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R. McGreal, W. Lee, M. Demos, L. Brennan, M. Kantorow; -Crystallin and Cytochrome C Form a Mitochondrial Complex With MsrA in Lens Cells. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1183.
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Oxidation of α -crystallin and cytochrome c (cyt c) at specific methionine residues results in loss of their respective chaperone and oxidoreductase activities. Both α -crystallin and cyt c are oxidized in the lenses of Methionine Sulfoxide Reductase A (MsrA) knockout mice in vivo and their activities are dependent on repair by MsrA. Both cyt c, α -crystallin and MsrA are localized to lens cells suggesting they may form a functional complex in specific lens cell sub-types. Here, we examined possible interactions between α -crystallin and cyt c in lens cells as a first step towards establishing a possible role for α -crystallin and MsrA in modulating the apoptotic and oxidoreductase activities of cyt c.
Levels of cyt c and α -crystallin (total, α A and α B-crystallin) were examined by RT-PCR and western analysis of microdissected mouse and human lenses. Protein complexes were analyzed by co-immune precipitation analysis of extracts from cultured human lens epithelial cells (HLEB3 and SRA04/01) and whole human lenses. Protein complexes were further examined by microdissection of whole human and mouse lenses followed by immunoflourescent microscopy and organelle imaging.
As expected, high levels of α -crystallin, MsrA and cyt c were detected in the lens epithelium. Unexpectedly, significant levels of cyt c were also detected in lens fibers. MsrA, cyt c and α -crystallin formed stable complexes that were detected in all lens tissues. These complexes preferentially resided in lens mitochondria.
These results suggest that MsrA, α -crystallin and cyt c form complexes in lens epithelia and fibers. They suggest that both the oxidative stress repair activity of MsrA and the chaperone function of α -crystallin may modulate the activity of cyt c in the lens affecting both lens mitochondrial function, apoptosis and possibly lens differentiation.
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