SH006 - Conformational Landscape and TARP-2 Modulation of GluA4 AMPA Receptors

SH006

Conformational Landscape and TARP-2 Modulation of GluA4 AMPA Receptors

C. Vega-Gutiérrez^1,^2,*, J. Picañol-Parraga³, I. Sánchez-Valls^1,², V. D. P. Ribón-Fuster^1,², D. Soto³, B. Herguedas^1,²

¹Institute for Biocomputation and Physics of Complex Systems-University of Zaragoza, ²Advanced Microscopy Laboratory-University of Zaragoza, Zaragoza, ³Laboratory of Neurophysiology, Institute of Neurosciences, University of Barcelona, Barcelona, Spain

Rationale: AMPA receptors (AMPARs) mediate fast excitatory neurotransmission in the central nervous system and are essential for synaptic plasticity. Among AMPAR subtypes (GluA1-GluA4), GluA4-containing receptors are relatively unexplored, and their structural and functional properties remain poorly understood.

Methods: GluA4-containing AMPA receptors were produced by infecting mammalian suspension cells with baculovirus constructs encoding the receptor, either in isolation or in complex with the auxiliary subunit TARP-γ2. The expressed membrane proteins were purified and used for cryo-electron microscopy (cryo-EM) to capture multiple conformational states along the gating cycle in the presence of different ligands. Electrophysiology and cross-linking assays were performed to assess receptor gating and subunit-dependent modulation, providing complementary functional insights.

Results: Under resting conditions, GluA4-containing AMPA receptors adopt a Y-shaped dimer-of-dimers arrangement, similar to GluA2-containing AMPARs [1]. However, GluA4 exhibits greater conformational flexibility, undergoing substantial structural rearrangements throughout the gating cycle. Transient disruption of dimer interfaces within the ligand-binding domain (LBD) was observed in the desensitized state [1], similar to GluA1 and GluA3. This disruption is markedly stronger in the absence of TARP-γ2, accelerating GluA4 entry into desensitization. Furthermore, a previously unrecognized regulatory site was identified, mediating TARP-γ2-dependent modulation of receptor function [1].

Conclusions: These findings provide a structural and functional framework to understand the architecture of GluA4 receptors and the mechanisms underlying their gating, as well as the role of auxiliary subunits in modulating AMPA receptor behavior.

References: 1 Vega-Gutiérrez C, Picañol-Parraga J, Sánchez-Valls I, Ribón-Fuster VP, Soto D, Herguedas B (2025) Nature Structural and Molecular Biology, Online ahead of print.

Disclosure of Interest: None declared