Local RhoA activation induces septin recruitment

The regulation of the actin cytoskeleton is key for controlling cell shape and structure. While the Rho GTPase RhoA is well known to regulate the actomyosin cytoskeleton, its function in controlling the septin cytoskeleton remains unclear. As RhoA interactions can vary in both time and space, they can be challenging to discern from traditional bulk biochemical assays. Here we use multiple optogenetic tools to spatially and temporally increase myosin localization, stimulate contractile force, and activate RhoA, to investigate how RhoA and its downstream effector myosin impact the septin cytoskeleton. We find that neither local accumulation of myosin nor increased activity of myosin is sufficient to alter septin architecture. Local activation of RhoA, however, results in a local increase in septin accumulation. Importantly, this septin increase is independent of the scaffolding protein anillin, which can directly bind both septin and RhoA. Together these data expand the potential role of septins in mediating RhoA signaling by stimulating the remodeling of the septin cytoskeleton.