Studies on the pathophysiology and gene therapy for adrenoleukodystrophy using knock-out mice

X连锁肾上腺脑白质营养不良（ALD）是由肾上腺脑白质营养不良（ALDP）基因突变引起的，其主要生化异常是由于过氧化物酶体β氧化功能受损而导致组织和体液中极长链脂肪酸（VLCFA）的积累。我们用ALDP缺陷小鼠阐明了其病理生理学。ALD成纤维细胞中VLCFA β-氧化不被VLACS单独过表达所纠正，而是通过VLACS和ALDP的过表达来纠正。Western印迹分析显示，VLACS蛋白存在于ALDP缺陷小鼠的每个组织中。通过Nycodenz梯度离心纯化肝脏过氧化物酶体。仅在对照小鼠的过氧化物酶体部分中检测到VLACS蛋白，而在ALDP缺陷小鼠的胞质溶胶部分以及过氧化物酶体部分中检测到VLACS蛋白。这些结果表明，ALDP参与VLACS转运到过氧化物酶体中，并且除非定位在过氧化物酶体中，否则VLACS不能催化VLCFA β-氧化。

X-linked adrenoleukodystrophy (ALD) is caused by the mutation of ALD protein (ALDP) gene.Its principal biochemical abnormality is the accumulation of very long chain fatty acids (VLCFA) in tissues and body fluids, due to the impairment of beta-oxidatation in the peroxisome. We clarify its pathophysiology using the ALDP-deficient mice.VLCFA beta-oxidation in the ALD fibroblasts was not corrected by overxpression of VLACS only but done by overxpression of both VLACS and ALDP.Western blot analysis revealed that the VLACS protein was present in each tissue from the ALDP-deficient mouse. Liver peroxisomes were purified by Nycodenz gradient centrifugation. The VLACS protein was detected only in the peroxisomal fraction from the control mouse, while it was detected in the cytosol fraction as well as the peroxisomal fraction from the ALDP-deficient mouse. These results indicated that ALDP is involved in the transport of VLACS into the peroxisome and that VLACS can not catalyze VLCFA beta-oxidation unless localized in the peroxisome.