Tti1 and Tel2 Are Critical Factors in Mammalian Target of Rapamycin Complex Assembly
Tti1 and Tel2 Are Critical Factors in Mammalian Target of Rapamycin Complex Assembly
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DOI：
10.1074/jbc.m110.121699
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发表时间：
2010-06-25
影响因子：
4.8
通讯作者：
Mizushima, Noboru
中科院分区：
文献类型：
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作者：
Kaizuka, Takeshi;Hara, Taichi;Mizushima, Noboru
哺乳动物雷帕霉素靶蛋白（mTOR）是磷脂酰肌醇3-激酶相关激酶（PIKK）家族的成员，是翻译、细胞生长和自噬的主要调节因子。mTOR存在于两种不同的复合物中，mTORC 1和mTORC 2，其亚基组成不同。在这项研究中，我们确定KIAA 0406作为一种新的mTOR相互作用蛋白。由于它与粟酒裂殖酵母Tti 1具有序列同源性，我们将其命名为哺乳动物Tti 1。Tti 1在mTORC 1和mTORC 2中与mTOR组成性相互作用。Tti 1的敲低抑制mTORC 1底物（S6 K1和4F-BP 1）和mTORC 2底物（Akt）的磷酸化，并诱导自噬。S.粟酒裂殖酵母Tti 1与Tel 2结合，Tel 2是一种最近报道其哺乳动物同源物调节PIKK稳定性的蛋白质。我们证实Tti 1也在哺乳动物细胞中与Tel 2结合，并且Tti 1与PIKK蛋白家族的所有六个成员（mTOR、ATM、ATR、DNA-PKcs、SMG-1和TRRAP）相互作用并使其稳定。此外，使用免疫沉淀和尺寸排阻色谱分析，我们发现Tti 1或Tel 2的敲低导致mTORC 1和mTORC 2的分解。这些结果表明Tti 1和Tel 2不仅对mTOR稳定性很重要，而且对mTOR复合物的组装以维持其活性也很重要。
Mammalian target of rapamycin (mTOR) is a member of the phosphatidylinositol 3-kinase-related kinase (PIKK) family and is a major regulator of translation, cell growth, and autophagy. mTOR exists in two distinct complexes, mTORC1 and mTORC2, that differ in their subunit composition. In this study, we identified KIAA0406 as a novel mTOR-interacting protein. Because it has sequence homology with Schizosaccharomyces pombe Tti1, we named it mammalian Tti1. Tti1 constitutively interacts with mTOR in both mTORC1 and mTORC2. Knockdown of Tti1 suppresses phosphorylation of both mTORC1 substrates (S6K1 and 4F-BP1) and an mTORC2 substrate (Akt) and also induces autophagy. S. pombe Tti1 binds to Tel2, a protein whose mammalian homolog was recently reported to regulate the stability of PIKKs. We confirmed that Tti1 binds to Tel2 also in mammalian cells, and Tti1 interacts with and stabilizes all six members of the PIKK family of proteins (mTOR, ATM, ATR, DNA-PKcs, SMG-1, and TRRAP). Furthermore, using immuno-precipitation and size-exclusion chromatography analyses, we found that knockdown of either Tti1 or Tel2 causes disassembly of mTORC1 and mTORC2. These results indicate that Tti1 and Tel2 are important not only for mTOR stability but also for assembly of the mTOR complexes to maintain their activities.