Glutamate ReceptorsOutlineHistoryearly evidence for excitation by glutamatePharmacologyiGluR subtypesRationale for complexity: integrationPowerPoint Presentationglutamate receptor pharmacologySlide 10StructureSlide 12Slide 13orientation of KcsA versus iGluRSlide 15Slide 16Slide 17Slide 18Slide 19PhysiologyI-V relation for whole cell current through NMDA receptorsVoltage-dependent block of NMDA receptor single channels by Mg2+glycine is a co-agonist at NMDA receptorsagonist-dependent desensitization of AMPA receptorskainate desensitizes kainate receptorsI-V relations for the peak and decay phaseAPV blocks the slow component of transmissionCNQX blocks the fast componentvoltage-dependent block by Mg2+Why is the NMDA receptor-mediated component slow?brief pulses of glutamate elicit prolonged burstsSpecializationAlternate splicing can alter gating, modulation and traffickingsplicing and editingFlip/flop splicing alters desensitization kineticsC-tail splicing alters modulation and traffickingSlide 37RNA Editing can alter permeation and gatingadenosine deaminaseintronic hairpins define the editing siteQ/R site RNA editing regulates permeationSlide 42differences in EPSC time coursesummaryGlutamate ReceptorsPrimary reading: •Hestrin S, Nicoll RA, Perkel DJ, Sah P. (1990) Analysis of excitatory synaptic action in pyramidal cells using whole-cell recording from rat hippocampal slices. J Physiol. 422:203-25.Secondary readings:•Sobolevsky AI. (2015) Structure and Gating of Tetrameric Glutamate Receptors. J Physiol. 593:29-38.•Traynelis SF, et al. (2010) Glutamate receptor ion channels: structure, regulation, and function. Pharmacol Rev. 62(3):405-96.•Granger AJ, Shi Y, Lu W, Cerpas M, Nicoll RA. (2013) LTP requires a reserve pool of glutamate receptors independent of subunit type. Nature. 493:495-500. •Herring BE, Nicoll RA. (2016) Long-Term Potentiation: From CaMKII to AMPA Receptor Trafficking. Annu Rev Physiol. 78:351-65.•Henley JM, Wilkinson KA. (2016) Synaptic AMPA receptor composition in development, plasticity and disease. Nat Rev Neurosci. 17:337-50.Outline•History – what took so long?•Subtypes & Pharmacology – rationale for complexity?•Subunit Structure – snapshot of the closed state•Physiology & Roles in Transmission•Specialization – alternate splicing and RNA editingHistoryearly evidence for excitation by glutamateHayashi (1954) Keio J. Medicine 3:183-192Curtis, Phillis, and Watkins (1960) J. Physiol. 150:656-682Krnjevic and Phillis (1963) J. Physiol. 165:274-304PharmacologyiGluR subtypesNMDA obligate heteromers GluN1 + GluN2A, B, C, or DCa permeable, voltage-dependent Mg block10-20% amino acid identity to non-NMDAnon NMDA - AMPA and kainatehomomeric or heteromericQ / R editing site in the pore-loop30-40% sequence identity AMPA GluA1, 2, 3 and 4 kainate GluK1, 2, 3, 4 and 5Rationale for complexity: integration1. permeability2. kinetics3. modulation 4. traffickingglutamate receptor pharmacologyNMDA AMPA kainateagonists glutamate glutamate glutamateNMDA AMPA kainateaspartate quisqualate domoatekainate (AMPA)domoate antagonists APV CNQX CNQXGYKI53655permeability Na, K, Ca Na, K (Ca) Na, K, (Ca)co-agonist glycinechannel Mgblock MK-801glutamateAMPANMDAkainateStructureSobolevsky et al. Nature (2009)orientation of KcsA versus iGluRLee et al. (2014)Karakas & Furukawa (2014)Meyerson et al., Nature, 2014AMPA Receptor Cryo-Electron MicroscopyMeyerson et al., Nature, 2014Closed ActivatedDesensitizedPhysiologyI-V relation for whole cell current through NMDA receptorswith Mg2+without Mg2+Nowak et al., 1984Voltage-dependent block of NMDA receptor single channels by Mg2+Nowak and Ascher, 1988glycine is a co-agonist at NMDA receptorsJohnson and Ascher, 1987agonist-dependent desensitization of AMPA receptorsPatneau and Mayer, 1991kainate desensitizes kainate receptorsHuettner, 1990I-V relations for the peak and decay phaseHestrin et al., 1990APV blocks the slow component of transmissionHestrin et al., 1990CNQX blocks the fast componentHestrin et al., 1990voltage-dependent block by Mg2+ Hestrin et al., 1990Why is the NMDA receptor-mediated component slow?Lester et al., 1990brief pulses of glutamate elicit prolonged burstsLester et al., 1990SpecializationAlternate splicing can alter gating, modulation and trafficking•Flip/flop 38 amino acid modules in the S2 loop that control gating kinetics•Cytoplasmic sites for post-translational modification and binding to cytosolic proteins depend on C-terminal splicingsplicing and editingFlip/flop splicing alters desensitization kineticsSommer et al., 1990Mosbacher et al., 1994C-tail splicing alters modulation and traffickingBredt and Nicoll, 2003Chung et al., 2000Bredt and Nicoll, 2003RNA Editing can alter permeation and gating•Q/R site in GluA2 and GluK1 & 2 controls permeation, polyamine block and lipid modulation•R/G site in GluA2, 3 & 4 just before flip/flop splice module affects kinetics of desensitizationadenosine deaminaseMet Gln GlnAUG CAG CAAMet Arg GlnAUG CIG CAAintronic hairpins define the editing siteSeeburg et al., 1998Q/R site RNA editing regulates permeationQ/R site RNA editing determines polyamine block and fatty acid modulationGluK2(Q) GluK2(R)Wilding et al., 2005; 2008differences in EPSC time courseTrussell, 1999summary•Ionotropic glutamate receptors mediate fast excitatory transmission throughout the CNS•Structural diversity allows for control of permeation, kinetics, modulation and trafficking•AMPA and NMDA receptors are the major postsynaptic receptors; kainate receptors can be pre- or postsynaptic•High calcium permeability and voltage-dependent block by magnesium underlie the role of NMDA receptors in controlling synaptic plasticity•Insertion and removal of AMPA receptors is a major determinant of synaptic