Dementia Research Group, School of Life Sciences, University of Sussex, Falmer, E Sussex, BN1 9QG, United Kingdom; Chemistry Department, College of Science, Mustansiriyah University, Baghdad, Iraq.
Dementia Research Group, School of Life Sciences, University of Sussex, Falmer, E Sussex, BN1 9QG, United Kingdom.
J Mol Biol. 2018 Oct 19;430(21):4119-4131. doi: 10.1016/j.jmb.2018.08.010. Epub 2018 Aug 16.
Alzheimer's disease is a tauopathy characterized by pathological fibrillization of tau protein to form the paired helical filaments (PHFs), which constitute neurofibrillary tangles. The methylthioninium (MT) moiety reverses the proteolytic stability of the PHF core and is in clinical development for treatment of Alzheimer's disease in a stable reduced form as leuco-MT. It has been hypothesized that MT acts via oxidation of cysteine residues, which is incompatible with activity in the predominantly reducing environment of living cells. We have shown recently that the PHF-core tau unit assembles spontaneously in vitro to form PHF-like filaments. Here we describe studies using circular dichroism, SDS-PAGE, transmission electron microscopy and site-directed mutagenesis to elucidate the mechanism of action of the MT moiety. We show that MT inhibitory activity is optimal in reducing conditions, that the active moiety is the reduced leuco-MT form of the molecule and that its mechanism of action is cysteine independent.
阿尔茨海默病是一种以 Tau 蛋白病理性纤维化为特征的疾病，这种蛋白会形成成对的螺旋丝（PHF），从而构成神经纤维缠结。甲硫蒽鎓（MT）部分可以逆转 PHF 核心的蛋白水解稳定性，目前正在临床开发中，以稳定的还原形式（白细胞 MT）用于治疗阿尔茨海默病。有人假设 MT 通过半胱氨酸残基的氧化起作用，而这与活细胞中主要的还原环境中的活性不兼容。我们最近已经表明，PHF 核心 Tau 单元在体外自发组装形成 PHF 样纤维。在这里，我们描述了使用圆二色性、SDS-PAGE、透射电子显微镜和定点突变来阐明 MT 部分的作用机制的研究。我们表明，MT 的抑制活性在还原条件下最佳，活性部分是分子的还原白细胞 MT 形式，其作用机制不依赖于半胱氨酸。
