Kumar Amit, McGlohon Janie E, Estrada D Fernando
Department of Biochemistry, Jacobs School of Medicine and Biomedical Science, University at Buffalo, Buffalo, New York, USA.
Department of Biochemistry, Jacobs School of Medicine and Biomedical Science, University at Buffalo, Buffalo, New York, USA.
J Inorg Biochem. 2025 Oct;271:112969. doi: 10.1016/j.jinorgbio.2025.112969. Epub 2025 Jun 4.
Inherited mutations in the Ferredoxin Reductase (FdxR) gene can result in a spectrum of disorders that include auditory and optic neural atrophies as well as adrenal insufficiency. FdxR (also referred to as Adrenodoxin Reductase) is a flavoprotein located in the inner mitochondrial membrane. It is responsible for mediating electron transfer from NADPH to either Fdx1 (Adrenodoxin), which is the sole reductant for all seven mitochondrial cytochromes P450, or to the related ferredoxin Fdx2, which is a component in the FeS cluster biogenesis pathway. In most cases, the mechanistic causes that underpin FdxR-related neuropathies and steroid imbalances remain unknown. In this study, we investigate three clinically relevant variants of FdxR (R211Q, R275C, and R355Q) that exhibit classic FdxR-related disease phenotypes and are widely distributed in the protein. We use a combination of biophysical and biochemical techniques to evaluate both the FdxR:Fdx1 complex and the FdxR:Fdx2 complex since these redox complexes represent an important branch point in FdxR function. Two key findings from this study are that i) all three mutants alter the recognition of Fdx1 and Fdx2, despite R275C and R355Q being located distally from the expected site of interaction, and ii) R275C and R355Q disrupt the functional complex with Fdx1, but not with Fdx2. These findings are supplemented with 2D NMR data of each mutant FdxR complex. In summary, this work implicates protein instability and degradation as the proximal cause of FdxR-related disease, with a secondary cause being the disruption of cytochrome P450-mediated metabolism in mitochondria.
铁氧化还原蛋白还原酶（FdxR）基因的遗传突变可导致一系列疾病，包括听觉和视神经萎缩以及肾上腺功能不全。FdxR（也称为肾上腺皮质铁氧化还原蛋白还原酶）是一种位于线粒体内膜的黄素蛋白。它负责介导电子从NADPH转移至Fdx1（肾上腺皮质铁氧化还原蛋白）或相关的铁氧化还原蛋白Fdx2，其中Fdx1是所有七种线粒体细胞色素P450的唯一还原剂，而Fdx2是铁硫簇生物合成途径的一个组成部分。在大多数情况下，导致FdxR相关神经病变和类固醇失衡的机制原因仍不清楚。在本研究中，我们研究了FdxR的三种临床相关变体（R211Q、R275C和R355Q），它们表现出典型的FdxR相关疾病表型，并且在该蛋白中广泛分布。我们结合使用生物物理和生化技术来评估FdxR:Fdx1复合物和FdxR:Fdx2复合物，因为这些氧化还原复合物代表了FdxR功能中的一个重要分支点。本研究的两个关键发现是：i）尽管R275C和R355Q位于远离预期相互作用位点的位置，但所有三个突变体都会改变对Fdx1和Fdx2的识别；ii）R275C和R355Q会破坏与Fdx1的功能复合物，但不会破坏与Fdx2的功能复合物。这些发现得到了每个突变体FdxR复合物的二维核磁共振数据的补充。总之，这项工作表明蛋白质不稳定性和降解是FdxR相关疾病的近端原因，次要原因是线粒体中细胞色素P450介导的代谢受到破坏。
