Xu Xuan, Charrier Alyssa, Congrove Sunny, Ockunzzi Jeremiah, Buchner David A
Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
J Biol Chem. 2024 Dec;300(12):107985. doi: 10.1016/j.jbc.2024.107985. Epub 2024 Nov 13.
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.
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，基于大规模蛋白质-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与体重指数（BMI）、2型糖尿病风险和糖化血红蛋白（HbA1c）水平之间的关联。在此我们表明，成熟脂肪细胞中Zbtb9的缺失降低了PPARγ活性和蛋白水平，因此作为PPARγ信号的正调节因子发挥作用。相反，3T3-L1和人前脂肪细胞中Zbtb9的缺失增加了PPARγ水平并增强了脂肪生成。对Zbtb9缺陷前脂肪细胞的转录组学和转录因子结合位点分析表明，由经典地与细胞周期调控相关的E2F转录因子家族控制的E2F途径是上调最明显的途径之一。E2F1通过在脂肪生成早期直接结合Pparg启动子来促进Pparg表达，从而独立于其细胞周期作用而正向调节脂肪生成。调节E2F活性的RB磷酸化（pRB）在Zbtb9缺陷前脂肪细胞中也上调。至关重要的是，一种E2F1抑制剂阻断了Zbtb9缺陷对脂肪生成的影响。总体而言，这些结果表明，Zbtb9通过pRB-E2F信号作为Pparg表达的负调节因子抑制脂肪生成。我们的发现揭示了ZBTB9在脂肪细胞中的细胞状态依赖性作用，确定了一种新分子，它根据细胞环境作为PPARγ信号的正负调节因子来调节脂肪细胞生物学，因此可能在肥胖症和2型糖尿病的发病机制中起重要作用。
