Salmonella effector AvrA regulation of colonic epithelial cell inflammation by deubiquitination.
AvrA is a newly described bacterial effector existing in Salmonella. Here, we test the hypothesis that AvrA is a deubiquitinase that removes ubiquitin from two inhibitors of the nuclear factor-kappaB (NF-kappaB) pathway, IkappaBalpha and beta-catenin, thereby inhibiting the inflammatory responses of the host. The role of AvrA was assessed in intestinal epithelial cell models and in mouse models infected with AvrA-deficient and -sufficient Salmonella strains. We also purified AvrA and AvrA mutant proteins and characterized their deubiquitinase activity in a cell-free system. We investigated target gene and inflammatory cytokine expression, as well as effects on epithelial cell proliferation and apoptosis induced by AvrA-deficient and -sufficient bacterial strains in vivo. Our results show that AvrA blocks degradation of IkappaBalpha and beta-catenin in epithelial cells. AvrA deubiquitinates IkappaBalpha, which blocks its degradation and leads to the inhibition of NF-kappaB activation. Target genes of the NF-kappaB pathway, such as interleukin-6, were correspondingly down-regulated during bacterial infection with Salmonella expressing AvrA. AvrA also deubiquitinates and thus blocks degradation of beta-catenin. Target genes of the beta-catenin pathway, such as c-myc and cyclinD1, were correspondingly up-regulated with AvrA expression. Increased beta-catenin further negatively regulates the NF-kappaB pathway. Our findings suggest an important role for AvrA in regulating host inflammatory responses through NF-kappaB and beta-catenin pathways.
Ye
Zhongde
Z
Department of Pathology, The University of Chicago, Chicago, Illinois, USA.
Petrof
Elaine O
EO
Boone
David
D
Claud
Erika C
EC
Sun
Jun
J
D000818:Animals; D017209:Apoptosis; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D003106:Colon / Q000166:cytology*; D056741:Cyclin D; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D005260:Female; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D012481:Salmonella Infections, Animal / Q000276:immunology; D015398:Signal Transduction / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
C487891:AvrA protein, Salmonella typhimurium; D001426:Bacterial Proteins; D056741:Cyclin D; D016213:Cyclins; D020672:I-kappa B Proteins; C489428:Myc protein, mouse; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D025801:Ubiquitin; D051176:beta Catenin; D000072000:NF-KappaB Inhibitor alpha
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