A role for host cell exocytosis in InlB ‐mediated internalization of Listeria monocytogenes

SUMMARY
The bacterial surface protein InlB mediates internalization of Listeria monocytogenes into human cells through interaction with the host receptor tyrosine kinase, Met. InlB‐mediated entry requires localized polymerization of the host actin cytoskeleton. Apart from actin polymerization, roles for other host processes in Listeria entry are unknown. Here we demonstrate that exocytosis in the human cell promotes InlB‐dependent internalization. Using a probe consisting of VAMP3 with an exofacial Green Fluorescent Protein (GFP) tag, focal exocytosis was detected during InlB‐mediated entry. Exocytosis was dependent on Met tyrosine kinase activity and the GTPase RalA. Depletion of SNARE proteins by small interfering RNA demonstrated an important role for exocytosis in Listeria internalization. Depletion of SNARE proteins failed to affect actin filaments during internalization, suggesting that actin polymerization and exocytosis are separable host responses. SNARE proteins were required for delivery of the human GTPase Dynamin 2, which promotes InlB‐mediated entry. Our results identify exocytosis as a novel host process exploited by Listeria for infection.

Source: Cellular Microbiology - July 26, 2017 Category: Microbiology Authors: Hoan Van Ngo, Manmeet Bhalla, Da ‐Yuan Chen, Keith Ireton Tags: RESEARCH ARTICLE Source Type: research