POU homeodomain protein Oct-1 functions as a sensor for cyclic AMP

Abstract

Cyclic AMP is a fundamentally important second messenger for numerous peptide hormones and neurotransmitters that control gene expression, cell proliferation, and metabolic homeostasis. Here we show that cAMP works with the POU homeodomain protein Oct-1 to regulate gene expression in pancreatic and intestinal endocrine cells. This ubiquitously expressed transcription factor is known as a stress sensor. We found that it also functions as a repressor of Cdx-2, a proglucagon gene activator. Through a mechanism that involves the activation of exchange protein activated by cyclic AMP, elevation of cAMP leads to enhanced phosphorylation and nuclear exclusion of Oct-1 and reduced interactions between Oct-1 or nuclear co-repressors and the Cdx-2 gene promoter, detected by chromatin immunoprecipitation. In rat primary pancreatic islet cells, cAMP elevation also reduces nuclear Oct-1 content, which causes increased proglucagon and proinsulin mRNA expression. Our study therefore identifies a novel mechanism by which cAMP regulates hormone-gene expression and suggests that ubiquitously expressed Oct-1 may play a role in metabolic homeostasis by functioning as a sensor for cAMP.