Regulation of PPAR alpha by PACS-2 in response to nutrient stress

项目摘要 肥胖症的流行正在加速糖尿病、非酒精性脂肪肝（NAFLD）、心血管疾病和糖尿病的风险。 血管疾病和其他疾病。PPARa激动剂药物被开处方以促进脂肪损失和改善。 通过激活驱动线粒体B-氧化的基因程序来评估肝脂肪变性和胰岛素抵抗。 PPARa激动剂在肝脏中的作用通过重塑MAMs的作用而增强， 促进钙离子和磷脂在胞浆和内质网之间交换的结构， lum。主mT 0 RC 2/Akt信令节点定位到MAM，其中它协调PPARa和MAM 通过一种未知的机制。因此，了解mTORC 2/Akt如何调节PPARa 肝脏中的MAMs对于开发对抗肥胖流行病的新方法至关重要。我们长久以来- 长期目标是了解细胞核基因表达和细胞质ER/线粒体活性是如何协调的， 用来控制人体能量平衡本申请的目的是确定 mTORC 2/Akt介导的多功能蛋白PACS-2 Ser 437磷酸化如何与 PACS-2核运输信号以协调PPARa转录活性与MAM依赖性卡尔奇调蛋白 嗯，对禁食或高脂肪饮食的反应交换。我们的核心假设是，在对暴饮暴食的反应中- 因此，mTORC 2/Akt磷酸化的PACS-2在细胞质中螯合PPARa并增加MAMs， 通过抑制控制脂肪酸氧化的基因，同时诱导线粒体中的钙超载。这些 联合作用导致脂肪变性和胰岛素抵抗。相比之下，禁食沉默mTORC 2/Akt信号- 从而触发PACS-2去磷酸化。因此，PPARa被释放，MAMs被重塑， 其联合收割机增加脂肪酸氧化并支持禁食诱导的自噬。以强为导 初步数据，我们将通过追求三个具体目标来测试我们的假设：1）确定肝脏PACS- 2协调PPARa依赖性基因表达与MAM重塑以调节脂肪酸氧化; 2） 确定mTOR/Akt如何控制PACS-2对PGC-1a/PPARa活性的调节;以及3）确定mTOR/Akt如何控制PACS-2对PGC-1a/PPARa活性的调节。 PACS-2调节PPARa进入细胞核。这种方法是创新的，因为它将联合收割机与 营养过剩和禁食的体内模型以及基因表达，ER-线粒体通讯， nication，线粒体耗氧量和活细胞成像，以描述一种新的和以前未报道的， 控制对禁食或高脂饮食的反应的已知途径。这项研究意义重大，因为 这将进一步加深我们对mTORC 2/Akt如何控制PACS-2 Ser 437作为分子开关的理解 协调重要的，稳态转录和线粒体响应营养压力。

PROJECT SUMMARY The obesity pandemic is accelerating the risk of diabetes, non-alcoholic fatty liver disease (NAFLD), cardio- vascular diseases and other ailments. PPARa agonist drugs are prescribed to promote fat loss and amelio- rate hepatic steatosis and insulin resistance by activating gene programs driving mitochondrial b-oxidation. Effects of PPARa agonists in the liver are enhanced by remodeling the action of MAMs, cytoplasmic struc- tures that foster exchange of Ca2+ and phospholipids between the mitochondrion and endoplasmic reticu- lum. The master mTORC2/Akt signaling node localizes to the MAM where it coordinates PPARa and MAM actions through an unknown mechanism. Therefore, understanding how mTORC2/Akt regulates PPARa and MAMs in the liver is crucial to developing new approaches to combat the obesity epidemic. Our long- term goal is to understand how nuclear gene expression and cytoplasmic ER/mitochondrial activity are coor- dinated to control energy homeostasis in humans. The objective of this particular application is to determine how mTORC2/Akt-mediated phosphorylation of the multi-functional protein PACS-2 Ser437 combines with PACS-2 nuclear trafficking signals to coordinate PPARa transcriptional activity with MAM-dependent calci- um exchange in response to fasting or a high fat diet. Our central hypothesis is that in response to overeat- ing, mTORC2/Akt-phosphorylated PACS-2 sequesters PPARa in the cytoplasm and increases MAMs, there- by repressing genes controlling fatty acid oxidation while inducing calcium overload in mitochondria. These combined effects cause steatosis and insulin resistance. By contrast, fasting silences mTORC2/Akt signal- ing, triggering PACS-2 dephosphorylation. Consequently, PPARa is liberated and MAMs are remodeled, which combine to increase fatty acid oxidation and support fasting-induced autophagy. Guided by strong preliminary data, we will test our hypothesis by pursuing three specific aims: 1) Determine how liver PACS- 2 coordinates PPARa-dependent gene expression with MAM remodeling to regulate fatty acid oxidation; 2) Determine how mTOR/Akt controls PACS-2 regulation of PGC-1a/PPARa activity; and 3) Determine how PACS-2 regulates access of PPARa to the nucleus. The approach is innovative because it will combine in vivo models of overnutrition and fasting together with studies on gene expression, ER-mitochondria commu- nication, mitochondrial oxygen consumption and live-cell imaging to describe a novel and previously unrec- ognized pathway controlling the response to fasting or a high fat diet. This research is significant because it will advance our understanding of how mTORC2/Akt controls PACS-2 Ser437 to act as a molecular switch to coordinate vital, homeostatic transcriptional and mitochondrial responses to nutrient stresses.