Legionella pneumophila VipD is a Rab5-activated phospholipase A1

Friday, November 08, 2013 — Poster Session III
10:00 a.m. – 12:00 p.m.	FAES Academic Center (Upper-Level Terrace)	NICHD	MICROBIO-4

Authors

A.H. Gaspar
M. Lucas
A.L. Rojas
A. Hierro
M.P. Machner

Abstract

Legionella pneumophila is an intracellular pathogen and is the causative agent of a severe pneumonia called Legionnaires’ disease. During infection, Legionella avoids the host’s endocytic pathway, an innate immune mechanism regulated by the GTPase Rab5 that facilitates degradation of internalized pathogens. To investigate the mechanism of Legionella endocytic avoidance, we screened an expression library of 147 L. pneumophila translocated effector proteins for Rab5 interaction and discovered that VipD specifically interacted with Rab5. We demonstrate that VipD targets active Rab5 and binding triggers phospholipase A1 activity in VipD. A crystallographic analysis of the complex reveals that a loop obstructing the active site in VipD is repositioned upon Rab5 binding, thereby exposing the catalytic pocket of the phospholipase domain. Within host cells, VipD targets to endosomes in a Rab5-dependent manner where it catalyzes the removal of critical factors for endosomal function such as phosphatidylinositol 3-phosphate (PI(3)P) and the tethering protein early endosome antigen 1 (EEA1). During infection, VipD-deficient L. pneumophila are attenuated in avoiding the endosomal compartment and reside within phagosomes that acquire Rab5 and PI(3)P. Thus, by catalyzing PI(3)P depletion in a Rab5-dependent manner, VipD alters the protein and lipid composition of endosomes thereby blocking their fusion with Legionella-containing vacuoles.