miR-1227 targets SEC23A to differentially regulate extracellular vesicle shedding

Extracellular vesicles (EV) are lipid encapsulated nanoparticles that are altered in cancer to promote cancer progression and metastasis. Cancer cells shed a heterogenous mixture of EV differing in both size and composition, which likely influence physiological processes in different manners. However, how cells differentially control the shedding of these EV populations is poorly understood. Here we show that miR-1227, a miRNA enriched in prostate cancer EV compared cells, induces the shedding of large EV (such as large oncosomes) while inhibiting the shedding of small EV (such as exosomes). RNA sequencing from cells stably expressing miR-1227, a modified RISCTRAP assay which stabilizes and purifies mRNA-miR-1227 complexes for RNA sequencing, and in silico target prediction were used to identify miR-1227 targets that may mediate this alteration in EV shedding. The COPII vesicle protein SEC23A emerged as a direct target of miR-1227 and was validated by qPCR, Wblot, and luciferase assays. Inhibition of SEC23A was sufficient to induce the shedding of large EV and inhibit the shedding of small EV. These results identify a novel mechanism of EV shedding by which miR-1227 induces a shift in EV shedding favoring the shedding of large EV over small EV through the inhibition of SEC23A.