Oral Presentation Australasian Extracellular Vesicles Conference 2018

Defining the EV surface proteome for insights into cargo delivery (#12)

Sarah E Stewart 1 , Kevin Moreau 1
  1. University of Cambridge Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom

Extracellular vesicles (EVs) contain many specific proteins, both cytosolic and membrane bound. The current model for extracellular vesicle biogenesis dictates that the subcellular location of proteins should be reflected in the EV architecture, where cytosolic proteins are in the lumen and cell surface proteins are on the outside of EVs. It has been shown that most receptors anchored in the membrane are retained in the correct orientation and various cytosolic proteins and RNAs are in the lumen of EVs. However, using biochemical approaches, we have shown that a cytosolic protein, Annexin A2, localises to both the lumen and the surface of EVs. Furthermore, it has been suggested that certain transmembrane proteins are in an upside-down orientation.

Here, we use mass spectrometry analysis to describe the surface proteome of extracellular vesicles from several cell lines. We find that there are several cytosolic proteins present on the surface of extracellular vesicles. Using this data, we are working to identify proteins that may be essential for cargo delivery into recipient cells. The presence of cytosolic proteins on the surface of EVs raises questions about their biogenesis and may provide insight into EV packaging and function. It is possible that proteins are specifically packaged onto the outer membrane of EVs and could mediate uptake and fusion with recipient cells.