title: Potent inhibition of angiotensin AT1 receptor signaling by RGS8: importance of the C-terminal third exon part of its RGS domain.
abstract: R4/B subfamily RGS (regulator of G protein signaling) proteins play roles in regulation of many GPCR-mediated responses. Multiple RGS proteins are usually expressed in a cell, and it is difficult to point out which RGS protein species are functionally important in the cell. To evaluate intrinsic potency of these RGS proteins, we compared inhibitory effects of RGS1, RGS2, RGS3, RGS4, RGS5, RGS8 and RGS16 on AT1 receptor signaling. Intracellular Ca(2+) responses to angiotensin II were markedly attenuated by transiently expressed RGS2, RGS3 and RGS8, compared to weak inhibition by RGS1, RGS4, RGS5 and RGS16. N-terminally deleted RGS2 (RGS2 domain) lost this potent inhibitory effect, whereas RGS domains of RGS3 and RGS8 showed strong inhibition similar to those of the full-length proteins. To investigate key determinants that specify the differences in potency, we constructed chimeric domains by replacing one or two of three exon parts of RGS8 domain with the corresponding part of RGS5. The chimeric RGS8 domains containing the first or the second exon part of RGS5 showed strong inhibitory effects similar to that of wild type RGS8, but the chimeric domain with the third exon part of RGS5 lost its activity. On the contrary, replacement of the third exon part of RGS5 with the corresponding residues of RGS8 increased the inhibitory effect. The role of the third exon part of RGS8 domain was further confirmed with the chimeric RGS8/RGS4 domains. These results indicate the potent inhibitory activity of RGS8 among R4/B subfamily proteins and importance of the third exon.
authors.affiliation: a Department of Biochemistry and Molecular Pharmacology , Graduate School of Medicine, Chiba University , Chuo-Ku , Chiba , Japan.
authors.forename: Dan
authors.initials: D
authors.lastname: Song
authors.affiliation: a Department of Biochemistry and Molecular Pharmacology , Graduate School of Medicine, Chiba University , Chuo-Ku , Chiba , Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Nishiyama
authors.affiliation: a Department of Biochemistry and Molecular Pharmacology , Graduate School of Medicine, Chiba University , Chuo-Ku , Chiba , Japan.
authors.forename: Sadao
authors.initials: S
authors.lastname: Kimura
mesh_terms: D047228:Angiotensin II Type 1 Receptor Blockers / Q000378:metabolism*; D005091:Exons / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D000072417:Protein Domains; D020710:RGS Proteins / Q000235:genetics* / Q000378:metabolism*; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D020710:RGS Proteins; C080831:RGS1 protein, human; C107413:RGS16 protein; C087182:RGS2 protein, human; C485898:RGS3 protein, human; C491349:RGS5 protein, human; C116924:RGS8 protein, human; D044140:Receptor, Angiotensin, Type 1; C098799:RGS4 protein
keywords: AT1 receptor; G protein; RGS protein