A cell-permeable thiooxodihydropyrimidinedione compound that inhibits both formin-mediated, profilin-independent actin nucleation (IC50 ~15 μM using mDia1 or mDia2) and formin-mediated elongation of actin filaments in the presence of profilin (IC50 ~4 μM using Cdc12 or mDia2), but not the Arp2/3-mediated or formin-independent actin assembly. SMIFH2 targets the FH2 (formin homology 2) domain of formins from a large variety of species, including murine mDia1/2, C. elegans CYK-1, S. pombe Cdc12, S. pombe Fus1, and S. cerevisiae Bni1, and decreases formin affinity for the actin filament barbed end. SMIFH2, at 25 μM, is shown to selectively disrupt formin-dependent actin cables and contractile rings, but not Arp2/3-dependent, CK-666- (Cat. No. 182515) sensitive actin patches, in fission yeast. SMIFH2 is also demonstrated to affect F-actin cytoskeleton structures and cell migration (by a 2-fold decrease at 10 μM) in NIH 3T3 fibroblast cultures.
SMIFH2 is an inhibitor of formin homology 2 domains. The compound is a first small molecule inhibitor of formin-mediated actin assembly that disrupts formin dependent processes from yeast to mammals. SMIFH2 may be a useful drug for identifying cellular processes dependent on formin-mediated actin assembly in a broad range of experimental systems. Formin is an actin nucleation factor.
