title: Host Cell-catalyzed S-Palmitoylation Mediates Golgi Targeting of the Legionella Ubiquitin Ligase GobX.
abstract: The facultative intracellular pathogen Legionella pneumophila, the causative agent of Legionnaires disease, infects and replicates within human alveolar macrophages. L. pneumophila delivers almost 300 effector proteins into the besieged host cell that alter signaling cascades and create conditions that favor intracellular bacterial survival. In order for the effectors to accomplish their intracellular mission, their activity needs to be specifically directed toward the correct host cell protein or target organelle. Here, we show that the L. pneumophila effector GobX possesses E3 ubiquitin ligase activity that is mediated by a central region homologous to mammalian U-box domains. Furthermore, we demonstrate that GobX exploits host cell S-palmitoylation to specifically localize to Golgi membranes. The hydrophobic palmitate moiety is covalently attached to a cysteine residue at position 175, which is part of an amphipathic α-helix within the C-terminal region of GobX. Site-directed mutagenesis of cysteine 175 or residues on the hydrophobic face of the amphipathic helix strongly attenuated palmitoylation and Golgi localization of GobX. Together, our study provides evidence that the L. pneumophila effector GobX exploits two post-translational modification pathways of host cells, ubiquitination and S-palmitoylation.
authors: From the Unit on Microbial Pathogenesis, Cell Biology and Metabolism Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892.
authors: Yi-Han
authors: YH
authors: Lin
authors: From the Unit on Microbial Pathogenesis, Cell Biology and Metabolism Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892.
authors: Alexandra G
authors: AG
authors: Doms
authors: From the Unit on Microbial Pathogenesis, Cell Biology and Metabolism Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892.
authors: Eric
authors: E
authors: Cheng
authors: From the Unit on Microbial Pathogenesis, Cell Biology and Metabolism Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892.
authors: Byoungkwan
authors: B
authors: Kim
authors: From the Unit on Microbial Pathogenesis, Cell Biology and Metabolism Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892.
authors: Timothy R
authors: TR
authors: Evans
authors: From the Unit on Microbial Pathogenesis, Cell Biology and Metabolism Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892 machnerm@mail.nih.gov.
authors: Matthias P
authors: MP
authors: Machner
mesh_terms: D055162:Biocatalysis; D006056:Golgi Apparatus / Q000378:metabolism*; D016952:Legionella pneumophila / Q000201:enzymology*; D021381:Protein Transport; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D044767:Ubiquitin-Protein Ligases
keywords: DHHC protein; Golgi; Legionella pneumophila; bacterial pathogenesis; click chemistry; protein palmitoylation; translocated effector; ubiquitylation (ubiquitination)