Burke Susan J, Collier J Jason, Scott Donald K
Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
FASEB J. 2009 Sep;23(9):2855-65. doi: 10.1096/fj.08-126631. Epub 2009 Apr 30.
Glucose-mediated activation of the L-type pyruvate kinase (L-PK) gene is repressed by cAMP, making this an excellent model for studying the mechanism by which these contrary signals regulate gene expression. Using the 832/13 rat insulinoma cell line, we demonstrate using RNA interference and chromatin immunoprecipitation that carbohydrate response element binding protein (ChREBP), hepatic nuclear factor 4alpha (HNF4alpha), and the coactivator CREB binding protein (CBP) are required for the glucose response of the L-PK gene and are recruited to the promoter by glucose. The cAMP agonist forskolin blocked the glucose-mediated induction of the L-PK gene in a PKA-dependent manner and blocked the recruitment of ChREBP, HNF4alpha, and CBP to the L-PK promoter, while simultaneously recruiting CBP to the cAMP-inducible gene, nuclear receptor subfamily 4, group A, member 2 (NR4A2). Overexpression of CBP, but not ChREBP, reversed the cAMP repression of the L-PK gene. In addition, CBP augmented the glucose response of the L-PK promoter. We conclude that cAMP and glucose signaling converge on a complex containing ChREBP, HNF4alpha, and CBP, and that cAMP acts by disrupting this transcriptional complex assembled by glucose-derived signals.
环磷酸腺苷（cAMP）可抑制葡萄糖介导的L型丙酮酸激酶（L-PK）基因激活，这使其成为研究这些相反信号调控基因表达机制的绝佳模型。利用832/13大鼠胰岛素瘤细胞系，我们通过RNA干扰和染色质免疫沉淀证明，碳水化合物反应元件结合蛋白（ChREBP）、肝细胞核因子4α（HNF4α）和共激活因子CREB结合蛋白（CBP）是L-PK基因葡萄糖反应所必需的，并且可被葡萄糖招募至启动子。cAMP激动剂福斯高林以依赖蛋白激酶A（PKA）的方式阻断葡萄糖介导的L-PK基因诱导，并阻断ChREBP、HNF4α和CBP向L-PK启动子的募集，同时将CBP招募至cAMP诱导基因核受体亚家族4 A组成员2（NR4A2）。过表达CBP而非ChREBP可逆转cAMP对L-PK基因的抑制。此外，CBP增强了L-PK启动子的葡萄糖反应。我们得出结论，cAMP和葡萄糖信号汇聚于一个包含ChREBP、HNF4α和CBP的复合物，并且cAMP通过破坏由葡萄糖衍生信号组装的转录复合物发挥作用。
