Biology and functions of the RGS9 isoforms.

Two splice isoforms of the ninth member of the regulator of G protein signaling (RGS) protein family are expressed in the nervous system, where they are engaged in such diverse functions as vision and behavior. RGS9-1 regulates phototransduction in rods and cones, while RGS9-2 regulates dopamine and opioid signaling in the basal ganglia. The main goal of this review is to illustrate how these functions are fulfilled through the interplay between the intrinsic molecular properties of RGS9 isoforms and their interactions with several key protein partners in the cells in which they are expressed.