Organ-specific distribution of AP-1 in AP-1 luciferase transgenic mice during the maturation process

Activator protein-1 (AP-1), a dimeric complex consisting of proteins encode d by the jun and fos gene families, is a transcription factor induced by a variety of signals including those eliciting proliferation, differentiation , and neoplastic transformation. Although AP-1 has been widely studied in t he last decade, physiological levels of AP-1 in different tissues are uncle ar. In the present study, we analyzed AP-1 activity in several organs (live r, kidney, brain, lung, spleen, heart, skin) of AP-1-luciferase transgenic mice of various ages. Results of these studies indicate that the level of A P-1 in young mice is much higher than that in older mice, and, second, that the skin contains considerably higher levels of AP-1 than other organs. Th e level of phosphorylated extracellular signal-regulated protein kinase (ER K) in skin was higher in 1- and 2-day-old mice than in mice of other ages. In addition, phosphorylated p38 kinase was high in 2-day-old and 1-wk-old m ice, but phosphorylated c-Jun NH2-terminal kinase was not detected at any a ge. AP-1 activity and level of phosphorylated ERKs declined with maturation . These results imply that AP-1 activity mediated through an ERKs-dependent pathway may be involved in skin development.