Abstract：
Pathogenic mutations of transactivation response element DNA-binding protein 43 (TDP-43) are closely linked with amyotrophic lateral sclerosis (ALS). It was recently reported that two ALS-linked familial mutants A315T and A315E of TDP-43307-319 peptides can self-assemble into oligomers including tetramers, hexamers, and octamers, among which hexamers were suggested to form the β-barrel structure. However, due to the transient nature of oligomers, their conformational properties and the atomic mechanisms underlying the β-barrel formation remain largely elusive. Herein, we investigated the hexameric conformational distributions of the wild-type (WT) TDP-43307-319 fragment and its A315T and A315E mutants by performing all-atom explicit-solvent replica exchange with solute tempering 2 simulations. Our simulations reveal that each peptide can self-assemble into diverse conformations including ordered β-barrels, bilayer β-sheets and/or monolayer β-sheets, and disordered complexes. A315T and A315E mutants display higher propensity to form β-barrel structures than the WT, which provides atomic explanation for their enhanced neurotoxicity reported previously. Detailed interaction analysis shows that A315T and A315E mutations increase inter-molecular interactions. Also, the β-barrel structures formed by the three different peptides are stabilized by distinct inter-peptide side-chain hydrogen bonding, hydrophobic, and aromatic stacking interactions. This study demonstrates the enhanced β-barrel formation of the TDP-43307-319 hexamer by the pathogenic A315T and A315E mutations and reveals the underlying molecular determinants, which may be helpful for in-depth understanding of the ALS-mutation-induced neurotoxicity of TDP-43 protein.
摘要：
反式激活反应元件DNA结合蛋白43（TDP-43）的致病突变与肌萎缩侧索硬化症（ALS）密切相关。最近有报道称，TDP-43307-319肽的两个ALS相关家族突变体A315T和A315E可以自组装成包括四聚体在内的寡聚体，hexamers,和八位字节，其中六聚体被建议形成β-桶结构。然而,由于低聚物的短暂性,它们的构象特性和β桶形成背后的原子机制在很大程度上仍然难以捉摸。在这里，我们通过使用溶质回火2模拟进行全原子显式溶剂副本交换，研究了野生型（WT）TDP-43307-319片段及其A315T和A315E突变体的六聚体构象分布。我们的模拟表明，每种肽都可以自组装成不同的构象，包括有序的β-桶，双层β-折叠和/或单层β-折叠，和无序的复合体。A315T和A315E突变体显示出比WT更高的形成β-桶结构的倾向，这为先前报道的它们增强的神经毒性提供了原子解释。详细的相互作用分析显示A315T和A315E突变增加分子间相互作用。此外，由三种不同的肽形成的β-桶结构通过不同的肽间侧链氢键稳定，疏水，和芳香堆积相互作用。这项研究证明了致病性A315T和A315E突变增强了TDP-43307-319六聚体的β桶形成，并揭示了潜在的分子决定因素，这可能有助于深入了解ALS突变引起的TDP-43蛋白的神经毒性。
