Secció d'Errors Congènits del Metabolisme, Servei de Bioquímica i Genètica Molecular, Hospital Clinic, IDIBAPS, 08028 Barcelona, Spain.
J Inherit Metab Dis. 2013 Sep;36(5):841-7. doi: 10.1007/s10545-012-9565-z. Epub 2012 Nov 22.
Cofactor disorders of mitochondrial energy metabolism are a heterogeneous group of diseases with a wide variety of clinical symptoms, particular metabolic profiles and variable enzymatic defects. Mutations in NFU1 were recently identified in patients with fatal encephalopathy displaying a biochemical phenotype consistent with defects in lipoic acid-dependent enzymatic activities and respiratory chain complexes. This discovery highlighted the molecular function of NFU1 as an iron-sulfur(Fe-S) cluster protein necessary for lipoic acid biosynthesis and respiratory chain complexes activities. To understand the pathophysiological mechanisms underlying this disease we have characterized the protein expression profiles of patients carrying NFU1 mutations. Fibroblasts from patients with the p.Gly208Cys mutation showed complete absence of protein-bound lipoic acid and decreased SDHA and SDHB subunits of complex II. In contrast, subunits of other respiratory chain complexes were normal. Protein lipoylation was also decreased in muscle and liver but not in other tissues available (brain, kidney, lung) from NFU1 patients. Although levels of the respiratory chain subunits were unaltered in tissues, BN-PAGE showed an assembly defect for complex II in muscle, consistent with the low enzymatic activity of this complex. This study provides new insights into the molecular bases of NFU1 disease as well as into the regulation of NFU1 protein in human tissues. We demonstrate a ubiquitous expression of NFU1 protein and further suggest that defects in lipoic acid biosynthesis and complex II are the main molecular signature of this disease, particularly in patients carrying the p.Gly208Cys mutation.
辅酶代谢缺陷是一组异质性疾病，具有广泛的临床表现、特定的代谢谱和不同的酶缺陷。最近在表现出与脂酰基辅酶 A 依赖性酶活性和呼吸链复合物缺陷一致的生化表型的致命性脑病患者中发现了 NFU1 基因突变。这一发现强调了 NFU1 的分子功能，即作为铁硫（Fe-S）簇蛋白，对于脂酰基辅酶 A 的生物合成和呼吸链复合物活性是必需的。为了了解这种疾病的病理生理机制，我们对携带 NFU1 突变的患者的蛋白表达谱进行了特征描述。p.Gly208Cys 突变患者的成纤维细胞显示完全缺乏蛋白结合的脂酰基辅酶 A 和复合物 II 的 SDHA 和 SDHB 亚基。相比之下，其他呼吸链复合物的亚基正常。尽管在组织中呼吸链亚基的水平没有改变，但 BN-PAGE 显示肌肉中复合物 II 的组装缺陷，与该复合物的低酶活性一致。这项研究为 NFU1 疾病的分子基础以及 NFU1 蛋白在人体组织中的调节提供了新的见解。我们证明了 NFU1 蛋白的普遍表达，并进一步表明脂酰基辅酶 A 生物合成和复合物 II 的缺陷是该疾病的主要分子特征，特别是在携带 p.Gly208Cys 突变的患者中。
