探討TAOK1在SH-SY5Y神經母細胞中的神經毒性及神經炎症效應

Abstract

神經退行性疾病 (Neurodegenerative Diseases)，如阿爾茨海默症（Alzheimer’s Disease）和帕金森病（Parkinson’s Disease），其特徵是神經元和突觸的喪失，通常由於異常蛋白質沉積和神經炎症引起。TAOK1（一種絲氨酸/蘇氨酸激酶）被確定為AD和PD患者認知障礙的生物標誌物，並在血漿來源的細胞外囊泡中積累。TAOK1已知會促進細胞死亡、病理性tau蛋白磷酸化，進而調節微管動態。儘管TAOK1在許多研究中與神經發育障礙有關，但其在神經退行性疾病中的作用較少研究。在初步研究中，TAOK1過度表達會降低細胞活力和ATP產量，增加tau蛋白磷酸化，並增加可轉座元件（Transposable Elements）的活動性。為了更好地研究TAOK1在通過tau蛋白誘導的微管失調和TE釋放的神經毒性後果中的作用，我們在人的神經母細胞瘤SH-SY5Y細胞中建立了一個可誘導的TAOK1過度表達細胞株。在本研究中，我們證明了TAOK1過度表達促進了tau蛋白的過度磷酸化，可能導致微管的不穩定。這表現為在神經分化過程中無法維持神經突起的生長。還觀察到了與突觸和微管相關基因表達的補償性變化。神經突起的喪失，加上細胞凋亡的增加，表明TAOK1過度表達與神經毒性有關。進一步分析發現，TAOK1過度表達的細胞在儘管抗氧化基因上調的情況持續顯示出活性氧水平的升高，，這表明氧化壓力是促使炎症反應的驅動因素。還發現內質網應激反應通路基因上調，暗示TAOK1介導的tau蛋白過度磷酸化在病理性蛋白質聚集中的作用。此外，TAOK1過度表達上調了幾個TE家族。隨著STING和TBK1表達的增加，數據表明細胞質雙鏈DNA的檢測增加，並可能通過I型干擾素通路激活炎症(IFN-I)反應，表明TE釋放的神經毒性後果。總體而言，這些發現闡明了TAOK1過度表達如何引起神經毒性並促進促炎機制，可能促進神經退行性疾病的進展。

Neurodegenerative diseases (NDs) like Alzheimer’s (AD) and Parkinson’s (PD) are characterised by neuron and synapse loss, often due to abnormal protein deposition and neuroinflammation. TAOK1, a serine/threonine kinase, was identified as a biomarker for cognitive impairment in AD and PD, accumulating in plasma-derived extracellular vesicles. TAOK1 is known to contribute to cell death, pathological tau phosphorylation, and by extension, regulation of microtubule dynamics. While TAOK1 has been implicated in neurodevelopmental disorders in many studies, its role in neurodegeneration is less studied. In preliminary studies, TAOK1 overexpression reduces cell viability and ATP production, increases phosphorylated Tau, and transposable elements (TEs) derepression. To better investigate TAOK1’s role in inducing neurotoxicity, therefore promoting neuron and functional loss, we established an inducible TAOK1-overexpressing cell line in human neuroblastoma SH-SY5Y cells. In this study, we have demonstrated that TAOK1 overexpression increases phosphorylated Tau, potentially leading to the destabilisation of microtubules. This was evidenced by inability to maintain neurite outgrowths during neuronal differentiation accompanied by changes in expression of synapse and microtubule-associated genes. Neurite loss, coupled with increased apoptosis, indicates neurotoxic effects linked to TAOK1 overexpression. TAOK1-overexpressing cells also exhibited elevated reactive oxygen species coupled with downregulation of mitochondria protein-coding genes, suggesting mitochondrial dysfunction as a driver of oxidative stress and neurotoxicity. Upregulation of endoplasmic reticulum stress response pathway genes was also discovered, implicating TAOK1-mediated tau hyperphosphorylation in pathological protein aggregation as a source of cellular stress. Additionally, TAOK1 overexpression upregulated several TE families. With increased STING and TBK1 expression, a heightened detection of cytosolic dsDNA and potential activation of inflammatory responses via class I Interferon pathways may be occurring as potential neurotoxic consequences of TE de-repression. Collectively, these findings elucidate how TAOK1 overexpression induces neurotoxicity and promotes pro-inflammatory mechanisms, contributing to the progression of neurodegenerative diseases.