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  • Autophagy Limits Listeria m...
    Py, Bénédicte F.; Lipinski, Marta M.; Yuan, Junying

    Autophagy, 03/2007, Letnik: 3, Številka: 2
    Journal Article

    Autophagy has been recently proposed to be a component of the innate cellular immune response against several types of intracellular microorganisms. However, other intracellular bacteria including Listeria monocytogenes have been thought to evade the autophagic cellular surveillance. Here, we show that cellular infection by L. monocytogenes induces an autophagic response, which inhibits the growth of both the wild-type and a delta actA mutant strain, the latter being impaired in cell-to-cell spreading. The onset of early intracellular growth is accelerated in autophagy-deficient cells, but the growth rate once bacteria begin to multiply in the cytosol does not change. Moreover, a significant fraction of the intracellular bacteria co-localize with autophagosomes at the early time-points after infection. Thus, autophagy targets L. monocytogenes during primary infection by limiting the onset of early bacterial growth. The bacterial expression of listeriolysin O but not phospholipases is necessary for the induction of autophagy, suggesting a possible role for permeabilization of the vacuole in the induction of autophagy. Interestingly, the growth of a delta plcA/B L. monocytogenes strain deficient for bacterial phospholipases is impaired in wild-type cells, but restored in the absence of autophagy, suggesting that bacterial phospholipases may facilitate the escape of bacteria from autophagic degradation. We conclude that L. monocytogenes are targeted for degradation by autophagy during the primary infection, in the early phase of the intracellular cycle, following listeriolysin O-dependent vacuole perforation but preceding active multiplication in the cytosol, and that expression of bacterial phospholipases is necessary for the evasion of autophagy.