Functional and structural properties of lipid-associated apolipoprotein J (clusterin)
Functional and structural properties of lipid-associated apolipoprotein J (clusterin)
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DOI：
10.1042/0264-6021:3440375
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发表时间：
1999-12-01
影响因子：
4.1
通讯作者：
Ghiso, J
中科院分区：
文献类型：
--
作者：
Calero, M;Tokuda, T;Ghiso, J
载脂蛋白J （apoJ, clusterin）是一种与血浆和脑脊液中的脂质相关的多功能蛋白，由肝细胞和星形胶质细胞以脂质颗粒的形式分泌。为了研究apoJ的结构和功能特性是否在与脂质结合后被调节，我们使用合成或血浆HDL衍生的脂质制备了apoJ高密度脂蛋白（HDL）样颗粒。所得的大多数脂质颗粒每个颗粒含有一个apoJ分子，并表现出与含apoJ的血浆HDL相同的α 2电泳迁移特性。颗粒大小似乎取决于脂质混合物中胆固醇的存在，其直径范围从存在胆固醇时的10纳米到不存在胆固醇时的20纳米。CD分析和傅里叶变换红外光谱分析显示，apoJ与脂质颗粒结合后二级结构发生了类似的变化，即α -螺旋含量减少，β -转结构增加。两项功能测试，即与阿尔茨海默病淀粉样蛋白β肽的结合相互作用和补体膜攻击复合物的抑制活性，均未发现apoJ活性在脂化后发生任何变化（P < 0.05）。与脂质结合后，与细胞受体meggalin的结合亲和力显著增强（P < 0.01）；K-d值从降解形式的78.8 +/- 10.7 nM降至apoJ-HDL的37.0 +/- 7.3 nM。虽然尚不清楚观察到的结构变化是否直接导致了更高的受体结合亲和力，但数据表明，补体抑制和淀粉样蛋白β结合基元位于与apoj - meggalin相互作用相关的分子区域不同。
Apolipoprotein J (apoJ, clusterin) is a multifunctional protein normally associated with lipids in plasma and cerebrospinal fluid, and secreted as lipoparticles by hepatocytes and astrocytes. To investigate whether the structural and functional properties of apoJ are modulated upon binding to lipids, we prepared apoJ high-density lipoprotein (HDL)-like particles employing either synthetic or plasma HDL-derived lipids. The majority of the resulting lipoparticles contained one molecule of apoJ per particle and exhibited the same alpha 2 electrophoretic mobility characteristic of apoJ-containing plasma HDL. Particle size seemed to be dependent on the presence of cholesterol in the lipid mixture and ranged from diameters of 10 nm in the presence of cholesterol to 20nm in the absence of cholesterol. CD analysis and Fourier-transform infrared spectroscopy revealed similar changes in the apoJ secondary structure induced by its incorporation into lipoparticles, namely a decrease in alpha-helix content and an increase in beta-turn structures. Two functional assays, the binding interaction with Alzheimer's amyloid beta peptides and the inhibitory activity of the complement membrane-attack complex, did not detect any changes in apoJ activity following its lipidation (P > 0.05). On the contrary, the binding affinity to the cellular receptor megalin was enhanced significantly (P < 0.01) after the association with lipids; the K-d value decreased from 78.8 +/- 10.7 nM for the delipidated form to 37.0 +/- 7.3 nM for apoJ-HDL. Although it is not known whether the structural changes observed are directly responsible for the higher receptor-binding affinity, the data suggest that the complement inhibition and amyloid beta-binding motifs are located in areas of the molecule different from those involved in the apoJ-megalin interaction.