Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany.
Institute for Clinical & Experimental Surgery, Saarland University, Homburg, Germany.
Sci Rep. 2017 Nov 27;7(1):16367. doi: 10.1038/s41598-017-16590-0.
Glucose homeostasis is regulated by insulin, which is produced in the β-cells of the pancreas. The synthesis of insulin is controlled by several transcription factors including PDX-1, USF1 and USF2. Both, PDX-1 and USF1 were identified as substrates for protein kinase CK2. Here, we have analysed the interplay of PDX-1, USF1 and CK2 in the regulation of PDX-1 gene transcription. We found that the PDX-1 promoter is dose-dependently transactivated by PDX-1 and transrepressed by USF1. With increasing glucose concentrations the transrepression of the PDX-1 promoter by USF1 is successively abrogated. PDX-1 binding to its own promoter was not influenced by glucose, whereas USF1 binding to the PDX-1 promoter was reduced. The same effect was observed after inhibition of the protein kinase activity by three different inhibitors or by using a phospho-mutant of USF1. Moreover, phosphorylation of USF1 by CK2 seems to strengthen the interaction between USF1 and PDX-1. Thus, CK2 is a negative regulator of the USF1-dependent PDX-1 transcription. Moreover, upon inhibition of CK2 in primary islets, insulin expression as well as insulin secretion were enhanced without affecting the viability of the cells. Therefore, inhibition of CK2 activity may be a promising approach to stimulate insulin production in pancreatic β-cells.
葡萄糖稳态受胰岛素调节，胰岛素由胰腺的β细胞产生。胰岛素的合成受多种转录因子控制，包括 PDX-1、USF1 和 USF2。PDX-1 和 USF1 都被鉴定为蛋白激酶 CK2 的底物。在这里，我们分析了 PDX-1、USF1 和 CK2 在 PDX-1 基因转录调控中的相互作用。我们发现 PDX-1 启动子被 PDX-1 剂量依赖性地转录激活，并被 USF1 转录抑制。随着葡萄糖浓度的增加，USF1 对 PDX-1 启动子的转录抑制逐渐被消除。PDX-1 与自身启动子的结合不受葡萄糖影响，而 USF1 与 PDX-1 启动子的结合减少。用三种不同的抑制剂或用 USF1 的磷酸突变体抑制蛋白激酶活性后，也观察到相同的效果。此外，CK2 似乎通过磷酸化 USF1 来增强 USF1 和 PDX-1 之间的相互作用。因此，CK2 是 USF1 依赖性 PDX-1 转录的负调节剂。此外，在原代胰岛中抑制 CK2 后，胰岛素表达和胰岛素分泌增强，而不影响细胞活力。因此，抑制 CK2 活性可能是刺激胰腺β细胞胰岛素产生的一种有前途的方法。
