Numerous endogenous and synthetic ligands modulate NMDA receptor activities and are potential candidates for therapeutic intervention in a number of neurologic disorders. To date, empirical attempts to control en masse NMDA receptor-mediated fluxes have had only modest success in the clinic, mainly due to inadequate understanding of the mechanisms governing the allosteric control of NMDA receptor activities and of the specific roles played by these activities in brain physiology and pathology. Over the previous funding period the objective has been to delineate the mechanisms by which endogenous modulators (protons, zinc/ifenprodil, glycine) affect NMDA receptor gating dynamics and thus control the macroscopic response relevant to synaptic signaling. Over the next funding period the objective is to delineate the intracellular protein motions that constitute the NMDA receptor activation. The general approach is to capitalize on the recently solved atomic-resolution structure for a GluA2 tetrameric receptor, a NMDA receptor homologue and our growing expertise on NMDA receptor gating modulation. We will introduce mutations to perturb (increase and decrease) the relative mobility of NMDA receptor structural modules and will delineate the accompanying changes in reaction mechanism by kinetic analyses of single-molecule signals. Further, we will explore the time course of macroscopic responses obtained from receptors with restricted or enhanced internal motions to better understand how specific structural features support the unique biological functions played by NMDA receptors in brain physiology and pathology. Overall this work will provide critical information about structural correlates of NMDA receptor activation and will integrate the currently isolated structural and kinetic models of gating. Given that glutamate receptors mediate more than 90% of excitatory transmission in brain and NMDA receptors are critical to many fundamental brain functions, knowledge generated by the proposed experiments is likely to have wide impact on the fields of neurotransmission and neuromodulation.

Public Health Relevance

NMDA receptors mediate fundamental brain processes and are therapeutic target for a number of neuropathologies including stroke, chronic neurodegeneration, addiction and pain. Results from this application will provide needed information about structural correlates of NMDA receptor activation and by integrating structural and kinetic models of gating will assist in the rational design of pharmacologic approaches to address acute and chronic neuropathies.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Biophysics of Neural Systems Study Section (BPNS)
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Silberberg, Shai D
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State University of New York at Buffalo
Schools of Medicine
United States
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Cummings, Kirstie A; Belin, Sophie; Popescu, Gabriela K (2017) Residues in the GluN1 C-terminal domain control kinetics and pharmacology of GluN1/GluN3A N-methyl-d-aspartate receptors. Neuropharmacology 119:40-47
Iacobucci, Gary J; Popescu, Gabriela K (2017) Resident Calmodulin Primes NMDA Receptors for Ca2+-Dependent Inactivation. Biophys J 113:2236-2248
Iacobucci, Gary J; Popescu, Gabriela K (2017) NMDA receptors: linking physiological output to biophysical operation. Nat Rev Neurosci 18:236-249
Cummings, Kirstie A; Popescu, Gabriela K (2016) Protons Potentiate GluN1/GluN3A Currents by Attenuating Their Desensitisation. Sci Rep 6:23344
Borschel, William F; Cummings, Kirstie A; Tindell, LeeAnn K et al. (2015) Kinetic contributions to gating by interactions unique to N-methyl-D-aspartate (NMDA) receptors. J Biol Chem 290:26846-55
Cummings, Kirstie A; Popescu, Gabriela K (2015) Glycine-dependent activation of NMDA receptors. J Gen Physiol 145:513-27
Paganelli, Meaghan A; Popescu, Gabriela K (2015) Actions of bupivacaine, a widely used local anesthetic, on NMDA receptor responses. J Neurosci 35:831-42
Popescu, Gabriela K (2015) Zinc transporter found attached to N-methyl-D-aspartate receptors. J Neurochem 132:155-8
Popescu, Gabriela K (2015) Accessories assist AMPA receptors to close pockets. J Gen Physiol 145:17-21
Maki, Bruce A; Popescu, Gabriela K (2014) Extracellular Ca(2+) ions reduce NMDA receptor conductance and gating. J Gen Physiol 144:379-92

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