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Ricardo PC, Arias MC, de Souza Araujo N. Decoding bee cleptoparasitism through comparative transcriptomics of Coelioxoides waltheriae and its host Tetrapedia diversipes. Sci Rep 2024; 14:12361. [PMID: 38811580 PMCID: PMC11137135 DOI: 10.1038/s41598-024-56261-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 03/04/2024] [Indexed: 05/31/2024] Open
Abstract
Cleptoparasitism, also known as brood parasitism, is a widespread strategy among bee species in which the parasite lays eggs into the nests of the host species. Even though this behavior has significant ecological implications for the dynamics of several species, little is known about the molecular pathways associated with cleptoparasitism. To shed some light on this issue, we used gene expression data to perform a comparative analysis between two solitary neotropical bees: Coelioxoides waltheriae, an obligate parasite, and their specific host Tetrapedia diversipes. We found that ortholog genes involved in signal transduction, sensory perception, learning, and memory formation were differentially expressed between the cleptoparasite and the host. We hypothesize that these genes and their associated molecular pathways are engaged in cleptoparasitism-related processes and, hence, are appealing subjects for further investigation into functional and evolutionary aspects of cleptoparasitism in bees.
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Affiliation(s)
- Paulo Cseri Ricardo
- Departamento de Genética e Biologia Evolutiva - Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.
| | - Maria Cristina Arias
- Departamento de Genética e Biologia Evolutiva - Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
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2
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Dolzer J, Schröder K, Stengl M. Cyclic nucleotide-dependent ionic currents in olfactory receptor neurons of the hawkmoth Manduca sexta suggest pull-push sensitivity modulation. Eur J Neurosci 2021; 54:4804-4826. [PMID: 34128265 DOI: 10.1111/ejn.15346] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 06/02/2021] [Accepted: 06/04/2021] [Indexed: 11/27/2022]
Abstract
Olfactory receptor neurons (ORNs) of the hawkmoth Manduca sexta sensitize via cAMP- and adapt via cGMP-dependent mechanisms. Perforated patch clamp recordings distinguished 11 currents in these ORNs. Derivatives of cAMP and/or cGMP antagonistically affected three of five K+ currents and two non-specific cation currents. The Ca2+ -dependent K+ current IK(Ca 2+ ) and the sensitive pheromone-dependent K+ current IK(cGMP-) , which both express fast kinetics, were inhibited by 8bcGMP, while a slow K+ current, IK(cGMP+) , was activated by 8bcGMP. Furthermore, application of 8bcAMP blocked slowly activating, zero mV-reversing, non-specific cation currents, ILL and Icat(PKC?) , which remained activated in the presence of 8bcGMP. Their activations pull the membrane potential towards their 0-mV reversal potentials, in addition to increasing intracellular Ca2+ levels voltage- and ILL -dependently. Twenty minutes after application, 8bcGMP blocked a TEA-independent K+ current, IK(noTEA) , and a fast cation current, Icat(nRP) , which both shift the membrane potential to negative values. We conclude that conditions of sensitization are maintained at high levels of cAMP, via specific opening/closure of ion channels that allow for fast kinetics, hyperpolarized membrane potentials, and low intracellular Ca2+ levels. In contrast, adaptation is supported via cGMP, which antagonizes cAMP, opening Ca2+ -permeable channels with slow kinetics that stabilize depolarized resting potentials. The antagonistic modulation of peripheral sensory neurons by cAMP or cGMP is reminiscent of pull-push mechanisms of neuromodulation at central synapses underlying metaplasticity.
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Affiliation(s)
- Jan Dolzer
- Biologie, Tierphysiologie, Philipps-Universität Marburg, Marburg, Germany.,Institut für Zoologie, Universität Regensburg, Regensburg, Germany
| | - Katrin Schröder
- Animal Physiology/Neuroethology, Biology, FB 10, University of Kassel, Kassel, Germany
| | - Monika Stengl
- Biologie, Tierphysiologie, Philipps-Universität Marburg, Marburg, Germany.,Institut für Zoologie, Universität Regensburg, Regensburg, Germany.,Animal Physiology/Neuroethology, Biology, FB 10, University of Kassel, Kassel, Germany
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3
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Perrier S, Moreau E, Deshayes C, El-Adouzi M, Goven D, Chandre F, Lapied B. Compensatory mechanisms in resistant Anopheles gambiae AcerKis and KdrKis neurons modulate insecticide-based mosquito control. Commun Biol 2021; 4:665. [PMID: 34079061 PMCID: PMC8172894 DOI: 10.1038/s42003-021-02192-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 05/06/2021] [Indexed: 02/04/2023] Open
Abstract
In the malaria vector Anopheles gambiae, two point mutations in the acetylcholinesterase (ace-1R) and the sodium channel (kdrR) genes confer resistance to organophosphate/carbamate and pyrethroid insecticides, respectively. The mechanisms of compensation that recover the functional alterations associated with these mutations and their role in the modulation of insecticide efficacy are unknown. Using multidisciplinary approaches adapted to neurons isolated from resistant Anopheles gambiae AcerKis and KdrKis strains together with larval bioassays, we demonstrate that nAChRs, and the intracellular calcium concentration represent the key components of an adaptation strategy ensuring neuronal functions maintenance. In AcerKis neurons, the increased effect of acetylcholine related to the reduced acetylcholinesterase activity is compensated by expressing higher density of nAChRs permeable to calcium. In KdrKis neurons, changes in the biophysical properties of the L1014F mutant sodium channel, leading to enhance overlap between activation and inactivation relationships, diminish the resting membrane potential and reduce the fraction of calcium channels available involved in acetylcholine release. Together with the lower intracellular basal calcium concentration observed, these factors increase nAChRs sensitivity to maintain the effect of low concentration of acetylcholine. These results explain the opposite effects of the insecticide clothianidin observed in AcerKis and KdrKis neurons in vitro and in vivo.
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Affiliation(s)
| | | | | | | | | | - Fabrice Chandre
- MIVEGEC, UMR IRD 224-CNRS 5290-Université de Montpellier, 911 avenue Agropolis, Montpellier, Cedex 05, France
| | - Bruno Lapied
- Univ Angers, INRAE, SIFCIR, SFR QUASAV, Angers, France.
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Thompson AJ, Verdin PS, Burton MJ, Davies TGE, Williamson MS, Field LM, Baines RA, Mellor IR, Duce IR. The effects of knock-down resistance mutations and alternative splicing on voltage-gated sodium channels in Musca domestica and Drosophila melanogaster. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2020; 122:103388. [PMID: 32376273 DOI: 10.1016/j.ibmb.2020.103388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/09/2020] [Accepted: 04/13/2020] [Indexed: 06/11/2023]
Abstract
Voltage-gated sodium channels (VGSCs) are a major target site for the action of pyrethroid insecticides and resistance to pyrethroids has been ascribed to mutations in the VGSC gene. VGSCs in insects are encoded by only one gene and their structural and functional diversity results from posttranscriptional modification, particularly, alternative splicing. Using whole cell patch clamping of neurons from pyrethroid susceptible (wild-type) and resistant strains (s-kdr) of housefly, Musca domestica, we have shown that the V50 for activation and steady state inactivation of sodium currents (INa+) is significantly depolarised in s-kdr neurons compared with wild-type and that 10 nM deltamethrin significantly hyperpolarised both of these parameters in the neurons from susceptible but not s-kdr houseflies. Similarly, tail currents were more sensitive to deltamethrin in wild-type neurons (EC15 14.5 nM) than s-kdr (EC15 133 nM). We also found that in both strains, INa+ are of two types: a strongly inactivating (to 6.8% of peak) current, and a more persistent (to 17.1% of peak) current. Analysis of tail currents showed that the persistent current in both strains (wild-type EC15 5.84 nM) was more sensitive to deltamethrin than was the inactivating type (wild-type EC15 35.1 nM). It has been shown previously, that the presence of exon l in the Drosophila melanogaster VGSC gives rise to a more persistent INa+ than does the alternative splice variant containing exon k and we used PCR with housefly head cDNA to confirm the presence of the housefly orthologues of splice variants k and l. Their effect on deltamethrin sensitivity was determined by examining INa+ in Xenopus oocytes expressing either the k or l variants of the Drosophila para VGSC. Analysis of tail currents, in the presence of various concentrations of deltamethrin, showed that the l splice variant was significantly more sensitive (EC50 42 nM) than the k splice variant (EC50 866 nM). We conclude that in addition to the presence of point mutations, target site resistance to pyrethroids may involve the differential expression of splice variants.
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Affiliation(s)
- Andrew J Thompson
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Paul S Verdin
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Mark J Burton
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - T G Emyr Davies
- Rothamsted Research, West Common, Harpenden, Hertfordshire, AL5 2JQ, United Kingdom
| | - Martin S Williamson
- Rothamsted Research, West Common, Harpenden, Hertfordshire, AL5 2JQ, United Kingdom
| | - Linda M Field
- Rothamsted Research, West Common, Harpenden, Hertfordshire, AL5 2JQ, United Kingdom
| | - Richard A Baines
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, M13 9PL, United Kingdom
| | - Ian R Mellor
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Ian R Duce
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, United Kingdom.
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5
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Moreau E, Mikulska-Ruminska K, Goulu M, Perrier S, Deshayes C, Stankiewicz M, Apaire-Marchais V, Nowak W, Lapied B. Orthosteric muscarinic receptor activation by the insect repellent IR3535 opens new prospects in insecticide-based vector control. Sci Rep 2020; 10:6842. [PMID: 32321987 PMCID: PMC7176678 DOI: 10.1038/s41598-020-63957-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 04/08/2020] [Indexed: 01/14/2023] Open
Abstract
The insect repellent IR3535 is one of the important alternative in the fight against mosquito-borne disease such as malaria, dengue, chikungunya, yellow fever and Zika. Using a multidisciplinary approach, we propose the development of an innovative insecticide-based vector control strategy using an unexplored property of IR3535. We have demonstrated that in insect neurosecretory cells, very low concentration of IR3535 induces intracellular calcium rise through cellular mechanisms involving orthosteric/allosteric sites of the M1-muscarinic receptor subtype, G protein βγ subunits, background potassium channel inhibition generating depolarization, which induces voltage-gated calcium channel activation. The resulting internal calcium concentration elevation increases nicotinic receptor sensitivity to the neonicotinoid insecticide thiacloprid. The synergistic interaction between IR3535 and thiacloprid contributes to significantly increase the efficacy of the treatment while reducing concentrations. In this context, IR3535, used as a synergistic agent, seems to promise a new approach in the optimization of the integrated vector management for vector control.
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Affiliation(s)
- Eléonore Moreau
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France
| | - Karolina Mikulska-Ruminska
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, N. Copernicus University, Torun, Poland
| | - Mathilde Goulu
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France
| | - Stéphane Perrier
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France
| | - Caroline Deshayes
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France
| | - Maria Stankiewicz
- Faculty of Biological and Veternary Sciences, N. Copernicus University, Torun, Poland
| | - Véronique Apaire-Marchais
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France
| | - Wieslaw Nowak
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, N. Copernicus University, Torun, Poland
| | - Bruno Lapied
- Laboratoire Signalisation Fonctionnelle des Canaux Ioniques et des Récepteurs (SiFCIR), UPRES EA 2647, USC INRA 1330, SFR QUASAV 4207, UFR Sciences, Université d'Angers, 2 boulevard Lavoisier, 49045, Angers, cedex, France.
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Odor-Induced Multi-Level Inhibitory Maps in Drosophila. eNeuro 2020; 7:ENEURO.0213-19.2019. [PMID: 31888962 PMCID: PMC6957311 DOI: 10.1523/eneuro.0213-19.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 12/06/2019] [Accepted: 12/16/2019] [Indexed: 12/04/2022] Open
Abstract
Optical imaging of intracellular Ca2+ influx as a correlate of neuronal excitation represents a standard technique for visualizing spatiotemporal activity of neuronal networks. However, the information-processing properties of single neurons and neuronal circuits likewise involve inhibition of neuronal membrane potential. Here, we report spatially resolved optical imaging of odor-evoked inhibitory patterns in the olfactory circuitry of Drosophila using a genetically encoded fluorescent Cl- sensor. In combination with the excitatory component reflected by intracellular Ca2+ dynamics, we present a comprehensive functional map of both odor-evoked neuronal activation and inhibition at different levels of olfactory processing. We demonstrate that odor-evoked inhibition carried by Cl- influx is present both in sensory neurons and second-order projection neurons (PNs), and is characterized by stereotypic, odor-specific patterns. Cl--mediated inhibition features distinct dynamics in different neuronal populations. Our data support a dual role of inhibitory neurons in the olfactory system: global gain control across the neuronal circuitry and glomerulus-specific inhibition to enhance neuronal information processing.
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7
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Bayley TG, Hedwig B. Dendritic Ca 2+ dynamics and multimodal processing in a cricket antennal interneuron. J Neurophysiol 2018; 120:910-919. [PMID: 29742027 PMCID: PMC6171068 DOI: 10.1152/jn.00663.2017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The integration of stimuli of different modalities is fundamental to information processing within the nervous system. A descending interneuron in the cricket brain, with prominent dendrites in the deutocerebrum, receives input from three sensory modalities: touch of the antennal flagellum, strain of the antennal base, and visual stimulation. Using calcium imaging, we demonstrate that each modality drives a Ca2+ increase in a different dendritic region. Moreover, touch of the flagellum is represented in a topographic map along the neuron’s dendrites. Using intracellular recording, we investigated the effects of Ca2+ on spike shape through the application of the Ca2+ channel antagonist Cd2+ and identified probable Ca2+-dependent K+ currents. NEW & NOTEWORTHY Different dendritic regions of the cricket brain neuron DBNi1-2 showed localized Ca2+ increases when three modalities of stimulation (touch of the flagellum, strain at antennal base, and visual input) were given. Touch stimulation induces localized Ca2+ increases according to a topographic map of the antenna. Ca2+ appears to activate K+ currents in DBNi1-2.
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Affiliation(s)
| | - Berthold Hedwig
- Department of Zoology, University of Cambridge , Cambridge , United Kingdom
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8
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Otero TF, Valero L, Martinez JG. Polypyrrole-amphiphile blend electrodes: new reaction-driven structural processes with possible formation of vesicles. Electrochim Acta 2017. [DOI: 10.1016/j.electacta.2017.06.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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9
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Lapied B, Defaix A, Stankiewicz M, Moreau E, Raymond V. Modulation of Low-Voltage-Activated Inward Current Permeable to Sodium and Calcium by DARPP-32 Drives Spontaneous Firing of Insect Octopaminergic Neurosecretory Cells. Front Syst Neurosci 2017; 11:31. [PMID: 28579948 PMCID: PMC5437719 DOI: 10.3389/fnsys.2017.00031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 05/03/2017] [Indexed: 12/02/2022] Open
Abstract
Identification of the different intracellular pathways that control phosphorylation/dephosphorylation process of ionic channels represents an exciting alternative approach for studying the ionic mechanisms underlying neuronal pacemaker activity. In the central nervous system of the cockroach Periplaneta americana, octopaminergic neurons, called dorsal unpaired median (DUM; DUM neurons), generate spontaneous repetitive action potentials. Short-term cultured adult DUM neurons isolated from the terminal abdominal ganglion (TAG) of the nerve cord were used to study the regulation of a tetrodotoxin-sensitive low-voltage-activated (LVA) channel permeable to sodium and calcium (Na/Ca), under whole cell voltage- and current-clamp conditions. A bell-shaped curve illustrating the regulation of the amplitude of the maintained current vs. [ATP]i was observed. This suggested the existence of phosphorylation mechanisms. The protein kinase A (PKA) inhibitor, H89 and elevating [cyclic adenosine 3′, 5′ monophosphate, cAMP]i, increased and decreased the current amplitude, respectively. This indicated a regulation of the current via a cAMP/PKA cascade. Furthermore, intracellular application of PP2B inhibitors, cyclosporine A, FK506 and PP1/2A inhibitor, okadaic acid decreased the current amplitude. From these results and because octopamine (OA) regulates DUM neuron electrical activity via an elevation of [cAMP]i, we wanted to know if, like in vertebrate dopaminergic neurons, OA receptor (OAR) stimulation could indirectly affect the current via PKA-mediated phosphorylation of Dopamine- and cAMP-regulated Phosphoprotein-32 (DARPP-32) known to inhibit PP1/2A. Experiments were performed using intracellular application of phospho-DARPP-32 and non-phospho-DARPP-32. Phospho-DARPP-32 strongly reduced the current amplitude whereas non-phospho-DARPP-32 did not affect the current. All together, these results confirm that DARPP-32-mediated inhibition of PP1/2A regulates the maintained sodium/calcium current, which contributes to the development of the pre-depolarizing phase of the DUM neuron pacemaker activity.
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Affiliation(s)
- Bruno Lapied
- Laboratoire SiFCIR UPRES EA 2647/USC INRA 1330, Université Bretagne Loire, University of Angers, UFR SciencesAngers, France
| | - Antoine Defaix
- Laboratoire SiFCIR UPRES EA 2647/USC INRA 1330, Université Bretagne Loire, University of Angers, UFR SciencesAngers, France
| | - Maria Stankiewicz
- Faculty of Biology and Environment Protection, N. Copernicus UniversityTorun, Poland
| | - Eléonore Moreau
- Laboratoire SiFCIR UPRES EA 2647/USC INRA 1330, Université Bretagne Loire, University of Angers, UFR SciencesAngers, France
| | - Valérie Raymond
- Laboratoire SiFCIR UPRES EA 2647/USC INRA 1330, Université Bretagne Loire, University of Angers, UFR SciencesAngers, France
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10
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Windley MJ, Vetter I, Lewis RJ, Nicholson GM. Lethal effects of an insecticidal spider venom peptide involve positive allosteric modulation of insect nicotinic acetylcholine receptors. Neuropharmacology 2017; 127:224-242. [PMID: 28396143 DOI: 10.1016/j.neuropharm.2017.04.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/28/2017] [Accepted: 04/06/2017] [Indexed: 01/17/2023]
Abstract
κ-Hexatoxins (κ-HXTXs) are a family of excitotoxic insect-selective neurotoxins from Australian funnel-web spiders that are lethal to a wide range of insects, but display no toxicity towards vertebrates. The prototypic κ-HXTX-Hv1c selectively blocks native and expressed cockroach large-conductance calcium-activated potassium (BKCa or KCa1.1) channels, but not their mammalian orthologs. Despite this potent and selective action on insect KCa1.1 channels, we found that the classical KCa1.1 blockers paxilline, charybdotoxin and iberiotoxin, which all block insect KCa1.1 channels, are not lethal in crickets. We therefore used whole-cell patch-clamp analysis of cockroach dorsal unpaired median (DUM) neurons to study the effects of κ-HXTX-Hv1c on sodium-activated (KNa), delayed-rectifier (KDR) and 'A-type' transient (KA) K+ channels. 1 μM κ-HXTX-Hv1c failed to significantly inhibit cockroach KNa and KDR channels, but did cause a 30 ± 7% saturating inhibition of KA channel currents, possibly via a Kv4 (Shal-like) action. However, this modest action at such a high concentration of κ-HXTX-Hv1c would indicate a different lethal target. Accordingly, we assessed the actions of κ-HXTX-Hv1c on neurotransmitter-gated ion channels in cockroach DUM neurons. We found that κ-HXTX-Hv1c failed to produce any major effects on GABAA or glutamate-Cl receptors but dramatically slowed nicotine-evoked ACh receptor (nAChR) current decay and reversed nAChR desensitization. These actions occurred without any alterations to nAChR current amplitude or the nicotine concentration-response curve, and are consistent with a positive allosteric modulation of nAChRs. κ-HXTX-Hv1c therefore represents the first venom peptide that selectively modulates insect nAChRs with a mode of action similar to the excitotoxic insecticide spinosyn A. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- Monique J Windley
- School of Life Sciences, University of Technology Sydney, Broadway, NSW 2007, Australia
| | - Irina Vetter
- Institute for Molecular Bioscience, University of Queensland, Brisbane St. Lucia, QLD 4072, Australia; School of Pharmacy, University of Queensland, Brisbane St. Lucia, QLD 4072, Australia
| | - Richard J Lewis
- Institute for Molecular Bioscience, University of Queensland, Brisbane St. Lucia, QLD 4072, Australia
| | - Graham M Nicholson
- School of Life Sciences, University of Technology Sydney, Broadway, NSW 2007, Australia.
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11
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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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12
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Arendt A, Baz ES, Stengl M. Functions of corazonin and histamine in light entrainment of the circadian pacemaker in the Madeira cockroach,Rhyparobia maderae. J Comp Neurol 2016; 525:1250-1272. [DOI: 10.1002/cne.24133] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 09/20/2016] [Accepted: 10/12/2016] [Indexed: 01/02/2023]
Affiliation(s)
- Andreas Arendt
- Animal Physiology, Department of Biology; University of Kassel; 34132 Kassel Germany
| | - El-Sayed Baz
- Animal Physiology, Department of Biology; University of Kassel; 34132 Kassel Germany
- Department of Zoology, Faculty of Science; Suez Canal University; 41522 Ismailia Governorate Egypt
| | - Monika Stengl
- Animal Physiology, Department of Biology; University of Kassel; 34132 Kassel Germany
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13
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Getahun MN, Thoma M, Lavista-Llanos S, Keesey I, Fandino RA, Knaden M, Wicher D, Olsson SB, Hansson BS. Intracellular regulation of the insect chemoreceptor complex impacts odour localization in flying insects. ACTA ACUST UNITED AC 2016; 219:3428-3438. [PMID: 27591307 DOI: 10.1242/jeb.143396] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 08/22/2016] [Indexed: 11/20/2022]
Abstract
Flying insects are well known for airborne odour tracking and have evolved diverse chemoreceptors. While ionotropic receptors (IRs) are found across protostomes, insect odorant receptors (ORs) have only been identified in winged insects. We therefore hypothesized that the unique signal transduction of ORs offers an advantage for odour localization in flight. Using Drosophila, we found expression and increased activity of the intracellular signalling protein PKC in antennal sensilla following odour stimulation. Odour stimulation also enhanced phosphorylation of the OR co-receptor Orco in vitro, while site-directed mutation of Orco or mutations in PKC subtypes reduced the sensitivity and dynamic range of OR-expressing neurons in vivo, but not IR-expressing neurons. We ultimately show that these mutations reduce competence for odour localization of flies in flight. We conclude that intracellular regulation of OR sensitivity is necessary for efficient odour localization, which suggests a mechanistic advantage for the evolution of the OR complex in flying insects.
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Affiliation(s)
- Merid N Getahun
- Max Planck Institute for Chemical Ecology, Department Evolutionary Neuroethology, Hans-Knöll-Strasse 8, Jena D-07745, Germany
| | - Michael Thoma
- Max Planck Institute for Chemical Ecology, Department Evolutionary Neuroethology, Hans-Knöll-Strasse 8, Jena D-07745, Germany
| | - Sofia Lavista-Llanos
- Max Planck Institute for Chemical Ecology, Department Evolutionary Neuroethology, Hans-Knöll-Strasse 8, Jena D-07745, Germany
| | - Ian Keesey
- Max Planck Institute for Chemical Ecology, Department Evolutionary Neuroethology, Hans-Knöll-Strasse 8, Jena D-07745, Germany
| | - Richard A Fandino
- Max Planck Institute for Chemical Ecology, Department Evolutionary Neuroethology, Hans-Knöll-Strasse 8, Jena D-07745, Germany
| | - Markus Knaden
- Max Planck Institute for Chemical Ecology, Department Evolutionary Neuroethology, Hans-Knöll-Strasse 8, Jena D-07745, Germany
| | - Dieter Wicher
- Max Planck Institute for Chemical Ecology, Department Evolutionary Neuroethology, Hans-Knöll-Strasse 8, Jena D-07745, Germany
| | - Shannon B Olsson
- Max Planck Institute for Chemical Ecology, Department Evolutionary Neuroethology, Hans-Knöll-Strasse 8, Jena D-07745, Germany
| | - Bill S Hansson
- Max Planck Institute for Chemical Ecology, Department Evolutionary Neuroethology, Hans-Knöll-Strasse 8, Jena D-07745, Germany
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Bradler C, Warren B, Bardos V, Schleicher S, Klein A, Kloppenburg P. Properties and physiological function of Ca2+-dependent K+ currents in uniglomerular olfactory projection neurons. J Neurophysiol 2016; 115:2330-40. [PMID: 26823514 DOI: 10.1152/jn.00840.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 01/27/2016] [Indexed: 11/22/2022] Open
Abstract
Ca(2+)-activated potassium currents [IK(Ca)] are an important link between the intracellular signaling system and the membrane potential, which shapes intrinsic electrophysiological properties. To better understand the ionic mechanisms that mediate intrinsic firing properties of olfactory uniglomerular projection neurons (uPNs), we used whole cell patch-clamp recordings in an intact adult brain preparation of the male cockroach Periplaneta americana to analyze IK(Ca) In the insect brain, uPNs form the principal pathway from the antennal lobe to the protocerebrum, where centers for multimodal sensory processing and learning are located. In uPNs the activation of IK(Ca) was clearly voltage and Ca(2+) dependent. Thus under physiological conditions IK(Ca) is strongly dependent on Ca(2+) influx kinetics and on the membrane potential. The biophysical characterization suggests that IK(Ca) is generated by big-conductance (BK) channels. A small-conductance (SK) channel-generated current could not be detected. IK(Ca) was sensitive to charybdotoxin (CTX) and iberiotoxin (IbTX) but not to apamin. The functional role of IK(Ca) was analyzed in occlusion experiments under current clamp, in which portions of IK(Ca) were blocked by CTX or IbTX. Blockade of IK(Ca) showed that IK(Ca) contributes significantly to intrinsic electrophysiological properties such as the action potential waveform and membrane excitability.
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Affiliation(s)
- Cathleen Bradler
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Ben Warren
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Viktor Bardos
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Sabine Schleicher
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Andreas Klein
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Peter Kloppenburg
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
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Hover S, King B, Hall B, Loundras EA, Taqi H, Daly J, Dallas M, Peers C, Schnettler E, McKimmie C, Kohl A, Barr JN, Mankouri J. Modulation of Potassium Channels Inhibits Bunyavirus Infection. J Biol Chem 2015; 291:3411-22. [PMID: 26677217 PMCID: PMC4751384 DOI: 10.1074/jbc.m115.692673] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Indexed: 11/06/2022] Open
Abstract
Bunyaviruses are considered to be emerging pathogens facilitated by the segmented nature of their genome that allows reassortment between different species to generate novel viruses with altered pathogenicity. Bunyaviruses are transmitted via a diverse range of arthropod vectors, as well as rodents, and have established a global disease range with massive importance in healthcare, animal welfare, and economics. There are no vaccines or anti-viral therapies available to treat human bunyavirus infections and so development of new anti-viral strategies is urgently required. Bunyamwera virus (BUNV; genus Orthobunyavirus) is the model bunyavirus, sharing aspects of its molecular and cellular biology with all Bunyaviridae family members. Here, we show for the first time that BUNV activates and requires cellular potassium (K(+)) channels to infect cells. Time of addition assays using K(+) channel modulating agents demonstrated that K(+) channel function is critical to events shortly after virus entry but prior to viral RNA synthesis/replication. A similar K(+) channel dependence was identified for other bunyaviruses namely Schmallenberg virus (Orthobunyavirus) as well as the more distantly related Hazara virus (Nairovirus). Using a rational pharmacological screening regimen, two-pore domain K(+) channels (K2P) were identified as the K(+) channel family mediating BUNV K(+) channel dependence. As several K2P channel modulators are currently in clinical use, our work suggests they may represent a new and safe drug class for the treatment of potentially lethal bunyavirus disease.
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Affiliation(s)
- Samantha Hover
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT
| | - Barnabas King
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH
| | - Bradley Hall
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT
| | - Eleni-Anna Loundras
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT
| | - Hussah Taqi
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT
| | - Janet Daly
- Veterinary Medicine and Science, University of Nottingham, Nottingham NG7 2RD
| | - Mark Dallas
- School of Pharmacy, University of Reading, Reading RG6 6AP, and
| | - Chris Peers
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT
| | - Esther Schnettler
- MRC-University of Glasgow Centre for Virus Research, Scotland, Glasgow G61 1QH, United Kingdom
| | - Clive McKimmie
- MRC-University of Glasgow Centre for Virus Research, Scotland, Glasgow G61 1QH, United Kingdom
| | - Alain Kohl
- MRC-University of Glasgow Centre for Virus Research, Scotland, Glasgow G61 1QH, United Kingdom
| | - John N Barr
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT,
| | - Jamel Mankouri
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT,
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Jones KK, Snelling EP, Watson AP, Seymour RS. Gas exchange and dive characteristics of the free-swimming backswimmer Anisops deanei. J Exp Biol 2015; 218:3478-86. [DOI: 10.1242/jeb.125047] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
ABSTRACT
Many aquatic insects utilise air bubbles on the surface of their bodies to supply O2 while they dive. The bubbles can simply store O2, as in the case of an ‘air store’, or they can act as a physical ‘gas gill’, extracting O2 from the water. Backswimmers of the genus Anisops augment their air store with O2 from haemoglobin cells located in the abdomen. The O2 release from the haemoglobin helps stabilise bubble volume, enabling backswimmers to remain near neutrally buoyant for a period of the dive. It is generally assumed that the backswimmer air store does not act as a gas gill and that gas exchange with the water is negligible. This study combines measurements of dive characteristics under different exotic gases (N2, He, SF6, CO) with mathematical modelling, to show that the air store of the backswimmer Anisops deanei does exchange gases with the water. Our results indicate that approximately 20% of O2 consumed during a dive is obtained directly from the water. Oxygen from the water complements that released from the haemoglobin, extending the period of near-neutral buoyancy and increasing dive duration.
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Affiliation(s)
- Karl K. Jones
- Department of Ecology and Environmental Science, School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Edward P. Snelling
- Department of Ecology and Environmental Science, School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Amy P. Watson
- Department of Ecology and Environmental Science, School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Roger S. Seymour
- Department of Ecology and Environmental Science, School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
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Abd-Ella A, Stankiewicz M, Mikulska K, Nowak W, Pennetier C, Goulu M, Fruchart-Gaillard C, Licznar P, Apaire-Marchais V, List O, Corbel V, Servent D, Lapied B. The Repellent DEET Potentiates Carbamate Effects via Insect Muscarinic Receptor Interactions: An Alternative Strategy to Control Insect Vector-Borne Diseases. PLoS One 2015; 10:e0126406. [PMID: 25961834 PMCID: PMC4427492 DOI: 10.1371/journal.pone.0126406] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 04/01/2015] [Indexed: 11/25/2022] Open
Abstract
Insect vector-borne diseases remain one of the principal causes of human mortality. In addition to conventional measures of insect control, repellents continue to be the mainstay for personal protection. Because of the increasing pyrethroid-resistant mosquito populations, alternative strategies to reconstitute pyrethroid repellency and knock-down effects have been proposed by mixing the repellent DEET (N,N-Diethyl-3-methylbenzamide) with non-pyrethroid insecticide to better control resistant insect vector-borne diseases. By using electrophysiological, biochemichal, in vivo toxicological techniques together with calcium imaging, binding studies and in silico docking, we have shown that DEET, at low concentrations, interacts with high affinity with insect M1/M3 mAChR allosteric site potentiating agonist effects on mAChRs coupled to phospholipase C second messenger pathway. This increases the anticholinesterase activity of the carbamate propoxur through calcium-dependent regulation of acetylcholinesterase. At high concentrations, DEET interacts with low affinity on distinct M1/M3 mAChR site, counteracting the potentiation. Similar dose-dependent dual effects of DEET have also been observed at synaptic mAChR level. Additionally, binding and in silico docking studies performed on human M1 and M3 mAChR subtypes indicate that DEET only displays a low affinity antagonist profile on these M1/M3 mAChRs. These results reveal a selective high affinity positive allosteric site for DEET in insect mAChRs. Finally, bioassays conducted on Aedes aegypti confirm the synergistic interaction between DEET and propoxur observed in vitro, resulting in a higher mortality of mosquitoes. Our findings reveal an unusual allosterically potentiating action of the repellent DEET, which involves a selective site in insect. These results open exciting research areas in public health particularly in the control of the pyrethroid-resistant insect-vector borne diseases. Mixing low doses of DEET and a non-pyrethroid insecticide will lead to improvement in the efficiency treatments thus reducing both the concentration of active ingredients and side effects for non-target organisms. The discovery of this insect specific site may pave the way for the development of new strategies essential in the management of chemical use against resistant mosquitoes.
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Affiliation(s)
- Aly Abd-Ella
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
- Plant Protection Department, Faculty of Agriculture, Assiut University, Assiut, Egypt
| | - Maria Stankiewicz
- Faculty of Biology and Environment Protection, N. Copernicus University, Torun, Poland
| | - Karolina Mikulska
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, N. Copernicus University, Torun, Poland
| | - Wieslaw Nowak
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, N. Copernicus University, Torun, Poland
| | - Cédric Pennetier
- Institut de Recherche pour le Développement, UMR 224 Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MiVEGEC), Montpellier, France
| | - Mathilde Goulu
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
| | - Carole Fruchart-Gaillard
- CEA, iBiTecS, Service d’Ingénierie Moléculaire des Protéines (SIMOPRO), Laboratoire de Toxinologie Moléculaire et Biotechnologie, Gif sur Yvette, France
| | - Patricia Licznar
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
| | - Véronique Apaire-Marchais
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
| | - Olivier List
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
| | - Vincent Corbel
- Institut de Recherche pour le Développement, UMR 224 Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MiVEGEC), Montpellier, France
- Department of Entomology, Faculty of Agriculture at Kamphaeng Saen, Kamphaeng Saen Campus, Kasetsart University, Nakhon Pathom, Thailand
| | - Denis Servent
- CEA, iBiTecS, Service d’Ingénierie Moléculaire des Protéines (SIMOPRO), Laboratoire de Toxinologie Moléculaire et Biotechnologie, Gif sur Yvette, France
| | - Bruno Lapied
- Laboratoire Récepteurs et Canaux Ioniques Membranaires (RCIM) UPRES EA 2647/USC INRA 1330, SFR 4207 QUASAV, Université d’Angers, UFR SCIENCES, Angers cedex, France
- * E-mail:
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Bende NS, Dziemborowicz S, Herzig V, Ramanujam V, Brown GW, Bosmans F, Nicholson GM, King GF, Mobli M. The insecticidal spider toxin SFI1 is a knottin peptide that blocks the pore of insect voltage-gated sodium channels via a large β-hairpin loop. FEBS J 2015; 282:904-20. [PMID: 25559770 DOI: 10.1111/febs.13189] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 12/15/2014] [Accepted: 12/27/2014] [Indexed: 11/27/2022]
Abstract
Spider venoms contain a plethora of insecticidal peptides that act on neuronal ion channels and receptors. Because of their high specificity, potency and stability, these peptides have attracted much attention as potential environmentally friendly insecticides. Although many insecticidal spider venom peptides have been isolated, the molecular target, mode of action and structure of only a small minority have been explored. Sf1a, a 46-residue peptide isolated from the venom of the tube-web spider Segesteria florentina, is insecticidal to a wide range of insects, but nontoxic to vertebrates. In order to investigate its structure and mode of action, we developed an efficient bacterial expression system for the production of Sf1a. We determined a high-resolution solution structure of Sf1a using multidimensional 3D/4D NMR spectroscopy. This revealed that Sf1a is a knottin peptide with an unusually large β-hairpin loop that accounts for a third of the peptide length. This loop is delimited by a fourth disulfide bond that is not commonly found in knottin peptides. We showed, through mutagenesis, that this large loop is functionally critical for insecticidal activity. Sf1a was further shown to be a selective inhibitor of insect voltage-gated sodium channels, consistent with its 'depressant' paralytic phenotype in insects. However, in contrast to the majority of spider-derived sodium channel toxins that function as gating modifiers via interaction with one or more of the voltage-sensor domains, Sf1a appears to act as a pore blocker.
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Affiliation(s)
- Niraj S Bende
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Qld, Australia
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19
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Ormerod KG, Hadden JK, Deady LD, Mercier AJ, Krans JL. Action of octopamine and tyramine on muscles of Drosophila melanogaster larvae. J Neurophysiol 2013; 110:1984-96. [DOI: 10.1152/jn.00431.2013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Octopamine (OA) and tyramine (TA) play important roles in homeostatic mechanisms, behavior, and modulation of neuromuscular junctions in arthropods. However, direct actions of these amines on muscle force production that are distinct from effects at the neuromuscular synapse have not been well studied. We utilize the technical benefits of the Drosophila larval preparation to distinguish the effects of OA and TA on the neuromuscular synapse from their effects on contractility of muscle cells. In contrast to the slight and often insignificant effects of TA, the action of OA was profound across all metrics assessed. We demonstrate that exogenous OA application decreases the input resistance of larval muscle fibers, increases the amplitude of excitatory junction potentials (EJPs), augments contraction force and duration, and at higher concentrations (10−5 and 10−4 M) affects muscle cells 12 and 13 more than muscle cells 6 and 7. Similarly, OA increases the force of synaptically driven contractions in a cell-specific manner. Moreover, such augmentation of contractile force persisted during direct muscle depolarization concurrent with synaptic block. OA elicited an even more profound effect on basal tonus. Application of 10−5 M OA increased synaptically driven contractions by ∼1.1 mN but gave rise to a 28-mN increase in basal tonus in the absence of synaptic activation. Augmentation of basal tonus exceeded any physiological stimulation paradigm and can potentially be explained by changes in intramuscular protein mechanics. Thus we provide evidence for independent but complementary effects of OA on chemical synapses and muscle contractility.
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Affiliation(s)
- Kiel G. Ormerod
- Department of Biological Sciences, Brock University, Saint Catharines, Ontario, Canada; and
| | - Julia K. Hadden
- Department of Neuroscience, Western New England University, Springfield, Massachusetts
| | - Lylah D. Deady
- Department of Neuroscience, Western New England University, Springfield, Massachusetts
| | - A. Joffre Mercier
- Department of Biological Sciences, Brock University, Saint Catharines, Ontario, Canada; and
| | - Jacob L. Krans
- Department of Neuroscience, Western New England University, Springfield, Massachusetts
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20
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Rates B, Prates MV, Verano-Braga T, da Rocha ÂP, Roepstorff P, Borges CL, Lapied B, Murillo L, Pimenta AM, Biondi I, De Lima ME. μ-Theraphotoxin-An1a: Primary structure determination and assessment of the pharmacological activity of a promiscuous anti-insect toxin from the venom of the tarantula Acanthoscurria natalensis (Mygalomorphae, Theraphosidae). Toxicon 2013; 70:123-34. [DOI: 10.1016/j.toxicon.2013.04.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 03/06/2013] [Accepted: 04/16/2013] [Indexed: 02/03/2023]
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21
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McKiernan EC. Effects of manipulating slowpoke calcium-dependent potassium channel expression on rhythmic locomotor activity in Drosophila larvae. PeerJ 2013; 1:e57. [PMID: 23638395 PMCID: PMC3628981 DOI: 10.7717/peerj.57] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 03/05/2013] [Indexed: 11/20/2022] Open
Abstract
Rhythmic motor behaviors are generated by networks of neurons. The sequence and timing of muscle contractions depends on both synaptic connections between neurons and the neurons' intrinsic properties. In particular, motor neuron ion currents may contribute significantly to motor output. Large conductance Ca(2+)-dependent K(+) (BK) currents play a role in action potential repolarization, interspike interval, repetitive and burst firing, burst termination and interburst interval in neurons. Mutations in slowpoke (slo) genes encoding BK channels result in motor disturbances. This study examined the effects of manipulating slo channel expression on rhythmic motor activity using Drosophila larva as a model system. Dual intracellular recordings from adjacent body wall muscles were made during spontaneous crawling-related activity in larvae expressing a slo mutation or a slo RNA interference construct. The incidence and duration of rhythmic activity in slo mutants were similar to wild-type control animals, while the timing of the motor pattern was altered. slo mutants showed decreased burst durations, cycle durations, and quiescence intervals, and increased duty cycles, relative to wild-type. Expressing slo RNAi in identified motor neurons phenocopied many of the effects observed in the mutant, including decreases in quiescence interval and cycle duration. Overall, these results show that altering slo expression in the whole larva, and specifically in motor neurons, changes the frequency of crawling activity. These results suggest an important role for motor neuron intrinsic properties in shaping the timing of motor output.
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Affiliation(s)
- Erin C McKiernan
- Instituto Tecnológico y de Estudios Superiores de Monterrey , Xochitepec, Morelos , México
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22
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Bende NS, Kang E, Herzig V, Bosmans F, Nicholson GM, Mobli M, King GF. The insecticidal neurotoxin Aps III is an atypical knottin peptide that potently blocks insect voltage-gated sodium channels. Biochem Pharmacol 2013; 85:1542-54. [PMID: 23473802 DOI: 10.1016/j.bcp.2013.02.030] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 02/24/2013] [Accepted: 02/27/2013] [Indexed: 12/26/2022]
Abstract
One of the most potent insecticidal venom peptides described to date is Aps III from the venom of the trapdoor spider Apomastus schlingeri. Aps III is highly neurotoxic to lepidopteran crop pests, making it a promising candidate for bioinsecticide development. However, its disulfide-connectivity, three-dimensional structure, and mode of action have not been determined. Here we show that recombinant Aps III (rAps III) is an atypical knottin peptide; three of the disulfide bridges form a classical inhibitor cystine knot motif while the fourth disulfide acts as a molecular staple that restricts the flexibility of an unusually large β hairpin loop that often houses the pharmacophore in this class of toxins. We demonstrate that the irreversible paralysis induced in insects by rAps III results from a potent block of insect voltage-gated sodium channels. Channel block by rAps III is voltage-independent insofar as it occurs without significant alteration in the voltage-dependence of channel activation or steady-state inactivation. Thus, rAps III appears to be a pore blocker that plugs the outer vestibule of insect voltage-gated sodium channels. This mechanism of action contrasts strikingly with virtually all other sodium channel modulators isolated from spider venoms that act as gating modifiers by interacting with one or more of the four voltage-sensing domains of the channel.
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Affiliation(s)
- Niraj S Bende
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia
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23
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Postembryonic developmental changes in photoreceptors of the stick insect Carausius morosus enhance the shift to an adult nocturnal life-style. J Neurosci 2013; 32:16821-31. [PMID: 23175835 DOI: 10.1523/jneurosci.2612-12.2012] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Optimization of sensory processing during development can be studied by using photoreceptors of hemimetabolous insects (with incomplete metamorphosis) as a research model. We have addressed this topic in the stick insect Carausius morosus, where retinal growth after hatching is accompanied by a diurnal-to-nocturnal shift in behavior, by recording from photoreceptors of first instar nymphs and adult animals using the patch-clamp method. In the nymphs, ommatidia were smaller and photoreceptors were on average 15-fold less sensitive to light than in adults. The magnitude of A-type K(+) current did not increase but the delayed rectifier doubled in adults compared with nymphs, the K(+) current densities being greater in the nymphs. By contrast, the density of light-induced current did not increase, although its magnitude increased 8.6-fold, probably due to the growth of microvilli. Nymph photoreceptors performed poorly, demonstrating a peak information rate (IR) of 2.9 ± 0.7 bits/s versus 34.1 ± 5.0 bits/s in adults in response to white-noise stimulation. Strong correlations were found between photoreceptor capacitance (a proxy for cell size) and IR, and between light sensitivity and IR, with larger and more sensitive photoreceptors performing better. In adults, IR peaked at light intensities matching irradiation from the evening sky. Our results indicate that biophysical properties of photoreceptors at each age stage and visual behavior are interdependent and that developmental improvement in photoreceptor performance may facilitate the switch from the diurnal to the safer nocturnal lifestyle. This also has implications for how photoreceptors achieve optimal performance.
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24
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SMN is required for sensory-motor circuit function in Drosophila. Cell 2012; 151:427-39. [PMID: 23063130 DOI: 10.1016/j.cell.2012.09.011] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 06/15/2012] [Accepted: 09/10/2012] [Indexed: 11/23/2022]
Abstract
Spinal muscular atrophy (SMA) is a lethal human disease characterized by motor neuron dysfunction and muscle deterioration due to depletion of the ubiquitous survival motor neuron (SMN) protein. Drosophila SMN mutants have reduced muscle size and defective locomotion, motor rhythm, and motor neuron neurotransmission. Unexpectedly, restoration of SMN in either muscles or motor neurons did not alter these phenotypes. Instead, SMN must be expressed in proprioceptive neurons and interneurons in the motor circuit to nonautonomously correct defects in motor neurons and muscles. SMN depletion disrupts the motor system subsequent to circuit development and can be mimicked by the inhibition of motor network function. Furthermore, increasing motor circuit excitability by genetic or pharmacological inhibition of K(+) channels can correct SMN-dependent phenotypes. These results establish sensory-motor circuit dysfunction as the origin of motor system deficits in this SMA model and suggest that enhancement of motor neural network activity could ameliorate the disease.
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25
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Salmela I, Immonen EV, Frolov R, Krause S, Krause Y, Vähäsöyrinki M, Weckström M. Cellular elements for seeing in the dark: voltage-dependent conductances in cockroach photoreceptors. BMC Neurosci 2012; 13:93. [PMID: 22867024 PMCID: PMC3472236 DOI: 10.1186/1471-2202-13-93] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 07/12/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The importance of voltage-dependent conductances in sensory information processing is well-established in insect photoreceptors. Here we present the characterization of electrical properties in photoreceptors of the cockroach (Periplaneta americana), a nocturnal insect with a visual system adapted for dim light. RESULTS Whole-cell patch-clamped photoreceptors had high capacitances and input resistances, indicating large photosensitive rhabdomeres suitable for efficient photon capture and amplification of small photocurrents at low light levels. Two voltage-dependent potassium conductances were found in the photoreceptors: a delayed rectifier type (KDR) and a fast transient inactivating type (KA). Activation of KDR occurred during physiological voltage responses induced by light stimulation, whereas KA was nearly fully inactivated already at the dark resting potential. In addition, hyperpolarization of photoreceptors activated a small-amplitude inward-rectifying (IR) current mediated at least partially by chloride. Computer simulations showed that KDR shapes light responses by opposing the light-induced depolarization and speeding up the membrane time constant, whereas KA and IR have a negligible role in the majority of cells. However, larger KA conductances were found in smaller and rapidly adapting photoreceptors, where KA could have a functional role. CONCLUSIONS The relative expression of KA and KDR in cockroach photoreceptors was opposite to the previously hypothesized framework for dark-active insects, necessitating further comparative work on the conductances. In general, the varying deployment of stereotypical K+ conductances in insect photoreceptors highlights their functional flexibility in neural coding.
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Affiliation(s)
- Iikka Salmela
- Department of Physics, University of Oulu, Oulu, Finland
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Windley MJ, Herzig V, Dziemborowicz SA, Hardy MC, King GF, Nicholson GM. Spider-venom peptides as bioinsecticides. Toxins (Basel) 2012; 4:191-227. [PMID: 22741062 PMCID: PMC3381931 DOI: 10.3390/toxins4030191] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 03/07/2012] [Accepted: 03/15/2012] [Indexed: 12/19/2022] Open
Abstract
Over 10,000 arthropod species are currently considered to be pest organisms. They are estimated to contribute to the destruction of ~14% of the world's annual crop production and transmit many pathogens. Presently, arthropod pests of agricultural and health significance are controlled predominantly through the use of chemical insecticides. Unfortunately, the widespread use of these agrochemicals has resulted in genetic selection pressure that has led to the development of insecticide-resistant arthropods, as well as concerns over human health and the environment. Bioinsecticides represent a new generation of insecticides that utilise organisms or their derivatives (e.g., transgenic plants, recombinant baculoviruses, toxin-fusion proteins and peptidomimetics) and show promise as environmentally-friendly alternatives to conventional agrochemicals. Spider-venom peptides are now being investigated as potential sources of bioinsecticides. With an estimated 100,000 species, spiders are one of the most successful arthropod predators. Their venom has proven to be a rich source of hyperstable insecticidal mini-proteins that cause insect paralysis or lethality through the modulation of ion channels, receptors and enzymes. Many newly characterized insecticidal spider toxins target novel sites in insects. Here we review the structure and pharmacology of these toxins and discuss the potential of this vast peptide library for the discovery of novel bioinsecticides.
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Affiliation(s)
- Monique J. Windley
- Neurotoxin Research Group, School of Medical & Molecular Biosciences, University of Technology, Sydney, Broadway NSW 2007, Australia; (M.J.W.); (S.A.D.)
| | - Volker Herzig
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland, 4072, Australia; (V.H.); (M.C.H.)
| | - Sławomir A. Dziemborowicz
- Neurotoxin Research Group, School of Medical & Molecular Biosciences, University of Technology, Sydney, Broadway NSW 2007, Australia; (M.J.W.); (S.A.D.)
| | - Margaret C. Hardy
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland, 4072, Australia; (V.H.); (M.C.H.)
| | - Glenn F. King
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland, 4072, Australia; (V.H.); (M.C.H.)
| | - Graham M. Nicholson
- Neurotoxin Research Group, School of Medical & Molecular Biosciences, University of Technology, Sydney, Broadway NSW 2007, Australia; (M.J.W.); (S.A.D.)
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Bodereau-Dubois B, List O, Calas-List D, Marques O, Communal PY, Thany SH, Lapied B. Transmembrane potential polarization, calcium influx, and receptor conformational state modulate the sensitivity of the imidacloprid-insensitive neuronal insect nicotinic acetylcholine receptor to neonicotinoid insecticides. J Pharmacol Exp Ther 2012; 341:326-39. [PMID: 22286500 DOI: 10.1124/jpet.111.188060] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neonicotinoid insecticides act selectively on insect nicotinic acetylcholine receptors (nAChRs). Recent studies revealed that their efficiency was altered by the phosphorylation/dephosphorylation process and the intracellular signaling pathway involved in the regulation of nAChRs. Using whole-cell patch-clamp electrophysiology adapted for dissociated cockroach dorsal unpaired median (DUM) neurons, we demonstrated that intracellular factors involved in the regulation of nAChR function modulated neonicotinoid sensitivity. DUM neurons were known to express two α-bungarotoxin-insensitive nAChR subtypes: nAChR1 and nAChR2. Whereas nAChR1 was sensitive to imidacloprid, nAChR2 was insensitive to this insecticide. Here, we demonstrated that, like nicotine, acetamiprid and clothianidin, other types of neonicotinoid insecticides, acted as agonists on the nAChR2 subtype. Using acetamiprid, we revealed that both steady-state depolarization and hyperpolarization affected nAChR2 sensitivity. The measurement of the input membrane resistance indicated that change in the acetamiprid-induced agonist activity was related to the receptor conformational state. Using cadmium chloride, ω-conotoxin GVIA, and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-acetamide (LOE 908), we found that inhibition of calcium influx through high voltage-activated calcium channels and transient receptor potential γ (TRPγ) activated by both depolarization and hyperpolarization increased nAChR2 sensitivity to acetamiprid. Finally, using N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W7), forskolin, and cAMP, we demonstrated that adenylyl cyclase sensitive to the calcium/calmodulin complex regulated internal cAMP concentration, which in turn modulated TRPγ function and nAChR2 sensitivity to acetamiprid. Similar TRPγ-induced modulatory effects were also obtained when clothianidin was tested. These findings bring insights into the signaling pathway modulating neonicotinoid efficiency and open novel strategies for optimizing insect pest control.
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Affiliation(s)
- Béatrice Bodereau-Dubois
- Laboratoire Récepteurs et Canaux Ioniques Membranaires, Faculté des Sciences, Université d'Angers, Angers, France
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Chorna T, Hasan G. The genetics of calcium signaling in Drosophila melanogaster. Biochim Biophys Acta Gen Subj 2011; 1820:1269-82. [PMID: 22100727 DOI: 10.1016/j.bbagen.2011.11.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 10/31/2011] [Accepted: 11/02/2011] [Indexed: 01/13/2023]
Abstract
BACKGROUND Genetic screens for behavioral and physiological defects in Drosophila melanogaster, helped identify several components of calcium signaling of which some, like the Trps, were novel. For genes initially identified in vertebrates, reverse genetic methods have allowed functional studies at the cellular and systemic levels. SCOPE OF REVIEW The aim of this review is to explain how various genetic methods available in Drosophila have been used to place different arms of Ca2+ signaling in the context of organismal development, physiology and behavior. MAJOR CONCLUSION Mutants generated in genes encoding a range of Ca2+ transport systems, binding proteins and enzymes affect multiple aspects of neuronal and muscle physiology. Some also affect the maintenance of ionic balance and excretion from malpighian tubules and innate immune responses in macrophages. Aspects of neuronal physiology affected include synaptic growth and plasticity, sensory transduction, flight circuit development and function. Genetic interaction screens have shown that mechanisms of maintaining Ca2+ homeostasis in Drosophila are cell specific and require a synergistic interplay between different intracellular and plasma membrane Ca2+ signaling molecules. GENERAL SIGNIFICANCE Insights gained through genetic studies of conserved Ca2+ signaling pathways have helped understand multiple aspects of fly physiology. The similarities between mutant phenotypes of Ca2+ signaling genes in Drosophila with certain human disease conditions, especially where homologous genes are causative factors, are likely to aid in the discovery of underlying disease mechanisms and help develop novel therapeutic strategies. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signalling.
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Affiliation(s)
- Tetyana Chorna
- National Center for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
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29
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Pflüger HJ, Field LH, Nishino H, Currie MJ. Neuromodulatory unpaired median neurons in the New Zealand tree weta, Hemideina femorata. JOURNAL OF INSECT PHYSIOLOGY 2011; 57:1420-1430. [PMID: 21810425 DOI: 10.1016/j.jinsphys.2011.07.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 07/08/2011] [Accepted: 07/13/2011] [Indexed: 05/31/2023]
Abstract
Wetas are ancient Gondwanan orthopterans (Anostostomatidae) with many species endemic to New Zealand. Like all Orthoptera they possess efferent neuromodulatory dorsal unpaired median (DUM) neurons, with bilaterally symmetrical axons, that are important components of motor networks. These neurons produce overshooting action potentials and are easily stimulated by a variety of external mechanosensory stimuli delivered to the body and appendages. In particular, stimulation of the antennae, mouth parts, tarsi and femora of the legs, abdomen, cerci and ovipositor is very effective in activating DUM neurons in the metathoracic ganglion of wetas. In addition, looming visual stimuli or light on-, light off-stimuli excite many metathoracic DUM neurons. These DUM sensory reflex pathways remain viable after the prothoracic to subesophageal connective is cut, whereas in locusts such reflex pathways are interrupted by the ablation. This suggests that, in wetas, sensory reflex pathways for DUM activation are organized in a less centralized fashion than in locusts, and may therefore reflect a plesiomorphic evolutionary state in the weta. In addition, many weta DUM neurons exhibit slow rhythmic bursting which also persists following the connective ablation.
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Affiliation(s)
- Hans-Joachim Pflüger
- University of Canterbury, School of Biological Sciences, Christchurch, New Zealand.
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Bucher D, Goaillard JM. Beyond faithful conduction: short-term dynamics, neuromodulation, and long-term regulation of spike propagation in the axon. Prog Neurobiol 2011; 94:307-46. [PMID: 21708220 PMCID: PMC3156869 DOI: 10.1016/j.pneurobio.2011.06.001] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 05/27/2011] [Accepted: 06/07/2011] [Indexed: 12/13/2022]
Abstract
Most spiking neurons are divided into functional compartments: a dendritic input region, a soma, a site of action potential initiation, an axon trunk and its collaterals for propagation of action potentials, and distal arborizations and terminals carrying the output synapses. The axon trunk and lower order branches are probably the most neglected and are often assumed to do nothing more than faithfully conducting action potentials. Nevertheless, there are numerous reports of complex membrane properties in non-synaptic axonal regions, owing to the presence of a multitude of different ion channels. Many different types of sodium and potassium channels have been described in axons, as well as calcium transients and hyperpolarization-activated inward currents. The complex time- and voltage-dependence resulting from the properties of ion channels can lead to activity-dependent changes in spike shape and resting potential, affecting the temporal fidelity of spike conduction. Neural coding can be altered by activity-dependent changes in conduction velocity, spike failures, and ectopic spike initiation. This is true under normal physiological conditions, and relevant for a number of neuropathies that lead to abnormal excitability. In addition, a growing number of studies show that the axon trunk can express receptors to glutamate, GABA, acetylcholine or biogenic amines, changing the relative contribution of some channels to axonal excitability and therefore rendering the contribution of this compartment to neural coding conditional on the presence of neuromodulators. Long-term regulatory processes, both during development and in the context of activity-dependent plasticity may also affect axonal properties to an underappreciated extent.
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Affiliation(s)
- Dirk Bucher
- The Whitney Laboratory and Department of Neuroscience, University of Florida, St. Augustine, FL 32080, USA.
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Anopheles gambiae mosquito isolated neurons: a new biological model for optimizing insecticide/repellent efficacy. J Neurosci Methods 2011; 200:68-73. [PMID: 21703304 DOI: 10.1016/j.jneumeth.2011.06.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 05/23/2011] [Accepted: 06/08/2011] [Indexed: 11/21/2022]
Abstract
To understand better the mode of action of insecticides and repellents used in vector-borne diseases control, we developed a new biological model based on mosquito neurons isolated from adults Anopheles gambiae heads. This cellular model is well adapted to multidisciplinary approaches: electrophysiology, pharmacology, molecular biology and biochemical assays. Using RT-PCR, we demonstrated that isolated neurons express the nicotinic acetylcholine receptor subunit α1 (Agα1 nAchR), two acetylcholinesterases (AChE-1 and AChE-2) and three voltage-gated ion channels required for membrane excitability (AgCav1, AgNav1 and AgKv1). In order to correlate the expression of the different transcripts, encoding functional AgNav channel, nAChR receptor and AChE enzymes detected by RT-PCR, with electrophysiological activity we used patch-clamp technique. We revealed that AgNav and AChE which are targeted by insecticide and/or repellent were sensitive to the pyrethroid permethrin and to the repellent DEET, respectively. In addition, using colorimetric method, we also showed that AChE was sensitive to the carbamate propoxur. These results indicated that this novel neuronal mosquito model will lead to molecular and functional characterization of insecticide/repellent targets and appears as a powerful tool to investigate the development of highly specific and effective strategies for disease vector control.
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Dose effects of oxaliplatin on persistent and transient Na+ conductances and the development of neurotoxicity. PLoS One 2011; 6:e18469. [PMID: 21494615 PMCID: PMC3072981 DOI: 10.1371/journal.pone.0018469] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Accepted: 03/01/2011] [Indexed: 12/13/2022] Open
Abstract
Background Oxaliplatin, a platinum-based chemotherapy utilised in the treatment of colorectal cancer, produces two forms of neurotoxicity- acute sensorimotor neuropathic symptoms and a dose-limiting chronic sensory neuropathy. Given that a Na+ channelopathy has been proposed as the mechanism underlying acute oxaliplatin-induced neuropathy, the present study aimed to determine specific mechanisms of Na+ channel dysfunction. Methodology/Principal Findings Specifically the function of transient and persistent Na+ currents were followed during treatment and were investigated in relation to oxaliplatin dose level. Eighteen patients were assessed before and after a single oxaliplatin infusion with motor and sensory axonal excitability studies performed on the median nerve at the wrist. While refractoriness (associated with Na+ channel inactivation) was significantly altered post-oxaliplatin infusion in both motor (Pre: 31.7±6.4%; Post: 68.8±14.5%; P≤.001) and sensory axons (Pre: 31.4±5.4%; Post: 21.4±5.5%; P<.05), strength-duration time constant (marker of persistent Na+ conductances) was not significantly altered post-infusion (Motor Pre: 0.395±0.01 ms; Post: 0.394±0.02 ms; NS; Sensory Pre:0.544±0.03 ms; Post: 0.535±0.05 ms; NS). However, changes in strength-duration time constant were significantly correlated with changes in refractoriness in motor and sensory axons (Motor correlation coefficient = −.65; P<.05; Sensory correlation coefficient = .67; P<.05). Conclusions/Significance It is concluded that the predominant effect of acute oxaliplatin exposure in human motor and sensory axons is mediated through changes in transient rather than persistent Na+ conductances. These findings are likely to have implications for the design and trial of neuroprotective strategies.
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Macmillan HA, Sinclair BJ. Mechanisms underlying insect chill-coma. JOURNAL OF INSECT PHYSIOLOGY 2011; 57:12-20. [PMID: 20969872 DOI: 10.1016/j.jinsphys.2010.10.004] [Citation(s) in RCA: 200] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Revised: 10/12/2010] [Accepted: 10/12/2010] [Indexed: 05/30/2023]
Abstract
At their critical thermal minimum (CT(min)) insects enter chill-coma, a reversible state where neuromuscular transmission and movement cease. The physiological mechanisms responsible for the insect CT(min) remain poorly understood despite the regular use of chill-coma onset and recovery as a means to assess evolved or acquired variation in low temperature tolerance. In this review, we summarize the use of chill-coma as a metric of thermal tolerance to date, and synthesise current knowledge on the nature and plasticity of lower thermal limits to present probable physiological mechanisms of cold-induced failure. Chill-coma is likely to be driven by an inability to maintain ionic homeostasis through the effects of temperature on ion-motive ATPases, ion channel gating mechanisms, and/or the lipid membrane, leading to a loss of nerve and muscle excitability.
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Affiliation(s)
- Heath A Macmillan
- Department of Biology, The University of Western Ontario, London, ON, N6A 5B7, Canada.
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34
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Dai A, Temporal S, Schulz DJ. Cell-specific patterns of alternative splicing of voltage-gated ion channels in single identified neurons. Neuroscience 2010; 168:118-29. [PMID: 20211705 DOI: 10.1016/j.neuroscience.2010.03.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 02/25/2010] [Accepted: 03/02/2010] [Indexed: 11/28/2022]
Abstract
CbNa(v) and CbIH encode channels that carry voltage-gated sodium and hyperpolarization activated cation currents respectively in the crab, Cancer borealis. We cloned and sequenced full length cDNAs for both CbNa(v) and CbIH and found nine different regions of alternative splicing for the CbNa(v) gene and four regions of alternative splicing for CbIH. We used RT-PCR to determine tissue-specific differences in splicing of both channel genes among cardiac muscle, skeletal muscle, brain, and stomatogastric ganglion (STG) tissue. We then examined the splice variant isoforms present in single, unambiguously identified neurons of the STG. We found cell-type specific patterns of alternative splicing for CbNa(v), indicating unique cell-specific pattern of post-transcriptional modification. Furthermore, we detected possible differences in cellular localization of alternatively spliced CbNa(v) transcripts; distinct mRNA isoforms are present between the cell somata and the axons of the neurons. In contrast, we found no qualitative differences among different cell types for CbIH variants present, although this analysis did not represent the full spectrum of all possible CbIH variants. CbIH mRNA was not detected in axon samples. Finally, although cell-type specific patterns of splicing were detected for CbNa(v), the same cell type within and between animals also displayed variability in which splice forms were detected. These results indicate that channel splicing is differentially regulated at the level of single neurons of the same neural network, providing yet another mechanism by which cell-specific neuronal output can be achieved.
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Affiliation(s)
- A Dai
- Department of Biological Sciences, University of Missouri, Columbia, MO, USA
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35
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Lavialle-Defaix C, Moignot B, Legros C, Lapied B. How Does Calcium-Dependent Intracellular Regulation of Voltage-Dependent Sodium Current Increase the Sensitivity to the Oxadiazine Insecticide Indoxacarb Metabolite Decarbomethoxylated JW062 (DCJW) in Insect Pacemaker Neurons? J Pharmacol Exp Ther 2010; 333:264-72. [DOI: 10.1124/jpet.109.163519] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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36
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Demmer H, Kloppenburg P. Intrinsic Membrane Properties and Inhibitory Synaptic Input of Kenyon Cells as Mechanisms for Sparse Coding? J Neurophysiol 2009; 102:1538-50. [DOI: 10.1152/jn.00183.2009] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The insect mushroom bodies (MBs) are multimodal signal processing centers and are essential for olfactory learning. Electrophysiological recordings from the MBs' principal component neurons, the Kenyon cells (KCs), showed a sparse representation of olfactory signals. It has been proposed that the intrinsic and synaptic properties of the KC circuitry combine to reduce the firing of action potentials and to generate relatively brief windows for synaptic integration in the KCs, thus causing them to operate as coincidence detectors. To better understand the ionic mechanisms that mediate the KC intrinsic firing properties, we used whole cell patch-clamp recordings from KCs in the adult, intact brain of Periplaneta americana to analyze voltage- and/or Ca2+-dependent inward ( ICa, INa) and outward currents [ IA, IK(V), IK,ST, IO(Ca)]. In general the currents had properties similar to those of currents in other insect neurons. Certain functional parameters of ICaand IO(Ca), however, had unusually high values, allowing them to assist sparse coding. ICahad a low-activation threshold and a very high current density compared with those of ICain other insect neurons. Together these parameters make ICasuitable for boosting and sharpening the excitatory postsynaptic potentials as reported in previous studies. IO(Ca)also had a large current density and a very depolarized activation threshold. In combination, the large ICaand IO(Ca)are likely to mediate the strong spike frequency adaptation. These intrinsic properties of the KCs are likely to be supported by their tonic, inhibitory synaptic input, which was revealed by specific GABA antagonists and which contributes significantly to the hyperpolarized membrane potential at rest.
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37
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Hodge JJL. Ion channels to inactivate neurons in Drosophila. Front Mol Neurosci 2009; 2:13. [PMID: 19750193 PMCID: PMC2741205 DOI: 10.3389/neuro.02.013.2009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Accepted: 08/11/2009] [Indexed: 02/05/2023] Open
Abstract
Ion channels are the determinants of excitability; therefore, manipulation of their levels and properties provides an opportunity for the investigator to modulate neuronal and circuit function. There are a number of ways to suppress electrical activity in Drosophila neurons, for instance, over-expression of potassium channels (i.e. Shaker Kv1, Shaw Kv3, Kir2.1 and DORK) that are open at resting membrane potential. This will result in increased potassium efflux and membrane hyperpolarisation setting resting membrane potential below the threshold required to fire action potentials. Alternatively over-expression of other channels, pumps or co-transporters that result in a hyperpolarised membrane potential will also prevent firing. Lastly, neurons can be inactivated by, disrupting or reducing the level of functional voltage-gated sodium (Nav1 paralytic) or calcium (Cav2 cacophony) channels that mediate the depolarisation phase of action potentials. Similarly, strategies involving the opposite channel manipulation should allow net depolarisation and hyperexcitation in a given neuron. These changes in ion channel expression can be brought about by the versatile transgenic (i.e. Gal4/UAS based) systems available in Drosophila allowing fine temporal and spatial control of (channel) transgene expression. These systems are making it possible to electrically inactivate (or hyperexcite) any neuron or neural circuit in the fly brain, and much like an exquisite lesion experiment, potentially elucidate whatever interesting behaviour or phenotype each network mediates. These techniques are now being used in Drosophila to reprogram electrical activity of well-defined circuits and bring about robust and easily quantifiable changes in behaviour, allowing different models and hypotheses to be rapidly tested.
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Affiliation(s)
- James J L Hodge
- Physiology and Pharmacology Department, University of Bristol Bristol, UK
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38
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Peron SP, Gabbiani F. Role of spike-frequency adaptation in shaping neuronal response to dynamic stimuli. BIOLOGICAL CYBERNETICS 2009; 100:505-520. [PMID: 19381681 PMCID: PMC2854487 DOI: 10.1007/s00422-009-0304-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Accepted: 03/16/2009] [Indexed: 05/27/2023]
Abstract
Spike-frequency adaptation is the reduction of a neuron's firing rate to a stimulus of constant intensity. In the locust, the Lobula Giant Movement Detector (LGMD) is a visual interneuron that exhibits rapid adaptation to both current injection and visual stimuli. Here, a reduced compartmental model of the LGMD is employed to explore adaptation's role in selectivity for stimuli whose intensity changes with time. We show that supralinearly increasing current injection stimuli are best at driving a high spike count in the response, while linearly increasing current injection stimuli (i.e., ramps) are best at attaining large firing rate changes in an adapting neuron. This result is extended with in vivo experiments showing that the LGMD's response to translating stimuli having a supralinear velocity profile is larger than the response to constant or linearly increasing velocity translation. Furthermore, we show that the LGMD's preference for approaching versus receding stimuli can partly be accounted for by adaptation. Finally, we show that the LGMD's adaptation mechanism appears well tuned to minimize sensitivity for the level of basal input.
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Affiliation(s)
- Simon Peter Peron
- Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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Peron S, Zordan MA, Magnabosco A, Reggiani C, Megighian A. From action potential to contraction: neural control and excitation-contraction coupling in larval muscles of Drosophila. Comp Biochem Physiol A Mol Integr Physiol 2009; 154:173-83. [PMID: 19427393 DOI: 10.1016/j.cbpa.2009.04.626] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 04/16/2009] [Accepted: 04/22/2009] [Indexed: 11/17/2022]
Abstract
The neuromuscular system of Drosophila melanogaster has been studied for many years for its relative simplicity and because of the genetic and molecular versatilities. Three main types of striated muscles are present in this dipteran: fibrillar muscles, tubular muscles and supercontractile muscles. The visceral muscles in adult flies and the body wall segmental muscles in embryos and larvae belong to the group of supercontractile muscles. Larval body wall muscles have been the object of detailed studies as a model for neuromuscular junction function but have received much less attention with respect to their mechanical properties and to the control of contraction. In this review we wish to assess available information on the physiology of the Drosophila larval muscular system. Our aim is to establish whether this system has the requisites to be considered a good model in which to perform a functional characterization of Drosophila genes, with a known muscular expression, as well as Drosophila homologs of human genes, the dysfunction of which, is known to be associated with human hereditary muscle pathologies.
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Affiliation(s)
- Samantha Peron
- Department of Anatomy and Physiology, University of Padua, Italy
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40
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Chang C, Shen WK, Wang TT, Lin YH, Hsu EL, Dai SM. A novel amino acid substitution in a voltage-gated sodium channel is associated with knockdown resistance to permethrin in Aedes aegypti. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2009; 39:272-278. [PMID: 19171193 DOI: 10.1016/j.ibmb.2009.01.001] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Revised: 12/29/2008] [Accepted: 01/03/2009] [Indexed: 05/26/2023]
Abstract
To identify pertinent mutations associated with knockdown resistance to permethrin, the entire coding sequence of the voltage-gated sodium channel gene Aa-para was sequenced and analyzed from a Per-R strain with 190-fold resistance to permethrin and two susceptible strains of Aedes aegypti. The longest transcript, a 6441bp open reading frame, encodes 2147 amino acid residues with an estimated molecular mass of 241kDa. A total of 33 exons were found in the Aa-para gene over 293kb of genomic DNA. Three previously unreported optional exons were identified. The first two exons, m and n, were located within the intracellular domain I/II, and the third, f', was found within the II/III linkers. The two mutually exclusive exons, d and l, were the only alternative exons in all the cDNA clones sequenced in this study. The most distinct finding was a novel amino acid substitution mutation, D1794Y, located within the extracellular linker between IVS5 and IVS6, which is concurrent with the known V1023G mutation in Aa-para of the Per-R strain. The high frequency and coexistence of the two mutations in the Per-R strain suggest that they might exert a synergistic effect to provide the knockdown resistance to permethrin. Furthermore, both cDNA and genomic DNA data from the same individual mosquitoes have demonstrated that RNA editing was not involved in amino acid substitutions of the Per-R strain.
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Affiliation(s)
- Cheng Chang
- Biotechnology Center, National Chung-Hsing University, Taichung, Taiwan, ROC
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41
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Peron S, Gabbiani F. Spike frequency adaptation mediates looming stimulus selectivity in a collision-detecting neuron. Nat Neurosci 2009; 12:318-26. [PMID: 19198607 DOI: 10.1038/nn.2259] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 12/11/2008] [Indexed: 11/09/2022]
Abstract
How active membrane conductance dynamics tunes neurons for specific time-varying stimuli remains poorly understood. We studied the biophysical mechanisms by which spike frequency adaptation shapes visual stimulus selectivity in an identified visual interneuron of the locust. The lobula giant movement detector (LGMD) responds preferentially to objects approaching on a collision course with the locust. Using calcium imaging, pharmacology and modeling, we show that spike frequency adaptation in the LGMD is mediated by a Ca(2+)-dependent potassium conductance closely resembling those associated with 'small-conductance' (SK) channels. Intracellular block of this conductance minimally affected the LGMD's response to approaching stimuli, but substantially increased its response to translating ones. Thus, spike frequency adaptation contributes to the neuron's tuning by selectively decreasing its responses to nonpreferred stimuli. Our results identify a new mechanism by which spike frequency adaptation may tune visual neurons to behaviorally relevant stimuli.
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Affiliation(s)
- Simon Peron
- Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
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Tyramine as an independent transmitter and a precursor of octopamine in the locust central nervous system: An immunocytochemical study. J Comp Neurol 2009; 512:433-52. [DOI: 10.1002/cne.21911] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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43
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Kosakai K, Satoh K, Yoshino M. Octopaminergic modulation of the single Ca2+ channel currents in Kenyon cells isolated from the mushroom body of the cricket brain. JOURNAL OF INSECT PHYSIOLOGY 2008; 54:1479-1486. [PMID: 18761015 DOI: 10.1016/j.jinsphys.2008.08.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Revised: 07/30/2008] [Accepted: 08/04/2008] [Indexed: 05/26/2023]
Abstract
Octopamine plays an important role in mediating reward signals in olfactory learning and memory formation in insect. However, its target molecules and signaling pathways are still unknown. In this study, we investigated the effects of octopamine on the voltage-activated Ca2+ channels expressed in native Kenyon cells isolated from the mushroom body of the cricket (Gryllus bimaculatus) brain. The cell-attached patch clamp recordings with 100 mM Ba2+ outside showed the presence of dihydropyridine (DHP) sensitive L-type Ca2+ channels with a single channel conductance of approximately 21+/-2 pS (n=12). The open probability (NPo) of single Ca2+ channel currents decreased by about 29+/-7% (n=6) by bath application of 10 microM octopamine. Octopamine-induced decrease in Po was imitated by bath application of 8-Br-cAMP, a membrane-permeable cAMP analog. Pre-treatment of Kenyon cells with the octopamine receptor antagonist phentolamine blocked the inhibitory effect of octopamine on Ca2+ channels. Pre-treatment of Kenyon cells with H-89, a selective inhibitor of cAMP-dependent protein kinase (PKA) attenuated the inhibitory effect of bath applied octopamine on Ca2+ channels. These results indicate that DHP-sensitive L-type Ca2+ channel is a target protein for octopamine and its modulation is mediated via cAMP and PKA-dependent signaling pathways in freshly isolated Kenyon cell in the cricket G. bimaculatus.
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Affiliation(s)
- K Kosakai
- Laboratory of Biology, Tokyo Gakugei University Senior High School, Setagaya, Tokyo 154-0002, Japan
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44
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45
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Gunning SJ, Maggio F, Windley MJ, Valenzuela SM, King GF, Nicholson GM. The Janus-faced atracotoxins are specific blockers of invertebrate K(Ca) channels. FEBS J 2008; 275:4045-59. [PMID: 18625007 DOI: 10.1111/j.1742-4658.2008.06545.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The Janus-faced atracotoxins are a unique family of excitatory peptide toxins that contain a rare vicinal disulfide bridge. Although lethal to a wide range of invertebrates, their molecular target has remained enigmatic for almost a decade. We demonstrate here that these toxins are selective, high-affinity blockers of invertebrate Ca(2+)-activated K(+) (K(Ca)) channels. Janus-faced atracotoxin (J-ACTX)-Hv1c, the prototypic member of this toxin family, selectively blocked K(Ca) channels in cockroach unpaired dorsal median neurons with an IC(50) of 2 nm, but it did not significantly affect a wide range of other voltage-activated K(+), Ca(2+) or Na(+) channel subtypes. J-ACTX-Hv1c blocked heterologously expressed cockroach large-conductance Ca(2+)-activated K(+) (pSlo) channels without a significant shift in the voltage dependence of activation. However, the block was voltage-dependent, indicating that the toxin probably acts as a pore blocker rather than a gating modifier. The molecular basis of the insect selectivity of J-ACTX-Hv1c was established by its failure to significantly inhibit mouse mSlo currents (IC(50) approximately 10 mum) and its lack of activity on rat dorsal root ganglion neuron K(Ca) channel currents. This study establishes the Janus-faced atracotoxins as valuable tools for the study of invertebrate K(Ca) channels and suggests that K(Ca) channels might be potential insecticide targets.
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Affiliation(s)
- Simon J Gunning
- Neurotoxin Research Group, Department of Medical & Molecular Biosciences, University of Technology, Sydney, NSW, Australia
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46
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Olson RO, Liu Z, Nomura Y, Song W, Dong K. Molecular and functional characterization of voltage-gated sodium channel variants from Drosophila melanogaster. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2008; 38:604-10. [PMID: 18405837 PMCID: PMC3056540 DOI: 10.1016/j.ibmb.2008.01.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2007] [Revised: 12/20/2007] [Accepted: 01/24/2008] [Indexed: 05/12/2023]
Abstract
Extensive alternative splicing and RNA editing have been documented for the transcript of DmNa(V) (formerly para), the sole sodium channel gene in Drosophila melanogaster. However, the functional consequences of these post-transcriptional modifications are not well understood. In this study we isolated 64 full-length DmNa(V) cDNA clones from D. melanogaster adults. Based on the usage of 11 alternative exons, 64 clones could be grouped into 29 splice types. When expressed in Xenopus oocytes, 33 DmNa(V) variants generated sodium currents large enough for functional characterization. Among these variants, DmNa(V)5-1 and DmNa(V)7-1 channels activated at the most hyperpolarizing potentials, whereas DmNa(V)1-6 and DmNa(V)19 channels activated at the most depolarizing membrane potentials. We identified an A-to-I editing event in DmNa(V)5-1 that is responsible for its uniquely low-voltage-dependent activation. The wide range of voltage dependence of gating properties exhibited by DmNa(V) variants represents a rich resource for future studies to determine the role of DmNa(V) in regulating sodium channel gating, pharmacology, and neuronal excitability in insects.
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Affiliation(s)
| | | | | | | | - Ke Dong
- Corresponding author. Tel.: + 1 517 432 2034; fax: +1 517 353 5598. (K. Dong)
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Husch A, Hess S, Kloppenburg P. Functional Parameters of Voltage-Activated Ca2+Currents From Olfactory Interneurons in the Antennal Lobe ofPeriplaneta americana. J Neurophysiol 2008; 99:320-32. [DOI: 10.1152/jn.00719.2007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Toward our goal to better understand the physiological parameters that mediate olfactory information processing on the cellular level, voltage-activated calcium currents ( ICa) in olfactory interneurons of the antennal lobe from adult cockroaches were analyzed under two conditions: 1) in acutely dissociated cells (in vitro) and 2) in an intact brain preparation (in situ). The study included an analysis of modulatory effects of potential inorganic and organic Ca2+channel blockers. ICawas isolated and identified using pharmacological, voltage, and ion substitution protocols. ICaconsisted of two components: transient and sustained. The decay of the transient component was largely Ca2+dependent. In vitro, ICahad an activation threshold of −50 mV with a maximal peak current at −7 mV and a half-maximal voltage ( V0.5act) for tail-current activation of −18 mV. In situ these parameters were significantly shifted to more depolarized membrane potentials: ICaactivated at −40 mV with a maximal peak current at 8 mV and a V0.5actfor tail-current activation of −11 mV. The sensitivity of ICato the divalent cations Cd2+, Co2+, and Ni2+was dose dependent. The most effective blocker was Cd2+with an IC50of 10−5M followed by Ni2+(IC50= 3.13 × 10−3M) and Co2+(IC50= 1.06 × 10−3M). The organic channel blockers verapamil, diltiazem, and nifedipine also blocked ICain a dose-dependent way and had differential effects on the current waveform. Verapamil blocked ICawith an IC50of 1.5 × 10−4M and diltiazem had an IC50of 2.87 × 10−4M. Nifedipine blocked ICaby 33% at a concentration of 10−4M.
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48
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Sheeba V, Gu H, Sharma VK, O'Dowd DK, Holmes TC. Circadian- and light-dependent regulation of resting membrane potential and spontaneous action potential firing of Drosophila circadian pacemaker neurons. J Neurophysiol 2007; 99:976-88. [PMID: 18077664 DOI: 10.1152/jn.00930.2007] [Citation(s) in RCA: 161] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ventral lateral neurons (LNvs) of adult Drosophila brain express oscillating clock proteins and regulate circadian behavior. Whole cell current-clamp recordings of large LNvs in freshly dissected Drosophila whole brain preparations reveal two spontaneous activity patterns that correlate with two underlying patterns of oscillating membrane potential: tonic and burst firing of sodium-dependent action potentials. Resting membrane potential and spontaneous action potential firing are rapidly and reversibly regulated by acute changes in light intensity. The LNv electrophysiological light response is attenuated, but not abolished, in cry(b) mutant flies hypomorphic for the cell-autonomous light-sensing protein CRYPTOCHROME. The electrical activity of the large LNv is circadian regulated, as shown by significantly higher resting membrane potential and frequency of spontaneous action potential firing rate and burst firing pattern during circadian subjective day relative to subjective night. The circadian regulation of membrane potential, spontaneous action potential firing frequency, and pattern of Drosophila large LNvs closely resemble mammalian circadian neuron electrical characteristics, suggesting a general evolutionary conservation of both physiological and molecular oscillator mechanisms in pacemaker neurons.
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Affiliation(s)
- Vasu Sheeba
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697, USA
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Gautier H, Auger J, Legros C, Lapied B. Calcium-activated potassium channels in insect pacemaker neurons as unexpected target site for the novel fumigant dimethyl disulfide. J Pharmacol Exp Ther 2007; 324:149-59. [PMID: 17942746 DOI: 10.1124/jpet.107.128694] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dimethyl disulfide (DMDS), a plant-derived insecticide, is a promising fumigant as a substitute for methyl bromide. To further understand the mode of action of DMDS, we examined its effect on cockroach octopaminergic neurosecretory cells, called dorsal unpaired median (DUM) neurons, using whole-cell patch-clamp technique, calcium imaging and antisense oligonucleotide strategy. At low concentration (1 microM), DMDS modified spontaneous regular spike discharge into clear bursting activity associated with a decrease of the amplitude of the afterhyperpolarization. This effect led us to suspect alterations of calcium-activated potassium currents (IKCa) and [Ca(2+)](i) changes. We showed that DMDS reduced amplitudes of both peak transient and sustained components of the total potassium current. IKCa was confirmed as a target of DMDS by using iberiotoxin, cadmium chloride, and pSlo antisense oligonucleotide. In addition, we showed that DMDS induced [Ca(2+)](i) rise in Fura-2-loaded DUM neurons. Using calcium-free solution, and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxy-phenyl)ethyl]-acetamide (LOE 908) [an inhibitor of transient receptor potential (TRP)gamma], we demonstrated that TRPgamma initiated calcium influx. By contrast, omega-conotoxin GVIA (an inhibitor of N-type high-voltage-activated calcium channels), did not affect the DMDS-induced [Ca(2+)](i) rise. Finally, the participation of the calcium-induced calcium release mechanism was investigated using thapsigargin, caffeine, and ryanodine. Our study revealed that DMDS-induced elevation in [Ca(2+)](i) modulated IKCa in an unexpected bell-shaped manner via intracellular calcium. In conclusion, DMDS affects multiple targets, which could be an effective way to improve pest control efficacy of fumigation.
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Affiliation(s)
- Hélène Gautier
- Unité Propre de Recherche et de l'Enseignement Supérieur, Equipe d'Accueil 2647/USC Institut National de la Recherche Agronomique, Université d'Angers, Unité de Formation et de Recherche Sciences, Angers cedex, France
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Rose U, Derst C, Wanischeck M, Marinc C, Walther C. Properties and possible function of a hyperpolarisation-activated chloride current in Drosophila. J Exp Biol 2007; 210:2489-500. [PMID: 17601953 DOI: 10.1242/jeb.006361] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
SUMMARY
A chloride current, ICl,H, slowly activating on hyperpolarisation was investigated in Drosophila melanogaster larval muscles using the two-electrode voltage clamp. Sizeable currents were observed after the intracellular chloride concentration([Cl–]i) had been elevated by diffusion of Cl– from the electrodes. The time course of ICl,H was rather variable and required two exponentials to be accurately described. The reversal potential, –40 to –20 mV in Cl–-loaded fires, shifted on lowering external[Cl–] in the positive direction. Steady-state activation of ICl,H was characterised by V0.5 of≈–120 mV and a slope factor, k, of ≈10 mV at a[Cl–]i ≈35 mmol l–1. Raising[Cl–]i to ≈50 mmol l–1 caused a negative shift of V0.5 equivalent to the change of ECl and led to a nearly threefold increase in maximal steady-state conductance. ICl,H was resistant to 10 mmol l–1 Zn2+ and 1 mmol l–1Cd2+ but was greatly reduced by 1 mmol l–19-anthracenecarboxylic acid (9-AC). ICl,H was affected by changes of extracellular pH and increased on lowering extracellular osmolality. 9-AC also decreased muscle fibre resting conductance by approximately 20% and increased muscle contractions. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis confirmed the expression of all three ClC genes in muscle, and immunohistochemistry indicated location of Drosophila melanogaster chloride channel-2(DmClC-2) at the Z-lines. We conclude that DmClC-2 accounts for the channels underlying ICl,H, and in part for the resting chloride conductance. DmClC-2 may serve general homeostatic mechanisms such as pH- and osmo-regulation or may support muscle function on high motor activity or during a particular neurohormonal state of the animal.
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Affiliation(s)
- Uwe Rose
- Institute of Neurobiology, University Ulm, Albert-Einstein-Allee 11, Ulm 89160, Germany.
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