Atwal Manpreet Singh, Nimac Jerneja, Čerček Urša, Goesch Sarah Ricarda, Goesch Hannah Rebecca, Tziortzouda Paraskevi, Ercolani Tiziana, Zatorska Anna, Pasha Terouz, Carre Ivo, Mitchell Jacqueline, Troakes Claire, Tummers Bart, Župunski Vera, Rogelj Boris, Hortobágyi Tibor, Hirth Frank
Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom.
Department of Biotechnology, Jozef Stefan Institute, Ljubljana, Slovenia.
Front Neurosci. 2025 Jul 23;19:1558227. doi: 10.3389/fnins.2025.1558227. eCollection 2025.
Cytoplasmic mislocalisation and nuclear depletion of TDP-43 are pathological hallmarks of amyotrophic lateral sclerosis (ALS), including mutations in the gene that characterise the most common genetic form of ALS (C9ALS). Studies in human cells and animal models have associated cytoplasmic mislocalisation of TDP-43 with abnormalities in nuclear transport receptors, referred to as karyopherins, that mediate the nucleocytoplasmic shuttling of TDP-43. Yet the relationship between karyopherin abnormalities and TDP-43 pathology are unclear. Here we report karyopherin-α4 (KPNA4) pathology in the spinal cord of TDP-43-positive sporadic ALS and C9ALS patients. Structural analyses revealed the selective interaction between KPNA subtypes, especially KPNA4, with the nuclear localisation signal (NLS) of TDP-43. Targeted cytoplasmic mislocalisation and nuclear depletion of TDP-43 caused KPNA4 pathology in human cells. Similar phenotypes were observed in whereby cytoplasmic accumulation of the TDP-43 homolog, TBPH, caused the nuclear decrease and cytosolic mislocalisation of the KPNA4 homolog, Importin-α3 (Impα3). In contrast, induced accumulation of Impα3 was not sufficient to cause TBPH mislocalisation. Instead, targeted gain of Impα3 in the presence of accumulating cytosolic TBPH, restored Impα3 localisation and partially rescued nuclear TBPH. These results demonstrate that cytoplasmic accumulation of TDP-43 causes karyopherin pathology that characterises ALS spinal cord. Together with earlier reports, our findings establish KPNA4 abnormalities as a molecular signature of TDP-43 proteinopathies and identify it as a potential therapeutic target to sustain nuclear TDP-43 essential for cellular homeostasis affected in ALS and frontotemporal dementia.
TDP - 43的细胞质错误定位和细胞核缺失是肌萎缩侧索硬化症（ALS）的病理特征，包括在最常见的遗传性ALS（C9ALS）基因中的突变。在人类细胞和动物模型中的研究表明，TDP - 43的细胞质错误定位与核转运受体（称为核转运蛋白）的异常有关，这些核转运蛋白介导TDP - 43的核质穿梭。然而，核转运蛋白异常与TDP - 43病理之间的关系尚不清楚。在这里，我们报告了TDP - 43阳性散发性ALS和C9ALS患者脊髓中的核转运蛋白α4（KPNA4）病理。结构分析揭示了KPNA亚型，特别是KPNA4与TDP - 43的核定位信号（NLS）之间的选择性相互作用。在人类细胞中，TDP - 43的靶向细胞质错误定位和细胞核缺失导致了KPNA4病理。在果蝇中也观察到了类似的表型，即TDP - 43同源物TBPH的细胞质积累导致了KPNA4同源物Importin - α3（Impα3）的细胞核减少和细胞质错误定位。相反，Impα3的诱导积累不足以导致TBPH错误定位。取而代之的是，在细胞质中积累的TBPH存在的情况下，靶向增加Impα3可恢复Impα3的定位并部分挽救细胞核中的TBPH。这些结果表明，TDP - 43的细胞质积累导致了以ALS脊髓为特征的核转运蛋白病理。与早期报告一起，我们的发现确定了KPNA4异常是TDP - 43蛋白病的分子特征，并将其鉴定为维持细胞核TDP - 43的潜在治疗靶点，而细胞核TDP - 43对于ALS和额颞叶痴呆中受影响的细胞内稳态至关重要。
