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Biological Chemistry

Editor-in-Chief: Brüne, Bernhard

Editorial Board Member: Buchner, Johannes / Ludwig, Stephan / Sies, Helmut / Turk, Boris / Wittinghofer, Alfred

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Adrenodoxin (Adx) and CYP11A1 (P450scc) induce apoptosis by the generation of reactive oxygen species in mitochondria

Evi Derouet-Hümbert1 / Klaus Roemer2 / Matthias Bureik3

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Corresponding author

Citation Information: Biological Chemistry. Volume 386, Issue 5, Pages 453–461, ISSN (Online) 1437-4315, ISSN (Print) 1431-6730, DOI: 10.1515/BC.2005.054, July 2005

Publication History

Received:
October 29, 2004
Accepted:
February 25, 2005
Published Online:
2005-07-05

Abstract

Mitochondrial cytochrome P450 systems are an indispensable component of mammalian steroid biosynthesis; they catalyze regio- and stereo-specific steroid hydroxylations and consist of three protein entities: adrenodoxin reductase (AdR), adrenodoxin (Adx), and a mitochondrial cytochrome P450 enzyme, e.g., CYP11A1 (P450 side chain cleavage, P450scc). It is known that the latter two are able to generate reactive oxygen species (ROS) in vitro. In this study, we investigated whether this ROS generation also occurs in vivo and, if so, whether it leads to the induction of apoptosis. We found that overexpression of either human or bovine Adx causes a significant loss of viability in 11 different cell lines. This loss of viability does not depend on the presence of the tumor suppressor protein p53. Transient overexpression of human Adx in HCT116 cells leads to ROS production, to a disruption of the mitochondrial transmembrane potential (ΔΨ), to cytochrome c release from the mitochondria, and to caspase activation. In contrast, the effect of transient overexpression of human CYP11A1 on cell viability varies in different cell lines, with some being sensitive and others not. We conclude that mitochondrial cytochrome P450 systems are a source of mitochondrial ROS production and can play a role in the induction of mitochondrial apoptosis.

Keywords: adrenodoxin; apoptosis; CYP11A1; cytochrome P450; electron transfer chain; mitochondria; reactive oxygen species; steroid hydroxylation

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