Intrinsic Abnormalities of Keratinocytes Initiate Skin Inflammation through the IL-23/T17 Axis in a MALT1-Dependent Manner.

Increasing evidence has supported the crucial role of CARD14 in the pathogenesis of psoriasis, whereas the precise cellular signaling involved in skin physiopathology remains poorly understood. In this article, we show that neither genetic ablation of Il17a nor elimination of T cells was sufficient to restrain the skin inflammation in a CARD14-E138A-mutation-induced psoriasis-like mouse model, whereas depletion of Il23, which extremely blocked the IL-23/T17 axis, was more effective. Targeting CBM complex by conditional deletion of MALT1 or BCL10 in keratinocytes abrogated both the cutaneous and systemic inflammation of heterozygous Card14 E138A/+ mice. Selective inactivation of keratinocyte-specific MALT1 proteolytic activity strongly ameliorated the Card14 E138A/+- and Card14 ΔQ136/+-induced skin disease, which was reproduced by using the imiquimod-induced mouse model. Together, our results suggest a sequence of events under CARD14-mutation-induced psoriasis condition that keratinocyte-intrinsic activation of CBM complex initiates the skin inflammation depending on the IL-23/T17 axis. Targeting keratinocytes by inactivation of MALT1 paracaspase activity might be a promising therapeutic target for early psoriasis treatment.