XALD--ROLE OF VERY LONG CHAIN FATTY ACYL COA SYNTHETASES

X连锁肾上腺脑白质营养不良（XALD）是一种进行性神经退行性疾病，具有两种主要临床表型，即快速致命的儿童期发作的脑型和较轻的缓慢进行性成人期发作的周围神经病。在生物化学上，过氧化物酶体中极长链酰基辅酶A合成酶（VLCS）激活极长链脂肪酸（VLCFA）的减少导致VLCFA β-氧化受损，随后组织VLCFA水平升高。ALDP是XALD缺陷基因的产物，类似于ATP结合盒跨膜转运蛋白，不是VLCS。 我们假设VLCS/ALDP相互作用的破坏是导致VLCS活性丧失的原因，从而导致XALD。我们已经确定了一个新的蛋白质家族，包括VLCS，并克隆了六个人，小鼠和酵母VLCS基因和同源物。该提案的一个目标是确定过氧化物酶体VLCFA活化系统的要求和组成部分，并确定XALD中该过程如何被破坏。第二个目的是表征这个新描述的蛋白质家族的成员与XALD和VLCFA代谢。为了实现这一目标，将在酵母和小鼠模型系统中研究VLCFA的激活。将对酵母VLCS（Fatlp）进行表征，并鉴定具有VLCS活性的其他酶。基因破坏策略将用于阐明酵母中VLCFA激活的组分，并创建用于表达同源哺乳动物基因的载体。其余的小鼠和人VLCS将被克隆，其基因产物的特点。通过靶向基因破坏产生的XALD小鼠模型将用于研究ALDP缺失对VLCS活性、组织表达和亚细胞分布的影响。此外，为了确定VLCS组织表达是否会影响XALD中的表型表达，将对各种小鼠和人VLCS基因进行作图，并将其图谱位置与候选XALD修饰基因的出现的染色体位置进行比较。

X-linked adrenoleukodystrophy (XALD) is a progressive neurodegenerative disorder with two main clinical phenotypes, a rapidly fatal, childhood- onset cerebral form and a milder, slowly progressive adult-onset peripheral neuropathy. Biochemically, decreased very long-chain fatty acid (VLCFA) activation by very long-chain acyl-CoA synthetase (VLCS) in peroxisomes results in impaired VLCFA beta-oxidation and subsequent elevation of tissue VLCFA levels. ALDP, the product of the gene defective in XALD, resembles ATP-binding cassette transmembrane transporter proteins and is not a VLCS. We hypothesize that disruption of a VLCS/ALDP interaction is responsible for loss of VLCS activity, and thus XALD. We have identified a new family of proteins that includes VLCS, and have cloned six human, mouse and yeast VLCS genes and homologs. One objective of this proposal is to identify the requirements and components of the peroxisomal VLCFA activation system and to determine how this process is disrupted in XALD. A second objective is to characterize the members of this newly described protein family with respect to both XALD and VLCFA metabolism. To accomplish this, VLCFA activation will be studied in yeast and mouse model systems. The yeast VLCS (Fatlp) will be characterized and other enzymes with VLCS activity will be identified. Gene disruption strategies will be used both to elucidate the components of VLCFA activation in yeast and to create a vehicle for expression of homologous mammalian genes. The remaining mouse and human VLCSs will be cloned and their gene products characterized. The mouse model of XALD created by targeted gene disruption will then be used to investigate the effects of ALDP absence on VLCS activity, tissue expression, and subcellular distribution. Furthermore, to determine whether VLCS tissue expression could affect phenotypic expression in XALD, the various mouse and human VLCS genes will be mapped and their map positions compared to emerging chromosomal locations of candidate XALD modifier genes.