NleH effectors interact with Bax inhibitor-1 to block apoptosis during enteropathogenic Escherichia coli infection.
The human pathogens enteropathogenic (EPEC) and enterohemorrhagic Escherichia coli and the related mouse pathogen Citrobacter rodentium subvert a variety of host cell signaling pathways via their plethora of type III secreted effectors, including triggering of an early apoptotic response. EPEC-infected cells do not develop late apoptotic symptoms, however. In this study we demonstrate that the NleH family effectors, homologs of the Shigella effector kinase OspG, blocks apoptosis. During EPEC infection, NleH effectors inhibit elevation of cytosolic Ca(2+) concentrations, nuclear condensation, caspase-3 activation, and membrane blebbing and promote cell survival. NleH1 alone is sufficient to prevent procaspase-3 cleavage induced by the proapoptotic compounds staurosporine, brefeldin A, and tunicamycin. Using C. rodentium, we found that NleH inhibits procaspase-3 cleavage at the bacterial attachment sites in vivo. A yeast two-hybrid screen identified the endoplasmic reticulum six-transmembrane protein Bax inhibitor-1 (BI-1) as an NleH-interacting partner. We mapped the NleH-binding site to the N-terminal 40 amino acids of BI-1. Knockdown of BI-1 resulted in the loss of NleH's antiapoptotic activity. These results indicate that NleH effectors are inhibitors of apoptosis that may act through BI-1 to carry out their cytoprotective function.
Hemrajani
Cordula
C
Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, United Kingdom.
Berger
Cedric N
CN
Robinson
Keith S
KS
Marchès
Olivier
O
Mousnier
Aurelie
A
Frankel
Gad
G
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects; D044082:Citrobacter rodentium; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D004756:Enterobacteriaceae Infections / Q000378:metabolism*; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D013047:Specific Pathogen-Free Organisms; D020798:Two-Hybrid System Techniques; D037521:Virulence Factors / Q000378:metabolism* / Q000494:pharmacology
D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C490015:Tmbim6 protein, mouse; D037521:Virulence Factors; D053148:Caspase 3; D002118:Calcium