Zip Proteins and Iron Metabolism

项目摘要/摘要 铁超载障碍遗传性血色沉着症是一种内分泌性肝病，是由于缺乏能力而导致的 产生足够量的海普西丁，这是一种由肝脏产生的铁调节激素。在……里面 血色沉着症，膳食铁吸收增加导致血浆非转铁蛋白结合的出现 铁(NTBI)，它被各种组织和细胞摄取，导致组织铁超载和相关的病理。 血浆NTBI也常见于遗传性血液疾病--地中海贫血。 这需要定期输血，随着时间的推移，这会导致铁超载。尽管NTBI是主要的 作为组织铁负荷的贡献者，我们对介导NTBI摄取的分子机制的理解是 不完整。这项提议的主要长期目标是确定将铁运输到 各种组织和细胞，特别是那些受铁超载相关病理影响的组织和细胞。我们的中心假设 膜转运蛋白ZIP14和ZIP8参与铁的稳态和NTBI的摄取。在 上一期我们发现ZIP14是肝细胞摄取NTBI的主要机制， 胰腺腺泡细胞，ZIP14是小鼠肝脏和胰腺铁负荷所必需的。 血色沉着症和膳食铁超载。我们还产生了各种条件ZIP8基因敲除小鼠 模型询问ZIP8在铁代谢和铁超载中的作用。在拟议研究的目标1中， 我们将继续通过ZIP14基因敲除(Zip14-/-)小鼠来确定ZIP14在组织铁负荷中的作用 与血红蛋白基因敲除(Hjv-/-)小鼠杂交，建立幼年血色素沉着症模型。当前的焦点 会出现在内分泌器官上，包括脑下垂体前叶和肾上腺。使用Hjv-/-小鼠，我们将 同时评估与铁结合降低ZIP14表达(药理学或遗传学)的效果 螯合在减轻组织铁负荷中的作用。在目标2中，我们将确定ZIP14介导的铁负荷是如何 胰岛β细胞会导致胰岛细胞功能障碍和糖尿病。为此，我们培育了一只转基因小鼠。 在β细胞中特异过度表达ZIP14的模型。当携带铁时，ZIP14转基因小鼠， 与富含铁的人类相似，它会在β细胞中积聚铁，从而患上糖尿病。我们将描述 糖尿病在这些小鼠中的发展，重点是β细胞中发生的变化。在目标3中，我们将继续 明确ZIP8在铁稳态中的作用，特别是其在应激性红细胞生成中的明显作用。要定义 ZIP8在组织铁负荷中的作用，我们将利用可诱导的ZIP8-/-小鼠以及ZIP8-/-；Zip14-/-Double 这将有助于确定这两个同源蛋白是否可以相互补偿 其他的。

PROJECT SUMMARY/ABSTRACT The iron overload disorder hereditary hemochromatosis is an endocrine liver disease that results from an inability to produce sufficient amounts of hepcidin, the iron-regulatory hormone produced by the liver. In hemochromatosis, increased absorption of dietary iron leads to the appearance of plasma non-transferrin-bound iron (NTBI), which is taken up by various tissues and cells leading to tissue iron overload and related pathology. Plasma NTBI is also commonly seen in the hematologic disease thalassemia major, an inherited blood disorder that requires regular blood transfusions, which over time result in iron overload. Although NTBI is the major contributor to tissue iron loading, our understanding of the molecular mechanisms that mediate NTBI uptake is incomplete. The primary long-term objective of this proposal is to define the proteins that transport iron into various tissues and cells, particularly those affected by iron-overload related pathology. Our central hypothesis is that the membrane transport proteins ZIP14 and ZIP8 participate in iron homeostasis and NTBI uptake. In the previous funding period we found that ZIP14 is the primary NTBI uptake mechanism in hepatocytes and pancreatic acinar cells, and that ZIP14 is required for iron loading of the liver and pancreas in mouse models of hemochromatosis and dietary iron overload. We also generated a variety of conditional Zip8 knockout mouse models to interrogate the roles of ZIP8 in iron metabolism and iron overload. In Aim 1 of the proposed research, we will continue to define the roles of ZIP14 in tissue iron loading by using ZIP14 knockout (Zip14-/-) mice intercrossed with hemojuvelin knockout (Hjv-/-) mice, a model of juvenile hemochromatosis. The current focus will be on endocrine organs including the anterior pituitary gland and adrenal gland. Using Hjv-/- mice, we will also assess the efficacy of reducing ZIP14 expression (pharmacologically or genetically) combined with iron chelation in mitigating tissue iron overload. In Aim 2, we will determine how ZIP14-mediated iron loading of pancreatic beta cells leads to beta cell dysfunction and diabetes. For this aim we generated a transgenic mouse model that overexpresses ZIP14 specifically in beta cells. When loaded with iron, the ZIP14 transgenic mice, similar to iron-loaded humans, accumulate iron in beta cells and develop diabetes. We will characterize the development of diabetes in these mice, focusing on changes that occur in beta cells. In Aim 3, we will continue to define the roles of ZIP8 in iron homeostasis, particularly its apparent role in stress erythropoiesis. To define the roles of ZIP8 in tissue iron loading, we will utilize inducible Zip8-/- mice as well as Zip8-/-;Zip14-/- double knockout mice, which will help to determine whether these two homologous proteins can compensate for each other.