Transducing the Signals: A G Protein Takes a New Identity

Danny N. Dhanasekaran^*

Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 19140, USA.

Summary: The prevailing dogma is that heterotrimeric G proteins exclusively transduce signals from the seven-transmembrane motif–containing cell surface receptors, also known as G protein–coupled receptors (GPCRs). New evidence indicates that G₁₃, the subunit of the G protein G₁₃, breaks away from this traditional exclusive signaling alliance with GPCRs to transmit signals from receptor tyrosine kinases (RTKs), such as platelet-derived growth factor receptor (PDGFR), epidermal growth factor receptor (EGFR), and vascular endothelial growth factor receptor (VEGFR). G₁₃ is involved in cell migration in response to GPCRs activated by lysophosphatidic acid (LPA) or thrombin. A new report indicates that G₁₃ is also required for cell migration induced by the growth factors, such as PDGF, EGF, or VEGF. GPCR coupling is not required for such RTK-to-G₁₃ signaling. This new identity for G₁₃ as a signal transducer for both GPCRs and RTKs may be a forerunner for similar findings involving other G subunits. This expanding role of G proteins in both GPCR signaling and RTK signaling is likely to have a great impact not only on our understanding of cell signaling in general, but also more specifically where the dysregulation of signaling by GPCRs, RTKs, and G proteins cause pathophysiological changes such as in the case of tumorigenesis, tumor progression and/or metastasis.

*Contact information. E-mail, danny001{at}temple.edu

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