PHOSPHATIDYLINOSITOL SIGNALING AND HUMAN DISEASE

本项目旨在明确肌醇信号反应在疾病发病机制中的作用。我们将研究肌醇1,3,4-5/6-激酶在脂肪细胞分化中的作用。这种酶催化形成六磷酸肌醇（IP6）的第一步，这是哺乳动物生命所必需的。初步研究表明，在脂肪细胞分化过程中，该酶和其他导致IP6产生的酶高度表达，该途径中的一些代谢物可能实际上导致了脂肪细胞的发育。我们将使用过表达和RNAi研究来定义致病分子。在另一项研究中，我们计划确定PI(3,4)P2水平升高的小鼠潜在的血栓形成前表型。我们提出，升高的水平是由于在Weeble突变小鼠中发生的4-ptaseI缺乏引起的。我们用从Weeble胚胎中取出的胎儿肝移植而成的正常小鼠，经致命照射后制成了辐射嵌合小鼠。因此，Weeble突变仅限于血细胞，初步实验表明这些动物具有血栓表型。我们将在激光损伤模型中研究血小板功能和体内血栓形成。我们将研究肌管蛋白PI 3-ptase家族中一个研究较少的分支，即MTMR6、MTMR7、MTMR8及其非活性伙伴MTMR9的功能。这些蛋白在应激诱导的细胞凋亡中起着不明确的作用。我们最近了解到，在我们实验室发现的另一种酶的突变是导致严重神经退行性乔伯特综合征的原因。这种酶是肌醇多磷酸5-磷酸酶eiv，一种脂质特异性的5-PtaseIV。Jos Gleeson博士（加州大学圣地亚哥分校/HHMI）在Joubert综合征家族中发现了5种不同的突变，并向我们发送了细胞和结构来定义这些突变的生物学后果。总之，我们使用肌醇生物化学来确定肌醇代谢障碍的表型和基因型。

This project aims to define the roles of inositol signaling reactions in the pathogenesis of disease. We will study the role of inositol 1,3,4-5/6-kinase in fat cell differentiation. This enzyme catalyzes the first step in formation of inositol hexakisphosphate (IP6) which is essential for life in mammals. Preliminary studies indicate that the enzyme and others leading to IP6 production are highly expressed during fat cell differentiation and that some metabolite in this pathway may actually cause fat cell development. We will use overexpression and RNAi studies to define the causal molecule. In another study we plan to determine the potentially prothrombotic phenotype of mice with elevated levels of PI(3,4)P2. We propose that the elevated levels arise from deficiency of 4-ptaseI that occur in Weeble mutant mice. We have made radiation chimeric mice from lethally irradiated normal mice rescued by fetal liver transplants from Weeble embryos. Thus the Weeble mutation is restricted to blood cells and preliminary experiments suggest that these animals have a thrombotic phenotype. We will study platelet function and in vivo thrombosis in a laser injury model. We will investigate the functions of a little studied sub branch of the myotubularin PI 3-ptase family namely MTMR6, MTMR7, MTMR8 and their inactive partner MTMR9. These proteins play undefined roles in stress-induced apoptosis. We recently learned that mutations in another enzyme discovered in our lab are the cause of a severe neurodegeneration Jobert syndrome. The enzyme is inositol polyphosphate 5-phosphataseIV a lipid specific 5-PtaseIV. Dr Jos Gleeson (UCSD/HHMI) has found 5 different mutations in families with Joubert syndrome and has sent us cells and constructs to define the biological consequences of these mutations. In summary we use inositol biochemistry to determine the phenotype vs genotype of disorders of inositol metabolism.