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，有两种主要的临床表型，一种是迅速致命的儿童期发作的大脑形式，另一种是较轻的、缓慢进展的成年期发作的周围神经病变。生物化学方面，过氧化物酶体中超长链酰基辅酶a合成酶（VLCS）对超长链脂肪酸（VLCFA）激活的降低导致VLCFA β -氧化受损，随后组织VLCFA水平升高。ALDP是XALD中基因缺陷的产物，类似于atp结合盒跨膜转运蛋白，而不是VLCS。我们假设VLCS/ALDP相互作用的破坏是VLCS活性丧失的原因，从而导致XALD。我们发现了一个包含VLCS的新蛋白家族，并克隆了6个人类、小鼠和酵母VLCS基因及其同源物。本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成部分，并确定该过程如何在XALD中被破坏。第二个目标是描述这个新描述的蛋白质家族成员在XALD和VLCFA代谢方面的特征。为了实现这一点，VLCFA的激活将在酵母和小鼠模型系统中进行研究。本文将对酵母VLCS （Fatlp）进行表征，并鉴定其他具有VLCS活性的酶。基因破坏策略将用于阐明酵母中VLCFA激活的组成部分，并为同源哺乳动物基因的表达创造载体。剩余的小鼠和人类vlcs将被克隆并鉴定其基因产物。通过靶向基因破坏建立的小鼠XALD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的表型表达，将绘制各种小鼠和人类VLCS基因的图谱，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.