Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA.
Central Arkansas Veterans Healthcare Service, McClellan Veterans Medical Center, Little Rock, AR, 72205, USA.
Sci Rep. 2023 Feb 6;13(1):2096. doi: 10.1038/s41598-023-28381-x.
Amyotrophic lateral sclerosis (ALS) is an inexorably progressive and degenerative disorder of motor neurons with no currently-known cure. Studies to determine the mechanism of neurotoxicity and the impact of ALS-linked mutations (SOD1, FUS, TARDP, C9ORF72, PFN1, TUBA4A and others) have greatly expanded our knowledge of ALS disease mechanisms and have helped to identify potential targets for ALS therapy. Cellular pathologies (e.g., aggregation of mutant forms of SOD1, TDP43, FUS, Ubiqulin2, PFN1, and C9ORF72), mitochondrial dysfunction, neuroinflammation, and oxidative damage are major pathways implicated in ALS. Nevertheless, the selective vulnerability of motor neurons remains unexplained. The importance of tubulins for long-axon infrastructure, and the special morphology and function of motor neurons, underscore the central role of the cytoskeleton. The recent linkage of mutations to the tubulin α chain, TUBA4A, to familial and sporadic cases of ALS provides a new investigative opportunity to shed light on both mechanisms of ALS and the vulnerability of motor neurons. In the current study we investigate TUBA4A, a structural microtubule protein with mutations causal to familial ALS, using molecular-dynamic (MD) modeling of protein structure to predict the effects of each mutation and its overall impact on GTP binding, chain stability, tubulin assembly, and aggregation propensity. These studies predict that each of the reported mutations will cause notable structural changes to the TUBA4A (α chain) tertiary protein structure, adversely affecting its physical properties and functions. Molecular docking and MD simulations indicate certain α chain mutations (e.g. K430N, R215C, and W407X) may cause structural deviations that impair GTP binding, and plausibly prevent or destabilize tubulin polymerization. Furthermore, several mutations (including R320C and K430N) confer a significant increase in predicted aggregation propensity of TUBA4A mutants relative to wild-type. Taken together, these in silico modeling studies predict structural perturbations and disruption of GTP binding, culminating in failure to form a stable tubulin heterocomplex, which may furnish an important pathogenic mechanism to trigger motor neuron degeneration in ALS.
肌萎缩侧索硬化症（ALS）是一种不可逆转的进行性和退行性运动神经元疾病，目前尚无已知的治愈方法。研究确定神经毒性的机制和 ALS 相关突变的影响（SOD1、FUS、TARDP、C9ORF72、PFN1、TUBA4A 等）极大地扩展了我们对 ALS 疾病机制的认识，并有助于确定 ALS 治疗的潜在靶点。细胞病理学（例如，突变型 SOD1、TDP43、FUS、Ubiqulin2、PFN1 和 C9ORF72 的聚集）、线粒体功能障碍、神经炎症和氧化损伤是与 ALS 相关的主要途径。然而，运动神经元的选择性易感性仍未得到解释。微管蛋白对长轴突基础设施的重要性，以及运动神经元的特殊形态和功能，突出了细胞骨架的核心作用。最近，突变与微管蛋白 α 链 TUBA4A 的关联，以及家族性和散发性 ALS 的关联，为阐明 ALS 的机制和运动神经元的易感性提供了新的研究机会。在本研究中，我们使用蛋白质结构的分子动力学（MD）建模来研究 TUBA4A，TUBA4A 是一种结构微管蛋白，其突变与家族性 ALS 有关，以预测每个突变及其对 GTP 结合、链稳定性、微管蛋白组装和聚集倾向的整体影响。这些研究预测，报告的每个突变都会导致 TUBA4A（α 链）三级蛋白质结构的显著结构变化，从而对其物理性质和功能产生不利影响。分子对接和 MD 模拟表明，某些 α 链突变（例如 K430N、R215C 和 W407X）可能导致结构偏差，从而阻碍 GTP 结合，并可能阻止或使微管蛋白聚合不稳定。此外，一些突变（包括 R320C 和 K430N）使 TUBA4A 突变体的预测聚集倾向相对于野生型显著增加。总之，这些计算机建模研究预测结构扰动和 GTP 结合的破坏，最终导致不稳定的微管蛋白异源复合物的形成失败，这可能为 ALS 中触发运动神经元退化提供一个重要的致病机制。
