title: Alpha7 nAChR-mediated activation of MAP kinase pathways in PC12 cells.
abstract: The alpha7 nicotinic acetylcholine receptor (alpha7 nAChR) plays a fundamental role in Ca(2+)-dependent activation of signaling pathways that can modulate intracellular events involved in learning and memory. Activation of extracellular signal-regulated kinase-1 and -2 (ERK1/2) are well documented Ca(2+) signaling events, but these have not been well characterized in response to alpha7 nAChR-selective ligands. The present study examined activation of ERK1/2 and explored pathways leading to CREB phosphorylation utilizing alpha7 nAChR-selective ligands in PC12 cells endogenously expressing alpha7 nAChRs. Robust concentration-dependent increase in ERK1/2 phosphorylation was triggered by structurally diverse alpha7 nAChR agonists such as nicotine, choline, GTS-21, SSR-180711A and PNU-282987 in the presence of the positive allosteric modulator (PAM) PNU-120596. This effect was attenuated by selective alpha7 nAChR antagonists or by chelation of extracellular Ca(2+). ERK1/2 phosphorylation was also attenuated by inhibitors of calmodulin-dependent protein kinase II (CaMKII), p38 MAP kinase and mitogen-activated protein kinase kinase1/2 (MEK1/2), indicating the involvement of these kinases upstream of ERK1/2. This was confirmed by direct measurement of p38 MAPK and MEK1/2 phosphorylation. These data suggest that alpha7 nAChR agonist-triggered Ca(2+) transient in PC12 cells induces activation of CaMKII, leading to sequential phosphorylation of p38 MAPK, MEK1/2, ERK1/2 and CREB. Such mechanisms may endow the alpha7 nAChRs with roles in modulating Ca(2+)-dependent intracellular second messenger events implicated in diverse aspects of cognition.
authors.affiliation: Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064-6125, USA.
authors.forename: Earl J
authors.initials: EJ
authors.lastname: Gubbins
authors.forename: Murali
authors.initials: M
authors.lastname: Gopalakrishnan
authors.forename: Jinhe
authors.initials: J
authors.lastname: Li
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048369:MAP Kinase Kinase 1 / Q000187:drug effects / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D016716:PC12 Cells; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism*; D064569:alpha7 Nicotinic Acetylcholine Receptor; D048051:p38 Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism
chemical_list: C579165:Chrna7 protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D002118:Calcium