The Formin Inhibitor, SMIFH2, Inhibits Members of the Myosin Superfamily

Abstract

AbstractThe small molecular inhibitor of formin FH2 domains, SMIFH2, is widely used in cell biological studies. It was selected in a chemical screen as a compound inhibiting formin-driven actin polymerizationin vitro, but not polymerization of pure actin, and found to be active against several types of formins from different species (Rizvi et al., 2009). Here, in experiments with cultured fibroblasts, we found that SMIFH2 inhibits retrograde flow of myosin 2 filaments and contraction of stress fibers. We further checked the effect of SMIFH2 on non-muscle myosin 2A and skeletal muscle myosin 2in vitroand found that SMIFH2 inhibits myosin ATPase activity and ability to translocate actin filaments in thein vitromotility assay. While inhibition of myosin 2Ain vitrorequired somewhat higher concentration of SMIFH2 than inhibition of retrograde flow and stress fiber contraction in cells, inhibition of several other non-muscle myosin types, e.g. mammalian myosin 10,Drosophilamyosin 7a andDrosophilamyosin 5 by SMIFH2, was equally or more efficient than inhibition of formins. Since actin polymerization and myosin contractility are linked in many cytoskeleton processes, additional careful analysis is needed in each case when function of formins was proposed solely on the basis of experiment with SMIFH2.