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Wasilewicz LJ, Gagnon ZE, Jung J, Mercier AJ. Investigating postsynaptic effects of a Drosophila neuropeptide on muscle contraction. J Neurophysiol 2024; 131:137-151. [PMID: 38150542 DOI: 10.1152/jn.00246.2023] [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: 06/20/2023] [Revised: 11/20/2023] [Accepted: 12/20/2023] [Indexed: 12/29/2023] Open
Abstract
The Drosophila neuropeptide, DPKQDFMRFamide, was previously shown to enhance excitatory junctional potentials (EJPs) and muscle contraction by both presynaptic and postsynaptic actions. Since the peptide acts on both sides of the synaptic cleft, it has been difficult to examine postsynaptic modulatory mechanisms, particularly when contractions are elicited by nerve stimulation. Here, postsynaptic actions are examined in 3rd instar larvae by applying peptide and the excitatory neurotransmitter, l-glutamate, in the bathing solution to elicit contractions after silencing motor output by removing the central nervous system (CNS). DPKQDFMRFamide enhanced glutamate-evoked contractions at low concentrations (EC50 1.3 nM), consistent with its role as a neurohormone, and the combined effect of both substances was supra-additive. Glutamate-evoked contractions were also enhanced when transmitter release was blocked in temperature-sensitive (Shibire) mutants, confirming the peptide's postsynaptic action. The peptide increased membrane depolarization in muscle when co-applied with glutamate, and its effects were blocked by nifedipine, an L-type channel blocker, indicating effects at the plasma membrane involving calcium influx. DPKQDFMRFamide also enhanced contractions induced by caffeine in the absence of extracellular calcium, suggesting increased calcium release from the sarcoplasmic reticulum (SR) or effects downstream of calcium release from the SR. The peptide's effects do not appear to involve calcium/calmodulin-dependent protein kinase II (CaMKII), previously shown to mediate presynaptic effects. The approach used here might be useful for examining postsynaptic effects of neurohormones and cotransmitters in other systems.NEW & NOTEWORTHY Distinguishing presynaptic and postsynaptic effects of neurohormones is a long-standing challenge in many model organisms. Here, postsynaptic actions of DPKQDFMRFamide are demonstrated by assessing its ability to potentiate contractions elicited by direct application of the neurotransmitter, glutamate, when axons are silent and when transmitter release is blocked. The peptide acts at multiple sites to increase contraction, increasing glutamate-induced depolarization at the cell membrane, acting on L-type channels, and acting downstream of calcium release from the sarcoplasmic reticulum.
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Affiliation(s)
- Lucas J Wasilewicz
- Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada
| | - Zoe E Gagnon
- Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada
| | - JaeHwan Jung
- Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada
| | - A Joffre Mercier
- Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada
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Guo L, Sun Y, Liu S. Adaptive behaviors of Drosophila larvae on slippery surfaces. J Biol Phys 2023; 49:121-132. [PMID: 36790728 PMCID: PMC9958210 DOI: 10.1007/s10867-023-09626-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 01/13/2023] [Indexed: 02/16/2023] Open
Abstract
Friction is ubiquitous but an essential force for insects during locomotion. Insects use dedicated bio-mechanical systems such as adhesive pads to modulate the intensity of friction, providing a stable grip with touching substrates for locomotion. However, how to uncover behavioral adaptation and regulatory neural circuits of friction modification is still largely understood. In this study, we devised a novel behavior paradigm to investigate adaptive behavioral alternation of Drosophila larvae under low-friction surfaces. We found a tail looseness phenotype similar to slipping behavior in humans, as a primary indicator to assess the degree of slipping. We found a gradual reduction on slipping level in wild-type larvae after successive larval crawling, coupled with incremental tail contraction, displacement, and speed acceleration. Meanwhile, we also found a strong correlation between tail looseness index and length of contraction, suggesting that lengthening tail contraction may contribute to enlarging the contact area with the tube. Moreover, we found a delayed adaptation in rut mutant larvae, inferring that neural plasticity may participate in slipping adaptation. In conclusion, our paradigm can be easily and reliably replicated, providing a feasible pathway to uncover the behavioral principle and neural mechanism of acclimation of Drosophila larvae to low-friction conditions.
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Affiliation(s)
- Li Guo
- Zhejiang Lab, Nanhu Headquarters, Kechuang Avenue, Zhongtai Sub-District, Yuhang District, Hangzhou City, Zhejiang Province, 311121, People's Republic of China.
| | - Yixuan Sun
- Zhejiang Lab, Nanhu Headquarters, Kechuang Avenue, Zhongtai Sub-District, Yuhang District, Hangzhou City, Zhejiang Province, 311121, People's Republic of China
| | - Sijian Liu
- Zhejiang Lab, Nanhu Headquarters, Kechuang Avenue, Zhongtai Sub-District, Yuhang District, Hangzhou City, Zhejiang Province, 311121, People's Republic of China
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Activity-Dependent Global Downscaling of Evoked Neurotransmitter Release across Glutamatergic Inputs in Drosophila. J Neurosci 2020; 40:8025-8041. [PMID: 32928887 DOI: 10.1523/jneurosci.0349-20.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 09/01/2020] [Accepted: 09/04/2020] [Indexed: 12/11/2022] Open
Abstract
Within mammalian brain circuits, activity-dependent synaptic adaptations, such as synaptic scaling, stabilize neuronal activity in the face of perturbations. Stability afforded through synaptic scaling involves uniform scaling of quantal amplitudes across all synaptic inputs formed on neurons, as well as on the postsynaptic side. It remains unclear whether activity-dependent uniform scaling also operates within peripheral circuits. We tested for such scaling in a Drosophila larval neuromuscular circuit, where the muscle receives synaptic inputs from different motoneurons. We used motoneuron-specific genetic manipulations to increase the activity of only one motoneuron and recordings of postsynaptic currents from inputs formed by the different motoneurons. We discovered an adaptation which caused uniform downscaling of evoked neurotransmitter release across all inputs through decreases in release probabilities. This "presynaptic downscaling" maintained the relative differences in neurotransmitter release across all inputs around a homeostatic set point, caused a compensatory decrease in synaptic drive to the muscle affording robust and stable muscle activity, and was induced within hours. Presynaptic downscaling was associated with an activity-dependent increase in Drosophila vesicular glutamate transporter expression. Activity-dependent uniform scaling can therefore manifest also on the presynaptic side to produce robust and stable circuit outputs. Within brain circuits, uniform downscaling on the postsynaptic side is implicated in sleep- and memory-related processes. Our results suggest that evaluation of such processes might be broadened to include uniform downscaling on the presynaptic side.SIGNIFICANCE STATEMENT To date, compensatory adaptations which stabilise target cell activity through activity-dependent global scaling have been observed only within central circuits, and on the postsynaptic side. Considering that maintenance of stable activity is imperative for the robust function of the nervous system as a whole, we tested whether activity-dependent global scaling could also manifest within peripheral circuits. We uncovered a compensatory adaptation which causes global scaling within a peripheral circuit and on the presynaptic side through uniform downscaling of evoked neurotransmitter release. Unlike in central circuits, uniform scaling maintains functionality over a wide, rather than a narrow, operational range, affording robust and stable activity. Activity-dependent global scaling therefore operates on both the presynaptic and postsynaptic sides to maintain target cell activity.
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Neuronal Glutamatergic Synaptic Clefts Alkalinize Rather Than Acidify during Neurotransmission. J Neurosci 2020; 40:1611-1624. [PMID: 31964719 DOI: 10.1523/jneurosci.1774-19.2020] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 01/14/2020] [Accepted: 01/15/2020] [Indexed: 12/11/2022] Open
Abstract
The dogma that the synaptic cleft acidifies during neurotransmission is based on the corelease of neurotransmitters and protons from synaptic vesicles, and is supported by direct data from sensory ribbon-type synapses. However, it is unclear whether acidification occurs at non-ribbon-type synapses. Here we used genetically encoded fluorescent pH indicators to examine cleft pH at conventional neuronal synapses. At the neuromuscular junction of female Drosophila larvae, we observed alkaline spikes of over 1 log unit during fictive locomotion in vivo. Ex vivo, single action potentials evoked alkalinizing pH transients of only ∼0.01 log unit, but these transients summated rapidly during burst firing. A chemical pH indicator targeted to the cleft corroborated these findings. Cleft pH transients were dependent on Ca2+ movement across the postsynaptic membrane, rather than neurotransmitter release per se, a result consistent with cleft alkalinization being driven by the Ca2+/H+ antiporting activity of the plasma membrane Ca2+-ATPase at the postsynaptic membrane. Targeting the pH indicators to the microenvironment of the presynaptic voltage gated Ca2+ channels revealed that alkalinization also occurred within the cleft proper at the active zone and not just within extrasynaptic regions. Application of the pH indicators at the mouse calyx of Held, a mammalian central synapse, similarly revealed cleft alkalinization during burst firing in both males and females. These findings, made at two quite different non-ribbon type synapses, suggest that cleft alkalinization during neurotransmission, rather than acidification, is a generalizable phenomenon across conventional neuronal synapses.SIGNIFICANCE STATEMENT Neurotransmission is highly sensitive to the pH of the extracellular milieu. This is readily evident in the neurological symptoms that accompany systemic acid/base imbalances. Imaging data from sensory ribbon-type synapses show that neurotransmission itself can acidify the synaptic cleft, likely due to the corelease of protons and glutamate. It is not clear whether the same phenomenon occurs at conventional neuronal synapses due to the difficulties in collecting such data. If it does occur, it would provide for an additional layer of activity-dependent modulation of neurotransmission. Our findings of alkalinization, rather than acidification, within the cleft of two different neuronal synapses encourages a reassessment of the scope of activity-dependent pH influences on neurotransmission and short-term synaptic plasticity.
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Expression of Heat Shock Protein 70 Is Insufficient To Extend Drosophila melanogaster Longevity. G3-GENES GENOMES GENETICS 2019; 9:4197-4207. [PMID: 31624139 PMCID: PMC6893204 DOI: 10.1534/g3.119.400782] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It has been known for over 20 years that Drosophila melanogaster flies with twelve additional copies of the hsp70 gene encoding the 70 kD heat shock protein lives longer after a non-lethal heat treatment. Since the heat treatment also induces the expression of additional heat shock proteins, the biological effect can be due either to HSP70 acting alone or in combination. This study used the UAS/GAL4 system to determine whether hsp70 is sufficient to affect the longevity and the resistance to thermal, oxidative or desiccation stresses of the whole organism. We observed that HSP70 expression in the nervous system or muscles has no effect on longevity or stress resistance but ubiquitous expression reduces the life span of males. We also observed that the down-regulation of hsp70 using RNAi did not affect longevity.
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Ma CS, Wang L, Zhang W, Rudolf VHW. Resolving biological impacts of multiple heat waves: interaction of hot and recovery days. OIKOS 2018. [DOI: 10.1111/oik.04699] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Chun-Sen Ma
- Climate Change Biology Research Group, State Key Laboratory for Biology of Plant Diseases and Insect Pests, Inst. of Plant Protection, Chinese Academy of Agricultural Sciences; No 2 Yuanmingyuan West Road Haidian District CN-100193 Beijing PR China
| | - Lin Wang
- Climate Change Biology Research Group, State Key Laboratory for Biology of Plant Diseases and Insect Pests, Inst. of Plant Protection, Chinese Academy of Agricultural Sciences; No 2 Yuanmingyuan West Road Haidian District CN-100193 Beijing PR China
| | - Wei Zhang
- Climate Change Biology Research Group, State Key Laboratory for Biology of Plant Diseases and Insect Pests, Inst. of Plant Protection, Chinese Academy of Agricultural Sciences; No 2 Yuanmingyuan West Road Haidian District CN-100193 Beijing PR China
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Kalinnikova TB, Kolsanova RR, Belova EB, Shagidullin RR, Gainutdinov MK. Opposite effects of moderate heat stress and hyperthermia on cholinergic system of soil nematodes Caenorhabditis elegans and Caenorhabditis briggsae. J Therm Biol 2016; 62:37-49. [PMID: 27839548 DOI: 10.1016/j.jtherbio.2016.05.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 05/26/2016] [Accepted: 05/29/2016] [Indexed: 10/20/2022]
Abstract
Cholinergic system plays important role in all functions of organisms of free-living soil nematodes C. elegans and C. briggsae. Using pharmacological analysis we showed the existence of two opposite responses of nematodes cholinergic system to moderate and extreme heat stress. Short-term (15min) noxious heat (31-32°C) caused activation of cholinergic synaptic transmission in C. elegans and C. briggsae organisms by sensitization of nicotinic ACh receptors. In contrast, hyperthermia blocked cholinergic synaptic transmission by inhibition of ACh secretion by neurons. The resistance of behavior to extreme high temperature (36-37°C) was significantly higher in C. briggsae than in C. elegans, and thermostability of cholinergic transmission correlated with resistance of behavior to hyperthermia. Activation of cholinergic transmission by moderate heat stress can be the reason of movement speed increase in such adaptive behavior as noxious heat escape. Inhibition of ACh release is one of reasons for behavior failure caused by extreme high temperature since partial inhibition of ACh-esterase by aldicarb protected C. elegans and C. briggsae behavior against hyperthermia. Antagonist of mAChRs atropine almost completely prevented the rise in behavior thermotolerance caused by aldicarb. Pilocarpine, agonist of mAChRs, protected nematodes behavior against hyperthermia similarly with aldicarb. Therefore it is evident that it is the deficiency of mAChRs activity that is the reason for nematodes' behavior failure by hyperthermia.
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Affiliation(s)
- Tatiana B Kalinnikova
- Research Institute for Problems of Ecology and Mineral Wealth Use of Tatarstan Academy of Sciences, Daurskaya str., 28, 420087 Kazan, Russia.
| | - Rufina R Kolsanova
- Research Institute for Problems of Ecology and Mineral Wealth Use of Tatarstan Academy of Sciences, Daurskaya str., 28, 420087 Kazan, Russia
| | - Evgenia B Belova
- Research Institute for Problems of Ecology and Mineral Wealth Use of Tatarstan Academy of Sciences, Daurskaya str., 28, 420087 Kazan, Russia
| | - Rifgat R Shagidullin
- Research Institute for Problems of Ecology and Mineral Wealth Use of Tatarstan Academy of Sciences, Daurskaya str., 28, 420087 Kazan, Russia
| | - Marat Kh Gainutdinov
- Research Institute for Problems of Ecology and Mineral Wealth Use of Tatarstan Academy of Sciences, Daurskaya str., 28, 420087 Kazan, Russia
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Lu Z, Chouhan AK, Borycz JA, Lu Z, Rossano AJ, Brain KL, Zhou Y, Meinertzhagen IA, Macleod GT. High-Probability Neurotransmitter Release Sites Represent an Energy-Efficient Design. Curr Biol 2016; 26:2562-2571. [PMID: 27593375 DOI: 10.1016/j.cub.2016.07.032] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 06/06/2016] [Accepted: 07/12/2016] [Indexed: 01/22/2023]
Abstract
Nerve terminals contain multiple sites specialized for the release of neurotransmitters. Release usually occurs with low probability, a design thought to confer many advantages. High-probability release sites are not uncommon, but their advantages are not well understood. Here, we test the hypothesis that high-probability release sites represent an energy-efficient design. We examined release site probabilities and energy efficiency at the terminals of two glutamatergic motor neurons synapsing on the same muscle fiber in Drosophila larvae. Through electrophysiological and ultrastructural measurements, we calculated release site probabilities to differ considerably between terminals (0.33 versus 0.11). We estimated the energy required to release and recycle glutamate from the same measurements. The energy required to remove calcium and sodium ions subsequent to nerve excitation was estimated through microfluorimetric and morphological measurements. We calculated energy efficiency as the number of glutamate molecules released per ATP molecule hydrolyzed, and high-probability release site terminals were found to be more efficient (0.13 versus 0.06). Our analytical model indicates that energy efficiency is optimal (∼0.15) at high release site probabilities (∼0.76). As limitations in energy supply constrain neural function, high-probability release sites might ameliorate such constraints by demanding less energy. Energy efficiency can be viewed as one aspect of nerve terminal function, in balance with others, because high-efficiency terminals depress significantly during episodic bursts of activity.
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Affiliation(s)
- Zhongmin Lu
- Integrative Biology and Neuroscience Graduate Program, Department of Biological Sciences and Wilkes Honors College, Florida Atlantic University, Jupiter, FL 33458, USA
| | - Amit K Chouhan
- School of Psychology and Neuroscience, University of St Andrews, St Andrews KY16 9AJ, Scotland, UK
| | - Jolanta A Borycz
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Zhiyuan Lu
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Adam J Rossano
- Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | - Keith L Brain
- Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - You Zhou
- Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Ian A Meinertzhagen
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Gregory T Macleod
- Department of Biological Sciences and Wilkes Honors College, Florida Atlantic University, Jupiter, FL 33458, USA.
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Karunanithi S, Brown IR. Heat shock response and homeostatic plasticity. Front Cell Neurosci 2015; 9:68. [PMID: 25814928 PMCID: PMC4357293 DOI: 10.3389/fncel.2015.00068] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 02/17/2015] [Indexed: 11/13/2022] Open
Abstract
Heat shock response and homeostatic plasticity are mechanisms that afford functional stability to cells in the face of stress. Each mechanism has been investigated independently, but the link between the two has not been extensively explored. We explore this link. The heat shock response enables cells to adapt to stresses such as high temperature, metabolic stress and reduced oxygen levels. This mechanism results from the production of heat shock proteins (HSPs) which maintain normal cellular functions by counteracting the misfolding of cellular proteins. Homeostatic plasticity enables neurons and their target cells to maintain their activity levels around their respective set points in the face of stress or disturbances. This mechanism results from the recruitment of adaptations at synaptic inputs, or at voltage-gated ion channels. In this perspective, we argue that heat shock triggers homeostatic plasticity through the production of HSPs. We also suggest that homeostatic plasticity is a form of neuroprotection.
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Affiliation(s)
- Shanker Karunanithi
- School of Medical Science, Griffith University QLD, Australia ; Menzies Health Institute of Queensland, Griffith University QLD, Australia
| | - Ian R Brown
- Department of Biological Sciences, Centre for the Neurobiology of Stress, University of Toronto Scarborough Toronto, ON, Canada
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Rossano AJ, Chouhan AK, Macleod GT. Genetically encoded pH-indicators reveal activity-dependent cytosolic acidification of Drosophila motor nerve termini in vivo. J Physiol 2013; 591:1691-706. [PMID: 23401611 PMCID: PMC3624846 DOI: 10.1113/jphysiol.2012.248377] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 01/04/2013] [Indexed: 01/27/2023] Open
Abstract
All biochemical processes, including those underlying synaptic function and plasticity, are pH sensitive. Cytosolic pH (pH(cyto)) shifts are known to accompany nerve activity in situ, but technological limitations have prevented characterization of such shifts in vivo. Genetically encoded pH-indicators (GEpHIs) allow for tissue-specific in vivo measurement of pH. We expressed three different GEpHIs in the cytosol of Drosophila larval motor neurons and observed substantial presynaptic acidification in nerve termini during nerve stimulation in situ. SuperEcliptic pHluorin was the most useful GEpHI for studying pH(cyto) shifts in this model system. We determined the resting pH of the nerve terminal cytosol to be 7.30 ± 0.02, and observed a decrease of 0.16 ± 0.01 pH units when the axon was stimulated at 40 Hz for 4 s. Realkalinization occurred upon cessation of stimulation with a time course of 20.54 ± 1.05 s (τ). The chemical pH-indicator 2,7-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein corroborated these changes in pH(cyto). Bicarbonate-derived buffering did not contribute to buffering of acid loads from short (≤ 4 s) trains of action potentials but did buffer slow (~60 s) acid loads. The magnitude of cytosolic acid transients correlated with cytosolic Ca(2+) increase upon stimulation, and partial inhibition of the plasma membrane Ca(2+)-ATPase, a Ca(2+)/H(+) exchanger, attenuated pH(cyto) shifts. Repeated stimulus trains mimicking motor patterns generated greater cytosolic acidification (~0.30 pH units). Imaging through the cuticle of intact larvae revealed spontaneous pH(cyto) shifts in presynaptic termini in vivo, similar to those seen in situ during fictive locomotion, indicating that presynaptic pH(cyto) shifts cannot be dismissed as artifacts of ex vivo preparations.
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Affiliation(s)
- Adam J Rossano
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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Hoekstra LA, Montooth KL. Inducing extra copies of the Hsp70 gene in Drosophila melanogaster increases energetic demand. BMC Evol Biol 2013; 13:68. [PMID: 23510136 PMCID: PMC3641968 DOI: 10.1186/1471-2148-13-68] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 02/26/2013] [Indexed: 12/17/2022] Open
Abstract
Background Mutations that increase gene expression are predicted to increase energy allocation to transcription, translation and protein function. Despite an appreciation that energetic tradeoffs may constrain adaptation, the energetic costs of increased gene expression are challenging to quantify and thus easily ignored when modeling the evolution of gene expression, particularly for multicellular organisms. Here we use the well-characterized, inducible heat-shock response to test whether expressing additional copies of the Hsp70 gene increases energetic demand in Drosophila melanogaster. Results We measured metabolic rates of larvae with different copy numbers of the Hsp70 gene to quantify energy expenditure before, during, and after exposure to 36°C, a temperature known to induce robust expression of Hsp70. We observed a rise in metabolic rate within the first 30 minutes of 36°C exposure above and beyond the increase in routine metabolic rate at 36°C. The magnitude of this increase in metabolic rate was positively correlated with Hsp70 gene copy number and reflected an increase as great as 35% of the 22°C metabolic rate. Gene copy number also affected Hsp70 mRNA levels as early as 15 minutes after larvae were placed at 36°C, demonstrating that gene copy number affects transcript abundance on the same timescale as the metabolic effects that we observed. Inducing Hsp70 also had lasting physiological costs, as larvae had significantly depressed metabolic rate when returned to 22°C after induction. Conclusions Our results demonstrate both immediate and persistent energetic consequences of gene copy number in a multicellular organism. We discuss these consequences in the context of existing literature on the pleiotropic effects of variation in Hsp70 copy number, and argue that the increased energetic demand of expressing extra copies of Hsp70 may contribute to known tradeoffs in physiological performance of extra-copy larvae. Physiological costs of mutations that greatly increase gene expression, such as these, may constrain their utility for adaptive evolution.
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Affiliation(s)
- Luke A Hoekstra
- Department of Biology, Indiana University, Bloomington, IN 47405, USA.
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Temperature and neuronal circuit function: compensation, tuning and tolerance. Curr Opin Neurobiol 2012; 22:724-34. [DOI: 10.1016/j.conb.2012.01.008] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Revised: 01/18/2012] [Accepted: 01/19/2012] [Indexed: 01/24/2023]
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Abstract
Most neurons fire in bursts, imposing episodic energy demands, but how these demands are coordinated with oxidative phosphorylation is still unknown. Here, using fluorescence imaging techniques on presynaptic termini of Drosophila motor neurons (MNs), we show that mitochondrial matrix pH (pHm), inner membrane potential (Δψm), and NAD(P)H levels ([NAD(P)H]m) increase within seconds of nerve stimulation. The elevations of pHm, Δψm, and [NAD(P)H]m indicate an increased capacity for ATP production. Elevations in pHm were blocked by manipulations that blocked mitochondrial Ca2+ uptake, including replacement of extracellular Ca2+ with Sr2+ and application of either tetraphenylphosphonium chloride or KB-R7943, indicating that it is Ca2+ that stimulates presynaptic mitochondrial energy metabolism. To place this phenomenon within the context of endogenous neuronal activity, the firing rates of a number of individually identified MNs were determined during fictive locomotion. Surprisingly, although endogenous firing rates are significantly different, there was little difference in presynaptic cytosolic Ca2+ levels ([Ca2+]c) between MNs when each fires at its endogenous rate. The average [Ca2+]c level (329±11 nM) was slightly above the average Ca2+ affinity of the mitochondria (281±13 nM). In summary, we show that when MNs fire at endogenous rates, [Ca2+]c is driven into a range where mitochondria rapidly acquire Ca2+. As we also show that Ca2+ stimulates presynaptic mitochondrial energy metabolism, we conclude that [Ca2+]c levels play an integral role in coordinating mitochondrial energy metabolism with presynaptic activity in Drosophila MNs.
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Iyengar BG, Chou CJ, Vandamme KM, Klose MK, Zhao X, Akhtar-Danesh N, Campos AR, Atwood HL. Silencing synaptic communication between random interneurons duringDrosophilalarval locomotion. GENES BRAIN AND BEHAVIOR 2011; 10:883-900. [DOI: 10.1111/j.1601-183x.2011.00729.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Carmel J, Rashkovetsky E, Nevo E, Korol A. Differential Expression of Small Heat Shock Protein Genes Hsp23 and Hsp40, and heat shock gene Hsr-omega in Fruit Flies (Drosophila melanogaster) along a Microclimatic Gradient. J Hered 2011; 102:593-603. [DOI: 10.1093/jhered/esr027] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Hückesfeld S, Niederegger S, Schlegel P, Heinzel HG, Spiess R. Feel the heat: The effect of temperature on development, behavior and central pattern generation in 3rd instar Calliphora vicina larvae. JOURNAL OF INSECT PHYSIOLOGY 2011; 57:136-146. [PMID: 20965195 DOI: 10.1016/j.jinsphys.2010.10.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 10/11/2010] [Accepted: 10/11/2010] [Indexed: 05/30/2023]
Abstract
Like in all poikilothermic animals, higher temperatures increase developmental rate and activity in Calliphora vicina larvae. We therefore could expect temperature to have a persistent effect on the output of the feeding and crawling central pattern generators (CPGs). When confronted with a steep temperature gradient, larvae show evasive behavior after touching the substrate with the cephalic sense organs. Beside this reflex behavior the terminal- and dorsal organ might also mediate long term CPG modulation. Both organs were thermally stimulated while their response was recorded from the maxillary- or antennal nerve. The terminal organ showed a tonic response characteristic while the dorsal organ was not sensitive to temperature. Thermal stimulation of the terminal organ did not affect the ongoing patterns of fictive feeding or crawling, recorded from the antennal- or abdominal nerve respectively. A selective increase of the central nervous system (CNS) temperature accelerated the motor patterns of both feeding and crawling. We propose that temperature affects centrally generated behavior via two pathways: short term changes like thermotaxis are mediated by the terminal organ, while long term adaptations like increased feeding rate are caused by temperature sensitive neurons in the CNS which were recently shown to exist in Drosophila larvae.
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Affiliation(s)
- Sebastian Hückesfeld
- Zoologisches Institut der Universität Bonn, Abteilung Neurobiologie, Poppelsdorfer Schloß, 53115 Bonn, Germany
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Peptide-induced modulation of synaptic transmission and escape response in Drosophila requires two G-protein-coupled receptors. J Neurosci 2010; 30:14724-34. [PMID: 21048131 DOI: 10.1523/jneurosci.3612-10.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neuropeptides are found in both mammals and invertebrates and can modulate neural function through activation of G-protein-coupled receptors (GPCRS). The precise mechanisms by which many of these GPCRs modulate specific signaling cascades to regulate neural function are not well defined. We used Drosophila melanogaster as a model to examine both the cellular and behavioral effects of DPKQDFMRFamide, the most abundant peptide encoded by the dFMRF gene. We show that DPKQDFMRFamide enhanced synaptic transmission through activation of two G-protein-coupled receptors, Fmrf Receptor (FR) and Dromyosupressin Receptor-2 (DmsR-2). The peptide increased both the presynaptic Ca(2+) response and the quantal content of released transmitter. Peptide-induced modulation of synaptic function could be abrogated by depleting intracellular Ca(2+) stores or by interfering with Ca(2+) release from the endoplasmic reticulum through disruption of either the ryanodine receptor or the inositol 1,4,5-trisphosphate receptor. The peptide also altered behavior. Exogenous DPKQDFMRFamide enhanced fictive locomotion; this required both the FR and DmsR-2. Likewise, both receptors were required for an escape response to intense light exposure. Thus, coincident detection of a peptide by two GPCRs modulates synaptic function through effects of Ca(2+)-induced Ca(2+) release, and we hypothesize that these mechanisms are involved in behavioral responses to environmental stress.
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Niederegger S, Pastuschek J, Mall G. Preliminary studies of the influence of fluctuating temperatures on the development of various forensically relevant flies. Forensic Sci Int 2010; 199:72-8. [DOI: 10.1016/j.forsciint.2010.03.015] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 03/03/2010] [Accepted: 03/10/2010] [Indexed: 11/27/2022]
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Presynaptic mitochondria in functionally different motor neurons exhibit similar affinities for Ca2+ but exert little influence as Ca2+ buffers at nerve firing rates in situ. J Neurosci 2010; 30:1869-81. [PMID: 20130196 DOI: 10.1523/jneurosci.4701-09.2010] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Mitochondria accumulate within nerve terminals and support synaptic function, most notably through ATP production. They can also sequester Ca(2+) during nerve stimulation, but it is unknown whether this limits presynaptic Ca(2+) levels at physiological nerve firing rates. Similarly, it is unclear whether mitochondrial Ca(2+) sequestration differs between functionally different nerve terminals. We addressed these questions using a combination of synthetic and genetically encoded Ca(2+) indicators to examine cytosolic and mitochondrial Ca(2+) levels in presynaptic terminals of tonic (MN13-Ib) and phasic (MNSNb/d-Is) motor neurons in Drosophila, which, as we determined, fire during fictive locomotion at approximately 42 Hz and approximately 8 Hz, respectively. Mitochondrial Ca(2+) sequestration starts in both terminals at approximately 250 nM, exhibits a similar Ca(2+)-uptake affinity (approximately 410 nM), and does not require Ca(2+) release from the endoplasmic reticulum. Nonetheless, mitochondrial Ca(2+) uptake in type Is terminals is more responsive to low-frequency nerve stimulation and this is due to higher cytosolic Ca(2+) levels. Since type Ib terminals have a higher mitochondrial density than Is terminals, it seemed possible that greater mitochondrial Ca(2+) sequestration may be responsible for the lower cytosolic Ca(2+) levels in Ib terminals. However, genetic and pharmacological manipulations of mitochondrial Ca(2+) uptake did not significantly alter nerve-stimulated elevations in cytosolic Ca(2+) levels in either terminal type within physiologically relevant rates of stimulation. Our findings indicate that presynaptic mitochondria have a similar affinity for Ca(2+) in functionally different nerve terminals, but do not limit cytosolic Ca(2+) levels within the range of motor neuron firing rates in situ.
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Klose MK, Boulianne GL, Robertson RM, Atwood HL. Role of ATP-dependent calcium regulation in modulation of Drosophila synaptic thermotolerance. J Neurophysiol 2009; 102:901-13. [PMID: 19474168 DOI: 10.1152/jn.91209.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Maintenance of synaptic transmission requires regulation of intracellular Ca(2+) in presynaptic nerve terminals; loss of this regulation at elevated temperatures may cause synaptic failure. Accordingly, we examined the thermosensitivity of presynaptic calcium regulation in Drosophila larval neuromuscular junctions, testing for effects of disrupting calcium clearance. Motor neurons were loaded with the ratiometric Ca(2+) indicator Fura-dextran to monitor calcium regulation as temperature increased. Block of the Na(+)/Ca(2+) exchanger or removal of extracellular Ca(2+) prevented the normal temperature-induced increase in resting calcium. Conversely, two treatments that interfered with Ca(2+) clearance-inactivation of the endoplasmic reticulum Ca(2+)-ATPase with thapsigargin and inhibition of the plasma membrane Ca(2+)-ATPase with high pH-significantly accelerated the temperature-induced rise in resting Ca(2+) concentration and reduced the thermotolerance of synaptic transmission. Disrupting Ca(2+)-ATPase function by interfering with energy production also facilitated the temperature-induced rise in resting [Ca(2+)] and reduced thermotolerance of synaptic transmission. Conversely, fortifying energy levels with extra intracellular ATP extended the operating temperature range of both synaptic transmission and Ca(2+) regulation. In each of these cases, Ca(2+) elevations evoked by an electrical stimulation of the nerve (evoked Ca(2+) responses) failed when resting Ca(2+) remained >e 200 nM for several minutes. Failure of synaptic function was correlated with the release of intracellular calcium stores, and we provide evidence suggesting that release from the mitochondria disrupts evoked calcium responses and synaptic transmission. Thus the thermal limit of synaptic transmission may be directly linked to the stability of ATP-dependent mechanisms that regulate intracellular ion concentrations in the nerve terminal.
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Affiliation(s)
- M K Klose
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada.
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21
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Natural Variation in Drosophila Stressed Locomotion Meets or Exceeds Variation Caused by Hsp70 Mutation: Analysis of Behavior and Performance. Behav Genet 2009; 39:306-20. [DOI: 10.1007/s10519-009-9256-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2008] [Accepted: 02/04/2009] [Indexed: 10/21/2022]
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22
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Fei GH, Feng ZP. Chronic hypoxia-induced alteration of presynaptic protein profiles and neurobehavioral dysfunction are averted by supplemental oxygen in Lymnaea stagnalis. Neuroscience 2008; 153:318-28. [DOI: 10.1016/j.neuroscience.2008.01.038] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Revised: 01/16/2008] [Accepted: 01/28/2008] [Indexed: 11/28/2022]
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23
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Rand MD, Bland CE, Bond J. Methylmercury activates enhancer-of-split and bearded complex genes independent of the notch receptor. Toxicol Sci 2008; 104:163-76. [PMID: 18367466 DOI: 10.1093/toxsci/kfn060] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Methylmercury (MeHg) is a persistent environmental toxin that has targeted effects on fetal neural development. Although a number of cytotoxic mechanisms of MeHg have been characterized in cultured cells, its mode of action in the developing nervous system in vivo is less clear. Studies of MeHg-affected rodent and human brains show disrupted cortical and cerebellar architecture suggestive of mechanisms that augment cell signaling pathways potentially affecting cell migration and proliferation. We previously identified the Notch receptor pathway, a highly conserved signaling mechanism fundamental for neural development, as a target for MeHg-induced signaling in Drosophila neural cell lines. Here we have expanded our use of the Drosophila model to resolve a broader spectrum of transcriptional changes resulting from MeHg exposure in vivo and in vitro. Several Notch target genes within the Enhancer-of-split (E(spl)C) and Bearded (BrdC) complexes are upregulated with MeHg exposure in the embryo and in cultured neural cells. However, the profile of MeHg-induced E(spl)C and BrdC gene expression differs significantly from that seen with activation of the Notch receptor. Targeted knockdown of Notch and of the downstream coactivator Suppressor of Hairless (Su(H)), shows no effect on MeHg-induced transcription, indicating a novel Notch-independent mechanism of action for MeHg. MeHg transcriptional activation is partially mimicked by iodoacetamide but not by N-ethylmaleimide, two thiol-specific electrophiles, revealing a degree of specificity of cellular thiol targets in MeHg-induced transcriptional events.
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Affiliation(s)
- Matthew D Rand
- Department of Anatomy and Neurobiology, College of Medicine, University of Vermont, Burlington, VT 05405, USA.
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24
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Mileva-Seitz V, Xiao C, Seroude L, Robertson RM. Tissue-specific targeting of Hsp26 has no effect on heat resistance of neural function in larval Drosophila. Cell Stress Chaperones 2008; 13:85-95. [PMID: 18347945 PMCID: PMC2666220 DOI: 10.1007/s12192-008-0016-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Revised: 09/10/2007] [Accepted: 09/11/2007] [Indexed: 11/29/2022] Open
Abstract
Hsp26 belongs to the small heat-shock protein family and is normally expressed in all cells during heat stress. We aimed to determine if overexpression of this protein protects behavior and neural function in Drosophila melanogaster during heat stress, as has previously been shown for Hsp70. We used the UAS-GAL4 expression system to drive expression of Hsp26 in the whole animal (ubiquitously), in the motoneurons, and in the muscles of wandering third-instar larvae. There were slight increases in time to crawling failure and normalized excitatory junction potential (EJP) area for some of the transgenic lines, but these were not consistent. In addition, Hsp26 had no effect on the temperature at failure of EJPs, normalized EJP peak amplitude, and normalized EJP half-width. Overexpression larvae had a similar number of motoneuronal boutons and length of nerve terminals as controls, indicating that the occasional protective effects on locomotion were not due to changes at the synapse. We conclude that overexpression had a small thermoprotective effect on locomotion and no effect on neural function. As it has been shown that Hsp26 requires action of other Hsps to reactivate the denatured proteins to which it binds, we propose that at least in larvae, the function of Hsp26 was masked in the relative absence of other Hsps.
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Affiliation(s)
- Viara Mileva-Seitz
- Department of Biology, Queen’s University, Kingston, ON K7L 3N6 Canada
- Institute of Medical Science, University of Toronto, 7213 Medical Sciences Building, 1 King’s College Circle, Toronto, ON M5S 1A8 Canada
| | - Chengfeng Xiao
- Department of Biology, Queen’s University, Kingston, ON K7L 3N6 Canada
| | - Laurent Seroude
- Department of Biology, Queen’s University, Kingston, ON K7L 3N6 Canada
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Klose MK, Atwood HL, Robertson RM. Hyperthermic preconditioning of presynaptic calcium regulation in Drosophila. J Neurophysiol 2008; 99:2420-30. [PMID: 18272873 DOI: 10.1152/jn.01251.2007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the thermosensitivity of calcium regulation in Drosophila larval neuromuscular junctions, testing effects of prior heat shock and Hsp70 expression. Motor neurons were loaded with either the ratiometric indicator Fura-dextran or the nonratiometric indicator Oregon Green bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid to monitor parameters of calcium regulation as temperature increased. Nerve terminals treated to a prior heat shock, and those of transgenic flies expressing higher than normal levels of Hsp70, were better able to maintain near-normal resting calcium concentrations, calcium influx, and calcium clearance at higher temperatures. Synaptic transmission was also protected by prior heat shock and by higher than normal Hsp70 expression. Thus the thermal limit of synaptic transmission may be directly linked to the stability of calcium regulation.
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Affiliation(s)
- M K Klose
- Department of Physiology, University of Toronto, 1 King's College Circle, Ontario, Canada.
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26
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Shakiryanova D, Klose MK, Zhou Y, Gu T, Deitcher DL, Atwood HL, Hewes RS, Levitan ES. Presynaptic ryanodine receptor-activated calmodulin kinase II increases vesicle mobility and potentiates neuropeptide release. J Neurosci 2007; 27:7799-806. [PMID: 17634373 PMCID: PMC6672873 DOI: 10.1523/jneurosci.1879-07.2007] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although it has been postulated that vesicle mobility is increased to enhance release of transmitters and neuropeptides, the mechanism responsible for increasing vesicle motion in nerve terminals and the effect of perturbing this mobilization on synaptic plasticity are unknown. Here, green fluorescent protein-tagged dense-core vesicles (DCVs) are imaged in Drosophila motor neuron terminals, where DCV mobility is increased for minutes after seconds of activity. Ca2+-induced Ca2+ release from presynaptic endoplasmic reticulum (ER) is shown to be necessary and sufficient for sustained DCV mobilization. However, this ryanodine receptor (RyR)-mediated effect is short-lived and only initiates signaling. Calmodulin kinase II (CaMKII), which is not activated directly by external Ca2+ influx, then acts as a downstream effector of released ER Ca2+. RyR and CaMKII are essential for post-tetanic potentiation of neuropeptide secretion. Therefore, the presynaptic signaling pathway for increasing DCV mobility is identified and shown to be required for synaptic plasticity.
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Affiliation(s)
- Dinara Shakiryanova
- Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Markus K. Klose
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Yi Zhou
- Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Tingting Gu
- Departments of Zoology and Cell Biology, University of Oklahoma, Norman, Oklahoma 73019, and
| | - David L. Deitcher
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853
| | - Harold L. Atwood
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Randall S. Hewes
- Departments of Zoology and Cell Biology, University of Oklahoma, Norman, Oklahoma 73019, and
| | - Edwin S. Levitan
- Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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27
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Rank NE, Bruce DA, McMillan DM, Barclay C, Dahlhoff EP. Phosphoglucose isomerase genotype affects running speed and heat shock protein expression after exposure to extreme temperatures in a montane willow beetle. ACTA ACUST UNITED AC 2007; 210:750-64. [PMID: 17297136 DOI: 10.1242/jeb.02695] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Eastern Sierra Nevada populations of the willow beetle Chrysomela aeneicollis commonly experience stressfully high and low environmental temperatures that may influence survival and reproduction. Allele frequencies at the enzyme locus phosphoglucose isomerase (PGI) vary across a climatic latitudinal gradient in these populations, with PGI allele 1 being most common in cooler regions and PGI allele 4 in warmer ones. PGI genotypes differ in heat and cold tolerance and in expression of a 70 kDa heat shock protein. Here we examine genetic, behavioral and environmental factors affecting a performance character, running speed, for willow beetles, and assess effects of consecutive cold and heat exposure on running speed and expression of Hsp70 in the laboratory. In nature, running speed depends on air temperature and is higher for males than females. Mating beetles ran faster than single beetles, and differences among PGI genotypes in male running speed depended on the presence of females. In the laboratory, exposure to cold reduced subsequent running speed, but the amount of this reduction depended on PGI genotype and previous thermal history. Effects of exposure to heat also depended on life history stage and PGI genotype. Adults possessing allele 1 ran fastest after a single exposure to stressful temperature, whereas those possessing allele 4 ran faster after repeated exposure. Larvae possessing allele 4 ran fastest after a single stressful exposure, but running speed generally declined after a second exposure to stressful temperature. The ranking of PGI genotypes after the second exposure depended on whether a larva had been exposed to cold or heat. Effects of temperature on Hsp70 expression also varied among PGI genotypes and depended on type of exposure, especially for adults (single heat exposure, two cold exposures: PGI 1-1>1-4>4-4; other multiple extreme exposures: 4-4>1-4>1-1). There was no consistent association between alleles at other polymorphic enzyme loci and running speed or Hsp70 expression. These data suggest that variation at PGI is associated with considerable plasticity in running speed. Differences in Hsp70 expression among PGI genotypes suggest that the heat-shock response may buffer differences in thermal tolerance and performance among genotypes and help maintain the PGI polymorphism in a thermally variable environment.
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Affiliation(s)
- Nathan E Rank
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, USA.
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28
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Xiao C, Mileva-Seitz V, Seroude L, Robertson RM. Targeting HSP70 to motoneurons protects locomotor activity from hyperthermia in Drosophila. Dev Neurobiol 2007; 67:438-55. [PMID: 17443800 DOI: 10.1002/dneu.20344] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Heat shock preconditioning can enhance locomotor and synaptic performance during subsequent hyperthermia. The molecular basis underlying this neural phenotypic modification is largely unknown. Here we report that directing the expression of the 70 kDa heat shock protein (HSP70) to motoneurons protected larval locomotor activity of Drosophila. Tissue-specific expression showed that motoneurons were critical for developing HSP70-mediated thermoprotection of locomotor activity, whereas peripheral sensory neurons, dopaminergic neurons, serotonergic neurons, and muscle cells alone were insufficient. Targeting HSP70 to motoneurons caused structural plasticity of axonal terminals associated with increased transmitter release at neuromuscular junctions at high temperature. The thermoprotection induced by motoneuronal expression of HSP70 mimicked the protective effect of a prior heat shock (36 degrees C, 1 h; 25 degrees C, 1 h) but the effects of heat shock and motoneuronal expression of HSP70 were not additive. In the absence of heat shock pretreatment, ubiquitously expressed transgenic HSP70 activated the transcription of endogenous hsp70 genes. These results demonstrate that motoneurons were critical for HSP70-mediated thermoprotection, and that transgenic HSP70 activated the transcription of endogenous hsp70 in motoneurons with the result that a mix of transgenic and endogenous HSP70 conferred thermoprotection in Drosophila larva.
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Affiliation(s)
- Chengfeng Xiao
- Department of Biology, Queen's University, Kingston, Ontario K7L 3N6 Canada
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29
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Song W, Onishi M, Jan LY, Jan YN. Peripheral multidendritic sensory neurons are necessary for rhythmic locomotion behavior in Drosophila larvae. Proc Natl Acad Sci U S A 2007; 104:5199-204. [PMID: 17360325 PMCID: PMC1820883 DOI: 10.1073/pnas.0700895104] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
From breathing to walking, rhythmic movements encompass physiological processes important across the entire animal kingdom. It is thought by many that the generation of rhythmic behavior is operated by a central pattern generator (CPG) and does not require peripheral sensory input. Sensory feedback is, however, required to modify or coordinate the motor activity in response to the circumstances of actual movement. In contrast to this notion, we report here that sensory input is necessary for the generation of Drosophila larval locomotion, a form of rhythmic behavior. Blockage of all peripheral sensory inputs resulted in cessation of larval crawling. By conditionally silencing various subsets of larval peripheral sensory neurons, we identified the multiple dendritic (MD) neurons as the neurons essential for the generation of rhythmic peristaltic locomotion. By recording the locomotive motor activities, we further demonstrate that removal of MD neuron input disrupted rhythmic motor firing pattern in a way that prolonged the stereotyped segmental motor firing duration and prevented the propagation of posterior to anterior segmental motor firing. These findings reveal that MD sensory neuron input is a necessary component in the neural circuitry that generates larval locomotion.
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Affiliation(s)
- Wei Song
- Departments of Physiology and Biochemistry, Howard Hughes Medical Institute, University of California, San Francisco, CA 94143
| | - Maika Onishi
- Departments of Physiology and Biochemistry, Howard Hughes Medical Institute, University of California, San Francisco, CA 94143
| | - Lily Yeh Jan
- Departments of Physiology and Biochemistry, Howard Hughes Medical Institute, University of California, San Francisco, CA 94143
| | - Yuh Nung Jan
- Departments of Physiology and Biochemistry, Howard Hughes Medical Institute, University of California, San Francisco, CA 94143
- *To whom correspondence should be addressed. E-mail:
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Fei G, Guo C, Sun HS, Feng ZP. Chronic hypoxia stress-induced differential modulation of heat-shock protein 70 and presynaptic proteins. J Neurochem 2007; 100:50-61. [PMID: 17227434 DOI: 10.1111/j.1471-4159.2006.04194.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Chronic hypoxia exposure can cause neurobehavioral dysfunction, but the underlying cellular and molecular mechanisms remain unclear. Here, we found that adult Lymnaea stagnalis snails maintained in low O(2) (approximately 5%) for 4 days developed slowed reactions to light stimuli, and reduced righting movement. Semiquantitative immunoblotting analyses showed that hypoxia exposure induced increased expression of heat-shock protein (HSP)70 in ganglion preparations, and suppressed expression of the presynaptic proteins syntaxin I, synaptic vesicle protein 2 (SV2) and synaptotagmin I. Detailed time course analyses showed that an early moderate increase developed within 6 h, preceding a substantial up-regulation of HSP70 after 4 days; an early reduction of syntaxin I in the first 24 h; a delayed reduction of synaptotagmin I after 4 days; and a biphasic change in SV2. Using a double-stranded RNA interference approach, we demonstrated that preventing the hypoxia inducible HSP70 enhanced down-regulation of syntaxin and synaptotagmin, and aggravated motor and sensory suppression. Co-immunoprecipitation analysis revealed an interaction between HSP70 and syntaxin. We have thus provided the first evidence that early induction of HSP70 by chronic hypoxia is critical for maintaining expression levels of presynaptic proteins. These findings implicate a new molecular mechanism underlying chronic hypoxia-induced neurobehavioral adaptation and impairment.
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Affiliation(s)
- Guanghe Fei
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
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