The chemotherapeutic drug epirubicin increases the exosomal export of miR-503 in endothelial cells. To understand the mechanisms behind this process, we transfected endothelial cells with miR-503 carrying a biotin tag. Then, we pulled-down the proteins interacting with miR-503 and studied their role in microRNA exosomal export. A total of four different binding partners were identified by mass spectrometry and validated by western blotting and negative controls, among them ANXA2 and hnRNPA2B1. Using knock-down systems combined with pull-down analysis, we determined that epirubicin mediates the export of miR-503 by disrupting the interaction between hnRNPA2B1 and miR-503. Then, both ANXA2 and miR-503 are sorted into exosomes while hnRNPA2B1 is relocated into the nucleus. The combination of these processes culminates in the increased export of miR-503. These results suggest, for the first time, that RNA-binding proteins can negatively regulate the exosomal sorting of microRNAs.

中文翻译：

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hnRNPA2B1 抑制内皮细胞中 miR-503 的外泌体输出。


化疗药物表阿霉素可增加内皮细胞中 miR-503 的外泌体输出。为了了解这一过程背后的机制，我们用带有生物素标签的 miR-503 转染内皮细胞。然后，我们提取了与 miR-503 相互作用的蛋白质，并研究了它们在 microRNA 外泌体输出中的作用。通过质谱鉴定了总共四种不同的结合配偶体，并通过蛋白质印迹和阴性对照进行了验证，其中包括 ANXA2 和 hnRNPA2B1。使用敲低系统结合下拉分析，我们确定表阿霉素通过破坏 hnRNPA2B1 和 miR-503 之间的相互作用来介导 miR-503 的输出。然后，ANXA2 和 miR-503 都被分选到外泌体中，而 hnRNPA2B1 则被重新定位到细胞核中。这些过程的结合最终导致 miR-503 的输出增加。这些结果首次表明，RNA 结合蛋白可以负向调节 microRNA 的外泌体分选。