Gating intermediates reveal inhibitory role of the voltage sensor in a cyclic nucleotide-modulated ion channel.

TitleGating intermediates reveal inhibitory role of the voltage sensor in a cyclic nucleotide-modulated ion channel.
Publication TypeJournal Article
Year of Publication2022
AuthorsGao X, Schmidpeter PAM, Berka V, Durham RJ, Fan C, Jayaraman V, Nimigean CM
JournalNat Commun
Volume13
Issue1
Pagination6919
Date Published2022 Nov 14
ISSN2041-1723
KeywordsCyclic AMP, Cyclic Nucleotide-Gated Cation Channels, Ion Channel Gating, Ligands, Nucleotides, Cyclic
Abstract

Understanding how ion channels gate is important for elucidating their physiological roles and targeting them in pathophysiological states. Here, we used SthK, a cyclic nucleotide-modulated channel from Spirochaeta thermophila, to define a ligand-gating trajectory that includes multiple on-pathway intermediates. cAMP is a poor partial agonist for SthK and depolarization increases SthK activity. Tuning the energy landscape by gain-of-function mutations in the voltage sensor domain (VSD) allowed us to capture multiple intermediates along the ligand-activation pathway, highlighting the allosteric linkage between VSD, cyclic nucleotide-binding (CNBD) and pore domains. Small, lateral displacements of the VSD S4 segment were necessary to open the intracellular gate, pointing to an inhibitory VSD at rest. We propose that in wild-type SthK, depolarization leads to such VSD displacements resulting in release of inhibition. In summary, we report conformational transitions along the activation pathway that reveal allosteric couplings between key sites integrating to open the intracellular gate.

DOI10.1038/s41467-022-34673-z
Alternate JournalNat Commun
PubMed ID36376326
Grant ListGM122528 / / U.S. Department of Health & Human Services | NIH | National Institute of General Medical Sciences (NIGMS) /
GM124451 / / U.S. Department of Health & Human Services | NIH | National Institute of General Medical Sciences (NIGMS) /