Targeting of Mycobacterium tuberculosis heparin-binding hemagglutinin to mitochondria in macrophages

PLoS Pathog. 2011 Dec;7(12):e1002435. doi: 10.1371/journal.ppat.1002435. Epub 2011 Dec 8.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis / physiology
  • Bacterial Proteins / metabolism*
  • Bacterial Proteins / pharmacology
  • Caspases / metabolism
  • Cell Line
  • Cell Separation
  • DNA Fragmentation
  • Enzyme Activation / drug effects
  • Enzyme Activation / physiology
  • Flow Cytometry
  • Humans
  • Immunoblotting
  • Macrophages / drug effects
  • Macrophages / metabolism*
  • Membrane Potential, Mitochondrial / drug effects
  • Membrane Proteins / metabolism*
  • Membrane Proteins / pharmacology
  • Mice
  • Microscopy, Fluorescence
  • Mitochondria / drug effects
  • Mitochondria / metabolism*
  • Mycobacterium tuberculosis / metabolism
  • Reactive Oxygen Species
  • Virulence Factors / metabolism*

Substances

  • Bacterial Proteins
  • HbhA protein, Mycobacterium tuberculosis
  • Membrane Proteins
  • Reactive Oxygen Species
  • Virulence Factors
  • Caspases