title: Activation of MEK/ERK Signaling by PACAP in Guinea Pig Cardiac Neurons.
abstract: Pituitary adenylate cyclase-activating polypeptide (PACAP) signaling can increase guinea pig cardiac neuron excitability in part through extracellular signal-regulated kinase (ERK) activation. The present study examined the PACAP receptors and signaling cascades that stimulate guinea pig cardiac neuron ERK signaling using confocal microscopy to quantify PACAP-induced neuronal phosphorylated ERK (pERK) immunoreactivity. PACAP and maxadilan, but not vasoactive intestinal polypeptide (VIP), increased cardiac neuron pERK, implicating primary roles for PACAP-selective PAC1 receptor (Adcyap1r1) signaling rather than VPAC receptors (Vipr1 and Vipr2) in the generation of cardiac neuron pERK. The adenylyl cyclase (AC) activator forskolin, but not the protein kinase C (PKC) activator phorbol myristate acetate (PMA), increased pERK. Also, Bim1 did not blunt PACAP activation of pERK. Together, the results suggest PAC1 receptor signal transduction via Gs/adenylyl cyclase (AC)/cAMP rather than Gq/phospholipase C (PLC) generated neuronal pERK. Activator and inhibitor studies suggested that the PACAP-mediated pERK activation was PKA-dependent rather than an exchange protein directly activated by a cAMP (EPAC), PKA-independent mechanism. The PACAP-induced pERK was inhibited by the clathrin inhibitor Pitstop2 to block receptor internalization and endosomal signaling. We propose that the PACAP-mediated MEK/ERK activation in cardiac neurons involves both AC/cAMP/PKA signaling and PAC1 receptor internalization/activation of signaling endosomes.
authors.affiliation: Department of Neurological Sciences, College of Medicine, University of Vermont, Burlington, VT, 05405, USA.
authors.forename: Todd A
authors.initials: TA
authors.lastname: Clason
authors.affiliation: Department of Neurological Sciences, College of Medicine, University of Vermont, Burlington, VT, 05405, USA.
authors.forename: Beatrice M
authors.initials: BM
authors.lastname: Girard
authors.affiliation: Department of Neurological Sciences, College of Medicine, University of Vermont, Burlington, VT, 05405, USA.
authors.forename: Victor
authors.initials: V
authors.lastname: May
authors.affiliation: Department of Neurological Sciences, College of Medicine, University of Vermont, Burlington, VT, 05405, USA. Rodney.Parsons@med.uvm.edu.
authors.forename: Rodney L
authors.initials: RL
authors.lastname: Parsons
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005260:Female; D006168:Guinea Pigs; D020935:MAP Kinase Signaling System; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051239:Receptors, Vasoactive Intestinal Peptide, Type II / Q000235:genetics / Q000378:metabolism; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I / Q000235:genetics / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D047428:Protein Kinase Inhibitors; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; C495507:Vipr1 protein, mouse; C495510:Vipr2 protein, mouse; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D013755:Tetradecanoylphorbol Acetate
keywords: Autonomic neuron; MAPK signaling; PAC1 endocytosis; PACAP; PKA