Heteromeric amyloid filaments of ANXA11 and TDP-43 in FTLD-TDP type C

Affiliations

• MRC Laboratory of Molecular Biology, Cambridge, UK.
• Department of Brain and Neurosciences, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
• Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.
• Department of Psychiatry, National Hospital Organization Shimofusa Psychiatric Center, Chiba, Japan.
• Department of Neuropathology, Tokyo Metropolitan Institute for Geriatrics and Gerontology, Tokyo, Japan.
• Mesulam Center for Cognitive Neurology and Alzheimer's Disease, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
• MRC Laboratory of Molecular Biology, Cambridge, UK. bfalcon@mrc-lmb.cam.ac.uk.

PMID:  39260416IF: 50.5 Q1 B1  DOI: 10.1038/s41586-024-08024-5IF: 50.5 Q1 B1

Abstract

Neurodegenerative diseases are characterized by the abnormal filamentous assembly of specific proteins in the central nervous system. Human genetic studies have established a causal role for protein assembly in neurodegeneration. However, the underlying molecular mechanisms remain largely unknown, which is limiting progress in developing clinical tools for these diseases. Recent advances in cryo-electron microscopy have enabled the structures of the protein filaments to be determined from the brains of patients. All neurodegenerative diseases studied to date have been characterized by the self-assembly of proteins in homomeric amyloid filaments, including that of TAR DNA-binding protein 43 (TDP-43) in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP) types A and B. Here we used cryo-electron microscopy to determine filament structures from the brains of individuals with FTLD-TDP type C, one of the most common forms of sporadic FTLD-TDP. Unexpectedly, the structures revealed that a second protein, annexin A11 (ANXA11), co-assembles with TDP-43 in heteromeric amyloid filaments. The ordered filament fold is formed by TDP-43 residues G282/G284–N345 and ANXA11 residues L39–Y74 from their respective low-complexity domains. Regions of TDP-43 and ANXA11 that were previously implicated in protein–protein interactions form an extensive hydrophobic interface at the centre of the filament fold. Immunoblots of the filaments revealed that the majority of ANXA11 exists as an approximately 22 kDa N-terminal fragment lacking the annexin core domain. Immunohistochemistry of brain sections showed the colocalization of ANXA11 and TDP-43 in inclusions, redefining the histopathology of FTLD-TDP type C. This work establishes a central role for ANXA11 in FTLD-TDP type C. The unprecedented formation of heteromeric amyloid filaments in the human brain revises our understanding of amyloid assembly and may be of significance for the pathogenesis of neurodegenerative diseases.

神经退行性疾病的一个重要特征是中枢神经系统中特定蛋白质的异常丝状聚集。通过人类基因研究，科学家已经确认了蛋白质聚集在神经退行性疾病中的因果关系。然而，具体的分子机制仍然不清楚，严重制约了针对这些疾病的临床治疗工具的开发。近年来，随着冷冻电子显微镜技术的进步，研究人员得以从患者的大脑中直接观察和确定蛋白质丝的结构。研究表明，所有已知的神经退行性疾病都表现出蛋白质自发组装成同源的淀粉样蛋白丝的特点，例如肌萎缩侧索硬化症（ALS）和伴有 TDP-43 包涵体的前颞叶变性（FTLD-TDP）A型和B型。在本文中，我们利用冷冻电子显微镜技术，首次解析了来自 FTLD-TDP C 型患者大脑中的丝状结构。FTLD-TDP C 型是最常见的散发性 FTLD-TDP 形式之一。令人意外的是，研究发现这些丝状结构揭示了另一种蛋白质 ANXA11 与 TDP-43 共同组装形成了异构的淀粉样蛋白丝。在这些丝状结构中，TDP-43 的 G282/G284-N345 片段和 ANXA11 的 L39-Y74 片段从各自的低复杂性结构域中形成了有序的折叠。TDP-43 和 ANXA11 的一些区域此前已被认为与蛋白质相互作用有关，这些区域在丝状折叠的中心形成了一个广泛的疏水界面。通过丝状物的免疫印迹，研究显示 ANXA11 主要以大约 22 kDa 的 N 端片段形式存在，该片段缺乏附着蛋白的核心结构域。此外，脑切片的免疫组化分析表明，ANXA11 和 TDP-43 在神经包涵体中共同定位，重新定义了 FTLD-TDP C 型的组织病理特征。