The structure and function of the retromer protein complex

The transport of transmembrane proteins and associated ligands through the endosomal system is governed by a number of different protein assemblies. One such assembly is retromer, a peripheral membrane protein complex that has important roles in endosomal sorting of a variety of cargo molecules. Retromer was first shown to control the endosome-to-Golgi retrieval of lysosomal hydrolase receptors, and over the past few years, it has been found to play a similar role in the transport of many other proteins in all eukaryotes from simple amoeba to plants and mammals. Recent structural studies of the core retromer complex have revealed both unexpected similarities and intriguing differences between retromer and other regulators of membrane trafficking and are beginning to open the door to a mechanistic understanding of retromer-mediated endosomal transport.