Molecular mechanisms associated with peptidergic control of adrenergic function

Phenylethanolamine N‐methyltransferase (PNMT), which produces epinephrine, is a marker of adrenergic function. While pituitary adenylate cyclase activating polypeptide (PACAP), independently and cooperatively with NGF, activates PNMT promoter‐driven and endogenous PNMT gene expression in PC12 cells, molecular mechanisms remain unknown. Transfection assays in PC12 cells and PKA‐deficient and PLCγ1‐deficient PC12 cells using PNMT promoter‐luciferase gene constructs and signaling inhibitors showed that PLCγl and cAMP‐dependent PKA signaling are critical for PACAP activation and PI3K, PKC, ERK1/2 MAPK, p38 MAPK downstream. The inhibitors also abrogated PACAPergic induction of endogenous PNMT. Western analysis of nuclear protein from PACAP‐treated PC12 cells showed that Egr‐1 and AP‐2 underlie PACAP responses. Results with nested deletion or site‐directed mutant constructs support this possibility. Exposure of PACAP‐treated transfected and untransfected PC12 cells to histone deacetylase (HDAC) inhibitors, Na butyrate or Trichostatine A, incrementally activated the PNMT promoter and endogenous PNMT. Findings indicate that PACAP transcriptionally activates the PNMT gene with HDAC being limiting. Presence of long and short forms of PNMT mRNA further suggest post‐transcriptional regulation by PACAP. Support: Spunk Fund, Inc., Sobel‐Keller Fund and McLean Hospital.