Ness Gene C, Kohlruss Nora, Gertz Karen R
Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd., Tampa, FL 33612, USA.
Biochem Biophys Res Commun. 2003 Mar 28;303(1):177-81. doi: 10.1016/s0006-291x(03)00319-x.
The association of the low-density lipoprotein (LDL) receptor with detergent resistant hepatic membranes was investigated using discontinuous sucrose gradients. In liver homogenates from both hamsters and rats, the fractions with the highest concentrations of LDL receptor coincided with the location of caveolin-1, a marker of the cholesterol-rich caveolae. Feeding the animals diets enriched in cholesterol slightly shifted both LDL receptor and caveolin-1 to positions of lower density. The cholesterol content of the caveolae fractions was increased 2-fold in animals fed cholesterol-supplemented diets. In homogenates of CHO cells, fractionated in the same manner, the LDL receptor was absent from the caveolae fractions but was present in denser fractions near the bottom of the gradient. Addition of caveolin-1 antibody to solubilized caveolae from liver coimmunoprecipitated the LDL receptor. These observations suggest that in liver, the LDL receptor is mainly located in caveolae. This location contrasts with the clathrin-coated pit location observed in fibroblasts and CHO cells.
利用不连续蔗糖梯度研究了低密度脂蛋白（LDL）受体与抗去污剂肝细胞膜的关联。在仓鼠和大鼠的肝脏匀浆中，LDL受体浓度最高的组分与富含胆固醇的小窝标记物小窝蛋白-1的位置一致。给动物喂食富含胆固醇的饮食会使LDL受体和小窝蛋白-1都略微向低密度位置移动。在喂食补充胆固醇饮食的动物中，小窝组分的胆固醇含量增加了2倍。在以相同方式分级分离的CHO细胞匀浆中，小窝组分中不存在LDL受体，但在梯度底部附近密度较高的组分中存在。向来自肝脏的溶解小窝中添加小窝蛋白-1抗体可共免疫沉淀LDL受体。这些观察结果表明，在肝脏中，LDL受体主要位于小窝中。这一位置与在成纤维细胞和CHO细胞中观察到的网格蛋白包被小窝位置形成对比。
