IL-22-Induced Ubiquitin-Specific Protease 15 Promotes Proliferation and Inflammation of Keratinocytes through Stabilization of Squamous Cell Carcinoma Antigen 2

Ubiquitin-specific protease 15 (USP15) plays a significant role in regulating various biological processes in several autoimmune diseases and cancers. However, its role in psoriatic keratinocytes (KCs) has not been extensively studied. In this study, we described that USP15 promotes proliferation and inflammation in KCs by stabilizing squamous cell carcinoma antigen 2. We discovered that the expression of USP15 and squamous cell carcinoma antigen 2 was elevated in lesions from patients with clinical psoriasis and an imiquimod-induced psoriatic dermatitis mouse model. USP15 was able to bind, deubiquitinate, and stabilize squamous cell carci-noma antigen 2. Knocking down USP15 resulted in reduced KC inflammation and impaired KC viability and clonogenicity. Topically applying USP15 small interfering RNA significantly ameliorated imiquimod-induced psoriatic dermatitis and reduced the infiltration of T cells and neutrophils. In addition, we determined that IL-22 was a key cytokine that upregulated the expression of USP15. These findings provide insights regarding the mechanisms involved in the proliferation and inflammation of KCs mediated by IL-22, suggesting a potential IL-22-USP15-squamous cell carcinoma antigen 2 axis in the pathogenesis of psoriatic KCs.