Peroxisome proliferator-activated receptor-γ (PPARγ) is a nuclear hormone receptor that is a master regulator of adipocyte differentiation and function. ZBTB9 is a widely expressed but poorly studied transcription factor that was predicted to interact with PPARγ based on large-scale protein-protein interaction experiments. In addition, genome-wide association studies (GWAS) revealed associations between ZBTB9 and BMI, T2D risk, and HbA1c levels. Here we show that Zbtb9 deficiency in mature adipocytes decreased PPARγ activity and protein level, and thus acts as a positive regulator of PPARγ signaling. In contrast, Zbtb9 deficiency in 3T3-L1 and human preadipocytes increased PPARγ levels and enhanced adipogenesis. Transcriptomic and transcription factor binding site analyses of Zbtb9 deficient preadipocytes revealed that the E2F pathway, controlled by the E2F family of transcription factors that are classically associated with cell cycle regulation, was among the most upregulated pathways. E2F1 positively regulates adipogenesis by promoting Pparg expression, independent of its cell cycle role, via direct binding to the Pparg promoter early during adipogenesis. RB phosphorylation (pRB), which regulates E2F activity, was also upregulated in Zbtb9 deficient preadipocytes. Critically, an E2F1 inhibitor blocked the effects of Zbtb9 deficiency on adipogenesis. Collectively, these results demonstrate that Zbtb9 inhibits adipogenesis as a negative regulator of Pparg expression via pRB-E2F signaling. Our findings reveal cell-state dependent roles of ZBTB9 in adipocytes, identifying a new molecule that regulates adipocyte biology as both a positive and negative regulator of PPARγ signaling depending on the cellular context, and thus may be important in the pathogenesis of obesity and T2D.

中文翻译：

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脂肪细胞中转录因子 ZBTB9 对 PPARγ 信号传导的细胞状态依赖性调节。


过氧化物酶体增殖物激活受体γ （PPARγ） 是一种核激素受体，是脂肪细胞分化和功能的主要调节因子。ZBTB9 是一种广泛表达但研究较少的转录因子，根据大规模蛋白质-蛋白质相互作用实验预测它与 PPARγ 相互作用。此外，全基因组关联研究 （GWAS） 揭示了 ZBTB9 与 BMI 、 T2D 风险和 HbA1c 水平之间的关联。在这里，我们表明成熟脂肪细胞中的 Zbtb9 缺陷降低了 PPARγ 活性和蛋白质水平，因此充当 PPARγ 信号传导的正调节因子。相比之下，3T3-L1 和人前脂肪细胞中的 Zbtb9 缺陷增加了 PPARγ 水平并增强了脂肪生成。Zbtb9 缺陷前脂肪细胞的转录组学和转录因子结合位点分析显示，由经典与细胞周期调节相关的转录因子 E2F 家族控制的 E2F 通路是上调最严重的通路之一。E2F1 通过在脂肪生成早期直接与 Pparg 启动子结合，促进 Pparg 表达，独立于其细胞周期作用，从而正向调节脂肪生成。调节 E2F 活性的 RB 磷酸化 （pRB） 在 Zbtb9 缺陷的前脂肪细胞中也上调。至关重要的是，E2F1 抑制剂阻断了 Zbtb9 缺陷对脂肪生成的影响。总的来说，这些结果表明 Zbtb9 通过 pRB-E2F 信号传导抑制脂肪生成作为 Pparg 表达的负调节因子。 我们的研究结果揭示了 ZBTB9 在脂肪细胞中的细胞状态依赖性作用，确定了一种调节脂肪细胞生物学的新分子，根据细胞环境作为 PPARγ 信号传导的正负调节因子，因此可能在肥胖和 T2D 的发病机制中很重要。