title: Nerve growth factor increases connexin43 phosphorylation and gap junctional intercellular communication.
abstract: The function of gap junctions is regulated by the phosphorylation state of their connexin subunits. Numerous growth factors are known to regulate connexin phosphorylation; however, the effect of nerve growth factor on gap junction function is not understood. The phosphorylation of connexin subunits is a key event during many aspects of the lifecycle of a connexin, including open/close states, assembly/trafficking, and degradation, and thus affects the functionality of the channel. PC12 cells infected with connexin43 (Cx43) retrovirus were used as a neuronal model to characterize the signal transduction pathways activated by nerve growth factor (NGF) that potentially affect the functional state of Cx43. Immunoblot analysis demonstrated that Cx43 and the mitogen-activated protein kinase (MAPK), ERK-1/2, were phosphorylated in response to TrkA activation via NGF and that phosphorylation could be prevented by treatment with the MEK-1/2 inhibitor U0126. The effects of NGF on gap junction intercellular communication were examined by monitoring fluorescence recovery after photobleaching PC12-Cx43 cells preloaded with calcein. Fluorescence recovery in the photobleached area increased after NGF treatment and decreased when pretreated with the MEK-1/2 inhibitor U0126. These data are the first to show a direct signaling link between neurotrophins and the phosphorylation of connexin proteins through the MAPK pathway resulting in increased gap junctional intercellular communication. Neurotrophic regulation of connexin activity provides a novel mechanism of regulating intercellular communication between neurons during nervous system development and repair.
authors.affiliation: Department of Anatomy and Cell Biology, Faculty of Medicine and Dentistry, The University of Western Ontario, London, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Cushing
authors.forename: Ruchi
authors.initials: R
authors.lastname: Bhalla
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Johnson
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Rushlow
authors.forename: Susan O
authors.initials: SO
authors.lastname: Meakin
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Belliveau
mesh_terms: D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002070:Butadienes / Q000494:pharmacology; D002450:Cell Communication / Q000187:drug effects* / Q000502:physiology; D045744:Cell Line, Tumor; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007365:Intercellular Junctions / Q000187:drug effects* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases; D009154:Mutation; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009447:Neuroblastoma / Q000473:pathology; D009570:Nitriles / Q000494:pharmacology; D016716:PC12 Cells / Q000145:classification; D010766:Phosphorylation / Q000187:drug effects; D038761:Photobleaching / Q000187:drug effects; D051381:Rats; D012190:Retroviridae / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D002070:Butadienes; D018031:Connexin 43; D004791:Enzyme Inhibitors; D009414:Nerve Growth Factors; D009570:Nitriles; C113580:U 0126; D014446:Tyrosine 3-Monooxygenase; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases