Redox regulation of KV7 channels through EF3 hand of calmodulin

Nuñez, Eider, Jones, Frederick ORCID: https://orcid.org/0000-0003-1636-0054, Muguruza-Montero, Arantza, Urrutia, Janire ORCID: https://orcid.org/0000-0002-8546-292X, Aguado, Alejandra, Malo, Covadonga, Bernardo-Seisdedos, Ganeko, Domene, Carmen ORCID: https://orcid.org/0000-0001-7115-4232, Millet, Oscar ORCID: https://orcid.org/0000-0001-8748-4105, Gamper, Nikita ORCID: https://orcid.org/0000-0001-5806-0207 and Villarroel, Alvaro ORCID: https://orcid.org/0000-0003-1096-7824 (2023) Redox regulation of KV7 channels through EF3 hand of calmodulin. eLife, 12. e81961. ISSN 2050-084X

Preview

Published Version Available under License Creative Commons Attribution. Download (1MB) | Preview

Abstract

Neuronal KV7 channels, important regulators of cell excitability, are among the most sensitive proteins to reactive oxygen species. The S2S3 linker of the voltage sensor was reported as a site-mediating redox modulation of the channels. Recent structural insights reveal potential interactions between this linker and the Ca2+-binding loop of the third EF-hand of calmodulin (CaM), which embraces an antiparallel fork formed by the C-terminal helices A and B, constituting the calcium responsive domain (CRD). We found that precluding Ca2+ binding to the EF3 hand, but not to EF1, EF2, or EF4 hands, abolishes oxidation-induced enhancement of KV7.4 currents. Monitoring FRET (Fluorescence Resonance Energy Transfer) between helices A and B using purified CRDs tagged with fluorescent proteins, we observed that S2S3 peptides cause a reversal of the signal in the presence of Ca2+ but have no effect in the absence of this cation or if the peptide is oxidized. The capacity of loading EF3 with Ca2+ is essential for this reversal of the FRET signal, whereas the consequences of obliterating Ca2+ binding to EF1, EF2, or EF4 are negligible. Furthermore, we show that EF3 is critical for translating Ca2+ signals to reorient the AB fork. Our data are consistent with the proposal that oxidation of cysteine residues in the S2S3 loop relieves KV7 channels from a constitutive inhibition imposed by interactions between the EF3 hand of CaM which is crucial for this signaling.