Mitochondrial respiratory chain and thioredoxin reductase regulate intermembrane Cu,Zn-superoxide dismutase activity: implications for mitochondrial energy metabolism and apoptosis
2007
IMS (intermembrane space) SOD1 (Cu/Zn-superoxide dismutase) is inactive in isolated intact rat liver mitochondria and is activated following oxidative modification of its critical thiol groups. The present study aimed to identify biochemical pathways implicated in the regulation of IMS SOD1 activity and to assess the impact of its functional state on key mitochondrial events. Exogenous H 2 O 2 (5 μM) activated SOD1 in intact mitochondria. However, neither H 2 O 2 alone nor H 2 O 2 in the presence of mitochondrial peroxiredoxin III activated SOD1, which was purified from mitochondria and subsequently reduced by dithiothreitol to an inactive state. The reduced enzyme was activated following incubation with the superoxide generating system, xanthine and xanthine oxidase. In intact mitochondria, the extent and duration of SOD1 activation was inversely correlated with mitochondrial superoxide production. The presence of TxrR-1 (thioredoxin reductase-1) was demonstrated in the mitochondrial IMS by Western blotting. Inhibitors of TxrR-1, CDNB (1-chloro-2,4-dinitrobenzene) or auranofin, prolonged the duration of H 2 O 2 -induced SOD1 activity in intact mitochondria. TxrR-1 inactivated SOD1 purified from mitochondria in an active oxidized state. Activation of IMS SOD1 by exogenous H 2 O 2 delayed CaCl 2 -induced loss of transmembrane potential, decreased cytochrome c release and markedly prevented superoxide-induced loss of aconitase activity in intact mitochondria respiring at state-3. These findings suggest that H 2 O 2 , superoxide and TxrR-1 regulate IMS SOD1 activity reversibly, and that the active enzyme is implicated in protecting vital mitochondrial functions.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
33
References
62
Citations
NaN
KQI