Redox regulation of KV7 channels through EF3 hand of calmodulin

• Published in: eLife Vol. 12
• Main Authors: Nuñez, Eider, Jones, Frederick, Muguruza-Montero, Arantza, Urrutia, Janire, Aguado, Alejandra, Malo, Covadonga, Bernardo-Seisdedos, Ganeko, Domene, Carmen, Millet, Oscar, Gamper, Nikita, Villarroel, Alvaro
• Format: Journal Article
• Language: English
• Published: eLife Sciences Publications, Ltd 20-02-2023; eLife Sciences Publications Ltd
• Subjects: calcium; calmodulin; Cell Biology; EF-hand; KCNQ; Neuroscience; redox; signal transduction
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.81961

Neuronal K
V
7 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 Ca
2+
-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 Ca
2+
binding to the EF3 hand, but not to EF1, EF2, or EF4 hands, abolishes oxidation-induced enhancement of K
V
7.4 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 Ca
2+
but have no effect in the absence of this cation or if the peptide is oxidized. The capacity of loading EF3 with Ca
2+
is essential for this reversal of the FRET signal, whereas the consequences of obliterating Ca
2+
binding to EF1, EF2, or EF4 are negligible. Furthermore, we show that EF3 is critical for translating Ca
2+
signals to reorient the AB fork. Our data are consistent with the proposal that oxidation of cysteine residues in the S2S3 loop relieves K
V
7 channels from a constitutive inhibition imposed by interactions between the EF3 hand of CaM which is crucial for this signaling.