The Septin Cytoskeleton is Required for Plasma Membrane Repair

TL;DR: In this paper , a silencing RNA (siRNA) screen was performed to uncover the plasma membrane repair mechanisms of cells injured by the bacterial pore-forming toxin listeriolysin O (LLO).

Abstract: Mammalian cells are frequently exposed to mechanical and biochemical stresses resulting in plasma membrane injuries. Repair mechanisms rapidly reseal the plasma membrane to restore homeostasis and prevent cell death. In the present work, a silencing RNA (siRNA) screen was performed to uncover the plasma membrane repair mechanisms of cells injured by the bacterial pore-forming toxin listeriolysin O (LLO). The screen identified a novel role for the septin cytoskeleton in mediating plasma membrane repair. Upon cell injury, the septin cytoskeleton partially dissociates from actin stress fibers and remodels with cortical F-actin and myosin-II to form loop (and ring)-like domains that protrude from the cell surface. These domains strictly colocalize with the calcium-dependent phospholipid-binding protein, annexin A2 (ANXA2). Importantly, formation of the SEPT/F-actin/ANXA2 domains are dependent on SEPT7 expression and is functionally correlated with the plasma membrane repair efficiency. Our studies open new research avenues by identifying a novel role for the septin cytoskeleton in remodeling the plasma membrane for its repair. SUMMARY Plasma membrane repair is a fundamental homeostatic process. Excessive damage or defective plasma membrane repair is associated with numerous pathological conditions. This work identifies a novel function of the septin cytoskeleton in remodeling the plasma membrane for its repair.