Combined regulation of mTORC1 and lysosomal acidification by GSK-3 suppresses autophagy and contributes to cancer cell growth
Combined regulation of mTORC1 and lysosomal acidification by GSK-3 suppresses autophagy and contributes to cancer cell growth
复制标题
DOI：
10.1038/onc.2014.390
复制
发表时间：
2015-08-27
期刊：
影响因子：
8
通讯作者：
Eldar-Finkelman, H.
中科院分区：
文献类型：
--
作者：
Azoulay-Alfaguter, I.;Elya, R.;Eldar-Finkelman, H.
关于糖原合成酶激酶 3 (GSK-3) 在癌症进展中的作用存在争议。最近的研究表明 GSK-3 参与了哺乳动物雷帕霉素靶蛋白 (mTOR) 的调节，而 mTOR 是恶性转化中的已知参与者。自噬是一种自我降解途径，被 mTOR 抑制，与细胞存活和肿瘤生长密切相关。在这里，我们表明 GSK-3 通过 mTOR 复合物-1 (mTORC1) 和溶酶体调节抑制自噬。我们发现，GSK-3 亚型（GSK-3 α 和 GSK-3 α）的过度表达会激活 mTORC1 并抑制 MCF-7 人乳腺癌细胞中的自噬，如 beclin-1 水平降低和 Sequestosome 1 (p62/SQSTM1) 上调所示。此外，GSK-3 的过度表达增加了自噬体的数量并抑制了自噬流。该活性与 GSK-3 引发的溶酶体酸化减少直接相关（其中 GSK-3 beta 的影响更强）。我们发现 MCF-7 细胞中溶酶体酸化减少，并且自噬体和 p62/SQSTM1 水平增加以及 mTORC1 活性增加。随后，用 GSK-3 抑制剂处理细胞可恢复溶酶体酸化，增强自噬通量并抑制 mTORC1。此外，GSK-3抑制剂抑制细胞增殖。我们提供的证据表明，GSK3 介导的 mTORC1 活性和 GSK-3 介导的溶酶体酸化通过不同的途径发生，但 mTORC1 和溶酶体都控制细胞生长。最后，我们发现 GSK-3 减少的溶酶体酸化抑制内吞清除，如表皮生长因子受体内吞降解减少所证明的。综上所述，我们的研究将 GSK-3 视为协调细胞稳态的关键调节因子。 GSK-3 抑制剂可能有助于针对 mTORC1 和溶酶体酸化进行癌症治疗。
There is controversy over the role of glycogen synthase kinase-3 (GSK-3) in cancer progression. Recent work has implicated GSK-3 in the regulation of mammalian target of rapamycin (mTOR), a known player in malignant transformation. Autophagy, a selfdegradation pathway, is inhibited by mTOR and is tightly associated with cell survival and tumor growth. Here we show that GSK-3 suppresses autophagy via mTOR complex-1 (mTORC1) and lysosomal regulation. We show that overexpression of GSK-3 isoforms (GSK-3 alpha and GSK-3 alpha) activated mTORC1 and suppressed autophagy in MCF-7 human breast cancer cells as indicated by reduced beclin-1 levels and upregulation of sequestosome 1 (p62/SQSTM1). Further, overexpression of GSK-3 increased the number of autophagosomes and inhibited autophagic flux. This activity was directly related to reduced lysosomal acidification triggered by GSK-3 (in which GSK-3 beta has a stronger impact). We found that lysosomal acidification is reduced in MCF-7 cells that also exhibit increased levels of autophagosomes and p62/SQSTM1 and increased activity of mTORC1. Subsequently, treating cells with GSK-3 inhibitors restored lysosomal acidification, enhanced autophagic flux and inhibited mTORC1. Furthermore, GSK-3 inhibitors inhibited cell proliferation. We provide evidence that GSK3-mediated mTORC1 activity and GSK-3-mediated lysosomal acidification occur via distinct pathways, yet both mTORC1 and lysosomes control cell growth. Finally, we show that GSK-3-reduced lysosomal acidification inhibits endocytic clearance as demonstrated by reduced endocytic degradation of the epidermal growth factor receptor. Taken together, our study places GSK-3 as a key regulator coordinating cellular homeostasis. GSK-3 inhibitors may be useful in targeting mTORC1 and lysosomal acidification for cancer therapy.