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Rozenfeld E, Ehmann N, Manoim JE, Kittel RJ, Parnas M. Homeostatic synaptic plasticity rescues neural coding reliability. Nat Commun 2023; 14:2993. [PMID: 37225688 DOI: 10.1038/s41467-023-38575-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Accepted: 05/08/2023] [Indexed: 05/26/2023] Open
Abstract
To survive, animals must recognize reoccurring stimuli. This necessitates a reliable stimulus representation by the neural code. While synaptic transmission underlies the propagation of neural codes, it is unclear how synaptic plasticity can maintain coding reliability. By studying the olfactory system of Drosophila melanogaster, we aimed to obtain a deeper mechanistic understanding of how synaptic function shapes neural coding in the live, behaving animal. We show that the properties of the active zone (AZ), the presynaptic site of neurotransmitter release, are critical for generating a reliable neural code. Reducing neurotransmitter release probability of olfactory sensory neurons disrupts both neural coding and behavioral reliability. Strikingly, a target-specific homeostatic increase of AZ numbers rescues these defects within a day. These findings demonstrate an important role for synaptic plasticity in maintaining neural coding reliability and are of pathophysiological interest by uncovering an elegant mechanism through which the neural circuitry can counterbalance perturbations.
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Affiliation(s)
- Eyal Rozenfeld
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Nadine Ehmann
- Department of Animal Physiology, Institute of Biology, Leipzig University, 04103, Leipzig, Germany
| | - Julia E Manoim
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Robert J Kittel
- Department of Animal Physiology, Institute of Biology, Leipzig University, 04103, Leipzig, Germany.
| | - Moshe Parnas
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel.
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel.
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2
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Dannhäuser S, Lux TJ, Hu C, Selcho M, Chen JTC, Ehmann N, Sachidanandan D, Stopp S, Pauls D, Pawlak M, Langenhan T, Soba P, Rittner HL, Kittel RJ. Antinociceptive modulation by the adhesion GPCR CIRL promotes mechanosensory signal discrimination. eLife 2020; 9:e56738. [PMID: 32996461 PMCID: PMC7546736 DOI: 10.7554/elife.56738] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 09/17/2020] [Indexed: 12/17/2022] Open
Abstract
Adhesion-type GPCRs (aGPCRs) participate in a vast range of physiological processes. Their frequent association with mechanosensitive functions suggests that processing of mechanical stimuli may be a common feature of this receptor family. Previously, we reported that the Drosophila aGPCR CIRL sensitizes sensory responses to gentle touch and sound by amplifying signal transduction in low-threshold mechanoreceptors (Scholz et al., 2017). Here, we show that Cirl is also expressed in high-threshold mechanical nociceptors where it adjusts nocifensive behaviour under physiological and pathological conditions. Optogenetic in vivo experiments indicate that CIRL lowers cAMP levels in both mechanosensory submodalities. However, contrasting its role in touch-sensitive neurons, CIRL dampens the response of nociceptors to mechanical stimulation. Consistent with this finding, rat nociceptors display decreased Cirl1 expression during allodynia. Thus, cAMP-downregulation by CIRL exerts opposing effects on low-threshold mechanosensors and high-threshold nociceptors. This intriguing bipolar action facilitates the separation of mechanosensory signals carrying different physiological information.
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Affiliation(s)
- Sven Dannhäuser
- Department of Animal Physiology, Institute of Biology, Leipzig UniversityLeipzigGermany
- Carl-Ludwig-Institute for Physiology, Leipzig UniversityLeipzigGermany
| | - Thomas J Lux
- Center for Interdisciplinary Pain Medicine, Department of Anaesthesiology, University Hospital WürzburgWürzburgGermany
| | - Chun Hu
- Neuronal Patterning and Connectivity, Center for Molecular Neurobiology, University Medical Center Hamburg-EppendorfHamburgGermany
| | - Mareike Selcho
- Department of Animal Physiology, Institute of Biology, Leipzig UniversityLeipzigGermany
- Carl-Ludwig-Institute for Physiology, Leipzig UniversityLeipzigGermany
| | - Jeremy T-C Chen
- Center for Interdisciplinary Pain Medicine, Department of Anaesthesiology, University Hospital WürzburgWürzburgGermany
| | - Nadine Ehmann
- Department of Animal Physiology, Institute of Biology, Leipzig UniversityLeipzigGermany
- Carl-Ludwig-Institute for Physiology, Leipzig UniversityLeipzigGermany
| | - Divya Sachidanandan
- Department of Animal Physiology, Institute of Biology, Leipzig UniversityLeipzigGermany
- Carl-Ludwig-Institute for Physiology, Leipzig UniversityLeipzigGermany
| | - Sarah Stopp
- Department of Animal Physiology, Institute of Biology, Leipzig UniversityLeipzigGermany
- Carl-Ludwig-Institute for Physiology, Leipzig UniversityLeipzigGermany
| | - Dennis Pauls
- Department of Animal Physiology, Institute of Biology, Leipzig UniversityLeipzigGermany
- Carl-Ludwig-Institute for Physiology, Leipzig UniversityLeipzigGermany
| | - Matthias Pawlak
- Department of Neurophysiology, Institute of Physiology, University of WürzburgWürzburgGermany
| | - Tobias Langenhan
- Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Medical Faculty, Leipzig UniversityLeipzigGermany
| | - Peter Soba
- Neuronal Patterning and Connectivity, Center for Molecular Neurobiology, University Medical Center Hamburg-EppendorfHamburgGermany
| | - Heike L Rittner
- Center for Interdisciplinary Pain Medicine, Department of Anaesthesiology, University Hospital WürzburgWürzburgGermany
| | - Robert J Kittel
- Department of Animal Physiology, Institute of Biology, Leipzig UniversityLeipzigGermany
- Carl-Ludwig-Institute for Physiology, Leipzig UniversityLeipzigGermany
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3
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Affiliation(s)
- Nadine Ehmann
- Department of Animal Physiology, Institute of Biology, Leipzig University, Leipzig, Germany
| | - Dennis Pauls
- Department of Animal Physiology, Institute of Biology, Leipzig University, Leipzig, Germany
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4
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Blanco-Redondo B, Nuwal N, Kneitz S, Nuwal T, Halder P, Liu Y, Ehmann N, Scholz N, Mayer A, Kleber J, Kähne T, Schmitt D, Sadanandappa MK, Funk N, Albertova V, Helfrich-Förster C, Ramaswami M, Hasan G, Kittel RJ, Langenhan T, Gerber B, Buchner E. Implications of the Sap47 null mutation for synapsin phosphorylation, longevity, climbing proficiency and behavioural plasticity in adult Drosophila. ACTA ACUST UNITED AC 2019; 222:jeb.203505. [PMID: 31488622 DOI: 10.1242/jeb.203505] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 08/29/2019] [Indexed: 12/18/2022]
Abstract
The Sap47 gene of Drosophila melanogaster encodes a highly abundant 47 kDa synaptic vesicle-associated protein. Sap47 null mutants show defects in synaptic plasticity and larval olfactory associative learning but the molecular function of Sap47 at the synapse is unknown. We demonstrate that Sap47 modulates the phosphorylation of another highly abundant conserved presynaptic protein, synapsin. Site-specific phosphorylation of Drosophila synapsin has repeatedly been shown to be important for behavioural plasticity but it was not known where these phospho-synapsin isoforms are localized in the brain. Here, we report the distribution of serine-6-phosphorylated synapsin in the adult brain and show that it is highly enriched in rings of synapses in the ellipsoid body and in large synapses near the lateral triangle. The effects of knockout of Sap47 or synapsin on olfactory associative learning/memory support the hypothesis that both proteins operate in the same molecular pathway. We therefore asked if this might also be true for other aspects of their function. We show that knockout of Sap47 but not synapsin reduces lifespan, whereas knockout of Sap47 and synapsin, either individually or together, affects climbing proficiency, as well as plasticity in circadian rhythms and sleep. Furthermore, electrophysiological assessment of synaptic properties at the larval neuromuscular junction (NMJ) reveals increased spontaneous synaptic vesicle fusion and reduced paired pulse facilitation in Sap47 and synapsin single and double mutants. Our results imply that Sap47 and synapsin cooperate non-uniformly in the control of synaptic properties in different behaviourally relevant neuronal networks of the fruitfly.
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Affiliation(s)
- Beatriz Blanco-Redondo
- Institute of Clinical Neurobiology, University of Würzburg, 97078 Würzburg, Germany .,Department of Neurobiology and Genetics, Biocenter of the University of Würzburg, 97074 Würzburg, Germany.,Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Leipzig University, 04103 Leipzig, Germany
| | - Nidhi Nuwal
- Department of Neurobiology and Genetics, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Susanne Kneitz
- Department of Physiological Chemistry, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Tulip Nuwal
- Department of Neurobiology and Genetics, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Partho Halder
- Department of Neurobiology and Genetics, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Yiting Liu
- Department of Neurobiology and Genetics, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Nadine Ehmann
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, 97070 Würzburg, Germany.,Department of Animal Physiology, Institute of Biology, Leipzig University, 04103 Leipzig, Germany.,Carl-Ludwig-Institute for Physiology, Leipzig University, 04103 Leipzig, Germany
| | - Nicole Scholz
- Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Leipzig University, 04103 Leipzig, Germany.,Department of Neurophysiology, Institute of Physiology, University of Würzburg, 97070 Würzburg, Germany
| | - Annika Mayer
- Institute of Clinical Neurobiology, University of Würzburg, 97078 Würzburg, Germany
| | - Jörg Kleber
- Leibniz Institute of Neurobiology, 39118 Magdeburg, Germany
| | - Thilo Kähne
- Institute of Experimental Internal Medicine, Otto von Guericke University, 39120 Magdeburg, Germany
| | - Dominique Schmitt
- Institute of Clinical Neurobiology, University of Würzburg, 97078 Würzburg, Germany
| | - Madhumala K Sadanandappa
- Institute of Clinical Neurobiology, University of Würzburg, 97078 Würzburg, Germany.,National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka 560065, India
| | - Natalja Funk
- Department of Neurobiology and Genetics, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Viera Albertova
- Institute of Clinical Neurobiology, University of Würzburg, 97078 Würzburg, Germany.,Department of Neurobiology and Genetics, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Charlotte Helfrich-Förster
- Department of Neurobiology and Genetics, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
| | - Mani Ramaswami
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka 560065, India
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka 560065, India
| | - Robert J Kittel
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, 97070 Würzburg, Germany.,Department of Animal Physiology, Institute of Biology, Leipzig University, 04103 Leipzig, Germany.,Carl-Ludwig-Institute for Physiology, Leipzig University, 04103 Leipzig, Germany
| | - Tobias Langenhan
- Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Leipzig University, 04103 Leipzig, Germany.,Department of Neurophysiology, Institute of Physiology, University of Würzburg, 97070 Würzburg, Germany
| | - Bertram Gerber
- Leibniz Institute of Neurobiology, 39118 Magdeburg, Germany.,Institute of Biology, University of Magdeburg, 39120 Magdeburg, Germany.,Center for Behavioral Brain Sciences, 39106 Magdeburg, Germany
| | - Erich Buchner
- Institute of Clinical Neurobiology, University of Würzburg, 97078 Würzburg, Germany .,Department of Neurobiology and Genetics, Biocenter of the University of Würzburg, 97074 Würzburg, Germany
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5
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Scholz N, Ehmann N, Sachidanandan D, Imig C, Cooper BH, Jahn O, Reim K, Brose N, Meyer J, Lamberty M, Altrichter S, Bormann A, Hallermann S, Pauli M, Heckmann M, Stigloher C, Langenhan T, Kittel RJ. Complexin cooperates with Bruchpilot to tether synaptic vesicles to the active zone cytomatrix. J Cell Biol 2019; 218:1011-1026. [PMID: 30782781 PMCID: PMC6400551 DOI: 10.1083/jcb.201806155] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 12/14/2018] [Accepted: 01/09/2019] [Indexed: 02/06/2023] Open
Abstract
By performing an in vivo screen in Drosophila melanogaster, Scholz, Ehmann, et al. identify Complexin as a functional interaction partner of Bruchpilot. The two proteins mediate a physical attachment of synaptic vesicles to the active zone cytomatrix and promote rapid, sustained synaptic transmission. Information processing by the nervous system depends on neurotransmitter release from synaptic vesicles (SVs) at the presynaptic active zone. Molecular components of the cytomatrix at the active zone (CAZ) regulate the final stages of the SV cycle preceding exocytosis and thereby shape the efficacy and plasticity of synaptic transmission. Part of this regulation is reflected by a physical association of SVs with filamentous CAZ structures via largely unknown protein interactions. The very C-terminal region of Bruchpilot (Brp), a key component of the Drosophila melanogaster CAZ, participates in SV tethering. Here, we identify the conserved SNARE regulator Complexin (Cpx) in an in vivo screen for molecules that link the Brp C terminus to SVs. Brp and Cpx interact genetically and functionally. Both proteins promote SV recruitment to the Drosophila CAZ and counteract short-term synaptic depression. Analyzing SV tethering to active zone ribbons of cpx3 knockout mice supports an evolutionarily conserved role of Cpx upstream of SNARE complex assembly.
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Affiliation(s)
- Nicole Scholz
- Institute of Physiology, Department of Neurophysiology, University of Würzburg, Würzburg, Germany.,Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Leipzig University, Leipzig, Germany
| | - Nadine Ehmann
- Institute of Physiology, Department of Neurophysiology, University of Würzburg, Würzburg, Germany.,Department of Animal Physiology, Institute of Biology, Leipzig University, Leipzig, Germany.,Carl Ludwig Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Divya Sachidanandan
- Institute of Physiology, Department of Neurophysiology, University of Würzburg, Würzburg, Germany
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Olaf Jahn
- Proteomics Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Kerstin Reim
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Jutta Meyer
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Proteomics Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Göttingen Graduate School for Neurosciences, Biophysics and Molecular Biosciences, University of Göttingen, Germany
| | - Marius Lamberty
- Institute of Physiology, Department of Neurophysiology, University of Würzburg, Würzburg, Germany.,Department of Animal Physiology, Institute of Biology, Leipzig University, Leipzig, Germany.,Carl Ludwig Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Steffen Altrichter
- Institute of Physiology, Department of Neurophysiology, University of Würzburg, Würzburg, Germany.,Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Leipzig University, Leipzig, Germany
| | - Anne Bormann
- Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Leipzig University, Leipzig, Germany
| | - Stefan Hallermann
- Carl Ludwig Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Martin Pauli
- Institute of Physiology, Department of Neurophysiology, University of Würzburg, Würzburg, Germany
| | - Manfred Heckmann
- Institute of Physiology, Department of Neurophysiology, University of Würzburg, Würzburg, Germany
| | | | - Tobias Langenhan
- Institute of Physiology, Department of Neurophysiology, University of Würzburg, Würzburg, Germany .,Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Leipzig University, Leipzig, Germany
| | - Robert J Kittel
- Institute of Physiology, Department of Neurophysiology, University of Würzburg, Würzburg, Germany .,Department of Animal Physiology, Institute of Biology, Leipzig University, Leipzig, Germany.,Carl Ludwig Institute for Physiology, Leipzig University, Leipzig, Germany
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6
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Beck S, Yu-Strzelczyk J, Pauls D, Constantin OM, Gee CE, Ehmann N, Kittel RJ, Nagel G, Gao S. Synthetic Light-Activated Ion Channels for Optogenetic Activation and Inhibition. Front Neurosci 2018; 12:643. [PMID: 30333716 PMCID: PMC6176052 DOI: 10.3389/fnins.2018.00643] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 08/29/2018] [Indexed: 01/21/2023] Open
Abstract
Optogenetic manipulation of cells or living organisms became widely used in neuroscience following the introduction of the light-gated ion channel channelrhodopsin-2 (ChR2). ChR2 is a non-selective cation channel, ideally suited to depolarize and evoke action potentials in neurons. However, its calcium (Ca2+) permeability and single channel conductance are low and for some applications longer-lasting increases in intracellular Ca2+ might be desirable. Moreover, there is need for an efficient light-gated potassium (K+) channel that can rapidly inhibit spiking in targeted neurons. Considering the importance of Ca2+ and K+ in cell physiology, light-activated Ca2+-permeant and K+-specific channels would be welcome additions to the optogenetic toolbox. Here we describe the engineering of novel light-gated Ca2+-permeant and K+-specific channels by fusing a bacterial photoactivated adenylyl cyclase to cyclic nucleotide-gated channels with high permeability for Ca2+ or for K+, respectively. Optimized fusion constructs showed strong light-gated conductance in Xenopus laevis oocytes and in rat hippocampal neurons. These constructs could also be used to control the motility of Drosophila melanogaster larvae, when expressed in motoneurons. Illumination led to body contraction when motoneurons expressed the light-sensitive Ca2+-permeant channel, and to body extension when expressing the light-sensitive K+ channel, both effectively and reversibly paralyzing the larvae. Further optimization of these constructs will be required for application in adult flies since both constructs led to eclosion failure when expressed in motoneurons.
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Affiliation(s)
- Sebastian Beck
- Julius-von-Sachs-Institute, University of Würzburg, Würzburg, Germany
| | | | - Dennis Pauls
- Neurobiology and Genetics, Theodor-Boveri Institute, Biocenter, University of Würzburg, Würzburg, Germany
| | - Oana M Constantin
- Institute for Synaptic Physiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christine E Gee
- Institute for Synaptic Physiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Nadine Ehmann
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Würzburg, Germany.,Department of Animal Physiology, Institute of Biology, Leipzig University, Leipzig, Germany.,Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Robert J Kittel
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Würzburg, Germany.,Department of Animal Physiology, Institute of Biology, Leipzig University, Leipzig, Germany.,Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Georg Nagel
- Julius-von-Sachs-Institute, University of Würzburg, Würzburg, Germany
| | - Shiqiang Gao
- Julius-von-Sachs-Institute, University of Würzburg, Würzburg, Germany
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7
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Ehmann N, Owald D, Kittel RJ. Drosophila active zones: From molecules to behaviour. Neurosci Res 2018; 127:14-24. [DOI: 10.1016/j.neures.2017.11.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 11/30/2017] [Accepted: 11/30/2017] [Indexed: 11/15/2022]
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Beck K, Ehmann N, Andlauer TFM, Ljaschenko D, Strecker K, Fischer M, Kittel RJ, Raabe T. Loss of the Coffin-Lowry syndrome-associated gene RSK2 alters ERK activity, synaptic function and axonal transport in Drosophila motoneurons. Dis Model Mech 2015; 8:1389-400. [PMID: 26398944 PMCID: PMC4631788 DOI: 10.1242/dmm.021246] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 08/27/2015] [Indexed: 01/06/2023] Open
Abstract
Plastic changes in synaptic properties are considered as fundamental for adaptive behaviors. Extracellular-signal-regulated kinase (ERK)-mediated signaling has been implicated in regulation of synaptic plasticity. Ribosomal S6 kinase 2 (RSK2) acts as a regulator and downstream effector of ERK. In the brain, RSK2 is predominantly expressed in regions required for learning and memory. Loss-of-function mutations in human RSK2 cause Coffin-Lowry syndrome, which is characterized by severe mental retardation and low IQ scores in affected males. Knockout of RSK2 in mice or the RSK ortholog in Drosophila results in a variety of learning and memory defects. However, overall brain structure in these animals is not affected, leaving open the question of the pathophysiological consequences. Using the fly neuromuscular system as a model for excitatory glutamatergic synapses, we show that removal of RSK function causes distinct defects in motoneurons and at the neuromuscular junction. Based on histochemical and electrophysiological analyses, we conclude that RSK is required for normal synaptic morphology and function. Furthermore, loss of RSK function interferes with ERK signaling at different levels. Elevated ERK activity was evident in the somata of motoneurons, whereas decreased ERK activity was observed in axons and the presynapse. In addition, we uncovered a novel function of RSK in anterograde axonal transport. Our results emphasize the importance of fine-tuning ERK activity in neuronal processes underlying higher brain functions. In this context, RSK acts as a modulator of ERK signaling.
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Affiliation(s)
- Katherina Beck
- University of Würzburg, Institute of Medical Radiation and Cell Research, Versbacherstraße 5, Würzburg D-97078, Germany
| | - Nadine Ehmann
- University of Würzburg, Institute of Physiology, Department of Neurophysiology, Röntgenring 9, Würzburg D-97070, Germany
| | - Till F M Andlauer
- University of Würzburg, Rudolf Virchow Center, DFG Research Center for Experimental Biomedicine, Josef-Schneider-Straße 2, Würzburg D-97080, Germany Freie Universität Berlin, Institute of Biology, Takusstraße 6, Berlin D-14195, Germany Max Planck Institute of Colloidals and Interfaces, Am Mühlenberg 1, Potsdam D-14476, Germany
| | - Dmitrij Ljaschenko
- University of Würzburg, Institute of Physiology, Department of Neurophysiology, Röntgenring 9, Würzburg D-97070, Germany
| | - Katrin Strecker
- University of Würzburg, Institute of Medical Radiation and Cell Research, Versbacherstraße 5, Würzburg D-97078, Germany
| | - Matthias Fischer
- University Hospital Würzburg, Department of Psychiatry, Psychosomatics and Psychotherapy, Füchsleinstraße 15, Würzburg 97080, Germany
| | - Robert J Kittel
- University of Würzburg, Institute of Physiology, Department of Neurophysiology, Röntgenring 9, Würzburg D-97070, Germany
| | - Thomas Raabe
- University of Würzburg, Institute of Medical Radiation and Cell Research, Versbacherstraße 5, Würzburg D-97078, Germany
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9
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Paul MM, Pauli M, Ehmann N, Hallermann S, Sauer M, Kittel RJ, Heckmann M. Bruchpilot and Synaptotagmin collaborate to drive rapid glutamate release and active zone differentiation. Front Cell Neurosci 2015; 9:29. [PMID: 25698934 PMCID: PMC4318344 DOI: 10.3389/fncel.2015.00029] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 01/16/2015] [Indexed: 11/13/2022] Open
Abstract
The active zone (AZ) protein Bruchpilot (Brp) is essential for rapid glutamate release at Drosophila melanogaster neuromuscular junctions (NMJs). Quantal time course and measurements of action potential-waveform suggest that presynaptic fusion mechanisms are altered in brp null mutants (brp(69) ). This could account for their increased evoked excitatory postsynaptic current (EPSC) delay and rise time (by about 1 ms). To test the mechanism of release protraction at brp(69) AZs, we performed knock-down of Synaptotagmin-1 (Syt) via RNAi (syt(KD) ) in wildtype (wt), brp(69) and rab3 null mutants (rab3(rup) ), where Brp is concentrated at a small number of AZs. At wt and rab3(rup) synapses, syt(KD) lowered EPSC amplitude while increasing rise time and delay, consistent with the role of Syt as a release sensor. In contrast, syt(KD) did not alter EPSC amplitude at brp(69) synapses, but shortened delay and rise time. In fact, following syt(KD) , these kinetic properties were strikingly similar in wt and brp(69) , which supports the notion that Syt protracts release at brp(69) synapses. To gain insight into this surprising role of Syt at brp(69) AZs, we analyzed the structural and functional differentiation of synaptic boutons at the NMJ. At 'tonic' type Ib motor neurons, distal boutons contain more AZs, more Brp proteins per AZ and show elevated and accelerated glutamate release compared to proximal boutons. The functional differentiation between proximal and distal boutons is Brp-dependent and reduced after syt(KD) . Notably, syt(KD) boutons are smaller, contain fewer Brp positive AZs and these are of similar number in proximal and distal boutons. In addition, super-resolution imaging via dSTORM revealed that syt(KD) increases the number and alters the spatial distribution of Brp molecules at AZs, while the gradient of Brp proteins per AZ is diminished. In summary, these data demonstrate that normal structural and functional differentiation of Drosophila AZs requires concerted action of Brp and Syt.
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Affiliation(s)
- Mila M Paul
- Department of Neurophysiology, Institute of Physiology, Julius-Maximilians-University Würzburg Würzburg, Germany
| | - Martin Pauli
- Department of Neurophysiology, Institute of Physiology, Julius-Maximilians-University Würzburg Würzburg, Germany
| | - Nadine Ehmann
- Department of Neurophysiology, Institute of Physiology, Julius-Maximilians-University Würzburg Würzburg, Germany
| | - Stefan Hallermann
- Carl-Ludwig-Institute for Physiology, University of Leipzig Leipzig, Germany
| | - Markus Sauer
- Department of Biotechnology and Biophysics, Julius-Maximilians-University Würzburg Würzburg, Germany
| | - Robert J Kittel
- Department of Neurophysiology, Institute of Physiology, Julius-Maximilians-University Würzburg Würzburg, Germany
| | - Manfred Heckmann
- Department of Neurophysiology, Institute of Physiology, Julius-Maximilians-University Würzburg Würzburg, Germany
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10
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Abstract
Brain function relies on accurate information transfer at chemical synapses. At the presynaptic active zone (AZ) a variety of specialized proteins are assembled to complex architectures, which set the basis for speed, precision and plasticity of synaptic transmission. Calcium channels are pivotal for the initiation of excitation-secretion coupling and, correspondingly, capture a central position at the AZ. Combining quantitative functional studies with modeling approaches has provided predictions of channel properties, numbers and even positions on the nanometer scale. However, elucidating the nanoscopic organization of the surrounding protein network requires direct ultrastructural access. Without this information, knowledge of molecular synaptic structure-function relationships remains incomplete. Recently, super-resolution microscopy (SRM) techniques have begun to enter the neurosciences. These approaches combine high spatial resolution with the molecular specificity of fluorescence microscopy. Here, we discuss how SRM can be used to obtain information on the organization of AZ proteins.
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Affiliation(s)
- Nadine Ehmann
- Department of Neurophysiology, Institute of Physiology, University of Würzburg Würzburg, Germany
| | - Markus Sauer
- Department of Biotechnology and Biophysics, University of Würzburg Würzburg, Germany
| | - Robert J Kittel
- Department of Neurophysiology, Institute of Physiology, University of Würzburg Würzburg, Germany
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Sauer M, van de Linde S, Holm T, Aufmkolk S, Ehmann N, Blum R, Bar-On D, Alon A, Ashery U, Ljaschenko D, Heckmann M, Kittel R. dSTORM of Synaptic Proteins. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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