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Actin Stress Fibers and Focal Adhesions During EMT

Actin cytoskeleton remodeling and focal adhesion formation are associated with increased cell movement during epithelial to mesenchymal transition (EMT). Specifically, Actin is assembled into contractile stress fibers, which are organized structures consisting of parallel Actin fibers with periodic cross-linking proteins such as alpha-Actinin and Myosin II motor proteins. Actin stress fiber assembly is regulated by Rho family GTPases, and fiber stability is maintained by inhibition of Actin depolymerization. Four stress fiber subtypes have been described based on intracellular location: ventral and dorsal stress fibers, perinuclear Actin cap, and transverse arcs. Ventral and dorsal stress fibers are common in motile mesenchymal cells and are linked to the extracellular matrix via focal adhesions. Focal adhesions are dynamic complexes that contain proteins such as Integrins, Focal Adhesion Kinase (FAK), and Vinculin. Focal adhesions link the cytoskeleton to the extracellular matrix and allow the cell to communicate with and respond to its environment. Focal adhesions are also sites of localized signal transduction events that regulate processes such as cell proliferation, differentiation, and migration.