title: Long-term potentiation of mGluR1 activity by depolarization-induced Homer1a in mouse cerebellar Purkinje neurons.
abstract: Metabotropic glutamate receptor 1 (mGluR1) plays a crucial role in synaptic plasticity and motor learning in the cerebellum. We have studied activity-dependent changes in mGluR1 function in mouse cultured Purkinje neurons. Depolarizing stimulation potentiated Ca2+ and current responses to an mGluR1 agonist for several hours in the cultured Purkinje neurons. It also blocked internalization of mGluR1 and increased the number of mGluR1s on the cell membrane. We found that depolarization simultaneously increased transcription of Homer1a in Purkinje neurons. Homer1a inhibited internalization and increased cell-surface expression of mGluR1 when coexpressed in human embryonic kidney (HEK)-293 cells. Depolarization-induced Homer1a expression in Purkinje neurons was blocked by a mitogen-activated protein kinase (MAPK) inhibitor. Changes in internalization and mGluR1-mediated Ca2+ response were also blocked by inhibition of MAPK activity, suggesting that localization and activity of mGluR1 were regulated in the same signalling pathway as Homer1a expression. It is thus suggested that depolarization of the Purkinje neuron leads to the increment in mGluR1 responsiveness through MAPK activity and induction of Homer1a expression, which increases active mGluR1 on the cell surface by blocking internalization of mGluR1.
authors.affiliation: Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Itsunari
authors.initials: I
authors.lastname: Minami
authors.forename: Mineko
authors.initials: M
authors.lastname: Kengaku
authors.forename: Peter Sillevis
authors.initials: PS
authors.lastname: Smitt
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Shigemoto
authors.forename: Tomoo
authors.initials: T
authors.lastname: Hirano
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000072233:Homer Scaffolding Proteins; D006801:Humans; D007150:Immunohistochemistry; D007668:Kidney / Q000187:drug effects / Q000502:physiology; D017774:Long-Term Potentiation / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008813:Mice, Inbred ICR; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009473:Neuronal Plasticity / Q000502:physiology*; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011689:Purkinje Cells / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000187:drug effects / Q000378:metabolism*; D012118:Resorcinols / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D018690:Excitatory Amino Acid Agonists; D000072233:Homer Scaffolding Proteins; D009479:Neuropeptides; D012333:RNA, Messenger; D018094:Receptors, Metabotropic Glutamate; D012118:Resorcinols; C104077:metabotropic glutamate receptor type 1; C079215:3,5-dihydroxyphenylglycine; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium; D005998:Glycine