Abstract
Purpose: :
αB-crystallin is known to be involved in oxidative stress protection of lens and retinal cells. The mechanism underlying this protection is not fully elucidated. Here, we examined the potential for αB-crystallin to preserve mitochondrial function under oxidative stress conditions.
Methods: :
Relative chaperone activities of WT αB, αB-R120G and αB-M68A mutants were measured using different substrates against heat and chemical denaturation. WT αB, αB-R120G and αB-M68A overexpressing ARPE 19 and HLE B3 cells lines were produced and the sub-cellular localization and mitochondrial function of the resulting cell lines were examined with or without oxidative stress treatment. Inter-cellular protein aggregation was also examined in these cell lines to estimate the in vivo chaperone activities of each αB-crystallin mutant. Interactions of the mutants with cytochrome c as a mitochondrial marker were also tested in vivo by fluorescent resonance energy transfer and in vitro by measuring cytochrome c activity.
Results: :
αB-crystallin is found at high levels in the mitochondria in lens and retinal cells. αB-crystallin specifically translocates to the mitochondria under oxidative conditions. Over-expression of αB-crystallin protects mitochondrial function under oxidative stress conditions. αB-crystallin specifically interacts with cytochrome c in vivo and protects cytochrome c against in vitro oxidation of methionine 80 thereby preserving its electron transport function.
Conclusions: :
These data demonstrate that αB-crystallin preserves mitochondrial function under oxidative stress conditions by protecting cytochrome c against oxidative inactivation. These results provide insight into the role of αB-crystallin in oxidative stress protection in multiple tissues and in the prevention of oxidative stress-associated disorders including cataract and age-related macular degeneration.
Keywords: chaperones • oxidation/oxidative or free radical damage • mitochondria