title: Clostridium difficile toxin A inhibits erythropoietin receptor-mediated colonocyte focal adhesion through inactivation of Janus Kinase-2.
abstract: Previously, we demonstrated that the erythropoietin receptor (EpoR) is present on fibroblasts, where it regulates focal contact. Here, we assessed whether this action of EpoR is involved in the reduced cell adhesion observed in colonocytes exposed to Clostridium difficile toxin A. EpoR was present and functionally active in cells of the human colonic epithelial cell line HT29 and epithelial cells of human colon tissues. Toxin A significantly decreased activating phosphorylations of EpoR and its downstream signaling molecules JAK-2 (Janus kinase 2) and STAT5 (signal transducer and activator of transcription 5). In vitro kinase assays confirmed that toxin A inhibited JAK 2 kinase activity. Pharmacological inhibition of JAK2 (with AG490) abrogated activating phosphorylations of EpoR and also decreased focal contacts in association with inactivation of paxillin, an essential focal adhesion molecule. In addition, AG490 treatment significantly decreased expression of occludin (a tight junction molecule) and tight junction levels. Taken together, these data suggest that inhibition of JAK2 by toxin A in colonocytes causes inactivation of EpoR, thereby enhancing the inhibition of focal contact formation and loss of tight junctions known to be associated with the enzymatic activity of toxin A.
authors.affiliation: Department of Life Science, College of Natural Science, Daejin University, Pocheon, Korea.
authors.forename: Seung Taek
authors.initials: ST
authors.lastname: Nam
authors.forename: Heon
authors.initials: H
authors.lastname: Seok
authors.forename: Dae Hong
authors.initials: DH
authors.lastname: Kim
authors.forename: Hyo Jung
authors.initials: HJ
authors.lastname: Nam
authors.forename: Jin Ku
authors.initials: JK
authors.lastname: Kang
authors.forename: Jang Hyun
authors.initials: JH
authors.lastname: Eom
authors.forename: Min Bum
authors.initials: MB
authors.lastname: Lee
authors.forename: Sung Kuk
authors.initials: SK
authors.lastname: Kim
authors.forename: Mi Jung
authors.initials: MJ
authors.lastname: Park
authors.forename: Jong Soo
authors.initials: JS
authors.lastname: Chang
authors.forename: Eun-Mi
authors.initials: EM
authors.lastname: Ha
authors.forename: Ko Eun
authors.initials: KE
authors.lastname: Shong
authors.forename: Jae Sam
authors.initials: JS
authors.lastname: Hwang
authors.forename: Ho
authors.initials: H
authors.lastname: Kim
mesh_terms: D000704:Analysis of Variance; D001427:Bacterial Toxins / Q000494:pharmacology*; D018938:Caco-2 Cells; D002448:Cell Adhesion / Q000187:drug effects; D002478:Cells, Cultured; D015179:Colorectal Neoplasms; D004768:Enterotoxins / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D022001:Focal Adhesions / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D019108:Tight Junctions / Q000378:metabolism
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D017382:Reactive Oxygen Species; D017467:Receptors, Erythropoietin; C041348:tcdA protein, Clostridium difficile; D053614:Janus Kinase 2