blister and monastrol

Non-muscle myosin II has diverse functions in cell contractility, cytokinesis and locomotion, but the specific contributions of its different isoforms have yet to be clarified. Here, we report that ablation of the myosin IIA isoform results in pronounced defects in cellular contractility, focal adhesions, actin stress fibre organization and tail retraction. Nevertheless, myosin IIA-deficient cells display substantially increased cell migration and exaggerated membrane ruffling, which was dependent on the small G-protein Rac1, its activator Tiam1 and the microtubule moter kinesin Eg5. Myosin IIA deficiency stabilized microtubules, shifting the balance between actomyosin and microtubules with increased microtubules in active membrane ruffles. When microtubule polymerization was suppressed, myosin IIB could partially compensate for the absence of the IIA isoform in cellular contractility, but not in cell migration. We conclude that myosin IIA negatively regulates cell migration and suggest that it maintains a balance between the actomyosin and microtubule systems by regulating microtubule dynamics.

Topics: Actomyosin; Aminoquinolines; Animals; Azepines; Cell Adhesion; Cell Movement; Chlorocebus aethiops; COS Cells; Embryonic Stem Cells; Enzyme Inhibitors; Fibroblasts; Guanine Nucleotide Exchange Factors; Heterocyclic Compounds, 4 or More Rings; Humans; Kinesins; Mice; Microtubules; Naphthalenes; Nocodazole; Nonmuscle Myosin Type IIA; Nonmuscle Myosin Type IIB; Pyrimidines; rac1 GTP-Binding Protein; RNA, Small Interfering; T-Lymphoma Invasion and Metastasis-inducing Protein 1; Thiones; Transfection; Vinblastine