Protonation controls ASIC1a activity via coordinated movements in multiple domains.

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Version: Final published version
Serval ID
serval:BIB_7DDBEAA9023B
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Protonation controls ASIC1a activity via coordinated movements in multiple domains.
Journal
Journal of General Physiology
Author(s)
Bonifacio G., Lelli C.I., Kellenberger S.
ISSN
1540-7748 (Electronic)
ISSN-L
0022-1295
Publication state
Published
Issued date
2014
Volume
143
Number
1
Pages
105-118
Language
english
Abstract
Acid-sensing ion channels (ASICs) are neuronal Na(+)-conducting channels activated by extracellular acidification. ASICs are involved in pain sensation, expression of fear, and neurodegeneration after ischemic stroke. Functional ASICs are composed of three identical or homologous subunits, whose extracellular part has a handlike structure. Currently, it is unclear how protonation of residues in extracellular domains controls ASIC activity. Knowledge of these mechanisms would allow a rational development of drugs acting on ASICs. Protonation may induce conformational changes that control the position of the channel gate. We used voltage-clamp fluorometry with fluorophores attached to residues in different domains of ASIC1a to detect conformational changes. Comparison of the timing of fluorescence and current signals identified residues involved in movements that preceded desensitization and may therefore be associated with channel opening or early steps leading to desensitization. Other residues participated in movements intimately linked to desensitization and recovery from desensitization. Fluorescence signals of all mutants were detected at more alkaline pH than ionic currents. Their midpoint of pH dependence was close to that of steady-state desensitization, whereas the steepness of the pH fluorescence relationship was closer to that of current activation. A sequence of movements was observed upon acidification, and its backward movements during recovery from desensitization occurred in the reverse order, indicating that the individual steps are interdependent. Furthermore, the fluorescence signal of some labeled residues in the finger domain was strongly quenched by a Trp residue in the neighboring β-ball domain. Upon channel activation, their fluorescence intensity increased, indicating that the finger moved away from the β ball. This extensive analysis of activity-dependent conformational changes in ASICs sheds new light on the mechanisms by which protonation controls ASIC activity.
Pubmed
Web of science
Open Access
Yes
Create date
24/01/2014 18:37
Last modification date
20/10/2020 8:19
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