MITOCHONDRIAL SHORT CHAIN 3-OH-ACYL-COA DEHYDROGENASES

线粒体脂肪酸β-氧化是高度氧化的哺乳动物组织的主要能量来源，对肝脏中酮体的中间代谢和产生是必不可少的。人类脂肪酸氧化基因的遗传缺陷会导致急性肝功能衰竭，这是一种类似雷氏综合征的表型，表现为低酮症、低血糖、心肌病、骨骼肌病或儿童猝死。这个途径由12种不同的核苷酸编码的酶催化的四个酶步骤组成，这些酶是发育调节的和组织特异性表达的。这项建议侧重于催化第三步的两种酶，短链3-羟基-酰基-辅酶A脱氢酶(SCHAD)。AIMS 1和2将检验这样一个假设，即Schad-1和-2基因的组织特异性和发育表达与其他脂肪酸氧化酶基因协调，并涉及对能量需求和营养线索做出反应的核激素受体转录因子。目的2利用人Schad-1基因和体外转基因小鼠定位关键调控序列。根据Schad-1的晶体结构和蛋白质同源性，目标3将在细菌中表达正常和突变的SCHADs后，确定Schad-1的结构与功能关系，以探索Schad-1和长链3-羟基酰辅酶A脱氢酶共享共同结构域的假设。使用我们已经确定的人类基因序列，Aim 4将描绘儿童中Schad-1或-2的突变，以检验Schad缺乏和环境压力导致雷氏综合征样急性肝衰竭表型的提议。目的5研究我们发现的3个人Schad-1基因突变对结构和功能的影响以及Schad缺陷的发病机制，以探讨Schad错义突变导致错误折叠导致线粒体内快速降解的假说。目的6是定义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)应激源对结果的影响，并类似地研究Schad-2基因敲除。这些研究将增进对脂肪酸氧化紊乱导致儿童急性肝功能衰竭、心肌病和猝死的发病机制的了解。

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.