Activation of the G Protein Gq/11 Through Tyrosine Phosphorylation of the α Subunit

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Science  20 Jun 1997:
Vol. 276, Issue 5320, pp. 1878-1881
DOI: 10.1126/science.276.5320.1878

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Various receptors coupled to the heterotrimeric guanine nucleotide-binding protein Gq/11 stimulate formation of inositol-1,4,5-trisphosphate (IP3). Activation of these receptors also induces protein tyrosine phosphorylation. Formation of IP3 in response to stimulated receptors that couple to Gq/11 was blocked by protein tyrosine kinase inhibitors. These inhibitors appeared to act before activation of Gq/11. Moreover, stimulation of receptors coupled to Gq/11 induced phosphorylation on a tyrosine residue (Tyr356) of the Gαq/11subunit, and this tyrosine phosphorylation event was essential for Gq/11 activation. Tyrosine phosphorylation of Gαq/11 induced changes in its interaction with receptors. Therefore, tyrosine phosphorylation of Gαq/11appears to regulate the activation of Gq/11 protein.

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