Regulators of G protein signaling (RGS) act as GTPase-activating proteins for Gαi and for Gαq/11. There is recent evidence for interaction of RGS proteins with Gαs, and substitution of Ser for Asp229 in RGS proteins enhances interactions with G proteins. Site-directed mutagenesis of Asp229 was used to assess the effect of this site on the gonadotropin-releasing hormone receptor (GnRHR)-Gαs mediated signaling in the absence or presence of over-expressed RGS3, RGS10 or a truncated form of RGS3 (RGS3T). We observed increased cAMP release with the mutant Gαs(D229S) compared to wt Gαs when GGH3 cells (GH3 cells stably expressing the GnRH receptor) were stimulated with a GnRH agonist. In the presence of RGS3, we did not observe any difference in cAMP release with wt Gαs or with Gαs(D229S) compared to control values; in the presence of RGS3T there was an increase of cAMP release with wt Gαs compared to the control but there was no difference between the Gαs(D229S) and the control values. When cells co-expressed wt Gαs and RGS10, there was a significant increase of cAMP release compared with cells co-expressing wt Gαs and Lac Z. Cells co-expressing Gαs(D229S) and RGS10 showed a significant increase of cAMP release compared to control cells. These results indicate differential regulation of the GnRHR-Gαs mediated signaling by a single mutation in Gαs in the presence of RGS10 and RGS3T, but not with RGS3. This is the first report of an effect of the Gαs(D229S) mutation on G protein-coupled receptor-mediated activation.
- Gonadotropin releasing hormone
- RGS proteins
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism