Potent and selective inhibition of angiotensin AT1 receptor signaling by RGS2: Roles of its N-terminal domain

Abstract Emerging evidence indicates that R4/B subfamily RGS (regulator of G protein signaling) proteins play roles in functional regulation in the cardiovascular system. In this study, we compared effects of three R4/B subfamily proteins, RGS2, RGS4 and RGS5 on angiotensin AT1 receptor signaling, and investigated roles of the N-terminus of RGS2. In HEK293T cells expressing AT1 receptor stably, intracellular Ca 2+ responses induced by angiotensin II were much more strongly attenuated by RGS2 than by RGS4 and RGS5. N-terminally deleted RGS2 proteins lost this potent inhibitory effect. Replacement of the N-terminal residues 1–71 of RGS2 with the corresponding residues (1–51) of RGS5 decreased significantly the inhibitory effect. On the other hand, replacement of the residues 1–51 of RGS5 with the residues 1–71 of RGS2 increased the inhibitory effect dramatically. Furthermore, we investigated functional contribution of N-terminal subdomains of RGS2, namely, an N-terminal region (residues 16–55) with an amphipathic α helix domain (the subdomain N1), a probable non-specific membrane-targeting subdomain, and another region (residues 56–71) between the α helix and the RGS box (the subdomain N2), a probable GPCR-recognizing subdomain. RGS2 chimera proteins with the residues 1–33 or 34–52 of RGS5 showed weak inhibitory activity, and either of RGS5 chimera proteins with residues 1–55 or 56–71 of RGS2 showed strong inhibitory effects on AT1 receptor signaling. The present study indicates the essential roles of both N-terminal subdomains for the potent inhibitory activity of RGS2 on AT1 receptor signaling.