Sphingomyelin is sorted at the trans Golgi network into a distinct class of secretory vesicle

Significance The biochemical reactions that drive cellular life are housed in distinct membrane enclosed compartments known as organelles. Whereas proteins targeting to different organelles are well developed, little is known regarding how lipids are sorted to different organelles. We engineered a protein from a marine organism into a fluorescent “biosensor” of sphingomyelin (SM), a sphingolipid that is produced in the Golgi apparatus but is a major component of the plasma membrane. By monitoring SM dynamics in live cells, we discovered that SM is transported from its site of synthesis in the Golgi to the plasma membrane in a distinct type of secretory transport carrier. Our findings show that vesicle-based trafficking pathways are specialized to transport distinct types of lipids, in addition to proteins.