JB Review Emerging roles of recycling endosomes

Cells internalize extracellular solutes, ligands and pro-teins and lipids in the plasma membrane (PM) by endo-cytosis. The removal of membrane from the PM is counteracted by endosomal recycling pathways that return the endocytosed proteins and lipids back to the PM. Recycling to the PM can occur from early endo-somes. However, many cells have a distinct subpopula-tion of endosomes that have a mildly acidic pH of 6.5 and are involved in the endosomal recycling. These endosomes are dubbed recycling endosomes (REs). In recent years, studies have begun to reveal that function of REs is not limited to the endosomal recycling. In this review, I summarize the nature of membrane trafficking pathways that pass through REs and the cell biological roles of these pathways