Pei Zhengtong, Oey Nadia A, Zuidervaart Maartje M, Jia Zhenzhen, Li Yuanyuan, Steinberg Steven J, Smith Kirby D, Watkins Paul A
Kennedy Krieger Institute, Johns Hopkins University School of Medicine, 707 N. Broadway, Baltimore, MD 21205, USA.
J Biol Chem. 2003 Nov 21;278(47):47070-8. doi: 10.1074/jbc.M310075200. Epub 2003 Sep 15.
Acyl-CoA synthetases play a pivotal role in fatty acid metabolism, providing activated substrates for fatty acid catabolic and anabolic pathways. Acyl-CoA synthetases comprise numerous proteins with diverse substrate specificities, tissue expression patterns, and subcellular localizations, suggesting that each enzyme directs fatty acids toward a specific metabolic fate. We reported that hBG1, the human homolog of the acyl-CoA synthetase mutated in the Drosophila mutant "bubblegum," belongs to a previously unidentified enzyme family and is capable of activating both long- and very long-chain fatty acid substrates. We now report that when overexpressed, hBG1 can activate diverse saturated, monosaturated, and polyunsaturated fatty acids. Using in situ hybridization and immunohistochemistry, we detected expression of mBG1, the mouse homolog of hBG1, in cerebral cortical and cerebellar neurons and in steroidogenic cells of the adrenal gland, testis, and ovary. The expression pattern and ability of BG1 to activate very long-chain fatty acids implicates this enzyme in the pathogenesis of X-linked adrenoleukodystrophy. In neuron-derived Neuro2a cells, mBG1 co-sedimented with mitochondria and was found in small vesicular structures located in close proximity to mitochondria. RNA interference was used to decrease mBG1 expression in Neuro2a cells and led to a 30-35% decrease in activation and beta-oxidation of the long-chain fatty acid, palmitate. These results suggest that in Neuro2a cells, mBG1-activated long-chain fatty acids are directed toward mitochondrial degradation. mBG1 appears to play a minor role in very long-chain fatty acid activation in these cells, indicating that other acyl-CoA synthetases are necessary for very long-chain fatty acid metabolism in Neuro2a cells.
酰基辅酶A合成酶在脂肪酸代谢中起关键作用，为脂肪酸分解代谢和合成代谢途径提供活化底物。酰基辅酶A合成酶由众多蛋白质组成，这些蛋白质具有不同的底物特异性、组织表达模式和亚细胞定位，这表明每种酶将脂肪酸导向特定的代谢命运。我们报道，hBG1是果蝇突变体“泡泡糖”中突变的酰基辅酶A合成酶的人类同源物，属于一个先前未鉴定的酶家族，能够激活长链和极长链脂肪酸底物。我们现在报道，当过度表达时，hBG1可以激活多种饱和、单不饱和和多不饱和脂肪酸。使用原位杂交和免疫组织化学，我们在大脑皮质和小脑神经元以及肾上腺、睾丸和卵巢的类固醇生成细胞中检测到了hBG1的小鼠同源物mBG1的表达。BG1激活极长链脂肪酸的表达模式和能力表明该酶与X连锁肾上腺脑白质营养不良的发病机制有关。在神经元来源的Neuro2a细胞中，mBG1与线粒体共沉降，并存在于紧邻线粒体的小泡状结构中。RNA干扰被用于降低Neuro2a细胞中mBG1的表达，并导致长链脂肪酸棕榈酸酯的激活和β氧化降低30 - 35%。这些结果表明，在Neuro2a细胞中，mBG1激活的长链脂肪酸被导向线粒体降解。mBG1在这些细胞的极长链脂肪酸激活中似乎起次要作用，这表明其他酰基辅酶A合成酶对于Neuro2a细胞中的极长链脂肪酸代谢是必需的。
