Lipoamide dehydrogenase mediates retention of coronin-1 on BCG vacuoles, leading to arrest in phagosome maturation

J Cell Sci. 2007 Aug 15;120(Pt 16):2796-806. doi: 10.1242/jcs.006221. Epub 2007 Jul 24.

Abstract

Mycobacterium tuberculosis evades the innate antimicrobial defenses of macrophages by inhibiting the maturation of its phagosome to a bactericidal phagolysosome. Despite intense studies of the mycobacterial phagosome, the mechanism of mycobacterial persistence dependent on prolonged phagosomal retention of the coat protein coronin-1 is still unclear. The present study demonstrated that several mycobacterial proteins traffic intracellularly in M. bovis BCG-infected cells and that one of them, with an apparent subunit size of M(r) 50,000, actively retains coronin-1 on the phagosomal membrane. This protein was initially termed coronin-interacting protein (CIP)50 and was shown to be also expressed by M. tuberculosis but not by the non-pathogenic species M. smegmatis. Cell-free system experiments using a GST-coronin-1 construct showed that binding of CIP50 to coronin-1 required cholesterol. Thereafter, mass spectrometry sequencing identified mycobacterial lipoamide dehydrogenase C (LpdC) as a coronin-1 binding protein. M. smegmatis over-expressing Mtb LpdC protein acquired the capacity to maintain coronin-1 on the phagosomal membrane and this prolonged its survival within the macrophage. Importantly, IFNgamma-induced phagolysosome fusion in cells infected with BCG resulted in the dissociation of the LpdC-coronin-1 complex by a mechanism dependent, at least in part, on IFNgamma-induced LRG-47 expression. These findings provide further support for the relevance of the LpdC-coronin-1 interaction in phagosome maturation arrest.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Bacterial Proteins / metabolism
  • Cholesterol / metabolism
  • Dihydrolipoamide Dehydrogenase / chemistry
  • Dihydrolipoamide Dehydrogenase / metabolism*
  • GTP-Binding Proteins / metabolism
  • Interferon-gamma / pharmacology
  • Macrophages / drug effects
  • Macrophages / microbiology
  • Macrophages / ultrastructure
  • Mice
  • Microbial Viability / drug effects
  • Microfilament Proteins / metabolism*
  • Molecular Sequence Data
  • Molecular Weight
  • Mycobacterium bovis / drug effects
  • Mycobacterium bovis / enzymology*
  • Mycobacterium smegmatis
  • Mycobacterium tuberculosis / drug effects
  • Mycobacterium tuberculosis / enzymology*
  • Phagosomes / drug effects
  • Phagosomes / microbiology*
  • Phagosomes / ultrastructure
  • Protein Binding / drug effects
  • Protein Transport / drug effects
  • Vacuoles / drug effects
  • Vacuoles / microbiology*

Substances

  • Bacterial Proteins
  • Ifi1 protein, mouse
  • Microfilament Proteins
  • coronin proteins
  • Interferon-gamma
  • Cholesterol
  • Dihydrolipoamide Dehydrogenase
  • GTP-Binding Proteins