
==== Front
bioRxiv
BIORXIV
bioRxiv
2692-8205
Cold Spring Harbor Laboratory

10.1101/2024.09.05.611422
preprint
1
Article
Temperature Sensitive Glutamate Gating of AMPA-subtype iGluRs
Kumar Mondal Anish http://orcid.org/0000-0002-3911-5644

Carrillo Elisa http://orcid.org/0000-0002-0419-395X

Jayaraman Vasanthi http://orcid.org/0000-0002-2686-7310

Twomey Edward C. http://orcid.org/0000-0002-1855-1586

07 9 2024
2024.09.05.611422https://creativecommons.org/licenses/by-nc-nd/4.0/ This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which allows reusers to copy and distribute the material in any medium or format in unadapted form only, for noncommercial purposes only, and only so long as attribution is given to the creator.
http://biorxiv.org/lookup/doi/10.1101/2024.09.05.611422
nihpp-2024.09.05.611422.pdf
Summary

Ionotropic glutamate receptors (iGluRs) are tetrameric ligand-gated ion channels that mediate the majority of excitatory neurotransmission 1 . iGluRs are gated by glutamate, where upon glutamate binding, they open their ion channels to enable cation influx into post-synaptic neurons, initiating signal transduction 2 . The structural mechanism of iGluR gating by glutamate has been extensively studied in the context of positive allosteric modulators (PAMs) 3–15 . A fundamental question has remained – are the PAM activated states of iGluRs representative of glutamate gating in the absence of PAMs? Here, using the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid subtype iGluR (AMPAR) we show that glutamate gating is unique from gating in the presence of PAMs. We demonstrate that glutamate gating is temperature sensitive, and through temperature-resolved cryo-electron microscopy (cryo-EM), capture all major glutamate gating states. Physiological temperatures augment channel activation and conductance. Activation by glutamate initiates ion channel opening that involves all ion channel helices hinging away from the pores axis in a motif that is conserved across all iGluRs. Desensitization occurs when the local dimer pairs decouple and enables closure of the ion channel below through restoring the channel hinges and refolding the channel gate. Our findings define how glutamate gates iGluRs, provide foundations for therapeutic design, and point to iGluR gating being temperature sensitive.
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pmc
