MDIA1 Senses Both Force and Torque during F-actin Filament Polymerisation

Abstract

Formins play a crucial role in regulating actin polymerization. A formin dimer binds to the barbed end of F-actin through its ring-like dimerized FH2 domains and recruits G-actin monomers through its proline-rich FH1 domains in a profilin dependent manner. Formins are often subject to mechanical stretch due to actomyosin contraction; therefore its function has been believed to be dependent on mechanical force. We have recently investigated the effects of force on formin-dependent actin polymerization. In both the presence and the absence of profilin, we observed that force could strongly promote actin polymerization, which strictly required that the actin filament could freely rotate around the formin. These results revealed that formins senses not only tensile force but also torque in the filament. Together, these results provide important new insights into the mechanosensing functions of formin-dependent actin organization in living cells.