The scaffold protein JLP plays a key role in regulating ultraviolet B‐induced apoptosis in mice

The ultraviolet B (UVB) component of sunlight can cause severe damage to skin cells and even induce skin cancer. Growing evidence indicates that the UVB‐induced signaling network is complex and involves diverse cellular processes. In this study, we investigated the role of c‐Jun NH₂‐terminal kinase‐associated leucine zipper protein (JLP), a scaffold protein for mitogen‐activated protein kinase (MAPK) signaling cascades, in UVB‐induced apoptosis. We found that UVB‐induced skin epidermal apoptosis was prevented in Jlp knockout (KO) as well as in keratinocyte‐specific Jlp KO mice. Analysis of the repair of UVB‐induced DNA damage over time showed no evidence for the involvement of JLP in this process. In contrast, UVB‐stimulated p38 MAPK activation in the skin was impaired in both Jlp KO and keratinocyte‐specific Jlp KO mice. Moreover, topical treatment of UVB‐irradiated mouse skin with a p38 inhibitor significantly suppressed the epidermal apoptosis in wild‐type mice, but not in Jlp KO mice. Our findings suggest that JLP in skin basal keratinocytes plays an important role in UVB‐induced apoptosis by modulating p38 MAPK signaling pathways. This is the first study to show a critical role for JLP in an in vivo response to environmental stimulation.