Erythroid transporter function in hemoglobin synthesis

红细胞转运蛋白在血红蛋白合成中的功能

基本信息

批准号：
6558665
负责人：
Orian S Shirihai
金额：
$ 31万
依托单位：
MARINE BIOLOGICAL LABORATORY
依托单位国家：
美国
项目类别：
财政年份：
2002
资助国家：
美国
起止时间：
2002-12-03 至 2003-11-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): A number of disorders due to abnormalities in heme biosynthesis influence erythropoiesis. During normal erythroid maturation, heme precursors are generated in the mitochondria, modified in the cytosol and then returned to the mitochondria for final assembly with iron. Remarkably, accumulation of toxic heme intermediates or substrates, and secondary mitochondrial damage, are key elements in the pathophysiology of all heme biosynthesis disorders. However, the mechanisms of export or import of heme products, by-products and intermediates to or from the mitochondrial matrix are as yet poorly understood. This proposal will focus on such mechanisms taking advantage of our discovery of ABC-me, a novel mitochondrial erythroid transporter. ABC-me expression is controlled by the erythroid transcription factor GATA-1 and is down regulated by heme. In differentiating erythroleukemic cells, ABC-me is rate limiting for heme biosynthesis. As such, ABC-me is the only mitochondrial inner membrane transporter implicated in heme biosynthesis. To explore its function in heme biosynthesis, we have developed ABC-me deficient cell culture models and functional assays of reconstituted transporter in proteoliposomes. We have established that differentiating erythroid cells with reduced ABC-me activity produce less heme and exhibit signs of mitochondrial stress. We postulate that transporters involved in the heme pathway serve as gatekeepers for reactive substrates, intermediates and byproducts and thus couple production of essential end products to protection from toxic intermediates. We propose a combined biochemical and biophysical approach to the study of the function of ABC-me in heme biosynthesis and the consequences of its malfunction. We will address the following questions: 1) Which steps in the heme biosynthetic pathway are facilitated by ABC-me? 2) Does ABC-me deficiency result in the accumulation of heme precursors in the cytosol and mitochondria? 3) What is the source of mitochondrial stress associated with ABC-me deficiency and what are the morphological and functional consequences? 4) Does ABC-me transport a heme biosynthesis intermediate, product or co-factor, and in which direction? 5) Does ABC-me facilitate heme biosynthesis indirectly by opposing mitochondrial stress.

描述（由申请人提供）：由于血红素生物合成异常导致的许多疾病影响红细胞生成。在正常红细胞成熟过程中，血红素前体在线粒体中产生，在细胞质中进行修饰，然后返回线粒体与铁进行最终组装。值得注意的是，有毒血红素中间体或底物的积累以及继发性线粒体损伤是所有血红素生物合成障碍的病理生理学的关键因素。然而，血红素产物、副产物和中间体向或从线粒体基质的输出或输入的机制仍知之甚少。该提案将重点关注利用我们发现的 ABC-me（一种新型线粒体红细胞转运蛋白）的此类机制。 ABC-me 表达受红细胞转录因子 GATA-1 控制，并受血红素下调。在分化红白血病细胞时，ABC-me 是血红素生物合成的速率限制。因此，ABC-me 是唯一参与血红素生物合成的线粒体内膜转运蛋白。为了探索其在血红素生物合成中的功能，我们开发了 ABC-me 缺陷细胞培养模型和蛋白脂质体中重建转运蛋白的功能测定。我们已经确定，ABC-me 活性降低的分化红系细胞产生的血红素较少，并表现出线粒体应激的迹象。我们假设参与血红素途径的转运蛋白充当反应底物、中间体和副产物的看门人，从而将重要最终产物的生产与有毒中间体的保护结合起来。我们提出了一种生物化学和生物物理相结合的方法来研究 ABC-me 在血红素生物合成中的功能及其故障的后果。我们将解决以下问题：1）ABC-me 促进血红素生物合成途径中的哪些步骤？ 2) ABC-me 缺乏是否会导致血红素前体在细胞质和线粒体中积累？ 3) 与 ABC-me 缺乏相关的线粒体应激的来源是什么？其形态和功能后果是什么？ 4) ABC-me 是否转运血红素生物合成中间体、产物或辅因子，以及朝哪个方向？ 5) ABC-me 是否通过对抗线粒体应激间接促进血红素生物合成。