Small molecule inhibitors of hnRNPA2B1-RNA interactions reveal a predictable sorting of RNA subsets into extracellular vesicles.

Extracellular vesicles (EVs) are cell-secreted membranous particles contributing to intercellular communication. Coding and noncoding RNAs can be detected as EV cargo, and RNA-binding proteins (RBPs), such as hnRNPA2B1, have been circumstantially implicated in EV-RNA sorting mechanisms. However, the contribution of competitive RBP-RNA interactions responsible for RNA-sorting outcomes is still unclear, especially for predicting the EV-RNA content. We designed a reverse proteomic analysis exploiting the EV-RNA to identify intracellular protein binders in vitro. Using cells expressing a recombinant hnRNPA2B1 to normalize competitive interactions, we prioritized a network of heterogeneous nuclear ribonucleoproteins and purine-rich RNA sequences subsequently validated in secreted EV-RNA through short fluorescent RNA oligos. Then, we designed a GGGAG-enriched RNA probe that efficiently interacted with a full-length human hnRNPA2B1 protein. We exploited the interaction to conduct a pharmacological screening and identify inhibitors of the protein-RNA binding. Small molecules were orthogonally validated through biochemical and cell-based approaches. Selected drugs remarkably impacted secreted EV-RNAs and reduced an RNA-dependent, EV-mediated paracrine activation of NF-kB in recipient cells. These results demonstrate the relevance of post-transcriptional mechanisms for EV-RNA sorting and the possibility of predicting the EV-RNA quality for developing innovative strategies targeting discrete paracrine functions.