Physiology and pathology of endosome-to-Golgi retrograde sorting.

Bidirectional traffic between the Golgi apparatus and the endosomal system sustains the functions of the trans-Golgi network (TGN) in secretion and organelle biogenesis. Export of cargo from the TGN via anterograde trafficking pathways depletes the organelle of sorting receptors, processing proteases, SNARE molecules, and other factors, and these are subsequently retrieved from endosomes via the retrograde pathway. Recent studies indicate that retrograde trafficking is vital to early metazoan development, nutrient homeostasis, and for processes that protect against Alzheimer's and other neurological diseases.