Megalin, mitochondrial intracrine signaling and the kidney

线粒体功能障碍和活性氧物种(ROS)在以下疾病过程中发挥关键作用 缺血性AKI，免疫反应和炎症，糖尿病，肥胖，代谢综合征，衰老， 神经退行性疾病和心血管疾病。因此，阐明线粒体的作用机制 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)肾损伤模型研究线粒体途径对肾脏的保护作用 确定了锡钙素-1(STC1)作为潜在的治疗靶点。STc1是一种线粒体内分泌分子 (定义为一种细胞外信号分子，它进入细胞，移位到线粒体，并改变其 功能)。STC1激活AMPK，进而上调解偶联蛋白(UCPs)和SIRT3，促进 线粒体的抗氧化防御系统。转基因过表达STC1可抵抗IR肾损伤。 像STC1这样的内切酶被转移到线粒体的机制尚不清楚。我们有 发现多配体受体巨蛋白是STC1从细胞表面到线粒体的运输工具 通过逆行的早期内胚体到高尔基体。培养细胞中的巨蛋白KO降低SIRT3的表达， 减少线粒体呼吸和糖酵解，增加对缺血性肾损伤的易感性。这 该提案将检验以下假设：巨蛋白对线粒体生物学至关重要；超蛋白的KO加剧 缺血肾损伤；而线粒体靶向STC1是STC1介导的细胞保护所必需的。目标 1A将确定多西环素诱导的小鼠缺血/再灌流肾损伤的表型和 肾小管上皮细胞特异性敲除巨蛋白。目的1B将表征培养的线粒体的表型 近端小管细胞，在基线和缺氧/复氧后加入megalin KO。目标2A将确定 在体外是否需要线粒体靶向STC1来实现STC1介导的细胞保护。目标2B将 确定在体内是否需要线粒体靶向STC1来实现STC1介导的细胞保护。我们的 拟议的研究将阐明megalin和stc1在线粒体功能中的作用，并可能为 对线粒体功能障碍至关重要的疾病的发病机制的洞察。

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.