A truncated form of RGS3 negatively regulates G protein-coupled receptor stimulation of adenylyl cyclase and phosphoinositide phospholipase C

Tapan Kumar Chatterjee, Alex K. Eapen, Rory A. Fisher

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Abstract

Identification of a new family of proteins (RGS proteins) that function as negative regulators of G protein signaling has sparked new understanding of desensitization of this signaling process. Recent studies with several mammalian RGS proteins has delineated their ability to interact with and function as GTPase-activating proteins specifically for G proteins in the G(i) family. Here, we investigated the functional activity of RGS3 and a truncated form of RGS3 on G protein-coupled receptor-mediated activation of adenylyl cyclase, phosphoinositide phospholipase C, and mitogen-activated protein kinase in intact cells. Polymerase chain reaction and 5'-rapid amplification of cDNA ends analyses revealed the tissue-specific expression of a short form of the RGS3 transcript that encodes the approximate carboxyl- terminal half of RGS3. This truncated form of RGS3 (RGS3T) was shown recently to function as a negative regulator of pheromone signaling in yeast (Druey, K. M., Blumer, K. J., Kang, V. R., and Kehrl, J. H. (1996) Nature 379, 742- 746). Baby hamster kidney cells transiently transfected with RGS3T cDNA exhibited a pronounced impairment in platelet-activating factor receptor- stimulated inositol phosphate production, a pertussis toxin-insensitive response. Similarly, calcitonin gone-related peptide receptor-stimulated increases in intracellular cAMP and pituitary adenylate-cyclase activating polypeptide receptor-stimulated increases in both cAMP and inositol phosphates were reduced significantly in RGS3T transfectants compared with vector-transfected control cells. In contrast, baby hamster kidney cells transfected with the full-length RGS3 cDNA showed no impairment in cAMP and inositol phosphate production mediated by these G protein-coupled receptors. However, lysophosphatidic acid receptor-stimulated phosphorylation of endogenous ERK1 and ERK2 was impaired markedly in both RGS3 and RGS3T transfectants, demonstrating the functional ability of both RGS forms to modulate G(i)-mediated signaling. These results provide the first evidence for regulatory effects of an RGS protein on G(s)- and G(q)-mediated signaling in intact cells and document that the carboxyl-terminal region of RGS3 comprises the structural domain for this activity.

Original languageEnglish (US)
Pages (from-to)15481-15487
Number of pages7
JournalJournal of Biological Chemistry
Volume272
Issue number24
DOIs
Publication statusPublished - Jun 13 1997

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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