Landers S C, Jones N L, Williams A S, Lewis J C
Department of Pathology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27157-1092.
Am J Pathol. 1993 May;142(5):1668-77.
Macrophages derived from blood monocytes are key in the development of atherosclerosis, as monocyte migration into the intima and accumulation of cholesterol leads to foam cell formation. To investigate the relationship between lipoprotein binding and the distribution of clathrin-coated endocytic vesicles, monocyte-derived macrophages were exposed in vitro to beta very low density lipoprotein (beta VLDL), conjugated to colloidal gold, and later were processed for immuno-electron microscopy to localize clathrin-coated vesicles. The immunolocalization was done in conjunction with either cryosectioning or whole mount intermediate voltage electron microscopy. Preferential binding of beta VLDL on small membrane ruffles and microvilli was quantitatively verified. Clathrin-coated vesicles were distributed throughout the cell; however, clusters of microvilli were associated with both a high concentration of coated vesicles and lipoprotein. Small membrane ruffles were not associated with clathrin-coated vesicles. These data support our hypothesis that endocytosis of beta VLDL near microvilli involves coated vesicles, whereas endocytosis of beta VLDL near ruffles is not mediated by coated endocytic vesicles. Furthermore, the association of coated vesicles with microvilli but not membrane ruffles may be important in understanding ligand trafficking within the cell. Given the distribution of coated vesicles within the cell, it is possible that the site of lipoprotein binding may determine the mechanism of entry into the cell and the metabolic effects of the internalized ligand.
源自血液单核细胞的巨噬细胞在动脉粥样硬化的发展中起关键作用，因为单核细胞迁移到内膜并积累胆固醇会导致泡沫细胞形成。为了研究脂蛋白结合与网格蛋白包被的内吞小泡分布之间的关系，将单核细胞衍生的巨噬细胞在体外暴露于与胶体金结合的β极低密度脂蛋白（β-VLDL），随后进行免疫电子显微镜检查以定位网格蛋白包被的小泡。免疫定位是结合冷冻切片或整装中间电压电子显微镜进行的。β-VLDL在小膜皱褶和微绒毛上的优先结合得到了定量验证。网格蛋白包被的小泡分布在整个细胞中；然而，微绒毛簇与高浓度的包被小泡和脂蛋白都有关联。小膜皱褶与网格蛋白包被的小泡无关。这些数据支持了我们的假设，即微绒毛附近β-VLDL的内吞作用涉及包被小泡，而皱褶附近β-VLDL的内吞作用不是由包被的内吞小泡介导的。此外，包被小泡与微绒毛而非膜皱褶的关联可能对理解细胞内配体运输很重要。鉴于包被小泡在细胞内的分布情况，脂蛋白结合位点可能决定其进入细胞的机制以及内化配体的代谢效应。
