Conversion of PtdIns(4, 5)P₂ into PtdIns(5)P by the S.flexneri effector IpgD reorganizes host cell morphology

Phosphoinositides play a central role in the control of several cellular events including actin cytoskeleton organization. Here we show that, upon infection of epithelial cells with the Gram-negative pathogen Shigella flexneri, the virulence factor IpgD is translocated directly into eukaryotic cells and acts as a potent inositol 4-phosphatase that specifically dephosphorylates phosphatidylinositol 4, 5-bisphosphate [PtdIns- (4, 5)P₂] into phosphatidylinositol 5-monophosphate [PtdIns(5)P] that then accumulates. Transfection experiments indicate that the transformation of PtdIns(4, 5)P₂ into PtdIns(5)P by IpgD is responsible for dramatic morphological changes of the host cell, leading to a decrease in membrane tether force associated with membrane blebbing and actin filament remodelling. These data provide the molecular basis for a new mechanism employed by a pathogenic bacterium to promote membrane ruffling at the entry site.