title: PACAP induces plasticity at autonomic synapses by nAChR-dependent NOS1 activation and AKAP-mediated PKA targeting.
abstract: Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic neuropeptide found at synapses throughout the central and autonomic nervous system. We previously found that PACAP engages a selective G-protein coupled receptor (PAC1R) on ciliary ganglion neurons to rapidly enhance quantal acetylcholine (ACh) release from presynaptic terminals via neuronal nitric oxide synthase (NOS1) and cyclic AMP/protein kinase A (PKA) dependent processes. Here, we examined how PACAP stimulates NO production and targets resultant outcomes to synapses. Scavenging extracellular NO blocked PACAP-induced plasticity supporting a retrograde (post- to presynaptic) NO action on ACh release. Live-cell imaging revealed that PACAP stimulates NO production by mechanisms requiring NOS1, PKA and Ca(2+) influx. Ca(2+)-permeable nicotinic ACh receptors composed of α7 subunits (α7-nAChRs) are potentiated by PKA-dependent PACAP/PAC1R signaling and were required for PACAP-induced NO production and synaptic plasticity since both outcomes were drastically reduced following their selective inhibition. Co-precipitation experiments showed that NOS1 associates with α7-nAChRs, many of which are perisynaptic, as well as with heteromeric α3*-nAChRs that generate the bulk of synaptic activity. NOS1-nAChR physical association could facilitate NO production at perisynaptic and adjacent postsynaptic sites to enhance focal ACh release from juxtaposed presynaptic terminals. The synaptic outcomes of PACAP/PAC1R signaling are localized by PKA anchoring proteins (AKAPs). PKA regulatory-subunit overlay assays identified five AKAPs in ganglion lysates, including a prominent neuronal subtype. Moreover, PACAP-induced synaptic plasticity was selectively blocked when PKA regulatory-subunit binding to AKAPs was inhibited. Taken together, our findings indicate that PACAP/PAC1R signaling coordinates nAChR, NOS1 and AKAP activities to induce targeted, retrograde plasticity at autonomic synapses. Such coordination has broad relevance for understanding the control of autonomic synapses and consequent visceral functions.
authors.affiliation: Department of Neurosciences, University of Toledo, College of Medicine and Life Sciences, United States. Electronic address: Selwyn_Jayakar@hms.harvard.edu.
authors.forename: Selwyn S
authors.initials: SS
authors.lastname: Jayakar
authors.affiliation: Department of Neurosciences, University of Toledo, College of Medicine and Life Sciences, United States. Electronic address: pcp@uab.edu.
authors.forename: Phyllis C
authors.initials: PC
authors.lastname: Pugh
authors.affiliation: Department of Neurosciences, University of Toledo, College of Medicine and Life Sciences, United States. Electronic address: zjd2@case.edu.
authors.forename: Zack
authors.initials: Z
authors.lastname: Dale
authors.affiliation: Department of Neurosciences, University of Toledo, College of Medicine and Life Sciences, United States. Electronic address: eric.starr@rockets.utoledo.edu.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Starr
authors.affiliation: Department of Neurosciences, University of Toledo, College of Medicine and Life Sciences, United States. Electronic address: cole@rockets.utoledo.edu.
authors.forename: Samantha
authors.initials: S
authors.lastname: Cole
authors.affiliation: Department of Neurosciences, University of Toledo, College of Medicine and Life Sciences, United States. Electronic address: Joseph.Margiotta@Utoledo.edu.
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Margiotta
mesh_terms: D054758:A Kinase Anchor Proteins / Q000378:metabolism*; D000818:Animals; D001341:Autonomic Nervous System / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D009473:Neuronal Plasticity; D009474:Neurons / Q000378:metabolism / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000378:metabolism*; D011485:Protein Binding; D011978:Receptors, Nicotinic / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism* / Q000502:physiology
chemical_list: D054758:A Kinase Anchor Proteins; D002118:Calcium; D017868:Cyclic AMP-Dependent Protein Kinases; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011978:Receptors, Nicotinic
keywords: Alpha-7; Biomarker; Excitatory postsynaptic current; Neuronal nitric oxide synthase; Neuropeptide; Nicotinic acetylcholine receptor; Patch clamp; Stress disorder; Synapse; Synaptic plasticity; Synaptic transmission; pituitary adenylate cyclase activating polypeptide