Introduction and aim
Unconventional protein secretion is an important process whereby certain cytosolic proteins are secreted into the extracellular space. Extracellular vesicles (EVs) contain many cytosolic proteins and represent a major pathway for unconventional protein secretion. Work in our lab identified a phospholipid scramblase that is an important regulator of unconventional protein secretion of soluble proteins (not encapsulated in EVs) from mammalian cells. Building on this work we are now interested in whether this phospholipid scramblase plays a role in EV cargo packaging and biogenesis.
Methods and results
To investigate the role of phospholipid scrambling in EV protein composition, we have conducted a proteomic analysis of scramblase knockout and wildtype EVs isolated from HeLa cells. Proteomic analysis shows that upon knockout of a phospholipid scramblase, the protein content in/on EVs is altered. Additionally, roles in EV biogenesis/secretion were investigated using biochemical approaches. Results suggest that scramblase activity is important for biogenesis/secretion of EVs as there is a decrease in the number of EVs secreted per cell.
Conclusions
Unconventional protein secretion is an important fundamental process. Understanding how EVs are packaged, and which proteins reside both within and on EVs is important for insights into the extracellular functions of EVs. This data contributes to the existing pool of knowledge regarding proteins that are secreted through unconventional protein secretion and will help to identify novel molecular pathways involved in EV biogenesis and cargo packaging.