title: The Salmonella SpiC protein targets the mammalian Hook3 protein function to alter cellular trafficking.
abstract: The Salmonella SpiC protein is secreted into the cytosol of macrophages via a unique type III secretion system that functions intracellularly to translocate proteins across the phagosomal membrane. The SpiC protein is required for survival within macrophages and inhibition of phagosome-lysosome fusion in vivo, and it is sufficient to inhibit endosome-endosome fusion in vitro. Here, we establish that SpiC targets the function of Hook3, a mammalian protein implicated in cellular trafficking. Purified GST-SpiC pulled down Hook3 from murine macrophages, and anti-Hook3 antibodies precipitated SpiC from the cytosol of Salmonella-infected macrophages. Expression of the spiC gene disrupted Golgi morphology in Vero cells and altered the distribution of lysosomes in macrophages, mimicking the phenotype of cells expressing a hook3 dominant-negative mutant. By inactivating Hook3 function, the SpiC protein may alter the lysosome network and prevent phagosome-lysosome fusion.
authors.affiliation: Department of Molecular Microbiology, Howard Hughes Medical Institute, Washington University School of Medicine, Campus Box 8230, 660 S. Euclid. Ave., St Louis, Missouri 63110-1093, USA.
authors.forename: Yoram
authors.initials: Y
authors.lastname: Shotland
authors.forename: Helmut
authors.initials: H
authors.lastname: Krämer
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Groisman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D017930:Genes, Reporter; D008247:Lysosomes / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology*; D051379:Mice; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D010588:Phagosomes / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; C120280:SpiC protein, Salmonella; C425466:hook3 protein, human; C479499:hook3 protein, mouse; D000242:Cyclic AMP