Megalin, mitochondrial intracrine signaling and the kidney

线粒体功能障碍和活性氧（ROS）在疾病过程中起关键作用， 缺血性阿基，免疫应答和炎症，糖尿病，肥胖症，代谢综合征，衰老， 神经变性和心血管疾病。因此，阐明线粒体的机制， 功能障碍是理解许多疾病过程的病理生理学的关键。使用 缺血/再灌注（I/R）肾损伤模型来表征用于肾保护的线粒体途径，我们 确定斯钙素-1（STC 1）为潜在的治疗靶点。STC 1是线粒体内分泌分子 （定义为一种细胞外信号分子，进入细胞，易位到线粒体并改变其功能。 功能）。STC 1激活AMPK，AMPK反过来上调解偶联蛋白（UCP）和SIRT 3，促进 线粒体抗氧化防御。STC 1的转基因过表达赋予对IR肾损伤的抗性。 内分泌物如STC 1易位到线粒体的机制尚不清楚。我们有 鉴定了多配体受体巨蛋白作为STC 1从细胞表面到线粒体的运输载体 通过逆行的早期内体到高尔基体。培养细胞中的巨蛋白KO降低SIRT 3的表达， 减少线粒体呼吸和糖酵解，并增加对缺血性肾损伤的易感性。这 一项提案将检验以下假设：megalin对线粒体生物学至关重要; megalin的KO使线粒体中的 缺血性肾损伤; STC 1介导的细胞保护需要STC 1的线粒体靶向。目的 图1A将确定具有多西环素诱导的和多柔比星诱导的小鼠中缺血/再灌注肾损伤的表型。 肾小管上皮特异性敲除巨蛋白。目的1B将描述培养的 在基线和缺氧/复氧后，具有巨蛋白KO的近端小管细胞。目标2A将决定 STC 1介导的体外细胞保护是否需要STC 1的线粒体靶向。目标2B将 确定STC 1介导的体内细胞保护是否需要STC 1的线粒体靶向。我们 拟议的研究将阐明megalin和STC 1在线粒体功能中的作用，并可能提供基本的 深入了解线粒体功能障碍至关重要的疾病的发病机制。

Mitochondrial dysfunction and reactive oxygen species (ROS) play critical roles in disease processes from ischemic AKI, to immune response and inflammation, diabetes, obesity, metabolic syndrome, aging, neurodegenerative and cardiovascular diseases. Therefore, elucidating mechanisms of mitochondrial dysfunction is key to understanding the pathophysiology of many disease processes. Using the ischemia/reperfusion (I/R) kidney injury model to characterize mitochondrial pathways for kidney protection, we identified stanniocalcin-1 (STC1) as a potential therapeutic target. STC1 is a mitochondrial intracrine molecule (defined as an extracellular signaling molecule that enters cells, translocates to mitochondria and alters their function). STC1 activates AMPK, which in turn upregulates uncoupling proteins (UCPs) and SIRT3, promoting mitochondrial anti-oxidant defenses. Transgenic overexpression of STC1 confers resistance to IR kidney injury. The mechanism whereby intracrines such as STC1 are translocated to mitochondria is unknown. We have identified the multi-ligand receptor megalin as a trafficking vehicle for STC1 from the cell surface to mitochondria via the retrograde early endosome-to-Golgi. Megalin KO in cultured cells decreases the expression of SIRT3, diminishes mitochondrial respiration and glycolysis, and increases susceptibility to ischemic kidney injury. This proposal will examine the hypotheses that: megalin is critical for mitochondrial biology; KO of megalin aggravates ischemic kidney injury; and mitochondrial targeting of STC1 is required for STC1-mediated cytoprotection. Aim 1A will determine the phenotype of ischemia/reperfusion kidney injury in mice with doxycycline-inducible and tubular epithelium-specific knockout of megalin. Aim 1B will characterize the mitochondrial phenotype in cultured proximal tubule cells with megalin KO, at baseline and following hypoxia/reoxygenation. Aim 2A will determine whether mitochondrial targeting of STC1 is required for STC1-mediated cytoprotection in vitro. Aim 2B will determine whether mitochondrial targeting of STC1 is required for STC1-mediated cytoprotection in vivo. Our proposed studies will elucidate the role of megalin and STC1 in mitochondrial function and may offer fundamental insights into the pathogenesis of diseases where mitochondrial dysfunction is critical.