Mechanism and regulation of iron export by ferroportin

铁转运蛋白对铁输出的机制和调控

• 批准号: 8144339
• 负责人: JERRY KAPLAN
• 金额: $ 30.71万
• 依托单位: UNIVERSITY OF UTAH
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-05-15 至 2015-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8144339
• 关键词: Address; Affect; Amino Acids; Anemia; Anti-Bacterial Agents; Behavior; Beryllium; Binding; Binding Proteins; Binding Sites; Biochemical; Cell physiology; Cell surface; Cells; Complex; Data; Diagnosis; Disease; Down-Regulation; Event; Genes; Genetic; Heat shock proteins; Homeostasis; Hormones; Inherited; Injury; Iron; Iron Overload; Laboratories; Lead; Mediating; Missense Mutation; Molecular; Molecular Conformation; Multivesicular Body; Mus; Mutation; Organ; Organism; Peptides; Phenotype; Phosphorylation; Physiology; Plasma; Property; Protein Kinase; Proteins; Regulation; Role; Serum; Starvation; Structure; Temperature; Testing; Tissues; Ubiquitin; Ubiquitination; base; deprivation; dimer; hepcidin; human disease; iron metabolism; metal transporting protein 1; monomer; mutant; peptide hormone; public health relevance; response; trafficking; ubiquitin ligase; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): Iron is both essential and toxic. Malregulation of iron metabolism resulting in decreased iron acquisition leads to anemia, while excessive iron accumulation leads to iron overload disease. Ferroportin (Fpn) is the only known iron exporter and understanding the regulation of Fpn is essential to understanding iron homeostasis. Fpn functions as a homodimer and missense mutations in Fpn result in a dominantly inherited iron-overload disease. We will identify domains in Fpn important for dimer formation and for the proper trafficking of Fpn to the cell surface. Systemic iron physiology is regulated by the binding of the peptide hormone hepcidin to Fpn leading to Fpn internalization and degradation. We previously identified the hepcidin-binding domain on Fpn. We will determine which amino acids in hepcidin are important for hepcidin conformation and Fpn binding. We will resolve the structure of hepcidin bound to the hepcidin-binding domain on Fpn by NMR. We determined that hepcidin induces the binding of Jak2 to Fpn. We will determine the binding site on Fpn for Jak2 and how Fpn monomers interact to permit Jak2 binding and activation. We will also determine how hepcidin induces the binding of hsp70 to Fpn and the role of hsp70 in Fpn internalization. We discovered that cellular iron deprivation leads to hepcidin-independent internalization of Fpn that is dependent on ubiquitination of Fpn. We determined that Nedd4-2 is the ubiquitin ligase responsible for hepcidin-independent internalization of Fpn, as well the ubiquitin ligase responsible for hepcidin-dependent internalized Fpn entry into the multivesicular body. Our data suggests that Nedd4-2 does not bind to Fpn directly. We will identify the proteins that mediate the effects of Nedd4-2 on Fpn. We will test the hypothesis that hepcidin- independent ubiquitination is a response to altered Fpn conformation. Using mice that have a FLOXED Nedd4-2, we will determine the role of iron starvation-induced Fpn degradation in cell and organ physiology. These studies will define the regulation of Fpn in normal and disease states and provide new opportunities for the treatment of both iron-overload disorders and anemia due to increased serum hepcidin. PUBLIC HEALTH RELEVANCE: Iron is an essential element but is toxic in excess. Malregulation of iron transport results in tissue injury, either from iron deprivation or overload. We will characterize iron transport through ferroportin, the only known mammalian iron exporter. We will determine the domains in ferroportin important for dimer formation and iron transport. We will determine how the hormone hepcidin regulates ferroportin internalization and the mechanism of hepcidin-independent ferroportin internalization. Our studies will provide information on how alterations in ferroportin result in disease and create new opportunities to manage and diagnose human diseases due to altered iron metabolism.

描述（由申请人提供）：铁既是必需的，也是有毒的。铁代谢失调导致铁获取减少导致贫血，而铁积累过多则导致铁超载疾病。铁转运蛋白 (Fpn) 是唯一已知的铁输出蛋白，了解 Fp​​n 的调节对于了解铁稳态至关重要。 Fpn 作为同二聚体起作用，Fpn 的错义突变导致显性遗传性铁超载疾病。我们将确定 Fpn 中对于二聚体形成和 Fpn 正确运输到细胞表面至关重要的结构域。全身铁生理学通过肽激素铁调素与 Fpn 的结合来调节，导致 Fpn 内化和降解。我们之前在 Fpn 上鉴定了铁调素结合域。我们将确定铁调素中的哪些氨基酸对于铁调素构象和 Fpn 结合很重要。我们将通过 NMR 解析与 Fpn 上的铁调素结合域结合的铁调素的结构。我们确定铁调素诱导 Jak2 与 Fpn 的结合。我们将确定 Fpn 上 Jak2 的结合位点以及 Fpn 单体如何相互作用以允许 Jak2 结合和激活。我们还将确定铁调素如何诱导 hsp70 与 Fpn 的结合以及 hsp70 在 Fpn 内化中的作用。我们发现细胞缺铁会导致 Fpn 不依赖铁调素的内化，而 Fpn 的内化依赖于 Fpn 的泛素化。我们确定 Nedd4-2 是负责 Fpn 不依赖铁调素内化的泛素连接酶，也是负责铁调素依赖性内化 Fpn 进入多泡体的泛素连接酶。我们的数据表明 Nedd4-2 不直接与 Fpn 结合。我们将鉴定介导 Nedd4-2 对 Fpn 影响的蛋白质。我们将检验以下假设：不依赖铁调素的泛素化是对 Fpn 构象改变的反应。使用具有 FLOXED Nedd4-2 的小鼠，我们将确定铁饥饿诱导的 Fpn 降解在细胞和器官生理学中的作用。这些研究将明确 Fpn 在正常和疾病状态下的调节，并为治疗铁过载疾病和血清铁调素增加引起的贫血提供新的机会。 公众健康相关性：铁是一种必需元素，但过量会产生毒性。铁转运的失调会导致组织损伤，无论是铁缺乏还是铁过载。我们将描述通过铁转运蛋白（唯一已知的哺乳动物铁输出蛋白）的铁转运。我们将确定铁转运蛋白中对二聚体形成和铁转运重要的结构域。我们将确定激素铁调素如何调节铁转运蛋白内化以及铁调素独立的铁转运蛋白内化机制。我们的研究将提供有关铁转运蛋白的改变如何导致疾病的信息，并为管理和诊断因铁代谢改变而导致的人类疾病创造新的机会。