Clostridium difficile Toxin B Causes Apoptosis in Epithelial Cells by Thrilling Mitochondria
INVOLVEMENT OF ATP-SENSITIVE MITOCHONDRIAL POTASSIUM CHANNELS*
- Paola Matarrese‡1,
- Loredana Falzano‡1,
- Alessia Fabbri‡,
- Lucrezia Gambardella‡,
- Claudio Frank‡,
- Blandine Geny§,
- Michel R. Popoff§,
- Walter Malorni‡2 and
- Carla Fiorentini‡23
- ‡Department of Drug Research and Evaluation, Istituto Superiore di Sanita', Viale Regina Elena 299, 00161 Rome, Italy and the §Unite des Toxines Microbiennes, Institut Pasteur, 75724 Paris, Cedex 15, France
- 3 To whom correspondence should be addressed. Tel.: 39-0649903006; Fax: 39-0649903691; E-mail: carla.fiorentini{at}iss.it.
Abstract
Targeting to mitochondria is emerging as a common strategy that bacteria utilize to interact with these central executioners of apoptosis. Several lines of evidence have in fact indicated mitochondria as specific targets for bacterial protein toxins, regarded as the principal virulence factors of pathogenic bacteria. This work shows, for the first time, the ability of the Clostridium difficile toxin B (TcdB), a glucosyltransferase that inhibits the Rho GTPases, to impact mitochondria. In living cells, TcdB provokes an early hyperpolarization of mitochondria that follows a calcium-associated signaling pathway and precedes the final execution step of apoptosis (i.e. mitochondria depolarization). Importantly, in isolated mitochondria, the toxin can induce a calcium-dependent mitochondrial swelling, accompanied by the release of the proapoptogenic factor cytochrome c. This is consistent with a mitochondrial targeting that does not require the Rho-inhibiting activity of the toxin. Of interest, the mitochondrial ATP-sensitive potassium channels are also involved in the apoptotic response to TcdB and appear to be crucial for the cell death execution phase, as demonstrated by using specific modulators of these channels. To our knowledge, the involvement of these mitochondrial channels in the ability of a bacterial toxin to control cell fate is a hitherto unreported finding.
Footnotes
-
↵4 The abbreviations used are: LT, C. sordelli lethal toxin; mKATP channel, ATP-sensitive mitochondrial potassium channel; 5HD, 5-hydroxydecanoic acid; TcdA, C. difficile toxin A; TcdB, C. difficile toxin B; WT, wild-type; rec, recombinant; cyt, cytochorome; FCCP, carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone; mAb, monoclonal antibody; MMP, mitochondrial membrane potential; MMHP, mitochondrial membrane hyperpolarization; JC-1, 5-5′,6-6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazol-carbocyanine iodide; TMRM, tetramethylrhodamine ester; OLM, oligomycin; PI, propidium iodide; MOPS, 3-(N-morpholino)propanesulfonic acid; NterTcdB, recombinant N-terminal domain of TcdB; NterLT82, recombinant N-terminal domain of C. sordellii LT82; fmk, fluoromethyl ketone; FITC, fluorescein isothiocyanate.
-
↵* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 Both authors contributed equally to this work.
-
↵2 Both authors are principal investigators.
-
- Received August 9, 2006.
- Revision received November 30, 2006.
- The American Society for Biochemistry and Molecular Biology, Inc.
