Figure 1. Exosome biogenesis.

Lipids, proteins and nucleic acids are transported to MVBs and onto or into the intraluminal vesicles, which upon fusion of the MVB with the plasma membrane are released as exosomes. Originally identified as a way to release transferrin receptor from maturing reticulocytes, other plasma membrane proteins have been shown to be targeted to MVBs through various mechanisms and released on exosomes. RNA and cytoplasmic proteins are also transported to MVBs, although the mechanisms mediating this transport are less understood (indicated by dashed line). See Glossary for definitions.