Gadhavi Joshna, Shah Sumedha, Sinha Tulika, Jain Alok, Gupta Sharad
Department of Biological Engineering, Indian Institute of Technology Gandhinagar, India.
Department of Bioengineering and Biotechnology, Birla Institute of Technology, Ranchi, India.
FEBS J. 2022 May;289(9):2562-2577. doi: 10.1111/febs.16284. Epub 2021 Dec 2.
Tau protein is found abundantly in neurofibrillary tangles in Alzheimer's disease (AD). The longest human tau isoform (2N4R) has 44 lysine residues. Several lysine-based post-translational modifications (PTMs) such as glycation, acetylation, ubiquitination, and sumoylation have been implicated not only in AD, but also in other tauopathies. Carbamylation is one such lysine neutralizing age-related nonenzymatic PTM which can modulate the aggregation propensity of tau. In this work, we have studied the aggregation potential of lysine-rich regions of tau upon carbamylation which do not aggregate in their native form. Using an array of biophysical and microscopic analyses, such as ThT kinetic assay, fluorescence microscopy, Congo red staining, and scanning electron microscopy, we demonstrate that peptides derived from four of five such regions exhibit robust fibrillar amyloid formation. These regions are found in the N-terminal projection domain that encompasses proline-rich domain (148-153 and 223-230), repeat domain R1 (253-260), as well as fibrillary core region (368-378), and can be described as hidden aggregation hot-spots which become activated upon carbamylation. We have further compared the impact of carbamylation with acetylation on the aggregation propensity of lysine-rich peptide ( KKVAVV ) using biophysical experiments and molecular dynamics simulations and deduced that carbamylation is a much stronger driver of aggregation than acetylation. Our findings may offer more insight into amyloid fibrils' interaction with hidden aggregation-prone nucleating sequences that act as hot-spots for inducing tau fibrillation.
在阿尔茨海默病（AD）的神经原纤维缠结中大量发现tau蛋白。人类最长的tau异构体（2N4R）有44个赖氨酸残基。几种基于赖氨酸的翻译后修饰（PTM），如糖基化、乙酰化、泛素化和类泛素化，不仅与AD有关，也与其他tau蛋白病有关。氨甲酰化就是这样一种与年龄相关的非酶促赖氨酸中和PTM，它可以调节tau蛋白的聚集倾向。在这项研究中，我们研究了氨甲酰化后tau蛋白富含赖氨酸区域的聚集潜力，这些区域在天然状态下不会聚集。通过一系列生物物理和显微镜分析，如硫黄素T动力学测定、荧光显微镜、刚果红染色和扫描电子显微镜，我们证明了来自五个这样的区域中的四个区域的肽表现出强大的纤维状淀粉样蛋白形成。这些区域位于N端投射结构域，包括富含脯氨酸的结构域（148 - 153和223 - 230）、重复结构域R1（253 - 260）以及纤维状核心区域（368 - 378），可以被描述为隐藏的聚集热点，在氨甲酰化后被激活。我们进一步使用生物物理实验和分子动力学模拟比较了氨甲酰化和乙酰化对富含赖氨酸肽（KKVAVV）聚集倾向的影响，并推断氨甲酰化是比乙酰化更强的聚集驱动因素。我们的发现可能为淀粉样纤维与隐藏的易于聚集的成核序列之间的相互作用提供更多见解，这些序列是诱导tau蛋白纤维化的热点。
