Fusion protein engineered exosomes for targeted degradation of specific RNAs in lysosomes: a proof-of-concept study

Therapeutically intervening the function of RNA in vivo remains a big challenge. We here developed an exosome-based strategy to deliver engineered RNA-binding protein for the purpose of recruiting specific RNA to the lysosomes for degradation. As a proof-of-principle study, RNA-binding protein HuR was fused to the C-terminus of Lamp2b, a membrane protein localized in both exosome and lysosome. The fusion protein was able to be incorporated into the exosomes. Moreover, exosomes engineered with Lamp2b-HuR successfully decreased the abundance of RNA targets possibly via lysosome-mediated degradation, especially when the exosomes were acidified. The system was specifically effective in macrophages, which are lysosome enriched and resistant to routine transfection mediated RNAi strategy. In the CCl4-induced liver injury mouse model, we found that delivery of acidified exosomes engineered with Lamp2b-HuR significantly reduced liver fibrosis, together with decreased miR-155 and other inflammatory genes. In summary, the established exosome-based RNA-binding protein delivery strategy, namely “exosome-mediated lysosomal clearance”, takes the advantage of exosome in targeted delivery and holds great promise in regulating a set of genes in vivo.