Abstract
Listeria can escape host autophagy defense pathways through mechanisms that remain poorly understood. We show here that in epithelial cells, Listeriolysin (LLO)-dependent cytosolic escape of Listeria triggered a transient amino-acid starvation host response characterized by GCN2 phosphorylation, ATF3 induction and mTOR inhibition, the latter favouring a pro-autophagic cellular environment. Surprisingly, rapid recovery of mTOR signalling was neither sufficient nor necessary for Listeria avoidance of autophagic targeting. Instead, we observed that Listeria phospholipases PlcA and PlcB reduced autophagic flux and phosphatidylinositol 3-phosphate (PI3P) levels, causing pre-autophagosomal structure stalling and preventing efficient targeting of cytosolic bacteria. In co-infection experiments, wild-type Listeria protected PlcA/B-deficient bacteria from autophagy-mediated clearance. Thus, our results uncover a critical role for Listeria phospholipases C in the inhibition of autophagic flux, favouring bacterial escape from host autophagic defense.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Activating Transcription Factor 3 / genetics
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Activating Transcription Factor 3 / metabolism
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Animals
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Autophagy*
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Bacterial Toxins / pharmacology
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Blotting, Western
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Cell Proliferation
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Cells, Cultured
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Cytosol / metabolism
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Embryo, Mammalian / cytology
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Embryo, Mammalian / metabolism
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Embryo, Mammalian / microbiology
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Enzyme-Linked Immunosorbent Assay
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Fibroblasts / cytology
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Fibroblasts / metabolism
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Fibroblasts / microbiology
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Fluorescent Antibody Technique
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HeLa Cells
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Heat-Shock Proteins / pharmacology
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Hemolysin Proteins / pharmacology
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Humans
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Listeria monocytogenes / enzymology*
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Listeriosis / metabolism
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Listeriosis / microbiology
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Listeriosis / pathology*
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Mice
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Phagosomes / metabolism
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Phagosomes / pathology*
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Phosphatidylinositol Phosphates / genetics
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Phosphatidylinositol Phosphates / metabolism
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Phospholipases / genetics
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Phospholipases / metabolism*
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Phosphorylation
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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RNA, Messenger / genetics
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Real-Time Polymerase Chain Reaction
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Reverse Transcriptase Polymerase Chain Reaction
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TOR Serine-Threonine Kinases / genetics
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TOR Serine-Threonine Kinases / metabolism
Substances
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ATF3 protein, human
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Activating Transcription Factor 3
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Bacterial Toxins
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Heat-Shock Proteins
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Hemolysin Proteins
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Phosphatidylinositol Phosphates
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RNA, Messenger
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phosphatidylinositol 3-phosphate
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MTOR protein, human
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EIF2AK4 protein, human
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Protein Serine-Threonine Kinases
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TOR Serine-Threonine Kinases
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Phospholipases
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hlyA protein, Listeria monocytogenes