过氧化物酶体脂肪酸转运蛋白ABCD1/2/3的结构与功能研究

脂肪酸在细胞质中被活化成脂酰辅酶A后分别进入线粒体和过氧化物酶体进行β-氧化而产生能量。ABC转运蛋白ABCD1/2/3负责向过氧化物酶体内转运超长链脂肪酸和支链脂肪酸，ABCD1基因的突变将导致超长链脂肪酸在胞质中大量积累，进而诱发X染色体伴性遗传肾上腺脑白质营养不良症。为了阐明D亚家族ABC转运蛋白的底物特异性和转运机制，以及三者之间的异同和功能关系，我们将利用晶体学或冷冻电镜技术解析ABCD1/2/3在底物转运循环中关键节点不同构象的三维结构。结合ATP酶活和转运活性实验等鉴定负责底物识别和转运的关键氨基酸残基，揭示ABCD1/2/3转运不同脂肪酸底物的分子机制。同时，基于结构比对和临床突变位点定位分析，结合生化研究阐明相关突变的致病机理。该研究不仅能加深我们对ABCD1/2/3转运脂肪酸精细分子机制的理解，还将为研究相关人类疾病的致病机理以及临床治疗和药物开发提供重要的理论基础。

The fatty acid is activated into the corresponding fatty acyl-CoA in cytoplasm, and transported to the mitochondria or peroxisomes for β-oxidation to produce ATP, providing the energy for cell metabolism. Previous reports showed that three ABC transporters ABCD1, ABCD2 and ABCD3 play key roles in the transport of very long-chain fatty acids and branch chain fatty acids into peroxisome, respectively. Mutations in human ABCD1 gene resulted in the accumulation of very long-chain fatty acids in the cytosol, and eventually led to the so-called X-linked Adrenoleukodystrophy (X-ALD), which is a common peroxisomal disease. To elucidate the substrate specificity and transport mechanism, and structure-based functional diversity, in this project we will solve the 3-D structures of ABCD1/2/3 at different stages of transport, to capture the key snapshots during the transportation cycle. Combined with biochemical assays, we will illustrate the structural basis for the various substrates transported by ABCD1/2/3. In addition, the structures will enable us to precisely map the clinical mutations and figure out the molecular mechanism of the pathogenesis of X-ALD. These findings will provide not only the structural insights into the ABC transporters in subfamily D, but also helpful hints for the development of pharmacotherapeutics and clinical drugs for the related human diseases.