Study of regionally different pathomechanism in TDP-43-positive inclusions of amyotrophic lateral sclerosis

散发性肌萎缩侧索硬化症(SALS)患者下运动神经元中TDP-43阳性包涵体的SMurf2和pSmad2/3免疫阳性。而散发性肌萎缩侧索硬化症(SALS)患者脑内运动神经元外TDP-43阳性包涵体的SMurf2和pSmad2/3明显阴性。这些结果表明，TDP-43包涵体的组成具有区域性差异，提示不同的发病机制。我们通过将TDP-43的核定位信号缺失突变体导入HEK293T细胞并抑制蛋白酶体的活性，在HEK293T细胞中复制了TDP-43的胞质聚集体。过表达Smad2可减少HEK293T细胞内胞质聚集体的数量，而转化生长因子β刺激可剂量依赖性地增强这种减少作用。我们的结果提示，激活转化生长因子β/Smad信号系统可能是延缓ALS进展的一种潜在的治疗途径。

TDP-43-positive inclusions in lower motor neurones of sporadic Amyotrophic lateral sclerosis (SALS) patients were immunopositive for Smurf2 and pSmad2/3. In contrast, TDP-43-positive inclusions in the extramotor neurones in the brain of SALS patients were noticeably negative for Smurf2 and pSmad2/3. These results demonstrated that the composition of the TDP-43 inclusions is regionally distinct, suggesting different underlying pathogenic processes. We replicated cytoplasmic aggregates of TDP-43 in HEK293T cells by transfecting the cells with a nuclear localization signal deletion mutant of TDP-43 and inhibiting proteasome activity. Overexpression of Smad2 reduced the amount of cytoplasmic aggregates in HEK293T cells, and TGF beta stimulation augmented this reduction effect in a dose-dependent manner. Our results suggest that activation of TGF beta/Smad signaling system may be a potential therapeutic approach to delay the progression of ALS.