The effect of G83R mutation on transthyretin protein structural stability

Transthyretin (TTR) G83R mutation can cause vitreous amyloidosis and severely impair vision. TTR variant aggregation and amyloid formation are known to be associated with ATTR amyloidosis. However, the mechanism underlying the pathological aggregation process of TTR G83R remains elusive. Further understanding of the effect of G83R mutation on TTR structure and stability will help to understand its pathogenesis. This study investigated thermodynamic and dynamic stability and fibril formation of TTR G83R and compared it with WT TTR and V30M variant. The results show that the quaternary and tertiary structural stability of TTR G83R is lower than WT TTR but significantly higher than TTR V30M. The fibril formation rate of TTR G83R under acidic conditions was between that of WT TTR and V30M variants. Molecular dynamics simulation suggested that G83R mutation mainly affected the stability of TTR tetramer, especially in an acidic environment. In summary, results from several different analyses in this study consistently demonstrate the thermodynamic and kinetic instability of G83R TTR in denaturant and acidic environments. The effect of G83R mutation on TTR stability is mainly tetramer dissociation, which may accelerate the aggregation of monomers to a certain extent. These results strongly suggest that the G83R mutation increases the amyloidosis potential inherent in TTR.

运甲状腺素蛋白（Transthyretin, TTR）G83R突变可引发玻璃体淀粉样变性并严重损害视力。TTR变体聚集与淀粉样蛋白形成已被证实与ATTR淀粉样变性（ATTR amyloidosis）相关，但TTR G83R病理性聚集过程背后的分子机制仍未明确。进一步阐明G83R突变对TTR结构与稳定性的影响，将有助于解析其致病机制。本研究针对TTR G83R的热力学稳定性、动态稳定性及原纤维形成能力展开探究，并将其与野生型TTR（WT TTR）及V30M变体进行对比。研究结果显示，TTR G83R的四级与三级结构稳定性低于野生型TTR，但显著高于TTR V30M变体。酸性条件下，TTR G83R的原纤维形成速率介于野生型TTR与V30M变体之间。分子动力学模拟（Molecular Dynamics Simulation）结果表明，G83R突变主要影响TTR四聚体的稳定性，尤其在酸性环境中。综上，本研究多项不同分析的结果一致证实，G83R突变型TTR在变性剂与酸性环境中存在热力学与动力学不稳定性。G83R突变对TTR稳定性的影响主要体现为四聚体解离，这在一定程度上可加速单体的聚集过程。上述结果有力表明，G83R突变增强了TTR固有的淀粉样变性潜能。