The G protein βγ subunit transduces the muscarinic receptor signal for Ca2+ release in Xenopus oocytes

Lisa Stehno-Bittel, Grigory Krapivinsky, Lyubov Krapivinsky, Carmen Perez-Terzic, David E. Clapham

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69 Scopus citations


At least 30 G protein-linked receptors stimulate phosphatidylinositol 4,5-bisphosphate phosphodiesterase (phospholipase Cβ, PLCβ) through G protein subunits to release intracellular calcium from the endoplasmic reticulum (Clapham, D. E. (1995) Cell 80, 259-268). Although both Gα and Gβγ G protein subunits have been shown to activate purified PLCβ in vitro, Gαq has been presumed to mediate the pertussis toxin-insensitive response in vivo. In this study, we show that Gβγ plays a dominant role in muscarinic-mediated activation of PLCβ by employing the Xenopus oocyte expression system. Antisense nucleotides and antibodies to Gαq/11 blocked the m3-mediated signal transduction by inhibiting interaction of the muscarinic receptor with the G protein. Agents that specifically bound free Gβγ subunits (Gα-GDP and a β-adrenergic receptor kinase fragment) inhibited acetylcholine-induced signal transduction to PLCβ, and injection of Gβγ subunits into oocytes directly induced release of intracellular Ca2+. We conclude that receptor coupling specificity of the Gαq/Gβγ heterotrimer is determined by Gαq; Gβγ is the predominant signaling molecule activating oocyte PLCβ.

Original languageEnglish (US)
Pages (from-to)30068-30074
Number of pages7
JournalJournal of Biological Chemistry
Issue number50
StatePublished - Dec 15 1995

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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