title: A Legionella Effector Disrupts Host Cytoskeletal Structure by Cleaving Actin.
abstract: Legionella pneumophila, the etiological agent of Legionnaires' disease, replicates intracellularly in protozoan and human hosts. Successful colonization and replication of this pathogen in host cells requires the Dot/Icm type IVB secretion system, which translocates approximately 300 effector proteins into the host cell to modulate various cellular processes. In this study, we identified RavK as a Dot/Icm substrate that targets the host cytoskeleton and reduces actin filament abundance in mammalian cells upon ectopic expression. RavK harbors an H95EXXH99 motif associated with diverse metalloproteases, which is essential for the inhibition of yeast growth and for the induction of cell rounding in HEK293T cells. We demonstrate that the actin protein itself is the cellular target of RavK and that this effector cleaves actin at a site between residues Thr351 and Phe352. Importantly, RavK-mediated actin cleavage also occurs during L. pneumophila infection. Cleavage by RavK abolishes the ability of actin to form polymers. Furthermore, an F352A mutation renders actin resistant to RavK-mediated cleavage; expression of the mutant in mammalian cells suppresses the cell rounding phenotype caused by RavK, further establishing that actin is the physiological substrate of RavK. Thus, L. pneumophila exploits components of the host cytoskeleton by multiple effectors with distinct mechanisms, highlighting the importance of modulating cellular processes governed by the actin cytoskeleton in the intracellular life cycle of this pathogen.
authors.affiliation: Purdue Institute for Inflammation, Immunology and Infectious Diseases and Department of Biological Sciences, Purdue University, West Lafayette, IN, United States of America.
authors.forename: Yao
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Purdue Institute for Inflammation, Immunology and Infectious Diseases and Department of Biological Sciences, Purdue University, West Lafayette, IN, United States of America.
authors.forename: Wenhan
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Purdue Institute for Inflammation, Immunology and Infectious Diseases and Department of Biological Sciences, Purdue University, West Lafayette, IN, United States of America.
authors.forename: Yunhao
authors.initials: Y
authors.lastname: Tan
authors.affiliation: Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States of America.
authors.forename: Ernesto S
authors.initials: ES
authors.lastname: Nakayasu
authors.affiliation: Purdue Institute for Inflammation, Immunology and Infectious Diseases and Department of Biological Sciences, Purdue University, West Lafayette, IN, United States of America.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Staiger
authors.affiliation: Purdue Institute for Inflammation, Immunology and Infectious Diseases and Department of Biological Sciences, Purdue University, West Lafayette, IN, United States of America.
authors.forename: Zhao-Qing
authors.identifier: 0000-0001-8890-6621
authors.initials: ZQ
authors.lastname: Luo
mesh_terms: D008841:Actin Cytoskeleton / Q000473:pathology*; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D019556:COS Cells; D002522:Chlorocebus aethiops; D003599:Cytoskeleton / Q000473:pathology*; D057809:HEK293 Cells; D054884:Host-Pathogen Interactions / Q000502:physiology*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D016952:Legionella pneumophila / Q000472:pathogenicity*; D007877:Legionnaires' Disease / Q000378:metabolism* / Q000473:pathology; D013058:Mass Spectrometry; D051379:Mice; D000069319:Type IV Secretion Systems / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D000069319:Type IV Secretion Systems