Kainate receptor modulation by NETO2

TL;DR

This study reveals the structural basis of how Neto2 modulates kainate receptor gating and rectification through cryo-EM structures, showing variable stoichiometry and specific interactions with GluK2.

Contribution

The paper provides the first cryo-EM structures of GluK2-Neto2 complexes in different states, elucidating the molecular mechanisms of Neto2 regulation of KARs.

Findings

Neto2 binds to specific faces of GluK2, influencing gating kinetics.

Variable stoichiometry of Neto2 association with GluK2 was observed.

Neto2's transmembrane helix interacts near the selectivity filter, affecting rectification.

Abstract

Glutamate-gated kainate receptors (KARs) are ubiquitous in the central nervous system of vertebrates, mediate synaptic transmission on post-synapse, and modulate transmitter release on pre-synapse. In the brain, the trafficking, gating kinetics, and pharmacology of KARs are tightly regulated by Neuropilin and tolloid-like proteins (Netos). Here we report cryo-EM structures of homo-tetrameric GluK2 in complex with Neto2 at inhibited and desensitized states, illustrating variable stoichiometry of GluK2-Neto2 complexes, with one or two Neto2 subunits associate with the GluK2. We find that Neto2 accesses only two broad faces of KARs, intermolecularly crosslinking the lower-lobe of ATDA/C, upper-lobe of LBDB/D, and lower-lobe of LBDA/C, illustrating how Neto2 regulates receptor-gating kinetics. The transmembrane helix of Neto2 is positioned proximal to the selectivity filter and competes with the amphiphilic H1-helix after M4 for interacting with an ICD formed by the M1-M2 linkers of the receptor, revealing how rectification is regulated by Neto2.