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Abstract
A central theme in the quest to unravel the genetic basis of epilepsy has been the effort to elucidate the roles played by inherited defects in ion channels. The ubiquitous expression of voltage-gated calcium channels (VGCCs) throughout the central nervous system (CNS), along with their involvement in fundamental processes, such as neuronal excitability and synaptic transmission, has made them attractive candidates. Recent insights provided by the identification of mutations in the P/Q-type calcium channel in humans and rodents with epilepsy and the finding of thalamic T-type calcium channel dysfunction in the absence of seizures have raised expectations of a causal role of calcium channels in the polygenic inheritance of idiopathic epilepsy. In this review, we consider how genetic variation in neuronal VGCCs may influence the development of epilepsy.
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Affiliation(s)
- Sanjeev Rajakulendran
- UCL-Institute of Neurology, MRC Centre for Neuromuscular Diseases, Queen Square, London WC1N 3BG, United Kingdom
| | - Michael G Hanna
- UCL-Institute of Neurology, MRC Centre for Neuromuscular Diseases, Queen Square, London WC1N 3BG, United Kingdom
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52
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Ca-α1T, a fly T-type Ca2+ channel, negatively modulates sleep. Sci Rep 2015; 5:17893. [PMID: 26647714 PMCID: PMC4673464 DOI: 10.1038/srep17893] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 11/06/2015] [Indexed: 01/14/2023] Open
Abstract
Mammalian T-type Ca2+ channels are encoded by three separate genes (Cav3.1, 3.2, 3.3). These channels are reported to be sleep stabilizers important in the generation of the delta rhythms of deep sleep, but controversy remains. The identification of precise physiological functions for the T-type channels has been hindered, at least in part, by the potential for compensation between the products of these three genes and a lack of specific pharmacological inhibitors. Invertebrates have only one T-type channel gene, but its functions are even less well-studied. We cloned Ca-α1T, the only Cav3 channel gene in Drosophila melanogaster, expressed it in Xenopus oocytes and HEK-293 cells, and confirmed it passes typical T-type currents. Voltage-clamp analysis revealed the biophysical properties of Ca-α1T show mixed similarity, sometimes falling closer to Cav3.1, sometimes to Cav3.2, and sometimes to Cav3.3. We found Ca-α1T is broadly expressed across the adult fly brain in a pattern vaguely reminiscent of mammalian T-type channels. In addition, flies lacking Ca-α1T show an abnormal increase in sleep duration most pronounced during subjective day under continuous dark conditions despite normal oscillations of the circadian clock. Thus, our study suggests invertebrate T-type Ca2+ channels promote wakefulness rather than stabilizing sleep.
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Coutelier M, Blesneac I, Monteil A, Monin ML, Ando K, Mundwiller E, Brusco A, Le Ber I, Anheim M, Castrioto A, Duyckaerts C, Brice A, Durr A, Lory P, Stevanin G. A Recurrent Mutation in CACNA1G Alters Cav3.1 T-Type Calcium-Channel Conduction and Causes Autosomal-Dominant Cerebellar Ataxia. Am J Hum Genet 2015; 97:726-37. [PMID: 26456284 DOI: 10.1016/j.ajhg.2015.09.007] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 09/18/2015] [Indexed: 12/20/2022] Open
Abstract
Hereditary cerebellar ataxias (CAs) are neurodegenerative disorders clinically characterized by a cerebellar syndrome, often accompanied by other neurological or non-neurological signs. All transmission modes have been described. In autosomal-dominant CA (ADCA), mutations in more than 30 genes are implicated, but the molecular diagnosis remains unknown in about 40% of cases. Implication of ion channels has long been an ongoing topic in the genetics of CA, and mutations in several channel genes have been recently connected to ADCA. In a large family affected by ADCA and mild pyramidal signs, we searched for the causative variant by combining linkage analysis and whole-exome sequencing. In CACNA1G, we identified a c.5144G>A mutation, causing an arginine-to-histidine (p.Arg1715His) change in the voltage sensor S4 segment of the T-type channel protein Cav3.1. Two out of 479 index subjects screened subsequently harbored the same mutation. We performed electrophysiological experiments in HEK293T cells to compare the properties of the p.Arg1715His and wild-type Cav3.1 channels. The current-voltage and the steady-state activation curves of the p.Arg1715His channel were shifted positively, whereas the inactivation curve had a higher slope factor. Computer modeling in deep cerebellar nuclei (DCN) neurons suggested that the mutation results in decreased neuronal excitability. Taken together, these data establish CACNA1G, which is highly expressed in the cerebellum, as a gene whose mutations can cause ADCA. This is consistent with the neuropathological examination, which showed severe Purkinje cell loss. Our study further extends our knowledge of the link between calcium channelopathies and CAs.
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54
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Phosphorylation of the Cav3.2 T-type calcium channel directly regulates its gating properties. Proc Natl Acad Sci U S A 2015; 112:13705-10. [PMID: 26483470 DOI: 10.1073/pnas.1511740112] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Phosphorylation is a major mechanism regulating the activity of ion channels that remains poorly understood with respect to T-type calcium channels (Cav3). These channels are low voltage-activated calcium channels that play a key role in cellular excitability and various physiological functions. Their dysfunction has been linked to several neurological disorders, including absence epilepsy and neuropathic pain. Recent studies have revealed that T-type channels are modulated by a variety of serine/threonine protein kinase pathways, which indicates the need for a systematic analysis of T-type channel phosphorylation. Here, we immunopurified Cav3.2 channels from rat brain, and we used high-resolution MS to construct the first, to our knowledge, in vivo phosphorylation map of a voltage-gated calcium channel in a mammalian brain. We identified as many as 34 phosphorylation sites, and we show that the vast majority of these sites are also phosphorylated on the human Cav3.2 expressed in HEK293T cells. In patch-clamp studies, treatment of the channel with alkaline phosphatase as well as analysis of dephosphomimetic mutants revealed that phosphorylation regulates important functional properties of Cav3.2 channels, including voltage-dependent activation and inactivation and kinetics. We also identified that the phosphorylation of a locus situated in the loop I-II S442/S445/T446 is crucial for this regulation. Our data show that Cav3.2 channels are highly phosphorylated in the mammalian brain and establish phosphorylation as an important mechanism involved in the dynamic regulation of Cav3.2 channel gating properties.
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55
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Monteil A, Chausson P, Boutourlinsky K, Mezghrani A, Huc-Brandt S, Blesneac I, Bidaud I, Lemmers C, Leresche N, Lambert RC, Lory P. Inhibition of Cav3.2 T-type Calcium Channels by Its Intracellular I-II Loop. J Biol Chem 2015; 290:16168-76. [PMID: 25931121 DOI: 10.1074/jbc.m114.634261] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Indexed: 11/06/2022] Open
Abstract
Voltage-dependent calcium channels (Cav) of the T-type family (Cav3.1, Cav3.2, and Cav3.3) are activated by low threshold membrane depolarization and contribute greatly to neuronal network excitability. Enhanced T-type channel activity, especially Cav3.2, contributes to disease states, including absence epilepsy. Interestingly, the intracellular loop connecting domains I and II (I-II loop) of Cav3.2 channels is implicated in the control of both surface expression and channel gating, indicating that this I-II loop plays an important regulatory role in T-type current. Here we describe that co-expression of this I-II loop or its proximal region (Δ1-Cav3.2; Ser(423)-Pro(542)) together with recombinant full-length Cav3.2 channel inhibited T-type current without affecting channel expression and membrane incorporation. Similar T-type current inhibition was obtained in NG 108-15 neuroblastoma cells that constitutively express Cav3.2 channels. Of interest, Δ1-Cav3.2 inhibited both Cav3.2 and Cav3.1 but not Cav3.3 currents. Efficacy of Δ1-Cav3.2 to inhibit native T-type channels was assessed in thalamic neurons using viral transduction. We describe that T-type current was significantly inhibited in the ventrobasal neurons that express Cav3.1, whereas in nucleus reticularis thalami neurons that express Cav3.2 and Cav3.3 channels, only the fast inactivating T-type current (Cav3.2 component) was significantly inhibited. Altogether, these data describe a new strategy to differentially inhibit Cav3 isoforms of the T-type calcium channels.
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Affiliation(s)
- Arnaud Monteil
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, Plateforme de Vectorologie, Biocampus Montpellier CNRS UMS 3426, INSERM US009, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Patrick Chausson
- Sorbonne Universités, Université Pierre et Marie Curie Université Paris 06, UM 119, Neuroscience Paris Seine (NPS), Paris F-75005, France, CNRS UMR 8246, NPS, Paris F-75005, France, and INSERM, U1130, NPS, Paris F-75005, France
| | - Katia Boutourlinsky
- Sorbonne Universités, Université Pierre et Marie Curie Université Paris 06, UM 119, Neuroscience Paris Seine (NPS), Paris F-75005, France, CNRS UMR 8246, NPS, Paris F-75005, France, and INSERM, U1130, NPS, Paris F-75005, France
| | - Alexandre Mezghrani
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Sylvaine Huc-Brandt
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Iulia Blesneac
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Isabelle Bidaud
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Céline Lemmers
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, Plateforme de Vectorologie, Biocampus Montpellier CNRS UMS 3426, INSERM US009, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Nathalie Leresche
- Sorbonne Universités, Université Pierre et Marie Curie Université Paris 06, UM 119, Neuroscience Paris Seine (NPS), Paris F-75005, France, CNRS UMR 8246, NPS, Paris F-75005, France, and INSERM, U1130, NPS, Paris F-75005, France
| | - Régis C Lambert
- Sorbonne Universités, Université Pierre et Marie Curie Université Paris 06, UM 119, Neuroscience Paris Seine (NPS), Paris F-75005, France, CNRS UMR 8246, NPS, Paris F-75005, France, and INSERM, U1130, NPS, Paris F-75005, France
| | - Philippe Lory
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France,
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56
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Reynders A, Mantilleri A, Malapert P, Rialle S, Nidelet S, Laffray S, Beurrier C, Bourinet E, Moqrich A. Transcriptional Profiling of Cutaneous MRGPRD Free Nerve Endings and C-LTMRs. Cell Rep 2015; 10:1007-1019. [PMID: 25683706 PMCID: PMC4542317 DOI: 10.1016/j.celrep.2015.01.022] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 12/13/2014] [Accepted: 01/08/2015] [Indexed: 01/06/2023] Open
Abstract
Cutaneous C-unmyelinated MRGPRD+ free nerve endings and C-LTMRs innervating hair follicles convey two opposite aspects of touch sensation: a sensation of pain and a sensation of pleasant touch. The molecular mechanisms underlying these diametrically opposite functions are unknown. Here, we used a mouse model that genetically marks C-LTMRs and MRGPRD+ neurons in combination with fluorescent cell surface labeling, flow cytometry, and RNA deep-sequencing technology (RNA-seq). Cluster analysis of RNA-seq profiles of the purified neuronal subsets revealed 486 and 549 genes differentially expressed in MRGPRD-expressing neurons and C-LTMRs, respectively. We validated 48 MRGPD- and 68 C-LTMRs-enriched genes using a triple-staining approach, and the Cav3.3 channel, found to be exclusively expressed in C-LTMRs, was validated using electrophysiology. Our study greatly expands the molecular characterization of C-LTMRs and suggests that this particular population of neurons shares some molecular features with Aβ and Aδ low-threshold mechanoreceptors.
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Affiliation(s)
- Ana Reynders
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, Case 907, 13288 Marseille Cedex 09, France
| | - Annabelle Mantilleri
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, Case 907, 13288 Marseille Cedex 09, France
| | - Pascale Malapert
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, Case 907, 13288 Marseille Cedex 09, France
| | - Stéphanie Rialle
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, UMR 5203, CNRS, U1191, INSERM, Université de Montpellier, 141 Rue de la Cardonille, 34094 Montpellier Cedex 05, France
| | - Sabine Nidelet
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, UMR 5203, CNRS, U1191, INSERM, Université de Montpellier, 141 Rue de la Cardonille, 34094 Montpellier Cedex 05, France
| | - Sophie Laffray
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, UMR 5203, CNRS, U1191, INSERM, Université de Montpellier, 141 Rue de la Cardonille, 34094 Montpellier Cedex 05, France
| | - Corinne Beurrier
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, Case 907, 13288 Marseille Cedex 09, France
| | - Emmanuel Bourinet
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, UMR 5203, CNRS, U1191, INSERM, Université de Montpellier, 141 Rue de la Cardonille, 34094 Montpellier Cedex 05, France.
| | - Aziz Moqrich
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, Case 907, 13288 Marseille Cedex 09, France.
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57
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Powell KL, Cain SM, Snutch TP, O'Brien TJ. Low threshold T-type calcium channels as targets for novel epilepsy treatments. Br J Clin Pharmacol 2015; 77:729-39. [PMID: 23834404 DOI: 10.1111/bcp.12205] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 07/02/2013] [Indexed: 12/21/2022] Open
Abstract
Low voltage-activated T-type calcium channels were originally cloned in the 1990s and much research has since focused on identifying the physiological roles of these channels in health and disease states. T-type calcium channels are expressed widely throughout the brain and peripheral tissues, and thus have been proposed as therapeutic targets for a variety of diseases such as epilepsy, insomnia, pain, cancer and hypertension. This review discusses the literature concerning the role of T-type calcium channels in physiological and pathological processes related to epilepsy. T-type calcium channels have been implicated in pathology of both the genetic and acquired epilepsies and several anti-epileptic drugs (AEDs) in clinical use are known to suppress seizures via inhibition of T-type calcium channels. Despite the fact that more than 15 new AEDs have become clinically available over the past 20 years at least 30% of epilepsy patients still fail to achieve seizure control, and many patients experience unwanted side effects. Furthermore there are no treatments that prevent the development of epilepsy or mitigate the epileptic state once established. Therefore there is an urgent need for the development of new AEDs that are effective in patients with drug resistant epilepsy, are anti-epileptogenic and are better tolerated. We also review the mechanisms of action of the current AEDs with known effects on T-type calcium channels and discuss novel compounds that are being investigated as new treatments for epilepsy.
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Affiliation(s)
- Kim L Powell
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Melbourne, Victoria, Australia
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58
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Perissinotti PP, Ethington EA, Almazan E, Martínez-Hernández E, Kalil J, Koob MD, Piedras-Rentería ES. Calcium current homeostasis and synaptic deficits in hippocampal neurons from Kelch-like 1 knockout mice. Front Cell Neurosci 2015; 8:444. [PMID: 25610372 PMCID: PMC4285801 DOI: 10.3389/fncel.2014.00444] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 12/10/2014] [Indexed: 11/30/2022] Open
Abstract
Kelch-like 1 (KLHL1) is a neuronal actin-binding protein that modulates voltage-gated CaV2.1 (P/Q-type) and CaV3.2 (α1H T-type) calcium channels; KLHL1 knockdown experiments (KD) cause down-regulation of both channel types and altered synaptic properties in cultured rat hippocampal neurons (Perissinotti et al., 2014). Here, we studied the effect of ablation of KLHL1 on calcium channel function and synaptic properties in cultured hippocampal neurons from KLHL1 knockout (KO) mice. Western blot data showed the P/Q-type channel α1A subunit was less abundant in KO hippocampus compared to wildtype (WT); and P/Q-type calcium currents were smaller in KO neurons than WT during early days in vitro, although this decrease was compensated for at late stages by increases in L-type calcium current. In contrast, T-type currents did not change in culture. However, biophysical properties and western blot analysis revealed a differential contribution of T-type channel isoforms in the KO, with CaV3.2 α1H subunit being down-regulated and CaV3.1 α1G up-regulated. Synapsin I levels were also reduced in the KO hippocampus and cultured neurons displayed a concomitant reduction in synapsin I puncta and decreased miniature excitatory postsynaptic current (mEPSC) frequency. In summary, genetic ablation of the calcium channel modulator resulted in compensatory mechanisms to maintain calcium current homeostasis in hippocampal KO neurons; however, synaptic alterations resulted in a reduction of excitatory synapse number, causing an imbalance of the excitatory-inhibitory synaptic input ratio favoring inhibition.
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Affiliation(s)
- Paula P Perissinotti
- Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine Maywood, IL, USA
| | - Elizabeth A Ethington
- Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine Maywood, IL, USA
| | - Erik Almazan
- Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine Maywood, IL, USA
| | - Elizabeth Martínez-Hernández
- Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine Maywood, IL, USA
| | - Jennifer Kalil
- Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine Maywood, IL, USA
| | - Michael D Koob
- Department of Laboratory Medicine and Pathology, Institute for Translational Neuroscience, University of Minnesota Minneapolis, MN, USA
| | - Erika S Piedras-Rentería
- Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine Maywood, IL, USA ; Neuroscience Institute, Loyola University Chicago, Stritch School of Medicine Maywood, IL, USA
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59
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Zhang L, Wang L, Jiang J, Zheng D, Liu S, Liu C. Lipopolysaccharides upregulate calcium concentration in mouse uterine smooth muscle cells through the T-type calcium channels. Int J Mol Med 2014; 35:784-90. [PMID: 25573237 DOI: 10.3892/ijmm.2014.2054] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 12/08/2014] [Indexed: 11/06/2022] Open
Abstract
Infection is a significant cause of preterm birth. Abnormal changes in intracellular calcium signals are the ultimate triggers of early uterine contractions that result in preterm birth. T‑type calcium channels play an important role in the pathogenesis of cancer, as well as endocrine and cardiovascular diseases. However, there are limited studies on their role in uterine contractions and parturition. In the present study, mouse uterine smooth muscle cells were isolated and treated with lipopolysaccharides (LPS) to mimic the microenvironment of uterine infection in vitro to investigate the role of T‑type calcium channels in the process of infection‑induced preterm birth. The results from quantitative polymerase chain reaction and western blot analysis showed that LPS significantly induced the expression of the Cav3.1 and Cav3.2 subtypes of T‑type calcium channels. Measurements of intracellular calcium concentration showed a significant increase in response to LPS. However, these effects can be reversed by T‑type calcium channel blockers. Western blot analysis further indicated that LPS induced the activation of the nuclear factor (NF)‑κB signaling pathway, and endothelin‑1 (ET‑1) was significantly upregulated, whereas NF‑κB inhibitors significantly inhibited the LPS‑induced upregulation of Cav3.1, Cav3.2 and ET‑1 expression. In addition, ET‑1 directly induced Cav3.1 and Cav3.2 expression, whereas ET‑1 antagonists inhibited the LPS‑induced upregulation of Cav3.1 and Cav3.2 expression. In conclusion, the present study demonstrates that infection triggers the upregulation of T‑type calcium channels and promotes calcium influx. This process relies on the activation of the NF‑κB/ET‑1 signaling pathway. The T‑type calcium channel is expected to become an effective target for the prevention of infection‑induced preterm birth.
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Affiliation(s)
- Lijuan Zhang
- Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang 110004, P.R. China
| | - Lin Wang
- Department of Emergency Medicine, Shengjing Hospital of China Medical University, Shenyang 110004, P.R. China
| | - Jingyi Jiang
- Clinical, Medical and Pharmaceutical College, China Medical University, Shenyang 110002, P.R. China
| | - Dongming Zheng
- Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang 110004, P.R. China
| | - Sishi Liu
- Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang 110004, P.R. China
| | - Caixia Liu
- Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang 110004, P.R. China
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60
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Rønnekleiv OK, Zhang C, Bosch MA, Kelly MJ. Kisspeptin and Gonadotropin-Releasing Hormone Neuronal Excitability: Molecular Mechanisms Driven by 17β-Estradiol. Neuroendocrinology 2014; 102:184-93. [PMID: 25612870 PMCID: PMC4459938 DOI: 10.1159/000370311] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Accepted: 12/02/2014] [Indexed: 11/19/2022]
Abstract
Kisspeptin is a neuropeptide that signals via a Gαq-coupled receptor, GPR54, in gonadotropin-releasing hormone (GnRH) neurons and is essential for pubertal maturation and fertility. Kisspeptin depolarizes and excites GnRH neurons primarily through the activation of canonical transient receptor potential (TRPC) channels and the inhibition of K+ channels. The gonadal steroid 17β-estradiol (E2) upregulates not only kisspeptin (Kiss1) mRNA but also increases the excitability of the rostral forebrain Kiss1 neurons. In addition, a primary postsynaptic action of E2 on GnRH neurons is to upregulate the expression of channel transcripts that orchestrate the downstream signaling of kisspeptin in GnRH neurons. These include not only TRPC4 channels but also low-voltage-activated T-type calcium channels and high-voltage-activated L-, N- and R-type calcium channel transcripts. Moreover, E2 has direct membrane-initiated actions to alter the excitability of GnRH neurons by enhancing ATP-sensitive potassium channel activity, which is critical for maintaining GnRH neurons in a hyperpolarized state for the recruitment of T-type calcium channels that are important for burst firing. Therefore, E2 modulates the excitability of GnRH neurons as well as of Kiss1 neurons by altering the expression and/or function of ion channels; moreover, kisspeptin provides critical excitatory input to GnRH neurons to facilitate burst firing activity and peptide release.
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Affiliation(s)
- Oline K. Rønnekleiv
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, Oregon, USA
| | - Chunguang Zhang
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon
| | - Martha A. Bosch
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon
| | - Martin J. Kelly
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, Oregon, USA
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61
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García-Caballero A, Gadotti VM, Stemkowski P, Weiss N, Souza IA, Hodgkinson V, Bladen C, Chen L, Hamid J, Pizzoccaro A, Deage M, François A, Bourinet E, Zamponi GW. The deubiquitinating enzyme USP5 modulates neuropathic and inflammatory pain by enhancing Cav3.2 channel activity. Neuron 2014; 83:1144-58. [PMID: 25189210 DOI: 10.1016/j.neuron.2014.07.036] [Citation(s) in RCA: 187] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2014] [Indexed: 12/22/2022]
Abstract
T-type calcium channels are essential contributors to the transmission of nociceptive signals in the primary afferent pain pathway. Here, we show that T-type calcium channels are ubiquitinated by WWP1, a plasma-membrane-associated ubiquitin ligase that binds to the intracellular domain III-IV linker region of the Cav3.2 T-type channel and modifies specific lysine residues in this region. A proteomic screen identified the deubiquitinating enzyme USP5 as a Cav3.2 III-IV linker interacting partner. Knockdown of USP5 via shRNA increases Cav3.2 ubiquitination, decreases Cav3.2 protein levels, and reduces Cav3.2 whole-cell currents. In vivo knockdown of USP5 or uncoupling USP5 from native Cav3.2 channels via intrathecal delivery of Tat peptides mediates analgesia in both inflammatory and neuropathic mouse models of mechanical hypersensitivity. Altogether, our experiments reveal a cell signaling pathway that regulates T-type channel activity and their role in nociceptive signaling.
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Affiliation(s)
- Agustin García-Caballero
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Vinicius M Gadotti
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Patrick Stemkowski
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Norbert Weiss
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Ivana A Souza
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Victoria Hodgkinson
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Chris Bladen
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Lina Chen
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Jawed Hamid
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Anne Pizzoccaro
- Laboratories of Excellence in Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, CNRS UMR5203, INSERM U661, IFR3 Universités Montpellier I&II, Montpellier, France
| | - Mickael Deage
- Laboratories of Excellence in Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, CNRS UMR5203, INSERM U661, IFR3 Universités Montpellier I&II, Montpellier, France
| | - Amaury François
- Laboratories of Excellence in Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, CNRS UMR5203, INSERM U661, IFR3 Universités Montpellier I&II, Montpellier, France
| | - Emmanuel Bourinet
- Laboratories of Excellence in Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, CNRS UMR5203, INSERM U661, IFR3 Universités Montpellier I&II, Montpellier, France
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
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Rivera-Arconada I, Lopez-Garcia JA. Characterisation of rebound depolarisation in mice deep dorsal horn neurons in vitro. Pflugers Arch 2014; 467:1985-96. [PMID: 25292284 DOI: 10.1007/s00424-014-1623-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 09/19/2014] [Accepted: 09/30/2014] [Indexed: 10/24/2022]
Abstract
Spinal dorsal horn neurons constitute the first relay for pain processing and participate in the processing of other sensory, motor and autonomic information. At the cellular level, intrinsic excitability is a factor contributing to network function. In turn, excitability is set by the array of ionic conductance expressed by neurons. Here, we set out to characterise rebound depolarisation following hyperpolarisation, a feature frequently described in dorsal horn neurons but never addressed in depth. To this end, an in vitro preparation of the spinal cord from mice pups was used combined with whole-cell recordings in current and voltage clamp modes. Results show the expression of H- and/or T-type currents in a significant proportion of dorsal horn neurons. The expression of these currents determines the presence of rebound behaviour at the end of hyperpolarising pulses. T-type calcium currents were associated to high-amplitude rebounds usually involving high-frequency action potential firing. H-currents were associated to low-amplitude rebounds less prone to elicit firing or firing at lower frequencies. For a large proportion of neurons expressing both currents, the H-current constitutes a mechanism to ensure a faster response after hyperpolarisations, adjusting the latency of the rebound firing. We conclude that rebound depolarisation and firing are intrinsic factors to many dorsal horn neurons that may constitute a mechanism to integrate somatosensory information in the spinal cord, allowing for a rapid switch from inhibited-to-excited states.
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Affiliation(s)
- Ivan Rivera-Arconada
- Department of Biología de Sistemas (Área Fisiología) Edificio de Medicina, Universidad de Alcala, 28871, Alcalá de Henares, Madrid, Spain
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63
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Functional expression of T-type Ca2+ channels in spinal motoneurons of the adult turtle. PLoS One 2014; 9:e108187. [PMID: 25255145 PMCID: PMC4177857 DOI: 10.1371/journal.pone.0108187] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 08/20/2014] [Indexed: 11/19/2022] Open
Abstract
Voltage-gated Ca2+ (CaV) channels are transmembrane proteins comprising three subfamilies named CaV1, CaV2 and CaV3. The CaV3 channel subfamily groups the low-voltage activated Ca2+ channels (LVA or T-type) a significant role in regulating neuronal excitability. CaV3 channel activity may lead to the generation of complex patterns of action potential firing such as the postinhibitory rebound (PIR). In the adult spinal cord, these channels have been found in dorsal horn interneurons where they control physiological events near the resting potential and participate in determining excitability. In motoneurons, CaV3 channels have been found during development, but their functional expression has not yet been reported in adult animals. Here, we show evidence for the presence of CaV3 channel-mediated PIR in motoneurons of the adult turtle spinal cord. Our results indicate that Ni2+ and NNC55-0396, two antagonists of CaV3 channel activity, inhibited PIR in the adult turtle spinal cord. Molecular biology and biochemical assays revealed the expression of the CaV3.1 channel isotype and its localization in motoneurons. Together, these results provide evidence for the expression of CaV3.1 channels in the spinal cord of adult animals and show also that these channels may contribute to determine the excitability of motoneurons.
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64
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Sellak H, Zhou C, Liu B, Chen H, Lincoln TM, Wu S. Transcriptional regulation of α1H T-type calcium channel under hypoxia. Am J Physiol Cell Physiol 2014; 307:C648-56. [PMID: 25099734 DOI: 10.1152/ajpcell.00210.2014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The low-voltage-activated T-type Ca(2+) channels play an important role in mediating the cellular responses to altered oxygen tension. Among three T-type channel isoforms, α1G, α1H, and α1I, only α1H was found to be upregulated under hypoxia. However, mechanisms underlying such hypoxia-dependent isoform-specific gene regulation remain incompletely understood. We, therefore, studied the hypoxia-dependent transcriptional regulation of α1G and α1H gene promoters with the aim to identify the functional hypoxia-response elements (HREs). In rat pulmonary artery smooth muscle cells (PASMCs) and pheochromocytoma (PC12) cells after hypoxia (3% O2) exposure, we observed a prominent increase in α1H mRNA at 12 h along with a significant rise in α1H-mediated T-type current at 24 and 48 h. We then cloned two promoter fragments from the 5'-flanking regions of rat α1G and α1H gene, 2,000 and 3,076 bp, respectively, and inserted these fragments into a luciferase reporter vector. Transient transfection of PASMCs and PC12 cells with these recombinant constructs and subsequent luciferase assay revealed a significant increase in luciferase activity from the reporter containing the α1H, but not α1G, promoter fragment under hypoxia. Using serial deletion and point mutation analysis strategies, we identified a functional HRE at site -1,173cacgc-1,169 within the α1H promoter region. Furthermore, an electrophoretic mobility shift assay using this site as a DNA probe demonstrated an increased binding activity to nuclear protein extracts from the cells after hypoxia exposure. Taken together, these findings indicate that hypoxia-induced α1H upregulation involves binding of hypoxia-inducible factor to an HRE within the α1H promoter region.
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Affiliation(s)
- Hassan Sellak
- Department of Anesthesiology and Perioperative Medicine, Georgia Regents University, Augusta, Georgia
| | - Chun Zhou
- Center for Lung Biology, University of South Alabama, Mobile, Alabama; Department of Pharmacology, University of South Alabama, Mobile, Alabama; and
| | - Bainan Liu
- Center for Lung Biology, University of South Alabama, Mobile, Alabama; Department of Pharmacology, University of South Alabama, Mobile, Alabama; and
| | - Hairu Chen
- Department of Anesthesiology and Perioperative Medicine, Georgia Regents University, Augusta, Georgia
| | - Thomas M Lincoln
- Department of Physiology, University of South Alabama, Mobile, Alabama
| | - Songwei Wu
- Department of Anesthesiology and Perioperative Medicine, Georgia Regents University, Augusta, Georgia;
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65
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Samios VN, Inoue T. Interleukin-1β and interleukin-6 affect electrophysiological properties of thalamic relay cells. Neurosci Res 2014; 87:16-25. [PMID: 25091392 DOI: 10.1016/j.neures.2014.06.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 06/12/2014] [Accepted: 06/17/2014] [Indexed: 11/28/2022]
Abstract
By acknowledging the relation between brain and body in health and disease, inflammatory processes may play a key role in this reciprocal relation. Pro-inflammatory cytokines such as interleukin-1β (IL-1β) and interleukin-6 (IL-6) are some of the agents involved in those processes. What exactly is their role in the CNS however is not that clear so far. To address the question of how pro-inflammatory cytokines may affect information processing at the cellular and molecular levels, relay neurons in the thalamic dorsal lateral geniculate nucleus in mouse brain slices were exposed to those cytokines and studied with the patch-clamp technique. IL-1β promoted hyperpolarization of the resting membrane potential (Vrest), decrease of input resistance (Rin), decrease of Ih rectification, decrease in action potential (AP) threshold and decrease in the number of APs in low threshold calcium spike (LTS) bursts, while IL-6 promoted decrease of Rin and decrease in the number of APs in LTS bursts. Computer simulations provided candidates for ionic conductance affected by those cytokines. Collectively, these findings demonstrate that IL-1β and IL-6 have modulatory effects on electrophysiological properties of thalamic neurons, implying that the thalamic functions may be affected by systemic disorders that present with high levels of those cytokines.
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Affiliation(s)
| | - Takafumi Inoue
- Department of Life Science and Medical Bioscience, Waseda University, Tokyo, Japan.
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66
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Perissinotti PP, Ethington EG, Cribbs L, Koob MD, Martin J, Piedras-Rentería ES. Down-regulation of endogenous KLHL1 decreases voltage-gated calcium current density. Cell Calcium 2014; 55:269-80. [PMID: 24703904 DOI: 10.1016/j.ceca.2014.03.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Revised: 03/04/2014] [Accepted: 03/09/2014] [Indexed: 10/25/2022]
Abstract
The actin-binding protein Kelch-like 1 (KLHL1) can modulate voltage-gated calcium channels in vitro. KLHL1 interacts with actin and with the pore-forming subunits of Cav2.1 and CaV3.2 calcium channels, resulting in up-regulation of P/Q and T-type current density. Here we tested whether endogenous KLHL1 modulates voltage gated calcium currents in cultured hippocampal neurons by down-regulating the expression of KLHL1 via adenoviral delivery of shRNA targeted against KLHL1 (shKLHL1). Control adenoviruses did not affect any of the neuronal properties measured, yet down-regulation of KLHL1 resulted in HVA current densities ~68% smaller and LVA current densities 44% smaller than uninfected controls, with a concomitant reduction in α(1A) and α(1H) protein levels. Biophysical analysis and western blot experiments suggest Ca(V)3.1 and 3.3 currents are also present in shKLHL1-infected neurons. Synapsin I levels, miniature postsynaptic current frequency, and excitatory and inhibitory synapse number were reduced in KLHL1 knockdown. This study corroborates the physiological role of KLHL1 as a calcium channel modulator and demonstrates a novel, presynaptic role.
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Affiliation(s)
- Paula P Perissinotti
- Cell and Molecular Physiology Department, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Avenue, Maywood, IL 60153, USA
| | - Elizabeth G Ethington
- Cell and Molecular Physiology Department, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Avenue, Maywood, IL 60153, USA
| | - Leanne Cribbs
- Office of Research Services, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Avenue, Maywood, IL 60153, USA
| | - Michael D Koob
- Institute for Translational Neuroscience, Department of Lab Medicine & Pathology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jody Martin
- Cell and Molecular Physiology Department, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Avenue, Maywood, IL 60153, USA; Neuroscience Institute, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Avenue, Maywood, IL 60153, USA
| | - Erika S Piedras-Rentería
- Cell and Molecular Physiology Department, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Avenue, Maywood, IL 60153, USA; Neuroscience Institute, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Avenue, Maywood, IL 60153, USA.
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67
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Crunelli V, David F, Leresche N, Lambert RC. Role for T-type Ca2+ channels in sleep waves. Pflugers Arch 2014; 466:735-45. [PMID: 24578015 DOI: 10.1007/s00424-014-1477-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 02/08/2014] [Indexed: 01/29/2023]
Abstract
Since their discovery more than 30 years ago, low-threshold T-type Ca(2+) channels (T channels) have been suggested to play a key role in many EEG waves of non-REM sleep, which has remained exclusively linked to the ability of these channels to generate low-threshold Ca(2+) potentials and associated high-frequency bursts of action potentials. Our present understanding of the biophysics and physiology of T channels, however, highlights a much more diverse and complex picture of the pivotal contributions that they make to different sleep rhythms. In particular, recent experimental evidence has conclusively demonstrated the essential contribution of thalamic T channels to the expression of slow waves of natural sleep and the key role played by Ca(2+) entry through these channels in the activation or modulation of other voltage-dependent channels that are important for the generation of both slow waves and sleep spindles. However, the precise contribution to sleep rhythms of T channels in cortical neurons and other sleep-controlling neuronal networks remains unknown, and a full understanding of the cellular and network mechanisms of sleep delta waves is still lacking.
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Affiliation(s)
- Vincenzo Crunelli
- School of Biosciences, Cardiff University, Museum Avenue, Cardiff, CF10 3US, UK,
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68
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T-type Ca2+ channels in absence epilepsy. Pflugers Arch 2014; 466:719-34. [DOI: 10.1007/s00424-014-1461-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Accepted: 01/22/2014] [Indexed: 11/25/2022]
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69
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Forward suppression in the auditory cortex is caused by the Ca(v)3.1 calcium channel-mediated switch from bursting to tonic firing at thalamocortical projections. J Neurosci 2014; 33:18940-50. [PMID: 24285899 DOI: 10.1523/jneurosci.3335-13.2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Brief sounds produce a period of suppressed responsiveness in the auditory cortex (ACx). This forward suppression can last for hundreds of milliseconds and might contribute to mechanisms of temporal separation of sounds and stimulus-specific adaptation. However, the mechanisms of forward suppression remain unknown. We used in vivo recordings of sound-evoked responses in the mouse ACx and whole-cell recordings, two-photon calcium imaging in presynaptic terminals, and two-photon glutamate uncaging in dendritic spines performed in brain slices to show that synaptic depression at thalamocortical (TC) projections contributes to forward suppression in the ACx. Paired-pulse synaptic depression at TC projections lasts for hundreds of milliseconds and is attributable to a switch between firing modes in thalamic neurons. Thalamic neurons respond to a brief depolarizing pulse with a burst of action potentials; however, within hundreds of milliseconds, the same pulse repeated again produces only a single action potential. This switch between firing modes depends on Ca(v)3.1 T-type calcium channels enriched in thalamic relay neurons. Pharmacologic inhibition or knockdown of Ca(v)3.1 T-type calcium channels in the auditory thalamus substantially reduces synaptic depression at TC projections and forward suppression in the ACx. These data suggest that Ca(v)3.1-dependent synaptic depression at TC projections contributes to mechanisms of forward suppression in the ACx.
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70
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Engbers JDT, Anderson D, Zamponi GW, Turner RW. Signal processing by T-type calcium channel interactions in the cerebellum. Front Cell Neurosci 2013; 7:230. [PMID: 24348329 PMCID: PMC3841819 DOI: 10.3389/fncel.2013.00230] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 11/06/2013] [Indexed: 01/28/2023] Open
Abstract
T-type calcium channels of the Cav3 family are unique among voltage-gated calcium channels due to their low activation voltage, rapid inactivation, and small single channel conductance. These special properties allow Cav3 calcium channels to regulate neuronal processing in the subthreshold voltage range. Here, we review two different subthreshold ion channel interactions involving Cav3 channels and explore the ability of these interactions to expand the functional roles of Cav3 channels. In cerebellar Purkinje cells, Cav3 and intermediate conductance calcium-activated potassium (IKCa) channels form a novel complex which creates a low voltage-activated, transient outward current capable of suppressing temporal summation of excitatory postsynaptic potentials (EPSPs). In large diameter neurons of the deep cerebellar nuclei, Cav3-mediated calcium current (I T) and hyperpolarization-activated cation current (I H) are activated during trains of inhibitory postsynaptic potentials. These currents have distinct, and yet synergistic, roles in the subthreshold domain with I T generating a rebound burst and I H controlling first spike latency and rebound spike precision. However, by shortening the membrane time constant the membrane returns towards resting value at a faster rate, allowing I H to increase the efficacy of I T and increase the range of burst frequencies that can be generated. The net effect of Cav3 channels thus depends on the channels with which they are paired. When expressed in a complex with a KCa channel, Cav3 channels reduce excitability when processing excitatory inputs. If functionally coupled with an HCN channel, the depolarizing effect of Cav3 channels is accentuated, allowing for efficient inversion of inhibitory inputs to generate a rebound burst output. Therefore, signal processing relies not only on the activity of individual subtypes of channels but also on complex interactions between ion channels whether based on a physical complex or by indirect effects on membrane properties.
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Affiliation(s)
- Jordan D. T. Engbers
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of CalgaryCalgary, Canada
| | - Dustin Anderson
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of CalgaryCalgary, Canada
| | - Gerald W. Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of CalgaryCalgary, Canada
| | - Ray W. Turner
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of CalgaryCalgary, Canada
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of CalgaryCalgary, Canada
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71
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Peruffo A, Giacomello M, Montelli S, Panin M, Cozzi B. Expression profile of the pore-forming subunits α1A and α1D in the foetal bovine hypothalamus: a mammal with a long gestation. Neurosci Lett 2013; 556:124-8. [PMID: 24148303 DOI: 10.1016/j.neulet.2013.10.026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 10/08/2013] [Accepted: 10/11/2013] [Indexed: 01/27/2023]
Abstract
This study describes the expression of the voltage operated calcium channels (VOCCs) subunits α1A (typical of the P/Q family) and α1D (of the L family) in the bovine hypothalamus. The expression of both P/Q and L families has been characterized in the brain of adult mammals. However, their distribution and expression during foetal neuronal differentiation have not yet been determined. The expression profile of the α1A and α1D pore-forming subunits was investigated during four embryonic stages in bovine foetuses. Our data suggest that the expressions of α1A and α1D are correlated during development, with an increase only in males that peaks on the last period of gestation. Bovine male hypothalami showed significantly higher α1A and α1D expression values in comparison to female ones during the whole developmental period. In the females, the expression profiles of both genes were constant during all the developmental time. Immunohistochemical studies confirmed the presence of the α1A and α1D protein subunits in foetal hypothalamic neurones starting from the third foetal stage. Our data provide new information on the hypothalamic expression of α1A and α1D subunits during development in a mammal with a long gestation period and a large and convoluted brain.
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Affiliation(s)
- A Peruffo
- Department of Comparative Biomedicine and Food Science, University of Padova, Vialedell'Università 16, 35020 Legnaro, PD, Italy.
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72
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Gulsuner S, Walsh T, Watts AC, Lee MK, Thornton AM, Casadei S, Rippey C, Shahin H, Nimgaonkar VL, Go RCP, Savage RM, Swerdlow NR, Gur RE, Braff DL, King MC, McClellan JM. Spatial and temporal mapping of de novo mutations in schizophrenia to a fetal prefrontal cortical network. Cell 2013; 154:518-29. [PMID: 23911319 DOI: 10.1016/j.cell.2013.06.049] [Citation(s) in RCA: 415] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 06/03/2013] [Accepted: 06/28/2013] [Indexed: 11/28/2022]
Abstract
Genes disrupted in schizophrenia may be revealed by de novo mutations in affected persons from otherwise healthy families. Furthermore, during normal brain development, genes are expressed in patterns specific to developmental stage and neuroanatomical structure. We identified de novo mutations in persons with schizophrenia and then mapped the responsible genes onto transcriptome profiles of normal human brain tissues from age 13 weeks gestation to adulthood. In the dorsolateral and ventrolateral prefrontal cortex during fetal development, genes harboring damaging de novo mutations in schizophrenia formed a network significantly enriched for transcriptional coexpression and protein interaction. The 50 genes in the network function in neuronal migration, synaptic transmission, signaling, transcriptional regulation, and transport. These results suggest that disruptions of fetal prefrontal cortical neurogenesis are critical to the pathophysiology of schizophrenia. These results also support the feasibility of integrating genomic and transcriptome analyses to map critical neurodevelopmental processes in time and space in the brain.
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Affiliation(s)
- Suleyman Gulsuner
- Department of Medicine and Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
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73
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Abstract
Low-voltage-activated T-type Ca(2+) channels are widely expressed in various types of neurons. Once deinactivated by hyperpolarization, T-type channels are ready to be activated by a small depolarization near the resting membrane potential and, therefore, are optimal for regulating the excitability and electroresponsiveness of neurons under physiological conditions near resting states. Ca(2+) influx through T-type channels engenders low-threshold Ca(2+) spikes, which in turn trigger a burst of action potentials. Low-threshold burst firing has been implicated in the synchronization of the thalamocortical circuit during sleep and in absence seizures. It also has been suggested that T-type channels play an important role in pain signal transmission, based on their abundant expression in pain-processing pathways in peripheral and central neurons. In this review, we will describe studies on the role of T-type Ca(2+) channels in the physiological as well as pathological generation of brain rhythms in sleep, absence epilepsy, and pain signal transmission. Recent advances in studies of T-type channels in the control of cognition will also be briefly discussed.
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Affiliation(s)
- Eunji Cheong
- Department of Biotechnology, Translational Research Center for Protein Function Control, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea.
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74
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Lambert RC, Bessaïh T, Crunelli V, Leresche N. The many faces of T-type calcium channels. Pflugers Arch 2013; 466:415-23. [PMID: 24043572 DOI: 10.1007/s00424-013-1353-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 09/06/2013] [Accepted: 09/07/2013] [Indexed: 01/27/2023]
Abstract
Since the discovery of low-voltage-activated T-type calcium channels in sensory neurons and the initial characterization of their physiological function mainly in inferior olive and thalamic neurons, studies on neuronal T-type currents have predominantly focused on the generation of low-threshold spike (and associated action potential burst firing) which is strictly conditioned by a preceding hyperpolarization. This T-type current mediated activity has become an archetype of the function of these channels, constraining our view of the potential physiological and pathological roles that they may play in controlling the excitability of single cells and neural networks. However, greatly helped by the recent availability of the first potent and selective antagonists for this class of calcium channels, novel T-type current functions are rapidly being uncovered, including their surprising involvement in neuronal excitability at depolarized membrane potentials and their complex control of dendritic integration and neurotransmitter release. These and other data summarized in this short review clearly indicate a much wider physiological involvement of T-type channels in neuronal activity than previously expected.
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75
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Gadotti VM, You H, Petrov RR, Berger ND, Diaz P, Zamponi GW. Analgesic effect of a mixed T-type channel inhibitor/CB2 receptor agonist. Mol Pain 2013; 9:32. [PMID: 23815854 PMCID: PMC3703287 DOI: 10.1186/1744-8069-9-32] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 06/29/2013] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Cannabinoid receptors and T-type calcium channels are potential targets for treating pain. Here we report on the design, synthesis and analgesic properties of a new mixed cannabinoid/T-type channel ligand, NMP-181. RESULTS NMP-181 action on CB1 and CB2 receptors was characterized in radioligand binding and in vitro GTPγ[35S] functional assays, and block of transiently expressed human Cav3.2 T-type channels by NMP-181 was analyzed by patch clamp. The analgesic effects and in vivo mechanism of action of NMP-181 delivered spinally or systemically were analyzed in formalin and CFA mouse models of pain. NMP-181 inhibited peak CaV3.2 currents with IC50 values in the low micromolar range and acted as a CB2 agonist. Inactivated state dependence further augmented the inhibitory action of NMP-181. NMP-181 produced a dose-dependent antinociceptive effect when administered either spinally or systemically in both phases of the formalin test. Both i.t. and i.p. treatment of mice with NMP-181 reversed the mechanical hyperalgesia induced by CFA injection. NMP-181 showed no antinocieptive effect in CaV3.2 null mice. The antinociceptive effect of intrathecally delivered NMP-181 in the formalin test was reversed by i.t. treatment of mice with AM-630 (CB2 antagonist). In contrast, the NMP-181-induced antinociception was not affected by treatment of mice with AM-281 (CB1 antagonist). CONCLUSIONS Our work shows that both T-type channels as well as CB2 receptors play a role in the antinociceptive action of NMP-181, and also provides a novel avenue for suppressing chronic pain through novel mixed T-type/cannabinoid receptor ligands.
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Affiliation(s)
- Vinicius M Gadotti
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
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76
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Bosch MA, Tonsfeldt KJ, Rønnekleiv OK. mRNA expression of ion channels in GnRH neurons: subtype-specific regulation by 17β-estradiol. Mol Cell Endocrinol 2013; 367:85-97. [PMID: 23305677 PMCID: PMC3570747 DOI: 10.1016/j.mce.2012.12.021] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 11/22/2012] [Accepted: 12/11/2012] [Indexed: 12/31/2022]
Abstract
Burst firing of neurons optimizes neurotransmitter release. GnRH neurons exhibit burst firing activity and T-type calcium channels, which are vital for burst firing activity, are regulated by 17β-estradiol (E2) in GnRH neurons. To further elucidate ion channel expression and E2 regulation during positive and negative feedback on GnRH neurosecretion, we used single cell RT-PCR and real-time qPCR to quantify channel mRNA expression in GnRH neurons. GFP-GnRH neurons expressed numerous ion channels important for burst firing activity. E2-treatment sufficient to induce an LH surge increased mRNA expression of HCN1 channels, which underlie the pacemaker current, the calcium-permeable Ca(V)1.3, Ca(V)2.2, Ca(V)2.3 channels, and TRPC4 channels, which mediate the kisspeptin excitatory response. E2 also decreased mRNA expression of SK3 channels underlying the medium AHP current. Therefore, E2 exerts fundamental changes in ion channel expression in GnRH neurons, to prime them to respond to incoming stimuli with increased excitability at the time of the surge.
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Affiliation(s)
- Martha A. Bosch
- Department of Physiology and Pharmacology, Oregon Health and Sciences University, Portland, OR 97239 USA
| | - Karen J. Tonsfeldt
- Department of Physiology and Pharmacology, Oregon Health and Sciences University, Portland, OR 97239 USA
| | - Oline K. Rønnekleiv
- Department of Physiology and Pharmacology, Oregon Health and Sciences University, Portland, OR 97239 USA
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Sciences University, Beaverton, OR 97005 USA
- Department of Anesthesiology and Perioperative Medicine, Oregon Health and Sciences University, Portland, OR 97239 USA
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77
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Cheong E, Shin HS. T-type Ca²⁺ channels in absence epilepsy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1560-71. [PMID: 23416255 DOI: 10.1016/j.bbamem.2013.02.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 01/15/2013] [Accepted: 02/01/2013] [Indexed: 11/28/2022]
Abstract
Low-voltage-activated T-type Ca²⁺ channels are highly expressed in the thalamocortical circuit, suggesting that they play a role in this brain circuit. Indeed, low-threshold burst firing mediated by T-type Ca²⁺ channels has long been implicated in the synchronization of the thalamocortical circuit. Over the past few decades, the conventional view has been that rhythmic burst firing mediated by T-type channels in both thalamic reticular nuclie (TRN) and thalamocortical (TC) neurons are equally critical in the generation of thalamocortical oscillations during sleep rhythms and spike-wave-discharges (SWDs). This review broadly investigates recent studies indicating that even though both TRN and TC nuclei are required for thalamocortical oscillations, the contributions of T-type channels to TRN and TC neurons are not equal in the genesis of sleep spindles and SWDs. T-type channels in TC neurons are an essential component of SWD generation, whereas the requirement for TRN T-type channels in SWD generation remains controversial at least in the GBL model of absence seizures. Therefore, a deeper understanding of the functional consequences of modulating each T-type channel subtype could guide the development of therapeutic tools for absence seizures while minimizing side effects on physiological thalamocortical oscillations. This article is part of a Special Issue entitled: Calcium channels.
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Affiliation(s)
- Eunji Cheong
- Department of Biotechnology, Translational Research Center for Protein Function Control, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea.
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78
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Francois A, Kerckhove N, Meleine M, Alloui A, Barrere C, Gelot A, Uebele VN, Renger JJ, Eschalier A, Ardid D, Bourinet E. State-dependent properties of a new T-type calcium channel blocker enhance Ca(V)3.2 selectivity and support analgesic effects. Pain 2012; 154:283-293. [PMID: 23257507 DOI: 10.1016/j.pain.2012.10.023] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 09/06/2012] [Accepted: 10/30/2012] [Indexed: 01/01/2023]
Abstract
T-type calcium channels encoded by the Ca(V)3.2 isoform are expressed in nociceptive primary afferent neurons where they contribute to hyperalgesia and thus are considered as a potential therapeutic target to treat pathological pain. Here we report that the small organic state-dependent T-type channel antagonist TTA-A2 efficiently inhibits recombinant and native Ca(V)3.2 currents. Although TTA-A2 is a pan Ca(V)3 blocker, it demonstrates a higher potency for Ca(V)3.2 compared to Ca(V)3.1. TTA-A2 selectivity for T-type currents was demonstrated in sensory neurons where it lowered cell excitability uniquely on neurons expressing T-type channels. In vivo pharmacology in Ca(V)3.2 knockout and wild type mice reveal that TTA-A2-mediated antinociception critically depends on Ca(V)3.2 expression. The pathophysiology of irritable bowel syndrome (IBS) was recently demonstrated to involve Ca(V)3.2 in a rat model of this disease. Oral administration of TTA-A2 produced a dose-dependent reduction of hypersensitivity in an IBS model, demonstrating its therapeutic potential for the treatment of pathological pain. Overall, our results suggest that the high potency of TTA-A2 in the depolarized state strengthen its analgesic efficacy and selectivity toward pathological pain syndromes. This characteristic would be beneficial for the development of analgesics targeting T-type channels, in particular for the treatment of pain associated with IBS.
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Affiliation(s)
- Amaury Francois
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France CNRS UMR5203, Montpellier, France INSERM, U661, Montpellier, France IFR3 Universités Montpellier I & II, Montpellier, France Clermont Université, Université d'Auvergne, Pharmacologie fondamentale et clinique de la douleur, BP 10448, F-63000 Clermont-Ferrand, France Inserm, U 766, F-63001 Clermont-Ferrand, France Merck Research Laboratories, West Point, PA, USA CHU Clermont-Ferrand, Service de Pharmacologie, F-63003 Clermont-Ferrand, France
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79
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Tai CH, Pan MK, Lin JJ, Huang CS, Yang YC, Kuo CC. Subthalamic discharges as a causal determinant of parkinsonian motor deficits. Ann Neurol 2012; 72:464-76. [DOI: 10.1002/ana.23618] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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80
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Alexander GE. Biology of Parkinson's disease: pathogenesis and pathophysiology of a multisystem neurodegenerative disorder. DIALOGUES IN CLINICAL NEUROSCIENCE 2012. [PMID: 22033559 PMCID: PMC3181806 DOI: 10.31887/dcns.2004.6.3/galexander] [Citation(s) in RCA: 272] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Parkinson's disease (PD) is the second most common movement disorder. The characteristic motor impairments - bradykinesia, rigidity, and resting tremor - result from degenerative loss of midbrain dopamine (DA) neurons in the substantia nigra, and are responsive to symptomatic treatment with dopaminergic medications and functional neurosurgery. PD is also the second most common neurodegenerative disorder. Viewed from this perspective, PD is a disorder of multiple functional systems, not simply the motor system, and of multiple neurotransmitter systems, not merely that of DA. The characteristic pathology - intraneuronal Lewy body inclusions and reduced numbers of surviving neurons - is similar in each of the targeted neuron groups, suggesting a common neurodegenerative process. Pathological and experimental studies indicate that oxidative stress, proteolytic stress, and inflammation figure prominently in the pathogenesis of PD. Yet, whether any of these mechanisms plays a causal role in human PD is unknown, because to date we have no proven neuroprotective therapies that slow or reverse disease progression in patients with PD. We are beginning to understand the pathophysiology of motor dysfunction in PD, but its etiopathogenesis as a neurodegenerative disorder remains poorly understood.
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Affiliation(s)
- Garrett E Alexander
- Department of Neurology, Emory University School of Medicine, Atlanta, Ga, USA
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81
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Modulation of low-voltage-activated T-type Ca²⁺ channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1550-9. [PMID: 22975282 DOI: 10.1016/j.bbamem.2012.08.032] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 08/29/2012] [Accepted: 08/30/2012] [Indexed: 12/16/2022]
Abstract
Low-voltage-activated T-type Ca²⁺ channels contribute to a wide variety of physiological functions, most predominantly in the nervous, cardiovascular and endocrine systems. Studies have documented the roles of T-type channels in sleep, neuropathic pain, absence epilepsy, cell proliferation and cardiovascular function. Importantly, novel aspects of the modulation of T-type channels have been identified over the last few years, providing new insights into their physiological and pathophysiological roles. Although there is substantial literature regarding modulation of native T-type channels, the underlying molecular mechanisms have only recently begun to be addressed. This review focuses on recent evidence that the Ca(v)3 subunits of T-type channels, Ca(v)3.1, Ca(v)3.2 and Ca(v)3.3, are differentially modulated by a multitude of endogenous ligands including anandamide, monocyte chemoattractant protein-1, endostatin, and redox and oxidizing agents. The review also provides an overview of recent knowledge gained concerning downstream pathways involving G-protein-coupled receptors. This article is part of a Special Issue entitled: Calcium channels.
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82
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Cui J, Ivanova E, Qi L, Pan ZH. Expression of CaV3.2 T-type Ca²⁺ channels in a subpopulation of retinal type-3 cone bipolar cells. Neuroscience 2012; 224:63-9. [PMID: 22909426 DOI: 10.1016/j.neuroscience.2012.08.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Revised: 08/09/2012] [Accepted: 08/10/2012] [Indexed: 11/17/2022]
Abstract
Retinal bipolar cells and ganglion cells are known to possess voltage-gated T-type Ca(2+) channels. Previous electrophysiological recording studies suggested that there is differential expression of different T-type Ca(2+) channel α1 subunits among bipolar cells. The detailed expression patterns of the individual T-type Ca(2+) channel subunits in the retina, however, remain unknown. In this study, we examined the expression of the Ca(V)3.2 Ca(2+) channel α1 subunit in the mouse retina using immunohistochemical analysis and patch-clamp recordings together with a Ca(V)3.2 knock out (KO) mouse line. The specificity of a Ca(V)3.2 Ca(2+) channel antibody was first confirmed in recombinant T-type Ca(2+) channels expressed in human embryonic kidney (HEK) cells and in Ca(V)3.2 KO mice. Our immunohistochemical analysis indicates that the Ca(V)3.2 antibody labels a subgroup of type-3 cone bipolar cells (CBCs), the PKAβII-immunopositive type-3 CBCs. The labeling was observed throughout the cell including dendrites and axon terminals. Our patch-clamp recording results further demonstrate that Ca(V)3.2 Ca(2+) channels contribute to the T-type Ca(2+) current in a subpopulation of type-3 CBCs. The findings of this study provide new insights into understanding the functional roles of T-type Ca(2+) channels in retinal processing.
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Affiliation(s)
- J Cui
- Department of Anatomy & Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, United States
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83
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T-type calcium channels in burst-firing, network synchrony, and epilepsy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1572-8. [PMID: 22885138 DOI: 10.1016/j.bbamem.2012.07.028] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 07/23/2012] [Accepted: 07/25/2012] [Indexed: 11/23/2022]
Abstract
Low voltage-activated (LVA) T-type calcium channels are well regarded as a key mechanism underlying the generation of neuronal burst-firing. Their low threshold for activation combined with a rapid and transient calcium conductance generates low-threshold calcium potentials (LTCPs), upon the crest of which high frequency action potentials fire for a brief period. Experiments using simultaneous electroencephalography (EEG) and intracellular recordings demonstrate that neuronal burst-firing is a likely causative component in the generation of normal sleep patterns as well as some pathophysiological conditions, such as epileptic seizures. However, less is known as to how these neuronal bursts impact brain behavior, in particular network synchronization. In this review we summarize recent findings concerning the role of T-type calcium channels in burst-firing and discuss how they likely contribute to the generation of network synchrony. We further outline the function of burst-firing and network synchrony in terms of epileptic seizures. This article is part of a Special Issue entitled: Calcium channels.
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84
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Elimination of the actin-binding domain in kelch-like 1 protein induces T-type calcium channel modulation only in the presence of action potential waveforms. JOURNAL OF SIGNAL TRANSDUCTION 2012; 2012:505346. [PMID: 22848812 PMCID: PMC3401526 DOI: 10.1155/2012/505346] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Accepted: 05/30/2012] [Indexed: 11/19/2022]
Abstract
The Kelch-like 1 protein (KLHL1) is a neuronal actin-binding protein that modulates calcium channel function. It increases the current density of Cav3.2 (α1H) calcium channels via direct interaction with α1H and actin-F, resulting in biophysical changes in Cav3.2 currents and an increase in recycling endosomal activity with subsequent increased α1H channel number at the plasma membrane. Interestingly, removal of the actin-binding Kelch motif (ΔKelch) prevents the increase in Cav3.2 current density seen with wild-type KLHL1 when tested with normal square pulse protocols but does not preclude the effect when tested using action potential waveforms (AP).
Here, we dissected the kinetic properties of the AP waveform that confer the mutant Kelch the ability to interact with Cav3.2 and induce an increase in calcium influx. We modified the action potential waveform by altering the slopes of repolarization and/or recovery from hyperpolarization or by changing the duration of the depolarization plateau or the hyperpolarization phase and tested the modulation of Cav3.2 by the mutant ΔKelch. Our results show that the recovery phase from hyperpolarization phase determines the conformational changes that allow the α1H subunit to properly interact with mutant KLHL1 lacking its actin-binding Kelch domains, leading to increased Ca influx.
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85
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Senatore A, Spafford JD. Gene transcription and splicing of T-type channels are evolutionarily-conserved strategies for regulating channel expression and gating. PLoS One 2012; 7:e37409. [PMID: 22719839 PMCID: PMC3376122 DOI: 10.1371/journal.pone.0037409] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 04/19/2012] [Indexed: 01/17/2023] Open
Abstract
T-type calcium channels operate within tightly regulated biophysical constraints for supporting rhythmic firing in the brain, heart and secretory organs of invertebrates and vertebrates. The snail T-type gene, LCa(v)3 from Lymnaea stagnalis, possesses alternative, tandem donor splice sites enabling a choice of a large exon 8b (201 aa) or a short exon 25c (9 aa) in cytoplasmic linkers, similar to mammalian homologs. Inclusion of optional 25c exons in the III-IV linker of T-type channels speeds up kinetics and causes hyperpolarizing shifts in both activation and steady-state inactivation of macroscopic currents. The abundant variant lacking exon 25c is the workhorse of embryonic Ca(v)3 channels, whose high density and right-shifted activation and availability curves are expected to increase pace-making and allow the channels to contribute more significantly to cellular excitation in prenatal tissue. Presence of brain-enriched, optional exon 8b conserved with mammalian Ca(v)3.1 and encompassing the proximal half of the I-II linker, imparts a ~50% reduction in total and surface-expressed LCa(v)3 channel protein, which accounts for reduced whole-cell calcium currents of +8b variants in HEK cells. Evolutionarily conserved optional exons in cytoplasmic linkers of Ca(v)3 channels regulate expression (exon 8b) and a battery of biophysical properties (exon 25c) for tuning specialized firing patterns in different tissues and throughout development.
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86
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van Loo KMJ, Schaub C, Pernhorst K, Yaari Y, Beck H, Schoch S, Becker AJ. Transcriptional regulation of T-type calcium channel CaV3.2: bi-directionality by early growth response 1 (Egr1) and repressor element 1 (RE-1) protein-silencing transcription factor (REST). J Biol Chem 2012; 287:15489-501. [PMID: 22431737 DOI: 10.1074/jbc.m111.310763] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The pore-forming Ca(2+) channel subunit Ca(V)3.2 mediates a low voltage-activated (T-type) Ca(2+) current (I(CaT)) that contributes pivotally to neuronal and cardiac pacemaker activity. Despite the importance of tightly regulated Ca(V)3.2 levels, the mechanisms regulating its transcriptional dynamics are not well understood. Here, we have identified two key factors that up- and down-regulate the expression of the gene encoding Ca(V)3.2 (Cacna1h). First, we determined the promoter region and observed several stimulatory and inhibitory clusters. Furthermore, we found binding sites for the transcription factor early growth response 1 (Egr1/Zif268/Krox-24) to be highly overrepresented within the Ca(V)3.2 promoter region. mRNA expression analyses and dual-luciferase promoter assays revealed that the Ca(V)3.2 promoter was strongly activated by Egr1 overexpression in vitro and in vivo. Subsequent chromatin immunoprecipitation assays in NG108-15 cells and mouse hippocampi confirmed specific Egr1 binding to the Ca(V)3.2 promoter. Congruently, whole-cell I(CaT) values were significantly larger after Egr1 overexpression. Intriguingly, Egr1-induced activation of the Ca(V)3.2 promoter was effectively counteracted by the repressor element 1-silencing transcription factor (REST). Thus, Egr1 and REST can bi-directionally regulate Ca(V)3.2 promoter activity and mRNA expression and, hence, the size of I(CaT). This mechanism has critical implications for the regulation of neuronal and cardiac Ca(2+) homeostasis under physiological conditions and in episodic disorders such as arrhythmias and epilepsy.
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Affiliation(s)
- Karen M J van Loo
- Department of Neuropathology, University of Bonn Medical Center, D-53105 Bonn, Germany.
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87
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88
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Abstract
17β-Oestradiol (E(2)) is essential for cyclical gonadotrophin-releasing hormone (GnRH) neuronal activity and secretion. In particular, E(2) increases the excitability of GnRH neurones during the afternoon of pro-oestrus in the rodent, which is associated with increased synthesis and secretion of GnRH. It is well established that E(2) regulates the activity of GnRH neurones through both presynaptic and postsynaptic mechanisms. E(2) significantly modulates the mRNA expression of numerous ion channels in GnRH neurones and alters the associated endogenous conductances, including potassium (K(ATP) , A-type) currents and low-voltage T-type and high-voltage L-type calcium currents. Notably, K(ATP) channels are critical for maintaining GnRH neurones in a hyperpolarised state for recruiting the T-type calcium channels, which are important for burst firing in GnRH neurones. In addition, there are other critical channels contributing to burst firing pattern, including the small conductance Ca(2+) -activated K(+) channels that may be modulated by E(2) . Despite these advances, the cellular mechanisms underlying the cyclical GnRH neuronal activity and GnRH release are largely unknown. Ultimately, the ensemble of both pre- and postsynaptic targets of the actions of E(2) will dictate the excitability and activity pattern of GnRH neurones.
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Affiliation(s)
- O K Rønnekleiv
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR 97239-3098, USA.
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89
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Cao XH, Byun HS, Chen SR, Pan HL. Diabetic neuropathy enhances voltage-activated Ca2+ channel activity and its control by M4 muscarinic receptors in primary sensory neurons. J Neurochem 2011; 119:594-603. [PMID: 21883220 PMCID: PMC3192928 DOI: 10.1111/j.1471-4159.2011.07456.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Painful neuropathy is one of the most serious complications of diabetes and remains difficult to treat. The muscarinic acetylcholine receptor (mAChR) agonists have a profound analgesic effect on painful diabetic neuropathy. Here we determined changes in T-type and high voltage-activated Ca(2+) channels (HVACCs) and their regulation by mAChRs in dorsal root ganglion (DRG) neurons in a rat model of diabetic neuropathy. The HVACC currents in large neurons, T-type currents in medium and large neurons, the percentage of small DRG neurons with T-type currents, and the Cav3.2 mRNA level were significantly increased in diabetic rats compared with those in control rats. The mAChR agonist oxotremorine-M significantly inhibited HVACCs in a greater proportion of DRG neurons with and without T-type currents in diabetic than in control rats. In contrast, oxotremorine-M had no effect on HVACCs in small and large neurons with T-type currents and in most medium neurons with T-type currents from control rats. The M(2) and M(4) antagonist himbacine abolished the effect of oxotremorine-M on HVACCs in both groups. The selective M(4) antagonist muscarinic toxin-3 caused a greater attenuation of the effect of oxotremorine-M on HVACCs in small and medium DRG neurons in diabetic than in control rats. Additionally, the mRNA and protein levels of M(4), but not M(2), in the DRG were significantly greater in diabetic than in control rats. Our findings suggest that diabetic neuropathy potentiates the activity of T-type and HVACCs in primary sensory neurons. M(4) mAChRs are up-regulated in DRG neurons and probably account for increased muscarinic analgesic effects in diabetic neuropathic pain.
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MESH Headings
- Animals
- Calcium Channels, T-Type/biosynthesis
- Calcium Channels, T-Type/genetics
- Calcium Channels, T-Type/metabolism
- Calcium Channels, T-Type/physiology
- Diabetes Mellitus, Experimental/genetics
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/pathology
- Diabetic Neuropathies/genetics
- Diabetic Neuropathies/metabolism
- Diabetic Neuropathies/pathology
- Disease Models, Animal
- Male
- Neuralgia/etiology
- Neuralgia/pathology
- Neuralgia/prevention & control
- RNA, Messenger/biosynthesis
- Rats
- Rats, Sprague-Dawley
- Receptor, Muscarinic M4/biosynthesis
- Receptor, Muscarinic M4/genetics
- Receptor, Muscarinic M4/physiology
- Sensory Receptor Cells/metabolism
- Sensory Receptor Cells/pathology
- Up-Regulation/genetics
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Affiliation(s)
- Xue-Hong Cao
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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90
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Bando SY, Alegro MC, Amaro E, Silva AV, Castro LHM, Wen HT, Lima LDA, Brentani H, Moreira-Filho CA. Hippocampal CA3 transcriptome signature correlates with initial precipitating injury in refractory mesial temporal lobe epilepsy. PLoS One 2011; 6:e26268. [PMID: 22022585 PMCID: PMC3194819 DOI: 10.1371/journal.pone.0026268] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 09/23/2011] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Prolonged febrile seizures constitute an initial precipitating injury (IPI) commonly associated with refractory mesial temporal lobe epilepsy (RMTLE). In order to investigate IPI influence on the transcriptional phenotype underlying RMTLE we comparatively analyzed the transcriptomic signatures of CA3 explants surgically obtained from RMTLE patients with (FS) or without (NFS) febrile seizure history. Texture analyses on MRI images of dentate gyrus were conducted in a subset of surgically removed sclerotic hippocampi for identifying IPI-associated histo-radiological alterations. METHODOLOGY/PRINCIPAL FINDINGS DNA microarray analysis revealed that CA3 global gene expression differed significantly between FS and NFS subgroups. An integrative functional genomics methodology was used for characterizing the relations between GO biological processes themes and constructing transcriptional interaction networks defining the FS and NFS transcriptomic signatures and its major gene-gene links (hubs). Co-expression network analysis showed that: i) CA3 transcriptomic profiles differ according to the IPI; ii) FS distinctive hubs are mostly linked to glutamatergic signalization while NFS hubs predominantly involve GABAergic pathways and neurotransmission modulation. Both networks have relevant hubs related to nervous system development, what is consistent with cell genesis activity in the hippocampus of RMTLE patients. Moreover, two candidate genes for therapeutic targeting came out from this analysis: SSTR1, a relevant common hub in febrile and afebrile transcriptomes, and CHRM3, due to its putative role in epilepsy susceptibility development. MRI texture analysis allowed an overall accuracy of 90% for pixels correctly classified as belonging to FS or NFS groups. Histological examination revealed that granule cell loss was significantly higher in FS hippocampi. CONCLUSIONS/SIGNIFICANCE CA3 transcriptional signatures and dentate gyrus morphology fairly correlate with IPI in RMTLE, indicating that FS-RMTLE represents a distinct phenotype. These findings may shed light on the molecular mechanisms underlying refractory epilepsy phenotypes and contribute to the discovery of novel specific drug targets for therapeutic interventions.
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Affiliation(s)
- Silvia Y. Bando
- Department of Pediatrics, Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, São Paulo, Brazil
| | - Maryana C. Alegro
- Laboratory of Integrated Systems, Escola Politécnica da Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Edson Amaro
- Department of Radiology, Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, São Paulo, Brazil
| | - Alexandre V. Silva
- Department of Biosciences, Universidade Federal de São Paulo, Santos, São Paulo, Brazil
| | - Luiz H. M. Castro
- Clinical Neurology Division, Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Hung-Tzu Wen
- Epilepsy Surgery Group, Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Leandro de A. Lima
- Laboratory of Biotechnology, Hospital do Câncer AC Camargo, São Paulo, São Paulo, Brazil
| | - Helena Brentani
- Department of Psychiatry, Instituto Nacional de Psiquiatria do Desenvolvimento and Laboratório de Investigação Médica 23, Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, São Paulo, Brazil
| | - Carlos Alberto Moreira-Filho
- Department of Pediatrics, Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, São Paulo, Brazil
- * E-mail:
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91
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Boehme R, Uebele VN, Renger JJ, Pedroarena C. Rebound excitation triggered by synaptic inhibition in cerebellar nuclear neurons is suppressed by selective T-type calcium channel block. J Neurophysiol 2011; 106:2653-61. [PMID: 21849607 DOI: 10.1152/jn.00612.2011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Following hyperpolarizing inputs, many neurons respond with an increase in firing rate, a phenomenon known as rebound excitation. Rebound excitation has been proposed as a mechanism to encode and process inhibitory signals and transfer them to target structures. Activation of low-voltage-activated T-type calcium channels and the ensuing low-threshold calcium spikes is one of the mechanisms proposed to support rebound excitation. However, there is still not enough evidence that the hyperpolarization provided by inhibitory inputs, particularly those dependent on chloride ions, is adequate to deinactivate a sufficient number of T-type calcium channels to drive rebound excitation on return to baseline. Here, this issue was investigated in the deep cerebellar nuclear neurons (DCNs), which receive the output of the cerebellar cortex conveyed exclusively by the inhibitory Purkinje cells and are also known to display rebound excitation. Using cerebellar slices and whole cell recordings of large DCNs, we show that a novel piperidine-based compound that selectively antagonizes T-type calcium channel activity, 3,5-dichloro-N-[1-(2,2-dimethyl-tetrahydropyran-4-ylmethyl)-4-fluoro-piperidin-4-ylmethyl]-benzamide (TTA-P2), suppressed rebound excitation elicited by current injection as well as by synaptic inhibition, whereas other electrophysiological properties of large DCNs were unaltered. Furthermore, TTA-P2 suppressed transient high-frequency rebounds found in DCNs with low-threshold spikes as well as the slow rebounds present in DCNs without low-threshold spikes. These findings demonstrate that chloride-dependent synaptic inhibition effectively triggers T-type calcium channel-mediated rebounds and that the latter channels may support slow rebound excitation in neurons without low-threshold spikes.
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Affiliation(s)
- Rebecca Boehme
- Dept. of Cognitive Neurology, Hertie Institute, Univ. of Tübingen, Otfried Müller Str. 27, 72076 Tübingen, Germany
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92
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Schulman JJ, Cancro R, Lowe S, Lu F, Walton KD, Llinás RR. Imaging of thalamocortical dysrhythmia in neuropsychiatry. Front Hum Neurosci 2011; 5:69. [PMID: 21863138 PMCID: PMC3149146 DOI: 10.3389/fnhum.2011.00069] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Accepted: 07/15/2011] [Indexed: 12/22/2022] Open
Abstract
Abnormal brain activity dynamics, in the sense of a thalamocortical dysrhythmia (TCD), has been proposed as the underlying mechanism for a subset of disorders that bridge the traditional delineations of neurology and neuropsychiatry. In order to test this proposal from a psychiatric perspective, a study using magnetoencephalography (MEG) was implemented in subjects with schizophrenic spectrum disorder (n = 14), obsessive–compulsive disorder (n = 10), or depressive disorder (n = 5) and in control individuals (n = 18). Detailed CNS electrophysiological analysis of these patients, using MEG, revealed the presence of abnormal theta range spectral power with typical TCD characteristics, in all cases. The use of independent component analysis and minimum-norm-based methods localized such TCD to ventromedial prefrontal and temporal cortices. The observed mode of oscillation was spectrally equivalent but spatially distinct from that of TCD observed in other related disorders, including Parkinson's disease, central tinnitus, neuropathic pain, and autism. The present results indicate that the functional basis for much of these pathologies may relate most fundamentally to the category of calcium channelopathies and serve as a model for the cellular substrate for low-frequency oscillations present in these psychiatric disorders, providing a basis for therapeutic strategies.
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Affiliation(s)
- Joshua J Schulman
- Department of Physiology and Neuroscience, New York University School of Medicine New York, NY, USA
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93
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Ku WH, Schneider SP. Multiple T-type Ca2+ current subtypes in electrophysiologically characterized hamster dorsal horn neurons: possible role in spinal sensory integration. J Neurophysiol 2011; 106:2486-98. [PMID: 21795620 DOI: 10.1152/jn.01083.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Whole cell patch-clamp recordings were used to investigate the contribution of transient, low-threshold calcium currents (I(T)) to firing properties of hamster spinal dorsal horn neurons. I(T) was widely, though not uniformly, expressed by cells in Rexed's laminae I-IV and correlated with the pattern of action potential discharge evoked under current-clamp conditions: I(T) in neurons responding to constant membrane depolarization with one or two action potentials was nearly threefold larger than I(T) in cells responding to the same activation with continuous firing. I(T) was evoked by depolarizing voltage ramps exceeding 46 mV/s and increased with ramp slope (240-2,400 mV/s). Bath application of 200 μM Ni(2+) depressed ramp-activated I(T). Phasic firing recorded in current clamp could only be activated by membrane depolarizations exceeding ∼43-46 mV/s and was blocked by Ni(2+) and mibefradil, suggesting I(T) as an underlying mechanism. Two components of I(T), "fast" and "slow," were isolated based on a difference in time constant of inactivation (12 ms and 177 ms, respectively). The amplitude of the fast subtype depended on the slope of membrane depolarization and was twice as great in burst-firing cells than in cells having a tonic discharge. Post hoc single-cell RT-PCR analyses suggested that the fast component is associated with the Ca(V)3.1 channel subtype. I(T) may enhance responses of phasic-firing dorsal horn neurons to rapid membrane depolarizations and contribute to an ability to discriminate between afferent sensory inputs that encode high- and low-frequency stimulus information.
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Affiliation(s)
- Wen-hsin Ku
- Dept. of Physiology, Michigan State Univ., East Lansing, MI 48824-3320, USA
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94
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T-type calcium channels contribute to colonic hypersensitivity in a rat model of irritable bowel syndrome. Proc Natl Acad Sci U S A 2011; 108:11268-73. [PMID: 21690417 DOI: 10.1073/pnas.1100869108] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The symptoms of irritable bowel syndrome (IBS) include significant abdominal pain and bloating. Current treatments are empirical and often poorly efficacious, and there is a need for the development of new and efficient analgesics aimed at IBS patients. T-type calcium channels have previously been validated as a potential target to treat certain neuropathic pain pathologies. Here we report that T-type calcium channels encoded by the Ca(V)3.2 isoform are expressed in colonic nociceptive primary afferent neurons and that they contribute to the exaggerated pain perception in a butyrate-mediated rodent model of IBS. Both the selective genetic inhibition of Ca(V)3.2 channels and pharmacological blockade with calcium channel antagonists attenuates IBS-like painful symptoms. Mechanistically, butyrate acts to promote the increased insertion of Ca(V)3.2 channels into primary sensory neuron membranes, likely via a posttranslational effect. The butyrate-mediated regulation can be recapitulated with recombinant Ca(V)3.2 channels expressed in HEK cells and may provide a convenient in vitro screening system for the identification of T-type channel blockers relevant to visceral pain. These results implicate T-type calcium channels in the pathophysiology of chronic visceral pain and suggest Ca(V)3.2 as a promising target for the development of efficient analgesics for the visceral discomfort and pain associated with IBS.
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95
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Bidaud I, Lory P. Hallmarks of the channelopathies associated with L-type calcium channels: a focus on the Timothy mutations in Ca(v)1.2 channels. Biochimie 2011; 93:2080-6. [PMID: 21664226 DOI: 10.1016/j.biochi.2011.05.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Accepted: 05/19/2011] [Indexed: 11/29/2022]
Abstract
Within the voltage-gated calcium channels (Cav channels) family, there are four genes coding for the L-type Cav channels (Cav1). The Cav1 channels underly many important physiological functions like excitation-contraction coupling, hormone secretion, neuronal excitability and gene transcription. Mutations found in the genes encoding the Cav channels define a wide variety of diseases called calcium channelopathies and all four genes coding the Cav1 channels are carrying such mutations. L-type calcium channelopathies include muscular, neurological, cardiac and vision syndromes. Among them, the Timothy syndrome (TS) is linked to missense mutations in CACNA1C, the gene that encodes the Ca(v)1.2 subunit. Here we review the important features of the Cav1 channelopathies. We also report on the specific properties of TS-Ca(v)1.2 channels, which display non-inactivating calcium current as well as higher plasma membrane expression. Overall, we conclude that both electrophysiological and surface expression properties must be investigated to better account for the functional consequences of mutations linked to calcium channelopathies.
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Affiliation(s)
- Isabelle Bidaud
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier, France
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96
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Cain SM, Snutch TP. Contributions of T-type calcium channel isoforms to neuronal firing. Channels (Austin) 2011; 4:475-82. [PMID: 21139420 DOI: 10.4161/chan.4.6.14106] [Citation(s) in RCA: 138] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Low voltage-activated (LVA) T-type calcium channels play critical roles in the excitability of many cell types and are a focus of research aimed both at understanding the physiological basis of calcium channel-dependent signaling and the underlying pathophysiology associated with hyperexcitability disorders such as epilepsy. These channels play a critical role towards neuronal firing in both conducting calcium ions during action potentials and also in switching neurons between distinct modes of firing. In this review the properties of the CaV3.1, CaV3.2 and CaV3.3 T-type channel isoforms is discussed in relation to their individual contributions to action potentials during burst and tonic firing states as well their roles in switching between firing states.
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Affiliation(s)
- Stuart M Cain
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada.
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97
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Parajuli LK, Fukazawa Y, Watanabe M, Shigemoto R. Subcellular distribution of α1G subunit of T-type calcium channel in the mouse dorsal lateral geniculate nucleus. J Comp Neurol 2011; 518:4362-74. [PMID: 20853512 DOI: 10.1002/cne.22461] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
T-type calcium channels play a pivotal role in regulating neural membrane excitability in the nervous system. However, the precise subcellular distributions of T-type channel subunits and their implication for membrane excitability are not well understood. Here we investigated the subcellular distribution of the α1G subunit of the calcium channel which is expressed highly in the mouse dorsal lateral geniculate nucleus (dLGN). Light microscopic analysis demonstrated that dLGN exhibits intense immunoperoxidase reactivity for the α1G subunit. Electron microscopic observation showed that the labeling was present in both the relay cells and interneurons and was found in the somatodendritic, but not axonal, domains of these cells. Most of the immunogold particles for the α1G subunit were either associated with the plasma membrane or the intracellular membranes. Reconstruction analysis of serial electron microscopic images revealed that the intensity of the intracellular labeling exhibited a gradient such that the labeling density was higher in the proximal dendrite and progressively decreased towards the distal dendrite. In contrast, the plasma membrane-associated particles were distributed with a uniform density over the somatodendritic surface of dLGN cells. The labeling density in the relay cell plasma membrane was about 3-fold higher than that of the interneurons. These results provide ultrastructural evidence for cell-type-specific expression levels and for uniform expression density of the α1G subunit over the plasma membrane of dLGN cells.
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Affiliation(s)
- Laxmi Kumar Parajuli
- Division of Cerebral Structure, National Institute for Physiological Sciences, Okazaki 444-8787, Japan
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98
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Rønnekleiv OK, Bosch MA, Zhang C. Regulation of endogenous conductances in GnRH neurons by estrogens. Brain Res 2010; 1364:25-34. [PMID: 20816765 PMCID: PMC2992606 DOI: 10.1016/j.brainres.2010.08.096] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 08/24/2010] [Accepted: 08/27/2010] [Indexed: 11/20/2022]
Abstract
17β-estradiol (E2) regulates the activity of the gonadotropin-releasing hormone (GnRH) neurons through both presynaptic and postsynaptic mechanisms, and this ovarian steroid hormone is essential for cyclical GnRH neuronal activity and secretion. E2 has significant actions to modulate the mRNA expression of numerous ion channels in GnRH neurons and/or to enhance (suppress) endogenous conductances (currents) including potassium (K(ATP), A-type) and calcium low voltage T-type and high voltage L-type currents. Also, it is well documented that E2 can alter the excitability of GnRH neurons via direct action, but the intracellular signaling cascades mediating these actions are not well understood. As an example, K(ATP) channels are critical ion channels needed for maintaining GnRH neurons in a hyperpolarized state for recruiting T-type calcium channels that are important for burst firing in GnRH neurons. E2 modulates the activity of K(ATP) channels via a membrane-initiated signaling pathway in GnRH neurons. Obviously there are other channels, including the small conductance activated K(+) (SK) channels, that maybe modulated by this signaling pathway, but the ensemble of mER-, ERα-, and ERβ-mediated effects both pre- and post-synaptic will ultimately dictate the excitability of GnRH neurons.
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Affiliation(s)
- Oline K Rønnekleiv
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR 97239, USA.
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99
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Markandeya YS, Fahey JM, Pluteanu F, Cribbs LL, Balijepalli RC. Caveolin-3 regulates protein kinase A modulation of the Ca(V)3.2 (alpha1H) T-type Ca2+ channels. J Biol Chem 2010; 286:2433-44. [PMID: 21084288 DOI: 10.1074/jbc.m110.182550] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Voltage-gated T-type Ca(2+) channel Ca(v)3.2 (α(1H)) subunit, responsible for T-type Ca(2+) current, is expressed in different tissues and participates in Ca(2+) entry, hormonal secretion, pacemaker activity, and arrhythmia. The precise subcellular localization and regulation of Ca(v)3.2 channels in native cells is unknown. Caveolae containing scaffolding protein caveolin-3 (Cav-3) localize many ion channels, signaling proteins and provide temporal and spatial regulation of intracellular Ca(2+) in different cells. We examined the localization and regulation of the Ca(v)3.2 channels in cardiomyocytes. Immunogold labeling and electron microscopy analysis demonstrated co-localization of the Ca(v)3.2 channel and Cav-3 relative to caveolae in ventricular myocytes. Co-immunoprecipitation from neonatal ventricular myocytes or transiently transfected HEK293 cells demonstrated that Ca(v)3.1 and Ca(v)3.2 channels co-immunoprecipitate with Cav-3. GST pulldown analysis confirmed that the N terminus region of Cav-3 closely interacts with Ca(v)3.2 channels. Whole cell patch clamp analysis demonstrated that co-expression of Cav-3 significantly decreased the peak Ca(v)3.2 current density in HEK293 cells, whereas co-expression of Cav-3 did not alter peak Ca(v)3.1 current density. In neonatal mouse ventricular myocytes, overexpression of Cav-3 inhibited the peak T-type calcium current (I(Ca,T)) and adenovirus (AdCa(v)3.2)-mediated increase in peak Ca(v)3.2 current, but did not affect the L-type current. The protein kinase A-dependent stimulation of I(Ca,T) by 8-Br-cAMP (membrane permeable cAMP analog) was abolished by siRNA directed against Cav-3. Our findings on functional modulation of the Ca(v)3.2 channels by Cav-3 is important for understanding the compartmentalized regulation of Ca(2+) signaling during normal and pathological processes.
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Affiliation(s)
- Yogananda S Markandeya
- Department of Medicine, Cellular and Molecular Arrhythmia Research Program, University of Wisconsin, Madison, Wisconsin 53706, USA
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100
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Walton KD, Dubois M, Llinás RR. Abnormal thalamocortical activity in patients with Complex Regional Pain Syndrome (CRPS) Type I. Pain 2010; 150:41-51. [DOI: 10.1016/j.pain.2010.02.023] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 01/19/2010] [Accepted: 02/12/2010] [Indexed: 11/26/2022]
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