Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China.
Int J Mol Sci. 2023 Feb 13;24(4):3729. doi: 10.3390/ijms24043729.
Transthyretin (TTR) aggregation and amyloid formation are associated with several ATTR diseases, such as senile systemic amyloidosis (SSA) and familial amyloid polyneuropathy (FAP). However, the mechanism that triggers the initial pathologic aggregation process of TTR remains largely elusive. Lately, increasing evidence has suggested that many proteins associated with neurodegenerative diseases undergo liquid-liquid phase separation (LLPS) and subsequent liquid-to-solid phase transition before the formation of amyloid fibrils. Here, we demonstrate that electrostatic interactions mediate LLPS of TTR, followed by a liquid-solid phase transition, and eventually the formation of amyloid fibrils under a mildly acidic pH in vitro. Furthermore, pathogenic mutations (V30M, R34T, and K35T) of TTR and heparin promote the process of phase transition and facilitate the formation of fibrillar aggregates. In addition, S-cysteinylation, which is a kind of post-translational modification of TTR, reduces the kinetic stability of TTR and increases the propensity for aggregation, while another modification, S-sulfonation, stabilizes the TTR tetramer and reduces the aggregation rate. Once TTR was S-cysteinylated or S-sulfonated, they dramatically underwent the process of phase transition, providing a foundation for post-translational modifications that could modulate TTR LLPS in the context of pathological interactions. These novel findings reveal molecular insights into the mechanism of TTR from initial LLPS and subsequent liquid-to-solid phase transition to amyloid fibrils, providing a new dimension for ATTR therapy.
转甲状腺素蛋白（TTR）聚集和淀粉样形成与几种ATTR 疾病有关，如老年性系统性淀粉样变性（SSA）和家族性淀粉样多发性神经病（FAP）。然而，触发 TTR 初始病理聚集过程的机制在很大程度上仍不清楚。最近，越来越多的证据表明，许多与神经退行性疾病相关的蛋白质经历液-液相分离（LLPS），并在形成淀粉样纤维之前随后发生液-固相变。在这里，我们证明静电相互作用介导 TTR 的 LLPS，随后是液-固相变，最终在体外轻度酸性 pH 下形成淀粉样纤维。此外，TTR 的致病性突变（V30M、R34T 和 K35T）和肝素促进相变过程，并促进纤维状聚集体的形成。此外，TTR 的 S-半胱氨酸化，是 TTR 的一种翻译后修饰，降低了 TTR 的动力学稳定性并增加了聚集的倾向，而另一种修饰，S-硫酸化，稳定了 TTR 四聚体并降低了聚集速率。一旦 TTR 被 S-半胱氨酸化或 S-硫酸化，它们就会剧烈地经历相变过程，为翻译后修饰提供了基础，这些修饰可以调节 TTR 在病理相互作用背景下的 LLPS。这些新发现揭示了 TTR 从初始 LLPS 到随后的液-固相变到淀粉样纤维的机制的分子见解，为 ATTR 治疗提供了一个新的维度。
