Moving and positioning the endolysosomal system

- Endolysosomal organelles are dynamically distributed throughout the cytoplasm.
- Movement of endolysosomal organelles depends on coupling to microtubule motors and actin.
- Contacts with the endoplasmic reticulum regulate organelle movement and positioning.
- Other organelles move by hitchhiking on endolysosomal organelles.
- Cellular functions depend on movement and positioning of endolysosomal organelles.

The endolysosomal system is extremely dynamic, yet highly organized. The spatio-temporal distribution of endolysosomal organelles depends on transport driven by microtubule motors such as kinesins and dynein, and by actin-based myosin motors. It has recently become appreciated that interactions with motors are controlled by contacts with other organelles, particularly the endoplasmic reticulum (ER). The ER also controls the concentration of endolysosomal organelles in the perinuclear area, as well as their fission and fusion, through a complex system of tethering proteins. Dynamic interactions go both ways, as contacts with endosomes can influence the movement of the ER and peroxisomes. The dynamics of endolysosomal organelles should thus no longer be studied in isolation, but in the context of the whole endomembrane system.