Ca2+Regulation of Myosin II and Myosin VI during Rupture of theShigella-Containing Vacuole

Abstract

AbstractShigella, the causative agent of bacillary dysentery, invades epithelial cells to colonize the intestinal mucosa. Following invasion,Shigellais enclosed in a vacuole that needs to rupture for bacterial intra-cytosolic replication. We show here that rupture of theShigellavacuole requires Ca2+influx leading to long lasting local Ca2+increases that regulate actin dynamics affecting theShigellavacuole integrity. These Ca2+increases promote vacuolar rupture by activating myosin II associated with actin filaments in membrane ruffles distant from the vacuole, while tethering myosin VI at the actin coat-surrounded vacuole. Ca2+depletion and myosin II inhibition impair formation of the actin coat and vacuole rupture. Inhibition of myosin VI also delays rupture of vacuoles but lead to their tumbling. These findings highlight a role for Ca2+in coordinating actin–based forces and constraints during early rupture steps of bacterial vacuole, that pull on vacuolar membranes and tether them to the actin cortex via myosin II and VI, respectively, a process relevant to intracellular pathogen and endomembrane trafficking.