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Proc Natl Acad Sci U S A. 2014 Jan 7;111(1):E25-33. doi: 10.1073/pnas.1315368111. Epub 2013 Dec 17.

A Cdc42- and Rac-interactive binding (CRIB) domain mediates functions of coronin.

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Center for Biochemistry, Medical Faculty, Center for Molecular Medicine Cologne and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, 50931 Köln, Germany.


The Cdc42- and Rac-interactive binding motif (CRIB) of coronin binds to Rho GTPases with a preference for GDP-loaded Rac. Mutation of the Cdc42- and Rac-interactive binding motif abrogates Rac binding. This results in increased 1evels of activated Rac in coronin-deficient Dictyostelium cells (corA(-)), which impacts myosin II assembly. corA(-) cells show increased accumulation of myosin II in the cortex of growth-phase cells. Myosin II assembly is regulated by myosin heavy chain kinase-mediated phosphorylation of its tail. Kinase activity depends on the activation state of the p21-activated kinase a. The myosin II defect of corA(-) mutant is alleviated by dominant-negative p21-activated kinase a. It is rescued by wild-type coronin, whereas coronin carrying a mutated Cdc42- and Rac-interactive binding motif failed to rescue the myosin defect in corA(-) mutant cells. Ectopically expressed myosin heavy chain kinases affinity purified from corA(-) cells show reduced kinase activity. We propose that coronin through its affinity for GDP-Rac regulates the availability of GTP-Rac for activation of downstream effectors.


Rac GTPases; cell signaling; cytoskeleton; protein–protein interaction

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