Aim: The demonstration that chaperone-mediated autophagy (CMA) contributes to the degradation of TDP-43, the main constituent of cytoplasmic inclusions typically found in motor neurons of patients with sporadic amyotrophic lateral sclerosis (sALS), has pointed out a possible involvement of CMA in aggregate formation. To explore this possibility, in this study, we verified the presence of a possible systemic CMA alteration in sALS patients and its effect on TDP-43 expression. Materials and methods: Gene and protein expression of the cytosolic chaperone HSC70 and the lysosome receptor LAMP2A, the two pivotal mediators of CMA, was assessed in peripheral blood mononuclear cells (PBMCs) derived from 30 sALS patients and 30 healthy controls. The expression of TDP-43 and co-chaperones BAG1 and BAG3 was also analyzed. Results: We found reduced HSC70 expression in patient cells, with no change in LAMP2A, and increased insoluble TDP-43 protein levels, with an aberrant intracellular localization. We also observed an unbalanced expression of co-chaperones BAG1 and BAG3. HSC70 down-regulation was confirmed in immortalized lymphoblastoid cell lines derived from sporadic and TARDBP mutant ALS patients. Lastly, we demonstrated that HSC70 silencing directly increases TDP-43 protein levels in human neuroblastoma cells. Discussion: Our results do not support the existence of a systemic CMA alteration in sALS patients but indicate a direct involvement of HSC70 alterations in ALS pathogenesis.

中文翻译：

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HSC70表达在散发性ALS患者的淋巴细胞中减少，并有助于TDP-43的积累。

目的：证明伴侣介导的自噬（CMA）有助于TDP-43的降解，TDP-43是散发性肌萎缩性侧索硬化症（sALS）患者运动神经元中常见的细胞质内含物的主要成分，已指出可能参与CMA形成聚集体。为了探索这种可能性，在这项研究中，我们验证了sALS患者中可能的全身性CMA改变的存在及其对TDP-43表达的影响。材料和方法：在30例sALS患者和30例健康对照者的外周血单个核细胞（PBMC）中评估了CMA的两个关键介体细胞溶质伴侣HSC70和溶酶体受体LAMP2A的基因和蛋白质表达。还分析了TDP-43和伴侣蛋白BAG1和BAG3的表达。结果：我们发现患者细胞中HSC70的表达降低，而LAMP2A却没有变化，并且不溶性TDP-43蛋白水平升高，细胞内定位异常。我们还观察到伴侣分子BAG1和BAG3的不平衡表达。在散发和TARDBP突变ALS患者的永生化淋巴母细胞系中证实了HSC70的下调。最后，我们证明了HSC70沉默可直接增加人神经母细胞瘤细胞中的TDP-43蛋白水平。讨论：我们的结果不支持sALS患者存在全身性CMA改变，但表明HSC70改变直接参与ALS发病机制。我们还观察到伴侣分子BAG1和BAG3的不平衡表达。在散发和TARDBP突变ALS患者的永生化淋巴母细胞系中证实了HSC70的下调。最后，我们证明了HSC70沉默可直接增加人神经母细胞瘤细胞中的TDP-43蛋白水平。讨论：我们的结果不支持sALS患者存在全身性CMA改变，但表明HSC70改变直接参与ALS发病机制。我们还观察到伴侣分子BAG1和BAG3的不平衡表达。在散发和TARDBP突变ALS患者的永生化淋巴母细胞系中证实了HSC70的下调。最后，我们证明了HSC70沉默可直接增加人神经母细胞瘤细胞中的TDP-43蛋白水平。讨论：我们的结果不支持sALS患者存在全身性CMA改变，但表明HSC70改变直接参与ALS发病机制。