The RD1 cluster from Mycobacterium marinum is responsible for autophagy activation upon infection

LERENA MC; COLOMBO MI.

Puerto Madryn

Congreso; XLVI Reunión Anual. Sociedad Argentina de Investigación en Bioquímica y Biología Celular; 2010

SAIB

Mycobacterium marinum (Mm), is widely used as a model to study pathogenic mycobacteria. In recent studies we have observed a marked recruitment of the autophagic protein LC3 to Mm phagosomes in cells incubated in control (i.e. full medium) or starvation conditions; a feature that is lost with heat-killed bacteria. However, when autophagy was induced pharmacologically by the drug rapamycin (Rap) the Mm phagosome was clearly decorated with LC3, despite bacterial status (i.e. live or heat-killed bacteria). Moreover, Rap was able to deliver LC3 to phagosomes containing an inert particle such as IgG-coated latex beads (IgG-LB). Interestingly, this process required a functional Atg5 protein since it was not observed in MEF Atg5 knock out cells, indicating that it depends on a functional autophagic pathway. We have also observed that Mm infection target LC3 to neighbor IgG-LB phagosomes even in control condition. Finally, we assessed the infection with Mm lacking the virulence cluster RD1 (Mm ∆RD1), which encodes several virulence factors and is deficient in the ESX-1 secretion system. We have found that Mm ∆RD1 was unable to recruit LC3 to its phagosome, but, as expected it acquired LC3 when Rap was used. Thus, our results suggest indicate that a factor secreted by the ESX-1 secretion system is responsible for LC3 recruitment to Mm phagosomes, a requirement overcome by Rap treatment.