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Cens T, Chavanieu A, Bertaud A, Mokrane N, Estaran S, Roussel J, Ménard C, De Jesus Ferreira M, Guiramand J, Thibaud J, Cohen‐Solal C, Rousset M, Rolland V, Vignes M, Charnet P. Molecular Targets of Neurotoxic Insecticides in
Apis mellifera. European J Org Chem 2022. [DOI: 10.1002/ejoc.202101531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Thierry Cens
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Alain Chavanieu
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Anaïs Bertaud
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Nawfel Mokrane
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Sébastien Estaran
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Julien Roussel
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Claudine Ménard
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | | | - Janique Guiramand
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Jean‐Baptiste Thibaud
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Catherine Cohen‐Solal
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Matthieu Rousset
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Valérie Rolland
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Michel Vignes
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
| | - Pierre Charnet
- Institut des Biomolécules Max Mousseron Université de Montpellier, CNRS, ENSCM 1919 Route de Mende 34293 Montpellier France
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Paten AM, Colin T, Coppin CW, Court LN, Barron AB, Oakeshott JG, Morgan MJ. Non-additive gene interactions underpin molecular and phenotypic responses in honey bee larvae exposed to imidacloprid and thymol. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 814:152614. [PMID: 34963587 DOI: 10.1016/j.scitotenv.2021.152614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 12/17/2021] [Accepted: 12/18/2021] [Indexed: 06/14/2023]
Abstract
Understanding the cumulative risk of chemical mixtures at environmentally realistic concentrations is a key challenge in honey bee ecotoxicology. Ecotoxicogenomics, including transcriptomics, measures responses in individual organisms at the molecular level which can provide insights into the mechanisms underlying phenotypic responses induced by one or more stressors and link impacts on individuals to populations. Here, fifth instar honey bee larvae were sampled from a previously reported field experiment exploring the phenotypic impacts of environmentally realistic chronic exposures of the pesticide imidacloprid (5 μg.kg-1 for six weeks) and the acaricide thymol (250 g.kg-1 applied via Apiguard gel in-hive for four weeks), both separately and in combination. RNA-seq was used to discover individual and interactive chemical effects on larval gene expression and to uncover molecular mechanisms linked to reported adult and colony phenotypes. The separate and combined treatments had distinct gene expression profiles which represented differentially affected signaling and metabolic pathways. The molecular signature of the mixture was characterised by additive interactions in canonical stress responses associated with oxidative stress and detoxification, and non-additive interactions in secondary responses including developmental, neurological, and immune pathways. Novel emergent impacts on eye development genes correlated with long-term defects in visual learning performance as adults. This is consistent with these chemicals working through independent modes of action that combine to impact common downstream pathways, and highlights the importance of establishing mechanistic links between molecular and phenotypic responses when predicting effects of chemical mixtures on ecologically relevant population outcomes.
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Affiliation(s)
- Amy M Paten
- Land and Water, CSIRO, Black Mountain, Canberra, ACT 2601, Australia.
| | - Théotime Colin
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Chris W Coppin
- Land and Water, CSIRO, Black Mountain, Canberra, ACT 2601, Australia.
| | - Leon N Court
- Land and Water, CSIRO, Black Mountain, Canberra, ACT 2601, Australia.
| | - Andrew B Barron
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia.
| | - John G Oakeshott
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia; Applied Biosciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Matthew J Morgan
- Land and Water, CSIRO, Black Mountain, Canberra, ACT 2601, Australia.
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3
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Henry C, Cens T, Charnet P, Cohen-Solal C, Collet C, van-Dijk J, Guiramand J, de Jésus-Ferreira MC, Menard C, Mokrane N, Roussel J, Thibault JB, Vignes M, Rousset M. Heterogeneous expression of GABA receptor-like subunits LCCH3 and GRD reveals functional diversity of GABA receptors in the honeybee Apis mellifera. Br J Pharmacol 2020; 177:3924-3940. [PMID: 32436264 DOI: 10.1111/bph.15135] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 04/24/2020] [Accepted: 05/09/2020] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND AND PURPOSE Despite a growing awareness, annual losses of honeybee colonies worldwide continue to reach threatening levels for food safety and global biodiversity. Among the biotic and abiotic stresses probably responsible for these losses, pesticides, including those targeting ionotropic GABA receptors, are one of the major drivers. Most insect genomes include the ionotropic GABA receptor subunit gene, Rdl, and two GABA-like receptor subunit genes, Lcch3 and Grd. Most studies have focused on Rdl which forms homomeric GABA-gated chloride channels, and a complete analysis of all possible molecular combinations of GABA receptors is still lacking. EXPERIMENTAL APPROACH We cloned the Rdl, Grd, and Lcch3 genes of Apis mellifera and systematically characterized the resulting GABA receptors expressed in Xenopus oocytes, using electrophysiological assays, fluorescence microscopy and co-immunoprecipitation techniques. KEY RESULTS The cloned subunits interacted with each other, forming GABA-gated heteromeric channels with particular properties. Strikingly, these heteromers were always more sensitive than AmRDL homomer to all the pharmacological agents tested. In particular, when expressed together, Grd and Lcch3 form a non-selective cationic channel that opens at low concentrations of GABA and with sensitivity to insecticides similar to that of homomeric Rdl channels. CONCLUSION AND IMPLICATIONS For off-target species like the honeybee, chronic sublethal exposure to insecticides constitutes a major threat. At these concentration ranges, homomeric RDL receptors may not be the most pertinent target to study and other ionotropic GABA receptor subtypes should be considered in order to understand more fully the molecular mechanisms of sublethal toxicity to insecticides.
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Affiliation(s)
| | - Thierry Cens
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Pierre Charnet
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | | | - Claude Collet
- UR 406 Abeilles et Environnement, INRAE, Avignon Cedex 9, France
| | | | | | | | - Claudine Menard
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Nawfel Mokrane
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Julien Roussel
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | | | - Michel Vignes
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Matthieu Rousset
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
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Mustard JA, Jones L, Wright GA. GABA signaling affects motor function in the honey bee. JOURNAL OF INSECT PHYSIOLOGY 2020; 120:103989. [PMID: 31805284 DOI: 10.1016/j.jinsphys.2019.103989] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 10/26/2019] [Accepted: 11/29/2019] [Indexed: 06/10/2023]
Abstract
GABA is the most common inhibitory neurotransmitter in both vertebrate and invertebrate nervous systems. In insects, inhibition plays important roles at the neuromuscular junction, in the regulation of central pattern generators, and in the modulation of information in higher brain processing centers. Additionally, increasing our understanding of the functions of GABA is important since GABAA receptors are the targets of several classes of pesticides. To investigate the role of GABA in motor function, honey bee foragers were injected with GABA or with agonists or antagonists specific for either GABAA or GABAB receptors. Compounds that activated either type of GABA receptor decreased activity levels. Bees injected with the GABAA receptor antagonist picrotoxin lost the ability to right themselves, whereas blockade of GABAB receptors led to increases in grooming. Injection with antagonists of either GABAA or GABAB receptors resulted in an increase in extended wing behavior, during which bees kept their wings out at right angles to their body rather than folded along their back. These data suggest that the GABA receptor types play distinct roles in behavior and that GABA may affect behavior at several different levels.
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Affiliation(s)
- Julie A Mustard
- Department of Biology, University of Texas Rio Grande Valley, Brownsville, TX 78520, USA.
| | - Lisa Jones
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Geraldine A Wright
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom; Department of Zoology, University of Oxford, Oxford OX1 3SZ, United Kingdom
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5
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Ugajin A, Uchiyama H, Miyata T, Sasaki T, Yajima S, Ono M. Identification and initial characterization of novel neural immediate early genes possibly differentially contributing to foraging-related learning and memory processes in the honeybee. INSECT MOLECULAR BIOLOGY 2018; 27:154-165. [PMID: 29096051 DOI: 10.1111/imb.12355] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Despite possessing a limited number of neurones compared to vertebrates, honeybees show remarkable learning and memory performance, an example being 'dance communication'. In this phenomenon, foraging honeybees learn the location of a newly discovered food source and transmit the information to nestmates by symbolic abdomen vibrating behaviour, leading to navigation of nestmates to the new food source. As an initial step toward understanding the detailed molecular mechanisms underlying the sophisticated learning and memory performance of the honeybee, we focused on the neural immediate early genes (IEGs), which are specific genes quickly transcribed after neural activity without de novo protein synthesis. Although these have been reported to play an essential role in learning and memory processes in vertebrates, far fewer studies have been performed in insects in this regard. From RNA-sequencing analysis and subsequent assays, we identified three genes, Src homology 3 (SH3) domain binding kinase, family with sequence similarity 46 and GB47136, as novel neural IEGs in the honeybee. Foragers and/or orientating bees, which fly around their hives to memorize the positional information, showed induced expression of these IEGs in the mushroom body, a higher-order centre essential for learning and memory, indicating a possible role for the novel IEGs in foraging-related learning and memory processes in the honeybee.
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Affiliation(s)
- A Ugajin
- Laboratory of Applied Entomology and Zoology, Graduate School of Agriculture, Tamagawa University, Machida, Tokyo, Japan
| | - H Uchiyama
- NODAI Genome Research Center, Tokyo University of Agriculture, Setagaya-ku, Tokyo, Japan
| | - T Miyata
- Department of Agri-Production Sciences, College of Agriculture, Tamagawa University, Machida, Tokyo, Japan
| | - T Sasaki
- Honeybee Science Research Center, Tamagawa University, Machida, Tokyo, Japan
| | - S Yajima
- NODAI Genome Research Center, Tokyo University of Agriculture, Setagaya-ku, Tokyo, Japan
- Department of Bioscience, Tokyo University of Agriculture, Setagaya-ku, Tokyo, Japan
| | - M Ono
- Laboratory of Applied Entomology and Zoology, Graduate School of Agriculture, Tamagawa University, Machida, Tokyo, Japan
- Honeybee Science Research Center, Tamagawa University, Machida, Tokyo, Japan
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Brutscher LM, Flenniken ML. RNAi and Antiviral Defense in the Honey Bee. J Immunol Res 2015; 2015:941897. [PMID: 26798663 PMCID: PMC4698999 DOI: 10.1155/2015/941897] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 11/25/2015] [Accepted: 11/29/2015] [Indexed: 01/08/2023] Open
Abstract
Honey bees play an important agricultural and ecological role as pollinators of numerous agricultural crops and other plant species. Therefore, investigating the factors associated with high annual losses of honey bee colonies in the US is an important and active area of research. Pathogen incidence and abundance correlate with Colony Collapse Disorder- (CCD-) affected colonies in the US and colony losses in the US and in some European countries. Honey bees are readily infected by single-stranded positive sense RNA viruses. Largely dependent on the host immune response, virus infections can either remain asymptomatic or result in deformities, paralysis, or death of adults or larvae. RNA interference (RNAi) is an important antiviral defense mechanism in insects, including honey bees. Herein, we review the role of RNAi in honey bee antiviral defense and highlight some parallels between insect and mammalian immune systems. A more thorough understanding of the role of pathogens on honey bee health and the immune mechanisms bees utilize to combat infectious agents may lead to the development of strategies that enhance honey bee health and result in the discovery of additional mechanisms of immunity in metazoans.
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Affiliation(s)
- Laura M. Brutscher
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717-3150, USA
- Institute on Ecosystems, Montana State University, Bozeman, MT 59717-3490, USA
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT 59717-3460, USA
| | - Michelle L. Flenniken
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717-3150, USA
- Institute on Ecosystems, Montana State University, Bozeman, MT 59717-3490, USA
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7
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Palmer MJ, Harvey J. Honeybee Kenyon cells are regulated by a tonic GABA receptor conductance. J Neurophysiol 2014; 112:2026-35. [PMID: 25031259 DOI: 10.1152/jn.00180.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The higher cognitive functions of insects are dependent on their mushroom bodies (MBs), which are particularly large in social insects such as honeybees. MB Kenyon cells (KCs) receive multisensory input and are involved in associative learning and memory. In addition to receiving sensory input via excitatory nicotinic synapses, KCs receive inhibitory GABAergic input from MB feedback neurons. Cultured honeybee KCs exhibit ionotropic GABA receptor currents, but the properties of GABA-mediated inhibition in intact MBs are currently unknown. Here, using whole cell recordings from KCs in acutely isolated honeybee brain, we show that KCs exhibit a tonic current that is inhibited by picrotoxin but not by bicuculline. Bath application of GABA (5 μM) and taurine (1 mM) activate a tonic current in KCs, but l-glutamate (0.1-0.5 mM) has no effect. The tonic current is strongly potentiated by the allosteric GABAA receptor modulator pentobarbital and is reduced by inhibition of Ca(2+) channels with Cd(2+) or nifedipine. Noise analysis of the GABA-evoked current gives a single-channel conductance value for the underlying receptors of 27 ± 3 pS, similar to that of resistant to dieldrin (RDL) receptors. The amount of injected current required to evoke action potential firing in KCs is significantly lower in the presence of picrotoxin. KCs recorded in an intact honeybee head preparation similarly exhibit a tonic GABA receptor conductance that reduces neuronal excitability, a property that is likely to contribute to the sparse coding of sensory information in insect MBs.
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Affiliation(s)
- Mary J Palmer
- Division of Neuroscience, Medical Research Institute, University of Dundee, Dundee, United Kingdom
| | - Jenni Harvey
- Division of Neuroscience, Medical Research Institute, University of Dundee, Dundee, United Kingdom
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8
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Effect of GABAergic inhibition on odorant concentration coding in mushroom body intrinsic neurons of the honeybee. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2013; 200:183-95. [DOI: 10.1007/s00359-013-0877-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 12/06/2013] [Accepted: 12/10/2013] [Indexed: 12/29/2022]
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Ugajin A, Kunieda T, Kubo T. Identification and characterization of an Egr ortholog as a neural immediate early gene in the European honeybee (Apis mellifera L.). FEBS Lett 2013; 587:3224-30. [PMID: 23994532 DOI: 10.1016/j.febslet.2013.08.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 08/19/2013] [Accepted: 08/19/2013] [Indexed: 10/26/2022]
Abstract
To date, there are only few reports of immediate early genes (IEGs) available in insects. Aiming at identifying a conserved IEG in insects, we characterized an Egr homolog of the honeybee (AmEgr: Apis mellifera Egr). AmEgr was transiently induced in whole worker brains after seizure induction. In situ hybridization for AmEgr indicated that neural activity of a certain mushroom body (a higher brain center) neuron subtype, which is the same as that we previously identified using another non-coding IEG, termed kakusei, is more enhanced in forager brains. These findings suggest that Egr can be utilized as an IEG in insects.
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Affiliation(s)
- Atsushi Ugajin
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Boumghar K, Couret-Fauvel T, Garcia M, Armengaud C. Evidence for a role of GABA- and glutamate-gated chloride channels in olfactory memory. Pharmacol Biochem Behav 2012; 103:69-75. [DOI: 10.1016/j.pbb.2012.08.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 07/26/2012] [Accepted: 08/04/2012] [Indexed: 01/11/2023]
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Torkkeli PH, Meisner S, Pfeiffer K, French AS. GABA and glutamate receptors have different effects on excitability and are differentially regulated by calcium in spider mechanosensory neurons. Eur J Neurosci 2012; 36:3602-14. [PMID: 22928994 DOI: 10.1111/j.1460-9568.2012.08275.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
GABA and glutamate receptors belonging to the ligand-gated chloride-channel family are primary targets of insecticides and antiparasitics, so their molecular structure, pharmacology and biophysical properties have attracted significant attention. However, little is known about the physiological roles of these channels or how they regulate neuronal excitability and animal behavior. Mechanosensory neurons of VS-3 slit sensilla in the patella of the tropical wandering spider, Cupiennius salei, react to the GABA(A)-receptor agonists, GABA and muscimol, with depolarization and an increase in intracellular [Ca(2+)] and, during random noise stimulation, with a mixed inhibitory-excitatory response. We established that the GABA(A)-receptors in all VS-3 neurons are identical, but there are at least two types of glutamate receptors and some neurons do not respond to glutamate at all. Immunohistochemistry with antibodies against Drosophila inhibitory glutamate receptor (GluCls) α-subunit suggests that in addition to VS-3 neurons, these receptors may also be present in the efferent neurons surrounding the sensory neurons. Most VS-3 neurons were inhibited but not depolarized by glutamate during random stimulation, but some depolarized and had a similar excitatory-inhibitory response to glutamate as to muscimol. The membrane-permeable Ca(2+)-chelator BAPTA-AM abolished muscimol effects but potentiated glutamate effects, indicating that GABA and glutamate receptors are differentially modulated by Ca(2+), leading to diverse regulation of neuronal excitability. We hypothesize that this could be achieved by different Ca(2+)-triggered phosphorylation processes at each receptor type. These findings are important for understanding the significance of Ca(2+)-mediated regulation of transmitter receptor molecules and its role in controlling excitability.
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Affiliation(s)
- Päivi H Torkkeli
- Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, NS, B3H 4R2, Canada.
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12
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Poppinga L, Janesch B, Fünfhaus A, Sekot G, Garcia-Gonzalez E, Hertlein G, Hedtke K, Schäffer C, Genersch E. Identification and functional analysis of the S-layer protein SplA of Paenibacillus larvae, the causative agent of American Foulbrood of honey bees. PLoS Pathog 2012; 8:e1002716. [PMID: 22615573 PMCID: PMC3355101 DOI: 10.1371/journal.ppat.1002716] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 04/07/2012] [Indexed: 11/23/2022] Open
Abstract
The Gram-positive, spore-forming bacterium Paenibacillus larvae is the etiological agent of American Foulbrood (AFB), a globally occurring, deathly epizootic of honey bee brood. AFB outbreaks are predominantly caused by two genotypes of P. larvae, ERIC I and ERIC II, with P. larvae ERIC II being the more virulent genotype on larval level. Recently, comparative proteome analyses have revealed that P. larvae ERIC II but not ERIC I might harbour a functional S-layer protein, named SplA. We here determine the genomic sequence of splA in both genotypes and demonstrate by in vitro self-assembly studies of recombinant and purified SplA protein in combination with electron-microscopy that SplA is a true S-layer protein self-assembling into a square 2D lattice. The existence of a functional S-layer protein is novel for this bacterial species. For elucidating the biological function of P. larvae SplA, a genetic system for disruption of gene expression in this important honey bee pathogen was developed. Subsequent analyses of in vivo biological functions of SplA were based on comparing a wild-type strain of P. larvae ERIC II with the newly constructed splA-knockout mutant of this strain. Differences in cell and colony morphology suggest that SplA is a shape-determining factor. Marked differences between P. larvae ERIC II wild-type and mutant cells with regard to (i) adhesion to primary pupal midgut cells and (ii) larval mortality as measured in exposure bioassays corroborate the assumption that the S-layer of P. larvae ERIC II is an important virulence factor. Since SplA is the first functionally proven virulence factor for this species, our data extend the knowledge of the molecular differences between these two genotypes of P. larvae and contribute to explaining the observed differences in virulence. These results present an immense advancement in our understanding of P. larvae pathogenesis. Paenibacillus larvae is the most devastating bacterial pathogen of honey bees. However, the molecular interactions between infected larvae and P. larvae are poorly understood and little more than speculation exist concerning virulence factors. Recently, a putative S-layer protein has been identified in P. larvae. We here demonstrate that only representatives of P. larvae genotype ERIC II harbor a functional splA-gene and that SplA is a true S-layer protein with self-assembly capability. The presence of a functional S-layer protein is novel for P. larvae. When elucidating the biological function of SplA we broke new ground by establishing primary cell culture for pupal gut cells and by developing a genetic system for disruption of gene expression in this important honey bee pathogen. By using these novel methods we were able to prove that SplA serves as a shape-determining factor, mediates adhesion to host cells, and is a key virulence factor of P. larvae ERIC II. These results present an immense advancement in our understanding of P. larvae pathogenesis. Furthermore, we propose P. larvae as a model system for the analysis of the in vivo functions of S-layer proteins because P. larvae SlpA knockout-mutants retain viability and are thus suitable for functional studies.
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Affiliation(s)
- Lena Poppinga
- Institute for Bee Research, Department of Molecular Bee Pathology, Hohen Neuendorf, Germany
| | - Bettina Janesch
- Department für NanoBiotechnologie, NanoGlycobiology, Universität für Bodenkultur Wien, Wien, Austria
| | - Anne Fünfhaus
- Institute for Bee Research, Department of Molecular Bee Pathology, Hohen Neuendorf, Germany
| | - Gerhard Sekot
- Department für NanoBiotechnologie, NanoGlycobiology, Universität für Bodenkultur Wien, Wien, Austria
| | - Eva Garcia-Gonzalez
- Institute for Bee Research, Department of Molecular Bee Pathology, Hohen Neuendorf, Germany
| | - Gillian Hertlein
- Institute for Bee Research, Department of Molecular Bee Pathology, Hohen Neuendorf, Germany
| | - Kati Hedtke
- Institute for Bee Research, Department of Molecular Bee Pathology, Hohen Neuendorf, Germany
| | - Christina Schäffer
- Department für NanoBiotechnologie, NanoGlycobiology, Universität für Bodenkultur Wien, Wien, Austria
| | - Elke Genersch
- Institute for Bee Research, Department of Molecular Bee Pathology, Hohen Neuendorf, Germany
- * E-mail:
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Inhibition of protein kinase C decreases sensitivity of GABA receptor subtype to fipronil insecticide in insect neurosecretory cells. Neurotoxicology 2011; 32:828-35. [DOI: 10.1016/j.neuro.2011.05.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 05/31/2011] [Accepted: 05/31/2011] [Indexed: 01/03/2023]
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14
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Dupuis JP, Bazelot M, Barbara GS, Paute S, Gauthier M, Raymond-Delpech V. Homomeric RDL and heteromeric RDL/LCCH3 GABA receptors in the honeybee antennal lobes: two candidates for inhibitory transmission in olfactory processing. J Neurophysiol 2009; 103:458-68. [PMID: 19906878 DOI: 10.1152/jn.00798.2009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
gamma-Aminobutyric acid (GABA)-gated chloride channel receptors are abundant in the CNS, where their physiological role is to mediate fast inhibitory neurotransmission. In insects, this inhibitory transmission plays a crucial role in olfactory information processing. In an effort to understand the nature and properties of the ionotropic receptors involved in these processes in the honeybee Apis mellifera, we performed a pharmacological and molecular characterization of GABA-gated channels in the primary olfactory neuropile of the honeybee brain-the antennal lobe (AL)-using whole cell patch-clamp recordings coupled with single-cell RT-PCR. Application of GABA onto AL cells at -110 mV elicited fast inward currents, demonstrating the existence of ionotropic GABA-gated chloride channels. Molecular analysis of the GABA-responding cells revealed that both subunits RDL and LCCH3 were expressed out of the three orthologs of Drosophila melanogaster GABA-receptor subunits encoded within the honeybee genome (RDL, resistant to dieldrin; GRD, GABA/glycine-like receptor of Drosophila; LCCH3, ligand-gated chloride channel homologue 3), opening the door to possible homo- and/or heteromeric associations. The resulting receptors were activated by insect GABA-receptor agonists muscimol and CACA and blocked by antagonists fipronil, dieldrin, and picrotoxin, but not bicuculline, displaying a typical RDL-like pharmacology. Interestingly, increasing the intracellular calcium concentration potentiated GABA-elicited currents, suggesting a modulating effect of calcium on GABA receptors possibly through phosphorylation processes that remain to be determined. These results indicate that adult honeybee AL cells express typical RDL-like GABA receptors whose properties support a major role in synaptic inhibitory transmission during olfactory information processing.
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Affiliation(s)
- Julien Pierre Dupuis
- Centre de Recherches sur la Cognition Animale, Université Paul Sabatier (Toulouse III), CNRS UMR 5169, 118 route de Narbonne, Toulouse Cedex 9, France
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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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In vivo labeling and in vitro characterisation of central complex neurons involved in the control of sound production. J Neurosci Methods 2009; 183:202-12. [PMID: 19583981 DOI: 10.1016/j.jneumeth.2009.06.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 06/23/2009] [Accepted: 06/27/2009] [Indexed: 11/22/2022]
Abstract
Injection of muscarine into the central complex of the grasshopper brain can stimulate species-specific sound production through activation of the phospholipase C-initiated transduction pathway. We introduce a strategy, to label central complex interneurons that are directly stimulated by the injected muscarine and to study their physiology in dissociated primary cell culture. Fluorescent dextranes, co-injected to brain sites where muscarine stimulates sound production, are incorporated from the extracellular space by 3-14 central complex neurons. Most labeled neurons are columnar neurons that express muscarinic acetylcholine receptors. An average of 3-4 dextrane-labeled central complex neurons per brain can be recognised by their fluorescence in dissociated cell cultures. Their function as potential direct targets of previous in vivo pharmacological stimulation of the intact brain was supported by expression of muscarinic receptors in cytomembranes of isolated neuronal cell bodies and muscarine-stimulated calcium responses in vitro. Pharmacological inhibition of phospholipase C function and removal of extracellular calcium indicated that release from inositolphosphate-regulated internal stores mediates the increase of cytosolic calcium concentrations. The experimental procedures described in this study can be applied to any preparation in which focal drug application elicits, terminates or modulates behavior in order to label and physiologically analyse those interneurons within the circuit that serve as direct targets of the injected drug.
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Mustard JA, Edgar EA, Mazade RE, Wu C, Lillvis JL, Wright GA. Acute ethanol ingestion impairs appetitive olfactory learning and odor discrimination in the honey bee. Neurobiol Learn Mem 2008; 90:633-43. [PMID: 18723103 DOI: 10.1016/j.nlm.2008.07.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Revised: 07/29/2008] [Accepted: 07/29/2008] [Indexed: 11/30/2022]
Abstract
Invertebrates are valuable models for increasing our understanding of the effects of ethanol on the nervous system, but most studies on invertebrates and ethanol have focused on the effects of ethanol on locomotor behavior. In this work we investigate the influence of an acute dose of ethanol on appetitive olfactory learning in the honey bee (Apis mellifera), a model system for learning and memory. Adult worker honey bees were fed a range of doses (2.5%, 5%, 10%, or 25%) of ethanol and then conditioned to associate an odor with a sucrose reward using either a simple or differential conditioning paradigm. Consumption of ethanol before conditioning significantly reduced both the rate of acquisition and the asymptotic strength of the association. Honey bees also exhibited a dose dependent reduction in arousal/attention during conditioning. Consumption of ethanol after conditioning did not affect recall 24h later. The observed deficits in acquisition were not due to the affect of ethanol on gustatory sensitivity or motor function. However, honey bees given higher doses of ethanol had difficulty discriminating amongst different odors suggesting that ethanol consumption influences olfactory processing. Taken together, these results demonstrate that an acute dose of ethanol affects appetitive learning and olfactory perception in the honey bee.
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Affiliation(s)
- Julie A Mustard
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ 85287, USA.
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