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1.
Regulation of Dietary Amino Acids and Voltage-Gated Calcium Channels in Autism Spectrum Disorder.
Singh, S, Sangam, SR, Senthilkumar, R
Advances in neurobiology. 2020;:647-660
Abstract
Autism, or autism spectrum disorders (ASD), is one of the complex genetic diseases and its etiology is unknown for majority of the patients. It is characterized by deterioration in social interaction, communication, interests, imagination, and activities. As autism is a highly heterogeneous disorder, the symptoms can vary greatly in each affected individual. Oxidative stress implicates major pathogenesis of neurological disorders like ASD. Nutrients and dietary supplements play an important role in the health of an individual and there are several lines of evidence suggesting the role of dietary factors in the development or pathogenesis of ASD. The amino acids supplement has been found to reduce symptoms as they act as the precursors of neurotransmitters which in turn may extenuate mental disorders. The biosynthesis of amino acids in the brain is regulated by the concentration of amino acids in plasma. Amino acids are also considerable entities as they themselves, or peptides consisting of them, have profound antioxidant activities. Dietary constituents have an effect on the transport of amino acids across the blood-brain barrier (BBB) thus indirectly modulating the therapeutic value of amino acids. Among the other factors, voltage-gated calcium channels are directly linked to ASD as per results of genetic studies. Malfunctioning of these calcium channels causes ASD. The intricate biochemical and molecular machinery contributing to neurological disorders is still unknown. Here we discuss the preventive role of dietary amino acids against and regulation of voltage-gated calcium channels on ASD.
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2.
Phenylalkylamines in calcium channels: computational analysis of experimental structures.
Tikhonov, DB, Lin, L, Yang, DSC, Yuchi, Z, Zhorov, BS
Journal of computer-aided molecular design. 2020;(11):1157-1169
Abstract
Experimental 3D structures of calcium channels with phenylalkylamines (PAAs) provide basis for further analysis of atomic mechanisms of these important cardiovascular drugs. In the crystal structure of the engineered calcium channel CavAb with Br-verapamil and in the cryo-EM structure of the Cav1.1 channel with verapamil, the ligands bind in the inner pore. However, there are significant differences between these structures. In the crystal structure the ligand ammonium group is much closer to the ion in the selectivity-filter region Site 3, which is most proximal to the inner pore, than in the cryo-EM structure. Here we used Monte Carlo energy minimizations to dock PAAs in calcium channels. Our computations suggest that in the crystal structure Site 3 is occupied by a water molecule rather than by a calcium ion. Analysis of the published electron density map does not rule out this possibility. In the cryo-EM structures the ammonium group of verapamil is shifted from the calcium ion in Site 3 either along the pore axis, towards the cytoplasm or away from the axis. Our unbiased docking reproduced these binding modes. However, in the cryo-EM structures detergent and lipid molecules interact with verapamil. When we removed these molecules, the nitrile group of verapamil bound to the calcium ion in Site 3. Models of Cav1.2 with different PAAs suggest similar binding modes and direct contacts of the ligands electronegative atoms with the calcium ion in Site 3. Such interactions explain paradoxes in structure-activity relationships of PAAs.
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3.
Charge Inversion and Calcium Gating in Mixtures of Ions in Nanopores.
Lin, K, Lin, CY, Polster, JW, Chen, Y, Siwy, ZS
Journal of the American Chemical Society. 2020;(6):2925-2934
Abstract
Calcium ions play important roles in many physiological processes, yet their concentration is much lower than the concentrations of potassium and sodium ions. The selectivity of calcium channels is often probed in mixtures of calcium and a monovalent salt, e.g., KCl or NaCl, prepared such that the concentration of cations is kept constant with the mole fraction of calcium varying from 0 and 1. In biological channels, even sub-mM concentration of calcium can modulate the channels' transport characteristics; this effect is often explained via the existence of high affinity Ca2+ binding sites on the channel walls. Inspired by properties of biological calcium-selective channels, we prepared a set of nanopores with tunable opening diameters that exhibited a similar response to the presence of calcium ions as biochannels. Nanopores in 15 nm thick silicon nitride films were drilled using focused ion beam and e-beam in a transmission electron microscope and subsequently rendered negatively charged through silanization. We found that nanopores with diameters smaller than 20 nm were blocked by calcium ions such that the ion currents in mixtures of KCl and CaCl2 and in CaCl2 were even ten times smaller than the ion currents in KCl solution. The ion current blockage was explained by the effect of local charge inversion where accumulated calcium ions switch the effective surface charge from negative to positive. The modulation of surface charge with calcium leads to concentration and voltage dependent local charge density and ion current. The combined experimental and modeling results provide a link between calcium ion-induced changes in surface charge properties and resulting ionic transport.
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4.
Impairment of Store-operated Calcium Entry: Implications in Alzheimer's Neurodegeneration.
Zhou, J, Wu, S
Current Alzheimer research. 2020;(12):1088-1094
Abstract
Alzheimer's disease (AD) is an insidious and progressive neurodegenerative disorder. Dysfunction of central cholinergic neurons, amyloid aggregation and deposition,oxidative stress,and biometal dyshomeostasis has been regarded as the major pathogenic mediators in this devastating disease. However, strategies derived from these hypotheses fail to slow down or stop the progression of AD, warranting a combination of therapies to target multiple etiological factors or examining alternative hypothesis. Store-operated calcium entry (SOCE) is the process by which depletion of calcium in the endoplasmic reticulum (ER) lumen causes an influx of calcium across plasmalemma. Accumulating evidence indicates that neuronal SOCE (nSOCE) is inhibited in family AD (FAD) and the inhibition of which causes instability of dendritic spines and enhances amyloidogenesis. Mutant Presenilin fails to function as an ER calcium leak channel and promotes degradation of stromal interaction molecules (STIM), ER calcium sensors; these effects may account for the repression of nSOCE in FAD. We have demonstrated that activation of autophagy degrades STIM proteins, resulting in a trimming effect on a dendritic arbor, under proteasome inhibition and endoplasmic reticulum stress, which are intimately connected with AD. Thus, we hypothesize that autophagy represses SOCE by degrading STIM proteins, leading to synapse loss in AD. This review article will highlight the roles of SOCE in AD neurodegeneration, the degradative mechanisms of STIM protein, and the therapeutic potential and associated challenge.
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5.
Genetic associations between voltage-gated calcium channels and autism spectrum disorder: a systematic review.
Liao, X, Li, Y
Molecular brain. 2020;(1):96
Abstract
OBJECTIVES The present review systematically summarized existing publications regarding the genetic associations between voltage-gated calcium channels (VGCCs) and autism spectrum disorder (ASD). METHODS A comprehensive literature search was conducted to gather pertinent studies in three online databases. Two authors independently screened the included records based on the selection criteria. Discrepancies in each step were settled through discussions. RESULTS From 1163 resulting searched articles, 28 were identified for inclusion. The most prominent among the VGCCs variants found in ASD were those falling within loci encoding the α subunits, CACNA1A, CACNA1B, CACNA1C, CACNA1D, CACNA1E, CACNA1F, CACNA1G, CACNA1H, and CACNA1I as well as those of their accessory subunits CACNB2, CACNA2D3, and CACNA2D4. Two signaling pathways, the IP3-Ca2+ pathway and the MAPK pathway, were identified as scaffolds that united genetic lesions into a consensus etiology of ASD. CONCLUSIONS Evidence generated from this review supports the role of VGCC genetic variants in the pathogenesis of ASD, making it a promising therapeutic target. Future research should focus on the specific mechanism that connects VGCC genetic variants to the complex ASD phenotype.
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6.
Featuring how calcium channels and calmodulin affect glioblastoma behavior. A review article.
Azab, MA, Alomari, A, Azzam, AY
Cancer treatment and research communications. 2020;:100255
Abstract
Glioblastoma (GBM) is considered to be the most aggressive primary brain tumor with an extremely bad prognosis. Recurrence after treatment is a major problem with a survival rate for one year ranging about 39.7%. Ideal outcomes are still difficult to be achieved despite the recent treatment combinations. The ultimate capacity to regrow after resection is considered to be related to the availability of self-regenerating populations of stem cells. We made a literature review interpreting how calcium channels and calcium-regulated proteins mechanistically elaborate glioblastoma virulence in different ways. Calcium channels, and calcium-regulated proteins have shown diverse interconnected roles in shaping different aspects of GBM biology as indicated in some experimental studies. The beneficial prospective of those roles granting GBM different aggressive potentials pose variable applications in targeted therapy whether it is experimental or clinical trials.
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7.
Two distinct phenotypes, hemiplegic migraine and episodic Ataxia type 2, caused by a novel common CACNA1A variant.
Nardello, R, Plicato, G, Mangano, GD, Gennaro, E, Mangano, S, Brighina, F, Raieli, V, Fontana, A
BMC neurology. 2020;(1):155
Abstract
BACKGROUND To investigate the genetic and environmental factors responsible for phenotype variability in a family carrying a novel CACNA1A missense mutation. Mutations in the CACNA1A gene were identified as responsible for at least three autosomal dominant disorders: FHM1 (Familial Hemiplegic Migraine), EA2 (Episodic Ataxia type 2), and SCA6 (Spinocerebellar Ataxia type 6). Overlapping clinical features within individuals of some families sharing the same CACNA1A mutation are not infrequent. Conversely, reports with distinct phenotypes within the same family associated with a common CACNA1A mutation are very rare. CASE PRESENTATION A clinical, molecular, neuroradiological, neuropsychological, and neurophysiological study was carried out in proband and his carrier mother. The new heterozygous missense variant c.4262G > A (p.Arg1421Gln) in the CACNA1A gene was detected in the two affected family members. The proband showed a complex clinical presentation characterized by developmental delay, poor motor coordination, hemiplegic migraine attacks, behavioral dysregulation, and EEG abnormalities. The mother showed typical episodic ataxia attacks during infancy with no other comorbidities and mild cerebellar signs at present neurological evaluation. CONCLUSIONS The proband and his mother exhibit two distinct clinical phenotypes. It can be hypothesized that other unknown modifying genes and/or environmental factors may cooperate to generate the wide intrafamilial variability.
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8.
Neocortical High Probability Release Sites Are Formed by Distinct Ca2+ Channel-to-Release Sensor Topographies during Development.
Bornschein, G, Eilers, J, Schmidt, H
Cell reports. 2019;(6):1410-1418.e4
Abstract
Coupling distances between Ca2+ channels and release sensors regulate vesicular release probability (pv). Tight coupling is thought to provide a framework for high pv and loose coupling for high plasticity at low pv. At synapses investigated during development, coupling distances decrease, thereby increasing pv and transmission fidelity. We find that neocortical high-fidelity synapses deviate from these rules. Paired recordings from pyramidal neurons with "slow" and "fast" Ca2+ chelators combined with experimentally constrained simulations suggest that coupling tightens significantly during development. However, fluctuation analysis revealed that neither pv (∼0.63) nor the number of release sites (∼8) changes concomitantly. Moreover, the amplitude and time course of presynaptic Ca2+ transients are not different between age groups. These results are explained by high-pv release sites with Ca2+ microdomains in young synapses and nanodomains in mature synapses. Thus, at neocortical synapses, a developmental reorganization of the active zone leaves pv unaffected, emphasizing developmental and functional synaptic diversity.
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9.
Mibefradil, a T-type Ca2+ channel blocker also blocks Orai channels by action at the extracellular surface.
Li, P, Rubaiy, HN, Chen, GL, Hallett, T, Zaibi, N, Zeng, B, Saurabh, R, Xu, SZ
British journal of pharmacology. 2019;(19):3845-3856
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Abstract
BACKGROUND AND PURPOSE Mibefradil, a T-type Ca2+ channel blocker, has been investigated for treating solid tumours. However, its underlying mechanisms are still unclear. Here, we have investigated the pharmacological actions of mibefradil on Orai store-operated Ca2+ channels. EXPERIMENTAL APPROACH Human Orai1-3 cDNAs in tetracycline-regulated pcDNA4/TO vectors were transfected into HEK293 T-REx cells with stromal interaction molecule 1 (STIM1) stable expression. The Orai currents were recorded by whole-cell and excised-membrane patch clamp. Ca2+ influx or release was measured by Fura-PE3/AM. Cell growth and death were monitored by WST-1, LDH assays and flow cytometry. KEY RESULTS Mibefradil inhibited Orai1, Orai2, and Orai3 currents dose-dependently. The IC50 for Orai1, Orai2, and Orai3 channels was 52.6, 14.1, and 3.8 μM respectively. Outside-out patch demonstrated that perfusion of 10-μM mibefradil to the extracellular surface completely blocked Orai3 currents and single channel activity evoked by 2-APB. Intracellular application of mibefradil did not alter Orai3 channel activity. Mibefradil at higher concentrations (>50 μM) inhibited Ca2+ release but had no effect on cytosolic STIM1 translocation evoked by thapsigargin. Inhibition on Orai channels by mibefradil was structure-related, as other T-type Ca2+ channel blockers with different structures, such as ethosuximide and ML218, had no or minimal effects on Orai channels. Moreover, mibefradil inhibited cell proliferation, induced apoptosis, and arrested cell cycle progression. CONCLUSIONS AND IMPLICATIONS Mibefradil is a potent cell surface blocker of Orai channels, demonstrating a new pharmacological action of this compound in regulating cell growth and death, which could be relevant to its anti-cancer activity.
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10.
Three-Dimensional and Chemical Mapping of Intracellular Signaling Nanodomains in Health and Disease with Enhanced Expansion Microscopy.
Sheard, TMD, Hurley, ME, Colyer, J, White, E, Norman, R, Pervolaraki, E, Narayanasamy, KK, Hou, Y, Kirton, HM, Yang, Z, et al
ACS nano. 2019;(2):2143-2157
Abstract
Nanodomains are intracellular foci which transduce signals between major cellular compartments. One of the most ubiquitous signal transducers, the ryanodine receptor (RyR) calcium channel, is tightly clustered within these nanodomains. Super-resolution microscopy has previously been used to visualize RyR clusters near the cell surface. A majority of nanodomains located deeper within cells have remained unresolved due to limited imaging depths and axial resolution of these modalities. A series of enhancements made to expansion microscopy allowed individual RyRs to be resolved within planar nanodomains at the cell periphery and the curved nanodomains located deeper within the interiors of cardiomyocytes. With a resolution of ∼ 15 nm, we localized both the position of RyRs and their individual phosphorylation for the residue Ser2808. With a three-dimensional imaging protocol, we observed disturbances to the RyR arrays in the nanometer scale which accompanied right-heart failure caused by pulmonary hypertension. The disease coincided with a distinct gradient of RyR hyperphosphorylation from the edge of the nanodomain toward the center, not seen in healthy cells. This spatial profile appeared to contrast distinctly from that sustained by the cells during acute, physiological hyperphosphorylation when they were stimulated with a β-adrenergic agonist. Simulations of RyR arrays based on the experimentally determined channel positions and phosphorylation signatures showed how the nanoscale dispersal of the RyRs during pathology diminishes its intrinsic likelihood to ignite a calcium signal. It also revealed that the natural topography of RyR phosphorylation could offset potential heterogeneity in nanodomain excitability which may arise from such RyR reorganization.