Novel roles of copper in adaptive responses to hypoxia

铜（Cu）是人体必需的营养物质，在氧的运输和利用中起着至关重要的作用。铜通过氧化磷酸化直接作用于氧的消耗，并且是铁的运输所必需的，铁对于血红蛋白内的氧运输至关重要。尽管铜在氧代谢中的重要性，但关于氧水平降低（缺氧）对铜稳态的影响知之甚少。缺氧是一种生理应激，与许多常见疾病的病理有关，因此细胞对缺氧的感知和反应机制对人类健康具有重要意义。利用基于crispr的新型铜稳态调控基因敲除筛选，研究人员发现von Hippel Lindau （VHL）基因突变可刺激ATP7B的表达，ATP7B是一种主要在肝细胞中表达的铜转运蛋白。VHL是氧感应的主要调节因子，我们证明在培养细胞和小鼠肝脏中，缺氧会强烈诱导ATP7B的表达。ATP7B对于将铜插入铜蓝蛋白至关重要，铜蓝蛋白是一种氧化铁酶，已知在铁输出到血浆中起作用。在本提案中，我们将通过ATP7B促进铜蓝质蛋白介导的铁输出到血浆的能力来验证缺氧诱导的红细胞生成所需要的假说。已知ATP7B基因的突变会导致威尔森氏病，这是一种致命的肝铜超载疾病。我们证明，缺氧诱导另一种铜转运体ATP7A的肝脏表达，ATP7A是ATP7B的功能同源物。在本提案中，我们将在威尔逊病的ATP7B-/-小鼠模型中验证缺氧诱导的ATP7A可以减轻肝铜超载和肝脏病理的假设。为了增加我们研究的转化潜力，临床批准的模拟缺氧药物Roxadustat的治疗效果也将在ATP7B-/-小鼠中进行测试，以确定其作为威尔逊氏病新疗法的潜力。最后，基于我们的基因敲除筛选的成功，我们将对铜稳态的新调节因子进行创新的基于CRISPR的基因激活筛选。为了验证这些假设，我们的建议将1)研究铜在缺氧适应性反应中的作用；2)在Wilson病动物模型中测试缺氧的治疗潜力，3)使用创新的基因激活筛选确定哺乳动物铜稳态的新成分。

Copper (Cu) is an essential nutrient that plays vital roles in oxygen transport and utilization. Copper functions directly in the consumption of oxygen via oxidative phosphorylation and is required for the transport of iron which is a vital for oxygen transport within hemoglobin. Despite the importance of copper in oxygen metabolism, little is known regarding the effects of reduced oxygen levels (hypoxia) on copper homeostasis. Hypoxia is a physiological stress that contributes to the pathology of many common diseases, thus the mechanisms by which cells sense and respond to hypoxia is of fundamental importance to human health. Using an innovative CRISPR-based knockout screen for novel regulators of copper homeostasis, mutations in the von Hippel Lindau (VHL) gene were found to stimulate the expression of ATP7B, a copper transporter primarily expressed in hepatocytes. VHL is a master regulator of oxygen sensing and we demonstrate that ATP7B expression is strongly induced by hypoxia in cultured cells and in the liver of mice. ATP7B is essential for inserting copper into the ceruloplasmin, a ferroxidase with known roles in iron export into the plasma. In this proposal, we will test the hypothesis that ATP7B is required for hypoxia-induced erythropoiesis through its ability to facilitate ceruloplasmin-mediated iron export into the plasma. Mutations in the ATP7B gene are known to cause Wilson disease, a lethal disorder of hepatic copper overload. We demonstrate that hypoxia induces hepatic expression of an alternative copper transporter, ATP7A, which is a functional homologue of ATP7B. In this proposal, we will test the hypothesis that hypoxia-induced ATP7A can attenuate hepatic copper overload and liver pathology in the ATP7B-/- mouse model of Wilson disease. To increase the translational potential of our studies, the therapeutic efficacy of a clinically approved hypoxia-mimetic drug Roxadustat will also be tested in ATP7B-/- mice to address its potential for repurposing as a novel treatment for Wilson disease. Finally, based on the demonstrated success of our knockout screen, we will perform an innovative CRISPR- based gene activation screen for novel regulators of copper homeostasis. To test these hypotheses, our proposal will 1) investigate the roles of copper in adaptive responses to hypoxia; 2) test the therapeutic potential of hypoxia in animal models of Wilson disease and 3) identify novel components of mammalian copper homeostasis using an innovative gene activation screen.