Functional interaction of peroxisomal ABC proteins and acyl-CoA sythesis in glial cells

1. X连锁肾上腺脑白质营养不良（ALD）是一种以极长链脂肪酸（VLCFA）异常积累为特征的神经退行性疾病。它是由编码过氧化物酶体膜ABC蛋白ALDP的基因ABCD 1缺陷引起的。然而，ALDP在中枢神经系统中的作用以及X-ALD的神经变性机制尚不清楚。在本研究中，我们分析了ALDP敲低胶质母细胞瘤细胞的脂质代谢。在ALDP敲低的细胞中，VLCFA β-氧化活性降低了约70%。此外，在这些细胞中，将[1-^<14>C]二十四烷酸掺入胆固醇酯级分中增加。此外，<14>在ALDP敲低的细胞中，[2-^ C]乙酸掺入胆固醇的量显著减少，并且胆固醇质量增加。这些结果表明，在胶质细胞中，ALDP的功能障碍导致胆固醇代谢以及VLCFA代谢的破坏。2.我们分析了从ALD-KO小鼠制备的原代小胶质细胞和星形胶质细胞的脂质代谢。与野生小鼠相比，VLCFA β-氧化活性显著降低。据报道，这些神经胶质细胞在神经元功能中具有重要作用。我们发现黄芩素5，6，7-三甲基醚（一种黄酮类衍生物）能够使X-ALD成纤维细胞异常的VLCFA代谢正常化。这种黄酮衍生物刺激过氧化物酶体VLCFA β-氧化，但抑制线粒体脂肪酸β-氧化。黄酮类化合物激活了酰基辅酶A合成酶的活性，表明酰基辅酶A合成酶的上调可能导致VLCFA β-氧化的刺激。4.克隆并鉴定了一种新的中链酰基辅酶A合成酶。该酶在脑、肾上腺、卵巢和睾丸中均有表达。

1.X-linked adrenoleukodystorophy (ALD) is a neurodegenerative disorder characterized by an abnormal accumulation of very long chain fatty acid (VLCFA). It is caused by a defect in the gene ABCD1 which encodes the peroxisomal membrane ABC protein, ALDP. However, the function of ALDP in CNS and the mechanism of the neurodegeneration in X-ALD were still unclear. In the present study, we have analyzed lipid metabolisms in ALDP-knockdown glioblastoma cells. In the ALDP-knockdown cells, the VLCFA β-oxidation activity was decreased by 〜70%. In addition, incorporation of [1-^<14>C]lignoceric acid into cholesterol ester fractions was increased in these cells. Furthermore, the incorporation of [2-^<14>C]acetic acid into cholesterol was significantly decreased and the cholesterol mass was increased in the ALDP-knockdown cells. These results indicate that in glial cells dysfunction of ALDP leads to the disruption of cholesterol metabolism as well as VLCFA metabolisms.2.We analyzed the lipid metabolisms of primary microglia and astrocyte prepared from ALD-KO mouse. The VLCFA β-oxidation activity was significantly decreased when compared with that from wild mouse. These glial cells are reported to have important roles in neuronal functions. Disruption of VLCFA metabolisms in these cells could lead to the neurodegeneration in X-ALD.3.We found that baicalein 5,6,7-trimethyl ether, a flavonoid derivative, have an ability to normalize the abnormal VLCFA metabolisms in X-ALD fibroblasts. This flavonoid derivative stimulated the peroxisomal VLCFA β-oxidation but inhibited the mitochondrial fatty acid β-oxidation. The flavonoid activated the acyl-CoA synthetase activities, suggesting that up-regulation of acyl-CoA synthetases could result in the stimulation of the VLCFA β-oxidation.4.A novel medium-chain acyl-CoA synthetase was cloned and characterized. This enzyme was expressed in brain, adrenal gland, ovary and testis.