RNF31 Regulates Skin Homeostasis by Protecting Epidermal Keratinocytes from Cell Death

Linear ubiquitin chain assembly complex plays an important role in regulating TNF-alpha signaling activation by modifying target proteins with linear (M1-linked) ubiquitin chains. In this study, we report that the epidermis-specific knockout (KO) of RNF31, the catalytic subunit of linear ubiquitin chain assembly complex, results in an early postnatal lethality in mice due to severe skin inflammation. The inflammation was mainly triggered by TNF-alpha-induced apoptosis in RNF31 KO keratinocytes. Mechanistically, the deficiency of RNF31 not only impaired TNF-alpha-induced NF-kB activation, but also significantly increased apoptosis. Consistently, deleting TNF receptor 1 could rescue the lethality of RNF31 epidermis-specific KO mice and also the skin inflammation. Collectively, our study provides an in vivo insight that linear ubiquitination is critical for maintaining the homeostasis of keratinocytes, which will shed light on designing therapeutic compounds to treat skin inflammation.