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López Soto EJ, Agosti F, Cabral A, Mustafa ER, Damonte VM, Gandini MA, Rodríguez S, Castrogiovanni D, Felix R, Perelló M, Raingo J. Constitutive and ghrelin-dependent GHSR1a activation impairs CaV2.1 and CaV2.2 currents in hypothalamic neurons. ACTA ACUST UNITED AC 2015; 146:205-19. [PMID: 26283199 PMCID: PMC4555474 DOI: 10.1085/jgp.201511383] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 07/13/2015] [Indexed: 12/22/2022]
Abstract
Constitutive and ligand-dependent GHSR1a activity attenuates CaV2 current and hypothalamic GABA release through distinct mechanisms and signaling pathways. The growth hormone secretagogue receptor type 1a (GHSR1a) has the highest known constitutive activity of any G protein–coupled receptor (GPCR). GHSR1a mediates the action of the hormone ghrelin, and its activation increases transcriptional and electrical activity in hypothalamic neurons. Although GHSR1a is present at GABAergic presynaptic terminals, its effect on neurotransmitter release remains unclear. The activities of the voltage-gated calcium channels, CaV2.1 and CaV2.2, which mediate neurotransmitter release at presynaptic terminals, are modulated by many GPCRs. Here, we show that both constitutive and agonist-dependent GHSR1a activity elicit a strong impairment of CaV2.1 and CaV2.2 currents in rat and mouse hypothalamic neurons and in a heterologous expression system. Constitutive GHSR1a activity reduces CaV2 currents by a Gi/o-dependent mechanism that involves persistent reduction in channel density at the plasma membrane, whereas ghrelin-dependent GHSR1a inhibition is reversible and involves altered CaV2 gating via a Gq-dependent pathway. Thus, GHSR1a differentially inhibits CaV2 channels by Gi/o or Gq protein pathways depending on its mode of activation. Moreover, we present evidence suggesting that GHSR1a-mediated inhibition of CaV2 attenuates GABA release in hypothalamic neurons, a mechanism that could contribute to neuronal activation through the disinhibition of postsynaptic neurons.
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Affiliation(s)
- Eduardo Javier López Soto
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Francina Agosti
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Agustina Cabral
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Emilio Roman Mustafa
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Valentina Martínez Damonte
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Maria Alejandra Gandini
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute, 07000 México D.F., México
| | - Silvia Rodríguez
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Daniel Castrogiovanni
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Ricardo Felix
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute, 07000 México D.F., México
| | - Mario Perelló
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Jesica Raingo
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
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Huang D, Huang S, Peers C, Du X, Zhang H, Gamper N. GABAB receptors inhibit low-voltage activated and high-voltage activated Ca(2+) channels in sensory neurons via distinct mechanisms. Biochem Biophys Res Commun 2015; 465:188-93. [PMID: 26239659 DOI: 10.1016/j.bbrc.2015.07.137] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 07/28/2015] [Indexed: 12/16/2022]
Abstract
Growing evidence suggests that mammalian peripheral somatosensory neurons express functional receptors for gamma-aminobutyric acid, GABAA and GABAB. Moreover, local release of GABA by pain-sensing (nociceptive) nerve fibres has also been suggested. Yet, the functional significance of GABA receptor triggering in nociceptive neurons is not fully understood. Here we used patch-clamp recordings from small-diameter cultured DRG neurons to investigate effects of GABAB receptor agonist baclofen on voltage-gated Ca(2+) currents. We found that baclofen inhibited both low-voltage activated (LVA, T-type) and high-voltage activated (HVA) Ca(2+) currents in a proportion of DRG neurons by 22% and 32% respectively; both effects were sensitive to Gi/o inhibitor pertussis toxin. Inhibitory effect of baclofen on both current types was about twice less efficacious as compared to that of the μ-opioid receptor agonist DAMGO. Surprisingly, only HVA but not LVA current modulation by baclofen was partially prevented by G protein inhibitor GDP-β-S. In contrast, only LVA but not HVA current modulation was reversed by the application of a reducing agent dithiothreitol (DTT). Inhibition of T-type Ca(2+) current by baclofen and the recovery of such inhibition by DTT were successfully reconstituted in the expression system. Our data suggest that inhibition of LVA current in DRG neurons by baclofen is partially mediated by an unconventional signaling pathway that involves a redox mechanism. These findings reinforce the idea of targeting peripheral GABA receptors for pain relief.
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Affiliation(s)
- Dongyang Huang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China
| | - Sha Huang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China
| | - Chris Peers
- Faculty of Medicine and Health, University of Leeds, Leeds, UK
| | - Xiaona Du
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China.
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
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53
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Zhu H, Ding Q. Lower expression level of two RAGE alternative splicing isoforms in Alzheimer’s disease. Neurosci Lett 2015; 597:66-70. [DOI: 10.1016/j.neulet.2015.04.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 04/13/2015] [Accepted: 04/18/2015] [Indexed: 11/26/2022]
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Schröder W, Lambert DG, Ko MC, Koch T. Functional plasticity of the N/OFQ-NOP receptor system determines analgesic properties of NOP receptor agonists. Br J Pharmacol 2015; 171:3777-800. [PMID: 24762001 DOI: 10.1111/bph.12744] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 04/07/2014] [Accepted: 04/15/2014] [Indexed: 12/12/2022] Open
Abstract
Despite high sequence similarity between NOP (nociceptin/orphanin FQ opioid peptide) and opioid receptors, marked differences in endogenous ligand selectivity, signal transduction, phosphorylation, desensitization, internalization and trafficking have been identified; underscoring the evolutionary difference between NOP and opioid receptors. Activation of NOP receptors affects nociceptive transmission in a site-specific manner, with antinociceptive effects prevailing after peripheral and spinal activation, and pronociceptive effects after supraspinal activation in rodents. The net effect of systemically administered NOP receptor agonists on nociception is proposed to depend on the relative contribution of peripheral, spinal and supraspinal activation, and this may depend on experimental conditions. Functional expression and regulation of NOP receptors at peripheral and central sites of the nociceptive pathway exhibits a high degree of plasticity under conditions of neuropathic and inflammatory pain. In rodents, systemically administered NOP receptor agonists exerted antihypersensitive effects in models of neuropathic and inflammatory pain. However, they were largely ineffective in acute pain while concomitantly evoking severe motor side effects. In contrast, systemic administration of NOP receptor agonists to non-human primates (NHPs) exerted potent and efficacious antinociception in the absence of motor and sedative side effects. The reason for this species difference with respect to antinociceptive efficacy and tolerability is not clear. Moreover, co-activation of NOP and μ-opioid peptide (MOP) receptors synergistically produced antinociception in NHPs. Hence, both selective NOP receptor as well as NOP/MOP receptor agonists may hold potential for clinical use as analgesics effective in conditions of acute and chronic pain.
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Affiliation(s)
- W Schröder
- Department of Translational Science, Global Innovation, Grünenthal GmbH, Aachen, Germany
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55
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Abstract
Chronic pain is very difficult to treat. Thus, novel analgesics are a critical area of research. Strong pre-clinical evidence supports the analgesic effects of α-conopeptides, Vc1.1 and RgIA, which block α9α10 nicotinic acetylcholine receptors (nAChRs). However, the analgesic mechanism is controversial. Some evidence supports the block of α9α10 nAChRs as an analgesic mechanism, while other evidence supports the inhibition of N-type CaV (CaV2.2) current via activation of GABAB receptors. Here we reassess the effect of Vc1.1 and RgIA on CaV current in rat sensory neurons. Unlike the previous findings, we found highly variable effects among individual sensory neurons, but on average only minimal inhibition induced by Vc1.1, and no significant effect on the current by RgIA. We also investigated the potential involvement of GABAB receptors in the Vc1.1 induced inhibition, and found no correlation between the size of CaV current inhibition induced by baclofen (GABAB agonist) vs. that induced by Vc1.1. Thus, GABAB receptors are unlikely to mediate the Vc1.1 induced CaV current inhibition. Based on the present findings, CaV current inhibition in dorsal root ganglia is unlikely to be the predominant mechanism by which either Vc1.1 or RgIA induce analgesia. SIGNIFICANCE STATEMENT Better analgesic drugs are desperately needed to help physicians to treat pain. While many pre-clinical studies support the analgesic effects of α-conopeptides, Vc1.1 and RgIA, the mechanism is controversial. The development of improved α-conopeptide analgesics would be greatly facilitated by a complete understanding of the analgesic mechanism. However, we show that we cannot reproduce one of the proposed analgesic mechanisms, which is an irreversible inhibition of CaV current in a majority of sensory neurons.
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Berecki G, McArthur JR, Cuny H, Clark RJ, Adams DJ. Differential Cav2.1 and Cav2.3 channel inhibition by baclofen and α-conotoxin Vc1.1 via GABAB receptor activation. ACTA ACUST UNITED AC 2014; 143:465-79. [PMID: 24688019 PMCID: PMC3971658 DOI: 10.1085/jgp.201311104] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The analgesic α-conotoxin Vc1.1 inhibits Cav2.3 channels through a GABAB receptor–dependent pathway involving c-Src. Neuronal Cav2.1 (P/Q-type), Cav2.2 (N-type), and Cav2.3 (R-type) calcium channels contribute to synaptic transmission and are modulated through G protein–coupled receptor pathways. The analgesic α-conotoxin Vc1.1 acts through γ-aminobutyric acid type B (GABAB) receptors (GABABRs) to inhibit Cav2.2 channels. We investigated GABABR-mediated modulation by Vc1.1, a cyclized form of Vc1.1 (c-Vc1.1), and the GABABR agonist baclofen of human Cav2.1 or Cav2.3 channels heterologously expressed in human embryonic kidney cells. 50 µM baclofen inhibited Cav2.1 and Cav2.3 channel Ba2+ currents by ∼40%, whereas c-Vc1.1 did not affect Cav2.1 but potently inhibited Cav2.3, with a half-maximal inhibitory concentration of ∼300 pM. Depolarizing paired pulses revealed that ∼75% of the baclofen inhibition of Cav2.1 was voltage dependent and could be relieved by strong depolarization. In contrast, baclofen or Vc1.1 inhibition of Cav2.3 channels was solely mediated through voltage-independent pathways that could be disrupted by pertussis toxin, guanosine 5′-[β-thio]diphosphate trilithium salt, or the GABABR antagonist CGP55845. Overexpression of the kinase c-Src significantly increased inhibition of Cav2.3 by c-Vc1.1. Conversely, coexpression of a catalytically inactive double mutant form of c-Src or pretreatment with a phosphorylated pp60c-Src peptide abolished the effect of c-Vc1.1. Site-directed mutational analyses of Cav2.3 demonstrated that tyrosines 1761 and 1765 within exon 37 are critical for inhibition of Cav2.3 by c-Vc1.1 and are involved in baclofen inhibition of these channels. Remarkably, point mutations introducing specific c-Src phosphorylation sites into human Cav2.1 channels conferred c-Vc1.1 sensitivity. Our findings show that Vc1.1 inhibition of Cav2.3, which defines Cav2.3 channels as potential targets for analgesic α-conotoxins, is caused by specific c-Src phosphorylation sites in the C terminus.
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Affiliation(s)
- Géza Berecki
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria 3083, Australia
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57
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Affiliation(s)
- Ann R Rittenhouse
- Department of Microbiology and Physiological Systems, Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA 01605
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58
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Huynh TG, Cuny H, Slesinger PA, Adams DJ. Novel Mechanism of Voltage-Gated N-type (Cav2.2) Calcium Channel Inhibition Revealed through α-Conotoxin Vc1.1 Activation of the GABAB Receptor. Mol Pharmacol 2014; 87:240-50. [DOI: 10.1124/mol.114.096156] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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59
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Groen JL, Andrade A, Ritz K, Jalalzadeh H, Haagmans M, Bradley TEJ, Jongejan A, Verbeek DS, Nürnberg P, Denome S, Hennekam RCM, Lipscombe D, Baas F, Tijssen MAJ. CACNA1B mutation is linked to unique myoclonus-dystonia syndrome. Hum Mol Genet 2014; 24:987-93. [PMID: 25296916 DOI: 10.1093/hmg/ddu513] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Using exome sequencing and linkage analysis in a three-generation family with a unique dominant myoclonus-dystonia-like syndrome with cardiac arrhythmias, we identified a mutation in the CACNA1B gene, coding for neuronal voltage-gated calcium channels CaV2.2. This mutation (c.4166G>A;p.Arg1389His) is a disruptive missense mutation in the outer region of the ion pore. The functional consequences of the identified mutation were studied using whole-cell and single-channel patch recordings. High-resolution analyses at the single-channel level showed that, when open, R1389H CaV2.2 channels carried less current compared with WT channels. Other biophysical channel properties were unaltered in R1389H channels including ion selectivity, voltage-dependent activation or voltage-dependent inactivation. CaV2.2 channels regulate transmitter release at inhibitory and excitatory synapses. Functional changes could be consistent with a gain-of-function causing the observed hyperexcitability characteristic of this unique myoclonus-dystonia-like syndrome associated with cardiac arrhythmias.
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Affiliation(s)
- Justus L Groen
- Department of Neurology, Department of Genome Analysis and Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands
| | - Arturo Andrade
- Department of Neuroscience, Brown University, Providence RI 02912, USA
| | | | | | | | | | - Aldo Jongejan
- Bioinformatics Laboratory, Clinical Epidemiology, Biostatistics and Bioinformatics and
| | | | - Peter Nürnberg
- Cologne Center for Genomics, University of Cologne, Cologne, Germany
| | - Sylvia Denome
- Department of Neuroscience, Brown University, Providence RI 02912, USA
| | - Raoul C M Hennekam
- Department of Pediatrics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Diane Lipscombe
- Department of Neuroscience, Brown University, Providence RI 02912, USA
| | | | - Marina A J Tijssen
- Department of Neurology, University of Groningen, Groningen, The Netherlands and
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60
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Li Z, He SQ, Xu Q, Yang F, Tiwari V, Liu Q, Tang Z, Han L, Chu YX, Wang Y, Hin N, Tsukamoto T, Slusher B, Guan X, Wei F, Raja SN, Dong X, Guan Y. Activation of MrgC receptor inhibits N-type calcium channels in small-diameter primary sensory neurons in mice. Pain 2014; 155:1613-1621. [PMID: 24813294 PMCID: PMC4104261 DOI: 10.1016/j.pain.2014.05.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 04/16/2014] [Accepted: 05/02/2014] [Indexed: 01/24/2023]
Abstract
Mas-related G-protein-coupled receptor subtype C (mouse MrgC11 and rat rMrgC), expressed specifically in small-diameter primary sensory neurons, may constitute a novel pain inhibitory mechanism. We have shown previously that intrathecal administration of MrgC-selective agonists can strongly attenuate persistent pain in various animal models. However, the underlying mechanisms for MrgC agonist-induced analgesia remain elusive. Here, we conducted patch-clamp recordings to test the effect of MrgC agonists on high-voltage-activated (HVA) calcium current in small-diameter dorsal root ganglion (DRG) neurons. Using pharmacological approaches, we show for the first time that an MrgC agonist (JHU58) selectively and dose-dependently inhibits N-type, but not L- or P/Q-type, HVA calcium channels in mouse DRG neurons. Activation of HVA calcium channels is important to neurotransmitter release and synaptic transmission. Patch-clamp recordings in spinal cord slices showed that JHU58 attenuated the evoked excitatory postsynaptic currents in substantia gelatinosa (SG) neurons in wild-type mice, but not in Mrg knockout mice, after peripheral nerve injury. These findings indicate that activation of endogenously expressed MrgC receptors at central terminals of primary sensory fibers may decrease peripheral excitatory inputs onto SG neurons. Together, these results suggest potential cellular and molecular mechanisms that may contribute to intrathecal MrgC agonist-induced analgesia. Because MrgC shares substantial genetic homogeneity with human MrgX1, our findings may suggest a rationale for developing intrathecally delivered MrgX1 receptor agonists to treat pathological pain in humans and provide critical insight regarding potential mechanisms that may underlie its analgesic effects.
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Affiliation(s)
- Zhe Li
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Shao-Qiu He
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Qian Xu
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Fei Yang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Vinod Tiwari
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Qin Liu
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Zongxiang Tang
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Liang Han
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Yu-Xia Chu
- Department of Neural and Pain Sciences, Program in Neuroscience, Dental School, University of Maryland, Baltimore, Maryland, 21201
| | - Yun Wang
- Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, 100020, China
| | - Niyada Hin
- Brain Science Institute, Johns Hopkins University, Baltimore, Maryland, 21205
| | - Takashi Tsukamoto
- Brain Science Institute, Johns Hopkins University, Baltimore, Maryland, 21205
- Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Barbara Slusher
- Brain Science Institute, Johns Hopkins University, Baltimore, Maryland, 21205
- Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Xiaowei Guan
- Department of Human Anatomy, Nanjing Medical University, Nanjing, 210029, China
| | - Feng Wei
- Department of Neural and Pain Sciences, Program in Neuroscience, Dental School, University of Maryland, Baltimore, Maryland, 21201
| | - Srinivasa N Raja
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
- Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21287
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
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61
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Agosti F, López Soto EJ, Cabral A, Castrogiovanni D, Schioth HB, Perelló M, Raingo J. Melanocortin 4 receptor activation inhibits presynaptic N-type calcium channels in amygdaloid complex neurons. Eur J Neurosci 2014; 40:2755-65. [PMID: 24943127 DOI: 10.1111/ejn.12650] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 04/30/2014] [Accepted: 05/05/2014] [Indexed: 12/22/2022]
Abstract
The melanocortin 4 receptor (MC4R) is a G protein-coupled receptor involved in food intake and energy expenditure regulation. MC4R activation modifies neuronal activity but the molecular mechanisms by which this regulation occurs remain unclear. Here, we tested the hypothesis that MC4R activation regulates the activity of voltage-gated calcium channels and, as a consequence, synaptic activity. We also tested whether the proposed effect occurs in the amygdala, a brain area known to mediate the anorexigenic actions of MC4R signaling. Using the patch-clamp technique, we found that the activation of MC4R with its agonist melanotan II specifically inhibited 34.5 ± 1.5% of N-type calcium currents in transiently transfected HEK293 cells. This inhibition was concentration-dependent, voltage-independent and occluded by the Gαs pathway inhibitor cholera toxin. Moreover, we found that melanotan II specifically inhibited 25.9 ± 2.0% of native N-type calcium currents and 55.4 ± 14.4% of evoked inhibitory postsynaptic currents in mouse cultured amygdala neurons. In vivo, we found that the MC4R agonist RO27-3225 increased the marker of cellular activity c-Fos in several components of the amygdala, whereas the N-type channel blocker ω conotoxin GVIA increased c-Fos expression exclusively in the central subdivision of the amygdala. Thus, MC4R specifically inhibited the presynaptic N-type channel subtype, and this inhibition may be important for the effects of melanocortin in the central subdivision of the amygdala.
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Affiliation(s)
- Francina Agosti
- Laboratory of Electrophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), La Plata, Buenos Aires, Argentina
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62
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Bourinet E, Altier C, Hildebrand ME, Trang T, Salter MW, Zamponi GW. Calcium-permeable ion channels in pain signaling. Physiol Rev 2014; 94:81-140. [PMID: 24382884 DOI: 10.1152/physrev.00023.2013] [Citation(s) in RCA: 208] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The detection and processing of painful stimuli in afferent sensory neurons is critically dependent on a wide range of different types of voltage- and ligand-gated ion channels, including sodium, calcium, and TRP channels, to name a few. The functions of these channels include the detection of mechanical and chemical insults, the generation of action potentials and regulation of neuronal firing patterns, the initiation of neurotransmitter release at dorsal horn synapses, and the ensuing activation of spinal cord neurons that project to pain centers in the brain. Long-term changes in ion channel expression and function are thought to contribute to chronic pain states. Many of the channels involved in the afferent pain pathway are permeable to calcium ions, suggesting a role in cell signaling beyond the mere generation of electrical activity. In this article, we provide a broad overview of different calcium-permeable ion channels in the afferent pain pathway and their role in pain pathophysiology.
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63
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Abstract
Chronic pain is a major therapeutic problem as the current treatment options are unsatisfactory with low efficacy and deleterious side effects. Voltage-gated Ca2+ channels (VGCCs), which are multi-complex proteins consisting of α1, β, γ, and α2δ subunits, play an important role in pain signaling. These channels are involved in neurogenic inflammation, excitability, and neurotransmitter release in nociceptors. It has been previously shown that N-type VGCCs (Cav2.2) are a major pain target. U.S. FDA approval of three Cav2.2 antagonists, gabapentin, pregabalin, and ziconotide, for chronic pain underlies the importance of this channel subtype. Also, there has been increasing evidence that L-type (Cav1.2) or T-type (Cav3.2) VGCCs may be involved in pain signaling and chronic pain. In order to develop novel pain therapeutics and to understand the role of VGCC subtypes, discovering subtype selective VGCC inhibitors or methods that selectively target the inhibitor into nociceptors would be essential. This review describes the various VGCC subtype inhibitors and the potential of utilizing VGCC subtypes as targets of chronic pain. Development of VGCC subtype inhibitors and targeting them into nociceptors will contribute to a better understanding of the roles of VGCC subtypes in pain at a spinal level as well as development of a novel class of analgesics for chronic pain.
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Affiliation(s)
- Seungkyu Lee
- F. M. Kirby Neurobiology Center, Children's Hospital Boston, Boston MA 02115 USA; ; Department of Neurobiology, Harvard Medical School, Boston MA 02115 USA
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64
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Jiang YQ, Andrade A, Lipscombe D. Spinal morphine but not ziconotide or gabapentin analgesia is affected by alternative splicing of voltage-gated calcium channel CaV2.2 pre-mRNA. Mol Pain 2013; 9:67. [PMID: 24369063 PMCID: PMC3916075 DOI: 10.1186/1744-8069-9-67] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 12/18/2013] [Indexed: 01/30/2023] Open
Abstract
Presynaptic voltage-gated calcium CaV2.2 channels play a privileged role in spinal level sensitization following peripheral nerve injury. Direct and indirect inhibitors of CaV2.2 channel activity in spinal dorsal horn are analgesic in chronic pain states. CaV2.2 channels represent a family of splice isoforms that are expressed in different combinations according to cell-type. A pair of mutually exclusive exons in the CaV2.2 encoding Cacna1b gene, e37a and e37b, differentially influence morphine analgesia. In mice that lack exon e37a, which is enriched in nociceptors, the analgesic efficacy of intrathecal morphine against noxious thermal stimuli is reduced. Here we ask if sequences unique to e37a influence: the development of abnormal thermal and mechanical sensitivity associated with peripheral nerve injury; and the actions of two other classes of analgesics that owe part or all of their efficacy to CaV2.2 channel inhibition. We find that: i) the analgesic efficacy of morphine, but not ziconotide or gabapentin, is reduced in mice lacking e37a, ii) the induction and maintenance of behaviors associated with sensitization that accompany peripheral nerve injury, do not require e37a-specific sequence, iii) intrathecal morphine, but not ziconotide or gabapentin analgesia to thermal stimuli is significantly lower in wild-type mice after peripheral nerve injury, iv) the analgesic efficacy of ziconotide and gabapentin to mechanical stimuli is reduced following nerve injury, and iv) intrathecal morphine analgesia to thermal stimuli in mice lacking e37a is not further reduced by peripheral nerve injury. Our findings show that the analgesic action of morphine, but not ziconotide or gabapentin, to thermal stimuli is linked to which Cacna1b exon, e37a or e37b, is selected during alternative pre-mRNA splicing.
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Affiliation(s)
| | | | - Diane Lipscombe
- Department of Neuroscience, Brown University, Providence, Rhode Island, USA.
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Dunn TW, Sossin WS. Inhibition of the Aplysia sensory neuron calcium current with dopamine and serotonin. J Neurophysiol 2013; 110:2071-81. [DOI: 10.1152/jn.00217.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The inhibition of Aplysia pleural mechanosensory neuron synapses by dopamine and serotonin through activation of endogenous dopaminergic and expressed 5-HT1Apl(a)/b receptors, respectively, involves a reduction in action potential-associated calcium influx. We show that the inhibition of synaptic efficacy is downstream of the readily releasable pool, suggesting that inhibition is at the level of calcium secretion coupling, likely a result of the changes in the calcium current. Indeed, the inhibitory responses directly reduce a CaV2-like calcium current in isolated sensory neurons. The inhibition of the calcium current is voltage independent as it is not affected by a strong depolarizing prepulse, consistent with other invertebrate CaV2 calcium currents. Similar to voltage-independent inhibition of vertebrate nociceptors, inhibition was blocked with Src tyrosine kinase inhibitors. The data suggest a conserved mechanism by which G protein-coupled receptor activation can inhibit the CaV2 calcium current in nociceptive neurons.
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Affiliation(s)
- Tyler W. Dunn
- Department Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Wayne S. Sossin
- Department Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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66
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Lipscombe D, Allen SE, Toro CP. Control of neuronal voltage-gated calcium ion channels from RNA to protein. Trends Neurosci 2013; 36:598-609. [PMID: 23907011 DOI: 10.1016/j.tins.2013.06.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2013] [Revised: 06/27/2013] [Accepted: 06/28/2013] [Indexed: 12/22/2022]
Abstract
Voltage-gated calcium ion (CaV) channels convert neuronal activity into rapid intracellular calcium signals to trigger a myriad of cellular responses. Their involvement in major neurological and psychiatric diseases, and importance as therapeutic targets, has propelled interest in subcellular-specific mechanisms that align CaV channel activity to specific tasks. Here, we highlight recent studies that delineate mechanisms controlling the expression of CaV channels at the level of RNA and protein. We discuss the roles of RNA editing and alternative pre-mRNA splicing in generating CaV channel isoforms with activities specific to the demands of individual cells; the roles of ubiquitination and accessory proteins in regulating CaV channel expression; and the specific binding partners that contribute to both pre- and postsynaptic CaV channel function.
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Affiliation(s)
- Diane Lipscombe
- Department of Neuroscience, Brown University, Providence, RI 02912, USA.
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67
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Cens T, Rousset M, Collet C, Raymond V, Démares F, Quintavalle A, Bellis M, Le Conte Y, Chahine M, Charnet P. Characterization of the first honeybee Ca²⁺ channel subunit reveals two novel species- and splicing-specific modes of regulation of channel inactivation. Pflugers Arch 2013; 465:985-96. [PMID: 23588376 DOI: 10.1007/s00424-013-1223-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 01/18/2013] [Accepted: 01/21/2013] [Indexed: 10/27/2022]
Abstract
The honeybee is a model system to study learning and memory, and Ca(2+) signals play a key role in these processes. We have cloned, expressed, and characterized the first honeybee Ca(2+) channel subunit. We identified two splice variants of the Apis CaVβ Ca(2+) channel subunit (Am-CaVβ) and demonstrated expression in muscle and neurons. Although AmCaVβ shares with vertebrate CaVβ subunits the SH3 and GK domains, it beholds a unique N terminus that is alternatively spliced in the first exon to produce a long (a) and short (b) variant. When expressed with the CaV2 channels both, AmCaVβa and AmCaVβb, increase current amplitude, shift the voltage-sensitivity of the channel, and slow channel inactivation as the vertebrate CaVβ2a subunit does. However, as opposed to CaVβ2a, slow inactivation induced by Am-CaVβa was insensitive to palmitoylation but displayed a unique PI3K sensitivity. Inactivation produced by the b variant was PI3K-insensitive but staurosporine/H89-sensitive. Deletion of the first exon suppressed the sensitivity to PI3K inhibitors, staurosporine, or H89. Recording of Ba(2+) currents in Apis neurons or muscle cells evidenced a sensitivity to PI3K inhibitors and H89, suggesting that both AmCaVβ variants may be important to couple cell signaling to Ca(2+) entry in vivo. Functional interactions with phospho-inositide and identification of phosphorylation sites in AmCaVβa and AmCaVβb N termini, respectively, suggest that AmCaVβ splicing promoted two novel and alternative modes of regulation of channel activity with specific signaling pathways. This is the first description of a splicing-dependent kinase switch in the regulation of Ca(2+) channel activity by CaVβ subunit.
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Affiliation(s)
- Thierry Cens
- CRBM, UMR 5237, CNRS, Université de Montpellier I&II, Montpellier, France
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68
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Brackett DM, Qing F, Amieux PS, Sellers DL, Horner PJ, Morris DR. FMR1 transcript isoforms: association with polyribosomes; regional and developmental expression in mouse brain. PLoS One 2013; 8:e58296. [PMID: 23505481 PMCID: PMC3591412 DOI: 10.1371/journal.pone.0058296] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 02/01/2013] [Indexed: 12/31/2022] Open
Abstract
The primary transcript of the mammalian Fragile X Mental Retardation-1 gene (Fmr1), like many transcripts in the central nervous system, is alternatively spliced to yield mRNAs encoding multiple proteins, which can possess quite different biochemical properties. Despite the fact that the relative levels of the 12 Fmr1 transcript isoforms examined here vary by as much as two orders of magnitude amongst themselves in both adult and embryonic mouse brain, all are associated with polyribosomes, consistent with translation into the corresponding isoforms of the protein product, FMRP (Fragile X Mental Retardation Protein). Employing the RiboTag methodology developed in our laboratory, the relative proportions of the 7 most abundant transcript isoforms were measured specifically in neurons and found to be similar to those identified in whole brain. Measurements of isoform profiles across 11 regions of adult brain yielded similar distributions, with the exceptions of the hippocampus and the olfactory bulb. These two regions differ from most of the brain in relative amounts of transcripts encoding an alternate form of one of the KH RNA binding domains. A possible relationship between patterns of expression in the hippocampus and olfactory bulb and the presence of neuroblasts in these two regions is suggested by the isoform patterns in early embryonic brain and in cultured neural progenitor cells. These results demonstrate that the relative levels of the Fmr1 isoforms are modulated according to developmental stage, highlighting the complex ramifications of losing all the protein isoforms in individuals with Fragile X Syndrome. It should also be noted that, of the eight most prominent FMRP isoforms (1–3, 6–9 and 12) in mouse, only two have the major site of phosphorylation at Ser-499, which is thought to be involved in some of the regulatory interactions of this protein.
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Affiliation(s)
- David M. Brackett
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Feng Qing
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Paul S. Amieux
- Department of Pharmacology; University of Washington, Seattle, Washington, United States of America
| | - Drew L. Sellers
- Department of Neurological Surgery, University of Washington, Seattle, Washington, United States of America
| | - Philip J. Horner
- Department of Neurological Surgery, University of Washington, Seattle, Washington, United States of America
| | - David R. Morris
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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69
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Hannon HE, Atchison WD. Omega-conotoxins as experimental tools and therapeutics in pain management. Mar Drugs 2013; 11:680-99. [PMID: 23470283 PMCID: PMC3705365 DOI: 10.3390/md11030680] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 02/14/2013] [Accepted: 02/15/2013] [Indexed: 12/24/2022] Open
Abstract
Neuropathic pain afflicts a large percentage of the global population. This form of chronic, intractable pain arises when the peripheral or central nervous systems are damaged, either directly by lesion or indirectly through disease. The comorbidity of neuropathic pain with other diseases, including diabetes, cancer, and AIDS, contributes to a complex pathogenesis and symptom profile. Because most patients present with neuropathic pain refractory to current first-line therapeutics, pharmaceuticals with greater efficacy in pain management are highly desired. In this review we discuss the growing application of ω-conotoxins, small peptides isolated from Conus species, in the management of neuropathic pain. These toxins are synthesized by predatory cone snails as a component of paralytic venoms. The potency and selectivity with which ω-conotoxins inhibit their molecular targets, voltage-gated Ca2+ channels, is advantageous in the treatment of neuropathic pain states, in which Ca2+ channel activity is characteristically aberrant. Although ω-conotoxins demonstrate analgesic efficacy in animal models of neuropathic pain and in human clinical trials, there remains a critical need to improve the convenience of peptide drug delivery methods, and reduce the number and severity of adverse effects associated with ω-conotoxin-based therapies.
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Affiliation(s)
- Heidi E Hannon
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI 48824, USA.
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70
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Adams DJ, Berecki G. Mechanisms of conotoxin inhibition of N-type (Ca(v)2.2) calcium channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1619-28. [PMID: 23380425 DOI: 10.1016/j.bbamem.2013.01.019] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 01/16/2013] [Accepted: 01/19/2013] [Indexed: 12/27/2022]
Abstract
N-type (Ca(v)2.2) voltage-gated calcium channels (VGCC) transduce electrical activity into other cellular functions, regulate calcium homeostasis and play a major role in processing pain information. Although the distribution and function of these channels vary widely among different classes of neurons, they are predominantly expressed in nerve terminals, where they control neurotransmitter release. To date, genetic and pharmacological studies have identified that high-threshold, N-type VGCCs are important for pain sensation in disease models. This suggests that N-type VGCC inhibitors or modulators could be developed into useful drugs to treat neuropathic pain. This review discusses the role of N-type (Ca(v)2.2) VGCCs in nociception and pain transmission through primary sensory dorsal root ganglion (DRG) neurons (nociceptors). It also outlines the potent and selective inhibition of N-type VGCCs by conotoxins, small disulfide-rich peptides isolated from the venom of marine cone snails. Of these conotoxins, ω-conotoxins are selective N-type VGCC antagonists that preferentially block nociception in inflammatory pain models, and allodynia and/or hyperalgesia in neuropathic pain models. Another conotoxin family, α-conotoxins, were initially proposed as competitive antagonists of muscle and neuronal nicotinic acetylcholine receptors (nAChR). Surprisingly, however, α-conotoxins Vc1.1 and RgIA, also potently inhibit N-type VGCC currents in the sensory DRG neurons of rodents and α9 nAChR knockout mice, via intracellular signaling mediated by G protein-coupled GABAB receptors. Understanding how conotoxins inhibit VGCCs is critical for developing these peptides into analgesics and may result in better pain management. This article is part of a Special Issue entitled: Calcium channels.
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Affiliation(s)
- David J Adams
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria, Australia.
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71
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Differential ubiquitination and proteasome regulation of Ca(V)2.2 N-type channel splice isoforms. J Neurosci 2012; 32:10365-9. [PMID: 22836269 DOI: 10.1523/jneurosci.0851-11.2012] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Ca(V)2.2 (N-type) calcium channels control the entry of calcium into neurons to regulate essential functions but most notably presynaptic transmitter release. Ca(V)2.2 channel expression levels are precisely controlled, but we know little of the cellular mechanisms involved. The ubiquitin proteasome system (UPS) is known to regulate expression of many synaptic proteins, including presynaptic elements, to optimize synaptic efficiency. However, we have limited information about ubiquitination of Ca(V)2 channels. Here we show that Ca(V)2.2 proteins are ubiquitinated, and that elements in the proximal C terminus of Ca(V)2.2 encoded by exon 37b of the mouse Cacna1b gene predispose cloned and native channels to downregulation by the UPS. Ca(V)2.2 channels containing e37b are expressed throughout the mammalian nervous system, but in some cells, notably nociceptors, sometimes e37a--not e37b--is selected during alternative splicing of Ca(V)2.2 pre-mRNA. By a combination of biochemical and functional analyses we show e37b promotes a form of ubiquitination that is coupled to reduced Ca(V)2.2 current density and increased sensitivity to the UPS. Cell-specific alternative splicing of e37a in nociceptors reduces Ca(V)2.2 channel ubiquitination and sensitivity to the UPS, suggesting a role in pain processing.
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72
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Zamponi GW, Currie KPM. Regulation of Ca(V)2 calcium channels by G protein coupled receptors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1629-43. [PMID: 23063655 DOI: 10.1016/j.bbamem.2012.10.004] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 10/02/2012] [Accepted: 10/04/2012] [Indexed: 12/29/2022]
Abstract
Voltage gated calcium channels (Ca²⁺ channels) are key mediators of depolarization induced calcium influx into excitable cells, and thereby play pivotal roles in a wide array of physiological responses. This review focuses on the inhibition of Ca(V)2 (N- and P/Q-type) Ca²⁺-channels by G protein coupled receptors (GPCRs), which exerts important autocrine/paracrine control over synaptic transmission and neuroendocrine secretion. Voltage-dependent inhibition is the most widespread mechanism, and involves direct binding of the G protein βγ dimer (Gβγ) to the α1 subunit of Ca(V)2 channels. GPCRs can also recruit several other distinct mechanisms including phosphorylation, lipid signaling pathways, and channel trafficking that result in voltage-independent inhibition. Current knowledge of Gβγ-mediated inhibition is reviewed, including the molecular interactions involved, determinants of voltage-dependence, and crosstalk with other cell signaling pathways. A summary of recent developments in understanding the voltage-independent mechanisms prominent in sympathetic and sensory neurons is also included. This article is part of a Special Issue entitled: Calcium channels.
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Affiliation(s)
- Gerald W Zamponi
- Department of Physiology & Pharmacology, Hotchkiss Brain Institute, University of Calgary, Canada
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73
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Alternative splicing: functional diversity among voltage-gated calcium channels and behavioral consequences. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1522-9. [PMID: 23022282 DOI: 10.1016/j.bbamem.2012.09.018] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 09/15/2012] [Accepted: 09/19/2012] [Indexed: 12/14/2022]
Abstract
Neuronal voltage-gated calcium channels generate rapid, transient intracellular calcium signals in response to membrane depolarization. Neuronal Ca(V) channels regulate a range of cellular functions and are implicated in a variety of neurological and psychiatric diseases including epilepsy, Parkinson's disease, chronic pain, schizophrenia, and bipolar disorder. Each mammalian Cacna1 gene has the potential to generate tens to thousands of Ca(V) channels by alternative pre-mRNA splicing, a process that adds fine granulation to the pool of Ca(V) channel structures and functions. The precise composition of Ca(V) channel splice isoform mRNAs expressed in each cell are controlled by cell-specific splicing factors. The activity of splicing factors are in turn regulated by molecules that encode various cellular features, including cell-type, activity, metabolic states, developmental state, and other factors. The cellular and behavioral consequences of individual sites of Ca(V) splice isoforms are being elucidated, as are the cell-specific splicing factors that control splice isoform selection. Altered patterns of alternative splicing of Ca(V) pre-mRNAs can alter behavior in subtle but measurable ways, with the potential to influence drug efficacy and disease severity. This article is part of a Special Issue entitled: Calcium channels.
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74
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Adams DJ, Callaghan B, Berecki G. Analgesic conotoxins: block and G protein-coupled receptor modulation of N-type (Ca(V) 2.2) calcium channels. Br J Pharmacol 2012; 166:486-500. [PMID: 22091786 DOI: 10.1111/j.1476-5381.2011.01781.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Conotoxins (conopeptides) are small disulfide bonded peptides from the venom of marine cone snails. These peptides target a wide variety of membrane receptors, ion channels and transporters, and have enormous potential for a range of pharmaceutical applications. Structurally related ω-conotoxins bind directly to and selectively inhibit neuronal (N)-type voltage-gated calcium channels (VGCCs) of nociceptive primary afferent neurones. Among these, ω-conotoxin MVIIA (Prialt) is approved by the Food and Drug Administration (FDA) as an alternative intrathecal analgesic for the management of chronic intractable pain, particularly in patients refractory to opioids. A series of newly discovered ω-conotoxins from Conus catus, including CVID-F, are potent and selective antagonists of N-type VGCCs. In spinal cord slices, these peptides reversibly inhibit excitatory synaptic transmission between primary afferents and dorsal horn superficial lamina neurones, and in the rat partial sciatic nerve ligation model of neuropathic pain, significantly reduce allodynic behaviour. Another family of conotoxins, the α-conotoxins, are competitive antagonists of mammalian nicotinic acetylcholine receptors (nAChRs). α-Conotoxins Vc1.1 and RgIA possess two disulfide bonds and are currently in development as a treatment for neuropathic pain. It was initially proposed that the primary target of these peptides is the α9α10 neuronal nAChR. Surprisingly, however, α-conotoxins Vc1.1, RgIA and PeIA more potently inhibit N-type VGCC currents via a GABA(B) GPCR mechanism in rat sensory neurones. This inhibition is largely voltage-independent and involves complex intracellular signalling. Understanding the molecular mechanisms of conotoxin action will lead to new ways to regulate VGCC block and modulation in normal and diseased states of the nervous system.
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Affiliation(s)
- David J Adams
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria, Australia.
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75
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A118G Mu Opioid Receptor polymorphism increases inhibitory effects on CaV2.2 channels. Neurosci Lett 2012; 523:190-4. [PMID: 22796651 DOI: 10.1016/j.neulet.2012.06.074] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 06/21/2012] [Accepted: 06/29/2012] [Indexed: 01/22/2023]
Abstract
Single nucleotide polymorphisms (SNPs) in the human OPRM1 gene result in common variants of Mu Opioid Receptors (hMORs). The A118G SNP occurs at high frequency in certain human populations and produces an aminoacidic substitution: N40D (hMOR-N to hMOR-D) at protein level. N40D is reported to alter pain thresholds and morphine efficacy. hMORs inhibit Ca(V)2.2 channels (N-type currents) at presynaptic nociceptor terminals in dorsal horn, thus reducing calcium influx, transmitter release, and transmission of noxious signals. Nociceptors express different splice isoforms of Ca(V)2.2. Isoforms distinguished by the presence of alternatively spliced exon e37a are of interest because channels containing e37a are particularly enriched in nociceptors. Recent studies showed that Ca(V)2.2e37a is more sensitive to inhibition by Mu Opioid Receptors than the ubiquitous splice variant Ca(V)2.2e37b. Here, we evaluate the effect of hMOR-N and hMOR-D on cloned Ca(V)2.2e37a channels expressed in mammalian cells. We observe that hMOR-D inhibits Ca(V)2.2e37a currents at agonist concentrations 4-fold lower than those needed to inhibit Ca(V)2.2e37a currents by the same degree via hMOR-N. We observe little difference in hMOR-D and hMOR-N inhibition of Ca(V)2.2e37b currents. Our study demonstrates that this common site of OPRM1 polymorphism affects the inhibitory actions of MORs on both major Ca(V)2.2 isoforms expressed in nociceptors.
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76
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Cuny H, de Faoite A, Huynh TG, Yasuda T, Berecki G, Adams DJ. γ-Aminobutyric acid type B (GABAB) receptor expression is needed for inhibition of N-type (Cav2.2) calcium channels by analgesic α-conotoxins. J Biol Chem 2012; 287:23948-57. [PMID: 22613715 DOI: 10.1074/jbc.m112.342998] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
α-Conotoxins Vc1.1 and RgIA are small peptides isolated from the venom of marine cone snails. They have effective anti-nociceptive actions in rat models of neuropathic pain. Pharmacological studies in rodent dorsal root ganglion (DRG) show their analgesic effect is mediated by inhibition of N-type (Ca(v)2.2) calcium channels via a pathway involving γ-aminobutyric acid type B (GABA(B)) receptor. However, there is no direct demonstration that functional GABA(B) receptors are needed for inhibition of the Ca(v)2.2 channel by analgesic α-conotoxins. This study examined the effect of the GABA(B) agonist baclofen and α-conotoxins Vc1.1 and RgIA on calcium channel currents after transient knockdown of the GABA(B) receptor using RNA interference. Isolated rat DRG neurons were transfected with small interfering RNAs (siRNA) targeting GABA(B) subunits R1 and R2. Efficient knockdown of GABA(B) receptor expression at mRNA and protein levels was confirmed by quantitative real time PCR (qRT-PCR) and immunocytochemical analysis, respectively. Whole-cell patch clamp recordings conducted 2-4 days after transfection showed that inhibition of N-type calcium channels in response to baclofen, Vc1.1 and RgIA was significantly reduced in GABA(B) receptor knockdown DRG neurons. In contrast, neurons transfected with a scrambled nontargeting siRNA were indistinguishable from untransfected neurons. In the HEK 293 cell heterologous expression system, Vc1.1 and RgIA inhibition of Ca(v)2.2 channels needed functional expression of both human GABA(B) receptor subunits. Together, these results confirm that GABA(B) receptors must be activated for the modulation of N-type (Ca(v)2.2) calcium channels by analgesic α-conotoxins Vc1.1 and RgIA.
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Affiliation(s)
- Hartmut Cuny
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria 3083, Australia
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77
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Lewis RJ, Dutertre S, Vetter I, Christie MJ. Conus Venom Peptide Pharmacology. Pharmacol Rev 2012; 64:259-98. [DOI: 10.1124/pr.111.005322] [Citation(s) in RCA: 323] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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78
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Simms BA, Zamponi GW. Trafficking and stability of voltage-gated calcium channels. Cell Mol Life Sci 2012; 69:843-56. [PMID: 21964928 PMCID: PMC11115007 DOI: 10.1007/s00018-011-0843-y] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Revised: 09/15/2011] [Accepted: 09/19/2011] [Indexed: 02/07/2023]
Abstract
Voltage-gated calcium channels are important mediators of calcium influx into electrically excitable cells. The amount of calcium entering through this family of channel proteins is not only determined by the functional properties of channels embedded in the plasma membrane but also by the numbers of channels that are expressed at the cell surface. The trafficking of channels is controlled by numerous processes, including co-assembly with ancillary calcium channel subunits, ubiquitin ligases, and interactions with other membrane proteins such as G protein coupled receptors. Here we provide an overview about the current state of knowledge of calcium channel trafficking to the cell membrane, and of the mechanisms regulating the stability and internalization of this important ion channel family.
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Affiliation(s)
- Brett A. Simms
- Department of Physiology and Pharmacology, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1 Canada
| | - Gerald W. Zamponi
- Department of Physiology and Pharmacology, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1 Canada
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79
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Asynchronous Ca2+ current conducted by voltage-gated Ca2+ (CaV)-2.1 and CaV2.2 channels and its implications for asynchronous neurotransmitter release. Proc Natl Acad Sci U S A 2012; 109:E452-60. [PMID: 22308469 DOI: 10.1073/pnas.1121103109] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We have identified an asynchronously activated Ca(2+) current through voltage-gated Ca(2+) (Ca(V))-2.1 and Ca(V)2.2 channels, which conduct P/Q- and N-type Ca(2+) currents that initiate neurotransmitter release. In nonneuronal cells expressing Ca(V)2.1 or Ca(V)2.2 channels and in hippocampal neurons, prolonged Ca(2+) entry activates a Ca(2+) current, I(Async), which is observed on repolarization and decays slowly with a half-time of 150-300 ms. I(Async) is not observed after L-type Ca(2+) currents of similar size conducted by Ca(V)1.2 channels. I(Async) is Ca(2+)-selective, and it is unaffected by changes in Na(+), K(+), Cl(-), or H(+) or by inhibitors of a broad range of ion channels. During trains of repetitive depolarizations, I(Async) increases in a pulse-wise manner, providing Ca(2+) entry that persists between depolarizations. In single-cultured hippocampal neurons, trains of depolarizations evoke excitatory postsynaptic currents that show facilitation followed by depression accompanied by asynchronous postsynaptic currents that increase steadily during the train in parallel with I(Async). I(Async) is much larger for slowly inactivating Ca(V)2.1 channels containing β(2a)-subunits than for rapidly inactivating channels containing β(1b)-subunits. I(Async) requires global rises in intracellular Ca(2+), because it is blocked when Ca(2+) is chelated by 10 mM EGTA in the patch pipette. Neither mutations that prevent Ca(2+) binding to calmodulin nor mutations that prevent calmodulin regulation of Ca(V)2.1 block I(Async). The rise of I(Async) during trains of stimuli, its decay after repolarization, its dependence on global increases of Ca(2+), and its enhancement by β(2a)-subunits all resemble asynchronous release, suggesting that I(Async) is a Ca(2+) source for asynchronous neurotransmission.
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80
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Glatt SJ, Cohen OS, Faraone SV, Tsuang MT. Dysfunctional gene splicing as a potential contributor to neuropsychiatric disorders. Am J Med Genet B Neuropsychiatr Genet 2011; 156B:382-92. [PMID: 21438146 PMCID: PMC3082621 DOI: 10.1002/ajmg.b.31181] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Accepted: 02/18/2011] [Indexed: 12/31/2022]
Abstract
Alternative pre-mRNA splicing is a major mechanism by which the proteomic diversity of eukaryotic genomes is amplified. Much akin to neuropsychiatric disorders themselves, alternative splicing events can be influenced by genetic, developmental, and environmental factors. Here, we review the evidence that abnormalities of splicing may contribute to the liability toward these disorders. First, we introduce the phenomenon of alternative splicing and describe the processes involved in its regulation. We then review the evidence for specific splicing abnormalities in a wide range of neuropsychiatric disorders, including psychotic disorders (schizophrenia), affective disorders (bipolar disorder and major depressive disorder), suicide, substance abuse disorders (cocaine abuse and alcoholism), and neurodevelopmental disorders (autism). Next, we provide a theoretical reworking of the concept of "gene-focused" epidemiologic and neurobiologic investigations. Lastly, we suggest potentially fruitful lines for future research that should illuminate the nature, extent, causes, and consequences of alternative splicing abnormalities in neuropsychiatric disorders.
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Affiliation(s)
- Stephen J. Glatt
- Psychiatric Genetic Epidemiology & Neurobiology Laboratory (PsychGENe Lab); Departments of Psychiatry and Behavioral Sciences & Neuroscience and Physiology; Medical Genetics Research Center; SUNY Upstate Medical University; Syracuse, NY 13210; U.S.A,To whom correspondence should be addressed: SUNY Upstate Medical University, 750 East Adams Street, Weiskotten Hall, Room 3283, Syracuse, NY 13210, U.S.A., , Facsimile: (315) 464-7744, Telephone: (315) 464-7742
| | - Ori S. Cohen
- Psychiatric Genetic Epidemiology & Neurobiology Laboratory (PsychGENe Lab); Departments of Psychiatry and Behavioral Sciences & Neuroscience and Physiology; Medical Genetics Research Center; SUNY Upstate Medical University; Syracuse, NY 13210; U.S.A
| | - Stephen V. Faraone
- Psychiatric Genetic Epidemiology & Neurobiology Laboratory (PsychGENe Lab); Departments of Psychiatry and Behavioral Sciences & Neuroscience and Physiology; Medical Genetics Research Center; SUNY Upstate Medical University; Syracuse, NY 13210; U.S.A
| | - Ming T. Tsuang
- Center for Behavioral Genomics; Department of Psychiatry; Institute of Genomic Medicine; University of California, San Diego; 9500 Gilman Drive; La Jolla, CA 92039; U.S.A, Veterans Affairs San Diego Healthcare System; 3350 La Jolla Village Drive; San Diego, CA 92161; U.S.A, Harvard Institute of Psychiatric Epidemiology and Genetics; Harvard Departments of Epidemiology and Psychiatry; 25 Shattuck Street; Boston, MA 02115; U.S.A
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81
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Franck MCM, Stenqvist A, Li L, Hao J, Usoskin D, Xu X, Wiesenfeld-Hallin Z, Ernfors P. Essential role of Ret for defining non-peptidergic nociceptor phenotypes and functions in the adult mouse. Eur J Neurosci 2011; 33:1385-400. [DOI: 10.1111/j.1460-9568.2011.07634.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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82
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Spehr J, Gelis L, Osterloh M, Oberland S, Hatt H, Spehr M, Neuhaus EM. G protein-coupled receptor signaling via Src kinase induces endogenous human transient receptor potential vanilloid type 6 (TRPV6) channel activation. J Biol Chem 2011; 286:13184-92. [PMID: 21349844 DOI: 10.1074/jbc.m110.183525] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+) homeostasis plays a critical role in a variety of cellular processes. We showed previously that stimulation of the prostate-specific G protein-coupled receptor (PSGR) enhances cytosolic Ca(2+) and inhibits proliferation of prostate cells. Here, we analyzed the signaling mechanisms underlying the PSGR-mediated Ca(2+) increase. Using complementary molecular, biochemical, electrophysiological, and live-cell imaging techniques, we found that endogenous Ca(2+)-selective transient receptor potential vanilloid type 6 (TRPV6) channels are critically involved in the PSGR-induced Ca(2+) signal. Biophysical characterization of the current activated by PSGR stimulation revealed characteristic properties of TRPV6. The molecular identity of the involved channel was confirmed using RNA interference targeting TrpV6. TRPV6-mediated Ca(2+) influx depended on Src kinase activity. Src kinase activation occurred independently of G protein activation, presumably by direct interaction with PSGR. Taken together, we report that endogenous TRPV6 channels are activated downstream of a G protein-coupled receptor and present the first physiological characterization of these channels in situ.
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Affiliation(s)
- Jennifer Spehr
- Department of Chemosensation, RTWH Aachen University, 52074 Aachen, Germany.
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83
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Weiss N, Sandoval A, Kyonaka S, Felix R, Mori Y, De Waard M. Rim1 modulates direct G-protein regulation of Ca(v)2.2 channels. Pflugers Arch 2011; 461:447-59. [PMID: 21331761 DOI: 10.1007/s00424-011-0926-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 01/13/2011] [Accepted: 01/13/2011] [Indexed: 11/29/2022]
Abstract
Regulation of presynaptic voltage-gated calcium channels is critical for depolarization-evoked neurotransmitter release. Various studies attempted to determine the functional implication of Rim1, a component of the vesicle release machinery. Besides to couple voltage-gated Ca(2+) channels to the presynaptic vesicle release machinery, it was evidenced that Rim1 also prevents voltage-dependent inactivation of the channels through a direct interaction with the ancillary β-subunits, thus facilitating neurotransmitter release. However, facilitation of synaptic activity may also be caused by a reduction of the inhibitory pathway carried by G-protein-coupled receptors. Here, we explored the functional implication of Rim1 in G-protein regulation of Ca(v)2.2 channels. Activation of μ-opioid receptors expressed in HEK-293 cells along with Ca(v)2.2 channels produced a drastic current inhibition both in control and Rim1-expressing cells. In contrast, Rim1 considerably promoted the extent of current deinhibition following channel activation, favoring sustained Ca(2+) influx under prolonged activity. Our data suggest that Rim1-induced facilitation of neurotransmitter release may come as a consequence of a decrease in the inhibitory pathway carried by G-proteins that contributes, together with the slowing of channel inactivation, to maintain Ca(2+) influx under prolonged activity. The present study also furthers functional insights in the importance of proteins from the presynaptic vesicle complex in the regulation of voltage-gated Ca(2+) channels by G-proteins.
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Affiliation(s)
- Norbert Weiss
- Laboratory of Ion Channels, Functions and Pathologies, Grenoble Institute of Neurosciences, INSERM U836, Grenoble, France.
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84
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Abstract
Voltage-gated Ca(2+) channels translate the electrical inputs of excitable cells into biochemical outputs by controlling influx of the ubiquitous second messenger Ca(2+) . As such the channels play pivotal roles in many cellular functions including the triggering of neurotransmitter and hormone release by CaV2.1 (P/Q-type) and CaV2.2 (N-type) channels. It is well established that G protein coupled receptors (GPCRs) orchestrate precise regulation neurotransmitter and hormone release through inhibition of CaV2 channels. Although the GPCRs recruit a number of different pathways, perhaps the most prominent, and certainly most studied among these is the so-called voltage-dependent inhibition mediated by direct binding of Gβγ to the α1 subunit of CaV2 channels. This article will review the basics of Ca(2+) -channels and G protein signaling, and the functional impact of this now classical inhibitory mechanism on channel function. It will also provide an update on more recent developments in the field, both related to functional effects and crosstalk with other signaling pathways, and advances made toward understanding the molecular interactions that underlie binding of Gβγ to the channel and the voltage-dependence that is a signature characteristic of this mechanism.
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Affiliation(s)
- Kevin P M Currie
- Department of Anesthesiology, Pharmacology and Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, TN, USA.
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85
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Abstract
Voltage-gated calcium channels (VGCC) play obligatory physiological roles, including modulation of neuronal: functions, synaptic plasticity, neurotransmitter release and gene transcription. Dysregulation and maladaptive changes in VGCC expression and activities may occur in the sensory pathway under various pathological conditions that could contribute to the development of pain. In this review, we summarized the most recent findings on the regulation of VGCC expression and physiological functions in the sensory pathway, and in dysregulation and maladaptive changes of VGCC under pain-inducing conditions. The implications of: these changes in understanding the mechanisms of pain transduction and in new drug design are also discussed.
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Affiliation(s)
- John Park
- Department of Pharmacology, University of California-Irvine School of Medicine, Irvine, CA, USA
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86
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Allen SE, Darnell RB, Lipscombe D. The neuronal splicing factor Nova controls alternative splicing in N-type and P-type CaV2 calcium channels. Channels (Austin) 2010; 4:483-9. [PMID: 21150296 DOI: 10.4161/chan.4.6.12868] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Many cellular processes are involved in optimizing protein function for specific neuronal tasks; here we focus on alternative pre-mRNA splicing. Alternative pre-mRNA splicing gives cells the capacity to modify and selectively re-balance their existing pool of transcripts in a coordinated way across multiple mRNAs, thereby effecting relatively rapid and relatively stable changes in protein activity. Here we report on and discuss the coordinated regulation of two sites of alternative splicing, e24a and e31a, in P-type CaV2.1 and N-type CaV2.2 channels. These two exons encode 4 and 2 amino acids, respectively, in the extracellular linker regions between transmembrane spanning segments S3 and S4 in domains III and IV of each CaV2 subunit. Recent genome-wide screens of splicing factor-RNA binding events by Darnell and colleagues show that Nova-2 promotes inclusion of e24a in CaV2.2 mRNAs in brain. We review these studies and show that a homologous e24a is present in theCaV2 .1 gene, Cacna1a, and that it is expressed in different regions of the nervous system. Nova-2 enhances inclusion of e24a but represses e31a inclusion in CaV2.1 and CaV2.2 mRNAs in brain. It is likely that coordinated alternative pre-mRNA splicing across related CaV2 genes by common splicing factors, allows neurons to orchestrate changes in synaptic protein function while maintaining a balanced and functioning system.
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Affiliation(s)
- Summer E Allen
- Department of Neuroscience, Brown University, Providence, RI, USA
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87
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Opioid inhibition of N-type Ca2+ channels and spinal analgesia couple to alternative splicing. Nat Neurosci 2010; 13:1249-56. [PMID: 20852623 PMCID: PMC2956429 DOI: 10.1038/nn.2643] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 08/23/2010] [Indexed: 12/16/2022]
Abstract
Alternative pre-mRNA splicing predominates in the nervous systems of complex organisms including humans dramatically expanding the potential size of the proteome. Cell-specific alternative pre-mRNA splicing is thought to optimize protein function for specialized cellular tasks, but direct evidence for this is limited. Transmission of noxious thermal stimuli relies on the activity of N-type CaV2.2 calcium channels in nociceptors. Using an exon replacement strategy in mice, we show that mutually exclusive splicing in the CaV2.2 gene modulates N-type channel function in nociceptors leading to a change in morphine analgesia. Exon 37a enhances μ-opioid receptor mediated inhibition of N-type calcium channels by promoting activity-independent inhibition. In the absence of e37a spinal morphine analgesia is weakened in vivo without influencing the basal response to noxious thermal stimuli. Our data suggest that highly specialized, discrete cellular responsiveness in vivo can be attributed to alternative splicing events regulated at the level of individual neurons.
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88
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Huang X, Senatore A, Dawson TF, Quan Q, Spafford JD. G-proteins modulate invertebrate synaptic calcium channel (LCav2) differently from the classical voltage-dependent regulation of mammalian Cav2.1 and Cav2.2 channels. ACTA ACUST UNITED AC 2010; 213:2094-103. [PMID: 20511524 DOI: 10.1242/jeb.042242] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Voltage-gated calcium channels in the Ca(v)2 channel class are regulators of synaptic transmission and are highly modified by transmitter inputs that activate synaptic G-protein-coupled receptors (GPCRs). A ubiquitous form of G-protein modulation involves an inhibition of mammalian Ca(v)2.1 and Ca(v)2.2 channels by Gbetagamma dimers that can be relieved by high-frequency trains of action potentials. Here, we address whether the ubiquitous and versatile form of G-protein regulation in mammals is also found in simpler invertebrate nervous systems. Remarkably, the invertebrate LCa(v)2 channel from the pond snail, Lymnaea stagnalis, does not bear any of the hallmarks of mammalian, voltage-dependent G-protein inhibition of Ca(v)2.2. Swapping either the I-II linker or N-terminus of Ca(v)2.2, which serve as key binding domains for G-protein inhibition, does not endow invertebrate LCa(v)2 channels with voltage-dependent G-protein modulatory capacity. Instead, in vitro expressed LCa(v)2 channels are inhibited slowly by the activation of cAMP, in a manner that depends on G-proteins but does not depend on Gbetagamma subunits. A similar G-protein and cAMP-dependent inhibition of nifedipine-insensitive LCa(v)2 currents is also consistent in native and identified Lymnaea VD4 neurons. The slower inhibition using a cellular messenger such as cAMP may meet the modulatory needs in invertebrates while an activity-dependent regulation, evolving in vertebrates, provides a more dynamic, fine-tuning of neurosecretion by regulating the influence of neurotransmitter inputs through presynaptic GPCRs.
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Affiliation(s)
- Xuan Huang
- Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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89
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Suh BC, Leal K, Hille B. Modulation of high-voltage activated Ca(2+) channels by membrane phosphatidylinositol 4,5-bisphosphate. Neuron 2010; 67:224-38. [PMID: 20670831 DOI: 10.1016/j.neuron.2010.07.001] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/30/2010] [Indexed: 12/23/2022]
Abstract
Modulation of voltage-gated Ca(2+) channels controls activities of excitable cells. We show that high-voltage activated Ca(2+) channels are regulated by membrane phosphatidylinositol 4,5-bisphosphate (PIP(2)) with different sensitivities. Plasma membrane PIP(2) depletion by rapamycin-induced translocation of an inositol lipid 5-phosphatase or by a voltage-sensitive 5-phosphatase (VSP) suppresses Ca(V)1.2 and Ca(V)1.3 channel currents by approximately 35% and Ca(V)2.1 and Ca(V)2.2 currents by 29% and 55%, respectively. Other Ca(V) channels are less sensitive. Inhibition is not relieved by strong depolarizing prepulses. It changes the voltage dependence of channel gating little. Recovery of currents from inhibition needs intracellular hydrolysable ATP, presumably for PIP(2) resynthesis. When PIP(2) is increased by overexpressing PIP 5-kinase, activation and inactivation of Ca(V)2.2 current slow and voltage-dependent gating shifts to slightly higher voltages. Thus, endogenous membrane PIP(2) supports high-voltage activated L-, N-, and P/Q-type Ca(2+) channels, and stimuli that activate phospholipase C deplete PIP(2) and reduce those Ca(2+) channel currents.
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Affiliation(s)
- Byung-Chang Suh
- Department of Physiology and Biophysics, The University of Washington School of Medicine, Seattle, WA 98195-7290, USA.
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90
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Zhang G, Chen W, Marvizón JCG. Src family kinases mediate the inhibition of substance P release in the rat spinal cord by μ-opioid receptors and GABA(B) receptors, but not α2 adrenergic receptors. Eur J Neurosci 2010; 32:963-73. [PMID: 20726886 DOI: 10.1111/j.1460-9568.2010.07335.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
GABA(B) , μ-opioid and adrenergic α(2) receptors inhibit substance P release from primary afferent terminals in the dorsal horn. Studies in cell expression systems suggest that μ-opioid and GABA(B) receptors inhibit transmitter release from primary afferents by activating Src family kinases (SFKs), which then phosphorylate and inhibit voltage-gated calcium channels. This study investigated whether SFKs mediate the inhibition of substance P release by these three receptors. Substance P release was measured as neurokinin 1 receptor (NK1R) internalization in spinal cord slices and in vivo. In slices, NK1R internalization induced by high-frequency dorsal root stimulation was inhibited by the μ-opioid agonist DAMGO and the GABA(B) agonist baclofen. This inhibition was reversed by the SFK inhibitor PP1. NK1R internalization induced by low-frequency stimulation was also inhibited by DAMGO, but PP1 did not reverse this effect. In vivo, NK1R internalization induced by noxious mechanical stimulation of the hind paw was inhibited by intrathecal DAMGO and baclofen. This inhibition was reversed by intrathecal PP1, but not by the inactive PP1 analog PP3. PP1 produced no effect by itself. The α(2) adrenergic agonists medetomidine and guanfacine produced a small but statistically significant inhibition of NK1R internalization induced by low-frequency dorsal root stimulation. PP1 did not reverse the inhibition by guanfacine. These results show that SFKs mediate the inhibition of substance P release by μ-opioid and GABA(B) receptors, but not by α(2) receptors, which is probably mediated by the binding of G protein βγ subunits to calcium channels.
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Affiliation(s)
- Guohua Zhang
- Center for Neurobiology of Stress, CURE: Digestive Diseases Research Center, Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA, USA
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91
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Abstract
Motor neurons are large, highly polarised cells with very long axons and a requirement for precise spatial and temporal gene expression. Neurodegenerative disorders characterised by selective motor neuron vulnerability include various forms of amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). A rapid expansion in knowledge on the pathophysiology of motor neuron degeneration has occurred in recent years, largely through the identification of genes leading to familial forms of ALS and SMA. The major emerging theme is that motor neuron degeneration can result from mutation in genes that encode factors important for ribonucleoprotein biogenesis and RNA processing, including splicing regulation, transcript stabilisation, translational repression and localisation of mRNA. Complete understanding of how these pathways interact and elucidation of specialised mechanisms for mRNA targeting and processing in motor neurons are likely to produce new targets for therapy in ALS and related disorders.
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92
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C-terminal deletion of metabotropic glutamate receptor 1 selectively abolishes coupling to Gαq. Eur J Pharmacol 2010; 627:63-8. [DOI: 10.1016/j.ejphar.2009.10.051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Revised: 10/06/2009] [Accepted: 10/26/2009] [Indexed: 11/23/2022]
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93
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Striessnig J. An oily competition: role of beta subunit palmitoylation for Ca2+ channel modulation by fatty acids. ACTA ACUST UNITED AC 2010; 134:363-7. [PMID: 19858356 PMCID: PMC2768802 DOI: 10.1085/jgp.200910330] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Jörg Striessnig
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria.
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94
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Zhang G, Chen W, Lao L, Marvizón JCG. Cannabinoid CB1 receptor facilitation of substance P release in the rat spinal cord, measured as neurokinin 1 receptor internalization. Eur J Neurosci 2010; 31:225-37. [PMID: 20074214 DOI: 10.1111/j.1460-9568.2009.07075.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The contribution of CB1 receptors in the spinal cord to cannabinoid analgesia is still unclear. The objective of this study was to investigate the effect of CB1 receptors on substance P release from primary afferent terminals in the spinal cord. Substance P release was measured as neurokinin 1 (NK1) receptor internalization in lamina I neurons. It was induced in spinal cord slices by dorsal root stimulation and in live rats by a noxious stimulus. In spinal cord slices, the CB1 receptor antagonists AM251, AM281 and rimonabant partially but potently inhibited NK1 receptor internalization induced by electrical stimulation of the dorsal root. This was due to an inhibition of substance P release and not of NK1 receptor internalization itself, because AM251 and AM281 did not inhibit NK1 receptor internalization induced by exogenous substance P. The CB1 receptor agonist ACEA increased NK1 receptor internalization evoked by dorsal root stimulation. The effects of AM251 and ACEA cancelled each other. In vivo, AM251 injected intrathecally decreased NK1 receptor internalization in spinal segments L5 and L6 induced by noxious hind paw clamp. Intrathecal AM251 also produced analgesia to radiant heat stimulation of the paw. The inhibition by AM251 of NK1 receptor internalization was reversed by antagonists of mu-opioid and GABA(B) receptors. This indicates that CB1 receptors facilitate substance P release by inhibiting the release of GABA and opioids next to primary afferent terminals, producing disinhibition. This results in a pronociceptive effect of CB1 receptors in the spinal cord.
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Affiliation(s)
- Guohua Zhang
- Veteran Affairs Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA
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95
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Chen W, Zhang G, Marvizón JCG. NMDA receptors in primary afferents require phosphorylation by Src family kinases to induce substance P release in the rat spinal cord. Neuroscience 2010; 166:924-34. [PMID: 20074620 DOI: 10.1016/j.neuroscience.2010.01.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 12/16/2009] [Accepted: 01/06/2010] [Indexed: 01/11/2023]
Abstract
The function of N-methyl-d-aspartate (NMDA) receptors in primary afferents remains controversial, in particular regarding their ability to evoke substance P release in the spinal cord. The objective of this study was, first, to confirm that substance P release evoked by NMDA is mediated by NMDA receptors in primary afferent terminals. Second, we investigated whether these NMDA receptors are inactivated in some conditions, which would explain why their effect on substance P release was not observed in some studies. Substance P release was induced in spinal cord slices and measured as neurokinin 1 (NK1) receptor internalization in lamina I neurons. NMDA (combined with d-serine) induced NK1 receptor internalization with a half of the effective concentration (EC50) of 258 nM. NMDA-induced NK1 receptor internalization was abolished by the NK1 receptor antagonist L-703,606, confirming that is was caused by substance P release, by NMDA receptor antagonists (MK1801 and ifenprodil), showing that it was mediated by NMDA receptors containing the NR2B subunit, and by preincubating the slices with capsaicin, showing that the substance P release was from primary afferents. However, it was not affected by lidocaine and omega-conotoxin MVIIA, which block Na+ channels and voltage-dependent Ca2+ channels, respectively. Therefore, NMDA-induced substance P release does not require firing of primary afferents or the opening of Ca2+ channels, which is consistent with the idea that NMDA receptors induce substance P directly by letting Ca2+ into primary afferent terminals. Importantly, NMDA-induced substance P release was eliminated by preincubating the slices for 1 h with the Src family kinase inhibitors PP1 and dasatinib, and was substantially increased by the protein tyrosine phosphatase inhibitor BVT948. In contrast, PP1 did not affect NK1 receptor internalization induced by capsaicin. These results show that tyrosine-phosphorylation of these NMDA receptors is regulated by the opposite actions of Src family kinases and protein tyrosine phosphatases, and is required to induce substance P release.
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Affiliation(s)
- W Chen
- Center for Neurobiology of Stress, CURE: Digestive Diseases Research Center, Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine at the University of California, Los Angeles, Los Angeles, CA, USA
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96
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McIntosh JM, Absalom N, Chebib M, Elgoyhen AB, Vincler M. Alpha9 nicotinic acetylcholine receptors and the treatment of pain. Biochem Pharmacol 2009; 78:693-702. [PMID: 19477168 PMCID: PMC2739401 DOI: 10.1016/j.bcp.2009.05.020] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 05/15/2009] [Accepted: 05/18/2009] [Indexed: 01/16/2023]
Abstract
Chronic pain is a vexing worldwide problem that causes substantial disability and consumes significant medical resources. Although there are numerous analgesic medications, these work through a small set of molecular mechanisms. Even when these medications are used in combination, substantial amounts of pain often remain. It is therefore highly desirable to develop treatments that work through distinct mechanisms of action. While agonists of nicotinic acetylcholine receptors (nAChRs) have been intensively studied, new data suggest a role for selective antagonists of nAChRs. alpha-Conotoxins are small peptides used offensively by carnivorous marine snails known as Conus. A subset of these peptides known as alpha-conotoxins RgIA and Vc1.1 produces both acute and long lasting analgesia. In addition, these peptides appear to accelerate the recovery of function after nerve injury, possibly through immune mediated mechanisms. Pharmacological analysis indicates that RgIA and Vc1.1 are selective antagonists of alpha9alpha10 nAChRs. A recent study also reported that these alpha9alpha10 antagonists are also potent GABA-B agonists. In the current study, we were unable to detect RgIA or Vc1.1 binding to or action on cloned GABA-B receptors expressed in HEK cells or Xenopus oocytes. We review the background, findings and implications of use of compounds that act on alpha9* nAChRs.(1).
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Affiliation(s)
- J Michael McIntosh
- Department of Psychiatry, University of Utah, Salt Lake City, UT 84132, USA.
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97
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Lee JA, Tang ZZ, Black DL. An inducible change in Fox-1/A2BP1 splicing modulates the alternative splicing of downstream neuronal target exons. Genes Dev 2009; 23:2284-93. [PMID: 19762510 DOI: 10.1101/gad.1837009] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Neuronal depolarization and CaM kinase IV signaling alter the splicing of multiple exons in transcripts for ion channels, neurotransmitter receptors, and other synaptic proteins. These splicing changes are mediated in part by special CaM kinase-responsive RNA elements, within or adjacent to exons that are repressed in the initial phase of chronic depolarization. The splicing of many neuronal transcripts is also regulated by members of the Fox (Feminizing gene on X) protein family, and these Fox targets are also often proteins affecting synaptic activity. We show that Fox-1/Ataxin 2-Binding Protein 1 (A2BP1), a protein implicated in a variety of neurological diseases, can counteract the effects of chronic depolarization on splicing. We find that exon 19 of Fox-1 is itself repressed by depolarization. Fox-1 transcripts missing exon 19 encode a nuclear isoform of Fox-1 that progressively replaces the cytoplasmic Fox-1 isoform as cells are maintained depolarizing media. The resulting increase in nuclear Fox-1 leads to the reactivation of many Fox-1 target exons, including exon 5 of the NMDA receptor 1, that were initially repressed by the high-KCl medium. These results reveal a novel mechanism for the slow modulation of splicing as cells adapt to chronic stimuli: The subcellular localization of a splicing regulator is controlled through its own alternative splicing.
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Affiliation(s)
- Ji-Ann Lee
- Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
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98
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Jakubek LM, Marangoudakis S, Raingo J, Liu X, Lipscombe D, Hurt RH. The inhibition of neuronal calcium ion channels by trace levels of yttrium released from carbon nanotubes. Biomaterials 2009; 30:6351-7. [PMID: 19698989 DOI: 10.1016/j.biomaterials.2009.08.009] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Accepted: 08/05/2009] [Indexed: 11/28/2022]
Abstract
Carbon nanotubes (CNTs) are used with increasing frequency in neuroengineering applications. CNT scaffolds are used to transmit electrical stimulation to cultured neurons and to control outgrowth and branching patterns of neurites. CNTs have been reported to disrupt normal neuronal function including alterations in endocytotic capability and inhibition of ion channels. Calcium ion channels regulate numerous neuronal and cellular functions including endo and exocytosis, neurite outgrowth, and gene expression. Strong CNT interactions with neuronal calcium ion channels would have profound biological implications. Here we show that physiological solutions containing CNTs inhibit neuronal voltage-gated calcium ion channels in a dose-dependent and CNT sample-dependent manner with IC50 as low as 1.2 microg/ml. Importantly, we demonstrate that the inhibitory activity does not involve tubular graphene as previously reported, but rather very low concentrations of soluble yttrium released from the nanotube growth catalyst. Cationic yttrium potently inhibits calcium ion channel function with an inhibitory efficacy, IC50, of 0.07 ppm w/w. Because of this potency, unpurified and even some reportedly "purified" CNT samples contain sufficient bioavailable yttrium to inhibit channel function. Our results have important implications for emerging nano-neurotechnology and highlight the critical role that trace components can play in the biological response to complex nanomaterials.
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Affiliation(s)
- Lorin M Jakubek
- Division of Engineering, Brown University, Providence, RI 02912, USA
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99
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Fricker D, Dinocourt C, Eugène E, Wood JN, Wood J, Miles R. Pyramidal cells of rodent presubiculum express a tetrodotoxin-insensitive Na+ current. J Physiol 2009; 587:4249-64. [PMID: 19596892 DOI: 10.1113/jphysiol.2009.175349] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Presubicular neurons are activated physiologically by a specific preferred head direction. Here we show that firing in these neurones is characterized by action potentials with a large overshoot and a reduced firing frequency adaptation during repetitive firing. We found that a component of the sodium current of presubicular cells was not abolished by tetrodotoxin (TTX, 10 mum) and was activated at more depolarized voltages than TTX-sensitive currents. This inward current was completely abolished by the removal of external sodium, suggesting that sodium is the charge carrier of this TTX-insensitive (TTX-I) current. The channels responsible for the TTX-I sodium current seemed to be expressed at sites distant from the soma, giving rise to a voltage-dependent delay in current activation. The voltage required for half-maximal activation was 21 mV, and 36 mV for inactivation, which is similar to that reported for Na(V)1.8 sodium channels. However, the kinetics were considerably slower, with a time constant of current decay of 1.4 s. The current was not abolished in pyramidal cells from animals lacking either the Na(V)1.8 or the Na(V)1.9 subunit. This, possibly novel, TTX-I sodium current could contribute to the coding functions of presubicular neurons, specifically the maintained firing associated with signalling of a stable head position.
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Affiliation(s)
- Desdemona Fricker
- CRICM - CNRS UMR7225, CHU Pitié-Salpêtrière, 105 Bd de l'Hôpital, 75013 Paris, France.
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Subcellular neuropharmacology: the importance of intracellular targeting. Trends Pharmacol Sci 2009; 30:203-11. [DOI: 10.1016/j.tips.2009.01.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 01/09/2009] [Accepted: 01/21/2009] [Indexed: 01/03/2023]
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