Structural basis of gating modulation of Kv4 channel complexes

Abstract

Modulation of voltage-gated potassium (Kv) channels by auxiliary subunits is central to the physiological function of channels in the brain and heart1,2. Native Kv4 tetrameric channels form macromolecular ternary complexes with two auxiliary β-subunits—intracellular Kv channel-interacting proteins (KChIPs) and transmembrane dipeptidyl peptidase-related proteins (DPPs)—to evoke rapidly activating and inactivating A-type currents, which prevent the backpropagation of action potentials1–5. However, the modulatory mechanisms of Kv4 channel complexes remain largely unknown. Here we report cryo-electron microscopy structures of the Kv4.2–DPP6S–KChIP1 dodecamer complex, the Kv4.2–KChIP1 and Kv4.2–DPP6S octamer complexes, and Kv4.2 alone. The structure of the Kv4.2–KChIP1 complex reveals that the intracellular N terminus of Kv4.2 interacts with its C terminus that extends from the S6 gating helix of the neighbouring Kv4.2 subunit. KChIP1 captures both the N and the C terminus of Kv4.2. In consequence, KChIP1 would prevent N-type inactivation and stabilize the S6 conformation to modulate gating of the S6 helices within the tetramer. By contrast, unlike the reported auxiliary subunits of voltage-gated channel complexes, DPP6S interacts with the S1 and S2 helices of the Kv4.2 voltage-sensing domain, which suggests that DPP6S stabilizes the conformation of the S1–S2 helices. DPP6S may therefore accelerate the voltage-dependent movement of the S4 helices. KChIP1 and DPP6S do not directly interact with each other in the Kv4.2–KChIP1–DPP6S ternary complex. Thus, our data suggest that two distinct modes of modulation contribute in an additive manner to evoke A-type currents from the native Kv4 macromolecular complex.

Cryo-EM structure of the human Kv3.1 channel reveals gating control by the cytoplasmic T1 domain

“…In the Kv4 subfamily, however, an analogous stabilizing interaction could exist because the R332 residue in the S4/S5 linker is conserved. This is confirmed by the recent full-length Kv4.2 structure 43 which indeed shows a salt bridge between the corresponding R6 (R305) carbonyl oxygen and the side chain of R311 in the S4/S5 linker (Fig. S12g ).…”

“…Of note, T1/C-terminal interactions have been suggested for other Kv channels, including Kv2.1 42 and Kv4.1 27 . While the current work was under review, structures of full-length human Kv4.2 were published 43 , confirming the close proximity of T1 and the C-terminal end of S6T, which are connected via an inter-subunit salt bridge located near α6 of Kv4.2 (Fig. S6c, d ).…”

“…S10a and Supplementary Results). Similar densities are also present in the open pores of the Kv1.2/2.1 and Kv4.2 structures determined by cryo-EM 28 , 43 .…”

The Role of Vti1a in Biological Functions and Its Possible Role in Nervous System Disorders

“…The K channel interacting proteins (KChIPs) belong to the neuronal calcium receptor family and assemble into a natural complex with the α subunit of the voltage-gated Kv4 potassium channel, encoding A-type K + current to regulate neuronal excitability ( Bähring, 2018 ; Kise et al, 2021 ). The specific assembly contributes to forming and stabilizing voltage-gated potassium channel tetramers and increases channel transport to the cell membrane surface ( Alfaro-Ruíz et al, 2020 ).…”

Mechanisms Underlying C-type Inactivation in Kv Channels: Lessons From Structures of Human Kv1.3 and Fly Shaker-IR Channels

“…High-resolution structures determined by X-ray crystallography or cryogenic-electron microscopy (cryo-EM) have provided deep molecular insights into the closed and open conformations of Kv channels ( Zhou et al, 2001 ; Long et al, 2005 ; Alabi et al, 2007 ; Long et al, 2007 ; Jensen et al, 2010 ; Jensen et al, 2012 ; Kim and Nimigean, 2016 ; Whicher and Mackinnon, 2016 ; Pau et al, 2017 ; Sun and Mackinnon, 2017 ; Wang and Mackinnon, 2017 ; Sun and Mackinnon, 2020 ; Kise et al, 2021 ). The description below is based on the structure of the rat Kv1.2-Kv2.1 paddle chimera (KvChim) (PDB: 2R9R) ( Figures 1A,B ).…”