Umebayashi Kyohei
Department of Cell Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan.
Cell Struct Funct. 2003 Oct;28(5):443-53. doi: 10.1247/csf.28.443.
After cell surface receptors are internalized for endocytosis, they are accurately sorted in endosomes. Some are recycled to the plasma membrane and others are downregulated by delivery to lysosomes. Evidence is rapidly accumulating that ubiquitination of cargo proteins acts as a sorting signal during endocytosis. Sorting devices that recognize ubiquitin are distributed to various compartments, probably acting in a concerted manner. Cholesterol is enriched in the plasma membrane and endosomes, and is involved in protein sorting by forming microdomains called lipid rafts. Ubiquitin and cholesterol hold the key to control the endocytic sorting, and they are likely acting cooperatively.
细胞表面受体通过内吞作用内化后，会在内体中进行精确分选。一些受体会被循环回质膜，而另一些则通过被递送至溶酶体而被下调。越来越多的证据表明，货物蛋白的泛素化在内吞作用期间充当分选信号。识别泛素的分选装置分布于各个区室，可能以协同方式发挥作用。胆固醇在质膜和内体中富集，并通过形成称为脂筏的微区参与蛋白质分选。泛素和胆固醇是控制内吞分选的关键，它们可能协同发挥作用。
