MITOCHONDRIAL SHORT CHAIN 3-OH-ACYL-COA DEHYDROGENASES

线粒体脂肪酸β -氧化是高氧化性哺乳动物组织的主要能量来源，对肝脏的中间代谢和酮体的产生至关重要。人类脂肪酸氧化基因的遗传缺陷导致急性肝衰竭，一种雷氏综合征样的低酮、低血糖表型；心肌病;骨骼肌病;或者童年突然意外死亡。该途径由12种不同的核编码酶催化的四个酶步骤组成，这些酶是发育调节和组织特异性表达的。本文主要研究催化第三步的两种酶，即短链3-羟基酰基辅酶a脱氢酶（SCHAD）。目的1和目的2将检验SCHAD-1和-2基因的组织特异性和发育性表达与其他脂肪酸氧化酶基因协调，并涉及响应能量需求和营养线索的核激素受体转录因子的假设。Aim 2将使用人类SCHAD-1基因和体外转染和转基因小鼠来定位关键的调控序列。基于SCHAD-1的晶体结构和蛋白同源性，Aim 3将确定正常SCHAD-1和突变SCHAD-1在细菌中表达后的结构-功能关系，探索SCHAD-1和长链3-羟基酰基辅酶a脱氢酶具有共同结构域的假设。利用我们已经确定的人类基因序列，Aim 4将描述儿童SCHAD-1或-2突变，以检验SCHAD缺乏和环境压力导致急性肝衰竭的雷氏综合征样表型的建议。目的5将研究我们发现的三种人类SCHAD-1突变对SCHAD缺陷的结构和功能的影响，探讨SCHAD错义突变导致线粒体内快速降解继发于错误折叠的假设。目的6是确定我们在小鼠中创建的SCHAD-1基因消融的表型，作为人类疾病的模型，检查环境和药物（阿司匹林和对乙酰氨基酚）压力源对结果的影响，并类似地研究SCHAD-2敲除。这些研究将增加对脂肪酸氧化障碍引起急性肝功能衰竭、心肌病和儿童猝死的发病机制的理解。

Mitochondrial fatty acid beta-oxidation is the major source of energy in highly oxidative mammalian tissues and is essential for intermediary metabolism and production of ketone bodies in liver. Human genetic defects in fatty acid oxidation genes cause acute liver failure, a Reye's syndrome-like phenotype of hypoketotic, hypoglycemia; cardiomyopathy; skeletal myopathy; or sudden, unexpected childhood death. This pathway consists of four enzymatic steps catalyzed by 12 different nuclearly-encoded enzymes that are developmentally-regulated and tissue- specifically expressed. This proposal focuses on two enzymes catalyzing the third step, the short chain 3-hydroxy-acyl-CoA dehydrogenases (SCHAD). Aims 1 and 2 will examine the hypothesis that tissue-specific and developmental expression of the SCHAD-1 and -2 genes is coordinated with other fatty acid oxidation enzyme genes and involves nuclear hormone receptor transcription factors responsive to energy requirements and nutritional cues. Aim 2 will use the human SCHAD-1 gene and in vitro transfection and transgenic mice to locate critical regulatory sequences. Based upon the SCHAD-1 crystal structure and protein homologies, Aim 3 will determine structure-function relationships of SCHAD-1 of normal and mutant SCHADs after expression in bacteria to explore the hypothesis that SCHAD-1 and long chain 3-hydroxy- acyl-CoA dehydrogenase share common structural domains. Using the human gene sequences we have determined, Aim 4 will delineate SCHAD-1 or -2 mutations in children to examine the proposal that SCHAD deficiency and environmental stresses cause a Reye's syndrome-like phenotype of acute hepatic failure. Aim 5 will examine the effects of the three human SCHAD-1 mutations we have discovered on structure and function, the pathogenetics of SCHAD deficiency, to explore the hypothesis that SCHAD missense mutations result in rapid intramitochondrial degradation secondary to misfolding. Aim 6 is to define the phenotype of SCHAD-1 gene ablation we created in mice as a model of human disease, to examine the effects of environmental and drug (aspirin and acetaminophen) stressors on outcome and to similarly study an SCHAD-2 knockout. These studies will augment understanding of the pathogenesis of fatty acid oxidation disorders causing acute liver failure, cardiomyopathy, and sudden death in children.