Functional annotation of the oxidized lipid hydrolase PLA2G7 in neurodegeneration

 描述(申请人提供)：PLA2G7基因编码一个50 kDa的分泌型丝氨酸水解酶。对PLA2G7的大部分关注都集中在它作为心血管疾病标志物的潜力上；然而，PLA2G7在哺乳动物的整个有机体中都有表达，包括大脑。抑制PLA2G7已显示出对人类阿尔茨海默病患者的治疗效果，但该酶在体内的功能尚不清楚。我们的实验室已经开发了一套工具来研究PLA2G7在小鼠脑中的作用，包括PLA2G7-/-小鼠，选择性的PLA2G7的中枢活性抑制剂，以及靶点参与试验，以确认抑制剂在体内的作用。利用这些化学和遗传工具，结合基于质谱学的脂体学和蛋白质组学研究，我们建议通过纵向研究来确定PLA2G7在中枢神经系统中的代谢功能，并确定它在两种神经退行性变小鼠模型中的作用。在具体目标1中，我们将使用PLA2G7-/-小鼠和选择性PLA2G7抑制剂JMN21绘制PLA2G7干扰小鼠大脑中随年龄变化的血脂变化图。这些研究将利用非靶向和靶向液质联用来识别和量化依赖于PLA2G7的大脑代谢物的变化。在特定目标2中，我们将在两个神经炎症和神经退化的动物模型中识别PLA2G7依赖的脂质变化：ABHD12-/-小鼠，罕见的人类遗传性疾病PHARC(多发性神经病、听力损失、共济失调、视网膜色素沉着和白内障)的小鼠模型，以及B6.Cg-TG(GFAP-APOE_I4)1Hol Apoetm1Unc/J(ApoE4)小鼠，阿尔茨海默病的小鼠模型。大约15%的人携带载脂蛋白Eε4等位基因，但至少有40%的晚发性AD患者存在载脂蛋白E 4等位基因；此外，具有一个ε4等位基因的人患AD的可能性是其他人的3-4倍，ε4纯合等位基因的人患AD的风险是其他晚发性AD风险因素的12倍，优势比远远大于其他晚发性AD风险因素。PLA2G7与apoE直接相关，理想地将其定位于调节代谢变化，特别是与apoE4转基因小鼠的脂肪氧化有关的代谢变化。在具体目标3中，我们将确定PLA2G7调节的脂质通路在ABHD12-/-和apoE4小鼠神经炎症和神经变性中的功能贡献。我们预计，这些研究将提供描述性的代谢分析和PLA2G7抑制或缺失的相应功能结果，与人类状况显著相关，包括PHARC和阿尔茨海默病，这是最常见的神经退行性疾病。在ABHD12-/-和apoE4小鼠中，鉴定PLA2G7的代谢功能，并将PLA2G7缺失或抑制所带来的代谢变化与治疗效果相关联，将有助于更好地了解PLA2G7的功能，并为其在人类疾病中的治疗作用奠定基础。

 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.