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，一种是儿童期起病的快速致死性脑型，另一种是病情较轻、进展缓慢的成人周围神经病。在生物化学方面，过氧化酶体中的超长链酰辅酶A合成酶(VLCs)降低了超长链脂肪酸(VLCFA)的激活，导致VLCFAβ氧化受损，从而导致组织VLCFA水平的升高。ALDP是XALD基因缺陷的产物，类似于ATP结合盒跨膜转运蛋白，不是VLCs。我们假设VLCs/ALDP相互作用的中断是VLCs活性丧失的原因，从而导致XALD。我们已经鉴定了包括VLCs在内的一个新的蛋白质家族，并克隆了六个人、小鼠和酵母VLCs基因及其同源物。这项建议的一个目标是确定过氧化体VLCFA激活系统的要求和组件，并确定这一过程在XALD中是如何被破坏的。第二个目标是关于XALD和VLCFA代谢的这个新描述的蛋白质家族的成员的特征。为此，将在酵母和小鼠模型系统中研究VLCFA的激活。将对酵母VLCs(Fatlp)进行鉴定，并鉴定具有VLCs活性的其他酶。基因中断策略将被用来阐明酵母中VLCFA激活的成分，并创建一种表达同源哺乳动物基因的载体。剩下的小鼠和人类VLCS将被克隆，并对它们的基因产品进行鉴定。通过靶向基因破坏建立的XALD小鼠模型将被用于研究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的组织表达是否会影响XALD的表型表达，我们将定位各种小鼠和人类VLCs基因，并将它们的映射位置与候选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.