Genetic Regulation of Phospholipid Synthesis in Yeast

描述(申请人提供)：酵母细胞合成一种典型的真核磷脂混合物，使用的途径和酶与高等真核生物的途径和酶基本相似，确保使用该模型系统产生的见解将与人类新陈代谢和健康相关。有人建议进行实验，利用当真核生物中磷脂的前体肌醇从活跃分裂的酵母细胞的生长介质中添加或移除时，磷脂、鞘磷脂和储存脂的合成和周转发生的快速和戏剧性的变化。酵母中对肌醇可获得性作出反应的许多脂类与真核细胞中的应激反应信号有关。随着肌醇可利用性的突然变化，这些脂类中发生的快速变化将与 信号和基因表达。该策略将用于定义特定的信令角色 脂类：内质网和质膜中的磷脂酸、二酰甘油和磷脂酰肌醇4-磷酸和鞘磷脂。磷脂酸不仅是一种信号脂质，而且是膜生物发生所必需的磷脂的关键前体。或者，磷脂酸通过去磷酸化作为前体，用于生产二酰基甘油，后者又作为合成磷脂和三酰甘油的前体，三酰甘油是脂滴的主要成分。控制三酰甘油合成的代谢调节与理解人类健康相关疾病的潜在因素高度相关，如慢性肥胖症。在缺乏肌醇的酵母细胞中，磷脂合成减少，三酰甘油水平上升，类似于导致肥胖的代谢变化。为探索这一重要调控机制而设计的实验被提出。脂类及其代谢产物参与了包括人类在内的高等真核生物膜生物发生、细胞生长和增殖的许多复杂信号通路。然而，在这些复杂的细胞过程中，个别脂质和相关代谢物的具体作用是 通常被涉及的代谢的复杂性以及许多潜在的信号脂质作为其他此类脂质的前体的事实所掩盖。此外，在正在进行的脂肪代谢过程中产生的许多信号都是瞬时的，正确识别特定的信号分子可能取决于能否准确地测量它并在活跃的新陈代谢背景下观察它的流量。这项建议中描述的实验利用了酵母模型系统的优势和相关脂代谢的快速变化以及克服这些障碍的信号。

DESCRIPTION (provided by applicant): Yeast cells synthesize a typically eukaryotic mixture of phospholipids, using pathways and enzymes that are largely similar to those in higher eukaryotes, ensuring that insights generated using this model system will be relevant to human metabolism and health. Experiments are proposed that exploit the rapid and dramatic changes that occur in the synthesis and turnover of phospholipids, sphingolipids and storage lipids when inositol, a precursor of phospholipids in eukaryotes, is added or removed from the growth medium of actively dividing yeast cells. Many of the lipids that respond to inositol availability i yeast are implicated in stress response signaling in eukaryotic cells. Rapid changes occurring in such lipids in response to abrupt changes in inositol availability will be correlated to changes in signaling and gene expression. This strategy will be used to define the specific signaling roles of the lipids; phosphatidic acid, diacylglycerol, and phosphatidylinositol 4- phosphate and sphingolipids in the endoplasmic reticulum and the plasma membrane. Phosphatidic acid not only serves as a signaling lipid but is also a key precursor of phospholipids essential for membrane biogenesis. Alternatively, phosphatidic acid serves as precursor via dephosphorylation for the production of diacylgycerol, which in turn serves as a precursor in the synthesis of both phospholipids and triacylglycerol, a major component of lipid droplets. The metabolic regulation controlling the synthesis of triacylglycerol is highly relevant to understanding factors underlying human health related conditions, such as chronic obesity. In yeast cells starved for inositol, phospholipid synthesis decreases and triacylglycerol levels increase, mimicking metabolic changes leading to obesity. Experiments designed to probe the mechanism of this important regulation are proposed. Lipids and metabolites derived from them have been implicated in many of the complex signaling pathways that regulate membrane biogenesis, cell growth and proliferation in higher eukaryotes, including humans. However, the specific roles of individual lipids and related metabolites in these complex cellular processes are often obscured by the complexity of the metabolism involved and by the fact that many potential signaling lipids serve as precursors to other such lipids. Moreover, many of the signals generated during ongoing lipid metabolism are transient and the correct identification of the specific signaling molecule may depend on being able to measure it accurately and observe its flux in the context of active metabolism. The experiments described in this proposal exploit the advantages of the yeast model system and the rapidity of changes in correlated lipid metabolism and signaling to overcome such barriers.