Inflammatory Cytokines and cAMP Regulate Amelotin Gene Transcription

Abstract

Amelotin（AMTN）is an enamel protein secreted by ameloblasts at maturation stage and expressed in internal basal lamina of junctional epithelium（JE）which attaches to the tooth enamel. JE may prevent invasion of bacteria into the periodontal tissue. AMTN localization suggests that the function might be responsible for cell adhesion. The aim of this study was to elucidate the effect of interleukin-1β（IL-1β）, tumor necrosis factor-α（TNF-α）or forskolin（FSK）on AMTN gene transcription in human gingival fibroblast（HGF）, human gingival epithelial Sa3 or Ca9-22 cells. IL-1β（1ng/ml）and TNF-α（10 ng/ml）increased promoter activities of -211, -353, -501, -769 and -950AMTN LUC constructs in HGF. TNF-α（10ng/ml）induced LUC activities of these five AMTN constructs in Sa3 cells. FSK（1µM）increased AMTN mRNA levels at 12 and 24 h in Ca9-22 cells. FSK（1µM, 12h）induced LUC activities of all six AMTN LUC constructs in Ca9-22 cells. These results demonstrated that IL-1β and TNF-α increased AMTN gene transcription in HGF and Sa3 cells. FSK increased AMTN gene transcription mediated through AP1 site in the human AMTN gene promoter. α upregulated - 211, - 353, - 501, - 769 and - 950AMTN gene promoter constructs in Sa3 cells. AMTN mRNA levels were increased significantly by FSK（1µM）at 12 and 24 h in Ca9 - 22 cells, and FSK（1µM） induced transcriptional activities of all AMTN LUC constructs at 12 h in Ca9-22 cells. These results suggest that FSK induced AMTN gene transcription via AP1 between -94 ~ -84 in the human AMTN gene promoter. Further research is requiring to analyze the role of cAMP on the expression and function of AMTN.