EGF stimulates transcription of CaN19 (S100A2) in HaCaT keratinocytes

CaN19 (S100A2), a member of the S100 family of calcium-binding proteins, was originally isolated in a screen for tumor suppressor genes. Recent work from our laboratory suggests that CaN19 is likely to be an effector of the regenerative hyperplasia pathway of epidermal differentiation. As other work from our laboratory in a human skin organ culture model suggests that this response is mediated by activation of the epidermal growth factor (EGF) receptor and/or related receptors of the ErbB family, we asked whether CaN19 expression could be increased by organ culture and by EGF treatment of human keratinocytes. CaN19 was strongly induced after 24 h of organ culture, and its induction could be blocked by PD153035, a specific inhibitor of EGF receptor tyrosine kinase activity. EGF treatment of immortalized human keratinocytes (HaCaT cells) increased CaN19 mRNA levels by 4.5-fold within 8 h, and a corresponding increase in CaN19 protein was observed by western blotting. EGF treatment had no effect on the expression of five other members of the S100A gene cluster. As assessed by nuclear run-off assay, CaN19 transcription increased rapidly in response to EGF, reaching a maximum induction of 16-fold after 2 h. In contrast, EGF treatment had no detectable effects on the decay of CaN19 transcripts, which were long lived (t1/2 > 6 h) in the presence or absence of EGF. PD153035 also blocked CaN19 transcription and the accumulation of CaN19 mRNA and protein in HaCaT cells. These results demonstrate that EGF receptor activation selectively stimulates CaN19 gene expression at the transcriptional level in human keratinocytes, and support the hypothesis that CaN19 is an important mediator of regenerative epidermal hyperplasia.