An extracellular vesicle delivery platform based on the PTTG1IP protein

Abstract Extracellular vesicles (EVs) hold great promise as therapeutic delivery vehicles, although their potential is limited by a lack of efficient EV engineering strategies to enhance loading and functional delivery of therapeutic cargo. Here, we identified N-glycosylation as a putative EV- sorting feature using a novel bioinformatics analysis strategy. We exploited this finding to develop a platform for EV-mediated delivery of macromolecular cargoes based on PTTG1IP, a small N- glycosylated, single spanning transmembrane protein. We demonstrate that PTTG1IP EV enrichment is dependent on its N-glycosylation at two sites, and that PTTG1IP is a suitable scaffold for EV loading of therapeutic cargoes. To achieve functional delivery, cargoes were fused to PTTG1IP, separated by various self-cleaving sequences intended to promote cargo release from the scaffold after EV loading. In addition, the fusogenic VSVG protein was co-expressed to enhance endosomal escape. This PTTG1IP-based strategy enabled highly efficient functional delivery of Cre protein to recipient cells and mouse xenograft tumors, as well as Cas9 and Cas9/sgRNA complex delivery to reporter cells. Importantly, PTTG1IP exhibited improved protein delivery potential relative to a scaffold based on CD63 (a common EV marker). Moreover, we developed various PTTG1IP variants with improved properties, demonstrating the versatility of PTTG1IP as an EV scaffold. The EV-loading platform described in this study offers significant advantages over other strategies, such as favourable membrane topology, the potential for further engineering, and functional delivery capability, which will enable the development of improved EV-based therapeutics.