Regulation of MYC by CARD14 in Human Epithelium is a Determinant of Epidermal Homeostasis and Disease I

Caspase recruitment domain family member 14 (CARD14) and its variants are associated with both atopic dermatitis (AD) and psoriasis, but their mechanistic impact on skin barrier homeostasis is largely unknown. CARD14 is known to signal via NF?B, however, CARD14-NF?B signaling does not fully explain the heterogeneity of CARD14-driven disease. Herein, we describe a direct interaction between CARD14 and MYC and show that CARD14 signals through MYC in keratinocytes to coordinate skin barrier homeostasis. CARD14 directly binds MYC and influences barrier formation in a MYC-dependent fashion, and this mechanism is undermined by disease-associated CARD14 variants. These studies establish a paradigm that CARD14 activation regulates skin barrier function by two distinct mechanisms including activating NF?B to bolster the antimicrobial (chemical) barrier and stimulating MYC to bolster the physical barrier. Finally, we show that CARD14-dependent MYC signaling occurs in other epithelia expanding the impact of our findings beyond the skin. Overall design: To determine differentially-activated pathways by WT CARD14 (vehicle- and mepazine-treated) vs R820W CARD14 (vehicle- and mepazine-treated) vs CARD14-deficiency, we utilized HaCat keratinocytes CRISPR-edited to harbor the desired genotype and cultured them with the MALT1 inhibitor mepazine or vehicle. We then performed RNA-sequencing and subsequent analysis of three independent experiments.