title: Strain-Specific Interactions of Listeria monocytogenes with the Autophagy System in Host Cells.
abstract: Listeria monocytogenes is an intracellular bacterial pathogen that can replicate in the cytosol of host cells. These bacteria undergo actin-based motility in the cytosol via expression of ActA, which recruits host actin-regulatory proteins to the bacterial surface. L. monocytogenes is thought to evade killing by autophagy using ActA-dependent mechanisms. ActA-independent mechanisms of autophagy evasion have also been proposed, but remain poorly understood. Here we examined autophagy of non-motile (ΔactA) mutants of L. monocytogenes strains 10403S and EGD-e, two commonly studied strains of this pathogen. The ΔactA mutants displayed accumulation of ubiquitinated proteins and p62/SQSTM1 on their surface. However, only strain EGD-e ΔactA displayed colocalization with the autophagy marker LC3 at 8 hours post infection. A bacteriostatic agent (chloramphenicol) was required for LC3 recruitment to 10403S ΔactA, suggesting that these bacteria produce a factor for autophagy evasion. Internalin K was proposed to block autophagy of L. monocytogenes in the cytosol of host cells. However, deletion of inlK in either the wild-type or ΔactA background of strain 10403S had no impact on autophagy evasion by bacteria, indicating it does not play an essential role in evading autophagy. Replication of ΔactA mutants of strain EGD-e and 10403S was comparable to their parent wild-type strain in macrophages. Thus, ΔactA mutants of L. monocytogenes can block killing by autophagy at a step downstream of protein ubiquitination and, in the case of strain EGD-e, downstream of LC3 recruitment to bacteria. Our findings highlight the strain-specific differences in the mechanisms that L. monocytogenes uses to evade killing by autophagy in host cells.
authors.affiliation: Cell Biology Program, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada.
authors.forename: Marija
authors.initials: M
authors.lastname: Cemma
authors.affiliation: Cell Biology Program, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada; Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada.
authors.forename: Grace Y
authors.initials: GY
authors.lastname: Lam
authors.affiliation: Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts 02115, United States of America.
authors.forename: Martina
authors.initials: M
authors.lastname: Stöckli
authors.affiliation: Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts 02115, United States of America.
authors.forename: Darren E
authors.initials: DE
authors.lastname: Higgins
authors.affiliation: Cell Biology Program, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada; Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada.
authors.forename: John H
authors.initials: JH
authors.lastname: Brumell
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D001343:Autophagy; D001426:Bacterial Proteins / Q000378:metabolism; D002460:Cell Line; D004285:Dogs; D006360:Heat-Shock Proteins / Q000378:metabolism; D054884:Host-Pathogen Interactions; D007700:Kinetics; D008089:Listeria monocytogenes / Q000502:physiology*; D008088:Listeriosis / Q000382:microbiology*; D061985:Madin Darby Canine Kidney Cells; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D021381:Protein Transport; D000071456:Sequestosome-1 Protein; D057149:Ubiquitinated Proteins / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; C480860:Map1lc3b protein, mouse; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D000071456:Sequestosome-1 Protein; C101343:Sqstm1 protein, mouse; D057149:Ubiquitinated Proteins; C072980:actA protein, Listeria monocytogenes