title: Pseudomonas aeruginosa ExoT Induces Atypical Anoikis Apoptosis in Target Host Cells by Transforming Crk Adaptor Protein into a Cytotoxin.
abstract: Previously, we demonstrated that Pseudomonas aeruginosa ExoT induces potent apoptosis in host epithelial cells in a manner that primarily depends on its ADP-ribosyltransferase domain (ADPRT) activity. However, the mechanism underlying ExoT/ADPRT-induced apoptosis remains undetermined. We now report that ExoT/ADPRT disrupts focal adhesion sites, activates p38β and JNK, and interferes with integrin-mediated survival signaling; causing atypical anoikis. We show that ExoT/ADPRT-induced anoikis is mediated by the Crk adaptor protein. We found that Crk-/- knockout cells are significantly more resistant to ExoT-induced apoptosis, while Crk-/- cells complemented with Crk are rendered sensitive to ExoT-induced apoptosis. Moreover, a dominant negative (DN) mutant form of Crk phenocopies ExoT-induced apoptosis both kinetically and mechanistically. Crk is generally believed to be a component of focal adhesion (FA) and its role in cellular survival remains controversial in that it has been found to be either pro-survival or pro-apoptosis. Our data demonstrate that although Crk is recruited to FA sites, its function is likely not required for FA assembly or for survival per se. However, when modified by ExoT or by mutagenesis, it can be transformed into a cytotoxin that induces anoikis by disrupting FA sites and interfering with integrin survival signaling. To our knowledge, this is the first example whereby a bacterial toxin exerts its cytotoxicity by subverting the function of an innocuous host cellular protein and turning it against the host cell.
authors.affiliation: Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America.
authors.forename: Stephen
authors.initials: S
authors.lastname: Wood
authors.affiliation: Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America.
authors.forename: Josef
authors.initials: J
authors.lastname: Goldufsky
authors.affiliation: Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America; Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois, United States of America; Cancer Center, Rush University Medical Center, Chicago, Illinois, United States of America.
authors.forename: Sasha H
authors.initials: SH
authors.lastname: Shafikhani
mesh_terms: D036002:ADP Ribose Transferases / Q000378:metabolism* / Q000494:pharmacology; D023102:Anoikis / Q000187:drug effects / Q000502:physiology*; D001427:Bacterial Toxins / Q000494:pharmacology; D015153:Blotting, Western; D002448:Cell Adhesion / Q000187:drug effects; D049109:Cell Proliferation; D003603:Cytotoxins / Q000494:pharmacology*; D022001:Focal Adhesions / Q000187:drug effects / Q000502:physiology*; D020690:GTPase-Activating Proteins / Q000494:pharmacology*; D005799:Genes, Dominant; D006367:HeLa Cells; D006801:Humans; D016023:Integrins / Q000378:metabolism; D018715:Microscopy, Video; D009154:Mutation / Q000235:genetics; D050737:Proto-Oncogene Proteins c-crk / Q000235:genetics / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D059008:Time-Lapse Imaging
chemical_list: D001427:Bacterial Toxins; C485285:CRK protein, human; D003603:Cytotoxins; C477521:ExoT protein, Pseudomonas aeruginosa; D020690:GTPase-Activating Proteins; D016023:Integrins; D050737:Proto-Oncogene Proteins c-crk; D036002:ADP Ribose Transferases