MECHANISM OF ACTIVATION AND FUNCTIONAL-SIGNIFICANCE OF THE LIPOLYSIS-STIMULATED RECEPTOR - EVIDENCE FOR A ROLE AS CHYLOMICRON REMNANT RECEPTOR
MECHANISM OF ACTIVATION AND FUNCTIONAL-SIGNIFICANCE OF THE LIPOLYSIS-STIMULATED RECEPTOR - EVIDENCE FOR A ROLE AS CHYLOMICRON REMNANT RECEPTOR
复制标题
DOI：
10.1021/bi00033a014
复制
发表时间：
1995-08-22
期刊：
影响因子：
2.9
通讯作者：
BIHAIN, BE
中科院分区：
文献类型：
--
作者：
MANN, CJ;KHALLOU, J;BIHAIN, BE
在培养的人和大鼠细胞中，当被游离脂肪酸（FFA）激活时，脂解刺激受体（LSR）介导含载脂蛋白B和载脂蛋白E的脂蛋白的结合以及它们随后的内化和降解。为了更好地了解LSR的生理作用，我们开发了一种生化测定，该测定优化了活化和结合步骤，从而允许估计活体动物肝脏中表达的LSR结合位点的数量。用这种技术，发现大鼠肝脏中LSR结合位点的表观数量与餐后血浆甘油三酯浓度之间存在强的负相关（r =-0.828，p < 0.001，n = 12）。在禁食24小时后，在同一动物中测量的LSR和血浆甘油三酯的数量之间不存在相关性。同样的膜结合试验用于阐明FFA诱导脂蛋白与LSR结合的机制。LSR激活步骤介导的FFA与LSR候选蛋白的表观分子量为115和90 kDa的直接相互作用，并发生独立的膜脂质环境。FFA诱导的构象转变，揭示了脂蛋白结合位点仍然完全可逆的FFA去除后。然而，由载脂蛋白配体占据的位点稳定了LSR的活性形式。单独或组合的不同FFA的效果的比较表明，相同的结合位点被不同的FFA揭示，并且FFA单体碳链的长度和饱和度在确定FFA活化效果的效力中是关键的。我们提出，LSR途径代表了一个限制性步骤的细胞摄取的naturally衍生的富含磷脂酰肌醇的脂蛋白，并推测FFA释放的脂解启动这一过程，通过改变LSR的构象，揭示脂蛋白结合位点。
In cultured human and rat cells, the lipolysis-stimulated receptor (LSR), when activated by free fatty acids (FFA), mediates the binding of apoprotein B- and apoprotein E-containing lipoproteins and their subsequent internalization and degradation. To better understand the physiological role of LSR, we developed a biochemical assay that optimizes both the activation and binding steps and, thus, allows the estimation of the number of LSR binding sites expressed in the livers of living animals. With this technique, a strong inverse correlation was found in rats between the apparent number of LSR binding sites in liver and the postprandial plasma triglyceride concentration (r = -0.828, p < 0.001, n = 12). No correlation existed between the number of LSR and plasma triglycerides measured in the same animals after 24 h of fasting. The same membrane binding assay was used to elucidate the mechanism by which FFA induce lipoprotein binding to LSR. The LSR activation step was mediated by direct interaction of FFA with LSR candidate proteins of apparent molecular masses of 115 and 90 kDa and occurred independently of the membrane lipid environment. The FFA-induced conformational shift that revealed the lipoprotein binding site remained fully reversible upon removal of the FFA. However, occupancy of the site by the apoprotein ligand stabilized the active form of LSR. Comparison of the effect of different FFA alone or in combination indicated that the same binding site is revealed by different FFA and that the length and saturation of the FFA monomeric carbon chain are critical in determining the potency of the FFA activating effect. We propose that the LSR pathway represents a limiting step for the cellular uptake of intestinally derived triglyceride-rich lipoproteins and speculate that FFA liberated by lipolysis initiate this process by altering the conformation of LSR to reveal the lipoprotein binding site.