The oxidized thiol proteome in aging and cataractous mouse and human lens revealed by ICAT labeling

Abstract

SummaryAge‐related cataractogenesis is associated with disulfide‐linked high molecular weight (HMW) crystallin aggregates. We recently found that the lens crystallin disulfidome was evolutionarily conserved in human and glutathione‐depleted mouse (LEGSKO) cataracts and that it could be mimicked by oxidation in vitro (Mol. Cell Proteomics, 14, 3211‐23 (2015)). To obtain a comprehensive blueprint of the oxidized key regulatory and cytoskeletal proteins underlying cataractogenesis, we have now used the same approach to determine, in the same specimens, all the disulfide‐forming noncrystallin proteins identified by ICAT proteomics. Seventy‐four, 50, and 54 disulfide‐forming proteins were identified in the human and mouse cataracts and the in vitro oxidation model, respectively, of which 17 were common to all three groups. Enzymes with oxidized cysteine at critical sites include GAPDH (hGAPDH, Cys247), glutathione synthase (hGSS, Cys294), aldehyde dehydrogenase (hALDH1A1, Cys126 and Cys186), sorbitol dehydrogenase (hSORD, Cys140, Cys165, and Cys179), and PARK7 (hPARK7, Cys46 and Cys53). Extensive oxidation was also present in lens‐specific intermediate filament proteins, such as BFSP1 and BFSP12 (hBFSP1 and hBFSP12, Cys167, Cys65, and Cys326), vimentin (mVim, Cys328), and cytokeratins, as well as microfilament and microtubule filament proteins, such as tubulin and actins. While the biological impact of these modifications for lens physiology remains to be determined, many of these oxidation sites have already been associated with either impaired metabolism or cytoskeletal architecture, strongly suggesting that they have a pathogenic role in cataractogenesis. By extrapolation, these findings may be of broader significance for age‐ and disease‐related dysfunctions associated with oxidant stress.

DJ-1 in Ocular Diseases: A Review

“…The above results indicate that DJ-1 is a significant oxidation site in the lens via the disulfide cross-linking 25 .…”

Dynamic disulfide exchange in a crystallin protein in the human eye lens promotes cataract-associated aggregation

“…Conversely, previous research also identified other nonnative internal disulfides in cataractous lenses, particularly in ␤-crystallins (57,59), as well as one such bond in the lens-specific chaperone ␣A-crystallin, which appeared to diminish its chaperone activity as well as contribute to aggregation (60,96). More recently, many disulfide bonds were discovered in noncrystallin proteins in the lens (97). It is possible that many of these longlived lens proteins fall within the redox "hot potato" model we have proposed.…”

“…What, then, is the possible fitness benefit of these sequenceproximal and likely redox-active disulfides? A possible explanation is that GSH levels become depleted in lens tissue during aging (50), and the lens core gradually becomes impermeable even to GSH generated in the lens cortex or present in vitreous humor (62), resulting in increased disulfide formation in lens cytoplasmic proteins (97). The ␥-crystallins have always been thought of as purely structural proteins with no known biochemical function aside from their structural stability and optical properties (42,43,48).…”

Conformational catalysis of cataract-associated aggregation in a human eye lens crystallin occurs via interface stealing

“…Human γD-crystallin is extremely thermodynamically and kinetically stable, likely an evolutionary adaptation to resist aggregation (17,25,(28)(29)(30). However, crystallins accumulate damage throughout life, even as the cytoplasm of aged lens cells becomes increasingly oxidizing (31)(32)(33)(34)(35)(36)(37)(38). Eventually, aggregation-prone partially unfolded intermediates arise, notably those locked by non-native disulfides (35,(39)(40)(41)(42)(43)(44)(45).…”