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D.A. Ferrington, R.J. Kapphahn, C.M. Ethen, L. Higgins, E.A. Peters; Age-Related Posttranslational Modifications of Crystallins in Rat Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1601.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Crystallins are small heat shock proteins with chaperone-like function that prevent heat and oxidative stress-induced aggregation of misfolded proteins. It has been reported that crystallins undergo age-related posttranslational modifications in the lens. These modifications can disrupt the conformation of the protein and alter chaperone function. Here we describe for the first time posttranslational modifications of crystallins in the rat retina. Methods: Retinal homogenates from young and old F344BN rats were analyzed for posttranslational modifications using 2D gel electrophoresis and immunochemical detection of phosphoserine, acetylated lysine, and 4-hydroxy-2-nonenal adducts on proteins. Protein identification was achieved by enzymatic digestion followed by MALDI-TOF mass spectrometry of extracted peptides. Protein identification was confirmed by MS/MS sequencing of peptides. Results: In this study, we identified posttranslational modifications in alpha A, alpha B, and beta B2 crystallin, including oxidation, phosphorylation, and acetylation. For each crystallin, one major spot and many additional spots with altered migration, indicative of changes in intrinsic charge and/or mass from that of the major spot, were observed. Spots with the same mass, but altered charge migrated as more acidic species. The chemical modifications observed here alter the net charge of the protein, which accounts for the appearance of these acidic species. Truncated forms were observed as spots with altered mass. Age-related differences were observed for each crystallin in the number of spots with altered migration as well as the type of posttranslational modification detected. Conclusions: In the rat retina, alpha A, alpha B, and beta B2 crystallin exhibit increased age-related posttranslational modifications. The increased amount of chemically modified crystallins suggests there is less protection from stress-induced protein aggregation in aged retina.
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