The Anaplasma phagocytophilum-occupied vacuole selectively recruits Rab-GTPases that are predominantly associated with recycling endosomes.

Anaplasma phagocytophilum is an obligate intracellular bacterium that infects neutrophils to reside within a host cell-derived vacuole. The A. phagocytophilum-occupied vacuole (ApV) fails to mature along the endocytic pathway and is non-fusogenic with lysosomes. Rab GTPases regulate membrane traffic. To better understand how the bacterium modulates the ApV's selective fusogencity, we examined the intracellular localization of 20 green fluorescent protein (GFP) or red fluorescent protein (RFP)-tagged Rab GTPases in A. phagocytophilum-infected HL-60 cells. GFP-Rab4A, GFP-Rab10, GFP-Rab11A, GFP-Rab14, RFP-Rab22A and GFP-Rab35, which regulate endocytic recycling, and GFP-Rab1, which mediates endoplasmic reticulum to Golgi apparatus trafficking, localize to the ApV. Fluorescently tagged Rabs are recruited to the ApV upon its formation and remain associated throughout infection. Endogenous Rab14 localizes to the ApV. Tetracycline treatment concomitantly promotes loss of recycling endosome-associated GFP-Rabs and acquisition of GFP-Rab5, GFP-Rab7, and the lysosomal marker, LAMP-1. Wild-type and GTPase- deficient versions, but not GDP-restricted versions of GFP-Rab1, GFP-Rab4A and GFP-Rab11A, localize to the ApV. Strikingly, GFP-Rab10 recruitment to the ApV is guanine nucleotide-independent. These data establish that A. phagocytophilum selectively recruits Rab GTPases that are primarily associated with recycling endosomes to facilitate its intracellular survival and implicate bacterial proteins in regulating Rab10 membrane cycling on the ApV.