Redox regulation of KV7 channels through EF3 hand of calmodulin

Eider Nuñez, Frederick Jones, Arantza Muguruza-Montero, Janire Urrutia, Alejandra Aguado, Covadonga Malo, Ganeko Bernardo-Seisdedos, Carmen Domene, Oscar Millet, Nikita Gamper, Alvaro Villarroel

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Article numbere81961
Publication statusPublished - 20 Feb 2023

Bibliographical note

Funding Information:
CM was supported by the Basque Government through a Basque Excellence Research Center (BERC) and JU was partially supported by BERC funds. CD thanks PRACE for awarding access to computational resources in CSCS, the Swiss National Supercomputing Service, in the 17th and 20th Project Access Calls. We acknowledge CESGA and CSIC for granting us access to computational resources to FinisTerrae II supercomputer.

Data availability
All data generated or analysed during this study are included in the manuscript and supporting file.

ASJC Scopus subject areas

  • Neuroscience(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)


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