-regulates signaling from heterotrimeric G-proteins by increasing the GTPase activity of the alpha subunits, thereby driving them into their inactive GDP-bound form. Down-regulates G-protein-mediated release of inositol phosphates and activation of MAP kinases. Binds EFNB1 and EFNB2. Binds the GNB1-GNG2 heterodimer (By similarity). Binds ESR1. Long isoforms are cytoplasmic and associated with the plasma membrane. Short isoforms are nuclear. Detected in kidney, uterus, ovary, heart, brain, spleen, lung and testis. Phosphorylated by cyclic GMP-dependent protein kinase. ISGylated.