Understanding the regulation of polyglucan biosynthesis in eukaryotic cells

活细胞中的碳储存对生物体的健康和生存至关重要。特别是，葡萄糖(GLC)在植物中以淀粉等多聚葡聚糖的形式储存，在许多其他生物中以糖原的形式储存，在它们各自的生命周期中发挥着至关重要的作用。淀粉是高等植物体内合成的一种不溶于水的多聚葡聚糖，作为短期和长期的能量储存，而糖原是一种水溶性的，在酵母和动物中是一种容易获得的主要储备碳水化合物。 淀粉是世界上最重要的农产品之一，也是驯化谷类和牧草产量的主要决定因素，其淀粉胚乳提供了人和牲畜的大部分热量摄入。参与淀粉生物合成的酶活性的协调和合作开始被理解。我的实验室已经研究了这一重要途径的调控超过15年，应用生物化学、分子生物学、生物信息学、植物生理学和细胞生物学来了解它在决定淀粉结构和产量中的作用。我们已经证明，蛋白质-蛋白质相互作用和蛋白质磷酸化通过调节许多酶的活性，以及控制特定蛋白质复合体的组装和拆卸，在淀粉合成的翻译后控制中发挥重要作用。除了核心的生物合成途径外，许多辅助成分，包括必需的非催化蛋白，如14-3-3S(调节蛋白质-蛋白质相互作用的真核蛋白质)，蛋白激酶和磷酸酶，负责调节淀粉的合成。糖原代谢的许多酶都受蛋白质磷酸化的调节，但与植物的情况相反，糖原合成酶之间的蛋白质-蛋白质相互作用几乎一无所知。 我的研究计划的主要目标是进一步了解植物中淀粉生物合成和酵母中糖原合成的翻译后控制。通过对碳储存的两个相关系统的研究，我们将对这两条重要途径的翻译后控制的平行模式有价值的洞察。在接下来的五年里，我将解决我们在谷类胚乳中储存淀粉沉积途径、质体中淀粉合成的控制以及糖原生物合成调控等关键领域的知识空白。具体地说，我将研究1)谷物胚乳细胞质中蔗糖代谢和淀粉合成前体ADPGlc形成的途径的翻译后调节，2)质质ADPGlc合成，以及3)通过分析参与糖原形成关键阶段的蛋白质-蛋白质相互作用组来研究酵母中的平行调节系统。了解控制细胞碳储存的调控系统是对农业和哺乳动物健康应用知识的重要贡献。

Carbon storage in living cells is essential for the fitness and survival of organisms. In particular, glucose (Glc), stored as polyglucans such as starch in plants and glycogen in many other organisms, serve crucial roles throughout their respective life cycles. Starch is a water insoluble polyglucan synthesized inside plastids of higher plants acting as a short- and long-term energy store, whereas glycogen is water-soluble, acting as a readily accessible major reserve carbohydrate in yeasts and animals. Starch is one of the most important agricultural commodities in the world, and the major determinant of yield in domesticated cereals and grasses, whose starchy endosperms provide the bulk of caloric intake of humans and livestock. The coordination and cooperation of enzyme activities involved in starch biosynthesis is beginning to be understood. My laboratory has studied the regulation of this important pathway for more than 15 years, applying biochemistry, molecular biology, bioinformatics, plant physiology and cell biology to understand its role in determining starch structure and yield. We have shown that protein-protein interactions and protein phosphorylation play important roles in the post-translational control of starch synthesis by regulating many enzyme activities, as well as controlling assembly and disassembly of specific protein complexes. In addition to the core biosynthetic pathway, many auxiliary components, including essential non-catalytic proteins e.g. 14-3-3s (eukaryotic proteins which regulate protein-protein interactions), protein kinases and phosphatases are responsible for regulating starch synthesis. Many enzymes of glycogen metabolism are regulated by protein phosphorylation, but in contrast to the situation in plants, almost nothing is known of protein-protein interactions between the enzymes of glycogen synthesis. The broad goal of my research program is to further understand the post translational control of starch biosynthesis in plants and glycogen synthesis in yeast. By studying the two related systems of carbon storage we will gain valuable insight into parallel modes of post-translational control of these two important pathways. Over the next five years, I will address gaps in our knowledge in key areas of the pathway of storage starch deposition in cereal endosperms, the control of starch synthesis inside plastids, and the regulation of glycogen biosynthesis. Specifically, I will investigate the post-translational regulation of 1) pathways of sucrose metabolism and formation of the precursor for starch synthesis, ADPGlc, in the cytoplasm of cereal endosperm 2) plastidial ADPGlc synthesis, and 3) investigate parallel regulatory systems in yeast by analyzing the protein-protein interactome involved in key stages of glycogen formation. Understanding the regulatory systems controlling cellular carbon storage represents an important contribution to knowledge with applications in agriculture and mammalian health.