The septin cytoskeleton is required for plasma membrane repair

Plasma membrane repair is a fundamental homeostatic process of eukaryotic cells. Here, we report a new function for the conserved cytoskeletal proteins known as septins in the repair of cells perforated by pore-forming toxins or mechanical disruption. Using a silencing RNA screen, we identified known repair factors (e.g. annexin A2, ANXA2) and novel factors such as septin 7 (SEPT7) that is essential for septin assembly. Upon plasma membrane injury, the septin cytoskeleton is extensively redistributed to form submembranous domains arranged as knob and loop structures containing F-actin, myosin IIA, S100A11, and ANXA2. Formation of these domains is Ca 2+ -dependent and correlates with plasma membrane repair efficiency. Super-resolution microscopy revealed that septins and F-actin form intertwined filaments associated with ANXA2. Depletion of SEPT7 prevented ANXA2 recruitment and formation of submembranous actomyosin domains. However, ANXA2 depletion had no effect on domain formation. Collectively, our data support a novel septin-based mechanism for resealing damaged cells, in which the septin cytoskeleton plays a key structural role in remodeling the plasma membrane by promoting the formation of SEPT/F-actin/myosin IIA/ANXA2/S100A11 repair domains. Synopsis The septin cytoskeleton is essential for plasma membrane repair. In response to wounding, septins are redistributed in a Ca 2+ -dependent fashion and are required for the formation of submembranous repair domains. The septin cytoskeleton is required for efficient plasma membrane repair of cells wounded mechanically or by transmembrane pores. The septin cytoskeleton is redistributed in a Ca 2+ -dependent fashion during plasma membrane repair to form filaments intertwined with F-actin and arranged in knob and loop-like structures. The septins control the formation of sub-membranous repair domains containing F-actin, myosin IIA, S100A11, and ANXA2. The septin cytoskeleton is essential for plasma membrane repair. In response to wounding, septins are redistributed in a Ca 2+ -dependent fashion and are required for the formation of submembranous repair domains.