title: Infection of macrophages with Mycobacterium tuberculosis induces global modifications to phagosomal function.
abstract: The phagosome is a central mediator of both the homeostatic and microbicidal functions of a macrophage. Following phagocytosis, Mycobacterium tuberculosis (Mtb) is able to establish infection through arresting phagosome maturation and avoiding the consequences of delivery to the lysosome. The infection of a macrophage by Mtb leads to marked changes in the behaviour of both the macrophage and the surrounding tissue as the bacterium modulates its environment to promote its survival. In this study, we use functional physiological assays to probe the biology of the phagosomal network in Mtb-infected macrophages. The resulting data demonstrate that Mtb modifies phagosomal function in a TLR2/TLR4-dependent manner, and that most of these modifications are consistent with an increase in the activation status of the cell. Specifically, superoxide burst is enhanced and lipolytic activity is decreased upon infection. There are some species- or cell type-specific differences between human and murine macrophages in the rates of acidification and the degree of proteolysis. However, the most significant modification is the marked reduction in intra-phagosomal lipolysis because this correlates with the marked increase in the retention of host lipids in the infected macrophage, which provides a potential source of nutrients that can be accessed by Mtb.
authors.affiliation: Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Podinovskaia
authors.forename: Wonsik
authors.initials: W
authors.lastname: Lee
authors.forename: Shannon
authors.initials: S
authors.lastname: Caldwell
authors.forename: David G
authors.initials: DG
authors.lastname: Russell
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004195:Disease Models, Animal; D054884:Host-Pathogen Interactions / Q000502:physiology; D008066:Lipolysis / Q000502:physiology; D008264:Macrophages / Q000382:microbiology* / Q000473:pathology / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009169:Mycobacterium tuberculosis / Q000472:pathogenicity* / Q000502:physiology; D010588:Phagosomes / Q000502:physiology*; D013481:Superoxides / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D014376:Tuberculosis / Q000503:physiopathology*
chemical_list: C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D013481:Superoxides