Functional interaction between peroxisomes and cholesterol metabolisms in glial cells

1.肾上腺脑白质营养不良（X-ALD）是一种以中枢神经系统进行性脱髓鞘为特征的遗传性疾病。X-ALD是由于ABCD 1基因突变引起的。它编码一半大小的过氧化物酶体ABC蛋白，肾上腺脑白质营养不良蛋白（ABCD 1），由745个氨基酸组成。ABCD 1包含一个跨膜和一个ATP结合结构域，并且应该在二聚化后起作用。在X-ALD患者的错义突变中，超过70%的突变ABCD 1 s未被免疫印迹分析检测到。我们研究了9个突变ABCD 1错义突变的细胞内命运。我们已经发现，不仅突变ABCD 1的功能障碍，而且突变ABCD 1 s的错误定位以及降解与X-ALD相关。此外，我们发现突变ABCD 1 s在短时间内被蛋白酶体迅速降解. ABCD 1的功能障碍导致极长链脂肪酸（VLCFA）在总体液中的积累，特别是在大脑中。ABCD 1被认为是 ...更多信息 是VLCFA或VLCFA-CoA的转运蛋白，但其确切功能尚不清楚。为了研究ABCD 1在胶质细胞脂质代谢中的作用，我们制备了ABCD 1敲除的胶质母细胞瘤细胞和ABCD 1敲除的小鼠原代星形胶质细胞，并分析了这些细胞中的VLCFA和胆固醇代谢。这项研究表明，ABCD 1的功能障碍导致神经胶质细胞中脂肪酸延长酶的上调以及过氧化物酶体VLCFA β-氧化的减少。这些VLCFA代谢的破坏可能导致VLCFA在X-ALD脑中积聚。在ABCD 1敲低的THP-1巨噬细胞中，胆固醇向巨噬细胞的掺入减少，ApoAI依赖的胆固醇流出增加。此外，ApoE分泌到培养基中和胆固醇合成显著增加。这些结果表明，THP-1巨噬细胞中ABCD 1功能障碍可导致胆固醇流出增加，虽然ABCD 1与胆固醇代谢之间的功能相互作用尚不清楚，但ABCD 1可能在维持胶质细胞和巨噬细胞胆固醇稳态中起作用。胶质细胞胆固醇代谢紊乱和VLCFA代谢紊乱可能与X-ALD的神经变性有关。少

1. Adrenoleukodystrophy (X-ALD) is an inherited disorder characterized by progressive demyelination of the central nervous system. X-ALD is due to the mutations in the ABCD1 gem. It encodes a half-size peroxisomal ABC protein, adrenoleukodystrophy protein (ABCD1), which consists of 745 amino acids. ABCD1 contains a transmembrane and an ATP-binding domain(s), and is supposed to work after dimerization. Among missense mutations in X-ALD patients, more than 70% of the mutant ABCD1s were not detected by immunoblot analysis. We examined intracellular fate of 9 mutant ABCD1s with missense mutation. We have found that not only dysfunction of mutant ABCD1 but also mistargeting as well as degradation of mutant ABCD1s would be associated with X-ALD. Furthermore, we found for the fast time that mutant ABCD1s were degraded rapidly by proteasomes.2. Dysfunction of ABCD1 leads to the accumulation of very long chain fatty acids (VLCFA) in total body fluids, especially in brain. ABCD1 has been thought … More to be a transporter of VLCFA or VLCFA-CoA, but the precise function is still unclear. To investigate the roles of ABCD1 in lipid metabolisms in glial cells, we prepared ABCD1-knockdown glioblastoma cells and ABCD 1-knockout mouse primary astrocytes, and analyzed the VLCFA and cholesterol metabolisms in these cells. This study shows that dysfunction of ABCD1 results in the up-regulation of fatty acid elongases as well as the reduction of peroxisomal VLCFA β-oxidation in glial cells. Disruption of these VLCFA metabolisms might result in the VLCFA accumulation in X-ALD brain. Furthermore, cholesterol level was significantly decreased in ABCD1-knockdown glioblastoma cells.In ABCD1-knockdown THP-1 macrophage, incorporation of cholesterol into macrophage was decreased and ApoAI-dependent cholesterol efflux was increased. In addition, ApoE secretion into medium and cholesterol synthesis was significantly increased. These results suggest that cholesterol efflux was inc eased by the dysfunction of ABCD1 in THP-1 macrophage.Although the functional interaction between ABCD1 and cholesterol metabolisms remains to be determined, ABCD1 might have a role for maintaining the cellular cholesterol homeostasis both in glial cells and macrophage. The disturbed cholesterol as well as VLCFA metabolisms in glial cells might be related to the neurodegeneration in X-ALD. Less