Mycobacterium marinum controls its interaction with the autophagic pathway.

LERENA, C.; COLOMBO, M. I.

Mar del Plata

Conferencia; XLIII Reunión Anual de la SAIB.; 2007

Mycobacterium marinum is a natural pathogen of fish that occasionally affects humans causing the “fish tank granuloma”. These granulomas are very similar to the ones caused by M. tuberculosis in the lungs of humans. Since M. marinum is a useful model to study pathogenic mycobacteria we have analyzed the interaction of this bacterium with the autophagic pathway.  Raw macrophages overexpressing the autophagy protein GFP-LC3 were infected with RFP-M. marinum and analyzed by confocal microscopy. At 2h post infection (p.i) a clear association of M. marinum with GFP-LC3 was observed. Infected cells were subsequently incubated for two hours in full medium with or without rapamycin (a classical enhancer of autophagy) or in starvation media (plus or minus the autophagy inhibitor wortmannin. The percentage of bacteria associated to GFP-LC3 varied depending on the conditions used, and reached the highest association when rapamycin was used. To determine at which time the autophagic response was more significant we analyzed the recruitment of LC3 at different p.i. times, Interestingly the highest level of association was found between 15 and 30 minutes p.i.  Unexpectedly, heat killed bacteria, was unable to recruit GFP-LC3. Our results indicate that at early p.i. time M. marinum interacts with the autophagic pathway and importantly,  that this interaction is regulated by the bacterium itself.