Keratin 16 spatially inhibits type I interferon responses in stressed skin.

The stress-induced keratin intermediate filament gene/protein KRT16 (K16) is spatially restricted to the suprabasal compartment of the epidermis and extensively used as a biomarker for psoriasis, hidradenitis suppurativa, atopic dermatitis and other inflammatory disorders. However, its role in these conditions remains poorly defined. Here we show that K16 negatively regulates type-I interferon (IFN) signaling and innate immune responses. In mouse skin in vivo, loss of Krt16 leads to exacerbation of imiquimod-induced psoriasiform disease and heightened recruitment of neutrophils in a phorbol ester-induced model of acute sterile inflammation. In KRT16 null human keratinocytes, loss of K16 amplifies IFN signaling including phospho-IRF7 and ISG15 after treatment with synthetic dsRNA poly(I:C). Mechanistically, K16 interacts with effectors of the RIG-I-like receptor (RLR) pathway, including 14-3-3ɛ, and inhibits the 14-3-3ɛ:RIG-I interaction upstream of IFN activation in vivo and ex vivo . These findings uncover a new paradigm for keratin-dependent regulation of innate immunity, with significant implications for our understanding of inflammatory skin diseases.