GLUCOSE SENSING AND SIGNALLING IN YEAST

描述(申请人提供)：葡萄糖为生命提供能量。大多数细胞更喜欢它作为它们的碳和能源，并且必须迅速和准确地感觉到它。对于酵母(酿酒酵母)来说，这一点尤其明显，因为它利用葡萄糖的方式不同寻常。酵母细胞必须检测到葡萄糖供应的波动，并迅速调整自己的新陈代谢，以最大限度地利用可用的东西。酵母菌控制葡萄糖利用的第一个限速步骤--向细胞内运输。我们发现了两个新的葡萄糖传感器，它们启动了一条信号转导途径，调节编码葡萄糖转运蛋白的HXT基因的表达。这些葡萄糖传感器是一类与营养转运蛋白相关的新型营养受体的创始成员；我们想知道它们是否起作用。由葡萄糖传感器启动的信号转导途径现在是焦点；我相信我们已经准备好将其提升到与其他信号转导途径一样的理解水平。这一葡萄糖传感途径始于细胞膜，Snf3和Rgt2葡萄糖传感器与Yock1蛋白激酶偶联。葡萄糖信号被转导到抑制HXT基因的Rgt1转录因子，并被MTH1和Std1抑制。葡萄糖与传感器的结合导致Yck 1磷酸化MTH1和Std1，从而将它们定位于泛素化和降解。我们想知道葡萄糖信号是如何由传感器产生的，该信号如何激活Yck 1对MTH1和Std1的磷酸化，MTH1和Std1如何调节Rgt1的功能，以及信号通路如何与代谢网络相结合。我们未来四年的具体目标是：目标1：了解葡萄糖信号是如何在途径的顶端产生和转导的。Aim1A：葡萄糖传感器是葡萄糖受体吗？Aim1B：传感器和传输器之间功能差异的基础是什么？Aim1C：Yck 1在信号通路中的作用是什么？Aim1D：我们是否遗漏了SRR途径的任何组成部分？目的2：了解葡萄糖信号如何调节Rgt1抑制子。目的：RGT1的抑制子区域是如何抑制其功能的？Aim2B：Rgt1的磷酸化残基的作用是什么？Aim2C：MTH1和Std1是如何抑制Rgt1的抑制子区域的？目的3：了解葡萄糖信号通路如何与代谢网络整合。目的3A：MTH1在腺嘌呤生物合成和一碳代谢中的作用是什么？目的3B：信号通路是如何在其他酵母中部署的？它是如何演变的？与公共健康相关：葡萄糖为生命提供燃料。大多数细胞喜欢它作为它们的食物来源；一些细胞需要它。细胞已经进化出许多复杂的机制来感知葡萄糖并对其做出适当的反应。这一点在面包酵母(S.cerevisiae)中尤其明显，它有几个高度进化的调节机制来感知和利用它在生命周期中遇到的广泛不同的葡萄糖量。这些调节机制决定了酵母的独特新陈代谢，酵母与许多类型的肿瘤细胞共享一种生活方式。我们的长期目标是了解酵母细胞如何感知和响应葡萄糖。我们正在研究一种葡萄糖传感系统，其关键组件是位于细胞膜上的新型葡萄糖受体，它可以检测葡萄糖，向细胞发送影响基因表达和影响新陈代谢的信号。我们的目标是了解这些新型受体是如何工作的。

DESCRIPTION (provided by applicant): Glucose fuels life. Most cells prefer it as their carbon and energy source, and must rapidly and accurately sense it. This is particularly apparent for yeast (S. cerevisiae) because of the unusual way it uses glucose. Yeast cells must detect fluctuations in the glucose supply and rapidly adjust their metabolism to make maximum use of what is available. Yeasts control glucose utilization at its first, rate- limiting step - transport into the cell. We discovered two novel glucose sensors that initiate a signal transduction pathway that regulates expression of HXT genes encoding glucose transporters. These glucose sensors are the founding members of a novel class of nutrient receptor related to nutrient transporters; we would like to know they work. The signal transduction pathway initiated by the glucose sensors is now in focus; I believe we are poised to elevate it to a level of understanding on par with other signal transduction pathways. This glucose sensing pathway begins at the cell membrane with the Snf3 and Rgt2 glucose sensors, which are coupled to the Yck1 protein kinase. The glucose signal is transduced to the Rgt1 transcription factor, which represses HXT genes, and is inhibited by Mth1 and Std1. Glucose binding to the sensors causes Yck1 to phosphorylate Mth1 and Std1, thereby targeting them for ubiquitination and degradation. We want to know how the glucose signal is generated by the sensors, how the signal activates phosphorylation of Mth1 and Std1 by Yck1, how Mth1 and Std1 regulate Rgt1 function, and how the signaling pathway meshes with the metabolic network. Our Specific Aims for the next four years are: Aim 1: Learn how the glucose signal is generated and transduced at the top of the pathway. Aim1A: Are the glucose sensors glucose receptors? Aim1B: What is the basis for functional differences between sensors and transporters? Aim1C: What is the role of Yck1 in the signaling pathway? Aim1D: Are we missing any components of the SRR pathway? Aim 2: Learn how the glucose signal regulates the Rgt1 repressor. Aim2A: How does the antirepressor region of Rgt1 inhibt its function?. Aim2B: What is the role of phosphorylated residues of Rgt1? Aim2C: How do Mth1 and Std1 inhibit the antirepressor region of Rgt1? Aim 3: Learn how the glucose signaling pathway is integrated with the metabolic network. Aim 3A: What is the role of Mth1 in adenine biosynthesis and one-carbon metabolism? Aim 3B: How is the signaling pathway deployed in other yeasts? How did it evolve? PUBLIC HEALTH RELEVANCE: Glucose fuels life. Most cells prefer it as their food source; some cells require it. Cells have evolved numerous and sophisticated mechanisms for sensing glucose and responding to it appropriately. This is especially apparent in Bakers' yeast (S. cerevisiae), which has several highly evolved regulatory mechanisms for sensing and utilizing the widely varying amounts of glucose it encounters during its lifetime. These regulatory mechanisms determine the distinctive metabolism of yeast, a lifestyle it shares with many kinds of tumor cells. Our long-term goal is to understand how yeast cells sense and respond to glucose. We are studying a glucose sensing system whose key components are novel glucose receptors that sit in the cell membrane and detect glucose, sending a signal into the cell that affects gene expression and influences metabolism. We aim to learn how these novel receptors work.