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：一种是快速致命的、儿童期发病的脑部形式，另一种是较温和、缓慢进展的成人发病的周围神经病变。从生化角度来看，过氧化物酶体中极长链酰基辅酶A合成酶（VLCS）导致极长链脂肪酸（VLCFA）活化减少，导致VLCFAβ氧化受损，随后导致组织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，但不是 VLCS。 我们假设 VLCS/ALDP 相互作用的破坏导致 VLCS 活性丧失，从而导致 XALD 丧失。我们已经鉴定了一个新的蛋白质家族，其中包括 VLCS，并克隆了 6 个人类、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 激活系统的要求和组件，并确定 XALD 中如何破坏该过程。第二个目标是表征这个新描述的蛋白质家族成员的 XALD 和 VLCFA 代谢特征。为了实现这一目标，将在酵母和小鼠模型系统中研究 VLCFA 激活。将鉴定酵母 VLCS (Fatlp) 的特性，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 激活的成分，并创建用于表达同源哺乳动物基因的载体。剩余的小鼠和人类 VLCS 将被克隆并表征其基因产物。通过靶向基因破坏创建的 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，将绘制各种小鼠和人类 VLCS 基因图谱，并将它们的图谱位置与候选 XALD 修饰基因的新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.