Point mutations in TOR confer Rheb-independent growth in fission yeast and nutrient-independent mammalian TOR signaling in mammalian cells
Point mutations in TOR confer Rheb-independent growth in fission yeast and nutrient-independent mammalian TOR signaling in mammalian cells
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DOI：
10.1073/pnas.0608510104
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发表时间：
2007-02-27
影响因子：
11.1
通讯作者：
Tamanoi, Fuyuhiko
中科院分区：
文献类型：
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作者：
Urano, Jun;Sato, Tatsuhiro;Tamanoi, Fuyuhiko
Rheb是Ras超家族GP结合蛋白的独特成员。我们以及其他人以前已经表明，Rheb是TSC/TOR信号通路的关键组成部分。在裂殖酵母中，Rheb由rhb 1基因编码。Rhb 1 p对生长至关重要，并直接与Tor 2 p相互作用。在这篇文章中，我们报告了Tor 2蛋白中22个单一氨基酸的变化，这些变化使其能够在没有Rhb 1 p的情况下生长。这些突变体还表现出降低的交配效率。有趣的是，突变位于Tor 2蛋白的C-末端一半，主要聚集在FAT和激酶结构域内。我们注意到FAT结构域（L1310 P）和激酶结构域（E2221 K）突变对生长和交配的影响存在一些差异。虽然Tor 2 p突变绕过了Rhb 1 p的生长需求，但它们无法抑制Rhb 1 p对应激和有毒氨基酸的抗性需求，这表明Rhb 1 p具有多种功能。在哺乳动物系统中，我们发现携带类似突变（L1460 P或E2419 K）的哺乳动物雷帕霉素靶蛋白（mTOR），尽管对雷帕霉素敏感，但即使在细胞缺乏营养时也表现出组成型激活。这些突变在与Raptor、Rictor或mLST 8形成复合物的能力方面没有显示出显著差异。此外，我们提供的证据表明突变mTOR可以与野生型mTOR复合，并且这种异二聚体在营养饥饿的细胞中具有活性。
Rheb is a unique member of the Ras superfamily GTP-binding proteins. We as well as others previously have shown that Rheb is a critical component of the TSC/TOR signaling pathway. in fission yeast, Rheb is encoded by the rhb1 gene. Rhb1p is essential for growth and directly interacts with Tor2p. In this article, we report identification of 22 single amino acid changes in the Tor2 protein that enable growth in the absence of Rhb1p. These mutants also exhibit decreased mating efficiency. Interestingly, the mutations are located in the C-terminal half of the Tor2 protein, clustering mainly within the FAT and kinase domains. We noted some differences in the effect of a mutation in the FAT domain (L1310P) and in the kinase domain (E2221K) on growth and mating. Although the Tor2p mutations bypass Rhb1p's requirement for growth, they are incapable of suppressing Rhb1p's requirement for resistance to stress and toxic amino acids, pointing to multiple functions of Rhb1p. In mammalian systems, we find that mammalian target of rapamycin (mTOR) carrying analogous mutations (L1460P or E2419K), although sensitive to rapamycin, exhibits constitutive activation even when the cells are starved for nutrients. These mutations do not show significant difference in their ability to form complexes with Raptor, Rictor, or mLST8. Furthermore, we present evidence that mutant mTOR can complex with wild-type mTOR and that this heterodimer is active in nutrient-starved cells.