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Wong E, Anggono V, Williams SR, Degnan SM, Degnan BM. Phototransduction in a marine sponge provides insights into the origin of animal vision. iScience 2022; 25:104436. [PMID: 35707725 PMCID: PMC9189025 DOI: 10.1016/j.isci.2022.104436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 08/22/2021] [Accepted: 05/17/2022] [Indexed: 11/24/2022] Open
Abstract
Most organisms respond to light. Here, we investigate the origin of metazoan phototransduction by comparing well-characterized opsin-based photosystems in neural animals with those in the sponge Amphimedon queenslandica. Although sponges lack neurons and opsins, they can respond rapidly to light. In Amphimedon larvae, this is guided by the light-sensing posterior pigment ring. We first use cell-type-specific transcriptomes to reveal that genes that characterize eumetazoan Gt- and Go-mediated photosystems are enriched in the pigment ring. We then apply a suite of signaling pathway agonists and antagonists to swimming larvae exposed to directional light. These experiments implicate metabotropic glutamate receptors, phospholipase-C, protein kinase C, and voltage-gated calcium channels in larval phototaxis; the inhibition of phospholipase-C, a key transducer of the Gq-mediated pathway, completely reverses phototactic behavior. Together, these results are consistent with aneural sponges sharing with neural metazoans an ancestral set of photosignaling pathways. Amphimedon larvae are negatively phototactic but lack neurons and opsins Sponge larval photosensory cells are enriched in conserved phototransduction genes Conserved photosignaling pathways appear to be controlling larval phototaxis Phototactic behavior is reversed by the inhibition of phospholipase-C
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Affiliation(s)
- Eunice Wong
- School of Biological Sciences, University of Queensland, Brisbane, QLD 4072, Australia
| | - Victor Anggono
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072, Australia.,Clem Jones Centre for Ageing Dementia Research, University of Queensland, Brisbane, QLD 4072, Australia
| | - Stephen R Williams
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072, Australia
| | - Sandie M Degnan
- School of Biological Sciences, University of Queensland, Brisbane, QLD 4072, Australia
| | - Bernard M Degnan
- School of Biological Sciences, University of Queensland, Brisbane, QLD 4072, Australia
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2
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de Hoog E, Spencer GE. Activity-dependent modulation of neuronal K V channels by retinoic acid enhances Ca V channel activity. J Biol Chem 2022; 298:101959. [PMID: 35452677 PMCID: PMC9127218 DOI: 10.1016/j.jbc.2022.101959] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 04/14/2022] [Accepted: 04/17/2022] [Indexed: 12/18/2022] Open
Abstract
The metabolite of vitamin A, retinoic acid (RA), is known to affect synaptic plasticity in the nervous system and to play an important role in learning and memory. A ubiquitous mechanism by which neuronal plasticity develops in the nervous system is through modulation of voltage-gated Ca2+ (CaV) and voltage-gated K+ channels. However, how retinoids might regulate the activity of these channels has not been determined. Here, we show that RA modulates neuronal firing by inducing spike broadening and complex spiking in a dose-dependent manner in peptidergic and dopaminergic cell types. Using patch-clamp electrophysiology, we show that RA-induced complex spiking is activity dependent and involves enhanced inactivation of delayed rectifier voltage-gated K+ channels. The prolonged depolarizations observed during RA-modulated spiking lead to an increase in Ca2+ influx through CaV channels, though we also show an opposing effect of RA on the same neurons to inhibit Ca2+ influx. At physiological levels of Ca2+, this inhibition is specific to CaV2 (not CaV1) channels. Examining the interaction between the spike-modulating effects of RA and its inhibition of CaV channels, we found that inhibition of CaV2 channels limits the Ca2+ influx resulting from spike modulation. Our data thus provide novel evidence to suggest that retinoid signaling affects both delayed rectifier K+ channels and CaV channels to fine-tune Ca2+ influx through CaV2 channels. As these channels play important roles in synaptic function, we propose that these modulatory effects of retinoids likely contribute to synaptic plasticity in the nervous system.
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Affiliation(s)
- Eric de Hoog
- Department of Biological Sciences, Brock University, 1812 Sir Isaac Brock's Way, St Catharines, Ontario. Canada. L2S 3A1
| | - Gaynor E Spencer
- Department of Biological Sciences, Brock University, 1812 Sir Isaac Brock's Way, St Catharines, Ontario. Canada. L2S 3A1.
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3
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Invertebrate neurons as a simple model to study the hyperexcitable state of epileptic disorders in single cells, monosynaptic connections, and polysynaptic circuits. Biophys Rev 2022; 14:553-568. [PMID: 35528035 PMCID: PMC9043075 DOI: 10.1007/s12551-022-00942-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 03/09/2022] [Indexed: 12/17/2022] Open
Abstract
Epilepsy is a neurological disorder characterized by a hyperexcitable state in neurons from different brain regions. Much is unknown about epilepsy and seizures development, depicting a growing field of research. Animal models have provided important clues about the underlying mechanisms of seizure-generating neuronal circuits. Mammalian complexity still makes it difficult to define some principles of nervous system function, and non-mammalian models have played pivotal roles depending on the research question at hand. Mollusks and the Helix land snail have been used to study epileptic-like behavior in neurons. Neurons from these organisms confer advantages as single-cell identification, isolation, and culture, either as single cells or as physiological relevant monosynaptic or polysynaptic circuits, together with amenability to different protocols and treatments. This review's purpose consists in presenting relevant papers in order to gain a better understanding of Helix neurons, their characteristics, uses, and capabilities for studying the fundamental mechanisms of epileptic disorders and their treatment, to facilitate their more expansive use in epilepsy research.
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Gauberg J, Elkhatib W, Smith CL, Singh A, Senatore A. Divergent Ca 2+/calmodulin feedback regulation of Ca V1 and Ca V2 voltage-gated calcium channels evolved in the common ancestor of Placozoa and Bilateria. J Biol Chem 2022; 298:101741. [PMID: 35182524 PMCID: PMC8980814 DOI: 10.1016/j.jbc.2022.101741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 02/10/2022] [Accepted: 02/13/2022] [Indexed: 11/04/2022] Open
Abstract
CaV1 and CaV2 voltage-gated calcium channels evolved from an ancestral CaV1/2 channel via gene duplication somewhere near the stem animal lineage. The divergence of these channel types led to distinguishing functional properties that are conserved among vertebrates and bilaterian invertebrates and contribute to their unique cellular roles. One key difference pertains to their regulation by calmodulin (CaM), wherein bilaterian CaV1 channels are uniquely subject to pronounced, buffer-resistant Ca2+/CaM-dependent inactivation, permitting negative feedback regulation of calcium influx in response to local cytoplasmic Ca2+ rises. Early diverging, nonbilaterian invertebrates also possess CaV1 and CaV2 channels, but it is unclear whether they share these conserved functional features. The most divergent animals to possess both CaV1 and CaV2 channels are placozoans such as Trichoplax adhaerens, which separated from other animals over 600 million years ago shortly after their emergence. Hence, placozoans can provide important insights into the early evolution of CaV1 and CaV2 channels. Here, we build upon previous characterization of Trichoplax CaV channels by determining the cellular expression and ion-conducting properties of the CaV1 channel orthologue, TCaV1. We show that TCaV1 is expressed in neuroendocrine-like gland cells and contractile dorsal epithelial cells. In vitro, this channel conducts dihydropyridine-insensitive, high-voltage–activated Ca2+ currents with kinetics resembling those of rat CaV1.2 but with left-shifted voltage sensitivity for activation and inactivation. Interestingly, TCaV1, but not TCaV2, exhibits buffer-resistant Ca2+/CaM-dependent inactivation, indicating that this functional divergence evolved prior to the emergence of bilaterian animals and may have contributed to their unique adaptation for cytoplasmic Ca2+ signaling within various cellular contexts.
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Affiliation(s)
- Julia Gauberg
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Wassim Elkhatib
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Carolyn L Smith
- NINDS, National Institutes of Health, Bethesda Maryland, 20892 USA
| | - Anhadvir Singh
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Adriano Senatore
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada.
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5
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Dong N, Bandura J, Zhang Z, Wang Y, Labadie K, Noel B, Davison A, Koene JM, Sun HS, Coutellec MA, Feng ZP. Ion channel profiling of the Lymnaea stagnalis ganglia via transcriptome analysis. BMC Genomics 2021; 22:18. [PMID: 33407100 PMCID: PMC7789530 DOI: 10.1186/s12864-020-07287-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 11/28/2020] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND The pond snail Lymnaea stagnalis (L. stagnalis) has been widely used as a model organism in neurobiology, ecotoxicology, and parasitology due to the relative simplicity of its central nervous system (CNS). However, its usefulness is restricted by a limited availability of transcriptome data. While sequence information for the L. stagnalis CNS transcripts has been obtained from EST libraries and a de novo RNA-seq assembly, the quality of these assemblies is limited by a combination of low coverage of EST libraries, the fragmented nature of de novo assemblies, and lack of reference genome. RESULTS In this study, taking advantage of the recent availability of a preliminary L. stagnalis genome, we generated an RNA-seq library from the adult L. stagnalis CNS, using a combination of genome-guided and de novo assembly programs to identify 17,832 protein-coding L. stagnalis transcripts. We combined our library with existing resources to produce a transcript set with greater sequence length, completeness, and diversity than previously available ones. Using our assembly and functional domain analysis, we profiled L. stagnalis CNS transcripts encoding ion channels and ionotropic receptors, which are key proteins for CNS function, and compared their sequences to other vertebrate and invertebrate model organisms. Interestingly, L. stagnalis transcripts encoding numerous putative Ca2+ channels showed the most sequence similarity to those of Mus musculus, Danio rerio, Xenopus tropicalis, Drosophila melanogaster, and Caenorhabditis elegans, suggesting that many calcium channel-related signaling pathways may be evolutionarily conserved. CONCLUSIONS Our study provides the most thorough characterization to date of the L. stagnalis transcriptome and provides insights into differences between vertebrates and invertebrates in CNS transcript diversity, according to function and protein class. Furthermore, this study provides a complete characterization of the ion channels of Lymnaea stagnalis, opening new avenues for future research on fundamental neurobiological processes in this model system.
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Affiliation(s)
- Nancy Dong
- Department of Physiology, University of Toronto, 3308 MSB, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada
| | - Julia Bandura
- Department of Physiology, University of Toronto, 3308 MSB, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada
| | - Zhaolei Zhang
- Donnelly Centre for Cellular and Biomolecular Research and Department of Molecular Genetics, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | - Yan Wang
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, M1C 1A4, Canada
| | - Karine Labadie
- Genoscope, Institut de biologie François Jacob, Commissariat à l'Energie Atomique (CEA), Université Paris-Saclay, BP5706, 91057, Evry, France
| | - Benjamin Noel
- Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, University of Evry, Université Paris-Saclay, 91057, Evry, France
| | - Angus Davison
- School of Life Sciences, University of Nottingham, University Park, Nottingham, UK, NG7 2RD, UK
| | - Joris M Koene
- Department of Ecological Science, Faculty of Science, Vrije Universiteit, Amsterdam, The Netherlands
| | - Hong-Shuo Sun
- Department of Physiology, University of Toronto, 3308 MSB, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada
- Department of Surgery, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
| | | | - Zhong-Ping Feng
- Department of Physiology, University of Toronto, 3308 MSB, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada.
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6
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Gauberg J, Abdallah S, Elkhatib W, Harracksingh AN, Piekut T, Stanley EF, Senatore A. Conserved biophysical features of the Ca V2 presynaptic Ca 2+ channel homologue from the early-diverging animal Trichoplax adhaerens. J Biol Chem 2020; 295:18553-18578. [PMID: 33097592 PMCID: PMC7939481 DOI: 10.1074/jbc.ra120.015725] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 10/21/2020] [Indexed: 12/20/2022] Open
Abstract
The dominant role of CaV2 voltage-gated calcium channels for driving neurotransmitter release is broadly conserved. Given the overlapping functional properties of CaV2 and CaV1 channels, and less so CaV3 channels, it is unclear why there have not been major shifts toward dependence on other CaV channels for synaptic transmission. Here, we provide a structural and functional profile of the CaV2 channel cloned from the early-diverging animal Trichoplax adhaerens, which lacks a nervous system but possesses single gene homologues for CaV1-CaV3 channels. Remarkably, the highly divergent channel possesses similar features as human CaV2.1 and other CaV2 channels, including high voltage-activated currents that are larger in external Ba2+ than in Ca2+; voltage-dependent kinetics of activation, inactivation, and deactivation; and bimodal recovery from inactivation. Altogether, the functional profile of Trichoplax CaV2 suggests that the core features of presynaptic CaV2 channels were established early during animal evolution, after CaV1 and CaV2 channels emerged via proposed gene duplication from an ancestral CaV1/2 type channel. The Trichoplax channel was relatively insensitive to mammalian CaV2 channel blockers ω-agatoxin-IVA and ω-conotoxin-GVIA and to metal cation blockers Cd2+ and Ni2+ Also absent was the capacity for voltage-dependent G-protein inhibition by co-expressed Trichoplax Gβγ subunits, which nevertheless inhibited the human CaV2.1 channel, suggesting that this modulatory capacity evolved via changes in channel sequence/structure, and not G proteins. Last, the Trichoplax channel was immunolocalized in cells that express an endomorphin-like peptide implicated in cell signaling and locomotive behavior and other likely secretory cells, suggesting contributions to regulated exocytosis.
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Affiliation(s)
- Julia Gauberg
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Salsabil Abdallah
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Wassim Elkhatib
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Alicia N Harracksingh
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Thomas Piekut
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Elise F Stanley
- Laboratory of Synaptic Transmission, Krembil Research Institute, Toronto, Ontario, Canada
| | - Adriano Senatore
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada.
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7
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de Hoog E, Lukewich MK, Spencer GE. Retinoid receptor-based signaling plays a role in voltage-dependent inhibition of invertebrate voltage-gated Ca 2+ channels. J Biol Chem 2019; 294:10076-10093. [PMID: 31048374 DOI: 10.1074/jbc.ra118.006444] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 04/30/2019] [Indexed: 01/04/2023] Open
Abstract
The retinoic acid receptor (RAR) and retinoid X receptor (RXR) mediate the cellular effects of retinoids (derivatives of vitamin A). Both RAR and RXR signaling events are implicated in hippocampal synaptic plasticity. Furthermore, retinoids can interact with calcium signaling during homeostatic plasticity. We recently provided evidence that retinoids attenuate calcium current (I Ca) through neuronal voltage-gated calcium channels (VGCCs). We now examined the possibility that constitutive activity of neuronal RXR and/or RAR alters calcium influx via the VGCCs. We found that in neurons of the mollusk Lymnaea stagnalis, two different RXR antagonists (PA452 and HX531) had independent and opposing effects on I Ca that were also time-dependent; whereas the RXR pan-antagonist PA452 enhanced I Ca, HX531 reduced I Ca Interestingly, this effect of HX531 occurred through voltage-dependent inhibition of VGCCs, a phenomenon known to influence neurotransmitter release from neurons. This inhibition appeared to be independent of G proteins and was largely restricted to Cav2 Ca2+ channels. Of note, an RAR pan-antagonist, LE540, also inhibited I Ca but produced G protein-dependent, voltage-dependent inhibition of VGCCs. These findings provide evidence that retinoid receptors interact with G proteins in neurons and suggest mechanisms by which retinoids might affect synaptic calcium signaling.
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Affiliation(s)
- Eric de Hoog
- From the Department of Biological Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada
| | - Mark K Lukewich
- From the Department of Biological Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada
| | - Gaynor E Spencer
- From the Department of Biological Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada
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8
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de Hoog E, Lukewich MK, Spencer GE. Retinoic acid inhibits neuronal voltage-gated calcium channels. Cell Calcium 2018; 72:51-61. [DOI: 10.1016/j.ceca.2018.02.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 01/17/2018] [Accepted: 02/08/2018] [Indexed: 10/18/2022]
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9
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Vatanparast J, Andalib-Lari F. Camphor elicits epileptiform discharges in snail neurons: The role of ion channels modulation. Neurotoxicology 2017; 60:299-307. [DOI: 10.1016/j.neuro.2015.12.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/15/2015] [Accepted: 12/15/2015] [Indexed: 11/25/2022]
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10
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Honeybee locomotion is impaired by Am-Ca V3 low voltage-activated Ca 2+ channel antagonist. Sci Rep 2017; 7:41782. [PMID: 28145504 PMCID: PMC5286435 DOI: 10.1038/srep41782] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 12/29/2016] [Indexed: 11/17/2022] Open
Abstract
Voltage‐gated Ca2+ channels are key transducers of cellular excitability and participate in several crucial physiological responses. In vertebrates, 10 Ca2+ channel genes, grouped in 3 families (CaV1, CaV2 and CaV3), have been described and characterized. Insects possess only one member of each family. These genes have been isolated in a limited number of species and very few have been characterized although, in addition to their crucial role, they may represent a collateral target for neurotoxic insecticides. We have isolated the 3 genes coding for the 3 Ca2+ channels expressed in Apis mellifera. This work provides the first detailed characterization of the honeybee T-type CaV3 Ca2+ channel and demonstrates the low toxicity of inhibiting this channel. Comparing Ca2+ currents recorded in bee neurons and myocytes with Ca2+ currents recorded in Xenopus oocytes expressing the honeybee CaV3 gene suggests native expression in bee muscle cells only. High‐voltage activated Ca2+ channels could be recorded in the somata of different cultured bee neurons. These functional data were confirmed by in situ hybridization, immunolocalization and in vivo analysis of the effects of a CaV3 inhibitor. The biophysical and pharmacological characterization and the tissue distribution of CaV3 suggest a role in honeybee muscle function.
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11
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Senatore A, Raiss H, Le P. Physiology and Evolution of Voltage-Gated Calcium Channels in Early Diverging Animal Phyla: Cnidaria, Placozoa, Porifera and Ctenophora. Front Physiol 2016; 7:481. [PMID: 27867359 PMCID: PMC5095125 DOI: 10.3389/fphys.2016.00481] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 10/07/2016] [Indexed: 12/18/2022] Open
Abstract
Voltage-gated calcium (Cav) channels serve dual roles in the cell, where they can both depolarize the membrane potential for electrical excitability, and activate transient cytoplasmic Ca2+ signals. In animals, Cav channels play crucial roles including driving muscle contraction (excitation-contraction coupling), gene expression (excitation-transcription coupling), pre-synaptic and neuroendocrine exocytosis (excitation-secretion coupling), regulation of flagellar/ciliary beating, and regulation of cellular excitability, either directly or through modulation of other Ca2+-sensitive ion channels. In recent years, genome sequencing has provided significant insights into the molecular evolution of Cav channels. Furthermore, expanded gene datasets have permitted improved inference of the species phylogeny at the base of Metazoa, providing clearer insights into the evolution of complex animal traits which involve Cav channels, including the nervous system. For the various types of metazoan Cav channels, key properties that determine their cellular contribution include: Ion selectivity, pore gating, and, importantly, cytoplasmic protein-protein interactions that direct sub-cellular localization and functional complexing. It is unclear when these defining features, many of which are essential for nervous system function, evolved. In this review, we highlight some experimental observations that implicate Cav channels in the physiology and behavior of the most early-diverging animals from the phyla Cnidaria, Placozoa, Porifera, and Ctenophora. Given our limited understanding of the molecular biology of Cav channels in these basal animal lineages, we infer insights from better-studied vertebrate and invertebrate animals. We also highlight some apparently conserved cellular functions of Cav channels, which might have emerged very early on during metazoan evolution, or perhaps predated it.
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Affiliation(s)
- Adriano Senatore
- Department of Biology, University of Toronto Mississauga Mississauga, ON, Canada
| | - Hamad Raiss
- Department of Biology, University of Toronto Mississauga Mississauga, ON, Canada
| | - Phuong Le
- Department of Biology, University of Toronto Mississauga Mississauga, ON, Canada
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12
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Luk CC, Lee AJ, Wijdenes P, Zaidi W, Leung A, Wong NY, Andrews J, Syed NI. Trophic factor-induced activity 'signature' regulates the functional expression of postsynaptic excitatory acetylcholine receptors required for synaptogenesis. Sci Rep 2015; 5:9523. [PMID: 25827640 PMCID: PMC4381329 DOI: 10.1038/srep09523] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 03/03/2015] [Indexed: 01/08/2023] Open
Abstract
Highly coordinated and coincidental patterns of activity-dependent mechanisms (“fire together wire together”) are thought to serve as inductive signals during synaptogenesis, enabling neuronal pairing between specific sub-sets of excitatory partners. However, neither the nature of activity triggers, nor the “activity signature” of long-term neuronal firing in developing/regenerating neurons have yet been fully defined. Using a highly tractable model system comprising of identified cholinergic neurons from Lymnaea, we have discovered that intrinsic trophic factors present in the Lymnaea brain-conditioned medium (CM) act as a natural trigger for activity patterns in post- but not the presynaptic neuron. Using microelectrode array recordings, we demonstrate that trophic factors trigger stereotypical activity patterns that include changes in frequency, activity and variance. These parameters were reliable indicators of whether a neuron expressed functional excitatory or inhibitory nAChRs and synapse formation. Surprisingly, we found that the post- but not the presynaptic cell exhibits these changes in activity patterns, and that the functional expression of excitatory nAChRs required neuronal somata, de novo protein synthesis and voltage gated calcium channels. In summary, our data provides novel insights into trophic factor mediated actions on neuronal activity and its specific regulation of nAChR expression.
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Affiliation(s)
- Collin C Luk
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta, Canada
| | - Arthur J Lee
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta, Canada
| | - Pierre Wijdenes
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta, Canada
| | - Wali Zaidi
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta, Canada
| | - Andrew Leung
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta, Canada
| | - Noelle Y Wong
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta, Canada
| | - Joseph Andrews
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta, Canada
| | - Naweed I Syed
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta, Canada
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13
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Cens T, Rousset M, Collet C, Charreton M, Garnery L, Le Conte Y, Chahine M, Sandoz JC, Charnet P. Molecular characterization and functional expression of the Apis mellifera voltage-dependent Ca2+ channels. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2015; 58:12-27. [PMID: 25602183 DOI: 10.1016/j.ibmb.2015.01.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/09/2015] [Accepted: 01/09/2015] [Indexed: 06/04/2023]
Abstract
Voltage-gated Ca(2+) channels allow the influx of Ca(2+) ions from the extracellular space upon membrane depolarization and thus serve as a transducer between membrane potential and cellular events initiated by Ca(2+) transients. Most insects are predicted to possess three genes encoding Cavα, the main subunit of Ca(2+) channels, and several genes encoding the two auxiliary subunits, Cavβ and Cavα2δ; however very few of these genes have been cloned so far. Here, we cloned three full-length cDNAs encoding the three Cavα subunits (AmelCav1a, AmelCav2a and AmelCav3a), a cDNA encoding a novel variant of the Cavβ subunit (AmelCavβc), and three full-length cDNAs encoding three Cavα2δ subunits (AmelCavα2δ1 to 3) of the honeybee Apis mellifera. We identified several alternative or mutually exclusive exons in the sequence of the AmelCav2 and AmelCav3 genes. Moreover, we detected a stretch of glutamine residues in the C-terminus of the AmelCav1 subunit that is reminiscent of the motif found in the human Cav2.1 subunit of patients with Spinocerebellar Ataxia type 6. All these subunits contain structural domains that have been identified as functionally important in their mammalian homologues. For the first time, we could express three insect Cavα subunits in Xenopus oocytes and we show that AmelCav1a, 2a and 3a form Ca(2+) channels with distinctive properties. Notably, the co-expression of AmelCav1a or AmelCav2a with AmelCavβc and AmCavα2δ1 produces High Voltage-Activated Ca(2+) channels. On the other hand, expression of AmelCav3a alone leads to Low Voltage-Activated Ca(2+) channels.
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Affiliation(s)
- Thierry Cens
- Institut des Biomolécules Max Mousseron (IBMM), CNRS UMR 5247, Place Eugène Bataillon, 34095 Montpellier cedex 5, France; Centre de Recherche de Biochimie Macromoléculaire (CRBM), CNRS UMR 5237, 1919 Route de Mende, 34293 Montpellier cedex 5, France; Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier cedex 5, France.
| | - Matthieu Rousset
- Institut des Biomolécules Max Mousseron (IBMM), CNRS UMR 5247, Place Eugène Bataillon, 34095 Montpellier cedex 5, France; Centre de Recherche de Biochimie Macromoléculaire (CRBM), CNRS UMR 5237, 1919 Route de Mende, 34293 Montpellier cedex 5, France; Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier cedex 5, France.
| | - Claude Collet
- INRA UR 406 Abeilles et Environnement, 228 Route de l'aérodrome, Domaine Saint Paul, Site Agroparc, CS40509, 84914 Avignon cedex 9, France.
| | - Mercedes Charreton
- INRA UR 406 Abeilles et Environnement, 228 Route de l'aérodrome, Domaine Saint Paul, Site Agroparc, CS40509, 84914 Avignon cedex 9, France.
| | - Lionel Garnery
- Laboratoire Evolution Génome et Spéciation (LEGS), CNRS UPR 9034, Avenue de la Terrasse, Bâtiment 13, 91198 Gif sur Yvette, France.
| | - Yves Le Conte
- INRA UR 406 Abeilles et Environnement, 228 Route de l'aérodrome, Domaine Saint Paul, Site Agroparc, CS40509, 84914 Avignon cedex 9, France.
| | - Mohamed Chahine
- Centre de recherche, Institut universitaire en santé mentale de Québec, 2601 Chemin de la Canardière, Québec Québec G1J 2G3, Canada.
| | - Jean-Christophe Sandoz
- Laboratoire Evolution Génome et Spéciation (LEGS), CNRS UPR 9034, Avenue de la Terrasse, Bâtiment 13, 91198 Gif sur Yvette, France.
| | - Pierre Charnet
- Institut des Biomolécules Max Mousseron (IBMM), CNRS UMR 5247, Place Eugène Bataillon, 34095 Montpellier cedex 5, France; Centre de Recherche de Biochimie Macromoléculaire (CRBM), CNRS UMR 5237, 1919 Route de Mende, 34293 Montpellier cedex 5, France; Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier cedex 5, France.
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14
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Treinys R, Kaselis A, Jover E, Bagnard D, Šatkauskas S. R-type calcium channels are crucial for semaphorin 3A-induced DRG axon growth cone collapse. PLoS One 2014; 9:e102357. [PMID: 25032951 PMCID: PMC4102519 DOI: 10.1371/journal.pone.0102357] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 06/18/2014] [Indexed: 12/20/2022] Open
Abstract
Semaphorin 3A (Sema3A) is a secreted protein involved in axon path-finding during nervous system development. Calcium signaling plays an important role during axonal growth in response to different guidance cues; however it remains unclear whether this is also the case for Sema3A. In this study we used intracellular calcium imaging to figure out whether Sema3A-induced growth cone collapse is a Ca2+ dependent process. Intracellular Ca2+ imaging results using Fura-2 AM showed Ca2+ increase in E15 mice dorsal root ganglia neurons upon Sema3A treatment. Consequently we analyzed Sema3A effect on growth cones after blocking or modifying intracellular and extracellular Ca2+ channels that are expressed in E15 mouse embryos. Our results demonstrate that Sema3A increased growth cone collapse rate is blocked by the non-selective R- and T- type Ca2+ channel blocker NiCl2 and by the selective R-type Ca2+ channel blocker SNX482. These Ca2+ channel blockers consistently decreased the Sema3A-induced intracellular Ca2+ concentration elevation. Overall, our results demonstrate that Sema3A-induced growth cone collapses are intimately related with increase in intracellular calcium concentration mediated by R-type calcium channels.
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Affiliation(s)
- Rimantas Treinys
- Biophysical Research Group, Biology department, Vytautas Magnus University, Kaunas, Lithuania
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Andrius Kaselis
- Biophysical Research Group, Biology department, Vytautas Magnus University, Kaunas, Lithuania
| | - Emmanuel Jover
- INCI – UPR-CNRS 3212, Neurotransmission et sécrétion neuroendocrine, Strasbourg, France
| | - Dominique Bagnard
- INSERM U1109, MN3t lab, Labex Medalis, University of Strasbourg, Strasbourg, France
| | - Saulius Šatkauskas
- Biophysical Research Group, Biology department, Vytautas Magnus University, Kaunas, Lithuania
- * E-mail:
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15
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Dawson TF, Boone AN, Senatore A, Piticaru J, Thiyagalingam S, Jackson D, Davison A, Spafford JD. Gene splicing of an invertebrate beta subunit (LCavβ) in the N-terminal and HOOK domains and its regulation of LCav1 and LCav2 calcium channels. PLoS One 2014; 9:e92941. [PMID: 24690951 PMCID: PMC3972191 DOI: 10.1371/journal.pone.0092941] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 02/27/2014] [Indexed: 01/31/2023] Open
Abstract
The accessory beta subunit (Ca(v)β) of calcium channels first appear in the same genome as Ca(v)1 L-type calcium channels in single-celled coanoflagellates. The complexity of this relationship expanded in vertebrates to include four different possible Ca(v)β subunits (β1, β2, β3, β4) which associate with four Ca(v)1 channel isoforms (Ca(v)1.1 to Ca(v)1.4) and three Ca(v)2 channel isoforms (Ca(v)2.1 to Ca(v)2.3). Here we assess the fundamentally-shared features of the Ca(v)β subunit in an invertebrate model (pond snail Lymnaea stagnalis) that bears only three homologous genes: (LCa(v)1, LCa(v)2, and LCa(v)β). Invertebrate Ca(v)β subunits (in flatworms, snails, squid and honeybees) slow the inactivation kinetics of Ca(v)2 channels, and they do so with variable N-termini and lacking the canonical palmitoylation residues of the vertebrate β2a subunit. Alternative splicing of exon 7 of the HOOK domain is a primary determinant of a slow inactivation kinetics imparted by the invertebrate LCa(v)β subunit. LCa(v)β will also slow the inactivation kinetics of LCa(v)3 T-type channels, but this is likely not physiologically relevant in vivo. Variable N-termini have little influence on the voltage-dependent inactivation kinetics of differing invertebrate Ca(v)β subunits, but the expression pattern of N-terminal splice isoforms appears to be highly tissue specific. Molluscan LCa(v)β subunits have an N-terminal "A" isoform (coded by exons: 1a and 1b) that structurally resembles the muscle specific variant of vertebrate β1a subunit, and has a broad mRNA expression profile in brain, heart, muscle and glands. A more variable "B" N-terminus (exon 2) in the exon position of mammalian β3 and has a more brain-centric mRNA expression pattern. Lastly, we suggest that the facilitation of closed-state inactivation (e.g. observed in Ca(v)2.2 and Ca(v)β3 subunit combinations) is a specialization in vertebrates, because neither snail subunit (LCa(v)2 nor LCa(v)β) appears to be compatible with this observed property.
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Affiliation(s)
- Taylor F. Dawson
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Adrienne N. Boone
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Adriano Senatore
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Joshua Piticaru
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | | | - Daniel Jackson
- Institute of Genetics, School of Biology, University of Nottingham, Nottingham, United Kingdom
| | - Angus Davison
- Institute of Genetics, School of Biology, University of Nottingham, Nottingham, United Kingdom
| | - J. David Spafford
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
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16
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Abstract
The electrical output of neurons relies critically on voltage- and calcium-gated ion channels. The traditional view of ion channels is that they operate independently of each other in the plasma membrane in a manner that could be predicted according to biophysical characteristics of the isolated current. However, there is increasing evidence that channels interact with each other not just functionally but also physically. This is exemplified in the case of Cav3 T-type calcium channels, where new work indicates the ability to form signaling complexes with different types of calcium-gated and even voltage-gated potassium channels. The formation of a Cav3-K complex provides the calcium source required to activate KCa1.1 or KCa3.1 channels and, furthermore, to bestow a calcium-dependent regulation of Kv4 channels via associated KChIP proteins. Here, we review these interactions and discuss their significance in the context of neuronal firing properties.
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17
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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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18
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Ransdell JL, Temporal S, West NL, Leyrer ML, Schulz DJ. Characterization of inward currents and channels underlying burst activity in motoneurons of crab cardiac ganglion. J Neurophysiol 2013; 110:42-54. [DOI: 10.1152/jn.00009.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Large cell motoneurons in the Cancer borealis cardiac ganglion generate rhythmic bursts of action potentials responsible for cardiac contractions. While it is well known that these burst potentials are dependent on coordinated interactions among depolarizing and hyperpolarizing conductances, the depolarizing currents present in these cells, and their biophysical characteristics, have not been thoroughly described. In this study we used a combined molecular biology and electrophysiology approach to look at channel identity, expression, localization, and biophysical properties for two distinct high-voltage-activated calcium currents present in these cells: a slow calcium current ( ICaS) and a transient calcium current ( ICaT). Our data indicate that CbCaV1 is a putative voltage-gated calcium channel subunit in part responsible for an L-type current, while CbCaV2 (formerly cacophony) is a subunit in part responsible for a P/Q-type current. These channels appear to be localized primarily to the somata of the motoneurons. A third calcium channel gene (CbCaV3) was identified that encodes a putative T-type calcium channel subunit and is expressed in these cells, but electrophysiological studies failed to detect this current in motoneuron somata. In addition, we identify and characterize for the first time in these cells a calcium-activated nonselective cationic current ( ICAN), as well as a largely noninactivating TTX-sensitive current reminiscent of a persistent sodium current. The identification and further characterization of these currents allow both biological and modeling studies to move forward with more attention to the complexity of interactions among these distinct components underlying generation of bursting output in motoneurons.
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Affiliation(s)
- Joseph L. Ransdell
- Department of Biological Sciences, University of Missouri, Columbia, Missouri
| | - Simone Temporal
- Department of Biological Sciences, University of Missouri, Columbia, Missouri
| | - Nicole L. West
- Department of Biological Sciences, University of Missouri, Columbia, Missouri
| | - Megan L. Leyrer
- Department of Biological Sciences, University of Missouri, Columbia, Missouri
| | - David J. Schulz
- Department of Biological Sciences, University of Missouri, Columbia, Missouri
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19
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Taiakina V, Boone AN, Fux J, Senatore A, Weber-Adrian D, Guillemette JG, Spafford JD. The calmodulin-binding, short linear motif, NSCaTE is conserved in L-type channel ancestors of vertebrate Cav1.2 and Cav1.3 channels. PLoS One 2013; 8:e61765. [PMID: 23626724 PMCID: PMC3634016 DOI: 10.1371/journal.pone.0061765] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 03/11/2013] [Indexed: 01/21/2023] Open
Abstract
NSCaTE is a short linear motif of (xWxxx(I or L)xxxx), composed of residues with a high helix-forming propensity within a mostly disordered N-terminus that is conserved in L-type calcium channels from protostome invertebrates to humans. NSCaTE is an optional, lower affinity and calcium-sensitive binding site for calmodulin (CaM) which competes for CaM binding with a more ancient, C-terminal IQ domain on L-type channels. CaM bound to N- and C- terminal tails serve as dual detectors to changing intracellular Ca2+ concentrations, promoting calcium-dependent inactivation of L-type calcium channels. NSCaTE is absent in some arthropod species, and is also lacking in vertebrate L-type isoforms, Cav1.1 and Cav1.4 channels. The pervasiveness of a methionine just downstream from NSCaTE suggests that L-type channels could generate alternative N-termini lacking NSCaTE through the choice of translational start sites. Long N-terminus with an NSCaTE motif in L-type calcium channel homolog LCav1 from pond snail Lymnaea stagnalis has a faster calcium-dependent inactivation than a shortened N-termini lacking NSCaTE. NSCaTE effects are present in low concentrations of internal buffer (0.5 mM EGTA), but disappears in high buffer conditions (10 mM EGTA). Snail and mammalian NSCaTE have an alpha-helical propensity upon binding Ca2+-CaM and can saturate both CaM N-terminal and C-terminal domains in the absence of a competing IQ motif. NSCaTE evolved in ancestors of the first animals with internal organs for promoting a more rapid, calcium-sensitive inactivation of L-type channels.
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Affiliation(s)
| | | | - Julia Fux
- Department of Biology, University of Waterloo, Waterloo, Canada
| | | | | | | | - J. David Spafford
- Department of Biology, University of Waterloo, Waterloo, Canada
- * E-mail:
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20
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Senatore A, Monteil A, van Minnen J, Smit AB, Spafford JD. NALCN ion channels have alternative selectivity filters resembling calcium channels or sodium channels. PLoS One 2013; 8:e55088. [PMID: 23383067 PMCID: PMC3557258 DOI: 10.1371/journal.pone.0055088] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 12/19/2012] [Indexed: 11/17/2022] Open
Abstract
NALCN is a member of the family of ion channels with four homologous, repeat domains that include voltage-gated calcium and sodium channels. NALCN is a highly conserved gene from simple, extant multicellular organisms without nervous systems such as sponges and placozoans and mostly remains a single gene compared to the calcium and sodium channels which diversified into twenty genes in humans. The single NALCN gene has alternatively-spliced exons at exons 15 or exon 31 that splices in novel selectivity filter residues that resemble calcium channels (EEEE) or sodium channels (EKEE or EEKE). NALCN channels with alternative calcium, (EEEE) and sodium, (EKEE or EEKE) -selective pores are conserved in simple bilaterally symmetrical animals like flatworms to non-chordate deuterostomes. The single NALCN gene is limited as a sodium channel with a lysine (K)-containing pore in vertebrates, but originally NALCN was a calcium-like channel, and evolved to operate as both a calcium channel and sodium channel for different roles in many invertebrates. Expression patterns of NALCN-EKEE in pond snail, Lymnaea stagnalis suggest roles for NALCN in secretion, with an abundant expression in brain, and an up-regulation in secretory organs of sexually-mature adults such as albumen gland and prostate. NALCN-EEEE is equally abundant as NALCN-EKEE in snails, but is greater expressed in heart and other muscle tissue, and 50% less expressed in the brain than NALCN-EKEE. Transfected snail NALCN-EEEE and NALCN-EKEE channel isoforms express in HEK-293T cells. We were not able to distinguish potential NALCN currents from background, non-selective leak conductances in HEK293T cells. Native leak currents without expressing NALCN genes in HEK-293T cells are NMDG(+) impermeant and blockable with 10 µM Gd(3+) ions and are indistinguishable from the hallmark currents ascribed to mammalian NALCN currents expressed in vitro by Lu et al. in Cell. 2007 Apr 20;129(2):371-83.
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21
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Senatore A, Spafford JD. Gene transcription and splicing of T-type channels are evolutionarily-conserved strategies for regulating channel expression and gating. PLoS One 2012; 7:e37409. [PMID: 22719839 PMCID: PMC3376122 DOI: 10.1371/journal.pone.0037409] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 04/19/2012] [Indexed: 01/17/2023] Open
Abstract
T-type calcium channels operate within tightly regulated biophysical constraints for supporting rhythmic firing in the brain, heart and secretory organs of invertebrates and vertebrates. The snail T-type gene, LCa(v)3 from Lymnaea stagnalis, possesses alternative, tandem donor splice sites enabling a choice of a large exon 8b (201 aa) or a short exon 25c (9 aa) in cytoplasmic linkers, similar to mammalian homologs. Inclusion of optional 25c exons in the III-IV linker of T-type channels speeds up kinetics and causes hyperpolarizing shifts in both activation and steady-state inactivation of macroscopic currents. The abundant variant lacking exon 25c is the workhorse of embryonic Ca(v)3 channels, whose high density and right-shifted activation and availability curves are expected to increase pace-making and allow the channels to contribute more significantly to cellular excitation in prenatal tissue. Presence of brain-enriched, optional exon 8b conserved with mammalian Ca(v)3.1 and encompassing the proximal half of the I-II linker, imparts a ~50% reduction in total and surface-expressed LCa(v)3 channel protein, which accounts for reduced whole-cell calcium currents of +8b variants in HEK cells. Evolutionarily conserved optional exons in cytoplasmic linkers of Ca(v)3 channels regulate expression (exon 8b) and a battery of biophysical properties (exon 25c) for tuning specialized firing patterns in different tissues and throughout development.
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22
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23
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Tuckwell HC. Quantitative aspects of L-type Ca2+ currents. Prog Neurobiol 2012; 96:1-31. [DOI: 10.1016/j.pneurobio.2011.09.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 09/16/2011] [Accepted: 09/23/2011] [Indexed: 12/24/2022]
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24
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Getz A, Xu F, Zaidi W, Syed NI. The antidepressant fluoxetine but not citalopram suppresses synapse formation and synaptic transmission between Lymnaea neurons by perturbing presynaptic and postsynaptic machinery. Eur J Neurosci 2011; 34:221-34. [DOI: 10.1111/j.1460-9568.2011.07757.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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25
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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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26
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Xu F, Luk C, Richard MP, Zaidi W, Farkas S, Getz A, Lee A, van Minnen J, Syed NI. Antidepressant fluoxetine suppresses neuronal growth from both vertebrate and invertebrate neurons and perturbs synapse formation betweenLymnaeaneurons. Eur J Neurosci 2010; 31:994-1005. [DOI: 10.1111/j.1460-9568.2010.07129.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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27
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Senatore A, Spafford JD. Transient and big are key features of an invertebrate T-type channel (LCav3) from the central nervous system of Lymnaea stagnalis. J Biol Chem 2010; 285:7447-58. [PMID: 20056611 DOI: 10.1074/jbc.m109.090753] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Here we describe features of the first non-mammalian T-type calcium channel (LCa(v)3) expressed in vitro. This molluscan channel possesses combined biophysical properties that are reminiscent of all mammalian T-type channels. It exhibits T-type features such as "transient" kinetics, but the "tiny" label, usually associated with Ba(2+) conductance, is hard to reconcile with the "bigness" of this channel in many respects. LCa(v)3 is 25% larger than any voltage-gated ion channel expressed to date. It codes for a massive, 322-kDa protein that conducts large macroscopic currents in vitro. LCa(v)3 is also the most abundant Ca(2+) channel transcript in the snail nervous system. A window current at typical resting potentials appears to be at least as large as that reported for mammalian channels. This distant gene provides a unique perspective to analyze the structural, functional, drug binding, and evolutionary aspects of T-type channels.
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Affiliation(s)
- Adriano Senatore
- Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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28
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Trophic factor-induced intracellular calcium oscillations are required for the expression of postsynaptic acetylcholine receptors during synapse formation between Lymnaea neurons. J Neurosci 2009; 29:2167-76. [PMID: 19228969 DOI: 10.1523/jneurosci.4682-08.2009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Nervous system functions in all animals rely upon synaptic connectivity that is established during early development. Whereas cell-cell signaling plays a critical role in establishing synapse specificity, the involvement of extrinsic growth factors cannot, however, be undermined. We have previously demonstrated that trophic factors are required for excitatory but not inhibitory synapse formation between Lymnaea neurons. Moreover, in the absence of trophic factors, neurons from a number of species establish inappropriate inhibitory synapses, which can, however, be corrected by the addition of trophic factors. The precise site of trophic factor actions (presynaptic versus postsynaptic) and the underlying mechanisms remain, however, undefined. Here, we provide the first direct evidence that the trophic factor-mediated excitatory synapse formation involves activity-induced calcium (Ca(2+)) oscillations in the postsynaptic left pedal dorsal 1 (LPeD1) but not the presynaptic visceral dorsal 4 (VD4, cholinergic) neuron. These oscillations involved Ca(2+) influx through voltage-gated Ca(2+) channels and required receptor tyrosine kinase activity which was essential for the expression of excitatory, nicotinic acetylcholine receptors in the postsynaptic cell during synapse formation. We also demonstrate that selectively blocking the electrical activity presynaptically did not perturb trophic factor-induced synapse formation between the paired cells, whereas hyperpolarizing the postsynaptic cell prevented appropriate synaptogenesis between VD4 and LPeD1 cells. Together, our data underscore the importance of extrinsic trophic factors in regulating the electrical activity of the postsynaptic but not the presynaptic cell and that the resulting Ca(2+) oscillations are essential for the expression of postsynaptic receptors during specific synapse formation.
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29
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Dunn T, McCamphill P, Syed N. Activity-induced large amplitude postsynaptic mPSPs at soma-soma synapses between Lymnaea neurons. Synapse 2008; 63:117-25. [DOI: 10.1002/syn.20589] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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30
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McCamphill PK, Dunn TW, Syed NI. Serotonin modulates transmitter release at central Lymnaea synapses through a G-protein-coupled and cAMP-mediated pathway. Eur J Neurosci 2008; 27:2033-42. [PMID: 18412624 DOI: 10.1111/j.1460-9568.2008.06180.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Neuromodulation is central to all nervous system function, although the precise mechanisms by which neurotransmitters affect synaptic efficacy between central neurons remain to be fully elucidated. In this study, we examined the neuromodulatory action of serotonin [5-hydroxytryptamine (5-HT)] at central synapses between identified neurons from the pond snail Lymnaea stagnalis. Using whole-cell voltage-clamp and sharp electrode recording, we show that 5-HT strongly depresses synaptic strength between cultured, cholinergic neuron visceral dorsal 4 (VD4 - presynaptic) and its serotonergic target left pedal dorsal 1 (LPeD1 - postsynaptic). This inhibition was accompanied by a reduction in synaptic depression, but had no effect on postsynaptic input resistance, indicating a presynaptic origin. In addition, serotonin inhibited the presynaptic calcium current (I(Ca)) on a similar time course as the change in synaptic transmission. Introduction of a non-condensable GDP analog, GDP-beta-S, through the presynaptic pipette inhibited the serotonin-mediated effect on I(Ca.) Similar results were obtained with a membrane-impermeable inactive cAMP analog, 8OH-cAMP. Furthermore, stimulation of the serotonergic postsynaptic cell also inhibited presynaptic currents, indicating the presence of a negative feedback loop between LPeD1 and VD4. Taken together, this study provides direct evidence for a negative feedback mechanism, whereby the activity of a presynaptic respiratory central pattern-generating neuron is regulated by its postsynaptic target cell. We demonstrate that either serotonin or LPeD1 activity-induced depression of presynaptic transmitter release from VD4 involves voltage-gated calcium channels and is mediated through a G-protein-coupled and cAMP-mediated system.
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Affiliation(s)
- P K McCamphill
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
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31
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PKC-induced intracellular trafficking of Ca(V)2 precedes its rapid recruitment to the plasma membrane. J Neurosci 2008; 28:2601-12. [PMID: 18322103 DOI: 10.1523/jneurosci.4314-07] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Activation of protein kinase C (PKC) potentiates secretion in Aplysia peptidergic neurons, in part by inducing new sites for peptide release at growth cone terminals. The mechanisms by which ion channels are trafficked to such sites are, however, not well understood. We now show that PKC activation rapidly recruits new Ca(V)2 subunits to the plasma membrane, and that recruitment is blocked by latrunculin B, an inhibitor of actin polymerization. In contrast, inhibition of microtubule polymerization selectively prevents the appearance of Ca(V)2 subunits only at the distal edge of the growth cone. In resting neurons, Ca(V)2-containing organelles reside in the central region of growth cones, but are absent from distal lamellipodia. After activation of PKC, these organelles are transported on microtubules to the lamellipodium. The ability to traffic to the most distal sites of channel insertion inside the lamellipodium does, therefore, not require intact actin but requires intact microtubules. Only after activation of PKC do Ca(V)2 channels associate with actin and undergo insertion into the plasma membrane.
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Ukhanov K, Leinders-Zufall T, Zufall F. Patch-clamp analysis of gene-targeted vomeronasal neurons expressing a defined V1r or V2r receptor: ionic mechanisms underlying persistent firing. J Neurophysiol 2007; 98:2357-69. [PMID: 17715188 DOI: 10.1152/jn.00642.2007] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Sensory neurons in the mouse vomeronasal organ consist of two major groups, apical and basal, that project to different brain regions, express unique sets of receptors, and serve distinct functions. Electrical properties of these two subpopulations, however, have not been systematically characterized. V1rb2-tau-GFP and V2r1b-tau-GFP tagged vomeronasal sensory neurons (VSNs) were selected as prototypical apical or basal VSNs, respectively, and their biophysical properties were analyzed in acute slices that minimized cell damage. Basal V2r1b-expressing VSNs had voltage-gated conductances, and especially Na(+) (Nav) and Ca(2+) (Cav) currents, that were substantially larger than those observed in apical V1rb2 VSNs, although the resting membrane potential, input resistance, and membrane capacitance were similar in both cell types. Of several types of Cav currents, T-type and L-type Cav currents contributed to action potential firing, and both currents alone were capable of generating oscillatory Ca(2+) spikes. The L-type Cav current was uniquely coupled to a BK large-conductance K(+) current, and interplay between these channels played a critical role in repolarizing spikes and maintaining persistent firing in VSNs. Larger Nav and Cav conductances, along with a more positive inactivation voltage of the Nav current in the V2r1b VSNs, contributed to the larger spike amplitude and higher spike frequency induced by depolarizing current in these cells compared with V1rb2 VSNs. Basal GFP-negative VSNs and V2r1b VSNs responded to prolonged depolarization with persistent, but adapting discharge that could be relevant in sensory adaptation. Collectively, these results suggest a novel mechanism for regulating and encoding neuronal activity in the accessory olfactory system.
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Affiliation(s)
- Kirill Ukhanov
- Whitney Laboratory for Marine Bioscience, Center for Smell and Taste, and the McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA.
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King GF. Modulation of insect Cav channels by peptidic spider toxins. Toxicon 2007; 49:513-30. [PMID: 17197008 DOI: 10.1016/j.toxicon.2006.11.012] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Accepted: 11/17/2006] [Indexed: 10/23/2022]
Abstract
Insects have a much smaller repertoire of voltage-gated calcium (Ca(V)) channels than vertebrates. Drosophila melanogaster harbors only a single ortholog of each of the vertebrate Ca(V)1, Ca(V)2, and Ca(V)3 subtypes, although its basal inventory is expanded by alternative splicing and editing of Ca(V) channel transcripts. Nevertheless, there appears to be little functional plasticity within this limited panel of insect Ca(V) channels, since severe loss-of-function mutations in genes encoding the pore-forming alpha1 subunits in Drosophila are embryonic lethal. Since the primary role of spider venom is to paralyze or kill insect prey, it is not surprising that most, if not all, spider venoms contain peptides that potently modify the activity of these functionally critical insect Ca(V) channels. Unfortunately, it has proven difficult to determine the precise ion channel subtypes recognized by these peptide toxins since insect Ca(V) channels have significantly different pharmacology to their vertebrate counterparts, and cloned insect Ca(V) channels are not available for electrophysiological studies. However, biochemical and genetic studies indicate that some of these spider toxins might ultimately become the defining pharmacology for certain subtypes of insect Ca(V) channels. This review focuses on peptidic spider toxins that specifically target insect Ca(V) channels. In addition to providing novel molecular tools for ion channel characterization, some of these toxins are being used as leads to develop new methods for controlling insect pests.
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Affiliation(s)
- Glenn F King
- Division of Chemical and Structural Biology, Institute for Molecular Bioscience, University of Queensland, Brisbane Qld. 4072, Australia.
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