molecular interactions between hosts and pathogens partho ghosh department of chemistry &...
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Molecular interactions between hosts and pathogens
Partho GhoshDepartment of Chemistry & Biochemistry
and Section of Molecular BiologyUniversity of California, San Diego
http://pghosh.ucsd.edu
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
Type III Secretion Needles
Kubori et al., Science 280:602 (98)
Pathogenic bacterium
Human cell
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
• 90% of severe and acute strains— inject the protein ExoU into human cells, results in cell death
CDC
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)
Testing the phospholipase idea: Syringe Loading
Clarke & McNeil. (1992) J Cell Sci 102:533-41
106 mammalian cells+
ExoU
?
ExoU kills mammalian cells and needs sites 1 and 2
Cel
l Dea
th
ExoU
Site 1
Site 2
ExoU needs a mammalian cell component
ExoU-GFP
Learning what that component is using yeast
Yeast making ExoU
Yeast without ExoU
ExoU kills cells but
Phospholipase inhibitors block
cell death
Cel
l Dea
th
Inhibitors
Will inhibitors stop Pseudomonas?
Pseudomonas aeruginosa+ inhibitor
Inhibitors protect against Pseudomonas
Cel
l Dea
th
Pseudom
onas
w/o E
xoU
Pseudom
onas
+ Inhib
itor
Pseudom
onas
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