State Key Laboratory of Pharmaceutical Biotechnology, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Nanjing Advanced Institute for Life Sciences, School of Life Sciences, Nanjing University, Nanjing, Jiangsu 210093, China.
School of Medicine and Life Sciences, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China.
Nat Commun. 2017 Jan 9;8:14041. doi: 10.1038/ncomms14041.
Tumour cells secrete exosomes that are involved in the remodelling of the tumour-stromal environment and promoting malignancy. The mechanisms governing tumour exosome release, however, remain incompletely understood. Here we show that tumour cell exosomes secretion is controlled by pyruvate kinase type M2 (PKM2), which is upregulated and phosphorylated in tumours. During exosome secretion, phosphorylated PKM2 serves as a protein kinase to phosphorylate synaptosome-associated protein 23 (SNAP-23), which in turn enables the formation of the SNARE complex to allow exosomes release. Direct phosphorylation assay and mass spectrometry confirm that PKM2 phosphorylates SNAP-23 at Ser95. Ectopic expression of non-phosphorylated SNAP-23 mutant (Ser95→Ala95) significantly reduces PKM2-mediated exosomes release whereas expression of selective phosphomimetic SNAP-23 mutants (Ser95→Glu95 but not Ser20→Glu20) rescues the impaired exosomes release induced by PKM2 knockdown. Our findings reveal a non-metabolic function of PKM2, an enzyme associated with tumour cell reliance on aerobic glycolysis, in promoting tumour cell exosome release.
肿瘤细胞分泌的外泌体参与肿瘤基质环境的重塑和促进恶性肿瘤的发生。然而，控制肿瘤外泌体释放的机制仍不完全清楚。在这里，我们发现肿瘤细胞外泌体的分泌受丙酮酸激酶 M2（PKM2）控制，PKM2 在肿瘤中上调和磷酸化。在分泌外泌体的过程中，磷酸化的 PKM2 作为一种蛋白激酶，磷酸化突触相关蛋白 23（SNAP-23），从而使 SNARE 复合物形成，允许外泌体释放。直接磷酸化实验和质谱分析证实 PKM2 在 Ser95 磷酸化 SNAP-23。外源性表达非磷酸化 SNAP-23 突变体（Ser95→Ala95）显著降低 PKM2 介导的外泌体释放，而表达选择性磷酸模拟 SNAP-23 突变体（Ser95→Glu95 但不是 Ser20→Glu20）则可挽救 PKM2 敲低引起的外泌体释放受损。我们的研究结果揭示了 PKM2 的一种非代谢功能，即与肿瘤细胞依赖有氧糖酵解相关的酶，在促进肿瘤细胞外泌体释放中的作用。
