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

摘要 这项拟议研究的大目标是了解真核细胞如何组织主要脂肪。 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做到这一点，以及 生物结果的特异性。感兴趣的系统是磷脂酰肌醇信号和一般 细胞如何在功能上将一个相当简单的化学密码导入到各种生物中的问题 活动。实验的目标是对一类未被调查的 蛋白质--磷脂酰肌醇(PtdIns Transfer Proteins，PITPs)--在 PtdIns 4-OH激酶活性的功能性通道。为此，两个独立的，但概念上 联系起来，将寻求以下方向：(1)利用Sec14-超级家族的原型成员及其 5个酵母菌作为实验模型，以及(Ii)利用哺乳动物新皮质的发育作为 识别三种可溶性哺乳动物PITP作用机制的生理背景 与Sec14-like蛋白家族完全无关的异构体--Start-like Class 1 PITPs 在结构方面。类Sec14和类Start的PITP都是在 磷脂代谢和高尔基体/膜信号/转运功能的接口。建议数 研究将检验与以下相关的具体假设：(I)真菌和哺乳动物的PITP如何结合和交换 它们的脂类配体，(Ii)个别PITP调节脂类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)中，以及(Iii)氧固醇如何结合 蛋白质(OSBP)相关蛋白在调节中对抗Sec14依赖的PtdIns-4-磷酸信号 高尔基体PtdIns-4-P信号转导机制及其在细胞周期调控中的作用 进入细胞周期的G1期。这些研究将澄清尚未回答的关键问题 关于PITPs的作用机制，Sec14样蛋白和Start样蛋白的机制 PITP将脂代谢与PtdIns激酶信号相结合，并对PITP功能的更多全球分支进行研究 与氧固醇结合蛋白家族成员(ORPs)的相互作用。越来越多的继承人 神经退行性疾病和神经发育疾病，以及增殖性疾病(如癌症)， 归因于类Sec14和类Start的PITP的不足。因此，拟议的研究将提供 直接与PITPs的分子机制有关的新的和基本的信息 调控和组织真核生物的信号转导，保护哺乳动物免受错乱疾病的侵袭 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.