Voltage-dependent anion channels control the release of the superoxide anion from mitochondria to cytosol - PubMed (original) (raw)

. 2003 Feb 21;278(8):5557-63.

doi: 10.1074/jbc.M210269200. Epub 2002 Dec 12.

Affiliations

Free article

Voltage-dependent anion channels control the release of the superoxide anion from mitochondria to cytosol

Derick Han et al. J Biol Chem. 2003.

Free article

Abstract

Several reactions in biological systems contribute to maintain the steady-state concentrations of superoxide anion (O(2)*-) and hydrogen peroxide (H(2)O(2)). The electron transfer chain of mitochondria is a well documented source of H(2)O(2); however, the release of O(2)*- from mitochondria into cytosol has not been unequivocally established. This study was aimed at validating mitochondria as sources of cytosolic O(2)*-, elucidating the mechanisms underlying the release of O(2)*- from mitochondria into cytosol, and assessing the role of outer membrane voltage-dependent anion channels (VDACs) in this process. Isolated rat heart mitochondria supplemented with complex I or II substrates generate an EPR signal ascribed to O(2)*-. Inhibition of the signal in a concentration-dependent manner by both manganese-superoxide dismutase and cytochrome c proteins that cannot cross the mitochondrial membrane supports the extramitochondrial location of the spin adduct. Basal rates of O(2)*- release from mitochondria were estimated at approximately 0.04 nmol/min/mg protein, a value increased approximately 8-fold by the complex III inhibitor, antimycin A. These estimates, obtained by quantitative spin-trapping EPR, were confirmed by fluorescence techniques, mainly hydroethidine oxidation and horseradish peroxidase-based p-hydroxyphylacetate dimerization. Inhibitors of VDAC, 4'-diisothiocyano-2,2'-disulfonic acid stilbene (DIDS), and dextran sulfate (in a voltage-dependent manner) inhibited O(2)*- production from mitochondria by approximately 55%, thus suggesting that a large portion of O(2)*- exited mitochondria via these channels. These findings are discussed in terms of competitive decay pathways for O(2)*- in the intermembrane space and cytosol as well as the implications of these processes for modulating cell signaling pathways in these compartments.

PubMed Disclaimer

Similar articles

Cited by

Publication types

MeSH terms

Substances

LinkOut - more resources