title: Targeting of Mycobacterium tuberculosis heparin-binding hemagglutinin to mitochondria in macrophages.
abstract: Mycobacterium tuberculosis heparin-binding hemagglutinin (HBHA), a virulence factor involved in extrapulmonary dissemination and a strong diagnostic antigen against tuberculosis, is both surface-associated and secreted. The role of HBHA in macrophages during M. tuberculosis infection, however, is less well known. Here, we show that recombinant HBHA produced by Mycobacterium smegmatis effectively induces apoptosis in murine macrophages. DNA fragmentation, nuclear condensation, caspase activation, and poly (ADP-ribose) polymerase cleavage were observed in apoptotic macrophages treated with HBHA. Enhanced reactive oxygen species (ROS) production and Bax activation were essential for HBHA-induced apoptosis, as evidenced by a restoration of the viability of macrophages pretreated with N-acetylcysteine, a potent ROS scavenger, or transfected with Bax siRNA. HBHA is targeted to the mitochondrial compartment of HBHA-treated and M. tuberculosis-infected macrophages. Dissipation of the mitochondrial transmembrane potential (ΔΨ(m)) and depletion of cytochrome c also occurred in both macrophages and isolated mitochondria treated with HBHA. Disruption of HBHA gene led to the restoration of ΔΨ(m) impairment in infected macrophages, resulting in reduced apoptosis. Taken together, our data suggest that HBHA may act as a strong pathogenic factor to cause apoptosis of professional phagocytes infected with M. tuberculosis.
authors.affiliation: Department of Microbiology, Research Institute for Medical Sciences, College of Medicine, Chungnam National University, Daejeon, South Korea.
authors.forename: Hosung
authors.initials: H
authors.lastname: Sohn
authors.forename: Jong-Seok
authors.initials: JS
authors.lastname: Kim
authors.forename: Sung Jae
authors.initials: SJ
authors.lastname: Shin
authors.forename: Kwangwook
authors.initials: K
authors.lastname: Kim
authors.forename: Choul-Jae
authors.initials: CJ
authors.lastname: Won
authors.forename: Woo Sik
authors.initials: WS
authors.lastname: Kim
authors.forename: Ki-Nam
authors.initials: KN
authors.lastname: Min
authors.forename: Han-Gyu
authors.initials: HG
authors.lastname: Choi
authors.forename: Je Chul
authors.initials: JC
authors.lastname: Lee
authors.forename: Jeong-Kyu
authors.initials: JK
authors.lastname: Park
authors.forename: Hwa-Jung
authors.initials: HJ
authors.lastname: Kim
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001426:Bacterial Proteins / Q000378:metabolism* / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002469:Cell Separation; D053938:DNA Fragmentation; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000378:metabolism; D017382:Reactive Oxygen Species; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C440647:HbhA protein, Mycobacterium tuberculosis; D008565:Membrane Proteins; D017382:Reactive Oxygen Species; D037521:Virulence Factors; D020169:Caspases