Autophagy is a cellular degradation process for the clearance of damaged or superfluous proteins and organelles, the recycling of which serves as an alternative energy source during periods of metabolic stress to maintain cell homeostasis and viability. The anti-necrotic function of autophagy is critical for tumorigenesis of many tumor cells, including hepatocellular carcinoma (HCC). However, the underlying mechanism is not clarified yet. Ammonium chloride (NH4Cl) is a well-known autophagy inhibitor, whereas its interaction with SMAD2 signaling pathway has not been reported previously. Here, we show that NH4Cl significantly inhibited rapamycin-induced autophagy in HCC cells through decreasing the levels of Beclin-1, autophagy-related protein 7 (ATG7), p62, and autophagosome marker LC3 and significantly decreased the level of phosphorylated SMAD2 in rapamycin-treated HCC cells. In order to find out whether NH4Cl may inhibit the autophagy in rapamycin-treated HCC cells through inhibition of SMAD2 signaling, we used transforming growth factor β1 (TGFβ1) to induce phosphorylation of SMAD2 in HCC cells. We found that induction of SMAD2 in HCC cells completely abolished the inhibitory effect of NH4Cl on rapamycin-induced autophagy in HCC cells, suggesting that NH4Cl inhibits autophagy of HCC cells through inhibiting SMAD2 signaling.

中文翻译：

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氯化铵通过 SMAD2 信号传导抑制肝细胞癌细胞的自噬。


自噬是一种细胞降解过程，用于清除受损或多余的蛋白质和细胞器，其回收在代谢应激期间可作为替代能源，以维持细胞稳态和活力。自噬的抗坏死功能对于许多肿瘤细胞的肿瘤发生至关重要，包括肝细胞癌（HCC）。然而，其根本机制尚不清楚。氯化铵 (NH4Cl) 是一种众所周知的自噬抑制剂，但其与 SMAD2 信号通路的相互作用尚未有报道。在这里，我们发现 NH4Cl 通过降低 Beclin-1、自噬相关蛋白 7 (ATG7)、p62 和自噬体标记物 LC3 的水平，显着抑制雷帕霉素诱导的 HCC 细胞自噬，并显着降低雷帕霉素中磷酸化 SMAD2 的水平。处理过的肝癌细胞。为了查明NH4Cl是否可能通过抑制SMAD2信号传导来抑制雷帕霉素处理的HCC细胞的自噬，我们使用转化生长因子β1（TGFβ1）诱导HCC细胞中SMAD2的磷酸化。我们发现HCC细胞中SMAD2的诱导完全消除了NH4Cl对雷帕霉素诱导的HCC细胞自噬的抑制作用，表明NH4Cl通过抑制SMAD2信号传导来抑制HCC细胞的自噬。