title: Inhibition and redistribution of NHE3, the apical Na+/H+ exchanger, by Clostridium difficile toxin B.
abstract: NHE3, the apical isoform of the Na(+)/H(+) exchanger, is central to the absorption of salt and water across the intestinal epithelium. We report that treatment of epithelial cells with toxin B of Clostridium difficile, a diarrheal pathogen, causes a pronounced inhibition of NHE3 activity, with little effect on the basolateral NHE1 isoform. Depression of NHE3 activity is accompanied by the translocation of apical exchangers to a subapical endomembrane compartment. Treatment of cells with toxin B increased the fraction of exchangers that were solubilized by nonionic detergents and induced dephosphorylation and extensive redistribution of ezrin. The Rho-kinase inhibitor, Y-27632, also altered the distribution and activity of NHE3. We suggest that inactivation of Rho-family GTPases by clostridial toxin B alters the interaction between NHE3 and the microvillar cytoskeleton, possibly by impairing the ability of ezrin to bridge the exchangers to filamentous actin. Detachment of NHE3 from the actin skeleton would facilitate its internalization, resulting in net disappearance from the apical surface. The consequent inhibition of transport is likely to contribute to the diarrheal effects of C. difficile.
authors.affiliation: Cell Biology Program, Hospital for Sick Children, Department of Biochemistry, University of Toronto, Ontario M5G 1X8, Canada.
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Hayashi
authors.forename: Katalin
authors.initials: K
authors.lastname: Szászi
authors.forename: Natasha
authors.initials: N
authors.lastname: Coady-Osberg
authors.forename: Wendy
authors.initials: W
authors.lastname: Furuya
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Bretscher
authors.forename: John
authors.initials: J
authors.lastname: Orlowski
authors.forename: Sergio
authors.initials: S
authors.lastname: Grinstein
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000494:pharmacology*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D019108:Tight Junctions / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D014018:Tissue Distribution / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D020033:Protein Isoforms; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; C031815:toxB protein, Clostridium difficile