LMO4 Is a Disease-Provocative Transcription Coregulator Activated by IL-23 in Psoriatic Keratinocytes.

Psoriasis is an autoimmune disease characterized by abnormal differentiation and hyperproliferation of epidermal keratinocytes. LIM-domain only protein 4 (LMO4) is a transcription factor coregulator that promotes the assembly of multiprotein complexes to regulate mammary epithelium and keratinocyte differentiation and proliferation during embryogenesis. In this study, LMO4 has been found to be abundantly expressed in psoriatic epidermis. LMO4 expression is increased in human keratinocytes induced to differentiate by calcium ex vivo, and LMO4 overexpression induces spontaneous differentiation and growth acceleration of human keratinocytes in the absence of calcium. IL-23, a cytokine highly expressed in psoriatic skin lesions, induces differentiation and promotes proliferation of human keratinocytes. The IL-23-mediated effects are accompanied by an increase in LMO4 expression mediated by signal transducer and activator of transcription 3 through an IL-23/acutely transforming retrovirus AKT8 in rodent T-cell lymphoma/signal transducer and activator of transcription 3 pathway in keratinocytes. Knockdown of LMO4 effectively inhibits differentiation and growth of keratinocytes both ex vivo and in IL-23-injected ears of mice. LMO4 appears to mediate IL-23-related responses in psoriatic keratinocytes and is a potential therapeutic target in psoriasis.