The molecular mechanisms of nutrient- and stress-dependent mTORC1 regulation mediated by human Sestrin2.

营养和胁迫依赖的分子机制 人Sestrin 2介导的mTORC1调控。 项目摘要 MTOR复合体1(MTORC1)是一种重要的营养感受器，其慢性 通过营养过剩激活可引起多种代谢病理，如胰岛素 耐药性和II型糖尿病。然而，大多数mTORC1的药物抑制剂， 非特异性地抑制mTORC2-另一个对 介导胰岛素信号转导--因此不适合糖尿病治疗。 Sestrins(Sesn)是最近发现的mTORC1抑制因子。MTORC1-抑制 Sesns的功能可以减缓大多数高营养和肥胖的发展 相关的新陈代谢病理。重要的是，SENS不抑制mTORC2和 相反，通过抑制mTORC1来上调其活性。相应地，转基因 Sesn过表达对慢性mTORC1肝损伤的保护作用 胰岛素抵抗的激活、发展和糖尿病的病理进展。 这些结果表明，SENS及其下游信号通路可能具有 作为肥胖相关疾病的药物靶点的治疗潜力。 最近，我们实验室和其他实验室的一些研究已经澄清了分子 Sesns的靶点，这使得对Sesns如何抑制mTORC1有了更清晰的理解。AS 广泛的遗传学和细胞生物学研究的结果，明确的上位关系 在GATOR2、GATOR1、RAG GTP酶和mTORC1之间建立了GATOR2、GATOR1、RAG GTP酶。 此外，最近的几篇论文也表明，一种氨基酸亮氨酸可以 与Sesn结合并调节其活动。 尽管它具有生理意义，但它所依据的生化和分子基础 这些蛋白质之间的相互作用和信号传递仍然完全未知。如果没有 对分子水平机制的理解，几乎不可能理性地 设计化学探针来调节这一信号级联。作为这项努力的一部分，我们 最近确定了人类Sestrin2(HSesn2)的第一个晶体结构，并 目前正计划将其用作理解依赖于SESN的 信号转导途径。我们的长期目标是定义生化和 Sesn依赖的信令中每个信令组件的结构特性 级联，并揭示对此功能至关重要的可用药结构主题 信号通路。结合使用X射线结晶学、分子电子 显微镜(EM)、细胞生物学和果蝇/小鼠遗传学实验，我们将 阐明hSesn2的结构、生化和细胞生物学作用及其信号转导 中间体-GATOR1和GATOR2-抑制mTORC1。分子 从这些研究中确定的机制和结构主题有望揭示 MTORC1调节药物未来发展的多个新药靶点 药物，这将是临床上有意义的，以减少进展的多元化 由高营养和肥胖引起的代谢病理。

Title: The molecular mechanisms of nutrient- and stress-dependent mTORC1 regulation mediated by human Sestrin2. Project Summary The mTOR complex 1 (mTORC1) is an important nutrient sensor whose chronic activation by overnutrition can provoke diverse metabolic pathologies such as insulin resistance and type II diabetes. Most pharmacological inhibitors of mTORC1, however, non-specifically suppress mTORC2—another mTOR complex that is critical for mediating insulin signal transduction—and thus inappropriate for diabetes treatment. Sestrins (Sesns) are recently identified mTORC1 suppressors. mTORC1-inhibitory function of Sesns attenuates development of most hypernutrition- and obesity- associated metabolic pathologies. Importantly, Sesns does not inhibit mTORC2 and rather upregulates its activity by suppressing mTORC1. Correspondingly, transgenic Sesn overexpression was highly effective in protecting liver from chronic mTORC1 activation, development of insulin resistance and progression of diabetic pathologies. These results suggest that Sesns and their downstream signaling pathway may have a therapeutic potential as a drug target toward the obesity-associated diseases. Recently, a number of studies by our labs and others have clarified the molecular targets of Sesns, which led to a clearer understanding of how Sesns inhibit mTORC1. As a result of extensive genetics and cell biology studies, a clear epistatic relationship between GATOR2, GATOR1, Rag GTPases and mTORC1 was established. Furthermore, a couple of recent papers also suggested that an amino acid leucine can bind to Sesns and modulates their activities. Despite its physiological significance, the biochemical and molecular basis by which these proteins interact with and signal to each other is still completely unknown. Without an understanding of the molecular level mechanism, it is nearly impossible to rationally design chemical probes to modulate this signaling cascade. As a part of this effort, we have recently determined the first crystal structure of human Sestrin2 (hSesn2), and are currently planning to use it as a starting platform for understanding the Sesn-dependent signal transduction pathway. Our long-term goal is to define the biochemical and structural properties of each signaling component within the Sesn-dependent signaling cascade and to reveal druggable structural motifs that are critical for functionality of this signaling pathway. Using a combination of X-ray crystallography, molecular electron microscopy (EM), cell biology and Drosophila/mouse genetics experiments, we will elucidate the structural, biochemical and cell-biological role of hSesn2 and its signaling intermediates—GATOR1 and GATOR2—in mTORC1 suppression. The molecular mechanisms and structural motifs identified from these studies are expected to reveal many new drug targets for future development of mTORC1-modulating pharmaceutical agents, which will be clinically significant for reducing the progression of diverse metabolic pathologies caused by hypernutrition and obesity.