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Updated: Jun 17, 2026

Measuring G-protein-coupled Receptor Signaling via Radio-labeled GTP Binding
Published on: June 9, 2017
G protein subunit Galpha13 binds to integrin alphaIIbbeta3 and mediates integrin "outside-in" signaling
Haixia Gong1, Bo Shen, Panagiotis Flevaris
1Department of Pharmacology, University of Illinois at Chicago, 835 South Wolcott Avenue, Room E403, Chicago, IL 60612, USA.
Abstract:
Integrins mediate cell adhesion to the extracellular matrix and transmit signals within the cell that stimulate cell spreading, retraction, migration, and proliferation. The mechanism of integrin outside-in signaling has been unclear. We found that the heterotrimeric guanine nucleotide-binding protein (G protein) Galpha13 directly bound to the integrin beta3 cytoplasmic domain and that Galpha13-integrin interaction was promoted by ligand binding to the integrin alphaIIbbeta3 and by guanosine triphosphate (GTP) loading of Galpha13. Interference of Galpha13 expression or a myristoylated fragment of Galpha13 that inhibited interaction of alphaIIbbeta3 with Galpha13 diminished activation of protein kinase c-Src and stimulated the small guanosine triphosphatase RhoA, consequently inhibiting cell spreading and accelerating cell retraction. We conclude that integrins are noncanonical Galpha13-coupled receptors that provide a mechanism for dynamic regulation of RhoA.
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