The Biology and Biochemistry of Lipid Transfer Protein-Regulated Phosphoinositide Signaling

摘要 这项研究的主要目的是了解真核细胞如何组织主要的脂质。 信号通路，以及这些通路如何以赋予空间和时间特异性的方式进行，以及 生物学结果的特异性。感兴趣的系统是磷酸肌醇信号传导和一般的 细胞如何在功能上将一个相当简单的化学密码转化为大量多样的生物信息的问题。 活动实验的目标是执行一个详细的功能分析，一类调查不足， 蛋白质-磷脂酰肌醇（PtdIns转移蛋白（PITPs））-谁发挥决定性作用， PtdIns 4-OH激酶活性的功能通道。为此，两个独立的，但概念上 联系起来，方向将追求：（i）利用Sec 14-超家族的原型成员及其 五种酵母旁系同源物作为实验模型，和（ii）利用哺乳动物新皮层的发育作为 生理背景，以确定三种可溶性哺乳动物PITP的作用机制 同种型-类似于StART的1类PITPs -与Sec 14样蛋白家族完全无关 在结构方面。Sec 14类和StART类PITP都是在 磷脂代谢和高尔基体/膜信号传导/运输功能的界面。拟议 研究将测试与以下内容相关的特定假设：（i）真菌和哺乳动物的PITP如何结合和交换 它们的脂质配体，（ii）个体PITP调节脂质代谢特定步骤的机制 在酵母和哺乳动物（特别是神经干细胞及其后代），以及（iii）如何氧固醇结合 蛋白（OSBP）相关蛋白在调节中对抗Sec 14依赖性PtdIns-4-磷酸信号传导 高尔基体PtdIns-4-P信号传导以及这种脂质结合蛋白拮抗作用如何在细胞周期控制中发挥作用 通过细胞周期的G1期进展。这些研究将澄清关键的未回答的问题 关于PITPs的功能机制，Sec 14样和StART样的机制 PITP将脂质代谢与PtdIns激酶信号传导偶联，并且PITP功能的更多全球分支 与氧固醇结合蛋白家族成员（ORP）的相互作用。越来越多的继承人 神经变性和神经发育疾病，以及增殖性疾病（例如癌症）， 是由于Sec 14样和StART样PITP中的不一致性。因此，拟议的研究将提供 这两个新的和基本的信息，直接关系到分子机制， 调节和组织真核生物中的信号转导，保护哺乳动物免受精神错乱的疾病 细胞增殖和神经变性。

Abstract The large objective of the proposed research is to understand how eukaryotic cells organize major lipid signaling pathways, and how these do so in a manner that imparts both spatial and temporal specificity, and specificity of biological outcome. The system of interest is phosphoinositide signaling and the general question of how cells functionally channel a rather simple chemical code into a large diversity of biological activities. The experimental goal is to execute a detailed functional analysis of an underinvestigated class of proteins -- the phosphatidylinositol (PtdIns transfer proteins (PITPs) – who play a determining role in the functional channeling of PtdIns 4-OH kinase activities. To that end, two independent, but conceptually linked, directions will be pursued that: (i) exploit the prototypical member of the Sec14-superfamily and its five yeast paralogs as experimental models, and (ii) exploit development of the mammalian neocortex as physiological context with which to identify mechanisms of action of the three soluble mammalian PITP isoforms – the StART-like Class 1 PITPs – that are completely unrelated to the Sec14-like family of proteins in terms of structure. Both Sec14-like and StART-like PITPs are essential factors that operate at the interface of phospholipid metabolism and Golgi/ membrane signaling/trafficking functions. The proposed studies will test specific hypotheses that relate to: (i) how fungal and mammalian PITPs bind and exchange their lipid ligands, (ii) the mechanisms by which individual PITPs regulate specific steps of lipid metabolism in yeast and mammals (particularly neural stem cells and their progeny), and (iii) how the oxysterol binding protein (OSBP)-related proteins work against Sec14-dependent PtdIns-4-phosphate signaling in regulating Golgi PtdIns-4-P signaling and how this lipid binding protein antagonism is played out in control of cell cycle progression through the G1 phase of the cell cycle. These studies will clarify key unanswered questions regarding the mechanism of function of PITPs, the mechanisms by which both Sec14-like and StART-like PITPs couple lipid metabolism to PtdIns kinase signaling, and more global ramifications of PITP functional interactions with the oxysterol binding protein family members (ORPs). A growing number of inherited neurodegenerative and neurodevelopmental diseases, and diseases of proliferative disorders (e.g. cancer), are attributed to insufficiencies in Sec14-like and StART-like PITPs. Thus, the proposed studies will provide both new and fundamental information that bears directly on molecular mechanisms by which PITPs regulate and organize signal transduction in eukaryotes, and protect mammals from diseases of deranged cell proliferation and neurodegeneration.