Functional annotation of the oxidized lipid hydrolase PLA2G7 in neurodegeneration

 描述（由申请人提供）：PLA 2G 7基因编码50 kDa分泌型丝氨酸水解酶。对PLA 2G 7的大部分关注集中在其作为心血管疾病标志物的潜力上;然而，PLA 2G 7在整个哺乳动物生物体中表达，包括脑。PLA 2G 7的抑制已经在患有阿尔茨海默病的人类患者中显示出治疗益处，但是该酶的体内功能的特征很差。我们的实验室已经开发了一套工具来研究PLA 2G 7在小鼠脑中的作用，包括PLA 2G 7-/-小鼠，PLA 2G 7的选择性中枢活性抑制剂，以及靶向接合测定来确认抑制剂在体内的作用。使用这些化学和遗传工具，结合基于质谱的脂质组学和蛋白质组学研究，我们建议使用纵向研究确定PLA 2G 7在中枢神经系统中的代谢功能，并定义其在两种小鼠神经退行性变模型中的作用。在具体目标1中，我们将使用PLA 2G 7-/-小鼠和选择性PLA 2G 7抑制剂JMN 21绘制PLA 2G 7破坏小鼠脑中的年龄依赖性脂质变化。这些研究将利用非靶向和靶向液相色谱-质谱法来鉴定和定量脑代谢物中的PLA 2G 7依赖性变化。在具体目标2中，我们将鉴定神经炎症和神经变性的两种动物模型中的PLA 2G 7依赖性脂质变化：ABHD 12-/-小鼠，罕见人类遗传性病症PHARC（多发性神经病、听力损失、共济失调、色素性视网膜病和白内障）的小鼠模型，和B6.Cg-Tg（GFAP-APOE_14）1Hol Apoetm 1Unc/J（apoE 4）小鼠，阿尔茨海默病的小鼠模型。大约15%的人携带apoE ε4等位基因，但至少40%的晚发性AD患者存在该等位基因;此外，具有一个ε4等位基因的个体患AD的可能性高3至4倍，具有纯合ε4等位基因的个体患AD的风险高12倍，比值比远大于其他晚发性AD风险因素的比值比。PLA 2G 7与apoE直接相关，理想地将其定位为调节apoE 4转基因小鼠中的代谢变化，特别是涉及脂质氧化。在具体目标3中，我们将确定PLA 2G 7调节的脂质途径对ABHD 12-/-和apoE 4小鼠中神经炎症和神经变性的功能贡献。我们预期这些研究将提供描述性代谢分析和PLA 2G 7抑制或缺失的相应功能结果，其与人类病症（包括PHARC和阿尔茨海默病，最普遍的神经退行性疾病）显著相关。在ABHD 12-/-和apoE 4小鼠中鉴定PLA 2G 7的代谢功能并将PLA 2G 7缺失或抑制所赋予的代谢变化与治疗效果相关联，将提供对PLA 2G 7功能的更好理解，并鉴定其在人类疾病中的治疗效果的基础。

 DESCRIPTION (provided by applicant): The PLA2G7 gene encodes a 50 kDa secreted serine hydrolase. Much of the focus on PLA2G7 has centered on its' potential as a marker for cardiovascular disease; however, PLA2G7 is expressed throughout the mammalian organism, including the brain. Inhibition of PLA2G7 has demonstrated therapeutic benefits in human patients with Alzheimer's disease, yet the in vivo function of the enzyme is poorly characterized. Our laboratory has developed a suite of tools to study the role of PLA2G7 in mouse brain including PLA2G7-/- mice, selective, centrally active inhibitors of PLA2G7, and target engagement assays to confirm inhibitor action in vivo. Using these chemical and genetic tools in combination with mass spectrometry-based lipidomic and proteomic studies we propose to determine the metabolic function of PLA2G7 in the central nervous system using longitudinal studies and define its role in two mouse models of neurodegeneration. In specific aim 1 we will map age-dependent lipid changes in the brains of PLA2G7-disrupted mice using PLA2G7-/- mice and the selective PLA2G7 inhibitor JMN21. These studies will utilize untargeted and targeted liquid chromatography- mass spectrometry to identify and quantify PLA2G7-dependent changes in brain metabolites. In specific aim 2 we will identify PLA2G7-dependent lipid changes in two animal models of neuroinflammation and neurodegeneration: ABHD12-/- mice, a mouse model of the rare human genetic disorder PHARC (polyneuropathy, hearing loss, ataxia, retinosis pigmentosa, and cataract), and B6.Cg-Tg(GFAP- APOE_i4)1Hol Apoetm1Unc/J (apoE4) mice, a mouse model for Alzheimer's disease. Approximately 15% of humans harbor the apoE ε4 allele, but it is present in at least 40% of patients with late-onset AD; additionally individuals with one ε4 allele are three to four times more likely to develop AD and individuals with homozygous ε4 alleles have twelve times higher risk, an odds ratio much greater than that of other late-onset AD risk factors. PLA2G7 is directly associated with apoE, ideally positioning it to modulate metabolic changes, particularly as pertains to lipid oxidation, in apoE4 transgenic mice. In specific aim 3 we will determine the functional contribution of PLA2G7-regulated lipid pathways to neuroinflammation and neurodegeneration in ABHD12-/- and apoE4 mice. We anticipate that these studies will provide descriptive metabolic analyses and consequential functional outcomes of PLA2G7 inhibition or deletion with significant relevance to human conditions, including PHARC and Alzheimer's disease, the most prevalent neurodegenerative disorder. Identification of the metabolic function of PLA2G7 and correlating the metabolic changes imparted by PLA2G7 deletion or inhibition with therapeutic effects in ABHD12-/- and apoE4 mice will provide a greater understanding of PLA2G7 function and identify the basis for its therapeutic effects in human disease.