Regulation of Pulsed Contraction of Actomyosin Networks

Actomyosin contractility regulates various biological processes including cell migration and cytokinesis. Cell cortex underlying a membrane, which is a representative actomyosin network in eukaryote cells, exhibits dynamic contractile behaviors. Interestingly, the cell cortex shows reversible aggregation of actin and myosin called pulsatile contraction in diverse cellular phenomena. While contractile behaviors of actomyosin machinery have been studied extensively in several in vitro and computational studies, none of them successfully reproduced pulsed contraction observed in vivo. In this study, we first reproduced the pulsed contraction only with the mechanical and dynamic behaviors of cytoskeletal components. We found that clusters with physiologically relevant size and duration can appear in the presence of both F-actin turnover and angle-dependent F-actin severing resulting from buckling induced by motor activities. In addition, we showed that RhoA signaling regulating the dynamics of F-actin and myosin can enhance the stability and durability of pulsed clusters. Our study sheds light on the underestimated significance of F-actin dynamics for the pulsed contraction and on the cooperative mechanism between mechanical and biochemical factors.