Characterization of phorbolester-inducible human neuronal factors involved in trans-activation of the galanin gene.

The expression of the neuropeptide galanin (GAL) is elevated in vivo upon nerve stimulation, injury, and in vitro by phorbol 12-myristate-13-acetate (PMA), suggesting that a signal pathway involving protein kinase C activation may be involved in GAL-gene activation. When plasmids containing a different length of the bovine GAL-promoter fused to luciferase were transfected into the human neuroblastoma cell line (SK-N-SH subclone SH-SY5Y), a PMA-responsive element was identified in the promoter-region -68 to -46 base pairs (bp). Co-transfection experiments with plasmids expressing cJun and cFos revealed that they could act alone, as well as synergistically with PMA to induce luciferase activity. Electrical mobility shift assays revealed that a cAMP response element (CRE)-like sequence (TGACGCGG; -59 to -52 bp) bound PMA-inducible nuclear proteins present in SH-SY5Y cells. These proteins appear to bind mainly as CRE-binding protein/activating-transcription-factor (CREB/ATF) and Jun/ATF heterodimers. In addition, an apparent PMA-inducible protein(s) not recognized by CREB/ATF and Jun antibodies bound to the CRE-like containing probe.