RGS10 is a selective activator of Gαi GTPase activity

Abstract

Polypeptides that define a protein family termed RGS (for regulators of G-protein signalling) are encoded by the SST2 gene of the yeast Saccharomyces cerevisiae, the EGL-10 gene of the nematode Caenorhabdatis elegans, and several related mammalian genes. Genetic studies in invertebrates and mammalian cell-transfection experiments indicate that RGS proteins negatively regulate signalling pathways involving seven transmembrane receptors and heterotrimeric G proteins. However, the biochemical mechanism by which RGS proteins control these pathways is unknown. Here we report the characterization of human RGS10, a member of this protein family. Co-immunoprecipitation studies demonstrate that RGS10 associates specifically with the activated forms of two related G-protein subunits, G alphai3, and G alphaz, but fails to interact with the structurally and functionally distinct G alphas subunit. In vitro assays with purified proteins indicate that RGS10 increases potently and selectively the GTP hydrolytic activity of several members of the G alphai family, including G alphai3, G alphaz, and G alpha0. These results demonstrate that RGS proteins can attenuate signalling pathways involving heterotrimeric G proteins by serving as GTPase-activating proteins for specific types of G alpha subunits.

RGSZ1 and GAIP Regulate μ- but Not δ-Opioid Receptors in Mouse CNS: Role in Tachyphylaxis and Acute Tolerance

“…In contrast, RGS of the R4 and R7 subfamilies bind GaGDP.P much better than GaGTP (Berman et al, 1996;Hunt et al, 1996;Posner et al, 1999). The extreme N-terminal helix of Gaz is crucial for interaction with Rz proteins Wang et al, 1998).…”

“…The impairment of RGSZ1 would permit a large fraction of GazGTP subunits to reach and regulate their effectors. After they spontaneously acquire their GazGDP.P transition state, they can also be deactivated by RGS4 and RGS10 proteins (Berman et al, 1996;Hunt et al, 1996;Hepler et al, 1997). The enhanced opioid analgesic effects observed in RGSZ1 knockdown mice were sensitive to CTOP antagonism, indicating the presence and binding of the m agonists to the opioid receptors.…”

The RGSZ2 Protein Exists in a Complex with μ-Opioid Receptors and Regulates the Desensitizing Capacity of Gz Proteins

“…The way that the distinct RGS proteins interact with Ga subunits has diverse regulatory consequences. While no RGS domain binds efficiently to the GaGDP forms that cannot regulate effector proteins, RGS proteins of the RGS-R4 and RGS-R7 subfamilies display greater affinity for GTP hydrolysis transition state than to the GaGTP form (Hunt et al, 1996;Berman et al, 1996;Posner et al, 1999). In contrast, the members of the RGS-Rz subfamily show the singular characteristic of binding with similar affinities to activated GaGTP and to the transition state .…”

“…The GazGTP subunits have a low intrinsic GTPase rate and thus RGSZ1 knockdown should prolong the period that GazGTP subunits act upon their effectors. In these circumstances, their deactivation would rely on other RGS proteins, for example, the RGS4 and RGS10 proteins (Berman et al, 1996;Hunt et al, 1996;Hepler et al, 1997). Similarly, while the potential of morphine and DAMGO to promote antinociception increases in the RGSZ1 knockdown mice, desensitization can be detected hours after their effects have ceased (Garzón et al, 2004).…”

Sumoylated RGS-Rz Proteins Act as Scaffolds for Mu-Opioid Receptors and G-Protein Complexes in Mouse Brain

“…Typically, RGS proteins display greater affinity to binding to the so-called transition state in which the conformation of the Ga is changed in order to initiate the conversion of the GTP into GDP (Berman et al, 1996;Hunt et al, 1996). However, the members of the RGS-Rz subfamily exhibit the distinctive feature of binding with similar affinities to the activated GaGTP subunits as well as to the transition state .…”