VAP-A and its binding partner CERT drive biogenesis of RNA-containing extracellular vesicles

RNA transfer via extracellular vesicles (EVs) influences cell phenotypes; however, lack of information regarding biogenesis of RNA-containing EVs has limited progress in the field. Vanderbilt University School of Medicine researchers have identified endoplasmic reticulum membrane contact sites (ER MCSs) as platforms for the generation of RNA-containing EVs. The researchers identified a subpopulation of small EVs that is highly enriched in RNA and regulated by the ER MCS linker protein VAP-A. Functionally, VAP-A-regulated EVs are critical for miR-100 transfer between cells and in vivo tumor formation. Lipid analysis of VAP-A-knockdown EVs revealed reductions in the EV biogenesis lipid ceramide. Knockdown of the VAP-A-binding ceramide transfer protein CERT led to similar defects in EV RNA content. Imaging experiments revealed that VAP-A promotes luminal filling of multivesicular bodies (MVBs), CERT localizes to MVBs, and the ceramide-generating enzyme neutral sphingomyelinase 2 colocalizes with VAP-A-positive ER. The researchers propose that ceramide transfer via VAP-A-CERT linkages drives the biogenesis of a select RNA-containing EV population.