title: Identification of the Mycobacterium tuberculosis protein PE-PGRS62 as a novel effector that functions to block phagosome maturation and inhibit iNOS expression.
abstract: Using a genetic screen in yeast we found that Mycobacterium tuberculosis PE-PGRS62 was capable of disrupting yeast vacuolar protein sorting, suggesting effects on endosomal trafficking. To study the impact of PE-PGRS62 on macrophage function, we infected murine macrophages with Mycobacterium smegmatis expressing PE-PGRS62. Infected cells displayed phagosome maturation arrest. Phagosomes acquired Rab5, but displayed a significant defect in Rab7 and LAMP-1 acquisition. Macrophages infected with M. smegmatis expressing PE-PGRS62 also expressed two- to threefold less iNOS protein when compared with cells infected with wild-type bacteria. Consistent with this, cells infected with a Mycobacterium marinum transposon mutant for the PE-PGRS62 orthologue showed greater iNOS protein expression when compared to cells infected with wild-type organisms. Complementation restored the ability of the mutant to inhibit iNOS expression. No differences in iNOS transcript levels were observed, suggesting that PE-PGRS62 effects on iNOS expression occurred post-transcriptionally. Marked differences in colony morphology were also seen in M. smegmatis expressing PE-PGRS62 and in the M. marinum transposon mutant, suggesting that PE-PGRS62 may affect cell wall composition. These findings suggest that PE-PGRS62 supports virulence via inhibition of phagosome maturation and iNOS expression, and these phenotypes may be linked to effects on bacterial cell wall composition.
authors.affiliation: Department of Medicine, Experimental Medicine Program, Division of Infectious Diseases, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Emily P
authors.initials: EP
authors.lastname: Thi
authors.forename: Chris Joon Ho
authors.initials: CJ
authors.lastname: Hong
authors.forename: Gaganjit
authors.initials: G
authors.lastname: Sanghera
authors.forename: Neil E
authors.initials: NE
authors.lastname: Reiner
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008264:Macrophages / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D051379:Mice; D020102:Mycobacterium smegmatis / Q000378:metabolism / Q000472:pathogenicity; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000472:pathogenicity; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010588:Phagosomes / Q000378:metabolism / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; C584158:PE-PGRS62 protein, Mycobacterium tuberculosis; D052247:Nitric Oxide Synthase Type II