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Rebecca S. McGreal, Lisa A. Brennan, Wanda Lee, Daniel Chauss, Marc Kantorow; α-crystallin Protects Against Apoptosis In Lens Cells By Directly Protecting Cytochrome C Against Methionine Oxidation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5290.
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α-crystallin is involved in multiple anti-apoptotic pathways. To date, those specific interactions between α-crystallin and other apoptotic components that modulate initiation of apoptosis have not been fully elucidated. Oxidation of cytochrome c (cyt c) at methionine 80 (met 80) is an essential step in the initiation of the intrinsic apoptotic pathway and we have previously demonstrated that MsrA repairs methionine oxidized cyt c and methionine oxidized α-crystallin suggesting a direct interaction between these proteins. Here, we examined the existence of functional complexes between cyt c, αA- and αB-crystallins and we tested the ability of α-crystallin to directly protect cyt c against met 80 oxidation which is the initiating step in the activation of the cyt c-mediated apoptotic pathway.
Levels and complex formation of α-crystallin (total, αA- and αB-) and cyt c were examined by western blot analysis of sub-cellular protein fractions and by fluorescent immune co-localization microscopy of cultured human lens epithelial cells (HLEB3). The ability of α-crystallin (total, αA- and αB-) to directly protect cyt c against met 80 oxidation was also monitored by peptide mapping, absorbance spectroscopy and cyt c peroxidase assays.
Both αA- and αB- crystallins were found to co-localize with cyt c in the mitochondria of HLE cells. Total, α- and αB-crystallin all protected cyt c against met 80 oxidation and subsequent gain of cyt c peroxidase activity.
These results demonstrate that α-crystallin and cyt c form functional complexes in lens cell mitochondria and that α-crystallin can protect cyt c against met 80 oxidation which is a key step in cyt c-initiated apoptosis. These results also suggest that α-crystallin plays a key role in mitochondrial protection of specific cyt c oxidation that initiates apoptosis in the lens and other tissues when protection by α-crystallin is lost.
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