Cross talk between metabotropic and ionotropic glutamate receptor-mediated signaling in parallel fiber-induced inositol 1,4,5-trisphosphate production in cerebellar Purkinje cells.
In many excitatory glutamatergic synapses, both ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGluRs) are closely distributed on the postsynaptic membrane. However, the functional significance of the close distribution of the two types of glutamate receptors has not been fully clarified. In this study, we examined the functional interaction between iGluR and mGluR at parallel fiber (PF)--> Purkinje cell synapses in the generation of inositol 1,4,5-trisphosphate (IP3), a key second messenger that regulates many important cellular functions. We visualized local IP3 dynamics in Purkinje cells using the green fluorescent protein-tagged pleckstrin homology domain (GFP-PHD) as a fluorescent IP3 probe. Purkinje cells were transduced with Sindbis virus encoding GFP-PHD and imaged with a two-photon laser scanning microscope. Translocation of GFP-PHD from the plasma membrane to the cytoplasm attributable to an increase in IP3 concentration was observed on PF stimulation in fine dendrites of Purkinje cells. Surprisingly, this PF-induced IP3 production was blocked not only by the group I mGluR antagonist but also by the AMPA receptor (AMPAR) antagonist. The PF-induced IP3 production was blocked by either the inhibition of G-protein activation by GDP-betaS or intracellular Ca2+ buffering by BAPTA. These results show that IP3 production is mediated cooperatively by group I mGluR and AMPAR through G-protein activation and Ca2+ influx at PF--> Purkinje cell synapses, identifying the robust cross talk between iGluR and mGluR for the generation of IP3 signals.
Okubo
Yohei
Y
Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan.
Kakizawa
Sho
S
Hirose
Kenzo
K
Iino
Masamitsu
M
D000818:Animals; D002118:Calcium / Q000502:physiology; D003712:Dendrites / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology; D005822:Genetic Vectors; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis*; D000072181:Inositol Polyphosphate 5-Phosphatases; D051379:Mice; D008810:Mice, Inbred C57BL; D009412:Nerve Fibers / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000502:physiology; D018408:Patch-Clamp Techniques; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D011689:Purkinje Cells / Q000378:metabolism* / Q000502:physiology; D018091:Receptors, AMPA / Q000502:physiology*; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D012845:Sindbis Virus
D009419:Nerve Tissue Proteins; D018091:Receptors, AMPA; D018094:Receptors, Metabotropic Glutamate; D011993:Recombinant Fusion Proteins; C033652:postsynaptic density proteins; D015544:Inositol 1,4,5-Trisphosphate; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; D019204:GTP-Binding Proteins; D002118:Calcium