Endosomes are central protein-sorting stations at the crossroads of numerous membrane trafficking pathways in all eukaryotes. They have a key role in protein homeostasis and cellular signalling and are involved in the pathogenesis of numerous diseases. Endosome-associated protein assemblies or coats collect transmembrane cargo proteins and concentrate them into retrieval domains. These domains can extend into tubular carriers, which then pinch off from the endosomal membrane and deliver the cargoes to appropriate subcellular compartments. Here we discuss novel insights into the structure of a number of tubular membrane coats that mediate the recruitment of cargoes into these carriers, focusing on sorting nexin-based coats such as Retromer, Commander and ESCPE-1. We summarize current and emerging views of how selective tubular endosomal carriers form and detach from endosomes by fission, highlighting structural aspects, conceptual challenges and open questions.

内体是所有真核生物中众多膜运输途径十字路口的中央蛋白质分选站。它们在蛋白质稳态和细胞信号传导中发挥关键作用，并参与多种疾病的发病机制。内体相关的蛋白质组装体或外壳收集跨膜货物蛋白并将其浓缩到检索域中。这些结构域可以延伸到管状载体中，然后从内体膜上夹断并将货物递送到适当的亚细胞区室。在这里，我们讨论了对许多管状膜涂层结构的新见解，这些管状膜涂层介导将货物招募到这些载体中，重点是对基于连接蛋白的涂层进行分类，例如Retromer、Commander和ESCPE-1。我们总结了关于选择性管状内体载体如何通过裂变形成和从内体分离的当前和新兴观点，强调了结构方面、概念挑战和悬而未决的问题。