BIOCHEMICAL-GENETIC STUDIES OF TRANSFERRIN ENDOCYTOSIS

这项提议的目的是为了更好地理解分子 转铁蛋白介导的必需激素摄取的机制 以Fe(III)形式存在的矿物铁。血清糖蛋白--转铁蛋白 结合Fe(III)，是营养铁的主要载体 传送到细胞中。递送过程涉及受体介导的 转铁蛋白与细胞表面受体结合的内吞作用 内吞，释放结合的铁(III)，并被循环到细胞外结合 更多的Fe(III)。为了研究这一过程，我们正在分离和 在培养的细胞中鉴定缺失的突变体 转铁蛋白介导的铁摄取机制。对这一过程的研究是 与医疗保健的两个方面有关。一是提供基本的 关于内吞作用的信息。内吞过程是一个基本的 细胞吸收各种营养物质所需的活动 (除了铁)以及在对细胞外信号的响应中 控制一系列不同的活动，从生物合成途径 免疫反应的方方面面。而且，很多感染性物质，比如 作为某些病毒和细菌，利用内吞过程帮助发挥作用 它们的细胞病变效应。对内吞作用的更好理解可能会 提供可用于临床识别的新信息 以及与内吞过程有关的疾病的治疗。一个 该项目影响医疗保健的第二个领域是铁 毒性。有多种临床情况，如遗传性 血色素沉着症和输血引起的铁超载与 铁中毒。通过研究转铁蛋白介导的突变体铁摄取 可能会异常地积累铁，我们可能会了解到一些关于 铁超载的毒性效应表现在细胞水平上。至 分离突变株，我们将培养的细胞暴露在一种细胞毒性形式的 白喉毒素共价偶联转铁蛋白的研究 转铁蛋白。暴露在这种试剂下存活的细胞很可能是 转铁蛋白摄取途径有缺陷，我们确实发现 具有这种表型的突变体。今后的工作重点是分析 这些变种人。

The objective of this proposal is to better understand the molecular mechanisms involved in the transferrin-mediated uptake of the essential mineral iron in the form of Fe(III). Transferrin, a serum glycoprotein that binds Fe(III), is the major carrier by which nutrient iron is delivered to cells. The delivery process involves receptor mediated endocytosis whereby transferrin binds to cell surface receptors and is endocytosed, release bound Fe(III), and is recycled out of the cell to bind more Fe(III). To investigate this process we are isolating and characterizing mutants in cultured cells that are deficient in the transferrin-mediated iron uptake mechanism. Research into this process is related to two aspects of health care. The first is to provide basic information about endocytosis. The endocytic process is a fundamental activity of cells that is required in the uptake of a variety of nutrients (in addition to iron) and in responding to extracellular signals that control a diverse spectrum of activities ranging from biosynthetic pathways to aspects of the immune response. Moreover, many infectious agents, such as certain viruses and bacteria, use the endocytic process to help exert their cytopathic effects. A better understanding of endocytosis may provide new information that can be applied clinically to the recognition and treatment of disease conditions related to the endocytic process. A second area in which this project impacts health care concerns iron toxicitiy. There are a variety of clinical conditions, such as hereditary hemochromatosis and transfusion-induced iron overload, that are related to iron toxicity. By studying transferrin-mediated iron uptake by mutants that might aberrantly accumulate iron, we may learn something about how the toxic effects of iron overload are expressed at the cellular level. To isolate mutants, we expose cultured cells to a cytotoxic form of transferrin prepared by covalently coupling diptheria toxin to transferrin. Cells that survive exposure to this reagent are likely to be defective in the transferrin uptake pathway and we have indeed found mutants with this phenotype. Work in the future will focus on analyzing these mutants.