Jung-Testas I, Weintraub H, Dupuis D, Eychenne B, Baulieu E E, Robel P
INSERM U33, Le Kremlin-Bicêtre, France.
J Steroid Biochem Mol Biol. 1992 Jul;42(6):597-605. doi: 10.1016/0960-0760(92)90450-w.
Newborn rat glial cells in primary culture contain an active cholesterol side chain cleavage cytochrome P450. Cholesterol can be supplied either by biosynthesis or derive from low density lipoproteins (LDL), which bind apolipoprotein Band E (apoB,E) (LDL)-receptors and undergo receptor-mediated endocytosis. Using antibodies to purified human plasma LDL and antibodies to bovine adreno-cortical LDL-receptor, the presence of LDL-receptors was demonstrated on rat glial cells after 3-4 weeks of primary culture, by ligand blotting, immunoblotting, and indirect immunofluorescence staining. The latter approach indicated that oligodendrocytes express higher levels of LDL-receptors than astrocytes present in the same culture. The immunofluorescence staining was observed not only at the cell surface, but also within the cytoplasm, suggesting that the LDL-receptor complexes had been internalized. Western blotting of LDL-receptors extracted from glial cells indicated a band of approximately 130 kDa, the size expected for intact receptors. Their functionality was shown by the conversion of [3H]cholesterol linoleate, incorporated into reconstituted LDL and added to the cell cultures, to [3H]pregnenolone and/or its 20 alpha-hydroxy-metabolite. This is the first characterization of functional LDL-receptors on isolated, well characterized, normal brain cells.
原代培养的新生大鼠神经胶质细胞含有一种活性胆固醇侧链裂解细胞色素P450。胆固醇既可以通过生物合成提供，也可以来源于低密度脂蛋白（LDL），后者与载脂蛋白B和E（apoB，E）（LDL）受体结合，并经历受体介导的内吞作用。使用针对纯化的人血浆LDL的抗体和针对牛肾上腺皮质LDL受体的抗体，通过配体印迹、免疫印迹和间接免疫荧光染色，在原代培养3 - 4周后的大鼠神经胶质细胞上证实了LDL受体的存在。后一种方法表明，少突胶质细胞表达的LDL受体水平高于同一培养物中的星形胶质细胞。免疫荧光染色不仅在细胞表面观察到，在细胞质内也观察到，这表明LDL受体复合物已经被内化。从神经胶质细胞中提取的LDL受体的蛋白质印迹显示出一条约130 kDa的条带，这是完整受体预期的大小。将掺入重组LDL并添加到细胞培养物中的[3H]胆固醇亚油酸酯转化为[3H]孕烯醇酮和/或其20α - 羟基代谢物，证明了它们的功能。这是首次对分离的、特征明确的正常脑细胞上的功能性LDL受体进行表征。
