Regulation of heme synthesis by mitochondrial proteins

摘要 该项目的长期目标是确定调节“管家”线粒体的机制。 血红素代谢血红素在生命必需过程的氧化还原反应中起着核心作用， 线粒体呼吸我的研究项目特别感兴趣的是1。识别蛋白质 调节线粒体血红素/卟啉转运和2.这些蛋白质是 线粒体内稳态机制，在结构上或功能上与线粒体的核心酶相互作用。 血红素合成途径虽然血红素合成的酶被很好地表征，并且在所有酶中是相同的， 在组织中，将血红素合成与细胞需求相结合的调节机制非常差 明白这些调节机制的重要性由于存在着某些疾病而得到强调。 血红素合成和铁代谢是由蛋白质的失调引起的，这些蛋白质通常与 “管家”稳态过程或线粒体呼吸。尽管所有组织都需要血红素， 我们大多数关于血红素合成调控方面的研究都集中在红系细胞上， 了解血红素在其他细胞类型中的合成。这个项目使用我们的知识红血红素合成 作为一个跳板，以确定血红素监管机制所需的管家血红素合成。 项目1旨在鉴定非红细胞线粒体卟啉转运所需的蛋白质， 细胞血红素中间体是光敏的和细胞毒性的，需要细胞快速和有效地代谢血红素的机制。 有效地运输血红素中间体穿过细胞膜，到血红素合成酶中的下一个酶。 通路当不能有效转运时，细胞毒性卟啉在细胞中积累，可能导致 卟啉症和血红素缺乏症。虽然TMEM 14 C对于红系细胞中的卟啉转运是必需的， TMEM 14蛋白不是非红系细胞中血红素合成所必需的。结合使用 TMEM 14 C抑制突变体的蛋白质组学和全基因组测序/RNAseq分析，我们将鉴定 在非红细胞中调节卟啉转运的新型线粒体蛋白。的长期目标 项目2是了解血红素合成复合物的调节蛋白质，调节管家 线粒体内稳态在这个项目期间，我们专注于普遍存在的线粒体解折叠酶， CLPX在调节血红素合成酶的活性和蛋白质稳定性中起重要作用。 我们发现CLPX的功能是高度组织特异性的，并建议了解其在系统性 在“管家”血红素合成的环境中调节血红素代谢。这些研究将提供 重要的数据集，这将是非常宝贵的线粒体蛋白解折叠酶社区，但也将是 对于确定CLPX如何通过血红素的严格调节来全面调节线粒体稳态至关重要。

ABSTRACT The long-term goal of this project is to identify the mechanisms that regulate “housekeeping” mitochondrial heme metabolism. Heme plays a central role in the redox reactions of life-essential processes such as mitochondrial respiration. My research program is particularly interested in 1. identifying proteins that regulate mitochondrial heme/porphyrin transport and 2. proteins that are part of the housekeeping mitochondrial homeostasis machinery that structurally or functionally interact with the core enzymes of the heme synthesis pathway. While the enzymes of the heme synthesis are well characterized and identical in all tissues, the regulatory mechanisms that couple heme synthesis to cellular requirements are very poorly understood. The importance of these regulatory mechanisms is underscored by the existence of disorders of heme synthesis and iron metabolism that are caused by dysregulation of proteins that are commonly associated with “housekeeping” homeostatic processes or mitochondrial respiration. Although all tissues require heme, most of our studies on regulatory aspects of heme synthesis have focused on erythroid cells to the exclusion of understanding heme synthesis in other cell types. This project uses our knowledge of erythroid heme synthesis as a springboard to identify heme regulatory mechanisms that are required for housekeeping heme synthesis. Project 1 aims to identify proteins that are required for mitochondrial porphyrin transport in non-erythroid cells. Heme intermediates are photosensitive and cytotoxic, requiring mechanisms for cells to quickly and efficiently transport heme intermediates across cell membranes, to the next enzyme in the heme synthetic pathway. When efficient transport does not occur, cytotoxic porphyrins accumulate in cells, potentially causing porphyria and heme deficiency. While TMEM14C is essential for porphyrin transport in erythroid cells, TMEM14 proteins are not required for heme synthesis in non-erythroid cells. Using a combination of proteomics and whole genome sequencing/RNAseq analysis of TMEM14C suppressor mutants, we will identify novel mitochondrial proteins that regulate porphyrin transport in non-erythroid cells. The long-term goal of Project 2 is to understand the regulation of the heme synthesis complex by proteins that regulate housekeeping mitochondrial homeostasis. During this project period, we focus on the ubiquitous mitochondrial unfoldase, CLPX, which plays an essential role in regulating the activity and protein stability of heme synthesis enzymes. We show that the function of CLPX is highly tissue-specific, and propose to understand its role in the systemic regulation of heme metabolism in the setting of “housekeeping” heme synthesis. These studies will provide essential datasets that will be invaluable to the mitochondrial protein unfoldase community, but will also be essential for determining how CLPX globally regulates mitochondrial homeostasis via tight regulation of heme.