Eosinophilic esophagitis-linked calpain 14 is an IL-13-induced protease that mediates esophageal epithelial barrier impairment.

Abstract

We recently identified a genome-wide genetic association of eosinophilic esophagitis (EoE) at 2p23 spanning the calpain 14 (<i>CAPN14</i>) gene, yet the causal mechanism has not been elucidated. We now show that recombinant CAPN14 cleaves a calpain-specific substrate and is inhibited by 4 classical calpain inhibitors: MDL-28170, acetyl-calpastatin, E-64, and PD151746. CAPN14 is specifically induced (>100-fold) in esophageal epithelium after IL-13 treatment. Epithelial cells overexpressing CAPN14 display impaired epithelial architecture, characterized by acantholysis, epidermal clefting, and epidermolysis. CAPN14 overexpression impairs epithelial barrier function, as demonstrated by decreased transepithelial resistance (2.1-fold) and increased FITC-dextran flux (2.6-fold). Epithelium with gene-silenced <i>CAPN14</i> demonstrates increased dilated intercellular spaces (5.5-fold) and less organized basal cell layering (1.5-fold) following IL-13 treatment. Finally, CAPN14 overexpression results in loss of desmoglein 1 (DSG1) expression, whereas the IL-13-induced loss of DSG1 is normalized by <i>CAPN14</i> gene silencing. Importantly, these findings were specific to CAPN14, as they were not observed with modulation of CAPN1 expression. These results, along with the potent induction of <i>CAPN14</i> by IL-13 and genetic linkage of EoE to the <i>CAPN14</i> gene locus, demonstrate a molecular and cellular pathway that contributes to T helper type 2 responses in mucosal epithelium.