PTEN negatively regulates mTORC2 formation and signaling in grade IV glioma via Rictor hyperphosphorylation at Thr1135 and direct the mode of action of an mTORC1/2 inhibitor.
PTEN negatively regulates mTORC2 formation and signaling in grade IV glioma via Rictor hyperphosphorylation at Thr1135 and direct the mode of action of an mTORC1/2 inhibitor.
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DOI：
10.1038/oncsis.2016.34
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发表时间：
2016-05-30
期刊：
影响因子：
6.2
通讯作者：
Mandal C
中科院分区：
文献类型：
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作者：
Bhattacharya K;Maiti S;Mandal C
为了研究PTEN在多形性胶质母细胞瘤的哺乳动物靶标雷帕霉素复合体2信号转导中的作用，我们发现在多形性胶质母细胞瘤中mTORC2的活性更高，与PTENwt细胞相比，mTOR(Ser2481)、AKT(Ser473)和糖原合成酶3β(GSK3β)(Ser9)的磷酸化水平增强。此外，PTEN缺失后的PTENwt细胞显示mTORC2激活。PTENwt细胞中mTORC2信号的减少与Thr1135残基上更高的Rictor磷酸化有关。Thr1135位的Rictor的磷酸化抑制了其与mTORC的结合，从而减少了mTORC2复合体的形成。此外，表达突变的Rictor(Thr1135被丙氨酸取代)的PTENwt细胞显示mTORC2的形成和信号增强。这种增强的mTORC2信号促进了GSK3β的失活。因此，我们建立了基底膜中mTORC2和GSK3β的相互激活机制。据我们所知，这是第一个报道PTEN通过促进GBM中Rictor磷酸化(Thr1135)在mTORC2形成中的作用。此外，对mTORC2的药物敏感性进行了评估。一种新发现的咔唑生物碱，马哈宁，对PTENu和PTENwt细胞都有细胞毒作用。对PTENu细胞的mTORC1/2和AKT均有完全抑制作用，而对PTENwt细胞的mTORC1只有抑制作用。在PTENwt细胞中，耗尽PTEN或与磷脂酰肌醇3激酶抑制剂联合使用均可增强mTORC1/2抑制剂的细胞毒作用和AKT抑制活性。相反，耗尽Rictor可降低mTORC1/2抑制剂对PTENu细胞的细胞毒作用。因此，PTEN在mTORC2的形成中起重要作用，并影响mTORC1/2抑制剂在GBM中的作用。
To investigate the role of PTEN (phosphatase and tensin homolog) in mammalian target of rapamycin complex 2 (mTORC2) signaling in glioblastoma multiforme (GBM), we found higher activation of mTORC2 in PTENmu cells, as evidenced by enhanced phosphorylation of mTOR (Ser2481), AKT (Ser473) and glycogen synthase kinase 3 beta (GSK3β) (Ser9) as compared with PTENwt cells. In addition, PTENwt cells upon PTEN depletion showed mTORC2 activation. The reduced mTORC2 signaling in PTENwt cells was related to higher Rictor phosphorylation at Thr1135 residue. Phosphorylation of Rictor at Thr1135 inhibited its association with mTORC and thus there was a reduction in mTORC2 complex formation. In addition, PTENwt cells expressing mutated Rictor in which Thr1135 was substituted with alanine, showed enhanced mTORC2 formation and signaling. This enhanced mTORC2 signaling promoted inactivation of GSK3β. Thus, we established the reciprocal activation of mTORC2 and GSK3β in GBM. To the best of our knowledge, this is the first report describing role of PTEN in mTORC2 formation by promoting Rictor phosphorylation (Thr1135) in GBM. Furthermore, the drug sensitivity of mTORC2 was evaluated. A newly identified carbazole alkaloid, mahanine, showed cytotoxicity in both PTENmu and PTENwt cells. It inhibited both mTORC1/2 and AKT completely in PTENmu cells, whereas it inhibited only mTORC1 in PTENwt cells. Cytotoxity and AKT-inhibitory activity of the mTORC1/2 inhibitor was increased either by depleting PTEN or in combination with phosphatidylinositol 3 kinase inhibitors in PTENwt cells. In contrast, depletion of Rictor decreased the cytotoxicity of the mTORC1/2 inhibitor in PTENmu cells. Thus, PTEN has an important role in mTORC2 formation and also influences the effectiveness of an mTORC1/2 inhibitor in GBM.