Role of Transferrin Receptor 2 in Iron Homeostasis

描述(申请人提供)：铁稳态失调是世界上最常见的营养问题之一。由于人类体内没有调节铁排泄的生理机制，体内平衡完全依赖于将饮食中铁的吸收与铁的利用和储存紧密联系起来。循环中的肝多肽海普西丁似乎是这一过程的中心调节因子。然而，肝细胞感知血浆铁和调节海普西丁表达的方式仍不清楚。与经典的Tf受体(TfR1)一样，最近发现的第二Tf受体(TfR2)介导细胞对holoTf的摄取。我们认为TfR2在肝细胞中的作用是作为肝细胞循环中HlooTf的感受器，以及铁调节多肽海普西丁的表达的调节器。这一假说得到了我们用无功能TfR2(TfR2 YaaSX纯合子小鼠)小鼠模型的观察支持。这项提议的广泛目标是定义和表征TfR2在铁稳态中的作用。我们有四个具体目标： 1)鉴定和鉴定TfR2在肝细胞摄取HoloTf中的作用。 2)明确TfR2在调节肝细胞表达海普西丁中的作用。 3)通过TfR2 v245x小鼠肝细胞中野生型TfR2的细胞特异性和可调控修复来区分TfR2在肝细胞中的作用。4)确定TfR2 M172K突变引起功能缺陷的分子基础。 这些研究将确定和表征TfR2作为肝细胞铁感受器的作用，以及它参与调节海普西丁的表达。这些知识将增加我们对铁稳态的理解，并可能提出新的方法来管理铁超载和分布不均的疾病。

DESCRIPTION (provided by applicant): Disorders of iron homeostasis are among the most common nutritional problems worldwide. Because there are no physiologic mechanisms to modulate iron excretion in humans, homeostasis depends entirely upon tightly linking dietary iron absorption with iron utilization and storage. The circulating liver peptide hepcidin appears to be a central regulator of this process. However, the means by which hepatocytes sense plasma iron and modulate hepcidin expression remain unknown. Like the classic Tf receptor (TfR1), the recently identified second Tf receptor (TfR2) mediates cellular uptake of holoTf. We propose that the role of TfR2 in the hepatoeyte is to serve as a hepatocellular sensor of circulating holoTf, and modulator of expression of the iron-regulatory peptide hepcidin. This hypothesis is supported by observations in our mouse model with a non-functional TfR2 (TfR2 YaaSX homozygous mice) It is the broad goal of this proposal to define and characterize the role of TfR2 in iron homeostasis. We have four specific aims: 1) Identify and characterize the participation of TfR2 in the hepatocellular uptake of holoTf. 2) Define the role of TfR2 in modulating the hepatocellular expression of hepcidin. 3) Distinguish the hepatocellular role of TfR2 by the cell-specific and regulatable restoration of wild-type TfR2 in TfR2 v245x mouse hepatocytes. 4) Determine the molecular basis for the functional defect caused by the TfR2 M172K mutation. These studies will identify and characterize the role of TfR2 as a hepatocellular iron sensor, and its participation in the modulation of hepcidin expression. This knowledge will increase our understanding of iron homeostasis, and may suggest new approaches to the management of diseases of iron overload and maldistribution.