title: Site specific oxidation of amino acid residues in rat lens γ-crystallin induced by low-dose γ-irradiation.
abstract: Although cataracts are a well-known age-related disease, the mechanism of their formation is not well understood. It is currently thought that eye lens proteins become abnormally aggregated, initially causing clumping that scatters the light and interferes with focusing on the retina, and ultimately resulting in a cataract. The abnormal aggregation of lens proteins is considered to be triggered by various post-translational modifications, such as oxidation, deamidation, truncation and isomerization, that occur during the aging process. Such modifications, which are also generated by free radical and reactive oxygen species derived from γ-irradiation, decrease crystallin solubility and lens transparency, and ultimately lead to the development of a cataract. In this study, we irradiated young rat lenses with low-dose γ-rays and extracted the water-soluble and insoluble protein fractions. The water-soluble and water-insoluble lens proteins were digested with trypsin, and the resulting peptides were analyzed by LC-MS. Specific oxidation sites of methionine, cysteine and tryptophan in rat water-soluble and -insoluble γE and γF-crystallin were determined by one-shot analysis. The oxidation sites in rat γE and γF-crystallin resemble those previously identified in γC and γD-crystallin from human age-related cataracts. Our study on modifications of crystallins induced by ionizing irradiation may provide useful information relevant to human senile cataract formation.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Ingu
authors.initials: I
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Saito
authors.affiliation: Radioisotope Research Center, Teikyo University, Kaga Itabashi-ku, Tokyo 173-8605, Japan.
authors.forename: Norihiko
authors.initials: N
authors.lastname: Fujii
authors.affiliation: Department of Ophthalmology, Hiroshima Memorial Hospital, Honkawacho, Naka-ku, Hiroshima 730-0802, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kanamoto
authors.affiliation: Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Chatake
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan. Electronic address: nfujii@rri.kyoto-u.ac.jp.
authors.forename: Noriko
authors.initials: N
authors.lastname: Fujii
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D002386:Cataract / Q000209:etiology / Q000378:metabolism; D018360:Crystallography, X-Ray; D005720:Gamma Rays / Q000009:adverse effects*; D006801:Humans; D007908:Lens, Crystalline / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects*; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011487:Protein Conformation; D051381:Rats; D017208:Rats, Wistar; D012995:Solubility; D053719:Tandem Mass Spectrometry; D038222:gamma-Crystallins / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects*
chemical_list: D000596:Amino Acids; D038222:gamma-Crystallins
keywords: Cataract; LC-MS/MS; Low-dose γ-irradiation; Oxidation; ROS; γ-Crystallin