The Mycobacterium tuberculosis proteasome active site threonine is essential for persistence yet dispensable for replication and resistance to nitric oxide

PLoS Pathog. 2010 Aug 12;6(8):e1001040. doi: 10.1371/journal.ppat.1001040.

Abstract

Previous work revealed that conditional depletion of the core proteasome subunits PrcB and PrcA impaired growth of Mycobacterium tuberculosis in vitro and in mouse lungs, caused hypersusceptibility to nitric oxide (NO) and impaired persistence of the bacilli during chronic mouse infections. Here, we show that genetic deletion of prcBA led to similar phenotypes. Surprisingly, however, an active site mutant proteasome complemented the in vitro and in vivo growth defects of the prcBA knockout (Delta prcBA) as well as its NO hypersensitivity. In contrast, long-term survival of M. tuberculosis in stationary phase and during starvation in vitro and in the chronic phase of mouse infection required a proteolytically active proteasome. Inhibition of inducible nitric oxide synthase did not rescue survival of Delta prcBA, revealing a function beyond NO defense, by which the proteasome contributes to M. tuberculosis fitness during chronic mouse infections. These findings suggest that proteasomal proteolysis facilitates mycobacterial persistence, that M. tuberculosis faces starvation during chronic mouse infections and that the proteasome serves a proteolysis-independent function.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Catalytic Domain / genetics
  • Female
  • Gene Knockout Techniques
  • Immunoblotting
  • Mice
  • Mice, Inbred C57BL
  • Mutation
  • Mycobacterium tuberculosis / growth & development*
  • Mycobacterium tuberculosis / pathogenicity*
  • Nitric Oxide / metabolism*
  • Polymerase Chain Reaction
  • Proteasome Endopeptidase Complex / chemistry
  • Proteasome Endopeptidase Complex / genetics
  • Proteasome Endopeptidase Complex / metabolism*
  • Threonine / chemistry
  • Threonine / genetics
  • Threonine / metabolism*
  • Tuberculosis

Substances

  • Bacterial Proteins
  • Threonine
  • Nitric Oxide
  • Proteasome Endopeptidase Complex