Mapping the Interaction Sites between AMPA Receptors and TARPs Reveals a Role for the Receptor N-Terminal Domain in Channel Gating

Ingo H Greger,Karolina Krol,Stuart G Cull-Candy,Ondrej Cais,Beatriz Herguedas,Mark Farrant

doi:10.1016/j.celrep.2014.09.029

Ingo H Greger, Karolina Krol + Show 4 more

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https://doi.org/10.1016/j.celrep.2014.09.029

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Abstract

SummaryAMPA-type glutamate receptors (AMPARs) mediate fast neurotransmission at excitatory synapses. The extent and fidelity of postsynaptic depolarization triggered by AMPAR activation are shaped by AMPAR auxiliary subunits, including the transmembrane AMPAR regulatory proteins (TARPs). TARPs profoundly influence gating, an effect thought to be mediated by an interaction with the AMPAR ion channel and ligand binding domain (LBD). Here, we show that the distal N-terminal domain (NTD) contributes to TARP modulation. Alterations in the NTD-LBD linker result in TARP-dependent and TARP-selective changes in AMPAR gating. Using peptide arrays, we identify a TARP interaction region on the NTD and define the path of TARP contacts along the LBD surface. Moreover, we map key binding sites on the TARP itself and show that mutation of these residues mediates gating modulation. Our data reveal a TARP-dependent allosteric role for the AMPAR NTD and suggest that TARP binding triggers a drastic reorganization of the AMPAR complex.

Highlights

amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors (AMPARs) mediate fast excitatory transmission and are crucial for various forms of synaptic plasticity (Bredt and Nicoll, 2003; Cull-Candy et al, 2006)
We recreated the modifications that had been used in the GluA2 crystal structure, GluA2cryst (Sobolevsky et al, 2009), as this provided direct structural information on the packing between N-terminal domain (NTD) and ligand binding domain (LBD)
The NTD-LBD Linker Modulates Recovery from Desensitization We investigated whether the NTD linker has a wider role in AMPAR function and could affect other aspects of gating that are regulated by transmembrane AMPAR regulatory proteins (TARPs)

Summary

Introduction

AMPA-type glutamate receptors (AMPARs) mediate fast excitatory transmission and are crucial for various forms of synaptic plasticity (Bredt and Nicoll, 2003; Cull-Candy et al, 2006) Their varied kinetic behavior (Mosbacher et al, 1994), as well as their calcium permeability and voltage-dependent block by polyamines (Cull-Candy et al, 2006; Geiger et al, 1995), varies between brain regions and appear to be adapted to the specific function of a given circuit (Jonas, 2000; Trussell, 1998). TARP-like modulation of AMPARs has been seen in invertebrates (Walker et al, 2006; Wang et al, 2008) and appears highly conserved

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