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Mol Biol Cell. 2017 May 15;28(10):1347-1360. doi: 10.1091/mbc.E16-12-0885. Epub 2017 Mar 29.

Phosphorylated cortactin recruits Vav2 guanine nucleotide exchange factor to activate Rac3 and promote invadopodial function in invasive breast cancer cells.

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Department of Cell Biology, Yale University, New Haven, CT 06520.
Faculty of Medicine in the Galilee, Bar-Ilan University, Safed 1311520, Israel.
Department of Chemistry, Yale University, New Haven, CT 06520.
Raymond and Beverly Sackler Laboratory of Genetics and Molecular Medicine, Department of Genetics and Genome Sciences and Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, Farmington, CT 06030.
Department of Anatomy and Structural Biology and Gruss Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461.
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520
Department of Neuroscience, Yale University, New Haven, CT 06520.


Breast carcinoma cells use specialized, actin-rich protrusions called invadopodia to degrade and invade through the extracellular matrix. Phosphorylation of the actin nucleation-promoting factor and actin-stabilizing protein cortactin downstream of the epidermal growth factor receptor-Src-Arg kinase cascade is known to be a critical trigger for invadopodium maturation and subsequent cell invasion in breast cancer cells. The functions of cortactin phosphorylation in this process, however, are not completely understood. We identify the Rho-family guanine nucleotide exchange factor Vav2 in a comprehensive screen for human SH2 domains that bind selectively to phosphorylated cortactin. We demonstrate that the Vav2 SH2 domain binds selectively to phosphotyrosine-containing peptides corresponding to cortactin tyrosines Y421 and Y466 but not to Y482. Mutation of the Vav2 SH2 domain disrupts its recruitment to invadopodia, and an SH2-domain mutant form of Vav2 cannot support efficient matrix degradation in invasive MDA-MB-231 breast cancer cells. We show that Vav2 function is required for promoting invadopodium maturation and consequent actin polymerization, matrix degradation, and invasive migratory behavior. Using biochemical assays and a novel Rac3 biosensor, we show that Vav2 promotes Rac3 activation at invadopodia. Rac3 knockdown reduces matrix degradation by invadopodia, whereas a constitutively active Rac3 can rescue the deficits in invadopodium function in Vav2-knockdown cells. Together these data indicate that phosphorylated cortactin recruits Vav2 to activate Rac3 and promote invadopodial maturation in invasive breast cancer cells.

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