Schmid S L, Fuchs R, Male P, Mellman I
Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510.
Cell. 1988 Jan 15;52(1):73-83. doi: 10.1016/0092-8674(88)90532-6.
Functionally distinct subpopulations of endosomes involved in targeting internalized material to specific intracellular destinations were resolved as two distinct peaks by free-flow electrophoresis. The less anodally shifted peak contained a population of early endosomes selectively labeled by brief exposures to endocytic tracers or by receptor-bound transferrin. Late endosomes, labeled only after longer periods of internalization, migrated more toward the anode. While both fluid phase and certain receptor-bound markers could be rapidly chased from early to late endosomes, transferrin remained in vesicles comigrating with early endosomes even after prolonged uptake. Thus early and late endosomes are kinetically related but functionally distinct: early endosomes serve as the major site of recycling of membrane and surface receptors and late endosomes are involved in delivery to lysosomes. The subpopulations each contain unique polypeptides not found on the plasma membrane. Thus, endosomes cannot be derived entirely from internalized cell surface components, and may have at least partly independent biosynthetic origins.
通过自由流动电泳，参与将内化物质靶向特定细胞内目的地的功能不同的内体亚群被解析为两个不同的峰。阳极迁移较少的峰包含一群早期内体，它们通过短暂暴露于内吞示踪剂或受体结合的转铁蛋白而被选择性标记。晚期内体仅在较长时间内化后才被标记，向阳极迁移得更多。虽然液相和某些受体结合标记物都可以从早期内体快速转移到晚期内体，但即使经过长时间摄取，转铁蛋白仍保留在与早期内体共同迁移的囊泡中。因此，早期和晚期内体在动力学上相关但功能不同：早期内体是膜和表面受体循环利用的主要场所，晚期内体则参与向溶酶体的递送。每个亚群都含有质膜上未发现的独特多肽。因此，内体不能完全源自内化的细胞表面成分，可能至少部分具有独立的生物合成起源。
