scholarly journals Voltage-gated calcium channels: Their discovery, function and importance as drug targets

2018 ◽  
Vol 2 ◽  
pp. 239821281879480 ◽  
Author(s):  
Annette C. Dolphin
Keyword(s):  
Calcium Channels ◽  
Calcium Channel ◽  
Drug Targets ◽  
Single Channel ◽  
Calcium Currents ◽  
Kinetic Properties ◽  
Subcellular Localisation ◽  
Channel Blockers ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels

This review will first describe the importance of Ca2+ entry for function of excitable cells, and the subsequent discovery of voltage-activated calcium conductances in these cells. This finding was rapidly followed by the identification of multiple subtypes of calcium conductance in different tissues. These were initially termed low- and high-voltage activated currents, but were then further subdivided into L-, N-, PQ-, R- and T-type calcium currents on the basis of differing pharmacology, voltage-dependent and kinetic properties, and single channel conductance. Purification of skeletal muscle calcium channels allowed the molecular identification of the pore-forming and auxiliary α2δ, β and ϒ subunits present in these calcium channel complexes. These advances then led to the cloning of the different subunits, which permitted molecular characterisation, to match the cloned channels with physiological function. Studies with knockout and other mutant mice then allowed further investigation of physiological and pathophysiological roles of calcium channels. In terms of pharmacology, cardiovascular L-type channels are targets for the widely used antihypertensive 1,4-dihydropyridines and other calcium channel blockers, N-type channels are a drug target in pain, and α2δ-1 is the therapeutic target of the gabapentinoid drugs, used in neuropathic pain. Recent structural advances have allowed a deeper understanding of Ca2+ permeation through the channel pore and the structure of both the pore-forming and auxiliary subunits. Voltage-gated calcium channels are subject to multiple pathways of modulation by G-protein and second messenger regulation. Furthermore, their trafficking pathways, subcellular localisation and functional specificity are the subjects of active investigation.

scholarly journals Voltage-gated calcium channel blockers for psychiatric disorders: genomic reappraisal

2019 ◽  
Vol 216 (5) ◽  
pp. 250-253 ◽  
Author(s):  
Paul J. Harrison ◽  
Elizabeth M. Tunbridge ◽  
Annette C. Dolphin ◽  
Jeremy Hall
Keyword(s):  
Calcium Channels ◽  
Calcium Channel ◽  
Psychiatric Disorders ◽  
Calcium Channel Blockers ◽  
Channel Blockers ◽  
Risk Genes ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Voltage Gated Calcium Channel ◽  
Second Use

SummaryWe reappraise the psychiatric potential of calcium channel blockers (CCBs). First, voltage-gated calcium channels are risk genes for several disorders. Second, use of CCBs is associated with altered psychiatric risks and outcomes. Third, research shows there is an opportunity for brain-selective CCBs, which are better suited to psychiatric indications.

Properties and distribution of single voltage-gated calcium channels in adult hippocampal neurons

1990 ◽  
Vol 64 (1) ◽  
pp. 91-104 ◽  
Author(s):  
R. E. Fisher ◽  
R. Gray ◽  
D. Johnston
Keyword(s):  
Guinea Pig ◽  
Calcium Channels ◽  
Single Channel ◽  
Cell Types ◽  
Voltage Gated ◽  
Channel Current ◽  
Single Channel Current ◽  
Voltage Gated Calcium Channels ◽  
Large Conductance Channel ◽  
Small Conductance

1. The properties of single voltage-gated calcium channels were investigated in acutely exposed CA3 and CA1 pyramidal neurons and granule cells of area dentata in the adult guinea pig hippocampal formation. 2. Guinea pig hippocampal slices were prepared in a conventional manner, then treated with proteolytic enzymes and gently shaken to expose the somata of the three cell types studied. Standard patch-clamp techniques were used to record current flow through calcium channels in cell-attached membrane patches with isotonic barium as the charge carrier. 3. Single-channel current amplitudes were measured at different membrane potentials. Single-channel current-voltage plots were constructed and single-channel slope conductances were found to fall into three classes. These were (approximately) 8, 14, and 25 pS, and were observed in all three cell types. 4. The three groups of channels differed from each other in voltage dependence of activation: from a holding potential of -80, the small-conductance channel began to activate at about -40 to -30 mV, the medium-conductance channel at about -20 mV, and the large-conductance channel at approximately 0 mV. 5. Ensemble averages of single-channel currents during voltage steps revealed differences in voltage-dependent inactivation. The small-conductance channel inactivated completely within approximately 50 ms during steps from -80 to -10 mV or more positive. Steps to less positive potentials resulted in less inactivation. The medium-conductance channel displayed variable inactivation during steps from -80 to 0 mV. Inactivation of this channel during a 160-ms step ranged from virtually zero to approximately 100%. The large-conductance channel displayed no significant inactivation during steps as long as 400 ms. 6. The large-conductance channel was strikingly affected by the dihydropyridine agonist Bay K8644 (0.5-2.0 microM), resulting in a high probability of channel opening, prolonged openings, and an apparent increase in the number of channels available for activation. The medium and small-conductance channels were not noticeably affected by the drug. 7. The large-conductance channel could be induced to open at very negative membrane potentials by holding the patch for several seconds at 20 or 30 mV and stepping to -30 or -40 mV. This process was enhanced by Bay K8644, resulting in prolonged openings at potentials as negative as -100 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium- and Calmodulin-Dependent Inactivation of Calcium Channels in Inner Hair Cells of the Rat Cochlea

2008 ◽  
Vol 99 (5) ◽  
pp. 2183-2193 ◽  
Author(s):  
Lisa Grant ◽  
Paul Fuchs
Keyword(s):  
Calcium Channels ◽  
Hair Cells ◽  
Calcium Currents ◽  
Resting Potential ◽  
Resting Membrane Potential ◽  
Inner Hair Cells ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Dependent Inactivation ◽  
Calcium Buffering

Modulation of voltage-gated calcium channels was studied in inner hair cells (IHCs) in an ex vivo preparation of the apical turn of the rat organ of Corti. Whole cell voltage clamp in the presence of potassium channel blockers showed inward calcium currents with millisecond activation and deactivation kinetics. When temperature was raised from 22 to 37°C, the calcium currents of immature IHCs [<12 days postnatal (P12)] increased threefold in amplitude, and developed more pronounced inactivation. This was determined to be calcium-dependent inactivation (CDI) on the basis of its reliance on external calcium (substitution with barium), sensitivity to internal calcium-buffering, and voltage dependence (reflecting the calcium driving force). After the onset of hearing at P12, IHC calcium current amplitude and the extent of inactivation were greatly reduced. Although smaller than in prehearing IHCs, CDI remained significant in the mature IHC near the resting membrane potential. CDI in mature IHCs was enhanced by application of the endoplasmic calcium pump blocker, benzo-hydroquinone. Conversely, CDI in immature IHCs was reduced by calmodulin inhibitors. Thus voltage-gated calcium channels in mammalian IHCs are subject to a calmodulin-mediated process of CDI. The extent of CDI depends on the balance of calcium buffering mechanisms and may be regulated by calmodulin-specific processes. CDI provides a means for the rate of spontaneous transmitter release to be adjusted to variations in hair cell resting potential and steady state calcium influx.

Modeling ion permeation through a bacterial voltage-gated calcium channel CaVAb using molecular dynamics simulations

2017 ◽  
Vol 13 (1) ◽  
pp. 208-214 ◽  
Author(s):  
Jamal Adiban ◽  
Yousef Jamali ◽  
Hashem Rafii-Tabar
Keyword(s):  
Molecular Dynamics ◽  
Calcium Channels ◽  
Calcium Channel ◽  
Molecular Dynamics Simulations ◽  
Selectivity Filter ◽  
Ion Permeation ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Voltage Gated Calcium Channel ◽  
Dynamics Simulations

Ca2+ion binds tightly to the center of the selectivity filter of voltage-gated calcium channels.

scholarly journals Functions of Presynaptic Voltage-gated Calcium Channels

Function ◽  
2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Annette C Dolphin
Keyword(s):  
Calcium Channels ◽  
Neurotransmitter Release ◽  
Action Potentials ◽  
Voltage Dependence ◽  
Kinetic Properties ◽  
Excitable Cells ◽  
Single Action ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Vesicular Release

Abstract Voltage-gated calcium channels are the principal conduits for depolarization-mediated Ca2+ entry into excitable cells. In this review, the biophysical properties of the relevant members of this family of channels, those that are present in presynaptic terminals, will be discussed in relation to their function in mediating neurotransmitter release. Voltage-gated calcium channels have properties that ensure they are specialized for particular roles, for example, differences in their activation voltage threshold, their various kinetic properties, and their voltage-dependence of inactivation. All these attributes play into the ability of the various voltage-gated calcium channels to participate in different patterns of presynaptic vesicular release. These include synaptic transmission resulting from single action potentials, and longer-term changes mediated by bursts or trains of action potentials, as well as release resulting from graded changes in membrane potential in specialized sensory synapses.

scholarly journals A new homozygous CACNB2 mutation has functional relevance and supports a role for calcium channels in autism spectrum disorder

2019 ◽  
Author(s):  
Claudio Graziano ◽  
Patrick Despang ◽  
Flavia Palombo ◽  
Giulia Severi ◽  
Annio Posar ◽  
...  
Keyword(s):  
Autism Spectrum Disorder ◽  
Calcium Channels ◽  
Calcium Channel ◽  
Autism Spectrum ◽  
Spectrum Disorder ◽  
Site Directed Mutagenesis ◽  
Global Developmental Delay ◽  
Whole Cell ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels

Abstract BackgroundDiagnostic yield in patients with autism spectrum disorder (ASD) has improved over the last years, thanks to the introduction of whole genome arrays and next generation sequencing, but etiology is still unknown for the majority of cases. Among distinct cellular pathways, evidence implicating dysregulation of cellular calcium homeostasis in ASD pathogenesis has been accumulating, and specific mutations in voltage-gated calcium channels found in patients with autism were shown to be functionally relevant.MethodsWhole exome sequencing and Sanger sequencing were performed to identify and confirm variants in a girl with ASD, global developmental delay and precocious puberty, born of first-degree cousins. Site-directed mutagenesis was used to generate a human CaVβ2d calcium channel subunit carrying a CACNB2 mutation. Whole-cell patch-clamp recordings were performed to reveal functional effects of mutant CaVβ2d on Ba2+-currents mediated by L-type (CaV1.2) calcium channels in transiently transfected HEK-293 cells.ResultsIn an ASD patient, we identified a rare homozygous variant (p.Arg70Cys) in the CACNB2 gene coding for the auxiliary CaVβ2subunit of voltage-gated calcium channels. In a recombinant system, the CaVβ2 variant, which was not previously associated to ASD, was found to alter CaV1.2 calcium channel function by significantly affecting activation and inactivation of whole-cell Ba2+-currents.LimitationsAlthough the evidence of CACNB2 involvement in ASD is slowly accumulating, the number of reported patients is very limited. Deep clinical phenotyping and functional studies in larger sets of subjects will be instrumental to fully understand the penetrance and outcome of CACNB2 variants.ConclusionsThe p.Arg70Cys variant in CACNB2 shows functional consequences similar to other ASD-associated CaVβ2 mutations. These results support the idea of CACNB2 variations contributing to the development of ASD and hint to a rare form of Mendelian recessive autism with possible specific comorbidities.

Dependency of hypoxic chemotransduction in cat carotid body on voltage-gated calcium channels

1991 ◽  
Vol 71 (3) ◽  
pp. 1062-1069 ◽  
Author(s):  
M. Shirahata ◽  
R. S. Fitzgerald
Keyword(s):  
Calcium Channels ◽  
Calcium Channel ◽  
Intracellular Calcium ◽  
Carotid Body ◽  
Calcium Ions ◽  
Extracellular Calcium ◽  
Bay K 8644 ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Selective Perfusion

The hypothesis that the entry of extracellular calcium ions into some compartment, quite possibly the type I cells, through voltage-gated calcium channels (VGCC) is essential for hypoxic chemotransduction in the cat carotid body was tested using an in situ perfusion technique. The neural output of the carotid body of anesthetized, paralyzed, and artificially ventilated cats in response to perfusions with Krebs-Ringer bicarbonate solution (KRB), calcium-free KRB, KRB containing calcium channel blockers, or KRB containing BAY K 8644 was recorded. Selective perfusion of the carotid body with hypoxic calcium-free KRB significantly decreased carotid chemoreceptor activity, suggesting that extracellular calcium is essential for hypoxic chemotransduction. Selective perfusion of the carotid body with hypoxic KRB containing verapamil (10–100 microM), diltiazem (10–100 microM), or nifedipine (10–100 microM) dose dependently attenuated the increase in chemoreceptor activity produced by hypoxia, suggesting that VGCC need to be activated for hypoxic chemotransduction. The carotid body response to hyperoxic KRB containing the calcium channel agonist BAY K 8644 (10 microM) was 267 +/- 87% of hyperoxic control KRB, suggesting that an enhanced influx of calcium ions through VGCC stimulates carotid chemoreceptor activity. Selective perfusion of the carotid body with severely hypoxic KRB containing BAY K 8644 did not increase chemoreceptor activity above that produced by severe hypoxia alone. This suggests that severe hypoxia increases intracellular calcium in some compartment of the carotid body to achieve stimulatory maximum response and that further increase in intracellular calcium does not produce further elevation of neural activity.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Different α2δ Accessory Subunits Regulate Distinctly Different Aspects of Calcium Channel Function in the Same Drosophila Neurons

2019 ◽  
Author(s):  
Laurin Heinrich ◽  
Stefanie Ryglewski
Keyword(s):  
Calcium Channels ◽  
Calcium Channel ◽  
Intracellular Signaling ◽  
Brain Diseases ◽  
Voltage Gated ◽  
Channel Function ◽  
Voltage Gated Calcium Channels ◽  
Accessory Subunits ◽  
Neuronal Compartments

AbstractVoltage gated calcium channels (VGCCs) regulate neuronal excitability and translate activity into calcium dependent intracellular signaling. The pore forming α1 subunit of high voltage activated (HVA) VGCCs operates not in isolation but associates with α2δ accessory subunits. α2δ subunits can affect calcium channel biophysical properties, surfacing, localization and transport, but their in vivo functions are incompletely understood. In vertebrates, it is largely unknown whether different combinations of the four α2δ and the 7 α1 subunits mediate different or partially redundant functions or whether different α1/α2δ combinations regulate different aspects of VGCC function. This study capitalizes on the relatively simpler situation in the Drosophila genetic model that contains only two genes for HVA calcium channels, one Cav1 homolog and one Cav2 homolog, both with well-described functions in different compartments of identified motoneurons. We find that both dα2δ1 and dα2δ3 (stj) are broadly but differently expressed in the nervous system. Both are expressed in motoneurons, but with differential subcellular localization. Functional analysis reveals that dα2δ3 is required for normal Cav1 and Cav2 current amplitudes and for correct Cav2 channel function in all neuronal compartments, axon terminal, axon, and somatodendritic domain. By contrast, dα2δ1 does not affect Cav1 or Cav2 current amplitudes or presynaptic function, but it is required for correct Cav2 channel allocation to the axonal versus the dendritic domain. Therefore, different α2δ subunits are required in the same neurons to precisely regulate distinctly different functions of HVA calcium channels, which is in accord with specific α2δ mutations causing different brain diseases.Significance StatementCalcium influx through the pore forming α1-subunit of voltage gated calcium channels serves essential neuronal functions, such as synaptic vesicle release, control of action potential shape and frequencies, synaptic input computations, and transcriptional control. Localization and function of α1-calcium channel subunits depend on interactions with α2δ accessory subunits. Here we present in vivo analysis of Drosophila motoneurons revealing that different α2δ subunits independently regulate distinctly different aspects of calcium channel function in the same neuron, such as current amplitude and dendritic versus axonal channel localization. Our findings start unraveling how different α1/α2δ combinations regulate functional calcium channel diversity in different sub-neuronal compartments, and may provide an entry point toward understanding how mutations of different α2δ genes underlie brain diseases.

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