Voltage- and calcium-dependent inactivation in high voltage-gated Ca2+ channels

Voltage-gated calcium channels (CaVs) are large (∼0.5 MDa), multisubunit, macromolecular machines that control calcium entry into cells in response to membrane potential changes. These molecular switches play pivotal roles in cardiac action potentials, neurotransmitter release, muscle contraction, calcium-dependent gene transcription and synaptic transmission. CaVs possess self-regulatory mechanisms that permit them to change their behaviour in response to activity, including voltage-dependent inactivation, calcium-dependent inactivation and calcium-dependent facilitation. These processes arise from the concerted action of different channel domains with CaV β-subunits and the soluble calcium sensor calmodulin. Until recently, nothing was known about the CaV structure at high resolution. Recent crystallographic work has revealed the first glimpses at the CaV molecular framework and set a new direction towards a detailed mechanistic understanding of CaV function.

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Voltage- and Calcium-Dependent Inactivation of Calcium Channels in Lymnaea Neurons

The Journal of General Physiology ◽

10.1085/jgp.114.4.535 ◽

1999 ◽

Vol 114 (4) ◽

pp. 535-550 ◽

Cited By ~ 6

Author(s):

Shalini Gera ◽

Lou Byerly

Keyword(s):

Cytochalasin B ◽

Lymnaea Stagnalis ◽

Slow Component ◽

Freshwater Snail ◽

High Concentration ◽

Calcium Dependent ◽

Channel Inactivation ◽

Dependent Inactivation ◽

Lymnaea Neurons ◽

Ca2 Channels

Ca2+ channel inactivation in the neurons of the freshwater snail, Lymnaea stagnalis, was studied using patch-clamp techniques. In the presence of a high concentration of intracellular Ca2+ buffer (5 mM EGTA), the inactivation of these Ca2+ channels is entirely voltage dependent; it is not influenced by the identity of the permeant divalent ions or the amount of extracellular Ca2+ influx, or reduced by higher levels of intracellular Ca2+ buffering. Inactivation measured under these conditions, despite being independent of Ca2+ influx, has a bell-shaped voltage dependence, which has often been considered a hallmark of Ca2+-dependent inactivation. Ca2+-dependent inactivation does occur in Lymnaea neurons, when the concentration of the intracellular Ca2+ buffer is lowered to 0.1 mM EGTA. However, the magnitude of Ca2+-dependent inactivation does not increase linearly with Ca2+ influx, but saturates for relatively small amounts of Ca2+ influx. Recovery from inactivation at negative potentials is biexponential and has the same time constants in the presence of different intracellular concentrations of EGTA. However, the amplitude of the slow component is selectively enhanced by a decrease in intracellular EGTA, thus slowing the overall rate of recovery. The ability of 5 mM EGTA to completely suppress Ca2+-dependent inactivation suggests that the Ca2+ binding site is at some distance from the channel protein itself. No evidence was found of a role for serine/threonine phosphorylation in Ca2+ channel inactivation. Cytochalasin B, a microfilament disrupter, was found to greatly enhance the amount of Ca2+ channel inactivation, but the involvement of actin filaments in this effect of cytochalasin B on Ca2+ channel inactivation could not be verified using other pharmacological compounds. Thus, the mechanism of Ca2+-dependent inactivation in these neurons remains unknown, but appears to differ from those proposed for mammalian L-type Ca2+ channels.

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Single-Channel Mechanism of Modulation of Calcium-Dependent Inactivation of the Voltage-Gated Calcium Channel Cav1.3 by its C-Terminus

Biophysical Journal ◽

10.1016/j.bpj.2012.11.2540 ◽

2013 ◽

Vol 104 (2) ◽

pp. 459a

Author(s):

Elena Novikova ◽

Elza Kuzmenkina ◽

Wanchana Jangsangthong ◽

Jan Matthes ◽

Alexandra Koschak ◽

...

Keyword(s):

Calcium Channel ◽

Single Channel ◽

Voltage Gated ◽

Calcium Dependent ◽

C Terminus ◽

Dependent Inactivation ◽

Voltage Gated Calcium Channel

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Voltage-gated calcium channels in GtoPdb v.2021.2

IUPHAR/BPS Guide to Pharmacology CITE ◽

10.2218/gtopdb/f80/2021.2 ◽

2021 ◽

Vol 2021 (2) ◽

Author(s):

William A. Catterall ◽

Edward Perez-Reyes ◽

Terrance P. Snutch ◽

Jörg Striessnig

Keyword(s):

High Voltage ◽

Low Voltage ◽

Transmembrane Domains ◽

Voltage Gated ◽

Voltage Dependent ◽

Alternatively Spliced ◽

Membrane Spanning ◽

Voltage Gated Ion Channels ◽

Ca2 Channels ◽

Α1 Subunit

Calcium (Ca2+) channels are voltage-gated ion channels present in the membrane of most excitable cells. The nomenclature for Ca2+channels was proposed by [127] and approved by the NC-IUPHAR Subcommittee on Ca2+ channels [70]. Most Ca2+ channels form hetero-oligomeric complexes. The α1 subunit is pore-forming and provides the binding site(s) for practically all agonists and antagonists. The 10 cloned α1-subunits can be grouped into three families: (1) the high-voltage activated dihydropyridine-sensitive (L-type, CaV1.x) channels; (2) the high- to moderate-voltage activated dihydropyridine-insensitive (CaV2.x) channels and (3) the low-voltage-activated (T-type, CaV3.x) channels. Each α1 subunit has four homologous repeats (I-IV), each repeat having six transmembrane domains and a pore-forming region between transmembrane domains S5 and S6. Voltage-dependent gating is driven by the membrane spanning S4 segment, which contains highly conserved positive charges that respond to changes in membrane potential. All of the α1-subunit genes give rise to alternatively spliced products. At least for high-voltage activated channels, it is likely that native channels comprise co-assemblies of α1, β and α2-δ subunits. The γ subunits have not been proven to associate with channels other than the α1s skeletal muscle Cav1.1 channel. The α2-δ1 and α2-δ2 subunits bind gabapentin and pregabalin.

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Disruption of the IS6-AID Linker Affects Voltage-gated Calcium Channel Inactivation and Facilitation

The Journal of General Physiology ◽

10.1085/jgp.200810143 ◽

2009 ◽

Vol 133 (3) ◽

pp. 327-343 ◽

Cited By ~ 43

Author(s):

Felix Findeisen ◽

Daniel L. Minor

Keyword(s):

Calcium Channel ◽

Common Mechanism ◽

Interaction Domain ◽

Voltage Gated ◽

Calcium Dependent ◽

Calcium Channel Inactivation ◽

Dependent Inactivation ◽

Voltage Dependent ◽

Rigid Connection ◽

Voltage Gated Calcium Channel

Two processes dominate voltage-gated calcium channel (CaV) inactivation: voltage-dependent inactivation (VDI) and calcium-dependent inactivation (CDI). The CaVβ/CaVα1-I-II loop and Ca2+/calmodulin (CaM)/CaVα1–C-terminal tail complexes have been shown to modulate each, respectively. Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved. Here, we demonstrate that the IS6–α-interaction domain (AID) linker provides a rigid connection between the pore and CaVβ/I-II loop complex by showing that IS6-AID linker polyglycine mutations accelerate CaV1.2 (L-type) and CaV2.1 (P/Q-type) VDI. Remarkably, mutations that either break the rigid IS6-AID linker connection or disrupt CaVβ/I-II association sharply decelerate CDI and reduce a second Ca2+/CaM/CaVα1–C-terminal–mediated process known as calcium-dependent facilitation. Collectively, the data strongly suggest that components traditionally associated solely with VDI, CaVβ and the IS6-AID linker, are essential for calcium-dependent modulation, and that both CaVβ-dependent and CaM-dependent components couple to the pore by a common mechanism requiring CaVβ and an intact IS6-AID linker.

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Molecular moieties masking Ca2+-dependent facilitation of voltage-gated Cav2.2 Ca2+ channels

The Journal of General Physiology ◽

10.1085/jgp.201711841 ◽

2017 ◽

Vol 150 (1) ◽

pp. 83-94 ◽

Cited By ~ 2

Author(s):

Jessica R. Thomas ◽

Jussara Hagen ◽

Daniel Soh ◽

Amy Lee

Keyword(s):

Functional Divergence ◽

Short Term ◽

Voltage Gated ◽

Regulatory Domains ◽

Dependent Inactivation ◽

Weak Binding ◽

Ef Hand ◽

Molecular Determinants ◽

Ca2 Channels ◽

Α1 Subunit

Voltage-gated Cav2.1 (P/Q-type) Ca2+ channels undergo Ca2+-dependent inactivation (CDI) and facilitation (CDF), both of which contribute to short-term synaptic plasticity. Both CDI and CDF are mediated by calmodulin (CaM) binding to sites in the C-terminal domain of the Cav2.1 α1 subunit, most notably to a consensus CaM-binding IQ-like (IQ) domain. Closely related Cav2.2 (N-type) channels display CDI but not CDF, despite overall conservation of the IQ and additional sites (pre-IQ, EF-hand–like [EF] domain, and CaM-binding domain) that regulate CDF of Cav2.1. Here we investigate the molecular determinants that prevent Cav2.2 channels from undergoing CDF. Although alternative splicing of C-terminal exons regulates CDF of Cav2.1, the splicing of analogous exons in Cav2.2 does not reveal CDF. Transfer of sequences encoding the Cav2.1 EF, pre-IQ, and IQ together (EF-pre-IQ-IQ), but not individually, are sufficient to support CDF in chimeric Cav2.2 channels; Cav2.1 chimeras containing the corresponding domains of Cav2.2, either alone or together, fail to undergo CDF. In contrast to the weak binding of CaM to just the pre-IQ and IQ of Cav2.2, CaM binds to the EF-pre-IQ-IQ of Cav2.2 as well as to the corresponding domains of Cav2.1. Therefore, the lack of CDF in Cav2.2 likely arises from an inability of its EF-pre-IQ-IQ to transduce the effects of CaM rather than weak binding to CaM per se. Our results reveal a functional divergence in the CDF regulatory domains of Cav2 channels, which may help to diversify the modes by which Cav2.1 and Cav2.2 can modify synaptic transmission.

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Voltage-gated calcium channels (CaV) in GtoPdb v.2021.3

IUPHAR/BPS Guide to Pharmacology CITE ◽

10.2218/gtopdb/f80/2021.3 ◽

2021 ◽

Vol 2021 (3) ◽

Author(s):

William A. Catterall ◽

Edward Perez-Reyes ◽

Terrance P. Snutch ◽

Jörg Striessnig

Keyword(s):

High Voltage ◽

Low Voltage ◽

Excitable Cells ◽

Voltage Gated ◽

Voltage Dependent ◽

Alternatively Spliced ◽

Membrane Spanning ◽

Voltage Gated Ion Channels ◽

Ca2 Channels ◽

Α1 Subunit

Ca2+ channels are voltage-gated ion channels present in the membrane of most excitable cells. The nomenclature for Ca2+channels was proposed by [127] and approved by the NC-IUPHAR Subcommittee on Ca2+ channels [70]. Most Ca2+ channels form hetero-oligomeric complexes. The α1 subunit is pore-forming and provides the binding site(s) for practically all agonists and antagonists. The 10 cloned α1-subunits can be grouped into three families: (1) the high-voltage activated dihydropyridine-sensitive (L-type, CaV1.x) channels; (2) the high- to moderate-voltage activated dihydropyridine-insensitive (CaV2.x) channels and (3) the low-voltage-activated (T-type, CaV3.x) channels. Each α1 subunit has four homologous repeats (I-IV), each repeat having six transmembrane domains (S1-S6) and a pore-forming region between S5 and S6. Voltage-dependent gating is driven by the membrane spanning S4 segment, which contains highly conserved positive charges that respond to changes in membrane potential. All of the α1-subunit genes give rise to alternatively spliced products. At least for high-voltage activated channels, it is likely that native channels comprise co-assemblies of α1, β and α2-δ subunits. The γ subunits have not been proven to associate with channels other than the α1s skeletal muscle Cav1.1 channel. The α2-δ1 and α2-δ2 subunits bind gabapentin and pregabalin.

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Activity-dependent regulation of T-type calcium channels by submembrane calcium ions

eLife ◽

10.7554/elife.22331 ◽

2017 ◽

Vol 6 ◽

Cited By ~ 10

Author(s):

Magali Cazade ◽

Isabelle Bidaud ◽

Philippe Lory ◽

Jean Chemin

Keyword(s):

Calcium Ions ◽

Large Decrease ◽

Channel Activity ◽

Ionotropic Receptors ◽

Voltage Gated ◽

Dependent Inactivation ◽

Steady State Inactivation ◽

Activity Dependent ◽

Hyperpolarizing Shift ◽

Ca2 Channels

Voltage-gated Ca2+ channels are involved in numerous physiological functions and various mechanisms finely tune their activity, including the Ca2+ ion itself. This is well exemplified by the Ca2+-dependent inactivation of L-type Ca2+ channels, whose alteration contributes to the dramatic disease Timothy Syndrome. For T-type Ca2+ channels, a long-held view is that they are not regulated by intracellular Ca2+. Here we challenge this notion by using dedicated electrophysiological protocols on both native and expressed T-type Ca2+ channels. We demonstrate that a rise in submembrane Ca2+ induces a large decrease in T-type current amplitude due to a hyperpolarizing shift in the steady-state inactivation. Activation of most representative Ca2+-permeable ionotropic receptors similarly regulate T-type current properties. Altogether, our data clearly establish that Ca2+ entry exerts a feedback control on T-type channel activity, by modulating the channel availability, a mechanism that critically links cellular properties of T-type Ca2+ channels to their physiological roles.

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