The regulation of endosome-to-Golgi retrograde transport by tethers and scaffolds

Retrograde transport between endosomes and the trans-Golgi network (TGN) is essential for the recycling of membrane proteins which are involved in a range of biological processes. A variety of machinery components have been identified at the TGN which regulate endosome-to-TGN transport, including small G proteins, SNAREs, tethering factors and scaffold molecules. The challenge is to understand how these regulatory components orchestrate not only the specific docking and fusion of retrograde membrane carriers with the TGN, but also maintain the integrity of this highly dynamic compartment to ensure efficient delivery and export of cargo. Here we review recent advances in defining the form and function of tethers and scaffolds in the regulation of the retrograde transport pathways.