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Nature. 1995 Aug 31;376(6543):781-4.

Receptor-tyrosine-kinase- and G beta gamma-mediated MAP kinase activation by a common signalling pathway.

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  • 1Howard Hughes Medical Institute, Department of Medicine (Cardiology), Duke University Medical Center, Durham, North Carolina 27710, USA.


Mitogen-activated protein (MAP) kinases mediate the phosphorylation and activation of nuclear transcription factors that regulate cell growth. MAP kinase activation may result from stimulation of either tyrosine-kinase (RTK) receptors, which possess intrinsic tyrosine kinase activity, or G-protein-coupled receptors (GPCR). RTK-mediated mitogenic signalling involves a series of SH2- and SH3-dependent protein-protein interactions between tyrosine-phosphorylated receptor, Shc, Grb2 and Sos, resulting in Ras-dependent MAP kinase activation. The beta gamma subunits of heterotrimeric G proteins (G beta gamma) also mediate Ras-dependent MAP kinase activation by an as-yet unknown mechanism. Here we demonstrate that activation of MAP kinase by Gi-coupled receptors is preceded by the G beta gamma-mediated tyrosine phosphorylation of Shc, leading to an increased functional association between Shc, Grb2 and Sos. Moreover, disruption of the Shc-Grb2-Sos complex blocks G beta gamma-mediated MAP kinase activation, indicating that G beta gamma does not mediate MAP kinase activation by a direct interaction with Sos. These results indicate that G beta gamma-mediated MAP kinase activation is initiated by a tyrosine phosphorylation event and proceeds by a pathway common to both GPCRs and RTKs.

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