Dataset Information

Calmodulin promotes a Ca²⁺ -dependent conformational change in the C-terminal regulatory domain of Ca_V 1.2.

ABSTRACT: Calmodulin (CaM) binds to the membrane-proximal cytosolic C-terminal domain of Ca_V 1.2 (residues 1520-1669, CT(1520-1669)) and causes Ca²⁺ -induced conformational changes that promote Ca²⁺ -dependent channel inactivation (CDI). We report biophysical studies that probe the structural interaction between CT(1520-1669) and CaM. The recombinantly expressed CT(1520-1669) is insoluble, but can be solubilized in the presence of Ca²⁺ -saturated CaM (Ca₄ /CaM), but not in the presence of Ca²⁺ -free CaM (apoCaM). We show that half-calcified CaM (Ca₂ /CaM₁₂ ) forms a complex with CT(1520-1669) that is less soluble than CT(1520-1669) bound to Ca₄ /CaM. The NMR spectrum of CT(1520-1669) reveals spectral differences caused by the binding of Ca₂ /CaM₁₂ versus Ca₄ /CaM, suggesting that the binding of Ca²⁺ to the CaM N-lobe may induce a conformational change in CT(1520-1669).

SUBMITTER: Yadav DK

PROVIDER: S-EPMC9719739 | biostudies-literature | 2022 Nov

REPOSITORIES: biostudies-literature

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Calmodulin promotes a Ca2+ -dependent conformational change in the C-terminal regulatory domain of CaV 1.2.

Yadav Deepak Kumar DK Anderson David E DE Hell Johannes W JW Ames James B JB

FEBS letters 20221108 22

Calmodulin (CaM) binds to the membrane-proximal cytosolic C-terminal domain of CaV 1.2 (residues 1520-1669, CT(1520-1669)) and causes Ca2+ -induced conformational changes that promote Ca2+ -dependent channel inactivation (CDI). We report biophysical studies that probe the structural interaction between CT(1520-1669) and CaM. The recombinantly expressed CT(1520-1669) is insoluble, but can be solubilized in the presence of Ca2+ -saturated CaM (Ca4</ ...[more]

PMID: 36310389

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Project description:Mammalian circadian (24 h) rhythms are timed by the pattern of spontaneous action potential firing in the suprachiasmatic nucleus (SCN). This oscillation in firing is produced through circadian regulation of several membrane currents, including large-conductance Ca2+- and voltage-activated K+ (BK) and L-type Ca2+ channel (LTCC) currents. During the day steady-state BK currents depend mostly on LTCCs for activation, whereas at night they depend predominantly on ryanodine receptors (RyRs). However, the contribution of these Ca2+ channels to BK channel activation during action potential firing has not been thoroughly investigated. In this study, we used a pharmacological approach to determine that both LTCCs and RyRs contribute to the baseline membrane potential of SCN action potential waveforms, as well as action potential-evoked BK current, during the day and night, respectively. Since the baseline membrane potential is a major determinant of circadian firing rate, we focused on the LTCCs contributing to low voltage activation of BK channels during the subthreshold phase. For these experiments, two LTCC subtypes found in SCN (CaV1.2 and CaV1.3) were coexpressed with BK channels in heterologous cells, where their differential contributions could be separately measured. CaV1.3 channels produced currents that were shifted to more hyperpolarized potentials compared with CaV1.2, resulting in increased subthreshold Ca2+ and BK currents during an action potential command. These results show that although multiple Ca2+ sources in SCN can contribute to the activation of BK current during an action potential, specific BK-CaV1.3 partnerships may optimize the subthreshold BK current activation that is critical for firing rate regulation.NEW & NOTEWORTHY BK K+ channels are important regulators of firing. Although Ca2+ channels are required for their activation in excitable cells, it is not well understood how BK channels activate using these Ca2+ sources during an action potential. This study demonstrates the differences in BK current activated by CaV1.2 and CaV1.3 channels in clock neurons and heterologous cells. The results define how specific ion channel partnerships can be engaged during distinct phases of the action potential.

Dataset Information

Calmodulin promotes a Ca²⁺ -dependent conformational change in the C-terminal regulatory domain of Ca_V 1.2.

Publications

Calmodulin promotes a Ca<sup>2+</sup> -dependent conformational change in the C-terminal regulatory domain of Ca<sub>V</sub> 1.2.

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