A critical role for IFN-β signaling for IFN-κ induction in keratinocytes
Bin Xu, Jon Musai, Yee Sun Tan, Grace A. Hile, William R. Swindell, Benjamin Klein, Jun Qin, Mrinal K. Sarkar, Jóhann E. Guðjónsson, J. Michelle Kahlenberg
Abstract
Background/Purpose Cutaneous lupus erythematosus (CLE) affects up to 70% of patients with systemic lupus erythematosus (SLE), and type I interferons (IFNs) are important promoters of SLE and CLE. Our previous work identified IFN-kappa (IFN-κ), a keratinocyte-produced type I IFN, as upregulated in non-lesional and lesional lupus skin and as a critical regulator for enhanced UVB-mediated cell death in SLE keratinocytes. Importantly, the molecular mechanisms governing regulation of IFN-κ expression have been relatively unexplored. Thus, this study sought to identify critical regulators of IFN-κ and identified a novel role for IFN-beta (IFN-β). Methods Human N/TERT keratinocytes were treated with the RNA mimic poly (I:C) or 50 mJ/cm 2 ultraviolet B (UVB), followed by mRNA expression quantification by RT-qPCR in the presence or absence neutralizing antibody to the type I IFN receptor (IFNAR). IFNB and STAT1 knockout (KO) keratinocytes were generated using CRISPR/Cas9. Results Time courses of poly(I:C) and UVB treatment revealed a differential expression of IFNB , which was upregulated between 3 and 6 h and IFNK , which was upregulated 24 h after stimulation. Intriguingly, only IFNK expression was substantially abrogated by neutralizing antibodies to IFNAR, suggesting that IFNK upregulation required type I IFN signaling for induction. Indeed, deletion of IFNB abrogated IFNK expression . Further exploration confirmed a role for type I IFN-triggered STAT1 activation. Conclusion Collectively, our work describes a novel mechanistic paradigm in keratinocytes in which initial IFN-κ induction in response to poly(I:C) and UVB is IFNβ1-dependent, thus describing IFNK as both an IFN gene and an interferon-stimulated gene.