Functional interaction of regulator of G protein signaling-2 with melanin-concentrating hormone receptor 1.

Melanin-concentrating hormone receptor 1 (MCHR1) is a G protein-coupled receptor (GPCR) highly expressed in the central nervous system. MCHR1 mediates many physiological functions including energy homeostasis and emotional processing. By acting as GTPase-activating proteins, regulators of G protein-signaling (RGS) proteins are negative modulators of GPCRs. We previously elucidated that RGS8 of the B/R4 RGS subfamily potently inhibits the action of both Galphaq- and Galphai/o-dependent MCHR1 signaling. In the present study of living cells, we provide evidence that another B/R4 protein, RGS2, is an efficient regulator of MCHR1-mediated calcium signaling exclusively via the Galphaq-dependent pathway. This effect was not observed for RGS4 and RGS5 proteins. Cotransfection of RGS2 with RGS8 additively increased the potency for inhibition of MCHR1 signaling. Truncation experiments revealed that an internal sequence within the N-terminal region of RGS2 (amino acids 28-80) was involved in the RGS2 modulation of MCHR1 activity. Our data suggest that RGS2 and RGS8 differentially associate with MCHR1 and may represent two distinct modes of signaling mechanisms in vivo.