PKC and ERK1/2 regulate amylase promoter activity during differentiation of a salivary gland cell line

The addition of transforming growth factor alpha (TGF alpha) to a human sub mandibular gland cell line (HSG) cultured on basement membrane extract Matr igel, synergistically activates the acinar cell-specific salivary amylase p romoter. Signaling through beta 1 integrins and increased phosphorylation o f ERK1/2 are involved in the increased promoter activity. Phorbol-12-myrist ate-13-acetate (PMA) and thapsigargin increase amylase promoter activity, s uggesting that phorbol ester and calcium-dependent protein kinase C (PKC) p athways are also involved. The combination of specific inhibitors of PKC an d MEK1 inhibits the amylase promoter. Inhibitors of the calcium-dependent P KC isoforms alpha, beta, and gamma decrease the promoter activity; however, PKC beta is not detectable in HSG cells. TGF alpha alters the cellular loc alization of PKC alpha but not -gamma, suggesting PKC alpha is involved in TGF alpha upregulation of the amylase promoter. Furthermore, rottlerin, a P KC delta-specific inhibitor, increases the promoter activity, suggesting PK C isoforms differentially regulate the amylase promoter. In conclusion, bet a 1-integrin and TGF alpha signaling pathways regulate the amylase promoter activity in HSG cells. in response to Matrigel and TGF alpha, the activati on of both PKC alpha and phosphorylation of ERK1/2 results in synergistic a ctivation of the amylase promoter. Published 2000 Wiley-Liss, Inc.(dagger)