Compartmentation and functions of sphingolipids.

Sphingolipids (SLs) are one of the three major lipid classes in all eukaryotic cells. They function as structural molecules of membranes and can also act as highly active signaling molecules. SL biosynthesis is mainly occurring at the endoplasmic reticulum and the Golgi apparatus. However, SL intermediates are also generated at other organelles such as the plasma membrane and the lysosome. SL biosynthesis is therefore highly compartmentalized. Maintaining SL levels is necessary for the function of multiple trafficking pathways. One major challenge is to decipher the complex regulatory networks controlling SL biosynthesis, the coordination of vesicular and non-vesicular SL transport as well as their role in trafficking. Recent investigations have shed new light on the regulation of SL biosynthesis. Here, we review how SL biosynthesis is coordinated, how SLs are transported and how their levels affect trafficking pathways. Finally, we discuss recently developed methods to study SL metabolism with spatio-temporal resolution.