Membrane binding sites for plasma lipoproteins on endosomes from rat liver.
Membrane binding sites for plasma lipoproteins on endosomes from rat liver.
复制标题
大鼠肝脏内体上血浆脂蛋白的膜结合位点。
DOI：
10.1073/pnas.86.6.1880
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发表时间：
1989
影响因子：
11.1
通讯作者：
Havel,RJ
中科院分区：
文献类型：
--
作者：
Jaeckle,S;Brady,SE;Havel,RJ
高纯度的大鼠肝内膜富含大量大分子的受体[包括低密度脂蛋白(LDL)受体]，通过包被的Pit/Enosome/Lysosome途径进入肝细胞[包括低密度脂蛋白(LDL)的受体]。在雌激素处理的大鼠肝内膜中，含有载脂蛋白E的脂蛋白的结合部位被多次诱导。其中一个结合位点被30 mM EDTA抑制，通过配基、免疫印迹和其他特征，似乎与低密度脂蛋白受体相同。另一个位点对EDTA高度抵抗，不结合低密度脂蛋白。然而，与EDTA抗性部位的结合很容易被肝素(就像低密度脂蛋白受体一样)以及针对大鼠或牛低密度脂蛋白受体制备的抗血清所抑制。EDTA抗性位点在早期内体、晚期内体和内体衍生的受体循环膜中的分布与低密度脂蛋白受体和其他循环受体的分布相似。低密度脂蛋白受体在未经处理的大鼠肝脏的内体膜中的存在水平约为雌二醇组的10%，但几乎检测不到EDTA抗性部位。在未处理或雌二醇处理的大鼠肝脏内膜上，未检测到不能被低密度脂蛋白受体抗血清抑制的β-VLDL饱和结合。EDTA抗性部位可能是一种修饰的低密度脂蛋白受体，它能识别载脂蛋白E，但不能识别低密度脂蛋白的载脂蛋白B。或者，它可能是一种独特的受体，与低密度脂蛋白受体共享免疫决定因素，专用于内吞含有载脂蛋白E的某些脂蛋白，包括乳糜粒残留物。
Highly purified endosomal membranes from rat liver, enriched in receptors for a number of macromolecules taken up into hepatocytes via the coated pit/endosome/lysosome pathway [including the receptor for low density lipoproteins (LDL)], were used to characterize binding sites for lipoproteins containing apolipoprotein E. In endosomal membranes from livers of estradiol-treated rats, in which LDL receptors are induced manyfold, two high-affinity binding sites were found for two apolipoprotein E-rich lipoproteins: very low density beta-lipoproteins (beta-VLDL) from cholesterol-fed rabbits and rat chylomicron remnants. One of these sites, binding to which is inhibited by 30 mM EDTA, appears identical to the LDL receptor by ligand and immunoblotting and other characteristics. The other site, highly resistant to EDTA, does not bind LDL. Binding to the EDTA-resistant site, however, is readily inhibited by heparin (as is the LDL receptor) and also by antisera prepared against rat or bovine LDL receptor. The distribution of the EDTA-resistant site among early endosomes, late endosomes, and endosome-derived receptor-recycling membranes is similar to that of the LDL receptor and other recycling receptors. The LDL receptor was present in endosomal membranes from livers of untreated rats at about 10% of the level found in membranes from estradiol-treated rats, but the EDTA-resistant site was barely detectable. No saturable binding of beta-VLDL that could not be inhibited by antisera to the LDL receptor could be detected in endosomal membranes from livers of either untreated or estradiol-treated rats. The EDTA-resistant site may be a modified form of the LDL receptor that recognizes apolipoprotein E but not the B apolipoprotein of LDL. Alternatively, it may be a distinct receptor sharing immunological determinants with the LDL receptor, specialized for the endocytosis of certain lipoproteins containing apolipoprotein E, including chylomicron remnants.