EGR1 coordinates a nuclear IL-33-phosphorylated STAT3 transcriptional complex to promote IL31 expression in TLR1/2-activated keratinocytes.

Abstract

Interleukin (IL)-31 is a pruritogenic cytokine implicated in atopic dermatitis (AD), but its transcriptional regulation in epidermal keratinocytes remains unclear. We investigated whether early growth response 1 (EGR1) links Toll-like receptor (TLR)1/2 signaling to IL31 expression through nuclear IL-33 and signal transducer and activator of transcription 3 (STAT3). EGR1 and IL-31 were prominent in human AD skin, and the TLR1/2 agonist Pam3CSK4 induced keratinocyte IL31 expression, EGR1 accumulation, and STAT3 phosphorylation. DNA affinity precipitation showed recruitment of EGR1, phosphorylated STAT3 (p-STAT3), and IL-33 to proximal IL31 promoter elements, while interaction and proximity-labeling analyses supported an EGR1-associated complex containing IL-33 and p-STAT3. Depletion of EGR1, IL-33, or STAT3 disrupted coordinated promoter recruitment. The EGR1 inhibitor IT25 impaired EGR1 promoter binding, suppressed Pam3CSK4-induced IL31 expression, and reduced epidermal IL-31 in house dust mite-exposed mouse skin. These findings identify EGR1 as a TLR1/2-responsive transcriptional organizer coordinating nuclear IL-33 and activated STAT3 at the IL31 promoter and linking innate receptor activation to keratinocyte IL31 expression.