Endocytosis of oxidized low density lipoprotein through scavenger receptor CD36 utilizes a lipid raft pathway that does not require caveolin-1
Endocytosis of oxidized low density lipoprotein through scavenger receptor CD36 utilizes a lipid raft pathway that does not require caveolin-1
复制标题
DOI：
10.1074/jbc.m307722200
复制
发表时间：
2003-11-14
影响因子：
4.8
通讯作者：
Lublin, DM
中科院分区：
文献类型：
--
作者：
Zeng, YC;Tao, NB;Lublin, DM
清道夫受体CD 36结合多种配体，包括血小板反应蛋白-1、氧化低密度脂蛋白（OxLDL）、脂肪酸、阴离子磷脂和凋亡细胞。据报道，CD 36存在于脂筏/小窝中，但对该蛋白在基线或配体结合后的膜运输知之甚少。在这里，我们确定，在中国仓鼠卵巢（CHO）细胞和内源性表达的CD 36在C32细胞中的表达导致均匀分布的蛋白质的质膜上，通过共聚焦荧光显微镜判断。通过抗CD 36抗体染色和表达嵌合CD 36-绿色荧光蛋白构建体的CHO细胞的活细胞成像观察到这种均匀模式。相比之下，小窝蛋白-1显示其常见的点状表面分布。相应地，CD 36和小窝蛋白-1的双重标记显示基本上没有重叠，无论是通过免疫荧光光学显微镜，也不是通过免疫金电子显微镜。此外，通过蔗糖梯度超离心分离冷Triton X-100细胞裂解物的脂筏产生了CD 36和小窝蛋白-1，但小窝蛋白-1的免疫沉淀物不含CD 36。OxLDL的结合导致CD 36和OxLDL内化到不含小窝蛋白-1或转铁蛋白但共内化糖基-磷脂酰肌醇锚定蛋白衰变加速因子（一种脂筏蛋白）的内体结构中。此外，在小窝蛋白-1-阴性KB细胞系中CD 36的表达足以用于OxLDL诱导的CD 36内化，表明小窝蛋白-1对于该内吞过程不是必需的。综上所述，这些数据表明，在稳态下，CD 36定位于脂筏中，但不在小窝中，并且OxLDL与CD 36的结合通过脂筏途径导致内吞作用，所述脂筏途径不同于网格蛋白介导的或小窝蛋白内化途径。
The scavenger receptor CD36 binds a diverse array of ligands, including thrombospondin-1, oxidized low density lipoprotein (OxLDL), fatty acids, anionic phospholipids, and apoptotic cells. CD36 has been reported to be present in lipid rafts/caveolae, but little is known about the membrane trafficking of this protein at baseline or following ligand binding. Here, we determined that expression of CD36 in Chinese hamster ovary (CHO) cells and endogenous expression of CD36 in C32 cells led to a homogeneous distribution of the protein on the plasma membrane, as judged by confocal fluorescence microscopy. This homogeneous pattern was observed both by anti-CD36 antibody staining and by live cell imaging of CHO cells expressing a chimeric CD36-green fluorescent protein construct. In contrast, caveolin-1 displayed its usual punctate surface distribution. Correspondingly, dual labeling of CD36 and caveolin-1 showed essentially no overlap, neither by immunofluorescence light microscopy nor by immunogold electron microscopy. Furthermore, isolation of lipid rafts by sucrose gradient ultracentrifugation of cold Triton X-100 cell lysates yielded both CD36 and caveolin-1, but immunoprecipitates of caveolin-1 did not contain CD36. Binding of OxLDL led to internalization of CD36 and OxLDL into endosomal structures that did not contain caveolin-1 or transferrin but that co-internalized the glycosyl-phosphatidylinositol-anchored protein decay accelerating factor, a lipid raft protein. Furthermore, expression of CD36 in the caveolin-1-negative KB cell line is sufficient for OxLDL-induced internalization of CD36, indicating that caveolin-1 is not required for this endocytic process. Taken together, these data demonstrate that at steady state, CD36 is localized in lipid rafts but not in caveolae, and that binding of OxLDL to CD36 leads to endocytosis through a lipid raft pathway that is distinct from the clathrin-mediated or caveolin internalization pathways.