LncRNA Ctcflos modulates glucocorticoid receptor-mediated induction of hepatic phosphoenolpyruvate carboxykinase in mice

Phosphoenolpyruvate carboxykinase (Pck1) is a key enzyme that catalyzes an irreversible step of hepatic gluconeogenesis; however, the mechanism underlying Pck1 regulation is not fully understood. In the present study, we investigated the role of Ctcflos, a long non-coding RNA (lncRNA) located in the mouse Pck1 enhancer region, in the transcriptional regulation of the Pck1 gene. Rapid amplification of cDNA ends (RACE) was done to identify the precise structures of Ctcflos isotypes. We analyzed the DNA binding signals of GR, hnRNPL, and histone marks by ChIP-qPCR assays. We used the antisense oligonucleotide (ASO) for suppression of Ctcflos and adenovirus encoding Ctcflos was injected into mice via the tail vein to overexpress Ctcflos in the liver. We performed RNA pull-down assays to search for Ctcflos-binding proteins. We identified the precise structures of five different hepatic Ctcflos isotypes. The induction of Ctcflos was dependent on the glucocorticoid receptor (GR) in the livers of fasted or dexamethasone-administered mice. Overexpression of Ctcflos increased the expression of Pck1, whereas knockdown of Ctcflos suppressed the transcript and protein expression of Pck1. Ctcflos bound the heterogeneous ribonucleoprotein L (hnRNPL), which interacts with GR. Knockdown of hnRNPL upregulated the Pck1 gene. The interaction between Ctcflos and hnRNPL interfered the binding of GR to hnRNPL, which subsequently increased GR recruitment in the Pck1 enhancer region. Targeting Ctcflos may provide a new insight into the development of alternative treatments for hyperglycemia by offering specific regulation of hepatic Pck1 gene expression.