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![Page 1: Molecular interactions between hosts and pathogens Partho Ghosh Department of Chemistry & Biochemistry and Section of Molecular Biology University of California,](https://reader035.fdocuments.net/reader035/viewer/2022062217/56649f495503460f94c6afac/html5/thumbnails/1.jpg)
Molecular interactions between hosts and pathogens
Partho GhoshDepartment of Chemistry & Biochemistry
and Section of Molecular BiologyUniversity of California, San Diego
http://pghosh.ucsd.edu
![Page 2: Molecular interactions between hosts and pathogens Partho Ghosh Department of Chemistry & Biochemistry and Section of Molecular Biology University of California,](https://reader035.fdocuments.net/reader035/viewer/2022062217/56649f495503460f94c6afac/html5/thumbnails/2.jpg)
Pathogens Host cells
VirulenceFactors
Host Cell Target
Establishment of niche in hostSubversion of host defenses and immunityProliferation in hostTransmission to other hosts
Infectious Diseases at the Molecular Level
![Page 3: Molecular interactions between hosts and pathogens Partho Ghosh Department of Chemistry & Biochemistry and Section of Molecular Biology University of California,](https://reader035.fdocuments.net/reader035/viewer/2022062217/56649f495503460f94c6afac/html5/thumbnails/3.jpg)
Type III Secretion Needles
Kubori et al., Science 280:602 (98)
Pathogenic bacterium
Human cell
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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
![Page 5: Molecular interactions between hosts and pathogens Partho Ghosh Department of Chemistry & Biochemistry and Section of Molecular Biology University of California,](https://reader035.fdocuments.net/reader035/viewer/2022062217/56649f495503460f94c6afac/html5/thumbnails/5.jpg)
Pseudomonas aeruginosa• Ubiquitous and antibiotic-resistant bacterium
• Problem for patients with weakened immune systems
• Certain strains cause severe and acute infections
• 90% of severe and acute strains— inject the protein ExoU into human cells, results in cell death
CDC
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Phospholipase A2 motifs — destroy mammalian cell membranes
But, overall identity to phospholipase ~10%
How does ExoU function?Using genome sequences to get
the answer
Phillips et al. JBC (03)
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Testing the phospholipase idea: Syringe Loading
Clarke & McNeil. (1992) J Cell Sci 102:533-41
106 mammalian cells+
ExoU
?
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ExoU kills mammalian cells and needs sites 1 and 2
Cel
l Dea
th
ExoU
Site 1
Site 2
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ExoU needs a mammalian cell component
ExoU-GFP
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Learning what that component is using yeast
Yeast making ExoU
Yeast without ExoU
![Page 11: Molecular interactions between hosts and pathogens Partho Ghosh Department of Chemistry & Biochemistry and Section of Molecular Biology University of California,](https://reader035.fdocuments.net/reader035/viewer/2022062217/56649f495503460f94c6afac/html5/thumbnails/11.jpg)
ExoU kills cells but
Phospholipase inhibitors block
cell death
Cel
l Dea
th
Inhibitors
![Page 12: Molecular interactions between hosts and pathogens Partho Ghosh Department of Chemistry & Biochemistry and Section of Molecular Biology University of California,](https://reader035.fdocuments.net/reader035/viewer/2022062217/56649f495503460f94c6afac/html5/thumbnails/12.jpg)
Will inhibitors stop Pseudomonas?
Pseudomonas aeruginosa+ inhibitor
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Inhibitors protect against Pseudomonas
Cel
l Dea
th
Pseudom
onas
w/o E
xoU
Pseudom
onas
+ Inhib
itor
Pseudom
onas
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CurrentAnn CaiAlicia GamezJyothi KumaranCase McNamaraJason MillerRebecca PhillipsCatarina RaposoLoren Rodgers
UCSDEd DennisDavid Six
Lorraine Pillus
William Fenical
University of TorontoCharlie Boone
FundingW.M. Keck FoundationCystic Fibrosis Foundation