Solubilization of apolipoprotein B and its specific binding by the cellular receptor for low density lipoprotein.
Solubilization of apolipoprotein B and its specific binding by the cellular receptor for low density lipoprotein.
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载脂蛋白 B 的溶解及其与低密度脂蛋白细胞受体的特异性结合。
DOI：
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发表时间：
1977
影响因子：
11.1
通讯作者：
W. Fisher
中科院分区：
文献类型：
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作者：
R. Shireman;L. L. Kilgore;W. Fisher
低密度脂蛋白（LDL）和极低密度脂蛋白（VLDL）与成纤维细胞上的受体特异性结合，并且已经假定LDL的载脂蛋白（载脂蛋白B）赋予细胞结合的特异性。这个假设已经在目前的研究中用水溶性载脂蛋白b -牛血清白蛋白复合物进行了测试。（125） i标记的载脂蛋白B与培养成纤维细胞的结合是温度依赖性的。特异性结合范围为183 ~ 859 ng/mg，浓度为5 mug/ml；37℃时，750 ~ 2199 ng/mg被结合并内化。在同一实验中，载脂蛋白B在4度和37度的结合量大大超过（125）i标记LDL的结合量。来自高β -脂蛋白血症纯合子的成纤维细胞显示（125）i标记LDL的结合很少，与细胞LDL受体的缺失一致。这些细胞也抑制了（125）i标记的载脂蛋白b的结合。在缺乏脂蛋白的培养基中生长的淋巴细胞显示出LDL的特异性结合；然而，新鲜分离的淋巴细胞没有表现出这种结合。（125） i标记的载脂蛋白B与淋巴细胞的结合与（125）i标记的LDL的结合平行。未标记的LDL和载脂蛋白B-白蛋白复合物竞争性地抑制（125）i标记的载脂蛋白B和（125）i标记的LDL与成纤维细胞的结合。当标记的LDL与成纤维细胞在37度下培养6小时时，它经历了细胞内化和降解，通过释放（125）i标记的片段到培养基中来测量。这种降解被未标记的载脂蛋白B抑制。相反，（125）i标记的载脂蛋白B也被成纤维细胞内化和降解，这一过程被LDL抑制。这些发现表明载脂蛋白B与LDL受体特异性结合，并且LDL的细胞结合是由载脂蛋白B决定的。
Low density lipoprotein (LDL) and very low density lipoprotein (VLDL) bind specifically to a receptor on fibroblasts, and it has been postulated that the apoprotein of LDL (apo B) confers the specificity of cellular binding. This hypothesis has been tested in the present study with a watersoluble apo B-bovine serum albumin complex. The binding of (125)I-labeled apo B to cultured fibroblasts was temperature-dependent. Specific binding ranged between 183 and 859 ng/mg of cell protein at a concentration of 5 mug/ml; at 37 degrees , 750-2199 ng/mg was bound and internalized. The binding of apo B greatly exceeded the amount of (125)I-labeled LDL bound at 4 degrees and 37 degrees in the same experiment. Fibroblasts from a subject homozygous for hyper-beta-lipoproteinemia showed minimal binding of (125)I-labeled LDL, consistent with the absence of the cellular LDL receptor. Such cells also had depressed binding of (125)I-labeled apo B. Lymphocytes grown in lipoprotein-deficient medium demonstrated specific binding of LDL; however, freshly isolated lymphocytes did not show such binding. The binding of (125)I-labeled apo B to lymphocytes paralleled the binding of (125)I-labeled LDL. Unlabeled LDL and apo B-albumin complex both competitively inhibited the binding of (125)I-labeled apo B and (125)I-labeled LDL to fibroblasts. When labeled LDL was incubated with fibroblasts for 6 hr at 37 degrees , it underwent cellular internalization and degradation, as measured by the release of (125)I-labeled fragments into the medium. This degradation was inhibited by unlabeled apo B. Conversely, (125)I-labeled apo B also was internalized and degraded by fibroblasts, and this process was inhibited by LDL. These findings demonstrate that apo B binds specifically to the LDL receptor and that the cellular binding of LDL is determined by this apoprotein.