Structure of a CLC chloride ion channel by cryo-electron microscopy

The epithelial sodium channel (ENaC), a member of the ENaC/DEG superfamily, regulates Na+ and water homeostasis. ENaCs assemble as heterotrimeric channels that harbor protease-sensitive domains critical for gating the channel. Here, we present the structure of human ENaC in the uncleaved state determined by single-particle cryo-electron microscopy. The ion channel is composed of a large extracellular domain and a narrow transmembrane domain. The structure reveals that ENaC assembles with a 1:1:1 stoichiometry of α:β:γ subunits arranged in a counter-clockwise manner. The shape of each subunit is reminiscent of a hand with key gating domains of a ‘finger’ and a ‘thumb.’ Wedged between these domains is the elusive protease-sensitive inhibitory domain poised to regulate conformational changes of the ‘finger’ and ‘thumb’; thus, the structure provides the first view of the architecture of inhibition of ENaC.

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Cryo-electron microscopy revealed TACAN is extensively and specifically associated with membrane lipids

10.1101/2021.10.11.463882 ◽

2021 ◽

Author(s):

Zhen Wang ◽

Fengying Fan ◽

Lili Dong ◽

Qingxia Wang ◽

Yue Zhou ◽

...

Keyword(s):

Electron Microscopy ◽

Ion Channel ◽

Membrane Lipids ◽

The Body ◽

Mechanical Hyperalgesia ◽

Transmembrane Helices ◽

Lipid Core ◽

Cryo Electron Microscopy ◽

Mechanosensitive Ion Channel

TACAN is not a mechanosensitive ion channel but significantly linked to the mechanical hyperalgesia. In this study, we show that the human TACAN is a homodimer with each monomer consisting of a body, a spring and a blade domains. The body domain contains six transmembrane helices that forms an independent channel. The spring domain adapts a loop-helix-loop configuration with the helix running within and parallel to the membrane. The blade domain is composed of two cytoplasmic helices. In addition, we found that all the helices of the body and the spring domains are specifically associated with membrane lipids. Particularly, a lipid core, residing within a cavity formed by the two body and spring domains, contacts with the helices from the body and spring domains and extends to reach two symmetrically arranged lipid clusters. These results extremely imply that the membrane lipids coordinate with the membrane-embedded protein to sense and transduce the mechanic signal.

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Heterogeneous Populations of Ligand-Gated Ion Channel, GLIC, Revealed by Cryo-Electron Microscopy and Simulations

Biophysical Journal ◽

10.1016/j.bpj.2020.11.1321 ◽

2021 ◽

Vol 120 (3) ◽

pp. 192a

Author(s):

Urska Rovsnik ◽

Yuxuan Zhuang ◽

Bjorn Forsberg ◽

Marta Carroni ◽

Linnea Axelsson ◽

...

Keyword(s):

Electron Microscopy ◽

Ion Channel ◽

Heterogeneous Populations ◽

Cryo Electron Microscopy

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Structure-based identification and characterisation of novel inhibitors of KNa1.1 potassium channels, a stratified target for KCNT1-related epilepsy

10.1101/779975 ◽

2019 ◽

Author(s):

Bethan A. Cole ◽

Rachel M. Johnson ◽

Hattapark Dejakaisaya ◽

Nadia Pilati ◽

Colin W.G. Fishwick ◽

...

Keyword(s):

Electron Microscopy ◽

Drug Discovery ◽

Ion Channel ◽

Potassium Channel ◽

Mutational Analysis ◽

Drug Resistant ◽

Channel Activity ◽

Epileptic Encephalopathies ◽

Cytotoxicity Assays ◽

Cryo Electron Microscopy

AbstractSeveral types of drug-resistant epileptic encephalopathies of infancy have been associated with mutations in the KCNT1 gene, which encodes the sodium-activated potassium channel subunit KNa1.1. These mutations are commonly gain-of-function, increasing channel activity, therefore inhibition by drugs is proposed as a stratified approach to treat disorders. To date, quinidine therapy has been trialled with several patients, but mostly with unsuccessful outcomes, which has been linked to its low potency and lack of specificity. Here we describe the use of a cryo-electron microscopy-derived KNa1.1 structure and mutational analysis to identify the quinidine biding site and identified novel inhibitors that target this site using computational methods. We describe six compounds that inhibit KNa1.1 channels with low- and sub-micromolar potencies, likely through binding in the intracellular pore vestibule. In preliminary hERG inhibition and cytotoxicity assays, two compounds showed little effect. These compounds may provide starting points for the development of novel pharmacophores for KNa1.1 inhibition, with the view to treating KCNT1-associated epilepsy and, with their potencies higher than quinidine, could become key tool compounds to further study this channel. Furthermore, this study illustrates the potential for utilising cryo-electron microscopy in ion channel drug discovery.

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Cryo-electron microscopy structure of the TRPV2 ion channel

Nature Structural & Molecular Biology ◽

10.1038/nsmb.3159 ◽

2016 ◽

Vol 23 (2) ◽

pp. 180-186 ◽

Cited By ~ 177

Author(s):

Lejla Zubcevic ◽

Mark A Herzik ◽

Ben C Chung ◽

Zhirui Liu ◽

Gabriel C Lander ◽

...

Keyword(s):

Electron Microscopy ◽

Ion Channel ◽

Cryo Electron Microscopy

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Cryo‐electron microscopy structure of CLHM1 ion channel from Caenorhabditis elegans

Protein Science ◽

10.1002/pro.3904 ◽

2020 ◽

Vol 29 (8) ◽

pp. 1803-1815

Author(s):

Weixin Yang ◽

Youwang Wang ◽

Jianli Guo ◽

Lingli He ◽

Ye Zhou ◽

...

Keyword(s):

Electron Microscopy ◽

Caenorhabditis Elegans ◽

Ion Channel ◽

Cryo Electron Microscopy

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Characterizing Functional States of a Model Ligand-Gated Ion Channel by Cryo-Electron Microscopy

Biophysical Journal ◽

10.1016/j.bpj.2018.11.885 ◽

2019 ◽

Vol 116 (3) ◽

pp. 160a

Author(s):

Urska Rovsnik ◽

Rebecca Howard ◽

Bjorn Forsberg ◽

Marta Carroni ◽

Erik Lindahl

Keyword(s):

Electron Microscopy ◽

Ion Channel ◽

Cryo Electron Microscopy ◽

Functional States

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Characterization of the dynamic resting state of a pentameric ligand-gated ion channel by cryo-electron microscopy and simulations

10.1101/2020.06.19.161356 ◽

2020 ◽

Author(s):

U Rovšnik ◽

Y Zhuang ◽

L Axelsson ◽

BO Forsberg ◽

V Lim ◽

...

Keyword(s):

Electron Microscopy ◽

Ion Channel ◽

Resting State ◽

Structural Data ◽

Cryo Electron Microscopy ◽

Electrochemical Signal ◽

Moderate Resolution ◽

Functional States ◽

Dynamics Simulations

AbstractLigand-gated ion channels are critical mediators of electrochemical signal transduction across evolution. Biophysical and pharmacological development in this family relies on high-quality structural data in multiple, subtly distinct functional states. However, structural data remain limited, particularly for the unliganded or resting state. Here we report cryo-electron microscopy structures of the Gloeobacter violaceus ligand-gated ion channel (GLIC) under resting and activating conditions (neutral and low pH). Parallel models were built either manually or using recently developed density-guided molecular simulations. The moderate resolution of resting-state reconstructions, particularly in the extracellular domain, was improved under activating conditions, enabling the visualization of residues at key subunit interfaces including loops B, C, F, and M2–M3. Combined with molecular dynamics simulations, the cryo-electron microscopy structures at different pH describe a heterogeneous population of closed channels, with activating conditions condensing the closed-channel energy landscape on a pathway towards gating.

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New challenges to image processing posed by cryo-Electron microscopy of single particles

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100086416 ◽

1991 ◽

Vol 49 ◽

pp. 422-423

Author(s):

Joachim Frank

Keyword(s):

Electron Microscopy ◽

Phase Contrast ◽

Particle Orientation ◽

Single Particles ◽

Contrast Transfer Function ◽

Virtual Absence ◽

Cryo Electron Microscopy ◽

Spatial Frequencies ◽

New Challenges ◽

Particle Images

Compared with images of negatively stained single particle specimens, those obtained by cryo-electron microscopy have the following new features: (a) higher “signal” variability due to a higher variability of particle orientation; (b) reduced signal/noise ratio (S/N); (c) virtual absence of low-spatial-frequency information related to elastic scattering, due to the properties of the phase contrast transfer function (PCTF); and (d) reduced resolution due to the efforts of the microscopist to boost the PCTF at low spatial frequencies, in his attempt to obtain recognizable particle images.

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