Genetic, Inflammatory, and Epithelial Cell Differentiation Factors Control Expression of Human Calpain-14

Abstract

Eosinophilic esophagitis (EoE) is a chronic, food-driven allergic disease resulting in eosinophilic esophageal inflammation. We recently found that EoE susceptibility is associated with genetic variants in the promoter of <i>CAPN14</i>, a gene with reported esophagus-specific expression. <i>CAPN14</i> is dynamically up-regulated as a function of EoE disease activity and after exposure of epithelial cells to interleukin-13 (IL-13). Herein, we aimed to explore molecular modulation of <i>CAPN14</i> expression. We identified three putative binding sites for the IL-13-activated transcription factor STAT6 in the promoter and first intron of <i>CAPN14</i> Luciferase reporter assays revealed that the two most distal STAT6 elements were required for the ∼10-fold increase in promoter activity subsequent to stimulation with IL-13 or IL-4, and also for the genotype-dependent reduction in IL-13-induced promoter activity. One of the STAT6 elements in the promoter was necessary for IL-13-mediated induction of <i>CAPN14</i> promoter activity while the other STAT6 promoter element was necessary for full induction. Chromatin immunoprecipitation in IL-13 stimulated esophageal epithelial cells was used to further support STAT6 binding to the promoter of <i>CAPN14</i> at these STAT6 binding sites. The highest <i>CAPN14</i> and calpain-14 expression occurred with IL-13 or IL-4 stimulation of esophageal epithelial cells under culture conditions that allow the cells to differentiate into a stratified epithelium. This work corroborates a candidate molecular mechanism for EoE disease etiology in which the risk variant at 2p23 dampens <i>CAPN14</i> expression in differentiated esophageal epithelial cells following IL-13/STAT6 induction of <i>CAPN14</i> promoter activity.