Getting to the right place at the right time – membrane trafficking and maturation in the endolysosomal system

The endolysosomal system connects Golgi and plasma membrane to the degradative pathway towards the lysosome and therefore presents a crossroads for endocytic recycling, secretory transport and degradation. This complexity makes protein sorting and trafficking within the endolysosomal system challenging, and it requires tight regulation so that all proteins localize correctly. Proteins are sorted by distinct sorting adaptors, which recognize sorting signals and subsequently facilitate formation of transport carriers, which deliver content to other organelles. Alternatively, organelle maturation allows passive protein transport along different trafficking routes including endosomal and autophagosomal maturation. In this review, we will provide a bird's eye overview of the divers routes along which proteins are transported within the endolysosomal system and highlight open questions in the field.