Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan.
Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan.
RNA. 2024 Oct 16;30(11):1422-1436. doi: 10.1261/rna.080165.124.
Many RNA-binding proteins (RBPs) contain low-complexity domains (LCDs) with prion-like compositions. These long intrinsically disordered regions regulate their solubility, contributing to their physiological roles in RNA processing and organization. However, this also makes these RBPs prone to pathological misfolding and aggregation that are characteristic of neurodegenerative diseases. For example, TAR DNA-binding protein 43 (TDP-43) forms pathological aggregates associated with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). While molecular chaperones are well-known suppressors of these aberrant events, we recently reported that highly disordered, hydrophilic, and charged heat-resistant obscure (Hero) proteins may have similar effects. Specifically, Hero proteins can maintain the activity of other proteins from denaturing conditions in vitro, while their overexpression can suppress cellular aggregation and toxicity associated with aggregation-prone proteins. However, it is unclear how these protective effects are achieved. Here, we used single-molecule FRET to monitor the conformations of the aggregation-prone prion-like LCD of TDP-43. While we observed high conformational heterogeneity in wild-type LCD, the ALS-associated mutation A315T promoted collapsed conformations. In contrast, an Hsp40 chaperone, DNAJA2, and a Hero protein, Hero11, stabilized extended states of the LCD, consistent with their ability to suppress the aggregation of TDP-43. Our results link single-molecule effects on conformation to macro effects on bulk aggregation, where a Hero protein, like a chaperone, can maintain the conformational integrity of a client protein to prevent its aggregation.
许多 RNA 结合蛋白 (RBP) 含有具有类朊病毒组成的低复杂度结构域 (LCD)。这些长的固有无序区域调节它们的溶解度，有助于它们在 RNA 加工和组织中的生理作用。然而，这也使这些 RBP 容易发生病理性错误折叠和聚集，这是神经退行性疾病的特征。例如，TAR DNA 结合蛋白 43 (TDP-43) 形成与肌萎缩侧索硬化症 (ALS) 和额颞叶变性 (FTLD) 相关的病理性聚集物。虽然分子伴侣是这些异常事件的众所周知的抑制剂，但我们最近报道，高度无序、亲水和带电荷的耐热性模糊 (Hero) 蛋白可能具有类似的作用。具体来说，Hero 蛋白可以在体外保持其他蛋白质的活性，使其免受变性条件的影响，而它们的过表达可以抑制与聚集倾向蛋白相关的细胞聚集和毒性。然而，这些保护作用是如何实现的尚不清楚。在这里，我们使用单分子 FRET 监测 TDP-43 易聚集的类朊病毒 LCD 的构象。虽然我们观察到野生型 LCD 中存在高度构象异质性，但 ALS 相关突变 A315T 促进了塌陷构象。相比之下，Hsp40 伴侣蛋白 DNAJA2 和 Hero 蛋白 Hero11 稳定了 LCD 的扩展状态，与它们抑制 TDP-43 聚集的能力一致。我们的结果将单分子对构象的影响与对总体聚集的宏观影响联系起来，其中 Hero 蛋白（如伴侣蛋白）可以维持客户蛋白的构象完整性，防止其聚集。
