Unrestrained Mammalian Target of Rapamycin Complexes 1 and 2 Increase Expression of Phosphatase and Tensin Homolog Deleted on Chromosome 10 to Regulate Phosphorylation of Akt Kinase
Unrestrained Mammalian Target of Rapamycin Complexes 1 and 2 Increase Expression of Phosphatase and Tensin Homolog Deleted on Chromosome 10 to Regulate Phosphorylation of Akt Kinase
复制标题
DOI：
10.1074/jbc.m111.246397
复制
发表时间：
2012-02-03
影响因子：
4.8
通讯作者：
Choudhury, Goutam Ghosh
中科院分区：
文献类型：
--
作者：
Das, Falguni;Ghosh-Choudhury, Nandini;Choudhury, Goutam Ghosh
多发性硬化症复合物2（TSC 2）和10号染色体上缺失的磷酸酶和张力蛋白同源物（PTEN）的功能是阻断生长因子诱导的哺乳动物雷帕霉素靶蛋白（mTOR）信号传导，并且在常染色体显性错构瘤综合征中突变。mTOR与一系列常见和不同的蛋白质结合，形成TOR复合物1（TORC 1）和TORC 2，调节细胞生长，分裂和代谢。TSC 2缺陷诱导mTOR的组成性激活，由于负反馈调节导致胰岛素抵抗状态，导致Akt磷酸化减少。我们最近描述了一种替代机制，表明在TSC 2缺陷中，增强的PTEN表达有助于减少Akt磷酸化。为了探讨PTEN的调控机制，我们使用雷帕霉素和组成型活性mTOR来显示TORC 1增加PTEN mRNA和蛋白的表达。我们发现在TSC 2（-/-）小鼠胚胎成纤维细胞中，mTOR激酶死亡突变体的表达通过转录机制抑制TORC 1和TORC 2，从而降低PTEN的表达。此外，激酶-deadm TOR分别增加和减少Akt在催化环位点Thr-308和疏水基序位点Ser-473的磷酸化。此外，通过下调raptor来抑制TSC 2缺失小鼠胚胎成纤维细胞或293细胞中的TORC 1失调，降低了转录因子Hif 1 α的水平并阻断了PTEN表达，导致Akt在Thr-308和Ser-473处的磷酸化增强。最后，rictor或mSin 1的敲除减弱了Hif 1 alpha的表达，从而降低了PTEN的转录。这些结果揭示了以前未被认识到的TORC 1和TORC 2在PTEN上调中的细胞自主功能，该功能阻止Akt的磷酸化并可能阻止TSC患者恶性肿瘤的发展。
Tuberous sclerosis complex 2 (TSC2) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) function to block growth factor-induced mammalian target of rapamycin (mTOR) signaling and are mutated in autosomal dominant hamartoma syndromes. mTOR binds to a spectrum of common and different proteins to form TOR complex 1 (TORC1) and TORC2, which regulate cell growth, division, and metabolism. TSC2 deficiency induces constitutive activation of mTOR, leading to a state of insulin resistance due to a negative feedback regulation, resulting in reduced Akt phosphorylation. We have recently described an alternative mechanism showing that in TSC2 deficiency, enhanced PTEN expression contributes to reduced Akt phosphorylation. To explore the mechanism of PTEN regulation, we used rapamycin and constitutively active mTOR to show that TORC1 increases the expression of PTEN mRNA and protein. We found that in TSC2(-/-) mouse embryonic fibroblasts expression of a kinase-dead mutant of mTOR, which inhibits both TORC1 and TORC2, decreases the expression of PTEN via transcriptional mechanism. Furthermore, kinase-deadm TOR increased and decreased phosphorylation of Akt at catalytic loop site Thr-308 and hydrophobic motif site Ser-473, respectively. Moreover, inhibition of deregulated TORC1 in TSC2-null mouse embryonic fibroblasts or in 293 cells by down-regulation of raptor decreased the levels of the transcription factor Hif1 alpha and blocked PTEN expression, resulting in enhanced phosphorylation of Akt at Thr-308 and Ser-473. Finally, knockdown of rictor or mSin1 attenuated the expression of Hif1 alpha, which decreased transcription of PTEN. These results unravel a previously unrecognized cell-autonomous function of TORC1 and TORC2 in the up-regulation of PTEN, which prevents phosphorylation of Akt and may shield against the development of malignancy in TSC patients.