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Sourisse JM, Schunter C. Neuromolecular mechanisms related to reflex behaviour in Aplysia are affected by ocean acidification. ROYAL SOCIETY OPEN SCIENCE 2024; 11:240329. [PMID: 39100147 PMCID: PMC11296145 DOI: 10.1098/rsos.240329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 04/16/2024] [Accepted: 05/13/2024] [Indexed: 08/06/2024]
Abstract
While ocean acidification (OA) impacts the behaviour of marine organisms, the complexity of neurosystems makes linking behavioural impairments to environmental change difficult. Using a simple model, we exposed Aplysia to ambient or elevated CO2 conditions (approx. 1500 µatm) and tested how OA affected the neuromolecular response of the pleural-pedal ganglia and caused tail withdrawal reflex (TWR) impairment. Under OA, Aplysia relax their tails faster with increased sensorin-A expression, an inhibitor of mechanosensory neurons. We further investigate how OA affects habituation training output, which produced a 'sensitization-like' behaviour and affected vesicle transport and stress response gene expression, revealing an influence of OA on learning. Finally, gabazine did not restore normal behaviour and elicited little molecular response with OA, instead, vesicular transport and cellular signalling link other neurotransmitter processes with TWR impairment. Our study shows the effects of OA on neurological tissue parts that control for behaviour.
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Affiliation(s)
- Jade M. Sourisse
- The Swire Institute of Marine Science, School of Biological Sciences, The University of Hong Kong, Pokfulam Road, , Hong Kong
| | - Celia Schunter
- The Swire Institute of Marine Science, School of Biological Sciences, The University of Hong Kong, Pokfulam Road, , Hong Kong
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Dunn TW, Fan X, Lee J, Smith P, Gandhi R, Sossin WS. The role of specific isoforms of Ca V2 and the common C-terminal of Ca V2 in calcium channel function in sensory neurons of Aplysia. Sci Rep 2023; 13:20216. [PMID: 37980443 PMCID: PMC10657410 DOI: 10.1038/s41598-023-47573-z] [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: 06/19/2023] [Accepted: 11/15/2023] [Indexed: 11/20/2023] Open
Abstract
The presynaptic release apparatus can be specialized to enable specific synaptic functions. Habituation is the diminishing of a physiological response to a frequently repeated stimulus and in Aplysia, habituation to touch is mediated by a decrease in transmitter release from the sensory neurons that respond to touch even after modest rates of action potential firing. This synaptic depression is not common among Aplysia synaptic connections suggesting the presence of a release apparatus specialized for this depression. We found that specific splice forms of ApCaV2, the calcium channel required for transmitter release, are preferentially used in sensory neurons, consistent with a specialized release apparatus. However, we were not able to find a specific ApCaV2 splice uniquely required for synaptic depression. The C-terminus of ApCaV2 alpha1 subunit retains conserved binding to Aplysia rab-3 interacting molecule (ApRIM) and ApRIM-binding protein (ApRBP) and the C-terminus is required for full synaptic expression of ApCaV2. We also identified a splice form of ApRIM that did not interact with the ApCav2 alpha 1 subunit, but it was not preferentially used in sensory neurons.
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Affiliation(s)
- Tyler W Dunn
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - Xiaotang Fan
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - Jiwon Lee
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - Petranea Smith
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - Rushali Gandhi
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - Wayne S Sossin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada.
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Enhanced single-cell metabolomics by capillary electrophoresis electrospray ionization-mass spectrometry with field amplified sample injection. Anal Chim Acta 2020; 1118:36-43. [PMID: 32418602 DOI: 10.1016/j.aca.2020.04.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/08/2020] [Accepted: 04/10/2020] [Indexed: 12/26/2022]
Abstract
Single-cell metabolomics provides information on the biochemical state of an individual cell and its relationship with the surrounding environment. Characterization of metabolic cellular heterogeneity is challenging, in part due to the small amounts of analytes and their wide dynamic concentration ranges within individual cells. CE-ESI-MS is well suited to single-cell assays because of its low sample-volume requirements and low detection limits. While the volume of a cell is in the picoliter range, after isolation, the typical volume of the lysed cell sample is on the order of a microliter; however, only nanoliters are injected into the CE system, with the volume mismatch limiting analytical performance. Here we developed an approach for the detection of intracellular metabolites from a single neuron using field amplified sample injection (FASI) CE-ESI-MS. Through the application of FASI, we achieved 100- to 300-fold detection limit enhancement compared to hydrodynamic injections. We further enhanced the analyte identification and quantification accuracy via introduction of two internal standards. As a result, the relative standard deviations of migration times were reduced to <5%, aiding identification. Finally, we successfully applied FASI CE-ESI-MS to the untargeted profiling of metabolites of Aplysia californica pleural sensory neurons with <50 μm diameter cell somata. As a result, twenty one neurotransmitters and metabolites have been quantified in these neurons.
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Farah CA, Dunn TW, Hastings MH, Ferguson L, Gao C, Gong K, Sossin WS. A role for Numb in Protein kinase M (PKM)-mediated increase in surface AMPA receptors during facilitation in Aplysia. J Neurochem 2019; 150:366-384. [PMID: 31254393 DOI: 10.1111/jnc.14807] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 06/25/2019] [Accepted: 06/26/2019] [Indexed: 12/15/2022]
Abstract
There is considerable evidence from both vertebrates and invertebrates that persistently active protein kinases maintain changes in synaptic strength that underlie memory. In the hermaphrodite marine mollusk, Aplysia californica, truncated forms of protein kinase C (PKC) termed protein kinase Ms have been implicated in both intermediate- and long-term facilitation, an increase in synaptic strength between sensory neurons and motor neurons thought to underlie behavioural sensitization in the animal. However, few substrates have been identified as candidates that could mediate this increase in synaptic strength. PKMs have been proposed to maintain synaptic strength through preventing endocytosis of AMPA receptors. Numb is a conserved regulator of endocytosis that is modulated by phosphorylation. We have identified and cloned Aplysia Numb (ApNumb). ApNumb contains three conserved PKC phosphorylation sites and PKMs generated from classical and atypical Aplysia PKCs can phosphorylate ApNumb in vitro and in cells. Over-expression of ApNumb that lacks the conserved PKC phosphorylation sites blocks increases in surface levels of a pHluorin-tagged Aplysia glutamate receptor measured using live imaging after intermediate- or long-term facilitation. Over-expression of this form of ApNumb did not block increases in synaptic strength seen during intermediate-term facilitation, but did block increases in synaptic strength seen during long-term facilitation. There was no effect of over-expression of this form of ApNumb on other putative Numb targets as measured using increases in calcium downstream of neurotrophins or agonists of metabotropic glutamate receptors. These results suggest that in Aplysia neurons, Numb specifically regulates AMPA receptor trafficking and is an attractive candidate for a target of PKMs in long-term maintenance of synaptic strength. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Open Science: This manuscript was awarded with the Open Materials Badge For more information see: https://cos.io/our-services/open-science-badges/.
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Affiliation(s)
- Carole A Farah
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Tyler W Dunn
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Margaret H Hastings
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Larissa Ferguson
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Cherry Gao
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Katrina Gong
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Wayne S Sossin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
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Dunn TW, Fan X, Ase AR, Séguéla P, Sossin WS. The Ca V2α1 EF-hand F helix tyrosine, a highly conserved locus for GPCR inhibition of Ca V2 channels. Sci Rep 2018; 8:3263. [PMID: 29459734 PMCID: PMC5818475 DOI: 10.1038/s41598-018-21586-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 02/07/2018] [Indexed: 12/16/2022] Open
Abstract
The sensory neuron of Aplysia californica participates in several forms of presynaptic plasticity including homosynaptic depression, heterosynaptic depression, facilitation and the reversal of depression. The calcium channel triggering neurotransmitter release at most synapses is CaV2, consisting of the pore forming α1 subunit (CaV2α1), and auxiliary CaVβ, and CaVα2δ subunits. To determine the role of the CaV2 channel in presynaptic plasticity in Aplysia, we cloned Aplysia CaV2α1, CaVβ, and CaVα2δ and over-expressed the proteins in Aplysia sensory neurons (SN). We show expression of exogenous CaV2α1 in the neurites of cultured Aplysia SN. One proposed mechanism for heterosynaptic depression in Aplysia is through inhibition of CaV2. Here, we demonstrate that heterosynaptic depression of the CaV2 calcium current is inhibited when a channel with a Y-F mutation at the conserved Src phosphorylation site is expressed, showing the strong conservation of this mechanism over evolution. We also show that the Y-F mutation reduces heterosynaptic inhibition of neurotransmitter release, highlighting the physiological importance of this mechanism for the regulation of synaptic efficacy. These results also demonstrate our ability to replace endogenous CaV2 channels with recombinant channels allowing future examination of the structure function relationship of CaV2 in the regulation of transmitter release in this system.
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Affiliation(s)
- Tyler W Dunn
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Xiaotang Fan
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Ariel R Ase
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Philippe Séguéla
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Wayne S Sossin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, H3A 2B4, Canada.
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Dunn TW, Sossin WS. Decline in the Recovery from Synaptic Depression in Heavier Aplysia Results from Decreased Serotonin-Induced Novel PKC Activation. PLoS One 2015; 10:e0136907. [PMID: 26317974 PMCID: PMC4552628 DOI: 10.1371/journal.pone.0136907] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 08/09/2015] [Indexed: 11/21/2022] Open
Abstract
The defensive withdrawal reflexes of Aplysia are important behaviors for protecting the animal from predation. Habituation and dishabituation allow for experience-dependent tuning of these reflexes and the mechanisms underlying these forms of behavioral plasticity involve changes in transmitter release from the sensory to motor neuron synapses through homosynaptic depression and the serotonin-mediated recovery from depression, respectively. Interestingly, dishabituation is reduced in older animals with no corresponding change in habituation. Here we show that the cultured sensory neurons of heavier animals (greater than 120g) that form synaptic connections with motor neurons have both reduced recovery from depression and reduced novel PKC Apl II activation with 5HT. The decrease in the recovery from depression correlated better with the size of the animal than the age of the animal. Much of this change in PKC activation and synaptic facilitation following depression can be rescued by direct activation of PKC Apl II with phorbol dibutyrate, suggesting a change in the signal transduction pathway upstream of PKC Apl II activation in the sensory neurons of larger animals.
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Affiliation(s)
- Tyler William Dunn
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Wayne S. Sossin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
- * E-mail:
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Farah CA, Naqib F, Weatherill DB, Pack CC, Sossin WS. Synapse formation changes the rules for desensitization of PKC translocation in Aplysia. Eur J Neurosci 2014; 41:328-40. [PMID: 25401305 DOI: 10.1111/ejn.12794] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 10/15/2014] [Accepted: 10/23/2014] [Indexed: 11/29/2022]
Abstract
Protein kinase Cs (PKCs) are activated by translocating from the cytoplasm to the membrane. We have previously shown that serotonin-mediated translocation of PKC to the plasma membrane in Aplysia sensory neurons was subject to desensitization, a decrease in the ability of serotonin to induce translocation after previous application of serotonin. In Aplysia, changes in the strength of the sensory-motor neuron synapse are important for behavioral sensitization and PKC regulates a number of important aspects of this form of synaptic plasticity. We have previously suggested that the desensitization of PKC translocation in Aplysia sensory neurons may partially explain the differences between spaced and massed training, as spaced applications of serotonin, a cellular analog of spaced training, cause greater desensitization of PKC translocation than one massed application of serotonin, a cellular analog of massed training. Our previous studies were performed in isolated sensory neurons. In the present study, we monitored translocation of fluorescently-tagged PKC to the plasma membrane in living sensory neurons that were co-cultured with motor neurons to allow for synapse formation. We show that desensitization now becomes similar during spaced and massed applications of serotonin. We had previously modeled the signaling pathways that govern desensitization in isolated sensory neurons. We now modify this mathematical model to account for the changes observed in desensitization dynamics following synapse formation. Our study shows that synapse formation leads to significant changes in the molecular signaling networks that underlie desensitization of PKC translocation.
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Affiliation(s)
- Carole A Farah
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Quebec, H3A 2B4, Canada
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Dunn TW, Sossin WS. Inhibition of the Aplysia sensory neuron calcium current with dopamine and serotonin. J Neurophysiol 2013; 110:2071-81. [DOI: 10.1152/jn.00217.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The inhibition of Aplysia pleural mechanosensory neuron synapses by dopamine and serotonin through activation of endogenous dopaminergic and expressed 5-HT1Apl(a)/b receptors, respectively, involves a reduction in action potential-associated calcium influx. We show that the inhibition of synaptic efficacy is downstream of the readily releasable pool, suggesting that inhibition is at the level of calcium secretion coupling, likely a result of the changes in the calcium current. Indeed, the inhibitory responses directly reduce a CaV2-like calcium current in isolated sensory neurons. The inhibition of the calcium current is voltage independent as it is not affected by a strong depolarizing prepulse, consistent with other invertebrate CaV2 calcium currents. Similar to voltage-independent inhibition of vertebrate nociceptors, inhibition was blocked with Src tyrosine kinase inhibitors. The data suggest a conserved mechanism by which G protein-coupled receptor activation can inhibit the CaV2 calcium current in nociceptive neurons.
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Affiliation(s)
- Tyler W. Dunn
- Department Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Wayne S. Sossin
- Department Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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Titlow JS, Rufer JM, King KE, Cooper RL. Pharmacological analysis of dopamine modulation in the Drosophila melanogaster larval heart. Physiol Rep 2013; 1:e00020. [PMID: 24303109 PMCID: PMC3831916 DOI: 10.1002/phy2.20] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 05/23/2013] [Accepted: 06/04/2013] [Indexed: 02/06/2023] Open
Abstract
Dopamine (DA) and other neurotransmitters affect nonneuronal tissues in insects by circulating in the hemolymph. In several organisms, DA has been shown to modulate distinct aspects of cardiac function but the signal transduction pathways that mediate dopaminergic effects on the heart are not well characterized. Here, we used a semiintact Drosophila melanogaster larva preparation and drugs targeting DA receptors and canonical second messenger pathways to identify signaling cascades that mediate the effect of DA on a myogenic heart. DA has a positive chronotropic effect that is mimicked by SKF38393 (type-1 DA receptor agonist) and quinpirole (type-2 DA receptor agonist). SCH23390 and spiperone (type-1 and type-2 DA receptor antagonists) are moderately effective at inhibiting DA's effect. An adenylate cyclase inhibitor (SQ,22536) is also effective at blocking the stimulatory effect of DA but the drug has its own dose-dependent effect. Activation of protein kinase C with a diacylglycerol analog has a stimulatory effect on heart rate (HR). These results suggest that (1) both DA receptor subtypes are expressed in third instar larva cardiac myocytes to increase HR in response to rising levels of DA in the hemolymph, and (2) canonical second messenger pathways modulate HR in D. melanogaster larvae. Having these disparate signaling cascades converge toward a common modulatory function appears redundant, but in the context of multiple cardioactive chemicals this redundancy is likely to increase the fidelity of signal transduction.
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Affiliation(s)
- Josh S Titlow
- Department of Biology and Center for Muscle Biology, University of Kentucky Lexington, KY, 40506-0225
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Roles of Protein Kinase C and Protein Kinase M in Aplysia Learning. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/b978-0-12-415823-8.00018-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Farah CA, Lindeman AA, Siu V, Gupta MD, Sossin WS. Autophosphorylation of the C2 domain inhibits translocation of the novel protein kinase C (nPKC) Apl II. J Neurochem 2012; 123:360-72. [PMID: 22913526 DOI: 10.1111/j.1471-4159.2012.07930.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 08/16/2012] [Accepted: 08/17/2012] [Indexed: 11/29/2022]
Abstract
Protein kinase Cs (PKCs) are critical signaling molecules controlled by complex regulatory pathways. Herein, we describe an important regulatory role for C2 domain phosphorylation. Novel PKCs (nPKCs) contain an N-terminal C2 domain that cannot bind to calcium. Previously, we described an autophosphorylation site in the Aplysia novel PKC Apl II that increased the binding of the C2 domain to lipids. In this study, we show that the function of this phosphorylation is to inhibit PKC translocation. Indeed, a phosphomimetic serine-glutamic acid mutation reduced translocation of PKC Apl II while blocking phosphorylation with a serine-alanine mutation enhanced translocation and led to the persistence of the kinase at the membrane longer after the end of the stimulation. Consistent with a role for autophosphorylation in regulating kinase translocation, inhibiting PKC activity using bisindolymaleimide 1 increased physiological translocation of PKC Apl II, whereas inhibiting phosphatase activity using calyculin A inhibited physiological translocation of PKC Apl II in neurons. Our results suggest a major role for autophosphorylation-dependent regulation of translocation.
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Affiliation(s)
- Carole A Farah
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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