Ubiquitin-specific peptidase 47 (USP47) regulates cutaneous oxidative injury through nicotinamide nucleotide transhydrogenase (NNT)

Human skin is daily exposed to oxidative stresses in the environment such as physical stimulation, chemical pollutants and pathogenic microorganisms, which are likely to cause skin diseases. As important post-translational modifications, protein ubiquitination and deubiquitination play crucial roles in maintaining cellular homeostasis by the proteolytic removal of oxidized proteins. We have previously reported that the expression of ubiquitin-specific protease 47 (USP47), a kind of deubiquitinating enzymes (DUBs), was significantly elevated in response to oxidative stress. However, the role of USP47 in cutaneous oxidative injury remains unclear. Usp47 wild-type (Usp47+/+) mice and Usp47 knockout (Usp47−/−) mice were used to establish two animal models of oxidative skin damage: (1) radiation- and (2) imiquimod (IMQ)-induced skin injury. Loss of Usp47 consistently aggravated mouse skin damage in vivo. Subsequently, we screened 63 upregulated and 170 downregulated proteins between the skin tissues of wild-type and Usp47−/− mice after 35 Gy electron beam radiation using proteomic analysis. Among the dysregulated proteins, nicotinamide nucleotide transhydrogenase (NNT), which has been reported as a significant regulator of oxidative stress and redox homeostasis, was further investigated in detail. Results showed that NNT was regulated by USP47 through direct ubiquitination mediated degradation and involved in the pathogenesis of cutaneous oxidative injury. Knockdown of NNT expression dramatically limited the energy production ability, with elevated mitochondrial reactive oxygen species (ROS) accumulation and increased mitochondrial membrane potential in irradiated HaCaT cells. Taken together, our present findings illustrate the critical role of USP47 in oxidative skin damage by modulating NNT degradation and mitochondrial homeostasis.