The cAMP responsive element and CREB partially mediate the response of thetyrosine hydroxylase gene to phorbol ester

Tyrosine hydroxylase (TH) gene promoter activity is increased in PC12 cells that are treated with the phorbol ester, 12-O-tetradecanoylphorbol 13-acet ate (TPA). Mutagenesis of either the cAMP responsive element (CRE) or the a ctivator protein-1 element (AP1) within the TH gene proximal promoter leads to a dramatic inhibition of the TPA response. The TH CRE and TH AP1 sites are also independently responsive to TPA in minimal promoter constructs. TP A treatment results in phosphorylation of cAMP responsive element binding p rotein (CREB) and activation of cAMP-dependent protein kinase (PKA) in PC12 cells; hence, we tested whether CREB and/or PKA are essential for the TPA response. In CREB-deficient cells, the response of the full TH gene proxima l promoter or the independent response of the TH CRE by itself to TPA is in hibited. The TPA-inducibility of TH mRNA is also blocked in CREB-deficient cells. Expression of the PKA inhibitor protein, PKI, also inhibits the inde pendent response of the TH CRE to IPA. Our results support the hypothesis t hat TPA stimulates the TH gene promoter via signaling pathways that activat e either the TH AP1 or TH CRE sites. Both signaling pathways are dependent on CREB and the TH CRE-mediated pathway is dependent on PKA.