Ceramide Induces Cytochrome c Release from Isolated Mitochondria
IMPORTANCE OF MITOCHONDRIAL REDOX STATE*
- Pedram Ghafourifar‡,
- Sabine D. Klein§,
- Olivier Schucht,
- Ursula Schenk,
- Martin Pruschy¶,
- Sonia Rocha¶ and
- Christoph Richter‖
- From the Laboratory of Biochemistry I, Swiss Federal Institute of Technology, Universitatsstrasse 16 and the ¶Department of Radiation Oncology, University Hospital of Zurich, CH-8092 Zurich, Switzerland
Abstract
In the present study we show thatN-acetylsphingosine (C2-ceramide),N-hexanoylsphingosine (C6-ceramide), and, to a much lesser extent, C2-dihydroceramide induce cytochromec (cyto c) release from isolated rat liver mitochondria. Ceramide-induced cyto c release is prevented by preincubation of mitochondria with a low concentration (40 nm) of Bcl-2. The release takes place when cytoc is oxidized but not when it is reduced. Upon cytoc loss, mitochondrial oxygen consumption, mitochondrial transmembrane potential (ΔΨ), and Ca2+ retention are diminished. Incubation with Bcl-2 prevents, and addition of cytoc reverses the alteration of these mitochondrial functions. In ATP-energized mitochondria, ceramides do not alter ΔΨ, neither when cyto c is oxidized nor when it is reduced, ruling out a nonspecific disturbance by ceramides of mitochondrial membrane integrity. Furthermore, ceramides decrease the reducibility of cytoc. We conclude that the apoptogenic properties of ceramides are in part mediated via their interaction with mitochondrial cytoc followed by its release and that the redox state of cytoc influences its detachment by ceramide from the inner mitochondrial membrane.
Footnotes
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↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Parts of this work were presented in the Biochemical Society meeting, Sheffield, United Kingdom, July 1998.
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↵‡ Financially supported by Swiss National Research Foundation Grant 31-45821.95.
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↵§ Financially supported by Leica and Avina Foundation (Switzerland).
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↵‖ To whom correspondence should be addressed. Tel.: 41-1-632-31-36; Fax: 41-1-632-11-21; E-mail:richter{at}bc.biol.ethz.ch.
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↵2 P. Ghafourifar, C. Richter, and J. Brunner, unpublished observation.
- Abbreviations:
- cyto c
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cytochrome c
- AA
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antimycin A
- Asc
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ascorbate
- TMPD
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tetramethyl-1,4-phenylenediamine
- C2-ceramide
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N-acetylsphingosine
- C6-ceramide
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N-hexanoylsphingosine
- DHC
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C2-dihydroceramide
- ΔΨ
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mitochondrial transmembrane potential
- PAGE
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polyacrylamide gel electrophoresis
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- Received August 28, 1998.
- Revision received December 9, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
