Direct evidence that Gi-coupled receptor stimulation of mitogen-activated protein kinase is mediated by G beta gamma activation of p21ras.

Journal Article (Journal Article)

Stimulation of Gi-coupled receptors leads to the activation of mitogen-activated protein kinases (MAP kinases). In several cell types, this appears to be dependent on the activation of p21ras (Ras). Which G-protein subunit(s) (G alpha or the G beta gamma complex) primarily is responsible for triggering this signaling pathway, however, is unclear. We have demonstrated previously that the carboxyl terminus of the beta-adrenergic receptor kinase, containing its G beta gamma-binding domain, is a cellular G beta gamma antagonist capable of specifically distinguishing G alpha- and G beta gamma-mediated processes. Using this G beta gamma inhibitor, we studied Ras and MAP kinase activation through endogenous Gi-coupled receptors in Rat-1 fibroblasts and through receptors expressed by transiently transfected COS-7 cells. We report here that both Ras and MAP kinase activation in response to lysophosphatidic acid is markedly attenuated in Rat-1 cells stably transfected with a plasmid encoding this G beta gamma antagonist. Likewise in COS-7 cells transfected with plasmids encoding Gi-coupled receptors (alpha 2-adrenergic and M2 muscarinic), the activation of Ras and MAP kinase was significantly reduced in the presence of the coexpressed G beta gamma antagonist. Ras-MAP kinase activation mediated through a Gq-coupled receptor (alpha 1-adrenergic) or the tyrosine kinase epidermal growth factor receptor was unaltered by this G beta gamma antagonist. These results identify G beta gamma as the primary mediator of Ras activation and subsequent signaling via MAP kinase in response to stimulation of Gi-coupled receptors.

Full Text

Duke Authors

Cited Authors

  • Koch, WJ; Hawes, BE; Allen, LF; Lefkowitz, RJ

Published Date

  • December 20, 1994

Published In

Volume / Issue

  • 91 / 26

Start / End Page

  • 12706 - 12710

PubMed ID

  • 7809106

Pubmed Central ID

  • PMC45508

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.91.26.12706


  • eng

Conference Location

  • United States