The His-Gly motif of acid-sensing ion channels resides in a reentrant 'loop' implicated in gating and ion selectivity
- University of California, San Francisco, United States
- Oregon Health and Science University, United States
Abstract
Acid-sensing ion channels (ASICs) are proton-gated members of the epithelial sodium channel/degenerin (ENaC/DEG) superfamily of ion channels and are expressed throughout the central and peripheral nervous systems. The homotrimeric splice variant ASIC1a has been implicated in nociception, fear memory, mood disorders and ischemia. Here we extract full-length chicken ASIC1 (cASIC1) from cell membranes using styrene maleic acid (SMA) copolymer, elucidating structures of ASIC1 channels in both high pH resting and low pH desensitized conformations by single-particle cryo-electron microscopy (cryo-EM). The structures of resting and desensitized channels reveal a reentrant loop at the amino terminus of ASIC1 that includes the highly conserved 'His-Gly' (HG) motif. The reentrant loop lines the lower ion permeation pathway and buttresses the 'Gly-Ala-Ser' (GAS) constriction, thus providing a structural explanation for the role of the His-Gly dipeptide in the structure and function of ASICs.
Data availability
The coordinates and associated cryo-EM map for the desensitized SMA-cASIC1a channel at pH 7.0 have been deposited in the Protein Data Bank and Electron Microscopy Data Bank under the accession codes 6VTK and EMD-21380, respectively. The coordinates and associated cryo-EM map for the resting SMA-cASIC1a channel at pH 8.0 have been deposited in the Protein Data Bank and Electron Microscopy Data Bank under the accession codes 6VTL and EMD-21381, respectively.
-
Structure of an acid-sensing ion channel solubilized by styrene maleic acid and in a desensitized state at low pHElectron Microscopy Data Bank, EMD-21380.
-
Structure of an acid-sensing ion channel solubilized by styrene maleic acid and in a resting state at high pHElectron Microscopy Data Bank, EMD-21381.
Article and author information
Author details
Funding
National Institute of Neurological Disorders and Stroke (5F31NS096782)
- Nate Yoder
National Institute of Neurological Disorders and Stroke (5R01NS038631)
- Eric Gouaux
National Institutes of Health (U24GM129539)
- Nate Yoder
National Institutes of Health (U24GM129547)
- Nate Yoder
National Institute of Diabetes and Digestive and Kidney Diseases (5T32DK007680)
- Nate Yoder
Tartar Trust
- Nate Yoder
ARCS Foundation
- Nate Yoder
Howard Hughes Medical Institute
- Eric Gouaux
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- László Csanády, Semmelweis University, Hungary
Version history
- Received: March 2, 2020
- Accepted: June 3, 2020
- Accepted Manuscript published: June 4, 2020 (version 1)
- Version of Record published: June 22, 2020 (version 2)
Copyright
© 2020, Yoder & Gouaux
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 3,226
- views
-
- 560
- downloads
-
- 66
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
The His-Gly motif of acid-sensing ion channels resides in a reentrant 'loop' implicated in gating and ion selectivity
eLife 9:e56527.
https://doi.org/10.7554/eLife.56527
Further reading
-
- Neuroscience
Tissue-clearing and labeling techniques have revolutionized brain-wide imaging and analysis, yet their application to clinical formalin-fixed paraffin-embedded (FFPE) blocks remains challenging. We introduce HIF-Clear, a novel method for efficiently clearing and labeling centimeter-thick FFPE specimens using elevated temperature and concentrated detergents. HIF-Clear with multi-round immunolabeling reveals neuron circuitry regulating multiple neurotransmitter systems in a whole FFPE mouse brain and is able to be used as the evaluation of disease treatment efficiency. HIF-Clear also supports expansion microscopy and can be performed on a non-sectioned 15-year-old FFPE specimen, as well as a 3-month formalin-fixed mouse brain. Thus, HIF-Clear represents a feasible approach for researching archived FFPE specimens for future neuroscientific and 3D neuropathological analyses.
-
- Neuroscience
Pavlovian fear conditioning has been extensively used to study the behavioral and neural basis of defensive systems. In a typical procedure, a cue is paired with foot shock, and subsequent cue presentation elicits freezing, a behavior theoretically linked to predator detection. Studies have since shown a fear conditioned cue can elicit locomotion, a behavior that - in addition to jumping, and rearing - is theoretically linked to imminent or occurring predation. A criticism of studies observing fear conditioned cue-elicited locomotion is that responding is non-associative. We gave rats Pavlovian fear discrimination over a baseline of reward seeking. TTL-triggered cameras captured 5 behavior frames/s around cue presentation. Experiment 1 examined the emergence of danger-specific behaviors over fear acquisition. Experiment 2 examined the expression of danger-specific behaviors in fear extinction. In total, we scored 112,000 frames for nine discrete behavior categories. Temporal ethograms show that during acquisition, a fear conditioned cue suppresses reward seeking and elicits freezing, but also elicits locomotion, jumping, and rearing - all of which are maximal when foot shock is imminent. During extinction, a fear conditioned cue most prominently suppresses reward seeking, and elicits locomotion that is timed to shock delivery. The independent expression of these behaviors in both experiments reveal a fear conditioned cue to orchestrate a temporally organized suite of behaviors.
