title: Porins facilitate nitric oxide-mediated killing of mycobacteria.
abstract: Non-pathogenic mycobacteria such us Mycobacterium smegmatis reside in macrophages within phagosomes that fuse with late endocytic/lysosomal compartments. This sequential fusion process is required for the killing of non-pathogenic mycobacteria by macrophages. Porins are proteins that allow the influx of hydrophilic molecules across the mycobacterial outer membrane. Deletion of the porins MspA, MspC and MspD significantly increased survival of M. smegmatis in J774 macrophages. However, the mechanism underlying this observation is unknown. Internalization of wild-type M. smegmatis (SMR5) and the porin triple mutant (ML16) by macrophages was identical indicating that the viability of the porin mutant in vivo was enhanced. This was not due to effects on phagosome trafficking since fusion of phagosomes containing the mutant with late endocytic compartments was unaffected. Moreover, in ML16-infected macrophages, the generation of nitric oxide (NO) was similar to the wild type-infected cells. However, ML16 was significantly more resistant to the effects of NO in vitro compared to SMR5. Our data provide evidence that porins render mycobacteria vulnerable to killing by reactive nitrogen intermediates within phagosomes probably by facilitating uptake of NO across the mycobacterial outer membrane.
authors.affiliation: European Molecular Biology Laboratory, Postfach 102209, 69117 Heidelberg, Germany.
authors.forename: Daniela Leite
authors.initials: DL
authors.lastname: Fabrino
authors.forename: Christopher K E
authors.initials: CK
authors.lastname: Bleck
authors.forename: Elsa
authors.initials: E
authors.lastname: Anes
authors.forename: Andrej
authors.initials: A
authors.lastname: Hasilik
authors.forename: Rossana C N
authors.initials: RC
authors.lastname: Melo
authors.forename: Michael
authors.initials: M
authors.lastname: Niederweis
authors.forename: Gareth
authors.initials: G
authors.lastname: Griffiths
authors.forename: Maximiliano Gabriel
authors.initials: MG
authors.lastname: Gutierrez
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000276:immunology / Q000494:pharmacology*; D002460:Cell Line; D015169:Colony Count, Microbial; D017353:Gene Deletion; D006801:Humans; D008264:Macrophages / Q000276:immunology* / Q000382:microbiology*; D051379:Mice; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects*; D020102:Mycobacterium smegmatis / Q000187:drug effects* / Q000276:immunology; D009569:Nitric Oxide / Q000276:immunology / Q000494:pharmacology*; D018272:Porins / Q000235:genetics / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents; C434272:MspC protein, Mycobacterium smegmatis; C434273:MspD protein, Mycobacterium smegmatis; D018272:Porins; C121838:mspA protein, Mycobacterium smegmatis; D009569:Nitric Oxide