Mycobacterium marinum antagonistically induces an autophagic response while repressing the autophagic flux in a TORC1- and ESX-1-dependent manner

PLoS Pathog. 2017 Apr 17;13(4):e1006344. doi: 10.1371/journal.ppat.1006344. eCollection 2017 Apr.

Abstract

Autophagy is a eukaryotic catabolic process also participating in cell-autonomous defence. Infected host cells generate double-membrane autophagosomes that mature in autolysosomes to engulf, kill and digest cytoplasmic pathogens. However, several bacteria subvert autophagy and benefit from its machinery and functions. Monitoring infection stages by genetics, pharmacology and microscopy, we demonstrate that the ESX-1 secretion system of Mycobacterium marinum, a close relative to M. tuberculosis, upregulates the transcription of autophagy genes, and stimulates autophagosome formation and recruitment to the mycobacteria-containing vacuole (MCV) in the host model organism Dictyostelium. Antagonistically, ESX-1 is also essential to block the autophagic flux and deplete the MCV of proteolytic activity. Activators of the TORC1 complex localize to the MCV in an ESX-1-dependent manner, suggesting an important role in the manipulation of autophagy by mycobacteria. Our findings suggest that the infection by M. marinum activates an autophagic response that is simultaneously repressed and exploited by the bacterium to support its survival inside the MCV.

MeSH terms

  • Autophagy*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Dictyostelium / genetics
  • Dictyostelium / metabolism
  • Dictyostelium / microbiology
  • Host-Pathogen Interactions
  • Humans
  • Mechanistic Target of Rapamycin Complex 1
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism*
  • Mycobacterium Infections, Nontuberculous / genetics
  • Mycobacterium Infections, Nontuberculous / metabolism*
  • Mycobacterium Infections, Nontuberculous / physiopathology*
  • Mycobacterium Infections, Nontuberculous / virology
  • Mycobacterium marinum / genetics
  • Mycobacterium marinum / metabolism*
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism*
  • Vacuoles / microbiology

Substances

  • Bacterial Proteins
  • Multiprotein Complexes
  • Mechanistic Target of Rapamycin Complex 1
  • TOR Serine-Threonine Kinases

Grants and funding

This work was supported by Swiss National Science Foundation (http://www.snf.ch/en/Pages/default.aspx) grant Nº 310030_149390 and European Cooperation in Science and Technology (http://www.cost.eu) grant Nº CA15138. TS is a member of iGE3 (http://www.ige3.unige.ch). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.