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Calmodulin regulates Cav3 T-type channels at their gating brake

Chemin, J; Taiakina, V; Monteil, A; Piazza, M; Guan, W; Stephens, RF; Kitmitto, A; ... Spafford, JD; + view all (2017) Calmodulin regulates Cav3 T-type channels at their gating brake. Journal of Biological Chemistry , 292 (49) pp. 20010-20031. 10.1074/jbc.M117.807925. Green open access

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Abstract

Calcium (Cav1 and Cav2) and sodium channels possess homologous CaM-binding motifs, known as IQ motifs in their C-termini, which associate with calmodulin (CaM), a universal calcium sensor. Cav3 T-type channels, which serve as pacemakers of the mammalian brain and heart, lack a C-terminal IQ motif. We illustrate that T-type channels associate with CaM using co-immunoprecipitation experiments and single particle cryo-electron microscopy. We demonstrate that protostome invertebrate (LCav3) and human Cav3.1, Cav3.2, and Cav3.3 T-type channels specifically associate with CaM at helix 2 of the gating brake in the I-II linker of the channels. Isothermal titration calorimetry results revealed that the gating brake and CaM bind each other with high nanomolar affinity. We show that the gating brake assumes a helical conformation upon binding CaM, with associated conformational changes to both CaM lobes as indicated by amide chemical shifts of the amino acids of CaM in 1H-15N HSQC NMR spectra. Intact Ca2+-binding sites on CaM and an intact gating brake sequence (first 39 aa of the I-II linker) were required in Cav3.2 channels to prevent the runaway gating phenotype, a hyperpolarizing shift in voltage sensitivities and faster gating kinetics. We conclude that the presence of high-nanomolar affinity binding sites for CaM at its universal gating brake and its unique form of regulation via the tuning of the voltage range of activity could influence the participation of Cav3 T-type channels in heart and brain rhythms. Our findings may have implications for arrhythmia disorders arising from mutations in the gating brake or CaM.

Type: Article
Title: Calmodulin regulates Cav3 T-type channels at their gating brake
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1074/jbc.M117.807925
Publisher version: http://dx.doi.org/10.1074/jbc.M117.807925
Language: English
Additional information: © 2017 by The American Society for Biochemistry and Molecular Biology, Inc. Author's Choice—Final version free via Creative Commons CC-BY license.
Keywords: Calcium channel; patch clamp; isothermal titration calorimetry (ITC); circular dichroism (CD); nuclear magnetic resonance (NMR); cryo-electron microscopy; short hairpin RNA (shRNA); gating
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Neuro, Physiology and Pharmacology
URI: http://discovery.ucl.ac.uk/id/eprint/10025126
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