Understanding the regulation of polyglucan biosynthesis in eukaryotic cells

活细胞中的碳储存对于生物体的健康和生存至关重要。特别是，葡萄糖（Glc），作为聚葡聚糖储存，如植物中的淀粉和许多其他生物体中的糖原，在其各自的生命周期中起着至关重要的作用。淀粉是在高等植物的质体内合成的水不溶性聚葡聚糖，作为短期和长期能量储存，而糖原是水溶性的，作为酵母和动物中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，也是驯化谷物和草产量的主要决定因素，其淀粉胚乳提供了人类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。我的实验室对这一重要途径的调控进行了超过15年的研究，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等技术，了解其在决定淀粉结构和产量方面的作用。我们已经表明，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物的组装和拆卸，在淀粉合成的翻译后控制中发挥重要作用。除了核心生物合成途径之外，许多辅助组分，包括必需的非催化蛋白质例如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合成。许多糖原代谢的酶受蛋白质磷酸化的调节，但与植物中的情况相反，几乎不知道糖原合成酶之间的蛋白质-蛋白质相互作用。 我研究项目的总体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。通过研究这两个相关的碳储存系统，我们将获得有价值的洞察这两个重要途径的翻译后控制的平行模式。在接下来的五年里，我将解决我们的知识差距在关键领域的途径储存淀粉沉积在谷物胚乳，控制质体内的淀粉合成，和糖原生物合成的调节。具体来说，我将研究1）蔗糖代谢途径和淀粉合成前体ADPGlc的形成，在谷物胚乳细胞质中的翻译后调节2）质体ADPGlc的合成，和3）通过分析糖原形成的关键阶段所涉及的蛋白质-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节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.