Jonas A, Bottum K, Theret N, Duchateau P, Castro G
Department of Biochemistry, College of Medicine, University of Illinois at Urbana-Champaign 61801.
J Lipid Res. 1994 May;35(5):860-70.
We used defined, reconstituted high density lipoproteins (rHDL) to study the effects of structure and composition of these particles on their role as cholesterol acceptors from cell membranes or from low density lipoproteins (LDL). Three discoidal rHDL and one spherical rHDL with distinct apolipoprotein A-I conformations, diameters and compositions were used in conjunction with Ob1771 cells to measure the rate of [3H]cholesterol efflux from the cells, direct binding to the cells, and competition with native HDL3 for binding. In addition, the same rHDL particles were used to study the kinetics of cholesterol mass transfer from LDL. The results show that the rates of cholesterol transfer depend on the nature of the donor (t1/2 11-19 min from LDL, and t1/2 5 h from the cells), on the phosphatidylcholine/cholesterol ratio in the acceptors (the closer this ratio is to the equilibrium value, the slower is the rate), and on the diameter of the acceptors (the smallest particles have the lowest t1/2 for cholesterol uptake from LDL, and are the most effective acceptors of [3H]cholesterol from cells after their phospholipid content is taken into account). The cholesterol uptake by the rHDL, both from the cells and from LDL, is determined mostly by the phospholipid pool available in the acceptors. Binding to the cells was equivalent for all the rHDL (Kd = 38-67 micrograms/ml) and comparable to HDL3, suggesting that the differences in apoA-I conformation have no effect on the binding to cells. Finally we observed that exposure of rHDL to cells may lead to remodeling of some of the lipoprotein particles.
我们使用经过定义的、重组的高密度脂蛋白（rHDL）来研究这些颗粒的结构和组成对其作为细胞膜或低密度脂蛋白（LDL）中胆固醇受体的作用的影响。使用了三种盘状rHDL和一种具有不同载脂蛋白A-I构象、直径和组成的球状rHDL，结合Ob1771细胞来测量[3H]胆固醇从细胞中的流出速率、与细胞的直接结合以及与天然HDL3竞争结合。此外，使用相同的rHDL颗粒来研究胆固醇从LDL的质量转移动力学。结果表明，胆固醇转移速率取决于供体的性质（从LDL转移的半衰期为11 - 19分钟，从细胞转移的半衰期为5小时）、受体中磷脂酰胆碱/胆固醇的比例（该比例越接近平衡值，速率越慢）以及受体的直径（最小的颗粒从LDL摄取胆固醇的半衰期最短，并且在考虑其磷脂含量后，是从细胞中摄取[3H]胆固醇最有效的受体）。rHDL从细胞和LDL摄取胆固醇主要由受体中可用的磷脂池决定。所有rHDL与细胞的结合相当（Kd = 38 - 67微克/毫升），且与HDL3相当，这表明载脂蛋白A-I构象的差异对与细胞的结合没有影响。最后，我们观察到rHDL与细胞接触可能导致一些脂蛋白颗粒发生重塑。
