Cholesterol-derived bile acids enhance the chaperone activity of α-crystallins.
Cholesterol-derived bile acids enhance the chaperone activity of α-crystallins.
复制标题
胆固醇衍生的胆汁酸增强α-晶状体蛋白的伴侣活性。
DOI：
10.1007/s12192-011-0259-5
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发表时间：
2011
影响因子：
3.8
通讯作者：
Shinohara,Toshimichi
中科院分区：
文献类型：
--
作者：
Song,Shuhua;Liang,JackJN;Mulhern,MichaelL;Madson,ChristianJ;Shinohara,Toshimichi
人类晶状体膜的胆固醇浓度是已知生物膜中最高的，但随着年龄的增长，胆固醇浓度显著下降。胆固醇的氧合作用会产生多种形式的氧化甾醇(胆汁酸)。我们之前已经证明了两种形式的胆汁酸成分-熊去氧胆酸(UDCA)和牛磺熊去氧胆酸(TUDCA)-抑制半乳糖血症大鼠晶状体上皮细胞的死亡，并减轻白内障的形成。我们研究了这些化合物是否也抑制了人类晶状体晶体蛋白的热聚集。从人晶状体中提取总水溶蛋白，利用原核表达系统获得重组人晶状体蛋白(αA-、αB-、βB2-和γC-晶状体蛋白)，并用高效液相色谱分离纯化。使用位于Ex/Em = 400/400 nm的荧光分光计测量了蛋白质在存在或不存在UDCA或TUDCA的情况下的光散射。蛋白印迹法检测人晶状体WS蛋白中α-晶体蛋白的表达。高浓度的UDCA和TUDCA显著抑制含低水平αA/αB-晶状体蛋白的总WS蛋白的热聚集。对每个重组人晶状体蛋白的光谱分析表明，胆汁酸不能抑制γC-、βB2-、αA-或αB-晶体蛋白的热聚集。α-晶状体蛋白和胆汁酸(UDCA或TUDCA)的结合抑制了每个单独的晶状体蛋白以及非晶状体蛋白胰岛素的热聚集。这些结果提示，UDCA或TUDCA对α-晶状体蛋白的伴侣活性有保护作用。据认为，晶状体中这两种天然产生的中间废物增强了α-晶状体蛋白的伴侣活性。这一发现可能导致UDCA和TUDCA作为抗白内障药物的发展。
Human lens membranes contain the highest cholesterol concentration of any known biological membranes, but it significantly decreases with age. Oxygenation of cholesterol generates numerous forms of oxysterols (bile acids). We previously showed that two forms of the bile acid components—ursodeoxycholic acid (UDCA) and tauroursodeoxycholic acid (TUDCA)—suppressed lens epithelial cell death and alleviated cataract formation in galactosemic rat lenses. We investigated whether these compounds also suppress the thermal aggregation of human lens crystallins. Total water-soluble (WS) proteins were prepared from human lenses, and recombinant human crystallins (αA-, αB-, βB2-, and γC-crystallin) were generated by a prokaryotic expression system and purified by liquid chromatography. The light scattering of proteins in the presence or absence of UDCA or TUDCA was measured using a spectrofluorometer set at Ex/Em = 400/400 nm. Protein blot analysis was conducted for detection of α-crystallins in the human lens WS proteins. High concentrations of UDCA and TUDCA significantly suppressed thermal aggregation of total lens WS proteins, which contained a low level of αA-/αB-crystallin. Spectroscopic analysis with each recombinant human lens crystallin indicated that the bile acids did not suppress the thermal aggregation of γC-, βB2-, αA-, or αB-crystallin. Combination of α-crystallin and bile acid (either UDCA or TUDCA) suppressed thermal aggregation of each individual crystallin as well as a non-crystallin protein, insulin. These results suggest that UDCA or TUDCA protects the chaperone activity of α-crystallin. It is believed that these two naturally occurring intermediate waste products in the lens enhance the chaperone activity of α-crystallin. This finding may lead to the development of UDCA and TUDCA as anticataract agents.