Research Departments & Organizations
We are interested in understanding how the structure of glutamate receptors determines their kinetic behavior. A combination of patch-clamp recording of macroscopic and single-channel currents and X-ray crystallography is employed to elucidate the major conformational changes that translate neurotransmitter binding into ion channel opening and receptor desensitization. Experimental and simulation studies are designed to determine the role of receptor kinetics in shaping synaptic transmission in the brain.
Specialized Terms: Glutamate receptors
Extensive Research Description
Ionotropic glutamate receptors (iGluRs) are protein complexes that form an ion channel in the cell membrane and localize to synapses where they are opened in response to glutamate binding. About 75% of the 100 trillion synaptic connections in the mammalian brain use glutamate-gated ion channels to evoke EPSCs in the postsynaptic cell and human synapses can faithfully follow presynaptic firing at rates of hundreds of action potentials per second. Our lab uses a combination of fast, piezoelectric-controlled, glutamate application to outside-out membrane patches and analysis of data from single receptor molecules to mimic synaptic transmission and study the kinetics of iGluRs.
Over the past decade, often in collaboration with Susumu Tomita (Yale), much of our work has been on modulation of iGluR gating by auxiliary subunits. We showed that the type I TARP stargazin (γ‑2) modulates both ensemble and single-channel currents through AMPARs via protein-protein interactions that depend on its first extracellular domain; showed that the four type I TARPs (Transmembrane AMPA Receptor Proteins) comprise two subfamilies (γ‑2, γ-3 and γ-4, γ-8) which lower the activation energy for channel opening and modulate synaptic currents to different extents. Together with the Tomita lab, we identified the first auxiliary subunit for kainate receptors (Neto2) and showed that it modulated kainate receptor function by slowing entry into desensitization and speeding recovery from it.
Recent work on TARPs demonstrated that TARP modulation of AMPA receptor gating is dynamic and altered by receptor stimulation; the physical interaction of TARPs with pore-forming subunits alters the conformation of the iGluR ligand-binding domain; and TARPs promote a unique gating mode, characterized by long bursts of openings to the largest open levels, that underlies the slow exponential component in the decays of ensemble currents, a feature that is the hallmark of TARP modulation. In addition to our ongoing work with the Tomita lab, we have active collaborations with the laboratories of Vasanthi Jayaraman (UT Houston), Flora Vaccarino (Yale), and Céline Auger (Univ Paris).
Train stimulation of parallel fibre to Purkinje cell inputs reveals two populations of synaptic responses with different receptor signatures.
Devi SP, Howe JR, Auger C. Train stimulation of parallel fibre to Purkinje cell inputs reveals two populations of synaptic responses with different receptor signatures. The Journal Of Physiology 2016, 594:3705-27. 2016
Modulation of non-NMDA receptor gating by auxiliary subunits.
Howe JR. Modulation of non-NMDA receptor gating by auxiliary subunits. The Journal Of Physiology 2015, 593:61-72. 2015
FOXG1-Dependent Dysregulation of GABA/Glutamate Neuron Differentiation in Autism Spectrum Disorders.
Mariani J, Coppola G, Zhang P, Abyzov A, Provini L, Tomasini L, Amenduni M, Szekely A, Palejev D, Wilson M, Gerstein M, Grigorenko EL, Chawarska K, Pelphrey KA, Howe JR, Vaccarino FM. FOXG1-Dependent Dysregulation of GABA/Glutamate Neuron Differentiation in Autism Spectrum Disorders. Cell 2015, 162:375-390. 2015
Stargazin promotes closure of the AMPA receptor ligand-binding domain.
MacLean DM, Ramaswamy SS, Du M, Howe JR, Jayaraman V. Stargazin promotes closure of the AMPA receptor ligand-binding domain. The Journal Of General Physiology 2014, 144:503-12. 2014
Auxiliary proteins promote modal gating of AMPA- and kainate-type glutamate receptors.
Zhang W, Devi SP, Tomita S, Howe JR. Auxiliary proteins promote modal gating of AMPA- and kainate-type glutamate receptors. The European Journal Of Neuroscience 2014, 39:1138-47. 2014