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Curr Opin Cell Biol. 2012 Oct;24(5):600-6. doi: 10.1016/ Epub 2012 Sep 11.

Inside-out, outside-in, and inside-outside-in: G protein signaling in integrin-mediated cell adhesion, spreading, and retraction.

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Department of Pharmacology, University of Illinois at Chicago, Chicago, IL 60612, United States.


The integrin family of cell adhesion receptors mediates bi-directional signaling: 'inside-out' signaling activates the ligand binding function of integrins and 'outside-in' signaling mediates cellular responses induced by ligand binding to integrins leading to cell spreading, retraction, migration, and proliferation. Integrin signaling requires both heterotrimeric G proteins and monomeric small G proteins. This review focuses on recent development in the roles of G proteins in integrin outside-in signaling. The finding of direct interaction between the heterotrimeric G protein subunit Gα13 and integrin β subunits reveals a new mechanism for integrin signaling, and also uncovers a crosstalk between the signaling pathways initiated by G protein-coupled receptors (GPCRs) and integrins. This crosstalk, which may be referred to as 'inside-outside-in' signaling, dynamically regulates contractility and greatly promotes integrin outside-in signaling.

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