NF-κB-regulated transcriptional control of CLCA in a differentiated mouse keratinocyte line

Background: CLCA was postulated to be a calcium-activated chloride channel accessory protein. Recent reports indicate that CLCA isoforms are likely to be expressed in different layers of the stratified epithelium of the skin.

Objective: The present study investigated the transcriptional mechanism by which murine CLCA2 (mCLCA2) is expressed in the transformed keratinocyte line Pam212 that can differentiate.

Methods: A luciferase reporter assay, chromatin immunoprecipitation (ChIP) assay, reverse transcription-PCR, and immunocytochemistry were performed using Pam212 cells.

Results: Promoter activity of mCLCA2 was inhibited profoundly by site-directed mutagenesis of a putative nuclear factor-κB (NF-κB) binding site and by treatment with siRNA against p65. ChIP and transcription factor assays showed the specific association of endogenously activated p65 protein with the NF-κB binding domain. As confirmed by the nuclear translocation of p65, tumor necrosis factor α and caffeic acid phenethyl ester (CAPE) increased and decreased mCLCA2 promoter activity, respectively, but exhibited modest effects on endogenous mCLCA2 expression in cells in culture medium containing 0.05 mM Ca(2+). When the Ca(2+) concentration was raised to 1.0mM, the mRNA and protein levels of mCLCA2 increased as well as those of the differentiation markers keratin 1 (K1) and K10. CAPE profoundly suppressed only the Ca(2+)-triggered expression of mCLCA2, not K1 or K10. Immunohistochemistry of native skin and organotypic 3D cultures confirmed the distribution of the CLCA2 homolog in differentiated cells.

Conclusion: The present study revealed for the first time that basal NF-κB activity is involved in the Ca(2+)-dependent regulation of mCLCA2 expression in a mouse keratinocyte line.