Nykjaer A, Nielsen M, Lookene A, Meyer N, Røigaard H, Etzerodt M, Beisiegel U, Olivecrona G, Gliemann J
Department of Medical Biochemistry, University of Aarhus, Denmark.
J Biol Chem. 1994 Dec 16;269(50):31747-55.
It has previously been shown that lipoprotein lipase can mediate uptake of remnant lipoprotein particles via binding to the low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor (LRP). Binding of lipoprotein lipase, and of triglyceride-rich lipoproteins associated with the lipase, to LRP depends on an intact carboxyl-terminal folding domain of the lipase (Nykjaer, A., Bengtsson-Olivecrona, G., Lookene, A., Moestrup, S. K., Petersen, C. M., Weber, W., Beisiegel, W., and Gliemann, J. (1993) J. Biol. Chem. 268, 15048-15055). Here we show that the site for binding to the receptor is within residues 380-425 of the bovine and residues 378-423 of the human lipoprotein lipase. We demonstrate that a carboxyl-terminal fragment of human lipoprotein lipase (residues 378-448), expressed as fusion protein in Escherichia coli, binds to purified and cellular LRP but not to lipoproteins. Binding of the fragment to purified LRP was blocked by heparin. In addition, the fragment inhibited the binding of lipase and the lipase-mediated binding of lipoproteins to the purified receptor. The fragment exhibited reduced binding to proteoglycan-deficient cells. Moreover, the fragment inhibited the uptake of lipoproteins in cells mediated by the lipase via binding to heparan sulfate proteoglycans and LRP. We conclude that the fragment contains the site for binding to LRP and a candidate site for interaction with heparan sulfate proteoglycans, whereas binding to lipoproteins is inefficient. The fragment can therefore inhibit the lipase-mediated lipoprotein uptake, a process that may promote the development of atherosclerosis when occurring in cells of the arterial wall.
先前的研究表明，脂蛋白脂肪酶可通过与低密度脂蛋白受体相关蛋白/α2-巨球蛋白受体（LRP）结合来介导残余脂蛋白颗粒的摄取。脂蛋白脂肪酶以及与该脂肪酶相关的富含甘油三酯的脂蛋白与LRP的结合取决于脂肪酶完整的羧基末端折叠结构域（尼克耶尔，A.，本特松-奥利韦克隆纳，G.，洛克内，A.，莫斯特鲁普，S.K.，彼得森，C.M.，韦伯，W.，贝西格尔，W.，和格利曼，J.（1993年）《生物化学杂志》268卷，15048 - 15055页）。在此我们表明，牛脂蛋白脂肪酶的380 - 425位残基以及人脂蛋白脂肪酶的378 - 423位残基是与受体结合的位点。我们证明，人脂蛋白脂肪酶的羧基末端片段（378 - 448位残基）在大肠杆菌中作为融合蛋白表达，它能与纯化的和细胞中的LRP结合，但不与脂蛋白结合。该片段与纯化的LRP的结合被肝素阻断。此外，该片段抑制脂肪酶以及脂肪酶介导的脂蛋白与纯化受体的结合。该片段与蛋白聚糖缺陷细胞的结合减少。而且，该片段通过与硫酸乙酰肝素蛋白聚糖和LRP结合，抑制脂肪酶介导的细胞内脂蛋白摄取。我们得出结论，该片段包含与LRP结合的位点以及与硫酸乙酰肝素蛋白聚糖相互作用的候选位点，而与脂蛋白的结合效率较低。因此，该片段可抑制脂肪酶介导的脂蛋白摄取，当这一过程发生在动脉壁细胞中时，可能会促进动脉粥样硬化的发展。
