Shearer T R, Azuma M, David L L, Murachi T
Department of Biochemistry, School of Dentistry, Oregon Health Sciences University, Portland 97201.
Invest Ophthalmol Vis Sci. 1991 Mar;32(3):533-40.
Cataracts were produced in cultured rat lenses by either 10 microM calcium ionophore A23187, 25 microM sodium selenite, or 30 mM xylose. E64, an inhibitor of cysteine proteases, such as calpain (EC, 3.4.22.17), reduced severity of cataract and proteolysis of crystallins when included at a 500 microM concentration in the culture medium along with cataractogenic agents. Calpain II enzyme activity and the amount of calpain antigen were decreased in the cytosol of cataractous lens. However, E64 caused an increase in the amount of an 80-kD calpain subunit associated with the ethyleneglycol-bis-(beta-aminoethylether) tetraacetic acid/ethylenediaminetetraacetic acid-washed insoluble proteins when lenses were incubated with cataractous agents. These data indicate that E64 was at least partially effective in inhibiting lens calpain, and that activation of lens calpain may involve binding to the insoluble fraction. These results provide strong evidence for the activation of calpain in rodent cataracts and suggest testing inhibitors of calpain as anticataract drugs.
通过10微摩尔的钙离子载体A23187、25微摩尔的亚硒酸钠或30毫摩尔的木糖在培养的大鼠晶状体中诱导产生白内障。E64是一种半胱氨酸蛋白酶抑制剂，如钙蛋白酶（EC，3.4.22.17），当在培养基中与致白内障剂一起以500微摩尔的浓度存在时，可降低白内障的严重程度并减少晶状体蛋白的蛋白水解。在白内障晶状体的细胞质中，钙蛋白酶II的酶活性和钙蛋白酶抗原的量减少。然而，当晶状体与致白内障剂一起孵育时，E64导致与乙二醇双（β-氨基乙基醚）四乙酸/乙二胺四乙酸洗涤的不溶性蛋白质相关的80-kD钙蛋白酶亚基的量增加。这些数据表明E64在抑制晶状体钙蛋白酶方面至少部分有效，并且晶状体钙蛋白酶的激活可能涉及与不溶性部分的结合。这些结果为啮齿动物白内障中钙蛋白酶的激活提供了有力证据，并建议测试钙蛋白酶抑制剂作为抗白内障药物。
