title: Cancer metastasis-suppressing peptide metastin upregulates excitatory synaptic transmission in hippocampal dentate granule cells.
abstract: Metastin is an antimetastatic peptide encoded by the KiSS-1 gene in cancer cells. Recent studies found that metastin is a ligand for the orphan G-protein-coupled receptor GPR54, which is highly expressed in specific brain regions such as the hypothalamus and parts of the hippocampus. This study shows that activation of GPR54 by submicromolar concentrations of metastin reversibly enhances excitatory synaptic transmission in hippocampal dentate granule cells in a mitogen-activated protein (MAP) kinase-dependent manner. Synaptic enhancement by metastin was suppressed by intracellular application of the G-protein inhibitor GDP-beta-S and the calcium chelator BAPTA. Analysis of miniature excitatory postsynaptic currents (mEPSCs) revealed an increase in the mean amplitude but no change in event frequency. This indicates that GPR54 and the mechanism responsible for the increase in EPSCs are postsynaptic. Metastin-induced synaptic potentiation was abolished by 50 microM PD98059 and 20 microM U0126, two inhibitors of the MAP kinases ERK1 and ERK2. The effect was also blocked by inhibitors of calcium/calmodulin-dependent kinases and tyrosine kinases. RT-PCR experiments showed that both KiSS-1 and GPR54 are expressed in the hippocampal dentate gyrus. Metastin is thus a novel endogenous factor that modulates synaptic excitability in the dentate gyrus through mechanisms involving MAP kinases, which in turn may be controlled upstream by calcium-activated kinases and tyrosine kinases.
authors.affiliation: Department of Pharmacology, 801 N. Rutledge St., P.O. Box 19629, Springfield, IL 62794-9629, USA. aarai@siumed.edu
authors.forename: Amy C
authors.initials: AC
authors.lastname: Arai
authors.forename: Yan-Fang
authors.initials: YF
authors.lastname: Xia
authors.forename: Erika
authors.initials: E
authors.lastname: Suzuki
authors.forename: Markus
authors.initials: M
authors.lastname: Kessler
authors.forename: Olivier
authors.initials: O
authors.lastname: Civelli
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Nothacker
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D059648:Kisspeptins; D020935:MAP Kinase Signaling System / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D025521:Tumor Suppressor Proteins
chemical_list: C106628:KISS1 protein, human; D059648:Kisspeptins; D011506:Proteins; D025521:Tumor Suppressor Proteins; D020928:Mitogen-Activated Protein Kinases