PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE TRIGGERS DUAL TRANSDUCTION SIGNALING IN CATH.A CELLS AND TRANSCRIPTIONALLY ACTIVATES TYROSINE-HYDROXYLASE AND C-FOS EXPRESSION

We used a catecholaminergic neuron-like cell line (CATH.a cells) as a model system to investigate the likelihood that pituitary adenylate cy clase-activating polypeptide (PACAP) may participate in the regulation of specific gene expression in catecholaminergic neurons. Analysis by reverse transcriptase-PCR amplification revealed the presence in thes e cells of type I PACAP receptors, with a short isoform, together with a heavier so-called Hop splice variant. PACAP38 and PACAP27 enhanced, in a dose-dependent manner, both cyclic AMP formation and phosphoinos itide breakdown, with EC(50), values of, respectively, 0.6 x 10(-10) a nd 2 x 10(-9) M. These peptides, in addition, also elevated [Ca2+](i) by mobilizing intracellular calcium pools. Vasoactive intestinal pepti de (VIP) was similar to 1,000-fold less potent in stimulating cyclic A MP (with EC(50) = 2 x 10(-7) M) and failed to change the turnover of p hosphoinositides and to alter [Ca2+](i). Both forms of PACAP, as well as forskolin, stimulated transcriptional induction of tyrosine hydroxy lase (TH) and c-fos promoters fused to a chloramphenicol acetyltransfe rase (CAT) reporter gene in transiently transfected cells (p < 0.01 vs . controls). Induction of CAT activity linked to both TH and c-fos pro moters was obliterated upon coexpression of a dominant inhibitory muta nt (Mt-RAB) of cyclic AMP-dependent protein kinase. We conclude that C ATH.a cells do express functional PACAP type I receptors, the activati on of which impinges on TH and c-fos transcription according to a proc ess that is primarily dependent on the cyclic AMP-PKA pathway.