Zip Proteins and Iron Metabolism

项目总结/摘要 铁超负荷紊乱遗传性血色病是一种内分泌性肝病， 产生足够量的铁调素，一种由肝脏产生的铁调节激素。在 在血色素沉着症中，膳食铁的吸收增加导致血浆非转铁蛋白结合的出现， 铁（NTBI），其被各种组织和细胞摄取，导致组织铁过载和相关病理学。 血浆NTBI也常见于血液病重型地中海贫血，一种遗传性血液疾病 这需要定期输血，随着时间的推移会导致铁超载。虽然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 不完整这项提案的主要长期目标是确定将铁转运到体内的蛋白质。 各种组织和细胞，特别是受铁过载相关病理影响的那些。我们的核心假设 膜转运蛋白ZIP 14和ZIP 8参与铁稳态和NTBI摄取。在 在上一个资助期，我们发现ZIP 14是肝细胞中主要的NTBI摄取机制， 胰腺腺泡细胞，并且ZIP 14是铁负荷的小鼠模型中的肝脏和胰腺所需的。 血色素沉着症和膳食铁过量。我们还产生了多种条件性Zip 8基因敲除小鼠 模型来询问ZIP 8在铁代谢和铁过载中的作用。在拟议研究的目标1中， 我们将继续使用ZIP 14基因敲除（Zip 14-/-）小鼠来确定ZIP 14在组织铁负荷中的作用 与青少年血色素沉着症模型hemojuvelin敲除（HIBE-/-）小鼠杂交。当前焦点 会对内分泌器官包括脑下垂体和肾上腺产生影响。使用Hymphocyte-/-小鼠，我们将 还评估了降低ZIP 14表达（内源性或遗传性）与铁结合的功效 缓解组织铁过载的螯合作用。在目标2中，我们将确定ZIP 14介导的铁负载如何影响细胞的铁负载。 胰腺β细胞导致β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细胞中特异性过表达ZIP 14的模型。当负载铁时，ZIP 14转基因小鼠， 类似于铁负荷的人类，在β细胞中积累铁并发展成糖尿病。我们将描述 这些小鼠糖尿病的发展，重点是β细胞发生的变化。目标3：我们将继续 确定ZIP 8在铁稳态中的作用，特别是其在应激红细胞生成中的明显作用。以限定 ZIP 8在组织铁负荷中的作用，我们将利用诱导型Zip 8-/-小鼠以及Zip 8-/-; Zip 14-/-双 敲除小鼠，这将有助于确定这两种同源蛋白质是否可以相互补偿 其他.

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.