Patel S C, Asotra K, Patel Y C, McConathy W J, Patel R C, Suresh S
Department of Neurology, University of Connecticut Health Center, Farmington, USA.
Neuroreport. 1995 Mar 7;6(4):653-7. doi: 10.1097/00001756-199503000-00017.
Expression of the lipophilic ligand transporter, apolipoprotein D (apoD) by primary astrocyte cultures derived from neonatal mouse brain was investigated. Western blot analysis of cell lysates and media showed that apoD is constitutively secreted by astrocytes with little intracellular storage. The secreted apoD floated primarily at density 1.063-1.21 g ml-1 upon sequential ultracentrifugation indicating its association with lipids. Treatment of astrocytes with the carboxylic ionophore, monensin, resulted in intracellular retention and decreased secretion of apoD that was of slightly reduced M(r). Progesterone, a steroid hormone that binds to apoD with high affinity (10(-6) mol l-1) and the oxysterol, 25-hydroxycholesterol which is a potent regulator of cellular cholesterol homeostasis in mammalian cells, differentially stimulated apoD, but not apoE secretion. These results show that astrocytes synthesize and constitutively secrete apoD and suggest a physiologic role for this lipocalin in cholesterol metabolism in the nervous system.
对源自新生小鼠脑的原代星形胶质细胞培养物中亲脂性配体转运蛋白载脂蛋白D（apoD）的表达进行了研究。对细胞裂解物和培养基的蛋白质免疫印迹分析表明，apoD由星形胶质细胞组成性分泌，细胞内储存很少。经连续超速离心后，分泌的apoD主要漂浮在密度为1.063 - 1.21 g/ml处，表明其与脂质相关。用羧酸离子载体莫能菌素处理星形胶质细胞，导致apoD在细胞内潴留且分泌减少，其相对分子质量略有降低。孕酮是一种与apoD具有高亲和力（10⁻⁶ mol/l）的甾体激素，以及25 - 羟基胆固醇这种在哺乳动物细胞中是细胞胆固醇稳态的有效调节剂的氧化甾醇，它们对apoD的分泌有不同的刺激作用，但对apoE的分泌无刺激作用。这些结果表明，星形胶质细胞合成并组成性分泌apoD，并提示这种脂质运载蛋白在神经系统胆固醇代谢中具有生理作用。
