cAMP Stringently Regulates Human Cathelicidin Antimicrobial Peptide Expression in the Mucosal Epithelial Cells by Activating cAMP-response Element-binding Protein, AP-1, and Inducible cAMP Early Repressor

Abstract

Little is known about the regulation of the innate host defense peptide cathelicidin at the mucosal surfaces. Expression is believed to be transcriptionally regulated, and several cis-acting elements have been identified in the cathelicidin putative promoter. However, the trans-acting factors have not been clearly defined. We have recently reported that bacterial exotoxins suppress cathelicidin expression in sodium butyrate-differentiated intestinal epithelial cells (ECs), and this may be mediated through inducible cAMP early repressor. Here we have shown that cAMP-signaling pathways transcriptionally regulate cathelicidin expression in various ECs. cAMP-response elementbinding protein (CREB) and AP-1 (activator protein-1) bind to the cathelicidin putative promoter in vitro. Additionally, transcriptional complexes containing CREB, AP-1, and cathelicidin upstream regulatory sequences are formed within ECs. We have also shown that these complexes may activate cathelicidin promoter and are required for its inducible expression in ECs. This is underscored by the fact that silencing of CREB and AP-1 results in failure of ECs to up-regulate cathelicidin, and hepatitis B virus X protein may use CREB to induce cathelicidin. On the other hand, inducible cAMP early repressor competes with CREB and AP-1 for binding to the cathelicidin promoter and represses transcription, thus functioning as a counter-regulatory mechanism. Finally, both CREB and AP-1 were shown to play major roles in the regulation of cathelicidin in sodium butyrate-differentiated HT-29 cells. This is the first report of a detailed mechanistic study of inducible cathelicidin expression in the mucosal ECs. At the same time, it describes a novel immunomodulatory function of cAMP.

MUC2 Mucin and Butyrate Contribute to the Synthesis of the Antimicrobial Peptide Cathelicidin in Response to Entamoeba histolytica- and Dextran Sodium Sulfate-Induced Colitis

“…We have previously shown that cAMP agonist stimulated the secretion of preformed and newly synthesized mucin (26,33). Moreover, cAMP signaling regulates cathelicidin expression by binding CREB and activator protein 1 (AP-1) to the promoter region (25). Thus, we speculate that MUC2 functions as a cAMP ligand to induce the production of cathelicidins from the colonic epithelium.…”

“…Activation of cAMP and mitogen-activated protein kinase (MAPK) signaling pathways is necessary for the simultaneous expression of MUC2 and cathelicidins in colonic epithelial cells. To evaluate common intracellular signaling mechanisms in the regulation of MUC2 and cathelicidins, we focused on the adenylyl cyclase pathway that was shown to transcriptionally regulate cathelicidin (25) and newly synthesized mucin (26) in intestinal epithelial cells. Butyrate activates cyclic AMP (cAMP) response element binding protein (CREB) and increases the activity of cAMP response element (CRE) (27), both of which have been implicated in the activation of the cathelicidin promoter (25).…”

An Inducible and Secreted Eukaryote-Like Serine/Threonine Kinase of Salmonella enterica Serovar Typhi Promotes Intracellular Survival and Pathogenesis

“…THP-1 cells seeded in a 90-mm tissue culture petri dish (10 7 cells/well) were differentiated with PMA (100 nM; 24 h). Cells were infected with bacteria as described under "Gentamicin protection assay" above, and nuclear extracts were prepared as described previously (19). Briefly, THP-1 cells were harvested by scraping, resuspended in low-salt buffer A (10 mM HEPES [pH 7.9], 1.5 mM MgCl 2 , 10 mM KCl), and incubated on ice for 15 min.…”

“…Quantitative PCR (qPCR) was performed in a StepOnePlus system (ABI) using SYBR green master mix. Relative quantitation was done by the comparative threshold cycle (C T ) method (19). The levels of expression of the genes of interest were normalized against that of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene (for cytokine and chemokine gene expression) or 16S rRNA (for S. Typhi gene expression) using the formula 2…”

Predicting functional regulatory SNPs in the human antimicrobial peptide genes DEFB1 and CAMP in tuberculosis and HIV/AIDS

“…In particular, some previous works have related CREB1 to LL-37 induction (Chakraborty et al, 2009) and as a precursor of the major histocompatibility complex class II genes (Fontes et al, 1999). Our results suggest that CREB1 also regulate DEFB1 expression.…”