Type II phosphatidylinositol 4-kinases promote Listeria monocytogenes entry into target cells

Abstract

Interaction of the Listeria surface protein InlB with the hepatocyte growth factor receptor Met activates signalling events that trigger bacterial internalization into mammalian epithelial cells. We show here that purified phagosomes containing InlB-coated beads display type II phosphatidylinositol 4-kinase (PI4K) activity. In human epithelial HeLa cells, both PI4KIIalpha and PI4KIIbeta isoforms are corecruited with Met around InlB-coated beads or wild-type Listeria during the early steps of internalization, and phosphatidylinositol 4-phosphate [PI(4)P] is detected at the entry site. We demonstrate that PI4KIIalpha or PI4KIIbeta knockdown, but not type III PI4Kbeta knockdown, inhibits Listeria internalization. Production of PI(4)P derivatives such as phosphatidylinositol 3,4,5-triphosphate [PI(3,4,5)P(3)] upon InlB stimulation is not affected by PI4KIIalpha or beta knockdown, suggesting that these phosphoinositides are generated by a type III PI4K. Strikingly, knockdown of the PI(4)P ligand and clathrin adaptor AP-1 strongly inhibits bacterial entry. Together, our results reveal a yet non-described role for type II PI4Ks in phagocytosis.