Charge-Pairing Mechanism of Phosphorylation Effect upon Amyloid Fibrillation of Human Tau Core Peptide
Charge-Pairing Mechanism of Phosphorylation Effect upon Amyloid Fibrillation of Human Tau Core Peptide
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DOI：
10.1021/bi8010994
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发表时间：
2008-11-11
期刊：
影响因子：
2.9
通讯作者：
Konno, Takashi
中科院分区：
文献类型：
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作者：
Inoue, Masafumi;Hirata, Akiyoshi;Konno, Takashi
原纤维蛋白，人tau蛋白的磷酸化被认为在阿尔茨海默病的发病机制中起关键作用。为了阐明磷酸化对tau纤维化影响的分子机制，我们合成了肽VQTVY（310）K（PHF 6）及其磷酸化衍生物（PHF（6）pY）。PHF6是一个围绕在体内磷酸化位点Tyr310周围的部分肽，并形成类似于全长tau蛋白产生的淀粉样蛋白型原纤维。采用光谱和显微镜方法研究了PHF 6和PHF 6pY的原纤化过程，并确定了原纤化的临界浓度，比较了两种原纤化过程的稳定性。结果表明，磷酸化通过改变PHF 6对pH和离子强度的依赖性，强烈影响PHF 6的原纤化倾向。在此基础上，我们认为磷酸基团上的带电位点及其与邻近带电残基的静电配对是磷酸化效应的物理来源。为了验证这种电荷配对机制，我们使用一系列具有非原生电荷分布的PHF6衍生物进行了实验。分子间的静电相互作用模式也证明了由两种不同的肽物种组成的系统，发现当微量的磷酸化PHF6分子共存时，非磷酸化PHF6的原纤化急剧增强。利用PHF 6纤维的晶体坐标的模拟分析也被用于解释在分子水平上的实验结果。本研究使用模型肽系统，为我们提供了一个微观上深入了解tau蛋白磷酸化在淀粉样蛋白相关疾病中的作用。
Phosphorylation of a fibrillogenic protein, human tau, is believed to play crucial roles in the pathogenesis of Alzheimer's disease. For elucidating molecular mechanisms of the phosphorylation effect on tau fibrillation, we synthesized a peptide, VQTVY(310)K (PHF6) and its phosphorylated derivative (PHF(6)pY). PHF6 is a partial peptide surrounding a plausible in vivo phosphorylation site Tyr310 and forms amyloid-type fibrils similar to those generated by full-length tau. Fibrillation of PHF6 and PHF6pY were studied by spectroscopic and microscopic methods, and the critical concentration of the fibrillation was determined for comparing the fibril stability. The results showed that the phosphorylation strongly influenced the fibrillation propensity of PHF6 by changing its dependency on pH and ionic strength. On the basis of the observations, we suggested that charged sites on the phosphate group and its electrostatic pairing with the neighboring charged residues were physical origins of the phosphorylation effect. To verify this charge-pairing mechanism, we conducted experiments using a series of PHF6 derivatives with non-native charge distributions. The electrostatic interaction in an intermolecular mode was also demonstrated by the system composed of two different peptide species, which found that fibrillation of nonphosphorylated PHF6 was drastically enhanced when a trace amount of phosphorylated PHF6 molecules coexisted. A simulation analysis utilizing crystal coordinates of the PHF6 fibril was also performed for interpreting the experimental results in a molecular level. The present study using the model peptide system gave us a microscopically insightful view on the roles of tau phosphorylation in amyloid-related diseases.