A functional role for ezrin during Shigella flexneri entry into epithelialcells

Shigella flexneri is an enteroinvasive bacterium responsible for bacillary dysentery in humans. Bacterial entry into epithelial cells is a crucial ste p for the establishment of the infection. It is characterized by a transien t reorganization of the host cell cytoskeleton at the site of bacterial int eraction with the cell membrane, which leads to bacterial engulfment by a m acropinocytic process. We show in this study that the membrane-cytoskeleton linker, ezrin, a member of the ERM (ezrin, radixin, moesin) family, plays an active role in the process of Shigella uptake. Ezrin is highly enriched in cellular protrusions induced by the bacterium and is found in close asso ciation with the plasma membrane. In addition, Shigella entry is significan tly reduced in cells transfected with a dominant negative allele of ezrin w ith entry foci showing much shorter cellular protrusions. These results ind icate that ezrin not only acts as a membrane-cytoskeleton linker, but may a lso mediate extension of cellular projections in the presence of signals su ch as those elicited by invading microorganisms.