Background

Emerging studies have shown that FAT atypical cadherin 1 (FAT1) and autophagy separately inhibits and promotes acute myeloid leukemia (AML) proliferation. However, it is unknown whether FAT1 were associated with autophagy in regulating AML proliferation.

Methods

AML cell lines, 6-week-old male nude mice and AML patient samples were used in this study. qPCR/Western blot and cell viability/³H-TdR incorporation assays were separately used to detect mRNA/protein levels and cell activity/proliferation. Luciferase reporter assay was used to examine gene promoter activity. Co-IP analysis was used to detect the binding of proteins.

Results

In this study, we for the first time demonstrated that FAT1 inhibited AML proliferation by decreasing AML autophagy level. Moreover, FAT1 weakened AML autophagy level via decreasing autophagy related 4B (ATG4B) expression. Mechanistically, we found that FAT1 reduced the phosphorylated and intranuclear SMAD family member 2/3 (smad2/3) protein levels, thus decreasing the activity of ATG4B gene promoter. Furthermore, we found that FAT1 competitively bound to TGF-βR II which decreased the binding of TGF-βR II to TGF-βR I and the subsequent phosphorylation of TGF-βR I, thus reducing the phosphorylation and intranuclear smad2/3. The experiments in nude mice showed that knockdown of FAT1 promoted AML autophagy and proliferation in vivo.

Conclusions

Collectively, these results revealed that FAT1 downregulates ATG4B expression via inhibiting TGFβ-smad2/3 signaling activity, thus decreasing the autophagy level and proliferation activity of AML cells.

General significance

Our study suggested that the “FAT1-TGFβ-smad2/3-ATG4B-autophagy” pathway may be a novel target for developing new targeted drugs to AML treatment.

中文翻译：

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FAT1通过下调ATG4B表达抑制AML自噬和增殖

背景

新兴研究表明，FAT 非典型钙粘蛋白 1 (FAT1) 和自噬分别抑制和促进急性髓系白血病 (AML) 增殖。然而，FAT1 是否与自噬调节 AML 增殖有关尚不清楚。

方法

本研究使用了 AML 细胞系、6 周龄雄性裸鼠和 AML 患者样本。分别使用qPCR/Western blot 和细胞活力/ ^{3 H-TdR 掺入测定来检测 mRNA/蛋白质水平和细胞活性/增殖。}荧光素酶报告基因测定用于检查基因启动子活性。Co-IP 分析用于检测蛋白质的结合。

结果

在本研究中，我们首次证明FAT1通过降低AML自噬水平来抑制AML增殖。此外，FAT1 通过减少自噬相关 4B (ATG4B) 的表达来削弱 AML 自噬水平。从机制上讲，我们发现FAT1降低了磷酸化和核内SMAD家族成员2/3（smad2/3）蛋白的水平，从而降低了ATG4B基因启动子的活性。此外，我们发现FAT1竞争性地与TGF-βR II结合，从而减少TGF-βR II与TGF-βR I的结合以及随后TGF-βR I的磷酸化，从而减少磷酸化和核内smad2/3。裸鼠实验表明，敲除FAT1可促进体内AML自噬和增殖。

结论

总的来说，这些结果表明FAT1通过抑制TGFβ-smad2/3信号活性下调ATG4B表达，从而降低AML细胞的自噬水平和增殖活性。

一般意义

我们的研究表明，“FAT1-TGFβ-smad2/3-ATG4B-自噬”通路可能是开发治疗 AML 的新靶向药物的新靶点。