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Mazzaferro S, Kang G, Natarajan K, Hibbs RE, Sine SM. Structural bases for stoichiometry-selective calcium potentiation of a neuronal nicotinic receptor. Br J Pharmacol 2024. [PMID: 38454578 DOI: 10.1111/bph.16321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 01/05/2024] [Accepted: 01/08/2024] [Indexed: 03/09/2024] Open
Abstract
BACKGROUND AND PURPOSE α4β2 nicotinic acetylcholine (nACh) receptors assemble in two stoichiometric forms, one of which is potentiated by calcium. The sites of calcium binding that underpin potentiation are not known. EXPERIMENTAL APPROACH To identify calcium binding sites, we applied cryo-electron microscopy (cryo-EM) and molecular dynamics (MD) simulations to each stoichiometric form of the α4β2 nACh receptor in the presence of calcium ions. To test whether the identified calcium sites are linked to potentiation, we generated mutants of anionic residues at the sites, expressed wild type and mutant receptors in clonal mammalian fibroblasts, and recorded ACh-elicited single-channel currents with or without calcium. KEY RESULTS Both cryo-EM and MD simulations show calcium bound to a site between the extracellular and transmembrane domains of each α4 subunit (ECD-TMD site). Substituting alanine for anionic residues at the ECD-TMD site abolishes stoichiometry-selective calcium potentiation, as monitored by single-channel patch clamp electrophysiology. Additionally, MD simulation reveals calcium association at subunit interfaces within the extracellular domain. Substituting alanine for anionic residues at the ECD sites reduces or abolishes stoichiometry-selective calcium potentiation. CONCLUSIONS AND IMPLICATIONS Stoichiometry-selective calcium potentiation of the α4β2 nACh receptor is achieved by calcium association with topographically distinct sites framed by anionic residues within the α4 subunit and between the α4 and β2 subunits. Stoichiometry-selective calcium potentiation could result from the greater number of calcium sites in the stoichiometric form with three rather than two α4 subunits. The results are relevant to modulation of signalling via α4β2 nACh receptors in physiological and pathophysiological conditions.
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Affiliation(s)
- Simone Mazzaferro
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
- Wellcome Trust - Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, UK
- Wellcome Trust - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, UK
| | - Guipeun Kang
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Kathiresan Natarajan
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Ryan E Hibbs
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Neurobiology, University of California San Diego, La Jolla, California, USA
| | - Steven M Sine
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota, USA
- Department of Neurology, Mayo Clinic College of Medicine and Science, Rochester, Minnesota, USA
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Iacobucci GJ, Popescu GK. Calcium- and calmodulin-dependent inhibition of NMDA receptor currents. Biophys J 2024; 123:277-293. [PMID: 38140727 PMCID: PMC10870176 DOI: 10.1016/j.bpj.2023.12.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/05/2023] [Accepted: 12/19/2023] [Indexed: 12/24/2023] Open
Abstract
Calcium ions (Ca2+) reduce NMDA receptor currents through several distinct mechanisms. Among these, calmodulin (CaM)-dependent inhibition (CDI) accomplishes rapid, reversible, and incomplete reduction of the NMDA receptor currents in response to elevations in intracellular Ca2+. Quantitative and mechanistic descriptions of CDI of NMDA receptor-mediated signals have been marred by variability originating, in part, from differences in the conditions and metrics used to evaluate this process across laboratories. Recent ratiometric approaches to measure the magnitude and kinetics of NMDA receptor CDI have facilitated rapid insights into this phenomenon. Notably, the kinetics and magnitude of NMDA receptor CDI depend on the degree of saturation of its CaM binding sites, which represent the bona fide calcium sensor for this type of inhibition, the kinetics and magnitude of the Ca2+ signal, which depends on the biophysical properties of the NMDA receptor or of adjacent Ca2+ sources, and on the relative distribution of Ca2+ sources and CaM molecules. Given that all these factors vary widely during development, across cell types, and with physiological and pathological states, it is important to understand how NMDA receptor CDI develops and how it contributes to signaling in the central nervous system. Here, we review briefly these recent advances and highlight remaining questions about the structural and kinetic mechanisms of NMDA receptor CDI. Given that pathologies can arise from several sources, including mutations in the NMDA receptor and in CaM, understanding how CaM responds to intracellular Ca2+ signals to initiate conformational changes in NMDA receptors, and mapping the structural domains responsible will help to envision novel therapeutic strategies to neuropsychiatric diseases, which presently have limited available treatments.
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Affiliation(s)
- Gary J Iacobucci
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, SUNY, Buffalo, New York
| | - Gabriela K Popescu
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, SUNY, Buffalo, New York.
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Chandravanshi LP, Agrawal P, Darwish HW, Trigun SK. Impairments of Spatial Memory and N-methyl-d-aspartate Receptors and Their Postsynaptic Signaling Molecules in the Hippocampus of Developing Rats Induced by As, Pb, and Mn Mixture Exposure. Brain Sci 2023; 13:1715. [PMID: 38137163 PMCID: PMC10742016 DOI: 10.3390/brainsci13121715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 11/24/2023] [Accepted: 11/29/2023] [Indexed: 12/24/2023] Open
Abstract
Exposure to metal mixtures is recognized as a real-life scenario, needing novel studies that can assess their complex effects on brain development. There is still a significant public health concern associated with chronic low levels of metal exposure. In contrast to other metals, these three metals (As, Pb, and Mn) are commonly found in various environmental and industrial contexts. In addition to additive or synergistic interactions, concurrent exposure to this metal mixture may also have neurotoxic effects that differ from those caused by exposure to single components. The NMDA receptor and several important signaling proteins are involved in learning, memory, and synaptic plasticity in the hippocampus, including CaMKII, postsynaptic density protein-95 (PSD-95), synaptic Ras GTPase activating protein (SynGAP), a negative regulator of Ras-MAPK activity, and CREB. We hypothesized that alterations in the above molecular players may contribute to metal mixture developmental neurotoxicity. Thus, the aim of this study was to investigate the effect of these metals and their mixture at low doses (As 4 mg, Pb 4 mg, and Mn 10 mg/kg bw/p.o) on NMDA receptors and their postsynaptic signaling proteins during developing periods (GD6 to PD59) of the rat brain. Rats exposed to As, Pb, and Mn individually or at the same doses in a triple-metal mixture (MM) showed impairments in learning and memory functions in comparison to the control group rats. Declined protein expressions of NR2A, PSD-95, p- CaMKII, and pCREB were observed in the metal mix-exposed rats, while the expression of SynGAP was found to be enhanced in the hippocampus as compared to the controls on PD60. Thereby, our data suggest that alterations in the NMDA receptor complex and postsynaptic signaling proteins could explain the cognitive dysfunctions caused by metal-mixture-induced developmental neurotoxicity in rats. These outcomes indicate that incessant metal mixture exposure may have detrimental consequences on brain development.
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Affiliation(s)
- Lalit P. Chandravanshi
- Department of Forensic Science, Sharda University, Greater Noida 201308, India; (L.P.C.); (P.A.)
| | - Prashant Agrawal
- Department of Forensic Science, Sharda University, Greater Noida 201308, India; (L.P.C.); (P.A.)
| | - Hany W. Darwish
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia
| | - Surendra Kumar Trigun
- Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India
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4
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Zhou J, Xia Y, Li M, Chen Y, Dai J, Liu C, Chen C. A higher dysregulation burden of brain DNA methylation in female patients implicated in the sex bias of Schizophrenia. Mol Psychiatry 2023; 28:4842-4852. [PMID: 37696874 PMCID: PMC10925554 DOI: 10.1038/s41380-023-02243-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 08/17/2023] [Accepted: 08/25/2023] [Indexed: 09/13/2023]
Abstract
Sex differences are pervasive in schizophrenia (SCZ), but the extent and magnitude of DNA methylation (DNAm) changes underlying these differences remain uncharacterized. In this study, sex-stratified differential DNAm analysis was performed in postmortem brain samples from 117 SCZ and 137 controls, partitioned into discovery and replication datasets. Three differentially methylated positions (DMPs) were identified (adj.p < 0.05) in females and 29 DMPs in males without overlap between them. Over 81% of these sex-stratified DMPs were directionally consistent between sexes but with different effect sizes. Females experienced larger magnitude of DNAm changes and more DMPs (based on data of equal sample size) than males, contributing to a higher dysregulation burden of DNAm in females SCZ. Additionally, despite similar proportions of female-related DMPs (fDMPs, 8%) being under genetic control compared with males (10%), significant enrichment of DMP-related single nucleotide polymorphisms (SNPs) in signals of genome-wide association studies was identified only in fDMPs. One DMP in each sex connected the SNPs and gene expression of CALHM1 in females and CCDC149 in males. PPI subnetworks revealed that both female- and male-related differential DNAm interacted with synapse-related dysregulation. Immune-related pathways were unique for females and neuron-related pathways were associated with males. This study reveals remarkable quantitative differences in DNAm-related sexual dimorphism in SCZ and that females have a higher dysregulation burden of SCZ-associated DNAm than males.
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Affiliation(s)
- Jiaqi Zhou
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, and the Department of Psychiatry, The Second Xiangya Hospital, Central South University, Changsha, Hunan, 410078, China
- State Key Laboratory of Genetic Engineering, Human Phenome Institute, and School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Yan Xia
- Department of Medicine, Harvard Medical School, Boston, MA, 02114, USA.
- Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA, 02114, USA.
- Analytic and Translational Genetics unit, Massachusetts General Hospital, Boston, MA, 02114, USA.
| | - Miao Li
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, and the Department of Psychiatry, The Second Xiangya Hospital, Central South University, Changsha, Hunan, 410078, China
| | - Yu Chen
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, and the Department of Psychiatry, The Second Xiangya Hospital, Central South University, Changsha, Hunan, 410078, China
- Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA, 02114, USA
| | - Jiacheng Dai
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, and the Department of Psychiatry, The Second Xiangya Hospital, Central South University, Changsha, Hunan, 410078, China
- State Key Laboratory of Genetic Engineering, Human Phenome Institute, and School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Chunyu Liu
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, and the Department of Psychiatry, The Second Xiangya Hospital, Central South University, Changsha, Hunan, 410078, China.
- Department of Psychiatry, SUNY Upstate Medical University, Syracuse, NY, 13210, USA.
| | - Chao Chen
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, and the Department of Psychiatry, The Second Xiangya Hospital, Central South University, Changsha, Hunan, 410078, China.
- Hunan Key Laboratory of Animal Models for Human Diseases, Central South University, Changsha, Hunan, 410078, China.
- National Clinical Research Center on Mental Disorders, The Second Xiangya Hospital, Central South University, Changsha, Hunan, 410078, China.
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, 410078, China.
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Cobb-Lewis DE, Sansalone L, Khaliq ZM. Contributions of the Sodium Leak Channel NALCN to Pacemaking of Medial Ventral Tegmental Area and Substantia Nigra Dopaminergic Neurons. J Neurosci 2023; 43:6841-6853. [PMID: 37640554 PMCID: PMC10573758 DOI: 10.1523/jneurosci.0930-22.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 08/04/2023] [Accepted: 08/10/2023] [Indexed: 08/31/2023] Open
Abstract
We tested the role of the sodium leak channel, NALCN, in pacemaking of dopaminergic neuron (DAN) subpopulations from adult male and female mice. In situ hybridization revealed NALCN RNA in all DANs, with lower abundance in medial ventral tegmental area (VTA) relative to substantia nigra pars compacta (SNc). Despite lower relative abundance of NALCN, we found that acute pharmacological blockade of NALCN in medial VTA DANs slowed pacemaking by 49.08%. We also examined the electrophysiological properties of projection-defined VTA DAN subpopulations identified by retrograde labeling. Inhibition of NALCN reduced pacemaking in DANs projecting to medial nucleus accumbens (NAc) and others projecting to lateral NAc by 70.74% and 31.98%, respectively, suggesting that NALCN is a primary driver of pacemaking in VTA DANs. In SNc DANs, potentiating NALCN by lowering extracellular calcium concentration speeded pacemaking in wildtype but not NALCN conditional knockout mice, demonstrating functional presence of NALCN. In contrast to VTA DANs, however, pacemaking in SNc DANs was unaffected by inhibition of NALCN. Instead, we found that inhibition of NALCN increased the gain of frequency-current plots at firing frequencies slower than spontaneous firing. Similarly, inhibition of the hyperpolarization-activated cyclic nucleotide-gated (HCN) conductance increased gain but had little effect on pacemaking. Interestingly, simultaneous inhibition of NALCN and HCN resulted in significant reduction in pacemaker rate. Thus, we found NALCN makes substantial contributions to driving pacemaking in VTA DAN subpopulations. In SNc DANs, NALCN is not critical for pacemaking but inhibition of NALCN makes cells more sensitive to hyperpolarizing stimuli.SIGNIFICANCE STATEMENT Pacemaking in midbrain dopaminergic neurons (DAN) relies on multiple subthreshold conductances, including a sodium leak. Whether the sodium leak channel, NALCN, contributes to pacemaking in DANs located in the VTA and the SNc has not yet been determined. Using electrophysiology and pharmacology, we show that NALCN plays a prominent role in driving pacemaking in projection-defined VTA DAN subpopulations. By contrast, pacemaking in SNc neurons does not rely on NALCN. Instead, the presence of NALCN regulates the excitability of SNc DANs by reducing the gain of the neuron's response to inhibitory stimuli. Together, these findings will inform future efforts to obtain DAN subpopulation-specific treatments for use in neuropsychiatric disorders.
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Affiliation(s)
- Dana E Cobb-Lewis
- Cellular Neurophysiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
- Institute for Neuroscience, George Washington University School of Medicine and Health Sciences, Washington, DC 20037
| | - Lorenzo Sansalone
- Cellular Neurophysiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
| | - Zayd M Khaliq
- Cellular Neurophysiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
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6
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Valiente-Gabioud AA, Fabritius A, Griesbeck O. Probing the interstitial calcium compartment. J Physiol 2023; 601:4217-4226. [PMID: 36073135 DOI: 10.1113/jp279510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 08/30/2022] [Indexed: 11/08/2022] Open
Abstract
Calcium in interstitial fluids is a crucial ion pool for entry into cells through a plethora of calcium-permeable channels. It is also sensed actively by dedicated receptors. While the mechanisms of global calcium homeostasis and regulation in body fluids appear well understood, more efforts and new technology are needed to elucidate local calcium handling in the small and relatively isolated interstitial spaces between cells. Here we review current methodology for monitoring interstitial calcium and highlight the potential of new approaches for its study. In particular, new generations of high-performance low-affinity genetically encoded calcium indicators could allow imaging of calcium in relatively inaccessible intercellular structures in live tissues and organisms.
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Affiliation(s)
- Ariel A Valiente-Gabioud
- Tools for Bio-Imaging, Max-Planck-Institute for Biological Intelligence (i.F.), Martinsried, Germany
| | - Arne Fabritius
- Tools for Bio-Imaging, Max-Planck-Institute for Biological Intelligence (i.F.), Martinsried, Germany
| | - Oliver Griesbeck
- Tools for Bio-Imaging, Max-Planck-Institute for Biological Intelligence (i.F.), Martinsried, Germany
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7
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Chen C, Zhou J, Xia Y, Li M, Chen Y, Dai J, Liu C. A Higher Dysregulation Burden of Brain DNA Methylation in Female Patients Implicated in the Sex Bias of Schizophrenia. RESEARCH SQUARE 2023:rs.3.rs-2496133. [PMID: 36778507 PMCID: PMC9915764 DOI: 10.21203/rs.3.rs-2496133/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Sex differences are pervasive in schizophrenia (SCZ), but the extent and magnitude of DNA methylation (DNAm) changes underlying these differences remain uncharacterized. In this study, sex-stratified differential DNAm analysis was performed in postmortem brain samples from 117 SCZ and 137 controls, partitioned into discovery and replication datasets. Three differentially methylated positions (DMPs) were identified (adj. p < 0.05) in females and 29 DMPs in males without overlap between them. Over 81% of these sex-stratified DMPs were directionally consistent between sexes but with different effect sizes. Down-sampling analysis revealed more DMPs in females than in males when the sample sizes matched. Females had higher DNAm levels in healthy individuals and larger magnitude of DNAm changes in patients than males. Despite similar proportions of female-related DMPs (fDMPs, 8%) being under genetic control compared with males (10%), significant enrichment of DMP-related SNPs in signals of genome-wide association studies was identified only in fDMPs. One DMP in each sex connected the SNPs and gene expression of CALHM1 in females and CCDC149 in males. PPI subnetworks revealed that both female- and male-related differential DNAm interacted with synapse-related dysregulation. Immune-related pathways were unique for females and neuron-related pathways were associated with males. This study reveals remarkable quantitative differences in DNAm-related sexual dimorphism in SCZ and that females have a higher dysregulation burden of SCZ-associated DNAm than males.
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8
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2-AG-Mediated Control of GABAergic Signaling Is Impaired in a Model of Epilepsy. J Neurosci 2023; 43:571-583. [PMID: 36460464 PMCID: PMC9888507 DOI: 10.1523/jneurosci.0541-22.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 10/21/2022] [Accepted: 11/25/2022] [Indexed: 12/05/2022] Open
Abstract
Repeated seizures result in a persistent maladaptation of endocannabinoid (eCB) signaling, mediated part by anandamide signaling deficiency in the basolateral amygdala (BLA) that manifests as aberrant synaptic function and altered emotional behavior. Here, we determined the effect of repeated seizures (kindling) on 2-arachidonoylglycerol (2-AG) signaling on GABA transmission by directly measuring tonic and phasic eCB-mediated retrograde signaling in an in vitro BLA slice preparation from male rats. We report that both activity-dependent and muscarinic acetylcholine receptor (mAChR)-mediated depression of GABA synaptic transmission was reduced following repeated seizure activity. These effects were recapitulated in sham rats by preincubating slices with the 2-AG synthesizing enzyme inhibitor DO34. Conversely, preincubating slices with the 2-AG degrading enzyme inhibitor KML29 rescued activity-dependent 2-AG signaling, but not mAChR-mediated synaptic depression, over GABA transmission in kindled rats. These effects were not attributable to a change in cannabinoid type 1 (CB1) receptor sensitivity or altered 2-AG tonic signaling since the application of the highly selective CB1 receptor agonist CP55,940 provoked a similar reduction in GABA synaptic activity in both sham and kindled rats, while no effect of either DO34 or of the CB1 inverse agonist AM251 was observed on frequency and amplitude of spontaneous IPSCs in either sham or kindled rats. Collectively, these data provide evidence that repeated amygdala seizures persistently alter phasic 2-AG-mediated retrograde signaling at BLA GABAergic synapses, probably by impairing stimulus-dependent 2-AG synthesis/release, which contributes to the enduring aberrant synaptic plasticity associated with seizure activity.SIGNIFICANCE STATEMENT The plastic reorganization of endocannabinoid (eCB) signaling after seizures and during epileptogenesis may contribute to the negative neurobiological consequences associated with seizure activity. Therefore, a deeper understanding of the molecular basis underlying the pathologic long-term eCB signaling remodeling following seizure activity will be crucial to the development of novel therapies for epilepsy that not only target seizure activity, but, most importantly, the epileptogenesis and the comorbid conditions associated with epilepsy.
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Huang J, Xu Q, Li Y, He X, Guo Y, Sun X. Activation of Calcium-Sensing Receptor in the Area Postrema Inhibits Food Intake via Glutamatergic and GABAergic Signaling Pathways. Mol Nutr Food Res 2022; 66:e2200245. [PMID: 36281915 DOI: 10.1002/mnfr.202200245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 09/07/2022] [Indexed: 01/18/2023]
Abstract
SCOPE A high-protein diet has become a popular way to lose weight. Calcium-sensing receptor (CaSR) is activated by amino acids in addition to calcium ions. CaSR shows dense expression in the area postrema (AP), which participates in feeding regulation. The effect of CaSR in the AP on food intake and the potential mechanism involved is investigated. METHODS AND RESULTS Male C57BL/6 mice are used to observe the effect of R568 (agonist of CaSR) on food intake. Enzyme-linked immunosorbent assay, immunofluorescence staining, and chemogenetics are used to explore the neural signaling involved. CaSR activation in the AP inhibited acute feeding; R568 increases the content of glutamate and γ-aminobutyric acid (GABA) in the AP, whereas only glutamatergic neurons mediate the effect of R568. GABA-A receptor and ionic glutamate receptor (N-methyl-D-aspartate receptor [NMDAR]) in the paraventricular nucleus of hypothalamus (PVN) are involved in the effect of R568. Promotion of oxytocin (OT) synthesis in the PVN also participates in the effect of R568, and this mechanism is mediated by NMDAR in the PVN. CONCLUSION CaSR activation in the AP suppresses feeding, and AP-PVN glutamatergic and GABAergic signaling pathways are involved.
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Affiliation(s)
- Jinfang Huang
- Department of Physiology and Pathophysiology, School of Basic Medicine, Qingdao University, Qingdao, Shandong, 266071, China
| | - Qian Xu
- Department of Physiology and Pathophysiology, School of Basic Medicine, Qingdao University, Qingdao, Shandong, 266071, China
| | - Yuhang Li
- Department of Physiology and Pathophysiology, School of Basic Medicine, Qingdao University, Qingdao, Shandong, 266071, China
| | - Xiaoman He
- Department of Physiology and Pathophysiology, School of Basic Medicine, Qingdao University, Qingdao, Shandong, 266071, China
| | - Yajie Guo
- Department of Physiology and Pathophysiology, School of Basic Medicine, Qingdao University, Qingdao, Shandong, 266071, China
| | - Xiangrong Sun
- Department of Physiology and Pathophysiology, School of Basic Medicine, Qingdao University, Qingdao, Shandong, 266071, China
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10
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High frequency oscillations play important roles in development of epileptogenesis/ictogenesis via activation of astroglial signallings. Biomed Pharmacother 2022; 149:112846. [PMID: 35325849 DOI: 10.1016/j.biopha.2022.112846] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 03/16/2022] [Accepted: 03/18/2022] [Indexed: 11/24/2022] Open
Abstract
To explore developmental processes of epileptogenesis/ictogenesis and pathophysiology of carbamazepine-resistant epilepsy, we determined effects of high-frequency-oscillation (HFO) on glutamatergic tripartite-synaptic transmission, astroglial expression of connexin43, and intracellular Erk- and Akt-signalling, using genetic rat model (S286L-TG) of autosomal-dominant sleep-related hypermotor epilepsy(ADSHE), which bears rat S286L-mutant Chrna4(corresponding to human S284L-mutant CHRNA4). Artificial physiological ripple- and pathological fast-ripple-burst stimulations use-dependently increased L-glutamate release through connexin43-containing hemichannels by enhancing Erk-signalling alone or both ERK- and Akt-signalling together, respectively. Stimulatory effects of HFO-bursts on astroglial L-glutamate release were enhanced by increasing extracellular K+ levels, Akt- and Erk-signalling-dependently. HFO-bursts also activated connexin43 expression and Akt- and Erk-signallings use-dependently. Extracellular pH elevation enhanced HFO-burst-evoked astroglial L-glutamate release, which was suppressed by therapeutically-relevant concentration of zonisamide via possible carbonic-anhydrase inhibition, but not by that of carbamazepine. Unexpectedly, these responses of S286L-TG to HFO-bursts were almost equal to those of wild-type astrocytes. These results indicated that candidate pathomechanism/pathophysiology of carbamazepine-resistant ADSHE, which enhanced HFO-bursts in S286L-TG neurons may contribute to epileptogenesis/ictogenesis development via activation of connexin43-associated astroglial transmission, which was directly unaffected by mutation, and induced through activated Erk-signalling, followed by Akt-signalling. Therefore, suppression of overexpressed Erk-signalling probably prevents ADSHE onset via indirect inhibition of mutant CHRNA4-associated pathomechanistic developments.
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11
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Tyurikova O, Shih P, Dembitskaya Y, Savtchenko LP, McHugh TJ, Rusakov DA, Semyanov A. K + efflux through postsynaptic NMDA receptors suppresses local astrocytic glutamate uptake. Glia 2022; 70:961-974. [PMID: 35084774 PMCID: PMC9132042 DOI: 10.1002/glia.24150] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 01/14/2022] [Accepted: 01/14/2022] [Indexed: 12/31/2022]
Abstract
Glutamatergic transmission prompts K+ efflux through postsynaptic NMDA receptors. The ensuing hotspot of extracellular K+ elevation depolarizes presynaptic terminal, boosting glutamate release, but whether this also affects glutamate uptake in local astroglia has remained an intriguing question. Here, we find that the pharmacological blockade, or conditional knockout, of postsynaptic NMDA receptors suppresses use-dependent increase in the amplitude and duration of the astrocytic glutamate transporter current (IGluT ), whereas blocking astrocytic K+ channels prevents the duration increase only. Glutamate spot-uncaging reveals that astrocyte depolarization, rather than extracellular K+ rises per se, is required to reduce the amplitude and duration of IGluT . Biophysical simulations confirm that local transient elevations of extracellular K+ can inhibit local glutamate uptake in fine astrocytic processes. Optical glutamate sensor imaging and a two-pathway test relate postsynaptic K+ efflux to enhanced extrasynaptic glutamate signaling. Thus, repetitive glutamatergic transmission triggers a feedback loop in which postsynaptic K+ efflux can transiently facilitate presynaptic release while reducing local glutamate uptake.
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Affiliation(s)
- Olga Tyurikova
- Shemyakin‐Ovchinnikov Institute of Bioorganic ChemistryRussian Academy of SciencesMoscowRussia
- Department of Clinical and Experimental EpilepsyUCL Institute of Neurology, Queen SquareLondonUK
- Brain Science Institute (BSI)RIKENWako‐shiSaitamaJapan
| | - Pei‐Yu Shih
- Brain Science Institute (BSI)RIKENWako‐shiSaitamaJapan
| | - Yulia Dembitskaya
- Shemyakin‐Ovchinnikov Institute of Bioorganic ChemistryRussian Academy of SciencesMoscowRussia
- Brain Science Institute (BSI)RIKENWako‐shiSaitamaJapan
| | - Leonid P. Savtchenko
- Department of Clinical and Experimental EpilepsyUCL Institute of Neurology, Queen SquareLondonUK
| | - Thomas J. McHugh
- Brain Science Institute (BSI)RIKENWako‐shiSaitamaJapan
- RIKEN Center for Brain Science, Wako‐shiSaitamaJapan
| | - Dmitri A. Rusakov
- Department of Clinical and Experimental EpilepsyUCL Institute of Neurology, Queen SquareLondonUK
| | - Alexey Semyanov
- Shemyakin‐Ovchinnikov Institute of Bioorganic ChemistryRussian Academy of SciencesMoscowRussia
- Brain Science Institute (BSI)RIKENWako‐shiSaitamaJapan
- Department of Clinical Pharmacology, Sechenov First Moscow State Medical UniversityMoscowRussia
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12
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Cherkashin AP, Rogachevskaja OA, Kabanova NV, Kotova PD, Bystrova MF, Kolesnikov SS. Taste Cells of the Type III Employ CASR to Maintain Steady Serotonin Exocytosis at Variable Ca 2+ in the Extracellular Medium. Cells 2022; 11:cells11081369. [PMID: 35456048 PMCID: PMC9030112 DOI: 10.3390/cells11081369] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 04/07/2022] [Accepted: 04/11/2022] [Indexed: 12/17/2022] Open
Abstract
Type III taste cells are the only taste bud cells which express voltage-gated (VG) Ca2+ channels and employ Ca2+-dependent exocytosis to release neurotransmitters, particularly serotonin. The taste bud is a tightly packed cell population, wherein extracellular Ca2+ is expected to fluctuate markedly due to the electrical activity of taste cells. It is currently unclear whether the Ca2+ entry-driven synapse in type III cells could be reliable enough at unsteady extracellular Ca2. Here we assayed depolarization-induced Ca2+ signals and associated serotonin release in isolated type III cells at varied extracellular Ca2+. It turned out that the same depolarizing stimulus elicited invariant Ca2+ signals in type III cells irrespective of bath Ca2+ varied within 0.5–5 mM. The serotonin release from type III cells was assayed with the biosensor approach by using HEK-293 cells co-expressing the recombinant 5-HT4 receptor and genetically encoded cAMP sensor Pink Flamindo. Consistently with the weak Ca2+ dependence of intracellular Ca2+ transients produced by VG Ca2+ entry, depolarization-triggered serotonin secretion varied negligibly with bath Ca2+. The evidence implicated the extracellular Ca2+-sensing receptor in mediating the negative feedback mechanism that regulates VG Ca2+ entry and levels off serotonin release in type III cells at deviating Ca2+ in the extracellular medium.
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13
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Selenium Effects on Oxidative Stress-Induced Calcium Signaling Pathways in Parkinson’s Disease. Indian J Clin Biochem 2022; 37:257-266. [DOI: 10.1007/s12291-022-01031-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 03/02/2022] [Indexed: 02/07/2023]
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14
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Mazzaferro S, Strikwerda JR, Sine SM. Stoichiometry-selective modulation of α4β2 nicotinic ACh receptors by divalent cations. Br J Pharmacol 2022; 179:1353-1370. [PMID: 34768309 DOI: 10.1111/bph.15723] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 10/11/2021] [Accepted: 10/18/2021] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND AND PURPOSE α4β2 nicotinic ACh receptors (nAChRs) comprise the most abundant class of nAChRs in the nervous system. They assemble in two stoichiometric forms, each exhibiting distinct functional and pharmacological signatures. However, whether one or both forms are modulated by calcium or magnesium has not been established. EXPERIMENTAL APPROACH To assess the functional consequences of calcium and magnesium, each stoichiometric form was expressed in clonal mammalian fibroblasts and single-channel currents were recorded in the presence of a range of ACh concentrations. KEY RESULTS In the absence of divalent cations, each stoichiometric form exhibits high unitary conductance and simple gating kinetics composed of solitary channel openings or short bursts of openings. However, in the presence of calcium and magnesium, the conductance and gating kinetics change in a stoichiometry-dependent manner. Calcium and magnesium reduce the conductance of both stoichiometric forms, with each cation producing an equivalent reduction, but the reduction is greater for the (α4)2 (β2)3 form. Moreover, divalent cations promote efficient channel opening of the (α4)3 (β2)2 stoichiometry, while minimally affecting the (α4)2 (β2)3 stoichiometry. For the (α4)3 (β2)2 stoichiometry, at high but not low ACh concentrations, calcium in synergy with magnesium promote clustering of channel openings into episodes of many openings in quick succession. CONCLUSION AND IMPLICATIONS Modulation of the α4β2 nAChR by divalent cations depends on the ACh concentration, the type of cation and the subunit stoichiometry. The functional consequences of modulation are expected to depend on the regional distributions of the stoichiometric forms and synaptic versus extrasynaptic locations of the receptors.
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Affiliation(s)
- Simone Mazzaferro
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
| | - John R Strikwerda
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
| | - Steven M Sine
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.,Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.,Department of Neurology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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15
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Yeh SCA, Hou J, Wu JW, Yu S, Zhang Y, Belfield KD, Camargo FD, Lin CP. Quantification of bone marrow interstitial pH and calcium concentration by intravital ratiometric imaging. Nat Commun 2022; 13:393. [PMID: 35046411 PMCID: PMC8770570 DOI: 10.1038/s41467-022-27973-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 12/22/2021] [Indexed: 12/23/2022] Open
Abstract
The fate of hematopoietic stem cells (HSCs) can be directed by microenvironmental factors including extracellular calcium ion concentration ([Ca2+]e), but the local [Ca2+]e around individual HSCs in vivo remains unknown. Here we develop intravital ratiometric analyses to quantify the absolute pH and [Ca2+]e in the mouse calvarial bone marrow, taking into account the pH sensitivity of the calcium probe and the wavelength-dependent optical loss through bone. Unexpectedly, the mean [Ca2+]e in the bone marrow (1.0 ± 0.54 mM) is not significantly different from the blood serum, but the HSCs are found in locations with elevated local [Ca2+]e (1.5 ± 0.57 mM). With aging, a significant increase in [Ca2+]e is found in M-type cavities that exclusively support clonal expansion of activated HSCs. This work thus establishes a tool to investigate [Ca2+]e and pH in the HSC niche with high spatial resolution and can be broadly applied to other tissue types.
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Affiliation(s)
- S-C A Yeh
- Advanced Microscopy Program, Center for Systems Biology and Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA
| | - J Hou
- Advanced Microscopy Program, Center for Systems Biology and Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA
| | - J W Wu
- Advanced Microscopy Program, Center for Systems Biology and Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA
| | - S Yu
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, 323 Martin Luther King Jr. Blvd., Newark, NJ, 07102, USA
| | - Y Zhang
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, 323 Martin Luther King Jr. Blvd., Newark, NJ, 07102, USA
| | - K D Belfield
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, 323 Martin Luther King Jr. Blvd., Newark, NJ, 07102, USA
| | - F D Camargo
- Stem Cell Program, Boston Children's Hospital, Boston, MA, USA
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA, USA
| | - C P Lin
- Advanced Microscopy Program, Center for Systems Biology and Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA.
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, 02138, USA.
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16
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Verkhratsky A, Parpura V, Li B, Scuderi C. Astrocytes: The Housekeepers and Guardians of the CNS. ADVANCES IN NEUROBIOLOGY 2021; 26:21-53. [PMID: 34888829 DOI: 10.1007/978-3-030-77375-5_2] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Astroglia are a diverse group of cells in the central nervous system. They are of the ectodermal, neuroepithelial origin and vary in morphology and function, yet, they can be collectively defined as cells having principle function to maintain homeostasis of the central nervous system at all levels of organisation, including homeostasis of ions, pH and neurotransmitters; supplying neurones with metabolic substrates; supporting oligodendrocytes and axons; regulating synaptogenesis, neurogenesis, and formation and maintenance of the blood-brain barrier; contributing to operation of the glymphatic system; and regulation of systemic homeostasis being central chemosensors for oxygen, CO2 and Na+. Their basic physiological features show a lack of electrical excitability (inapt to produce action potentials), but display instead a rather active excitability based on variations in cytosolic concentrations of Ca2+ and Na+. It is expression of neurotransmitter receptors, pumps and transporters at their plasmalemma, along with transports on the endoplasmic reticulum and mitochondria that exquisitely regulate the cytosolic levels of these ions, the fluctuation of which underlies most, if not all, astroglial homeostatic functions.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.
- Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Baoman Li
- Department of Forensic Analytical Toxicology, School of Forensic Medicine, China Medical University, Shenyang, China
| | - Caterina Scuderi
- Department of Physiology and Pharmacology "Vittorio Erspamer", SAPIENZA University of Rome, Rome, Italy
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17
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Natarajan K, Mukhtasimova N, Corradi J, Lasala M, Bouzat C, Sine SM. Mechanism of calcium potentiation of the α7 nicotinic acetylcholine receptor. J Gen Physiol 2021; 152:151971. [PMID: 32702089 PMCID: PMC7478872 DOI: 10.1085/jgp.202012606] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 05/19/2020] [Accepted: 06/22/2020] [Indexed: 12/14/2022] Open
Abstract
The α7 nicotinic acetylcholine receptor (nAChR) is among the most abundant types of nAChR in the brain, yet the ability of nerve-released ACh to activate α7 remains enigmatic. In particular, a major population of α7 resides in extra-synaptic regions where the ACh concentration is reduced, owing to dilution and enzymatic hydrolysis, yet ACh shows low potency in activating α7. Using high-resolution single-channel recording techniques, we show that extracellular calcium is a powerful potentiator of α7 activated by low concentrations of ACh. Potentiation manifests as robust increases in the frequency of channel opening and the average duration of the openings. Molecular dynamics simulations reveal that calcium binds to the periphery of the five ligand binding sites and is framed by a pair of anionic residues from the principal and complementary faces of each site. Mutation of residues identified by simulation prevents calcium from potentiating ACh-elicited channel opening. An anionic residue is conserved at each of the identified positions in all vertebrate species of α7. Thus, calcium associates with a novel structural motif on α7 and is an obligate cofactor in regions of limited ACh concentration.
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Affiliation(s)
- Kathiresan Natarajan
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN
| | - Nuriya Mukhtasimova
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN
| | - Jeremías Corradi
- Instituto de Investigaciones Bioquímicas, Departamento de Biologia, Bioquimica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina
| | - Matías Lasala
- Instituto de Investigaciones Bioquímicas, Departamento de Biologia, Bioquimica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina
| | - Cecilia Bouzat
- Instituto de Investigaciones Bioquímicas, Departamento de Biologia, Bioquimica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina
| | - Steven M Sine
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN.,Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN.,Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN
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18
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Kopach O, Esteras N, Wray S, Abramov AY, Rusakov DA. Genetically engineered MAPT 10+16 mutation causes pathophysiological excitability of human iPSC-derived neurons related to 4R tau-induced dementia. Cell Death Dis 2021; 12:716. [PMID: 34274950 PMCID: PMC8286258 DOI: 10.1038/s41419-021-04007-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 07/07/2021] [Accepted: 07/08/2021] [Indexed: 01/02/2023]
Abstract
Human iPSC lines represent a powerful translational model of tauopathies. We have recently described a pathophysiological phenotype of neuronal excitability of human cells derived from the patients with familial frontotemporal dementia and parkinsonism (FTDP-17) caused by the MAPT 10+16 splice-site mutation. This mutation leads to the increased splicing of 4R tau isoforms. However, the role of different isoforms of tau protein in initiating neuronal dementia-related dysfunction, and the causality between the MAPT 10+16 mutation and altered neuronal activity have remained unclear. Here, we employed genetically engineered cells, in which the IVS10+16 mutation was introduced into healthy donor iPSCs to increase the expression of 4R tau isoform in exon 10, aiming to explore key physiological traits of iPSC-derived MAPT IVS10+16 neurons using patch-clamp electrophysiology and multiphoton fluorescent imaging techniques. We found that during late in vitro neurogenesis (from ~180 to 230 days) iPSC-derived cortical neurons of the control group (parental wild-type tau) exhibited membrane properties compatible with "mature" neurons. In contrast, MAPT IVS10+16 neurons displayed impaired excitability, as reflected by a depolarized resting membrane potential, an increased input resistance, and reduced voltage-gated Na+- and K+-channel-mediated currents. The mutation changed the channel properties of fast-inactivating Nav and decreased the Nav1.6 protein level. MAPT IVS10+16 neurons exhibited reduced firing accompanied by a changed action potential waveform and severely disturbed intracellular Ca2+ dynamics, both in the soma and dendrites, upon neuronal depolarization. These results unveil a causal link between the MAPT 10+16 mutation, hence overproduction of 4R tau, and a dysfunction of human cells, identifying a biophysical basis of changed neuronal activity in 4R tau-triggered dementia. Our study lends further support to using iPSC lines as a suitable platform for modelling tau-induced human neuropathology in vitro.
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Affiliation(s)
- Olga Kopach
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK.
| | - Noemí Esteras
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
| | - Selina Wray
- Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, London, UK
| | - Andrey Y Abramov
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
| | - Dmitri A Rusakov
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK
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19
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Chanaday NL, Nosyreva E, Shin OH, Zhang H, Aklan I, Atasoy D, Bezprozvanny I, Kavalali ET. Presynaptic store-operated Ca 2+ entry drives excitatory spontaneous neurotransmission and augments endoplasmic reticulum stress. Neuron 2021; 109:1314-1332.e5. [PMID: 33711258 PMCID: PMC8068669 DOI: 10.1016/j.neuron.2021.02.023] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 01/18/2021] [Accepted: 02/19/2021] [Indexed: 12/11/2022]
Abstract
Store-operated calcium entry (SOCE) is activated by depletion of Ca2+ from the endoplasmic reticulum (ER) and mediated by stromal interaction molecule (STIM) proteins. Here, we show that in rat and mouse hippocampal neurons, acute ER Ca2+ depletion increases presynaptic Ca2+ levels and glutamate release through a pathway dependent on STIM2 and the synaptic Ca2+ sensor synaptotagmin-7 (syt7). In contrast, synaptotagmin-1 (syt1) can suppress SOCE-mediated spontaneous release, and STIM2 is required for the increase in spontaneous release seen during syt1 loss of function. We also demonstrate that chronic ER stress activates the same pathway leading to syt7-dependent potentiation of spontaneous glutamate release. During ER stress, inhibition of SOCE or syt7-driven fusion partially restored basal neurotransmission and decreased expression of pro-apoptotic markers, indicating that these processes participate in the amplification of ER-stress-related damage. Taken together, we propose that presynaptic SOCE links ER stress and augmented spontaneous neurotransmission, which may, in turn, facilitate neurodegeneration.
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Affiliation(s)
- Natali L. Chanaday
- Department of Pharmacology, School of Medicine, Vanderbilt University, Nashville, TN, 37240-7933, USA
| | - Elena Nosyreva
- Department of Neuroscience, The University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Ok-Ho Shin
- Department of Pharmacology, School of Medicine, Vanderbilt University, Nashville, TN, 37240-7933, USA
| | - Hua Zhang
- Department of Physiology, The University of Texas Southwestern Medical Center, Dallas, TX 75390-9040, USA
| | - Iltan Aklan
- Department of Neuroscience and Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Deniz Atasoy
- Department of Neuroscience and Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA,Iowa Neuroscience Institute, University of Iowa, Iowa City, IA, 52242, USA,FOE Diabetes Research Center, University of Iowa, Iowa City, IA, 52242, USA
| | - Ilya Bezprozvanny
- Department of Physiology, The University of Texas Southwestern Medical Center, Dallas, TX 75390-9040, USA.,Laboratory of Molecular Neurodegeneration, Peter the Great St Petersburg State Polytechnic University, St. Petersburg, Russia
| | - Ege T. Kavalali
- Department of Pharmacology, School of Medicine, Vanderbilt University, Nashville, TN, 37240-7933, USA.,Vanderbilt Brain Institute.,Corresponding author: Ege T. Kavalali, Ph.D., Department of Pharmacology, Vanderbilt University, 465 21st Avenue South, 7130A MRBIII, PMB407933 Nashville, TN 37240-7933, phone: 615-343-5480,
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20
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Lim D, Semyanov A, Genazzani A, Verkhratsky A. Calcium signaling in neuroglia. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 362:1-53. [PMID: 34253292 DOI: 10.1016/bs.ircmb.2021.01.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Glial cells exploit calcium (Ca2+) signals to perceive the information about the activity of the nervous tissue and the tissue environment to translate this information into an array of homeostatic, signaling and defensive reactions. Astrocytes, the best studied glial cells, use several Ca2+ signaling generation pathways that include Ca2+ entry through plasma membrane, release from endoplasmic reticulum (ER) and from mitochondria. Activation of metabotropic receptors on the plasma membrane of glial cells is coupled to an enzymatic cascade in which a second messenger, InsP3 is generated thus activating intracellular Ca2+ release channels in the ER endomembrane. Astrocytes also possess store-operated Ca2+ entry and express several ligand-gated Ca2+ channels. In vivo astrocytes generate heterogeneous Ca2+ signals, which are short and frequent in distal processes, but large and relatively rare in soma. In response to neuronal activity intracellular and inter-cellular astrocytic Ca2+ waves can be produced. Astrocytic Ca2+ signals are involved in secretion, they regulate ion transport across cell membranes, and are contributing to cell morphological plasticity. Therefore, astrocytic Ca2+ signals are linked to fundamental functions of the central nervous system ranging from synaptic transmission to behavior. In oligodendrocytes, Ca2+ signals are generated by plasmalemmal Ca2+ influx, or by release from intracellular stores, or by combination of both. Microglial cells exploit Ca2+ permeable ionotropic purinergic receptors and transient receptor potential channels as well as ER Ca2+ release. In this contribution, basic morphology of glial cells, glial Ca2+ signaling toolkit, intracellular Ca2+ signals and Ca2+-regulated functions are discussed with focus on astrocytes.
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Affiliation(s)
- Dmitry Lim
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale, Novara, Italy.
| | - Alexey Semyanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia; Faculty of Biology, Moscow State University, Moscow, Russia; Sechenov First Moscow State Medical University, Moscow, Russia
| | - Armando Genazzani
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale, Novara, Italy
| | - Alexei Verkhratsky
- Sechenov First Moscow State Medical University, Moscow, Russia; Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom; Achucarro Centre for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
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21
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Jeon YK, Choi SW, Kwon JW, Woo J, Choi SW, Kim SJ, Kim SJ. Thermosensitivity of the voltage-dependent activation of calcium homeostasis modulator 1 (calhm1) ion channel. Biochem Biophys Res Commun 2020; 534:590-596. [PMID: 33199024 DOI: 10.1016/j.bbrc.2020.11.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 11/08/2020] [Indexed: 01/08/2023]
Abstract
Calcium homeostasis modulator 1 (calhm1) proteins form an outwardly rectifying nonselective ion channel having exceedingly slow kinetics and low sensitivity to voltage that is shifted by lowering extracellular Ca2+ ([Ca2+]e). Here we found that physiological temperature dramatically facilitates the voltage-dependent activation of the calhm1 current (Icalhm1); increased amplitude (Q10, 7-15) and fastened speed of activation. Also, the leftward shift of the half-activation voltage (V1/2) was similary observed in the normal and lower [Ca2+]e. Since calhm1 is highly expressed in the brain and taste cells, the thermosensitivity should be considered in their electrophysiology.
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Affiliation(s)
- Young Keul Jeon
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea
| | - Si Won Choi
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea
| | - Jae Won Kwon
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea
| | - Joohan Woo
- Department of Physiology and Ion Channel Disease Research Center, Dongguk University College of Medicine, Seoul, Republic of Korea
| | - Seong Woo Choi
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Sang Jeong Kim
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea
| | - Sung Joon Kim
- Department of Physiology, Seoul National University College of Medicine, Republic of Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Republic of Korea.
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22
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Rasmussen R, O'Donnell J, Ding F, Nedergaard M. Interstitial ions: A key regulator of state-dependent neural activity? Prog Neurobiol 2020; 193:101802. [PMID: 32413398 PMCID: PMC7331944 DOI: 10.1016/j.pneurobio.2020.101802] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 03/24/2020] [Accepted: 03/26/2020] [Indexed: 02/08/2023]
Abstract
Throughout the nervous system, ion gradients drive fundamental processes. Yet, the roles of interstitial ions in brain functioning is largely forgotten. Emerging literature is now revitalizing this area of neuroscience by showing that interstitial cations (K+, Ca2+ and Mg2+) are not static quantities but change dynamically across states such as sleep and locomotion. In turn, these state-dependent changes are capable of sculpting neuronal activity; for example, changing the local interstitial ion composition in the cortex is sufficient for modulating the prevalence of slow-frequency neuronal oscillations, or potentiating the gain of visually evoked responses. Disturbances in interstitial ionic homeostasis may also play a central role in the pathogenesis of central nervous system diseases. For example, impairments in K+ buffering occur in a number of neurodegenerative diseases, and abnormalities in neuronal activity in disease models disappear when interstitial K+ is normalized. Here we provide an overview of the roles of interstitial ions in physiology and pathology. We propose the brain uses interstitial ion signaling as a global mechanism to coordinate its complex activity patterns, and ion homeostasis failure contributes to central nervous system diseases affecting cognitive functions and behavior.
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Affiliation(s)
- Rune Rasmussen
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
| | - John O'Donnell
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, United States
| | - Fengfei Ding
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, United States
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark; Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, United States.
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23
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Sylantyev S, Savtchenko LP, O'Neill N, Rusakov DA. Extracellular GABA waves regulate coincidence detection in excitatory circuits. J Physiol 2020; 598:4047-4062. [PMID: 32667048 PMCID: PMC8432164 DOI: 10.1113/jp279744] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 07/09/2020] [Indexed: 11/23/2022] Open
Abstract
KEY POINTS Rapid changes in neuronal network activity trigger widespread waves of extracellular GABA in hippocampal neuropil. Elevations of extracellular GABA narrow the coincidence detection window for excitatory inputs to CA1 pyramidal cells. GABA transporters control the effect of extracellular GABA on coincidence detection. Small changes in the kinetics of dendritic excitatory currents amplify when reaching the soma. ABSTRACT Coincidence detection of excitatory inputs by principal neurons underpins the rules of signal integration and Hebbian plasticity in the brain. In the hippocampal circuitry, detection fidelity is thought to depend on the GABAergic synaptic input through a feedforward inhibitory circuit also involving the hyperpolarisation-activated Ih current. However, afferent connections often bypass feedforward circuitry, suggesting that a different GABAergic mechanism might control coincidence detection in such cases. To test whether fluctuations in the extracellular GABA concentration [GABA] could play a regulatory role here, we use a GABA 'sniffer' patch in acute hippocampal slices of the rat and document strong dependence of [GABA] on network activity. We find that blocking GABAergic signalling strongly widens the coincidence detection window of direct excitatory inputs to pyramidal cells whereas increasing [GABA] through GABA uptake blockade shortens it. The underlying mechanism involves membrane-shunting tonic GABAA receptor current; it does not have to rely on Ih but depends strongly on the neuronal GABA transporter GAT-1. We use dendrite-soma dual patch-clamp recordings to show that the strong effect of membrane shunting on coincidence detection relies on nonlinear amplification of changes in the decay of dendritic synaptic currents when they reach the soma. Our results suggest that, by dynamically regulating extracellular GABA, brain network activity can optimise signal integration rules in local excitatory circuits.
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Affiliation(s)
- Sergiy Sylantyev
- Rowett InstituteUniversity of AberdeenAshgrove Rd. WestAberdeenAB25 2ZDUK
- UCL Queen Square Institute of NeurologyUniversity College LondonQueen SquareLondonWC1N 3BGUK
| | - Leonid P. Savtchenko
- UCL Queen Square Institute of NeurologyUniversity College LondonQueen SquareLondonWC1N 3BGUK
| | - Nathanael O'Neill
- Centre for Clinical Brain SciencesUniversity of Edinburgh49 Little France CrescentEdinburghEH16 4SBUK
| | - Dmitri A. Rusakov
- UCL Queen Square Institute of NeurologyUniversity College LondonQueen SquareLondonWC1N 3BGUK
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Fukuyama K, Ueda Y, Okada M. Effects of Carbamazepine, Lacosamide and Zonisamide on Gliotransmitter Release Associated with Activated Astroglial Hemichannels. Pharmaceuticals (Basel) 2020; 13:ph13060117. [PMID: 32516974 PMCID: PMC7345221 DOI: 10.3390/ph13060117] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 05/23/2020] [Accepted: 06/03/2020] [Indexed: 12/14/2022] Open
Abstract
Recent studies using the genetic partial epilepsy model have demonstrated that hyperfunction of astroglial hemichannels contributes to pathomechanism of epileptic seizure. Therefore, to explore the novel anticonvulsive mechanisms, the present study determined the effects of voltage-dependent Na+ channel (VDSC)-inhibiting anticonvulsants, carbamazepine (CBZ), lacosamide (LCM), and zonisamide (ZNS) on the astroglial release of l-glutamate and adenosine triphosphate (ATP). The effects of subchronic administration of therapeutic-relevant dose of three anticonvulsants on the release of l-glutamate and ATP in the orbitofrontal cortex (OFC) were determined using microdialysis. The concentration-dependent effects of acute and subchronic administrations of anticonvulsants on astroglial gliotransmitter release were determined using primary cultured astrocytes. The concentration-dependent effects of subchronic administrations of anticonvulsants on connexin43 (Cx43) expression in the plasma membrane of primary cultured astrocytes were determined using the Simple Western system. An increase in the levels of extracellular K+ resulted in a concentration-dependent increase in the astroglial release of l-glutamate and ATP. The depleted levels of extracellular Ca2+ alone did not affect astroglial gliotransmitter release but did accelerate K+-evoked gliotransmitter release via activation of astroglial hemichannels. Both non-selective hemichannel inhibitor carbenoxolone (CBX) and selective Cx43 inhibitor GAP19 prevented both gliotransmitter release through activated astroglial hemichannels and the hemichannel-activating process induced by elevation of the levels of extracellular K+ with depletion of the levels of extracellular Ca2+. ZNS subchronically decreased Cx43 expression and acutely/subchronically inhibited Cx43 hemichannel activity. LCM acutely inhibited hemichannel activity but did not subchronically affect Cx43 expression. Therapeutic-relevant concentration of CBZ did not affect hemichannel activity or Cx43 expression, but supratherapeutic concentration of CBZ decreased Cx43 expression and hemichannel activity. Therefore, the present study demonstrated the distinct effects of CBZ, LCM, and ZNS on gliotransmitter release via modulation of astroglial hemichannel function. The different features of the effects of three VDSC-inhibiting anticonvulsants on astroglial transmission associated with hemichannels, at least partially, possibly contributing to the formation of the properties of these three anticonvulsants, including the antiepileptic spectrum and adverse effects regarding mood and cognitive disturbance.
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Upregulated and Hyperactivated Thalamic Connexin 43 Plays Important Roles in Pathomechanisms of Cognitive Impairment and Seizure of Autosomal Dominant Sleep-Related Hypermotor Epilepsy with S284L-Mutant α4 Subunit of Nicotinic ACh Receptor. Pharmaceuticals (Basel) 2020; 13:ph13050099. [PMID: 32443400 PMCID: PMC7280967 DOI: 10.3390/ph13050099] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 04/26/2020] [Accepted: 05/08/2020] [Indexed: 01/07/2023] Open
Abstract
To understand the pathomechanism and pathophysiology of autosomal dominant sleep-related hypermotor epilepsy (ADSHE), we studied functional abnormalities of glutamatergic transmission in thalamocortical pathway from reticular thalamic nucleus (RTN), mediodorsal thalamic nucleus (MDTN) to orbitofrontal cortex (OFC) associated with S286L-mutant α4β2-nicotinic acetylcholine receptor (nAChR), and connexin43 (Cx43) hemichannel of transgenic rats bearing rat S286L-mutant Chrna4 gene (S286L-TG), corresponding to the human S284L-mutant CHRNA4 gene using simple Western analysis and multiprobe microdialysis. Cx43 expression in the thalamic plasma membrane fraction of S286L-TG was upregulated compared with that of wild-type. Subchronic administrations of therapeutic-relevant doses of zonisamide (ZNS) and carbamazepine (CBZ) decreased and did not affect Cx43 expression of S286L-TG, respectively. Upregulated Cx43 enhanced glutamatergic transmission during both resting and hyperexcitable stages in S286L-TG. Furthermore, activation of GABAergic transmission RTN-MDTN pathway conversely enhanced, but not inhibited, l-glutamate release in the MDTN via upregulated/activated Cx43. Local administration of therapeutic-relevant concentration of ZNS and CBZ acutely supressed and did not affect glutamatergic transmission in the thalamocortical pathway, respectively. These results suggest that pathomechanisms of ADSHE seizure and its cognitive deficit comorbidity, as well as pathophysiology of CBZ-resistant/ZNS-sensitive ADSHE seizures of patients with S284L-mutation.
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Dukes MP, Rowe RK, Harvey T, Rangel W, Pedigo S. Nickel reduces calcium dependent dimerization in neural cadherin. Metallomics 2020; 11:475-482. [PMID: 30624456 DOI: 10.1039/c8mt00349a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cadherins are the transmembrane component in adherens junctions, structures that link the actin cytoskeletons in adjacent cells within solid tissues including neurological synapses, epithelium and endothelium. Cell-cell adhesion by cadherins requires the binding of calcium ions to specific sites in the extracellular region. Given the complexity of the cell adhesion microenvironment, we are investigating whether other divalent cations might affect calcium-dependent dimerization of neural (N) cadherin. The studies reported herein characterize the impact of binding physiological magnesium(ii) or neurotoxic nickel(ii) on calcium-dependent N-cadherin function. Physiological levels of magnesium have only a small effect on the calcium-binding affinity and calcium-induced dimerization of N-cadherin. However, a tenfold lower concentration of nickel decreases the apparent calcium-binding affinity and calcium-induced dimerization of N-cadherin. Competitive binding studies indicate that the apparent dissociation constants for nickel and magnesium are 0.2 mM and 2.5 mM, respectively. These Kd values are consistent with concentrations observed for a range of divalent cations in the extracellular space. Results from these studies indicate that calcium-induced dimerization by N-cadherin is attenuated by natural and non-physiological divalent cations in the extracellular microenvironment.
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Affiliation(s)
- M P Dukes
- Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA.
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27
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Pronker MF, van den Hoek H, Janssen BJC. Design and structural characterisation of olfactomedin-1 variants as tools for functional studies. BMC Mol Cell Biol 2019; 20:50. [PMID: 31726976 PMCID: PMC6857237 DOI: 10.1186/s12860-019-0232-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 10/10/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Olfactomedin-1 (Olfm1; also known as Noelin or Pancortin) is a highly-expressed secreted brain and retina protein and its four isoforms have different roles in nervous system development and function. Structural studies showed that the long Olfm1 isoform BMZ forms a disulfide-linked tetramer with a V-shaped architecture. The tips of the Olfm1 "V" each consist of two C-terminal β-propeller domains that enclose a calcium binding site. Functional characterisation of Olfm1 may be aided by new biochemical tools derived from these core structural elements. RESULTS Here we present the production, purification and structural analysis of three novel monomeric, dimeric and tetrameric forms of mammalian Olfm1 for functional studies. We characterise these constructs structurally by high-resolution X-ray crystallography and small-angle X-ray scattering. The crystal structure of the Olfm1 β-propeller domain (to 1.25 Å) represents the highest-resolution structure of an olfactomedin family member to date, revealing features such as a hydrophilic tunnel containing water molecules running into the core of the domain where the calcium binding site resides. The shorter Olfactomedin-1 isoform BMY is a disulfide-linked tetramer with a shape similar to the corresponding region in the longer BMZ isoform. CONCLUSIONS These recombinantly-expressed protein tools should assist future studies, for example of biophysical, electrophysiological or morphological nature, to help elucidate the functions of Olfm1 in the mature mammalian brain. The control over the oligomeric state of Olfm1 provides a firm basis to better understand the role of Olfm1 in the (trans-synaptic) tethering or avidity-mediated clustering of synaptic receptors such as post-synaptic AMPA receptors and pre-synaptic amyloid precursor protein. In addition, the variation in domain composition of these protein tools provides a means to dissect the Olfm1 regions important for receptor binding.
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Affiliation(s)
- Matti F Pronker
- MRC Laboratory of Molecular Biology, Division of Neurobiology, Francis Crick Avenue, Cambridge, CB2 0QH, UK. .,Bijvoet Center for Biomolecular Research, Utrecht University, Crystal and Structural Chemistry, Kruytgebouw, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
| | - Hugo van den Hoek
- Bijvoet Center for Biomolecular Research, Utrecht University, Crystal and Structural Chemistry, Kruytgebouw, Padualaan 8, 3584 CH, Utrecht, The Netherlands.,Department of Molecular Structural Biology, Max Planck institute for Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany
| | - Bert J C Janssen
- Bijvoet Center for Biomolecular Research, Utrecht University, Crystal and Structural Chemistry, Kruytgebouw, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
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Roles for the Endoplasmic Reticulum in Regulation of Neuronal Calcium Homeostasis. Cells 2019; 8:cells8101232. [PMID: 31658749 PMCID: PMC6829861 DOI: 10.3390/cells8101232] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 10/01/2019] [Accepted: 10/03/2019] [Indexed: 02/06/2023] Open
Abstract
By influencing Ca2+ homeostasis in spatially and architecturally distinct neuronal compartments, the endoplasmic reticulum (ER) illustrates the notion that form and function are intimately related. The contribution of ER to neuronal Ca2+ homeostasis is attributed to the organelle being the largest reservoir of intracellular Ca2+ and having a high density of Ca2+ channels and transporters. As such, ER Ca2+ has incontrovertible roles in the regulation of axodendritic growth and morphology, synaptic vesicle release, and neural activity dependent gene expression, synaptic plasticity, and mitochondrial bioenergetics. Not surprisingly, many neurological diseases arise from ER Ca2+ dyshomeostasis, either directly due to alterations in ER resident proteins, or indirectly via processes that are coupled to the regulators of ER Ca2+ dynamics. In this review, we describe the mechanisms involved in the establishment of ER Ca2+ homeostasis in neurons. We elaborate upon how changes in the spatiotemporal dynamics of Ca2+ exchange between the ER and other organelles sculpt neuronal function and provide examples that demonstrate the involvement of ER Ca2+ dyshomeostasis in a range of neurological and neurodegenerative diseases.
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Ca 2+-independent but voltage-dependent quantal catecholamine secretion (CiVDS) in the mammalian sympathetic nervous system. Proc Natl Acad Sci U S A 2019; 116:20201-20209. [PMID: 31530723 DOI: 10.1073/pnas.1902444116] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Action potential-induced vesicular exocytosis is considered exclusively Ca2+ dependent in Katz's Ca2+ hypothesis on synaptic transmission. This long-standing concept gets an exception following the discovery of Ca2+-independent but voltage-dependent secretion (CiVDS) and its molecular mechanisms in dorsal root ganglion sensory neurons. However, whether CiVDS presents only in sensory cells remains elusive. Here, by combining multiple independent recordings, we report that [1] CiVDS robustly presents in the sympathetic nervous system, including sympathetic superior cervical ganglion neurons and slice adrenal chromaffin cells, [2] uses voltage sensors of Ca2+ channels (N-type and novel L-type), and [3] contributes to catecholamine release in both homeostatic and fight-or-flight like states; [4] CiVDS-mediated catecholamine release is faster than that of Ca2+-dependent secretion at the quantal level and [5] increases Ca2+ currents and contractility of cardiac myocytes. Together, CiVDS presents in the sympathetic nervous system with potential physiological functions, including cardiac muscle contractility.
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Rama S, Jensen TP, Rusakov DA. Glutamate Imaging Reveals Multiple Sites of Stochastic Release in the CA3 Giant Mossy Fiber Boutons. Front Cell Neurosci 2019; 13:243. [PMID: 31213985 PMCID: PMC6558140 DOI: 10.3389/fncel.2019.00243] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 05/16/2019] [Indexed: 11/17/2022] Open
Abstract
One of the most studied central synapses which have provided fundamental insights into cellular mechanisms of neural connectivity is the “giant” excitatory connection between hippocampal mossy fibers (MFs) and CA3 pyramidal cells. Its large presynaptic bouton features multiple release sites and is densely packed with thousands of synaptic vesicles, to sustain a highly facilitating “detonator” transmission. However, whether glutamate release sites at this synapse act independently, in a stochastic manner, or rather synchronously, remains poorly understood. This knowledge is critical for a better understanding of mechanisms underpinning presynaptic plasticity and postsynaptic signal integration rules. Here, we use the optical glutamate sensor SF-iGluSnFR and the intracellular Ca2+ indicator Cal-590 to monitor spike-evoked glutamate release and presynaptic calcium entry in MF boutons. Multiplexed imaging reveals that distinct sites in individual MF giant boutons release glutamate in a probabilistic fashion, also showing use-dependent short-term facilitation. The present approach provides novel insights into the basic mechanisms of neurotransmitter release at excitatory synapses.
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Affiliation(s)
- Sylvain Rama
- UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Thomas P Jensen
- UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Dmitri A Rusakov
- UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
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31
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Forsberg M, Seth H, Björefeldt A, Lyckenvik T, Andersson M, Wasling P, Zetterberg H, Hanse E. Ionized calcium in human cerebrospinal fluid and its influence on intrinsic and synaptic excitability of hippocampal pyramidal neurons in the rat. J Neurochem 2019; 149:452-470. [PMID: 30851210 DOI: 10.1111/jnc.14693] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 02/21/2019] [Accepted: 03/05/2019] [Indexed: 12/13/2022]
Abstract
It is well-known that the extracellular concentration of calcium affects neuronal excitability and synaptic transmission. Less is known about the physiological concentration of extracellular calcium in the brain. In electrophysiological brain slice experiments, the artificial cerebrospinal fluid traditionally contains relatively high concentrations of calcium (2-4 mM) to support synaptic transmission and suppress neuronal excitability. Using an ion-selective electrode, we determined the fraction of ionized calcium in healthy human cerebrospinal fluid to 1.0 mM of a total concentration of 1.2 mM (86%). Using patch-clamp and extracellular recordings in the CA1 region in acute slices of rat hippocampus, we then compared the effects of this physiological concentration of calcium with the commonly used 2 mM on neuronal excitability, synaptic transmission, and long-term potentiation (LTP) to examine the magnitude of changes in this range of extracellular calcium. Increasing the total extracellular calcium concentration from 1.2 to 2 mM decreased spontaneous action potential firing, induced a depolarization of the threshold, and increased the rate of both de- and repolarization of the action potential. Evoked synaptic transmission was approximately doubled, with a balanced effect between inhibition and excitation. In 1.2 mM calcium high-frequency stimulation did not result in any LTP, whereas a prominent LTP was observed at 2 or 4 mM calcium. Surprisingly, this inability to induce LTP persisted during blockade of GABAergic inhibition. In conclusion, an increase from the physiological 1.2 mM to 2 mM calcium in the artificial cerebrospinal fluid has striking effects on neuronal excitability, synaptic transmission, and the induction of LTP. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Read the Editorial Highlight for this article on page 435.
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Affiliation(s)
- My Forsberg
- Department of Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Henrik Seth
- Department of Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Andreas Björefeldt
- Department of Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Department of Neuroscience, Brown University, Providence, RI, USA
| | - Tim Lyckenvik
- Department of Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Mats Andersson
- Department of Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Pontus Wasling
- Department of Clinical Neuroscience, The Sahlgrenska Academy, University of Gothenburg, Mölndal, Sweden
| | - Henrik Zetterberg
- Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy, University of Gothenburg, Mölndal, Sweden.,Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden.,UCL Institute of Neurology, Queen Square, London, UK.,The Dementia Research Institute at UCL, London, UK
| | - Eric Hanse
- Department of Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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Jensen TP, Zheng K, Cole N, Marvin JS, Looger LL, Rusakov DA. Multiplex imaging relates quantal glutamate release to presynaptic Ca 2+ homeostasis at multiple synapses in situ. Nat Commun 2019; 10:1414. [PMID: 30926781 PMCID: PMC6441074 DOI: 10.1038/s41467-019-09216-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 02/25/2019] [Indexed: 12/17/2022] Open
Abstract
Information processing by brain circuits depends on Ca2+-dependent, stochastic release of the excitatory neurotransmitter glutamate. Whilst optical glutamate sensors have enabled detection of synaptic discharges, understanding presynaptic machinery requires simultaneous readout of glutamate release and nanomolar presynaptic Ca2+ in situ. Here, we find that the fluorescence lifetime of the red-shifted Ca2+ indicator Cal-590 is Ca2+-sensitive in the nanomolar range, and employ it in combination with green glutamate sensors to relate quantal neurotransmission to presynaptic Ca2+ kinetics. Multiplexed imaging of individual and multiple synapses in identified axonal circuits reveals that glutamate release efficacy, but not its short-term plasticity, varies with time-dependent fluctuations in presynaptic resting Ca2+ or spike-evoked Ca2+ entry. Within individual presynaptic boutons, we find no nanoscopic co-localisation of evoked presynaptic Ca2+ entry with the prevalent glutamate release site, suggesting loose coupling between the two. The approach enables a better understanding of release machinery at central synapses.
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Affiliation(s)
- Thomas P Jensen
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK.
| | - Kaiyu Zheng
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK
| | - Nicholas Cole
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK
| | - Jonathan S Marvin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, 20147, VA, USA
| | - Loren L Looger
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, 20147, VA, USA
| | - Dmitri A Rusakov
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK.
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33
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Davila S, Liu P, Smith A, Marshall AG, Pedigo S. Spontaneous Calcium-Independent Dimerization of the Isolated First Domain of Neural Cadherin. Biochemistry 2018; 57:6404-6415. [PMID: 30387993 DOI: 10.1021/acs.biochem.8b00733] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cadherins are calcium-dependent, transmembrane adhesion molecules that assemble through direct noncovalent association of their N-terminal extracellular modular domains. As the transmembrane component of adherens junctions, they indirectly link adherent cells' actin cytoskeletons. Here, we investigate the most distal extracellular domain of neural cadherin (N-cadherin), a protein required at excitatory synapses, the site of long-term potentiation. This domain is the site of the adhesive interface, and it forms a dimer spontaneously without binding calcium, a surprising finding given that calcium binding is required for proper physiological function. A critical tryptophan at position 2, W2, provides a spectroscopic probe for the "closed" monomer and strand-swapped dimer. Spectroscopic studies show that W2 remains docked in the two forms but has a different apparent interaction with the hydrophobic pocket. Size-exclusion chromatography was used to measure the levels of the monomer and dimer over time to study the kinetics and equilibria of the unexpected spontaneous dimer formation ( Kd = 130 μM; τ = 2 days at 4 °C). Our results support the idea that NCAD1 is missing critical contacts that facilitate the rapid exchange of the βA-strand. Furthermore, the monomer and dimer have equivalent and exceptionally high intrinsic stability for a 99-residue Ig-like domain with no internal disulfides ( Tm = 77 °C; Δ H = 85 kcal/mol). Ultimately, a complete analysis of synapse dynamics requires characterization of the kinetics and equilibria of N-cadherin. The studies reported here take a reductionist approach to understanding the essential biophysics of an atypical Ig-like domain that is the site of the adhesive interface of N-cadherin.
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Affiliation(s)
- Samantha Davila
- Department of Chemistry and Biochemistry , University of Mississippi , University , Mississippi 38677 , United States
| | - Peilu Liu
- Department of Chemistry & Biochemistry , Florida State University , Tallahassee , Florida 32306 , United States.,Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory , Florida State University , Tallahassee , Florida 32310 , United States
| | - Alexis Smith
- Department of Chemistry and Biochemistry , University of Mississippi , University , Mississippi 38677 , United States
| | - Alan G Marshall
- Department of Chemistry & Biochemistry , Florida State University , Tallahassee , Florida 32306 , United States.,Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory , Florida State University , Tallahassee , Florida 32310 , United States
| | - Susan Pedigo
- Department of Chemistry and Biochemistry , University of Mississippi , University , Mississippi 38677 , United States
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Roy N, Sanz-Leon P, Robinson PA. Spectrum of connectivity fluctuations including the effect of activity-dependent feedback. Phys Rev E 2018; 98:022319. [PMID: 30253627 DOI: 10.1103/physreve.98.022319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Indexed: 11/07/2022]
Abstract
The spatiotemporal spectrum of feedback-driven fluctuations of brain connectivity is investigated using nonlinear neural field theory of the corticothalamic system. Weakly nonlinear dynamics of neural feedbacks are expanded in terms of first order perturbations of neural activity relative to a fixed point. Susceptibilities are used to quantify the change in connectivity per unit change in presynaptic or postsynaptic activity caused by nonlinear feedbacks such as facilitation, depression, sensitization, potentiation, and the effects of discrete eigenmode structure are included for a spherical brain geometry. Spectral signatures such as resonances are identified that allow the presence of particular presynaptic and postsynaptic feedback effects to be inferred. These include additional resonances at high frequencies and shifts of existing spectral peaks, mostly visible in the lowest spatial modes of the response.
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Affiliation(s)
- N Roy
- School of Physics, University of Sydney, New South Wales 2006, Australia and Center for Integrative Brain Function, University of Sydney, New South Wales 2006, Australia
| | - P Sanz-Leon
- School of Physics, University of Sydney, New South Wales 2006, Australia and Center for Integrative Brain Function, University of Sydney, New South Wales 2006, Australia
| | - P A Robinson
- School of Physics, University of Sydney, New South Wales 2006, Australia and Center for Integrative Brain Function, University of Sydney, New South Wales 2006, Australia
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35
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Ultradian calcium rhythms in the paraventricular nucleus and subparaventricular zone in the hypothalamus. Proc Natl Acad Sci U S A 2018; 115:E9469-E9478. [PMID: 30228120 PMCID: PMC6176559 DOI: 10.1073/pnas.1804300115] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Despite that the various functions in mammals fluctuate in the ultradian fashion, the origin and mechanism of the rhythm are largely unknown. In this study, we found synchronous ultradian calcium rhythms in the hypothalamic paraventricular nucleus (PVN), subparaventricular zone (SPZ), and suprachiasmatic nucleus (SCN). The ultradian rhythms were originated from the SPZ-PVN region and transmitted to the SCN. Neurochemical interventions revealed that the glutamatergic mechanism is critical for generation and a tetrodotoxin-sensitive neural network for synchrony of the ultradian rhythm. The GABAergic system could have a role in refining the circadian output signals. The study provides the first clue to understand the loci and mechanism of ultradian rhythm in the hypothalamus. The suprachiasmatic nucleus (SCN), the master circadian clock in mammals, sends major output signals to the subparaventricular zone (SPZ) and further to the paraventricular nucleus (PVN), the neural mechanism of which is largely unknown. In this study, the intracellular calcium levels were measured continuously in cultured hypothalamic slices containing the PVN, SPZ, and SCN. We detected ultradian calcium rhythms in both the SPZ-PVN and SCN regions with periods of 0.5–4.0 hours, the frequency of which depended on the local circadian rhythm in the SPZ-PVN region. The ultradian rhythms were synchronous in the entire SPZ-PVN region and a part of the SCN. Because the ultradian rhythms were not detected in the SCN-only slice, the origin of ultradian rhythm is the SPZ-PVN region. In association with an ultradian bout, a rapid increase of intracellular calcium in a millisecond order was detected, the frequency of which determined the amplitude of an ultradian bout. The synchronous ultradian rhythms were desynchronized and depressed by a sodium channel blocker tetrodotoxin, suggesting that a tetrodotoxin-sensitive network is involved in synchrony of the ultradian bouts. In contrast, the ultradian rhythm is abolished by glutamate receptor blockers, indicating the critical role of glutamatergic mechanism in ultradian rhythm generation, while a GABAA receptor blocker increased the frequency of ultradian rhythm and modified the circadian rhythm in the SCN. A GABAergic network may refine the circadian output signals. The present study provides a clue to unraveling the loci and network mechanisms of the ultradian rhythm.
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36
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Gerbino A, Colella M. The Different Facets of Extracellular Calcium Sensors: Old and New Concepts in Calcium-Sensing Receptor Signalling and Pharmacology. Int J Mol Sci 2018; 19:E999. [PMID: 29584660 PMCID: PMC5979557 DOI: 10.3390/ijms19040999] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 03/23/2018] [Accepted: 03/25/2018] [Indexed: 12/14/2022] Open
Abstract
The current interest of the scientific community for research in the field of calcium sensing in general and on the calcium-sensing Receptor (CaR) in particular is demonstrated by the still increasing number of papers published on this topic. The extracellular calcium-sensing receptor is the best-known G-protein-coupled receptor (GPCR) able to sense external Ca2+ changes. Widely recognized as a fundamental player in systemic Ca2+ homeostasis, the CaR is ubiquitously expressed in the human body where it activates multiple signalling pathways. In this review, old and new notions regarding the mechanisms by which extracellular Ca2+ microdomains are created and the tools available to measure them are analyzed. After a survey of the main signalling pathways triggered by the CaR, a special attention is reserved for the emerging concepts regarding CaR function in the heart, CaR trafficking and pharmacology. Finally, an overview on other Ca2+ sensors is provided.
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Affiliation(s)
- Andrea Gerbino
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, 70121 Bari, Italy.
| | - Matilde Colella
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, 70121 Bari, Italy.
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37
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Bijata M, Labus J, Guseva D, Stawarski M, Butzlaff M, Dzwonek J, Schneeberg J, Böhm K, Michaluk P, Rusakov DA, Dityatev A, Wilczyński G, Wlodarczyk J, Ponimaskin E. Synaptic Remodeling Depends on Signaling between Serotonin Receptors and the Extracellular Matrix. Cell Rep 2018; 19:1767-1782. [PMID: 28564597 DOI: 10.1016/j.celrep.2017.05.023] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 04/03/2017] [Accepted: 05/04/2017] [Indexed: 02/04/2023] Open
Abstract
Rewiring of synaptic circuitry pertinent to memory formation has been associated with morphological changes in dendritic spines and with extracellular matrix (ECM) remodeling. Here, we mechanistically link these processes by uncovering a signaling pathway involving the serotonin 5-HT7 receptor (5-HT7R), matrix metalloproteinase 9 (MMP-9), the hyaluronan receptor CD44, and the small GTPase Cdc42. We highlight a physical interaction between 5-HT7R and CD44 (identified as an MMP-9 substrate in neurons) and find that 5-HT7R stimulation increases local MMP-9 activity, triggering dendritic spine remodeling, synaptic pruning, and impairment of long-term potentiation (LTP). The underlying molecular machinery involves 5-HT7R-mediated activation of MMP-9, which leads to CD44 cleavage followed by Cdc42 activation. One important physiological consequence of this interaction includes an increase in neuronal outgrowth and elongation of dendritic spines, which might have a positive effect on complex neuronal processes (e.g., reversal learning and neuronal regeneration).
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Affiliation(s)
- Monika Bijata
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology of the Polish Academy of Science, Pasteura 3, Warsaw 02-093, Poland
| | - Josephine Labus
- Cellular Neurophysiology, Center of Physiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Daria Guseva
- Cellular Neurophysiology, Center of Physiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Michał Stawarski
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology of the Polish Academy of Science, Pasteura 3, Warsaw 02-093, Poland
| | - Malte Butzlaff
- Cellular Neurophysiology, Center of Physiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Joanna Dzwonek
- Department of Neurophysiology, Nencki Institute of Experimental Biology of the Polish Academy of Science, Pasteura 3, Warsaw 02-093, Poland
| | - Jenny Schneeberg
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), Leipziger Str. 44, 39120 Magdeburg, Germany; Medical Faculty, Otto von Guericke University, Leipziger Str. 44, 39120 Magdeburg, Germany
| | - Katrin Böhm
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), Leipziger Str. 44, 39120 Magdeburg, Germany; Medical Faculty, Otto von Guericke University, Leipziger Str. 44, 39120 Magdeburg, Germany
| | - Piotr Michaluk
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology of the Polish Academy of Science, Pasteura 3, Warsaw 02-093, Poland; UCL Institute of Neurology, University College of London, Queen Square, London WC1N 3BG, UK
| | - Dmitri A Rusakov
- UCL Institute of Neurology, University College of London, Queen Square, London WC1N 3BG, UK
| | - Alexander Dityatev
- Molecular Neuroplasticity Group, German Center for Neurodegenerative Diseases (DZNE), Leipziger Str. 44, 39120 Magdeburg, Germany; Medical Faculty, Otto von Guericke University, Leipziger Str. 44, 39120 Magdeburg, Germany
| | - Grzegorz Wilczyński
- Department of Neurophysiology, Nencki Institute of Experimental Biology of the Polish Academy of Science, Pasteura 3, Warsaw 02-093, Poland
| | - Jakub Wlodarczyk
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology of the Polish Academy of Science, Pasteura 3, Warsaw 02-093, Poland.
| | - Evgeni Ponimaskin
- Cellular Neurophysiology, Center of Physiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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39
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 876] [Impact Index Per Article: 146.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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40
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Pinto BI, Pupo A, García IE, Mena-Ulecia K, Martínez AD, Latorre R, Gonzalez C. Calcium binding and voltage gating in Cx46 hemichannels. Sci Rep 2017; 7:15851. [PMID: 29158540 PMCID: PMC5696461 DOI: 10.1038/s41598-017-15975-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 10/24/2017] [Indexed: 12/26/2022] Open
Abstract
The opening of connexin (Cx) hemichannels in the membrane is tightly regulated by calcium (Ca2+) and membrane voltage. Electrophysiological and atomic force microscopy experiments indicate that Ca2+ stabilizes the hemichannel closed state. However, structural data show that Ca2+ binding induces an electrostatic seal preventing ion transport without significant structural rearrangements. In agreement with the closed-state stabilization hypothesis, we found that the apparent Ca2+ sensitivity is increased as the voltage is made more negative. Moreover, the voltage and Ca2+ dependence of the channel kinetics indicate that the voltage sensor movement and Ca2+ binding are allosterically coupled. An allosteric kinetic model in which the Ca2+ decreases the energy necessary to deactivate the voltage sensor reproduces the effects of Ca2+ and voltage in Cx46 hemichannels. In agreement with the model and suggesting a conformational change that narrows the pore, Ca2+ inhibits the water flux through Cx hemichannels. We conclude that Ca2+ and voltage act allosterically to stabilize the closed conformation of Cx46 hemichannels.
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Affiliation(s)
- Bernardo I Pinto
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Amaury Pupo
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Isaac E García
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- Facultad de Odontología, Universidad de Valparaíso, Valparaíso, Chile
| | - Karel Mena-Ulecia
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Ramón Latorre
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.
| | - Carlos Gonzalez
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.
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41
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Abstract
The emerging technological revolution in genetically encoded molecular sensors and super-resolution imaging provides neuroscientists with a pass to the real-time nano-world. On this small scale, however, classical principles of electrophysiology do not always apply. This is in large part because the nanoscopic heterogeneities in ionic concentrations and the local electric fields associated with individual ions and their movement can no longer be ignored. Here, we review basic principles of molecular electrodiffusion in the cellular environment of organized brain tissue. We argue that accurate interpretation of physiological observations on the nanoscale requires a better understanding of the underlying electrodiffusion phenomena.
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42
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Nicholson C, Hrabětová S. Brain Extracellular Space: The Final Frontier of Neuroscience. Biophys J 2017; 113:2133-2142. [PMID: 28755756 DOI: 10.1016/j.bpj.2017.06.052] [Citation(s) in RCA: 169] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 05/31/2017] [Accepted: 06/07/2017] [Indexed: 01/15/2023] Open
Abstract
Brain extracellular space is the narrow microenvironment that surrounds every cell of the central nervous system. It contains a solution that closely resembles cerebrospinal fluid with the addition of extracellular matrix molecules. The space provides a reservoir for ions essential to the electrical activity of neurons and forms an intercellular chemical communication channel. Attempts to reveal the size and structure of the extracellular space using electron microscopy have had limited success; however, a biophysical approach based on diffusion of selected probe molecules has proved useful. A point-source paradigm, realized in the real-time iontophoresis method using tetramethylammonium, as well as earlier radiotracer methods, have shown that the extracellular space occupies ∼20% of brain tissue and small molecules have an effective diffusion coefficient that is two-fifths that in a free solution. Monte Carlo modeling indicates that geometrical constraints, including dead-space microdomains, contribute to the hindrance to diffusion. Imaging the spread of macromolecules shows them increasingly hindered as a function of size and suggests that the gaps between cells are predominantly ∼40 nm with wider local expansions that may represent dead-spaces. Diffusion measurements also characterize interactions of ions and proteins with the chondroitin and heparan sulfate components of the extracellular matrix; however, the many roles of the matrix are only starting to become apparent. The existence and magnitude of bulk flow and the so-called glymphatic system are topics of current interest and controversy. The extracellular space is an exciting area for research that will be propelled by emerging technologies.
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Affiliation(s)
- Charles Nicholson
- Department of Neuroscience and Physiology, New York University School of Medicine, New York, New York; Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York.
| | - Sabina Hrabětová
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York; The Robert Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, New York
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43
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Tanis JE, Ma Z, Foskett JK. The NH 2 terminus regulates voltage-dependent gating of CALHM ion channels. Am J Physiol Cell Physiol 2017; 313:C173-C186. [PMID: 28515089 DOI: 10.1152/ajpcell.00318.2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 04/26/2017] [Accepted: 05/03/2017] [Indexed: 12/15/2022]
Abstract
Calcium homeostasis modulator protein-1 (CALHM1) and its Caenorhabditis elegans (ce) homolog, CLHM-1, belong to a new family of physiologically important ion channels that are regulated by voltage and extracellular Ca2+ (Ca2+o) but lack a canonical voltage-sensing domain. Consequently, the intrinsic voltage-dependent gating mechanisms for CALHM channels are unknown. Here, we performed voltage-clamp experiments on ceCLHM-1 chimeric, deletion, insertion, and point mutants to assess the role of the NH2 terminus (NT) in CALHM channel gating. Analyses of chimeric channels in which the ceCLHM-1 and human (h)CALHM1 NH2 termini were interchanged showed that the hCALHM1 NT destabilized channel-closed states, whereas the ceCLHM-1 NT had a stabilizing effect. In the absence of Ca2+o, deletion of up to eight amino acids from the ceCLHM-1 NT caused a hyperpolarizing shift in the conductance-voltage relationship with little effect on voltage-dependent slope. However, deletion of nine or more amino acids decreased voltage dependence and induced a residual conductance at hyperpolarized voltages. Insertion of amino acids into the NH2-terminal helix also decreased voltage dependence but did not prevent channel closure. Mutation of ceCLHM-1 valine 9 and glutamine 13 altered half-maximal activation and voltage dependence, respectively, in 0 Ca2+ In 2 mM Ca2+o, ceCLHM-1 NH2-terminal deletion and point mutant channels closed completely at hyperpolarized voltages with apparent affinity for Ca2+o indistinguishable from wild-type ceCLHM-1, although the ceCLHM-1 valine 9 mutant exhibited an altered conductance-voltage relationship and kinetics. We conclude that the NT plays critical roles modulating voltage dependence and stabilizing the closed states of CALHM channels.
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Affiliation(s)
- Jessica E Tanis
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; and
| | - Zhongming Ma
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; and
| | - J Kevin Foskett
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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44
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Jensen TP, Zheng K, Tyurikova O, Reynolds JP, Rusakov DA. Monitoring single-synapse glutamate release and presynaptic calcium concentration in organised brain tissue. Cell Calcium 2017; 64:102-108. [PMID: 28465084 DOI: 10.1016/j.ceca.2017.03.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Brain function relies in large part on Ca2+-dependent release of the excitatory neurotransmitter glutamate from neuronal axons. Establishing the causal relationship between presynaptic Ca2+ dynamics and probabilistic glutamate release is therefore a fundamental quest across neurosciences. Its progress, however, has hitherto depended primarily on the exploration of either cultured nerve cells or giant central synapses accessible to direct experimental probing in situ. Here we show that combining patch-clamp with time-resolved imaging of Ca2+ -sensitive fluorescence lifetime of Oregon Green BAPTA-1 (Tornado-FLIM) enables readout of single spike-evoked presynaptic Ca2+ concentration dynamics, with nanomolar sensitivity, in individual neuronal axons in acute brain slices. In parallel, intensity Tornado imaging of a locally expressed extracellular optical glutamate sensor iGluSnFr provides direct monitoring of single-quantum, single-synapse glutamate releases in situ. These two methods pave the way for simultaneous registration of presynaptic Ca2+ dynamics and transmitter release in an intact brain at the level of individual synapses.
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Affiliation(s)
- Thomas P Jensen
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
| | - Kaiyu Zheng
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - Olga Tyurikova
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK; Institute of Neuroscience, University of Nizhny Novgorod, 603950 Nizhny Novgorod, Russia
| | - James P Reynolds
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - Dmitri A Rusakov
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
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45
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Nanoscale diffusion in the synaptic cleft and beyond measured with time-resolved fluorescence anisotropy imaging. Sci Rep 2017; 7:42022. [PMID: 28181535 PMCID: PMC5299514 DOI: 10.1038/srep42022] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 01/05/2017] [Indexed: 12/11/2022] Open
Abstract
Neural activity relies on molecular diffusion within nanoscopic spaces outside and inside nerve cells, such as synaptic clefts or dendritic spines. Measuring diffusion on this small scale in situ has not hitherto been possible, yet this knowledge is critical for understanding the dynamics of molecular events and electric currents that shape physiological signals throughout the brain. Here we advance time-resolved fluorescence anisotropy imaging combined with two-photon excitation microscopy to map nanoscale diffusivity in ex vivo brain slices. We find that in the brain interstitial gaps small molecules move on average ~30% slower than in a free medium whereas inside neuronal dendrites this retardation is ~70%. In the synaptic cleft free nanodiffusion is decelerated by ~46%. These quantities provide previously unattainable basic constrains for the receptor actions of released neurotransmitters, the electrical conductance of the brain interstitial space and the limiting rate of molecular interactions or conformational changes in the synaptic microenvironment.
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46
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Wang Y, Kang Y, Ma C, Miao R, Wu C, Long Y, Ge T, Wu Z, Hou X, Zhang J, Qi Z. CNGC2 Is a Ca2+ Influx Channel That Prevents Accumulation of Apoplastic Ca2+ in the Leaf. PLANT PHYSIOLOGY 2017; 173:1342-1354. [PMID: 27999084 PMCID: PMC5291024 DOI: 10.1104/pp.16.01222] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 12/16/2016] [Indexed: 05/18/2023]
Abstract
Ca2+ is absorbed by roots and transported upward through the xylem to the apoplastic space of the leaf, after which it is deposited into the leaf cell. In Arabidopsis (Arabidopsis thaliana), the tonoplast-localized Ca2+/H+ transporters CATION EXCHANGER1 (CAX1) and CAX3 sequester Ca2+ from the cytosol into the vacuole, but it is not known what transporter mediates the initial Ca2+ influx from the apoplast to the cytosol. Here, we report that Arabidopsis CYCLIC NUCLEOTIDE-GATED CHANNEL2 (CNGC2) encodes a protein with Ca2+ influx channel activity and is expressed in the leaf areas surrounding the free endings of minor veins, which is the primary site for Ca2+ unloading from the vasculature and influx into leaf cells. Under hydroponic growth conditions, with 0.1 mm Ca2+, both Arabidopsis cngc2 and cax1cax3 loss-of-function mutants grew normally. Increasing the Ca2+ concentration to 10 mm induced H2O2 accumulation, cell death, and leaf senescence and partially suppressed the hypersensitive response to avirulent pathogens in the mutants but not in the wild type. In vivo apoplastic Ca2+ overaccumulation was found in the leaves of cngc2 and cax1cax3 but not the wild type under the 10 mm Ca2+ condition, as monitored by Oregon Green BAPTA 488 5N, a low-affinity and membrane-impermeable Ca2+ probe. Our results indicate that CNGC2 likely has no direct roles in leaf development or the hypersensitive response but, instead, that CNGC2 could mediate Ca2+ influx into leaf cells. Finally, the in vivo extracellular Ca2+ imaging method developed in this study provides a new tool for investigating Ca2+ dynamics in plant cells.
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Affiliation(s)
- Yan Wang
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
| | - Yan Kang
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
| | - Chunli Ma
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
| | - Ruiying Miao
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
| | - Caili Wu
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
| | - Yu Long
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
| | - Ting Ge
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
| | - Zinian Wu
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
| | - Xiangyang Hou
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
| | - Junxia Zhang
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
| | - Zhi Qi
- Inner Mongolia University, School of Life Sciences, Hohhot 010021, People's Republic of China (Y.W., Y.K., C.M., R.M., C.W., Y.L., T.G., J.Z., Z.Q.); and
- Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Hohhot 010010, People's Republic of China (Z.W., X.H.)
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47
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Dynamic Control of Synaptic Adhesion and Organizing Molecules in Synaptic Plasticity. Neural Plast 2017; 2017:6526151. [PMID: 28255461 PMCID: PMC5307005 DOI: 10.1155/2017/6526151] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 12/13/2016] [Indexed: 12/13/2022] Open
Abstract
Synapses play a critical role in establishing and maintaining neural circuits, permitting targeted information transfer throughout the brain. A large portfolio of synaptic adhesion/organizing molecules (SAMs) exists in the mammalian brain involved in synapse development and maintenance. SAMs bind protein partners, forming trans-complexes spanning the synaptic cleft or cis-complexes attached to the same synaptic membrane. SAMs play key roles in cell adhesion and in organizing protein interaction networks; they can also provide mechanisms of recognition, generate scaffolds onto which partners can dock, and likely take part in signaling processes as well. SAMs are regulated through a portfolio of different mechanisms that affect their protein levels, precise localization, stability, and the availability of their partners at synapses. Interaction of SAMs with their partners can further be strengthened or weakened through alternative splicing, competing protein partners, ectodomain shedding, or astrocytically secreted factors. Given that numerous SAMs appear altered by synaptic activity, in vivo, these molecules may be used to dynamically scale up or scale down synaptic communication. Many SAMs, including neurexins, neuroligins, cadherins, and contactins, are now implicated in neuropsychiatric and neurodevelopmental diseases, such as autism spectrum disorder, schizophrenia, and bipolar disorder and studying their molecular mechanisms holds promise for developing novel therapeutics.
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48
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Tu YC, Yang YC, Kuo CC. Modulation of NMDA channel gating by Ca 2+ and Cd 2+ binding to the external pore mouth. Sci Rep 2016; 6:37029. [PMID: 27848984 PMCID: PMC5111045 DOI: 10.1038/srep37029] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 10/24/2016] [Indexed: 01/14/2023] Open
Abstract
NMDA receptor channels are characterized by high Ca2+ permeability. It remains unclear whether extracellular Ca2+ could directly modulate channel gating and control Ca2+ influxes. We demonstrate a pore-blocking site external to the activation gate for extracellular Ca2+ and Cd2+, which has the same charge and radius as Ca2+ but is impermeable to the channel. The apparent affinity of Cd2+ or Ca2+ is higher toward the activated (a steady-state mixture of the open and desensitized, probably chiefly the latter) than the closed states. The blocking effect of Cd2+ is well correlated with the number of charges in the DRPEER motif at the external pore mouth, with coupling coefficients close to 1 in double mutant cycle analyses. The effect of Ca2+ and especially Cd2+ could be allosterically affected by T647A mutation located just inside the activation gate. A prominent "hook" also develops after wash-off of Cd2+ or Ca2+, suggesting faster unbinding rates of Cd2+ and Ca2+ with the mutation. We conclude that extracellular Ca2+ or Cd2+ directly binds to the DRPEER motif to modify NMDA channel activation (opening as well as desensitization), which seems to involve essential regional conformational changes centered at the bundle crossing point A652 (GluN1)/A651(GluN2).
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Affiliation(s)
- Ya-Chi Tu
- Department of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Ya-Chin Yang
- Department of Biomedical Sciences,College of Medicine, Chang Gung University, Tao-Yuan, Taiwan.,Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan.,Neuroscience Research Center, Chang Gung Memorial Hospital, Linkou Medical Center, Tao-Yuan, Taiwan
| | - Chung-Chin Kuo
- Department of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan.,Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan
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Colella M, Gerbino A, Hofer AM, Curci S. Recent advances in understanding the extracellular calcium-sensing receptor. F1000Res 2016; 5. [PMID: 27803801 PMCID: PMC5074356 DOI: 10.12688/f1000research.8963.1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/13/2016] [Indexed: 12/11/2022] Open
Abstract
The extracellular calcium-sensing receptor (CaR), a ubiquitous class C G-protein-coupled receptor (GPCR), is responsible for the control of calcium homeostasis in body fluids. It integrates information about external Ca
2+ and a surfeit of other endogenous ligands into multiple intracellular signals, but how is this achieved? This review will focus on some of the exciting concepts in CaR signaling and pharmacology that have emerged in the last few years.
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Affiliation(s)
- Matilde Colella
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari , Bari, Italy
| | - Andrea Gerbino
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari , Bari, Italy
| | - Aldebaran M Hofer
- Department of Surgery, Brigham & Women's Hospital, Harvard Medical School and VA Boston Healthcare System, West Roxbury, MA, USA
| | - Silvana Curci
- Department of Surgery, Brigham & Women's Hospital, Harvard Medical School and VA Boston Healthcare System, West Roxbury, MA, USA
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Sui B, Liu X, Wang M, Belfield KD. A Highly Selective Fluorescence Turn-On Sensor for Extracellular Calcium Ion Detection. Chemistry 2016; 22:10351-4. [PMID: 27247191 DOI: 10.1002/chem.201602162] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Indexed: 11/08/2022]
Abstract
A highly water-soluble, fluorescence turn-on sensor for Ca(2+) is reported. The sensor affords high selectivity in sensing Ca(2+) over other biologically important metal cations. The dissociation constant of the sensor in binding Ca(2+) is 0.92 mm. Fluorescence microscopy experiments demonstrate that the sensor is cell-impermeable and capable of detecting extracellular Ca(2+) .
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Affiliation(s)
- Binglin Sui
- College of Science and Liberal Arts, New Jersey Institute of Technology, Newark, New Jersey, 07102, United States
| | - Xinglei Liu
- College of Science and Liberal Arts, New Jersey Institute of Technology, Newark, New Jersey, 07102, United States
| | - Mengyuan Wang
- Department of Chemistry, University of Central Florida, Orlando, Florida, 32816, United States
| | - Kevin D Belfield
- College of Science and Liberal Arts, New Jersey Institute of Technology, Newark, New Jersey, 07102, United States.
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