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Cell Microbiol. 2013 May;15(5):795-808. doi: 10.1111/cmi.12073. Epub 2012 Dec 19.

Identification of the Mycobacterium tuberculosis protein PE-PGRS62 as a novel effector that functions to block phagosome maturation and inhibit iNOS expression.

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Department of Medicine, Experimental Medicine Program, Division of Infectious Diseases, University of British Columbia, Vancouver, British Columbia, Canada.


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.

[Indexed for MEDLINE]

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