TDP-43的核耗竭导致神经元突触丢失

Depletion of nuclear TDP-43 contributes to synaptic loss in the hippocampal neurons of rat brain

目的:TDP-43异常可能是包括阿尔茨海默病(Alzheimer's disease,AD)在内的很多神经变性疾病的致病原因,但是其致病机制不明。一个核心问题就是TDP-43异常导致的神经毒性来自于其在胞质内的异常聚集还是其在细胞核内的缺失。通过探究TDP-43异常导致突触退化的机制入手,分析了多种TDP-43截短型突变体的亚细胞定位以及细胞核内TDP-43缺失与树突棘异常之间的关系。方法:构建TDP-43功能域截短突变,分析其在细胞系胞质内的聚集情况、对内源性TDP-43的影响、对体外培养大鼠海马体神经元树突棘密度的影响,并探究回补核内TDP-43是否能够阻止TDP-43异常所导致的树突棘丢失。其中树突棘用于表征突触。结果:在HEK 293T中,TDP-43的ΔNLSΔR2突变表征可模拟TDP-43的病理异常,包括形成ThS阳性、高度磷酸化的胞质聚集,并且诱导内源TDP-43在细胞核内的缺失。ΔNLSΔR2在海马脑切片中可以显著降低CA1神经元的树突棘密度。这种树突棘密度降低可以被定位于细胞核内的TDP-43突变(NLS-TDP-43)所抑制。结论:TDP-43的ΔNLSΔR2突变可以模拟TDP-43的病理异常并降低CA1神经元的树突棘密度。补偿TDP-43的核耗竭可以部分阻止ΔNLSΔR2导致的树突棘减少,说明内源性TDP-43的核耗竭是此类树突棘丢失的部分原因。

Objective:TDP-43 pathology is featured in many neurodegenerative diseases,including Alzheimer's disease(AD).Its contribution to these diseases remains unclear.One fundamental question is whether the neurotoxic effects from TDP-43 abnormalities result from its abnormal aggregation in the cytoplasm or its deficiency in the nucleus.To address this question,we investigated the mechanisms underlying TDP-43 abnormality-induced synaptic loss by analyzing how TDP-43 mutants contribute to spine abnormalities.Methods:Truncated mutants of TDP-43 were analyzed for their aggregation,effects on endogenous TDP-43,effects on dendritic spine density in cultured rat hippocampal neurons,and whether nuclear TDP-43 replenishment could prevent spine loss induced by TDP-43 abnormalities.Results:TheΔNLSΔR2 mutation of TDP-43 could mimic pathological abnormalities of TDP-43,including the formation of ThS-positive,highly phosphorylated cytoplasmic aggregates,and induction of nuclear depletion of endogenous TDP-43 in HEK 293T cells.ΔNLSΔR2 significantly reduces dendritic spine density of CA1 neurons in rat hippocampal slice cultures.This reduction in dendritic spine density can be partially blocked by co-expression of nuclear-localized TDP-43 mutant(NLS-TDP-43).Conclusion:TheΔNLSΔR2 mutation of TDP-43 recapitulates pathological abnormalities of TDP-43 and reduces dendritic spine density of CA1 neurons.Compensation for nuclear depletion of TDP-43 partially blocks the decrease in dendritic spines caused byΔNLSΔR2,indicating that nuclear depletion of endogenous TDP-43 is a partial cause of spine loss induced by TDP-43 pathology.