Hephaestin: A Copper Protein Involved in Iron Metabolism

描述（由申请人提供）：缺铁对世界上三分之一以上的人口产生不利影响。相反，铁超载疾病血色病是人类最常见的遗传缺陷之一。为了保持缺乏和毒性之间的平衡，存在多种调节系统来优化人体内的铁水平。肠道对铁的吸收是这种调节的核心，因为不存在排出过量铁的生理手段。我们的长期目标是了解身体如何将其铁需求传达给肠道，以及肠道如何控制铁吸收到体内。我们以前确定，hephaestin，它将铁从亚铁氧化为三价铁，并且是将铁从肠道细胞转移到体内所必需的。我们正在研究它在肠道铁转运和全身铁稳态中的功能和作用。铁缺乏时，铁转运蛋白的表达增加，一些蛋白质（包括hephaestin）从细胞内位置移动到细胞表面，以促进铁转运。在全身性铁缺乏症中，肠上皮细胞处于最大吸收的状态，但也能够在潜在毒性饮食水平的情况下缓冲铁的吸收。在这项研究中，我们将提出三个问题。1)如何调节hephaestin响应于局部和全身铁的状态？我们将独立地操纵小鼠的饮食和全身铁状态，以确定饮食对肝铁蛋白和其他铁转运蛋白的全身影响。我们将使用细胞培养研究来确定调节机制。2)是什么调节了hephaestin的运动？我们将定义运动的饮食条件和运动发生的速率。我们将使用细胞培养系统来识别运动所必需的部分。我们将试图确定在hephaestin的运动中发挥作用的蛋白质。最后，我们将问3）铁蛋白如何促进铁的运输？为了从铁转运蛋白中释放铁，可能直接需要赫菲斯汀，或者它可以产生亚铁的梯度，从而驱动铁的运输。使用缓冲系统的铁转运测定法使我们能够非常严格地控制亚铁和三价铁的量，这将使我们能够区分这些可能性。

DESCRIPTION (provided by applicant): Iron deficiency adversely affects over one-third of the world's population. Conversely, iron overload disease hemochromatosis is one of the commonest genetic defects in man. In order to maintain a balance between deficiency and toxicity, multiple regulatory systems exist to optimize iron levels in the human body. The absorption of iron by the intestine is central to this regulation because no physiologic means exists to excrete excess iron. Our long-term goal is to understand how changes the body communicates its iron needs to the intestine and how the intestine controls iron absorption into the body. We previously identified, hephaestin, which oxidizes iron from ferrous to ferric iron and is required for moving iron from gut cells into the body. We are studying its function and role in intestinal iron transport and whole body iron homeostasis. Remarkable changes occur in response to iron deficiency, the expression of iron transport proteins increase and some proteins including hephaestin move from intracellular locations to the cell surface to facilitate iron transport. In systemic iron deficiency, the intestinal enterocyte is poised for maximal absorption but is also capable of buffering the uptake of iron in case of potentially toxic dietary levels. In this study, we will ask three questions. 1) How is hephaestin regulated in response to local and systemic iron status? We will independently manipulate dietary and systemic iron status in mice to define the dietary versus systemic effects on hephaestin and other iron transport proteins. We will use cell culture studies to define the regulatory mechanisms. 2) What regulates the movement of hephaestin? We will define the dietary conditions for movement and the rate at which it occurs. We will use a cell culture system to identify the parts of hephaestin that are necessary for movement. We will try to identify the proteins that play a role in the movement of hephaestin. Finally, we will ask 3) how iron oxidation by hephaestin facilitates iron transport ? Hephaestin could be directly required in order to release iron from the iron transporter or alternatively it could create a gradient of ferrous iron which would drive the transport of iron. Iron transport assays using a buffer system that allows us to very tightly control the amount of ferrous and ferric iron will allow us to distinguish between these possibilities.