Citation

CREB and C/EBP signaling pathways are modulated during inflammation and also targeted by Bacillus anthracis edema toxin (ET), but how these factors individually and jointly contribute to changes in immune cell function is poorly understood. Using CRISPR/Cas9 gene editing, macrophage cell lines lacking CREB and isoforms of C/EBP were generated and analyzed for changes in responses to LPS, ET, and IL-4. Macrophages lacking C/EBP suppressed induction of IL-10 and Arg1, while IL-6 was increased in these cells following exposure to LPS. Examination of C/EBP isoforms indicated the 38kDa isoform was necessary for the expression of IL-10 and Arg1. ChIP-Seq analysis of CREB and C/EBP binding to targets on the chromosome of human PBMC identified several regions where both factors overlapped in their binding, suggesting similar gene targeting or cooperative effects. Based on the ChIP-Seq data, a panel of previously unknown targets of CREB and C/EBP was identified and includes genes such as VNN2, GINS4, CTNNBL1, and SULF2. Isoforms of a transcriptional corepressor, transducin-like enhancer of Split (TLE), were also found to have CREB and C/EBP binding their promoter and were up regulated by ET. Finally, we explore a possible layer of C/EBP regulation by a protein complex consisting of adenomatous polyposis coli (APC) and PKA. Collectively, these data provide new insights into the role of CREB and C/EBP as immunosignaling regulators and targets of an important bacterial virulence factor.