S100A7, Jab1, and p27

Psoriasis, a chronic immune-mediated inflammatory skin disease, is characterized by dysregulated keratinocyte proliferation. The EF-hand calcium binding protein S100A7 has been found to be overexpressed in psoriatic keratinocytes. It is know that S100A7 may interact with Jab1, a cofactor that stabilizes c-Jun. Jab1 is known to downregulate the expression of the cell cycle inhibitor p27Kip1 in some cancer models. In this study, we aimed to investigate the possible interaction between S100A7 and Jab1 and the downstream effects on p27 Kip1 expression in normal human keratinocyte cells transfected with S100A7 CRISPR activation plasmid and in archival psoriatic skin samples. Our results showed that the upregulated S100A7 colocalizes with Jab1 at the nuclear level in transfected cells and psoriatic skin samples. We also showed a differential protein expression of Jab1 between cytoplasmic and nuclear compartments, thus suggesting Jab1 translocation from nucleus to cytoplasm. p27 Kip1 protein expression patterns would imply a translocation from nucleus and a subsequent degradation of this protein. The upregulation of S1007 and its interaction with Jab1 would contribute to the p27 Kip1 -dependent impaired proliferation that characterizes psoriatic skin.