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Molecular interactions between hosts and pathogens Partho Ghosh Department of Chemistry & Biochemistry and Section of Molecular Biology University of California, San Diego http://pghosh.ucsd.edu Infectious Diseases at the Molecular Level Pathogens Virulence Factors Host cells Host Cell Target Establishment of niche in host Subversion of host defenses and immunity Proliferation in host Transmission to other hosts Type III Secretion Needles Human cell Pathogenic bacterium Kubori et al., Science 280:602 (98) Type III Secretion System (TTSS) • Gram-negative • Pathogens of mammals –Escherichia coli –Pseudomonas aeruginosa –Salmonella tymphimurium –Shigella flexneri –Bordetella pertussis –Chlamydia trachomatis –Yersinia spp. • Pathogens of plants –Erwinia amylovora –Pseudomonas syringae –Ralstonia solanacearum –Xanthomonas campestris Pseudomonas aeruginosa • Ubiquitous and antibiotic-resistant bacterium • Problem for patients with weakened immune systems • Certain strains cause severe and acute infections CDC • 90% of severe and acute strains — inject the protein ExoU into human cells, results in cell death How does ExoU function? Using genome sequences to get the answer Phospholipase A2 motifs — destroy mammalian cell membranes But, overall identity to phospholipase ~10% Phillips et al. JBC (03) Testing the phospholipase idea: Syringe Loading 106 mammalian cells + ExoU ? Clarke & McNeil. (1992) J Cell Sci 102:533-41 Cell Death ExoU kills mammalian cells and needs sites 1 and 2 ExoU needs a mammalian cell component ExoU-GFP Learning what that component is using yeast Yeast without ExoU Yeast making ExoU Cell Death ExoU kills cells but Phospholipase inhibitors block cell death Inhibitors Will inhibitors stop Pseudomonas? Pseudomonas aeruginosa + inhibitor Cell Death Inhibitors protect against Pseudomonas Current Ann Cai Alicia Gamez Jyothi Kumaran Case McNamara Jason Miller Rebecca Phillips Catarina Raposo Loren Rodgers UCSD Ed Dennis David Six Lorraine Pillus William Fenical University of Toronto Charlie Boone Funding W.M. Keck Foundation Cystic Fibrosis Foundation
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