Regulation of Hepatic Heme Metabolism

肝脏血红素代谢的调节

• 批准号: 7256875
• 负责人: HERBERT L BONKOVSKY
• 金额: $ 39.64万
• 依托单位: CAROLINAS MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 1987
• 资助国家: 美国
• 起止时间: 1987-01-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7256875
• 关键词: 5' Flanking Region; 5-Aminolevulinate synthase; Acute; Animals; Antioxidants; Arsenicals; Binding; Birds; Cell Culture System; Cells; Chemicals; Down-Regulation; Drug or Chemical; Enzymes; Gene Expression; Genes; Goals; Heat shock proteins; Heat-Shock Response; Heavy Metals; Heme; Heme Iron; Hemeproteins; Hepatic; Hepatocyte; Home environment; HuR protein; Human; Immune response; Inflammatory; Life; Mediating; Messenger RNA; Metabolism; Metalloporphyrins; Metals; Modeling; Molecular; Mus; Numbers; Organism; Oxidative Stress; Oxygenases; Pathway interactions; Pharmaceutical Preparations; Play; Porphyrias; Porphyrins; Protein Isoforms; Protoporphyrins; Rate; Reaction; Regulation; Repression; Research; Role; Stress; Synthase I; Testing; Tissues; Transcriptional Activation; Transition Elements; Up-Regulation; Work; cobaltiprotoporphyrin; derepression; enzyme pathway; heme 1; heme oxygenase-1; mRNA Stability; programs; transcription factor

DESCRIPTION (provided by applicant): The long-term goal of this research program is to understand the pathways and regulation of hepatic porphyrin and heme metabolism. Heme is a primordial molecule that is of critical importance to life on earth. The pathway of heme synthesis in humans and other higher animals is highly conserved. It requires the concerted action of eight enzymes, the first of which, called 5-aminolevulinate synthase (ALAS), is normally rate controlling. The pathway of heme breakdown is also highly conserved, and its rate is controlled by activity of the first enzyme of this pathway, called heme oxygenase (HO). Levels of expression of both hepatic ALAS-1 and HO-1 can be changed dramatically. The ALAS-1 gene can be up-regulated by certain drugs or chemicals, including drugs that may precipitate acute attacks of porphyria, and by chemicals that block heme synthesis. Activity of ALAS-1 can be decreased by heme, an example of end-product repression of a biosynthetic pathway. Heine may act on ALAS by both transcriptional and post-transcriptional mechanisms. The gene for the 1 isoform of HO (HO-1) can be up-regulated by a large number of chemical and physical perturbations, including oxidative stress, heat shock, transition metals, heavy metals, heme, and other metalloporphyrins. There is growing evidence that HO-1 (also called heat shock protein 32) plays a key role in protecting cells and tissues from oxidative and other stress and that products of the HO reaction are important antioxidants, neuro-muscular transmitters, and modulators of inflammatory and immune responses. The work proposed here will advance understanding of the molecular mechanisms that underlie the regulation of hepatic ALAS and HO-1, the two key enzymes of heme metabolism. The specific aims are as follows: A.I. Specific Aim #1: Complete characterization of the molecular mechanism(s) that are responsible for the up-regulation of the HO-1 gene by heme (iron protoporphyrin) and cobalt protoporphyrin (CoPP). A.2. Specific Aim #2: Complete characterization of the molecular mechanism(s) that are responsible for down-regulation of the ALAS-1 by heme and test whether CoPP or other selected metalloporphyrins have similar effects and mechanisms of down-regulation. A corollary to Specific Aims 1 and 2 will be to characterize the interrelationships between the reciprocal regulation of these two genes by metalloporphyrins. We will achieve these specific aims in cell culture systems, which provide physiologically relevant models of hepatic heme metabolism and in suitably treated intact mice. A.3. Specific Aim #3: Delineate the molecular mechanisms responsible for control of the stability of ALAS mRNA and how heme shortens the life of this mRNA. Our major hypotheses are that 1. heme or cobalt protoporphyrin up-regulate HO-1 gene expression and down-regulate ALAS-1 expression by specific interaction of transcription factor(s) with heme- or other metalloporphyrin- responsive sequences in the 5'-flanking regions of these genes; 2. there is also an important post-transcriptional effect of heme to decrease stability of ALAS-1 mRNA; 3. this post-transcriptional effect is mediated by HuR, the protein that plays a critical role in determining mRNA stability; 4. The above actions of heme are due to effects of heme binding to Bach-l, leading to derepression of HO-1, repression of ALAS-l, and up-regulation of the HuR-dependent pathway of ALAS-1 by mRNA breakdown; and 5. the molecular mechanisms that mediate heme regulation of ALAS-1 and HO-1 are similar in avian, human, and murine hepatocytes in culture or in intact organisms.

描述（由申请人提供）：该研究计划的长期目标是了解肝卟啉和血红素代谢的途径和调节。血红素是一种原始分子，对地球上的生命至关重要。人类和其他高等动物中血红素合成的途径是高度保守的。它需要八种酶的协同作用，其中第一种酶称为5-氨基乙酸合酶（Alas），通常是控制速率。血红素分解的途径也高度保守，其速率由该途径的第一种酶的活性（称为血红素加氧酶（HO））控制。肝ALAS-1和HO-1的表达水平可以大大改变。 ALAS-1基因可以被某些药物或化学物质（包括可能导致卟啉症急性发作的药物）以及阻断血红素合成的化学物质上调。血红素可以降低ALAS-1的活性，这是生物合成途径终产物抑制的一个例子。 Heine可以通过转录和转录后机制来对其作用。 HO（HO-1）的1同工型的基因可以通过大量的化学和物理扰动（包括氧化应激，热休克，过渡金属，重金属，血红素和其他金属核酸酯）上调。越来越多的证据表明，HO-1（也称为热休克蛋白32）在保护细胞和组织免受氧化和其他压力的影响中起关键作用，而HO反应的产物是重要的抗氧化剂，神经肌肉发射器，以及炎症和免疫反应的调节剂。这里提出的工作将提高人们对肝ALAS和HO-1调节的分子机制的理解，这是血红素代谢的两个关键酶。具体目的如下： 人工智能。具体目的＃1：完全表征分子机制，这些机制负责通过血红素（铁原磷脂）和钴原核蛋白（COPP）对HO-1基因上调的上调。 A.2。具体目的＃2：分子机制的完整表征，这些机制负责通过血红素对ALAS-1进行下调，并测试COPP还是其他选定的金属甲素是否具有相似的下调作用和机制。特定目的1和2的推论是表征金属磷脂对这两个基因的相互调控之间的相互关系。 我们将在细胞培养系统中实现这些特定目标，这些细胞培养系统提供了与生理相关的肝血红素代谢模型以及经过适当治疗的完整小鼠。 A.3。特定目的＃3：描述负责控制Alas mRNA稳定性的分子机制，以及血红素如何缩短该mRNA的寿命。 我们的主要假设是1。血红素或钴原原磷脂上调HO-1基因表达，并通过转录因子与这些基因5'-芬兰克的血红素或其他金属酚反应序列的特异性相互作用下调Alas-1表达； 2。血红素在降低Alas-1 mRNA的稳定性方面也有重要的转录后作用。 3。这种转录后效应是由HUR介导的，HUR是在确定mRNA稳定性中起关键作用的蛋白质。 4。血红素的上述作用是由于血红素与BACH-L的结合作用，导致HO-1的压抑，Alas-L的抑制以及通过mRNA崩溃对Alas-1的HUR依赖性途径的上调； 5。介导Alas-1和HO-1的血红素调节的分子机制在培养物或完整生物中的鸟类，人和鼠肝细胞中相似。