Bretscher M S, Thomson J N
EMBO J. 1983;2(4):599-603. doi: 10.1002/j.1460-2075.1983.tb01469.x.
HeLa cells bind horse spleen ferritin when the two are incubated at 0 degrees C. Since the majority of this bound ferritin is located in coated pits, we conclude that the ferritin binds to a specific receptor which takes part in an endocytic cycle. When substrate-attached and well-spread giant HeLa cells are briefly labelled at 0 degrees C with ferritin, ferritin particles are found to be concentrated towards the cell periphery, where they exist largely outside coated pits. This peripheral concentration is a property of circulating (and not just newly synthesized) receptors because it is not affected by prior incubation of giant cells in cycloheximide. However, coated pits are themselves roughly uniformly distributed over the surface of these cells. These results provide evidence that the membrane internalised by coated pits on these cells is returned to the cell surface at the leading edge of the cell. Because of this separation of the sites of endocytosis and exocytosis, a flow of membrane must occur across the cell surface. This flow is composed of lipid plus receptors. The implications of this for capping and for cell spreading are discussed.
当在0摄氏度下孵育时，海拉细胞会结合马脾铁蛋白。由于大部分结合的铁蛋白位于被膜小窝中，我们得出结论，铁蛋白与参与内吞循环的特定受体结合。当贴壁且铺展良好的巨大海拉细胞在0摄氏度下用铁蛋白短暂标记时，发现铁蛋白颗粒集中在细胞周边，它们在很大程度上存在于被膜小窝之外。这种周边集中是循环（而非仅新合成）受体的特性，因为它不受巨细胞预先在环己酰亚胺中孵育的影响。然而，被膜小窝本身在这些细胞表面大致均匀分布。这些结果提供了证据，表明这些细胞上被膜小窝内化的膜在细胞前缘返回细胞表面。由于内吞和外排位点的这种分离，膜流必定会在细胞表面发生。这种流由脂质加受体组成。讨论了这对帽化和细胞铺展的影响。
