Integration of Hepatic Hepcidin and Intestinal HIF-2 alpha in Systemic Iron Metabolism

肝脏铁调素和肠道 HIF-2 α 在全身铁代谢中的整合

• 批准号: 9469643
• 负责人: Andrew Joseph Schwartz
• 金额: $ 3.56万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-30 至 2020-09-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9469643
• 关键词: Acute; Address; Affect; Alpha Cell; Apical; Autophagocytosis; Binding; Blood Circulation; CRISPR/Cas technology; Cell Line; Cells; Coupled; Data; Dietary Iron; Disease; Doxycycline; Erythropoiesis; Genetic; Goals; Heat-Shock Response; Hepatic; Homeostasis; Hormones; Human; Hypoxia Inducible Factor; Immunoprecipitation; Intestines; Iron; Iron Metabolism Disorders; Iron Overload; Knock-out; Laboratories; Liver; Lysosomes; Maintenance; Malnutrition; Mammals; Mass Spectrum Analysis; Mediating; Molecular; Molecular Chaperones; Morbidity - disease rate; Mutation; Organism; Pathway interactions; Process; Proteins; Regulation; Research; Research Proposals; Role; Signal Transduction; Site-Directed Mutagenesis; Stress; System; Tamoxifen; Technology; Testing; Tissues; Ubiquitination; absorption; bHLH-PAS factor HLF; base; hepcidin; insight; iron deficiency; iron metabolism; liver metabolism; metal transporting protein 1; mortality; mouse model; novel; overexpression; peptide hormone; sensor; therapeutic target; transcription factor; ubiquitin-protein ligase

Project Summary Over one billion people worldwide are affected by iron overload, iron deficiency, and states of malnutrition that perturb iron homeostasis. The master regulator of systemic iron metabolism is hepcidin, a hormone that is predominately synthesized and released by the liver. The function of hepcidin is to bind to the only mammalian iron exporter, ferroportin, resulting in ubiquitination, internalization, and degradation of ferroportin. Therefore, in the presence of hepcidin, small amounts of iron are mobilized from stores; in the absence of hepcidin, iron is rapidly mobilized into circulation. Mutations that disrupt the hepcidin/ferroportin signaling axis give rise to iron overload and iron deficiency in mammals, demonstrating that hepcidin and ferroportin are essential for the regulation of systemic iron homeostasis. Our lab has shown that the transcription factor, HIF-2, is a cellular iron sensor and is the master intestinal regulator of apical and basolateral iron transporters. Moreover, HIF-2 is essential for iron absorption following iron deficiency, the hyperabsorption of iron that leads to tissue iron accumulation during iron overload, and for efficient erythropoiesis. However, it is currently unknown whether the systemic iron regulator, hepcidin, and the intestinal iron regulator, HIF-2, integrate on the molecular level to maintain organism level iron homeostasis. Using a novel genetic mouse model that allows for tamoxifen-inducible deletion of hepatic hepcidin, our data shows that temporal loss of hepcidin increases intestinal HIF-2 activity and the expression of HIF-2-specific intestinal iron transporters. Ferroportin is the only known target of hepcidin. To further address this crosstalk, we have also begun to investigate the mechanism by which hepcidin initiates the internalization and degradation of ferroportin, which remains unknown. Our preliminary data shows that, once ubiquitinated and internalized, ferroportin is trafficked to the lysosome independent of canonical macroautophagic machinery. Using a cell based immunoprecipitation approach coupled to mass spectrometry, we identified and confirmed that heat shock 70 kDa protein 8 (HSC70) interacts with ferroportin. HSC70 is the rate limiting cargo protein involved in a process of selective lysosomal degradation that is discrete from macroautophagy, known as chaperone-mediated autophagy. This research proposal will test the hypothesis that rapid activation of intestinal HIF-2 by increased systemic iron demand is mediated by the hepcidin/ferroportin degradation axis in the intestine. This hypothesis will be tested through two interconnected specific aims: (1) Determine the requirement for ferroportin-mediated iron flux in intestinal HIF-2 regulation by hepcidin. (2) Characterize the molecular mechanisms of hepcidin-mediated ferroportin degradation. The proposed studies will unveil the mechanisms by which the liver and the intestine communicate to maintain systemic iron homeostasis, which is essential for the understanding and treatment of iron-related disorders.

项目摘要 全球超过10亿人受到铁超载，铁缺乏和营养不良状态的影响 那个扰动的铁稳态。系统性铁代谢的主要调节剂是肝素，是一匹马 主要由肝脏合成并释放。肝素的功能是结合到唯一的 哺乳动物铁出口商，铁蛋白，导致泛素化，内在化和降解 铁蛋白。因此，在肝素的存在下，少量的铁从商店中动员。在 铁皮素的缺乏，铁被迅速动员到循环中。破坏肝素/铁蛋白的突变 信号轴会导致哺乳动物的铁超负荷和铁缺乏，表明肝素和 铁蛋白对于调节全身铁稳态至关重要。我们的实验室表明 转录因子HIF-2是一种细胞铁传感器，是顶端的主肠调节剂 基底外侧铁转运蛋白。此外，HIF-2对于铁缺乏症后，施肥者至关重要 铁的超吸收，导致铁超载期间组织铁的积累，并为有效 红细胞生成。但是，目前尚不清楚系统性铁调节剂，肝素和 肠道调节剂HIF-2集成在分子水平上，以维持生物水平铁 稳态。使用新型的遗传小鼠模型，该模型允许他莫昔芬诱导的肝缺失 肝素，我们的数据表明，肝素的暂时损失会增加肠道HIF-2活性和 HIF-2特异性肠道铁转运蛋白的表达。铁蛋白是肝素唯一已知的靶标。 为了进一步解决此串扰，我们还开始研究肝素的机制 启动铁蛋白的内在化和降解，这仍然未知。我们的初步数据 表明，一旦泛素化和内在化，铁蛋白被贩运到独立于溶酶体 典型的宏观自载体机械。使用基于细胞的免疫沉淀方法耦合到质量 光谱法，我们确定并确认热休克70 kDa蛋白8（HSC70）与 铁蛋白。 HSC70是参与选择性溶酶体降解过程的限制货物蛋白的速率 这与大型噬菌体分离，称为伴侣介导的自噬。这项研究建议 将检验以下假设，即通过增加的全身铁需求而快速激活肠道HIF-2 由肠道中的肝素/铁蛋白降解轴介导。该假设将进行检验 通过两个相互联系的特定目的：（1）确定铁蛋白介导的铁通量的要求 肝素HEPCIDIN调节肠道HIF-2。 （2）表征肝素介导的分子机制 铁蛋白降解。拟议的研究将揭示肝脏和 肠道通信以维持全身铁稳态，这对于理解和 与铁相关疾病的治疗。