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Weichard I, Taschenberger H, Gsell F, Bornschein G, Ritzau-Jost A, Schmidt H, Kittel RJ, Eilers J, Neher E, Hallermann S, Nerlich J. Fully-primed slowly-recovering vesicles mediate presynaptic LTP at neocortical neurons. Proc Natl Acad Sci U S A 2023; 120:e2305460120. [PMID: 37856547 PMCID: PMC10614622 DOI: 10.1073/pnas.2305460120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 08/26/2023] [Indexed: 10/21/2023] Open
Abstract
Pre- and postsynaptic forms of long-term potentiation (LTP) are candidate synaptic mechanisms underlying learning and memory. At layer 5 pyramidal neurons, LTP increases the initial synaptic strength but also short-term depression during high-frequency transmission. This classical form of presynaptic LTP has been referred to as redistribution of synaptic efficacy. However, the underlying mechanisms remain unclear. We therefore performed whole-cell recordings from layer 5 pyramidal neurons in acute cortical slices of rats and analyzed presynaptic function before and after LTP induction by paired pre- and postsynaptic neuronal activity. LTP was successfully induced in about half of the synaptic connections tested and resulted in increased synaptic short-term depression during high-frequency transmission and a decelerated recovery from short-term depression due to an increased fraction of a slow recovery component. Analysis with a recently established sequential two-step vesicle priming model indicates an increase in the abundance of fully-primed and slowly-recovering vesicles. A systematic analysis of short-term plasticity and synapse-to-synapse variability of synaptic strength at various types of synapses revealed that stronger synapses generally recover more slowly from synaptic short-term depression. Finally, pharmacological stimulation of the cyclic adenosine monophosphate and diacylglycerol signaling pathways, which are both known to promote synaptic vesicle priming, mimicked LTP and slowed the recovery from short-term depression. Our data thus demonstrate that LTP at layer 5 pyramidal neurons increases synaptic strength primarily by enlarging a subpool of fully-primed slowly-recovering vesicles.
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Affiliation(s)
- Iron Weichard
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig04103, Germany
| | - Holger Taschenberger
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen37075, Germany
| | - Felix Gsell
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig04103, Germany
| | - Grit Bornschein
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig04103, Germany
| | - Andreas Ritzau-Jost
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig04103, Germany
| | - Hartmut Schmidt
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig04103, Germany
| | - Robert J. Kittel
- Department of Animal Physiology, Institute of Biology, Leipzig University, Leipzig04103, Germany
| | - Jens Eilers
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig04103, Germany
| | - Erwin Neher
- Emeritus Laboratory of Membrane Biophysics, Max Planck Institute for Multidisciplinary Sciences, Göttingen37070, Germany
- Cluster of Excellence “Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells”, University of Göttingen, Göttingen37073, Germany
| | - Stefan Hallermann
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig04103, Germany
| | - Jana Nerlich
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig04103, Germany
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2
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Wender M, Bornschein G, Brachtendorf S, Hallermann S, Eilers J, Schmidt H. Ca v2.2 Channels Sustain Vesicle Recruitment at a Mature Glutamatergic Synapse. J Neurosci 2023; 43:4005-4018. [PMID: 37185239 PMCID: PMC10255130 DOI: 10.1523/jneurosci.1279-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 04/06/2023] [Accepted: 04/08/2023] [Indexed: 05/17/2023] Open
Abstract
The composition of voltage-gated Ca2+ channel (Cav) subtypes that gate action potential (AP)-evoked release changes during the development of mammalian CNS synapses. Cav2.2 and Cav2.3 lose their function in gating-evoked release during postnatal synapse maturation. In mature boutons, Cav2.1 currents provide the almost exclusive trigger for evoked release, and Cav2.3 currents are required for the induction of presynaptic long-term potentiation. However, the functional significance of Cav2.2 remained elusive in mature boutons, although they remain present at active zones and continue contributing significantly to presynaptic Ca2+ influx. Here, we addressed the functional significance of Cav2.2 and Cav2.3 at mature parallel-fiber (PF) to Purkinje neuron synapses of mice of either sex. These synapses are known to exhibit the corresponding developmental Cav subtype changes in gating release. We addressed two hypotheses, namely that Cav2.2 and Cav2.3 are involved in triggering spontaneous glutamate release and that they are engaged in vesicle recruitment during repetitive evoked release. We found that spontaneous miniature release is Ca2+ dependent. However, experiments with Cav subtype-specific blockers excluded the spontaneous opening of Cavs as the Ca2+ source for spontaneous glutamate release. Thus, neither Cav2.2 nor Cav2.3 controls spontaneous release from PF boutons. Furthermore, vesicle recruitment during brief bursts of APs was also independent of Ca2+ influx through Cav2.2 and Cav2.3. However, Cav2.2, but not Cav2.3, currents significantly boosted vesicle recruitment during sustained high-frequency synaptic transmission. Thus, in mature PF boutons Cav2.2 channels are specifically required to sustain synaptic transmission during prolonged neuronal activity.SIGNIFICANCE STATEMENT At young CNS synapses, action potential-evoked release is gated via three subtypes of voltage-gated Ca2+ channels: Cav2.1, Cav2.2, and Cav2.3. During postnatal maturation, Cav2.2 and Cav2.3 lose their function in gating evoked release, such that at mature synapses Cav2.1 provides the almost exclusive source for triggering evoked release. Cav2.3 currents are required for the induction of presynaptic long-term potentiation. However, the function of the still abundant Cav2.2 in mature boutons remained largely elusive. Here, we studied mature cerebellar parallel-fiber synapses and found that Cav2.2 does not control spontaneous release. However, Ca2+ influx through Cav2.2 significantly boosted vesicle recruitment during trains of action potentials. Thus, Cav2.2 in mature parallel-fiber boutons participate in sustaining synaptic transmission during prolonged activity.
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Affiliation(s)
- Magdalena Wender
- Carl Ludwig Institute for Physiology, Medical Faculty, Leipzig University, 04103 Leipzig, Germany
| | - Grit Bornschein
- Carl Ludwig Institute for Physiology, Medical Faculty, Leipzig University, 04103 Leipzig, Germany
| | - Simone Brachtendorf
- Carl Ludwig Institute for Physiology, Medical Faculty, Leipzig University, 04103 Leipzig, Germany
| | - Stefan Hallermann
- Carl Ludwig Institute for Physiology, Medical Faculty, Leipzig University, 04103 Leipzig, Germany
| | - Jens Eilers
- Carl Ludwig Institute for Physiology, Medical Faculty, Leipzig University, 04103 Leipzig, Germany
| | - Hartmut Schmidt
- Carl Ludwig Institute for Physiology, Medical Faculty, Leipzig University, 04103 Leipzig, Germany
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3
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Ritzau-Jost A, Nerlich J, Kaas T, Krueger M, Tsintsadze T, Eilers J, Barbour B, Smith SM, Hallermann S. Direct whole-cell patch-clamp recordings from small boutons in rodent primary neocortical neuron cultures. STAR Protoc 2023; 4:102168. [PMID: 36920913 PMCID: PMC10026040 DOI: 10.1016/j.xpro.2023.102168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 12/08/2022] [Revised: 01/30/2023] [Accepted: 02/19/2023] [Indexed: 03/16/2023] Open
Abstract
Direct electrical recordings from conventional boutons in the mammalian central nervous system have proven challenging due to their small size. Here, we provide a protocol for direct whole-cell patch-clamp recordings from small presynaptic boutons of primary dissociated cultured neurons of the rodent neocortex. We describe steps to prepare primary neocortical cultures and recording pipettes, followed by identifying boutons and establishing a whole-cell bouton recording. We then provide details on precise pipette capacitance compensation required for high-resolution current-clamp recordings from boutons. For further details on the use and execution of this protocol, please refer to Ritzau-Jost et al.1.
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Affiliation(s)
- Andreas Ritzau-Jost
- Carl-Ludwig-Institute of Physiology, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany.
| | - Jana Nerlich
- Carl-Ludwig-Institute of Physiology, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany
| | - Thomas Kaas
- Carl-Ludwig-Institute of Physiology, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany
| | - Martin Krueger
- Institute of Anatomy, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany
| | - Timur Tsintsadze
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Oregon Health and Science University, Portland, OR 97239, USA; Section of Pulmonary and Critical Care Medicine, VA Portland Health Care System, Portland, OR 97239, USA
| | - Jens Eilers
- Carl-Ludwig-Institute of Physiology, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany
| | - Boris Barbour
- Institut de Biologie de l'ENS (IBENS), Département de Biologie, École Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | - Stephen M Smith
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Oregon Health and Science University, Portland, OR 97239, USA; Section of Pulmonary and Critical Care Medicine, VA Portland Health Care System, Portland, OR 97239, USA
| | - Stefan Hallermann
- Carl-Ludwig-Institute of Physiology, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany.
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4
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Schoknecht K, Hirrlinger J, Eilers J. Transient astrocytic accumulation of fluorescein during spreading depolarizations. Neurobiol Dis 2023; 178:106026. [PMID: 36731681 DOI: 10.1016/j.nbd.2023.106026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 08/23/2022] [Revised: 01/16/2023] [Accepted: 01/29/2023] [Indexed: 02/01/2023] Open
Abstract
Spreading depolarizations (SDs) occur frequently in acute cerebral injuries. They are characterized by a breakdown of transmembrane ion gradients resulting in a reduced extracellular sodium ([Na+]o) and increased extracellular potassium concentration ([K+]o). Elevated [K+]o induces astrocytic swelling, another feature of SD; however, the solutes that drive astrocytic swelling remain incompletely understood. We incidentally found astrocytic accumulation of fluorescein (Fluo) - a low molecular weight anionic dye - during SDs induced by elevated [K+]o. Herein, we aimed to explore the properties of astrocytic Fluo accumulation during SDs, electrical stimulation, [K+]o and glutamate elevation and elucidate underlying mechanisms and its relation to swelling. Experiments were performed in acute neocortical slices from adult male C57Bl6 mice and transgenic mice expressing tdTomato in parvalbumin (PV)-positive neurons. We labeled astrocytes with sulforhodamine-101 (SR-101), measured Fluo kinetics using 2-photon laser scanning microscopy and recorded local field potentials (LFP) to detect SDs. Elevations of [K+]o lead to an increase of the astrocytic Fluo intensity in parallel with astrocytic swelling. Pharmacological inhibitors of sodium‑potassium ATPase (Na/K-ATPase), secondary-active transporters and channels were used to address the underlying mechanisms. Fluo accumulation as well as swelling were only prevented by inhibition of the sodium‑potassium ATPase. Application of glutamate or hypoosmolar solution induced astrocytic swelling independent of Fluo accumulation and glutamate opposed Fluo accumulation when co-administered with high [K+]o. Astrocytes accumulated Fluo and swelled during electrical stimulation and even more during SDs. Taken together, Fluo imaging can be used as a tool to visualize yet unidentified anion fluxes during [K+]o- but not glutamate- or hypoosmolarity induced astrocytic swelling. Fluo imaging may thereby help to elucidate mechanisms of astrocytic swelling and associated fluid movements between brain compartments during physiological and pathological conditions, e.g. SDs.
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Affiliation(s)
- Karl Schoknecht
- Carl-Ludwig-Institute of Physiology, Medical Faculty, Leipzig University, Leipzig, Germany.
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute of Physiology, Medical Faculty, Leipzig University, Leipzig, Germany; Department of Neurogenetics, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Jens Eilers
- Carl-Ludwig-Institute of Physiology, Medical Faculty, Leipzig University, Leipzig, Germany
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5
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Köhler S, Winkler U, Junge T, Lippmann K, Eilers J, Hirrlinger J. Gray and white matter astrocytes differ in basal metabolism but respond similarly to neuronal activity. Glia 2023; 71:229-244. [PMID: 36063073 DOI: 10.1002/glia.24268] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [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: 04/07/2022] [Revised: 07/12/2022] [Accepted: 08/22/2022] [Indexed: 11/10/2022]
Abstract
Astrocytes are a heterogeneous population of glial cells in the brain, which adapt their properties to the requirements of the local environment. Two major groups of astrocytes are protoplasmic astrocytes residing in gray matter as well as fibrous astrocytes of white matter. Here, we compared the energy metabolism of astrocytes in the cortex and corpus callosum as representative gray matter and white matter regions, in acute brain slices taking advantage of genetically encoded fluorescent nanosensors for the NADH/NAD+ redox ratio and for ATP. Astrocytes of the corpus callosum presented a more reduced basal NADH/NAD+ redox ratio, and a lower cytosolic concentration of ATP compared to cortical astrocytes. In cortical astrocytes, the neurotransmitter glutamate and increased extracellular concentrations of K+ , typical correlates of neuronal activity, induced a more reduced NADH/NAD+ redox ratio. While application of glutamate decreased [ATP], K+ as well as the combination of glutamate and K+ resulted in an increase of ATP levels. Strikingly, a very similar regulation of metabolism by K+ and glutamate was observed in astrocytes in the corpus callosum. Finally, strong intrinsic neuronal activity provoked by application of bicuculline and withdrawal of Mg2+ caused a shift of the NADH/NAD+ redox ratio to a more reduced state as well as a slight reduction of [ATP] in gray and white matter astrocytes. In summary, the metabolism of astrocytes in cortex and corpus callosum shows distinct basal properties, but qualitatively similar responses to neuronal activity, probably reflecting the different environment and requirements of these brain regions.
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Affiliation(s)
- Susanne Köhler
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Ulrike Winkler
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Tabea Junge
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Kristina Lippmann
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Jens Eilers
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Johannes Hirrlinger
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany.,Department of Neurogenetics, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
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6
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Eshra A, Schmidt H, Eilers J, Hallermann S. Calcium dependence of neurotransmitter release at a high fidelity synapse. eLife 2021; 10:70408. [PMID: 34612812 PMCID: PMC8494478 DOI: 10.7554/elife.70408] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [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: 05/15/2021] [Accepted: 08/24/2021] [Indexed: 11/15/2022] Open
Abstract
The Ca2+-dependence of the priming, fusion, and replenishment of synaptic vesicles are fundamental parameters controlling neurotransmitter release and synaptic plasticity. Despite intense efforts, these important steps in the synaptic vesicles’ cycle remain poorly understood due to the technical challenge in disentangling vesicle priming, fusion, and replenishment. Here, we investigated the Ca2+-sensitivity of these steps at mossy fiber synapses in the rodent cerebellum, which are characterized by fast vesicle replenishment mediating high-frequency signaling. We found that the basal free Ca2+ concentration (<200 nM) critically controls action potential-evoked release, indicating a high-affinity Ca2+ sensor for vesicle priming. Ca2+ uncaging experiments revealed a surprisingly shallow and non-saturating relationship between release rate and intracellular Ca2+ concentration up to 50 μM. The rate of vesicle replenishment during sustained elevated intracellular Ca2+ concentration exhibited little Ca2+-dependence. Finally, quantitative mechanistic release schemes with five Ca2+ binding steps incorporating rapid vesicle replenishment via parallel or sequential vesicle pools could explain our data. We thus show that co-existing high- and low-affinity Ca2+ sensors mediate priming, fusion, and replenishment of synaptic vesicles at a high-fidelity synapse.
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Affiliation(s)
- Abdelmoneim Eshra
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Hartmut Schmidt
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Stefan Hallermann
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
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7
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Mrestani A, Pauli M, Kollmannsberger P, Repp F, Kittel RJ, Eilers J, Doose S, Sauer M, Sirén AL, Heckmann M, Paul MM. Active zone compaction correlates with presynaptic homeostatic potentiation. Cell Rep 2021; 37:109770. [PMID: 34610300 DOI: 10.1016/j.celrep.2021.109770] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [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: 11/03/2020] [Revised: 05/14/2021] [Accepted: 09/07/2021] [Indexed: 12/30/2022] Open
Abstract
Neurotransmitter release is stabilized by homeostatic plasticity. Presynaptic homeostatic potentiation (PHP) operates on timescales ranging from minute- to life-long adaptations and likely involves reorganization of presynaptic active zones (AZs). At Drosophila melanogaster neuromuscular junctions, earlier work ascribed AZ enlargement by incorporating more Bruchpilot (Brp) scaffold protein a role in PHP. We use localization microscopy (direct stochastic optical reconstruction microscopy [dSTORM]) and hierarchical density-based spatial clustering of applications with noise (HDBSCAN) to study AZ plasticity during PHP at the synaptic mesoscale. We find compaction of individual AZs in acute philanthotoxin-induced and chronic genetically induced PHP but unchanged copy numbers of AZ proteins. Compaction even occurs at the level of Brp subclusters, which move toward AZ centers, and in Rab3 interacting molecule (RIM)-binding protein (RBP) subclusters. Furthermore, correlative confocal and dSTORM imaging reveals how AZ compaction in PHP translates into apparent increases in AZ area and Brp protein content, as implied earlier.
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Affiliation(s)
- Achmed Mrestani
- Institute for Physiology, Department of Neurophysiology, Julius Maximilians University Würzburg, 97070 Würzburg, Germany; Department of Neurology, Leipzig University Medical Center, 04103 Leipzig, Germany
| | - Martin Pauli
- Institute for Physiology, Department of Neurophysiology, Julius Maximilians University Würzburg, 97070 Würzburg, Germany; Department of Neurosurgery, University Hospital of Würzburg, 97080 Würzburg, Germany
| | - Philip Kollmannsberger
- Center for Computational and Theoretical Biology, Julius Maximilians University Würzburg, 97074 Würzburg, Germany
| | - Felix Repp
- Institute for Physiology, Department of Neurophysiology, Julius Maximilians University Würzburg, 97070 Würzburg, Germany; Center for Computational and Theoretical Biology, Julius Maximilians University Würzburg, 97074 Würzburg, Germany; Department of Neurosurgery, University Hospital of Würzburg, 97080 Würzburg, Germany
| | - Robert J Kittel
- Institute for Physiology, Department of Neurophysiology, Julius Maximilians University Würzburg, 97070 Würzburg, Germany; Institute of Biology, Department of Animal Physiology, Leipzig University, 04103 Leipzig, Germany; Carl-Ludwig-Institute for Physiology, Leipzig University, 04103 Leipzig, Germany
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, Leipzig University, 04103 Leipzig, Germany
| | - Sören Doose
- Department of Biotechnology and Biophysics, Julius Maximilians University Würzburg, 97074 Würzburg, Germany
| | - Markus Sauer
- Department of Biotechnology and Biophysics, Julius Maximilians University Würzburg, 97074 Würzburg, Germany
| | - Anna-Leena Sirén
- Institute for Physiology, Department of Neurophysiology, Julius Maximilians University Würzburg, 97070 Würzburg, Germany; Department of Neurosurgery, University Hospital of Würzburg, 97080 Würzburg, Germany
| | - Manfred Heckmann
- Institute for Physiology, Department of Neurophysiology, Julius Maximilians University Würzburg, 97070 Würzburg, Germany.
| | - Mila M Paul
- Institute for Physiology, Department of Neurophysiology, Julius Maximilians University Würzburg, 97070 Würzburg, Germany; Department of Orthopaedic Trauma, Hand, Plastic and Reconstructive Surgery, University Hospital of Würzburg, 97080 Würzburg, Germany.
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8
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Braune J, Lindhorst A, Fröba J, Hobusch C, Kovacs P, Blüher M, Eilers J, Bechmann I, Gericke M. Multinucleated Giant Cells in Adipose Tissue Are Specialized in Adipocyte Degradation. Diabetes 2021; 70:538-548. [PMID: 33158932 DOI: 10.2337/db20-0293] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 10/30/2020] [Indexed: 11/13/2022]
Abstract
Obesity is associated with chronic low-grade inflammation of visceral adipose tissue (AT) characterized by an increasing number of AT macrophages (ATMs) and linked to type 2 diabetes. AT inflammation is histologically indicated by the formation of so-called crown-like structures, as ATMs accumulate around dying adipocytes, and the occurrence of multinucleated giant cells (MGCs). However, to date, the function of MGCs in obesity is unknown. Therefore, the aim of this study was to characterize MGCs in AT and unravel the function of these cells. We demonstrated that MGCs occurred in obese patients and after 24 weeks of a high-fat diet in mice, accompanying signs of AT inflammation and then representing ∼3% of ATMs in mice. Mechanistically, we found evidence that adipocyte death triggered MGC formation. Most importantly, MGCs in obese AT had a higher capacity to phagocytize oversized particles, such as adipocytes, as shown by live imaging of AT, 45-µm bead uptake ex vivo, and higher lipid content in vivo. Finally, we showed that interleukin-4 treatment was sufficient to increase the number of MGCs in AT, whereas other factors may be more important for endogenous MGC formation in vivo. Most importantly, our data suggest that MGCs are specialized for clearance of dead adipocytes in obesity.
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Affiliation(s)
- Julia Braune
- Institute of Anatomy and Cell Biology, Martin-Luther-University Halle-Wittenberg, Halle, Germany
| | - Andreas Lindhorst
- Institute of Anatomy and Cell Biology, Martin-Luther-University Halle-Wittenberg, Halle, Germany
- Institute of Anatomy, Leipzig University, Leipzig, Germany
| | - Janine Fröba
- Institute of Anatomy and Cell Biology, Martin-Luther-University Halle-Wittenberg, Halle, Germany
- Institute of Anatomy, Leipzig University, Leipzig, Germany
| | | | - Peter Kovacs
- Medical Department III, Leipzig University, Leipzig, Germany
| | - Matthias Blüher
- Medical Department III, Leipzig University, Leipzig, Germany
| | - Jens Eilers
- Carl-Ludwig Institute of Physiology, Leipzig University, Leipzig, Germany
| | - Ingo Bechmann
- Institute of Anatomy, Leipzig University, Leipzig, Germany
| | - Martin Gericke
- Institute of Anatomy and Cell Biology, Martin-Luther-University Halle-Wittenberg, Halle, Germany
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9
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Ritzau-Jost A, Tsintsadze T, Krueger M, Ader J, Bechmann I, Eilers J, Barbour B, Smith SM, Hallermann S. Large, Stable Spikes Exhibit Differential Broadening in Excitatory and Inhibitory Neocortical Boutons. Cell Rep 2021; 34:108612. [PMID: 33440142 PMCID: PMC7809622 DOI: 10.1016/j.celrep.2020.108612] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 10/19/2020] [Accepted: 12/06/2020] [Indexed: 01/09/2023] Open
Abstract
Presynaptic action potential spikes control neurotransmitter release and thus interneuronal communication. However, the properties and the dynamics of presynaptic spikes in the neocortex remain enigmatic because boutons in the neocortex are small and direct patch-clamp recordings have not been performed. Here, we report direct recordings from boutons of neocortical pyramidal neurons and interneurons. Our data reveal rapid and large presynaptic action potentials in layer 5 neurons and fast-spiking interneurons reliably propagating into axon collaterals. For in-depth analyses, we establish boutons of mature cultured neurons as models for excitatory neocortical boutons, demonstrating that the presynaptic spike amplitude is unaffected by potassium channels, homeostatic long-term plasticity, and high-frequency firing. In contrast to the stable amplitude, presynaptic spikes profoundly broaden during high-frequency firing in layer 5 pyramidal neurons, but not in fast-spiking interneurons. Thus, our data demonstrate large presynaptic spikes and fundamental differences between excitatory and inhibitory boutons in the neocortex.
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Affiliation(s)
- Andreas Ritzau-Jost
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany
| | - Timur Tsintsadze
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Oregon Health and Science University, Portland, OR 97239, USA; Section of Pulmonary and Critical Care Medicine, VA Portland Health Care System, Portland, OR 97239, USA
| | - Martin Krueger
- Institute of Anatomy, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany
| | - Jonas Ader
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany
| | - Ingo Bechmann
- Institute of Anatomy, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany
| | - Boris Barbour
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, PSL Université Paris, 75005 Paris, France
| | - Stephen M Smith
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Oregon Health and Science University, Portland, OR 97239, USA; Section of Pulmonary and Critical Care Medicine, VA Portland Health Care System, Portland, OR 97239, USA.
| | - Stefan Hallermann
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, Leipzig University, 04103 Leipzig, Germany.
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10
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Bornschein G, Eilers J, Schmidt H. Neocortical High Probability Release Sites Are Formed by Distinct Ca 2+ Channel-to-Release Sensor Topographies during Development. Cell Rep 2020; 28:1410-1418.e4. [PMID: 31390556 DOI: 10.1016/j.celrep.2019.07.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [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: 02/11/2019] [Revised: 05/29/2019] [Accepted: 06/28/2019] [Indexed: 01/10/2023] Open
Abstract
Coupling distances between Ca2+ channels and release sensors regulate vesicular release probability (pv). Tight coupling is thought to provide a framework for high pv and loose coupling for high plasticity at low pv. At synapses investigated during development, coupling distances decrease, thereby increasing pv and transmission fidelity. We find that neocortical high-fidelity synapses deviate from these rules. Paired recordings from pyramidal neurons with "slow" and "fast" Ca2+ chelators combined with experimentally constrained simulations suggest that coupling tightens significantly during development. However, fluctuation analysis revealed that neither pv (∼0.63) nor the number of release sites (∼8) changes concomitantly. Moreover, the amplitude and time course of presynaptic Ca2+ transients are not different between age groups. These results are explained by high-pv release sites with Ca2+ microdomains in young synapses and nanodomains in mature synapses. Thus, at neocortical synapses, a developmental reorganization of the active zone leaves pv unaffected, emphasizing developmental and functional synaptic diversity.
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Affiliation(s)
- Grit Bornschein
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27a, 04103 Leipzig, Germany.
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27a, 04103 Leipzig, Germany
| | - Hartmut Schmidt
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27a, 04103 Leipzig, Germany.
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Kaiser N, Pätz C, Brachtendorf S, Eilers J, Bechmann I. Undisturbed climbing fiber pruning in the cerebellar cortex of CX 3 CR1-deficient mice. Glia 2020; 68:2316-2329. [PMID: 32488990 DOI: 10.1002/glia.23842] [Citation(s) in RCA: 3] [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: 12/14/2018] [Revised: 04/21/2020] [Accepted: 04/28/2020] [Indexed: 11/11/2022]
Abstract
Pruning, the elimination of excess synapses is a phenomenon of fundamental importance for correct wiring of the central nervous system. The establishment of the cerebellar climbing fiber (CF)-to-Purkinje cell (PC) synapse provides a suitable model to study pruning and pruning-relevant processes during early postnatal development. Until now, the role of microglia in pruning remains under intense investigation. Here, we analyzed migration of microglia into the cerebellar cortex during early postnatal development and their possible contribution to the elimination of CF-to-PC synapses. Microglia enrich in the PC layer at pruning-relevant time points giving rise to the possibility that microglia are actively involved in synaptic pruning. We investigated the contribution of microglial fractalkine (CX3 CR1) signaling during postnatal development using genetic ablation of the CX3 CR1 receptor and an in-depth histological analysis of the cerebellar cortex. We found an aberrant migration of microglia into the granule and the molecular layer. By electrophysiological analysis, we show that defective fractalkine signaling and the associated migration deficits neither affect the pruning of excess CFs nor the development of functional parallel fiber and inhibitory synapses with PCs. These findings indicate that CX3 CR1 signaling is not mandatory for correct cerebellar circuit formation. MAIN POINTS: Ablation of CX3 CR1 results in a transient migration defect in cerebellar microglia. CX3 CR1 is not required for functional pruning of cerebellar climbing fibers. Functional inhibitory and parallel fiber synapse development with Purkinje cells is undisturbed in CX3 CR1-deficient mice.
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Affiliation(s)
- Nicole Kaiser
- Institute for Anatomy, University of Leipzig, Leipzig, Germany
| | - Christina Pätz
- Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Simone Brachtendorf
- Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Ingo Bechmann
- Institute for Anatomy, University of Leipzig, Leipzig, Germany
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12
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Wagner W, Lippmann K, Heisler FF, Gromova KV, Lombino FL, Roesler MK, Pechmann Y, Hornig S, Schweizer M, Polo S, Schwarz JR, Eilers J, Kneussel M. Myosin VI Drives Clathrin-Mediated AMPA Receptor Endocytosis to Facilitate Cerebellar Long-Term Depression. Cell Rep 2019; 28:11-20.e9. [DOI: 10.1016/j.celrep.2019.06.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 05/01/2019] [Accepted: 05/31/2019] [Indexed: 11/30/2022] Open
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Kusch V, Bornschein G, Loreth D, Bank J, Jordan J, Baur D, Watanabe M, Kulik A, Heckmann M, Eilers J, Schmidt H. Munc13-3 Is Required for the Developmental Localization of Ca 2+ Channels to Active Zones and the Nanopositioning of Ca v2.1 Near Release Sensors. Cell Rep 2019; 22:1965-1973. [PMID: 29466725 DOI: 10.1016/j.celrep.2018.02.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 12/01/2017] [Accepted: 01/31/2018] [Indexed: 12/20/2022] Open
Abstract
Spatial relationships between Cav channels and release sensors at active zones (AZs) are a major determinant of synaptic fidelity. They are regulated developmentally, but the underlying molecular mechanisms are largely unclear. Here, we show that Munc13-3 regulates the density of Cav2.1 and Cav2.2 channels, alters the localization of Cav2.1, and is required for the development of tight, nanodomain coupling at parallel-fiber AZs. We combined EGTA application and Ca2+-channel pharmacology in electrophysiological and two-photon Ca2+ imaging experiments with quantitative freeze-fracture immunoelectron microscopy and mathematical modeling. We found that a normally occurring developmental shift from release being dominated by Ca2+ influx through Cav2.1 and Cav2.2 channels with domain overlap and loose coupling (microdomains) to a nanodomain Cav2.1 to sensor coupling is impaired in Munc13-3-deficient synapses. Thus, at AZs lacking Munc13-3, release remained triggered by Cav2.1 and Cav2.2 microdomains, suggesting a critical role of Munc13-3 in the formation of release sites with calcium channel nanodomains.
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Affiliation(s)
- Valentin Kusch
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany
| | - Grit Bornschein
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany
| | - Desiree Loreth
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Julia Bank
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Johannes Jordan
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - David Baur
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany
| | - Masahiko Watanabe
- Department of Anatomy, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
| | - Akos Kulik
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Manfred Heckmann
- Department of Physiology, Neurophysiology, Medical Faculty, University of Würzburg, Röntgenring 9, 97070 Würzburg, Germany
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany
| | - Hartmut Schmidt
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany.
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Pätz C, Brachtendorf S, Eilers J. Developmental Easing of Short-Term Depression in "Winner" Climbing Fibers. Front Cell Neurosci 2019; 13:183. [PMID: 31118890 PMCID: PMC6504704 DOI: 10.3389/fncel.2019.00183] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 01/18/2019] [Accepted: 04/12/2019] [Indexed: 11/13/2022] Open
Abstract
The postnatal development of cerebellar climbing fiber (CF) to Purkinje neuron (PN) synapses is characterized by a substantial pruning during the first 3 weeks after birth, switching from multiple- to single-CF innervation. Previous studies suggested that CF maturation is governed by bidirectional changes of synaptic plasticity. The strengthening of surviving "winner" CFs, which translocate from the PN soma to the dendrite, is thought to be guided by long-term potentiation (LTP), while weakening of to-be-eliminated "loser" CFs, which remain on the soma, was proposed to be due to long-term depression (LTD). However, there are conflicting results from previous studies, whether or not strengthening of winner and weakening of loser CFs during postnatal development is accompanied by changes in short-term plasticity and, thus, whether pre- or postsynaptic forms of LTD and LTP are operational. We, therefore, analyzed the developmental profile of paired-pulse depression (PPD) in "weak" and "strong" CFs in 3-21-day old Igsf9-eGFP mice, which allow visual identification of GFP-labeled CFs. We found that in 3-8-day old mice strong CFs are marked by a stronger PPD compared to weak CFs. Surprisingly, PPD of strong CFs eases during maturation, while PPD in weak CFs remains unchanged. This easing of PPD is neither due to changes in presynaptic influx-release coupling nor to an increased saturation of postsynaptic receptors. Thus, our results imply that synaptic contacts of CFs show distinct features of PPD depending on their affiliation to winner or loser CFs and depending on their somatic or dendritic location.
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Affiliation(s)
- Christina Pätz
- Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Simone Brachtendorf
- Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
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15
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Naumann G, Lippmann K, Eilers J. Photophysical properties of Na + -indicator dyes suitable for quantitative two-photon fluorescence-lifetime measurements. J Microsc 2018; 272:136-144. [PMID: 30191999 DOI: 10.1111/jmi.12754] [Citation(s) in RCA: 5] [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: 07/05/2018] [Revised: 08/14/2018] [Accepted: 08/14/2018] [Indexed: 12/29/2022]
Abstract
Two-photon microscopy (2PM) offers great potential in fluorescence imaging of intracellular Na+ dynamics of live cells. A severe drawback, however, is that quantitative ratioing of fluorescence intensities at different wavelengths [possible in one-photon imaging with the classical Na+ -indicator dye sodium-binding benzofuran isophtalate (SBFI)] is not practical in 2PM. We aimed at establishing 2PM-based time-correlated fluorescence lifetime measurements as an alternative method for quantifying Na+ dynamics. We compared the photophysical properties of the four Na+ -sensitive fluorescent indicator dyes SBFI, CoroNa Green, Sodium Green and Asante NaTRIUM Green-2 (ANG-2) in cuvette calibrations. All four dyes showed Na+ -dependent intensity changes, with ANG-2 having the most favourable properties for 2PM. All dyes but SBFI showed significant changes in their fluorescence lifetime upon Na+ binding, again with ANG-2 being the most promising dye. We found that, unfortunately, the fluorescence lifetime of ANG-2 is not only affected by Na+ but also by protons, K+ and dye impurities, rendering a quantitative description of the individual lifetime components impractical. However, a simplified calibration procedure, based on a published approach for Ca2+ imaging, allowed relating lifetimes to Na+ concentration. Using ANG-2 and the simplified calibration will allow quantitative two-photon Na+ imaging with millimolar sensitivity. LAY DESCRIPTION Dynamic changes of ion concentrations, which play crucial roles in cellular physiology, can be monitored with appropriate fluorescent indicator dyes. For intracellular sodium ions (Na+ ), certain dyes even allow quantitative measurements with standard microscopic techniques. However, for two-photon microscopy, which allows resolving cells deep in intact tissue, imaging solutions that are fully quantitative are lacking. For the four commercially available Na+ dyes 'SBFI', 'CoroNa Green', 'Sodium Green', and 'Asante NaTRIUM Green-2' (ANG2) we analyzed whether their fluorescent lifetime (LT), i.e., the nanosecond decay of emission of photons after a pulsed excitation, could serve as a quantitative measure of intracellular Na+ . Pulsed excitation in the femtosecond range is an inherent feature of two-photon microscopy and, in combination with fast, single-photon counting microscopes, allows for easy-to-implement LT microscopy. We found that Sodium Green and ANG2 showed strong Na+ -dependent changes in the fluorescence LT, while SBFI showed no, and CoroNa Green only small changes. ANG2, as the brightest dye, was further characterized regarding effects of protons and potassium ions (K+ ), both also present in cells at significant concentrations, on the fluorescence LT. We found that the LT of ANG2 is affected in a predictable manner by Na+ , K+ , and protons. However, our data reveal that the commercial dye must also contain impurities with unexpected Na+ - and K+ -binding characteristics, rendering a quantitative description of the individual lifetime components impractical. We, therefore, adapted a simplified calibration procedure, based on a published approach for Ca2+ imaging, that allows relating the average lifetime to Na+ concentration. With this simplified calibration procedure, ANG2 is well suited for quantitative two-photon Na+ imaging with millimolar sensitivity.
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Affiliation(s)
- G Naumann
- Carl-Ludwig-Institute for Physiology, University Leipzig, Liebigstr. 27, Leipzig, Germany
| | - K Lippmann
- Carl-Ludwig-Institute for Physiology, University Leipzig, Liebigstr. 27, Leipzig, Germany
| | - J Eilers
- Carl-Ludwig-Institute for Physiology, University Leipzig, Liebigstr. 27, Leipzig, Germany
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16
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Ritzau-Jost A, Jablonski L, Viotti J, Lipstein N, Eilers J, Hallermann S. Apparent calcium dependence of vesicle recruitment. J Physiol 2018; 596:4693-4707. [PMID: 29928766 DOI: 10.1113/jp275911] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [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: 01/26/2018] [Accepted: 06/11/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Synaptic transmission relies on the recruitment of neurotransmitter-filled vesicles to presynaptic release sites. Increased intracellular calcium buffering slows the recovery from synaptic depression, suggesting that vesicle recruitment is a calcium-dependent process. However, the molecular mechanisms of vesicle recruitment have only been investigated at some synapses. We investigate the role of calcium in vesicle recruitment at the cerebellar mossy fibre to granule cell synapse. We find that increased intracellular calcium buffering slows the recovery from depression following physiological stimulation. However, the recovery is largely resistant to perturbation of the molecular pathways previously shown to mediate calcium-dependent vesicle recruitment. Furthermore, we find two pools of vesicles with different recruitment speeds and show that models incorporating two pools of vesicles with different calcium-independent recruitment rates can explain our data. In this framework, increased calcium buffering prevents the release of intrinsically fast-recruited vesicles but does not change the vesicle recruitment rates themselves. ABSTRACT During sustained synaptic transmission, recruitment of new transmitter-filled vesicles to the release site counteracts vesicle depletion and thus synaptic depression. An elevated intracellular Ca2+ concentration has been proposed to accelerate the rate of vesicle recruitment at many synapses. This conclusion is often based on the finding that increased intracellular Ca2+ buffering slows the recovery from synaptic depression. However, the molecular mechanisms of the activity-dependent acceleration of vesicle recruitment have only been analysed at some synapses. Using physiological stimulation patterns in postsynaptic recordings and step depolarizations in presynaptic bouton recordings, we investigate vesicle recruitment at cerebellar mossy fibre boutons. We show that increased intracellular Ca2+ buffering slows recovery from depression dramatically. However, pharmacological and genetic interference with calmodulin or the calmodulin-Munc13 pathway, which has been proposed to mediate Ca2+ -dependence of vesicle recruitment, barely affects vesicle recovery from depression. Furthermore, we show that cerebellar mossy fibre boutons have two pools of vesicles: rapidly fusing vesicles that recover slowly and slowly fusing vesicles that recover rapidly. Finally, models adopting such two pools of vesicles with Ca2+ -independent recruitment rates can explain the slowed recovery from depression upon increased Ca2+ buffering. Our data do not rule out the involvement of the calmodulin-Munc13 pathway during stronger stimuli or other molecular pathways mediating Ca2+ -dependent vesicle recruitment at cerebellar mossy fibre boutons. However, we show that well-established two-pool models predict an apparent Ca2+ -dependence of vesicle recruitment. Thus, previous conclusions of Ca2+ -dependent vesicle recruitment based solely on increased intracellular Ca2+ buffering should be considered with caution.
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Affiliation(s)
- Andreas Ritzau-Jost
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, Leipzig University, Leipzig, Germany
| | - Lukasz Jablonski
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, Leipzig University, Leipzig, Germany
| | - Julio Viotti
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, Leipzig University, Leipzig, Germany.,Department of Anatomy and Embryology, Center of Anatomy, University Medical Center Göttingen, Göttingen, Germany
| | - Noa Lipstein
- Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, Leipzig University, Leipzig, Germany
| | - Stefan Hallermann
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, Leipzig University, Leipzig, Germany
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17
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Orthgiess J, Gericke M, Immig K, Schulz A, Hirrlinger J, Bechmann I, Eilers J. Neurons exhibit Lyz2 promoter activity in vivo: Implications for using LysM-Cre mice in myeloid cell research. Eur J Immunol 2016; 46:1529-32. [PMID: 27062494 DOI: 10.1002/eji.201546108] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [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: 10/06/2015] [Revised: 02/23/2016] [Accepted: 04/01/2016] [Indexed: 12/13/2022]
Abstract
To characterize LysM-Cre mediated gene targeting in mice, we crossed LysM-Cre mice to two independent reporter-mouse lines (tdTomato or YFP). Surprisingly, we found that more than 90% of cells with LysM-Cre mediated recombination in the brain were neurons, rather than myeloid cells, such as microglia. Hence, by using the LysM-Cre mouse line for conditional knockout approaches, a significant neuronal recombination needs to be considered.
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Affiliation(s)
- Johannes Orthgiess
- Carl-Ludwig Institute of Physiology, Leipzig University, Leipzig, Germany
| | - Martin Gericke
- Institute of Anatomy, Leipzig University, Leipzig, Germany
| | - Kerstin Immig
- Institute of Anatomy, Leipzig University, Leipzig, Germany
| | - Angela Schulz
- Institute of Biochemistry, Leipzig University, Leipzig, Germany
| | | | - Ingo Bechmann
- Institute of Anatomy, Leipzig University, Leipzig, Germany
| | - Jens Eilers
- Carl-Ludwig Institute of Physiology, Leipzig University, Leipzig, Germany
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18
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Gericke M, Weyer U, Braune J, Bechmann I, Eilers J. A method for long-term live imaging of tissue macrophages in adipose tissue explants. Am J Physiol Endocrinol Metab 2015; 308:E1023-33. [PMID: 25874903 DOI: 10.1152/ajpendo.00075.2015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 04/14/2015] [Indexed: 11/22/2022]
Abstract
Obesity is frequently associated with a chronic low-grade inflammation within adipose tissue (AT). Although classical signs of inflammation are missing in AT inflammation, there is a significant increase in macrophages and, to a lesser extent, other immune cells, such as T cells, B cells, mast cells, and neutrophils. The spatial and temporal activation of these cells as well as their accumulation in the AT seem to be tightly linked to so-called crown-like structures (CLS). CLS are accumulations of adipose tissue macrophages (ATMs) around dead adipocytes and are thought to reflect a scavenger response. At present, data on the life cycle of CLS are missing. To better understand the cellular events underlying AT inflammation, we developed an approach that allows long-term imaging of ATMs, adipocytes, and CLS within live AT explants. We tested three putative reporter mouse lines for myeloid cells in regard to their suitability for live imaging. Thereby, we identified ATMs from CSF1R-eGFP mice to exhibit the most robust expression of eGFP. AT explants from these mice allowed stable live imaging for more than 7 days without significant phototoxicity. Long-term imaging thus revealed the accumulation of ATMs around dying adipocytes, migration of ATMs within AT, and also the degradation of the lipid remnants of perishing adipocytes. The observed behavior of ATMs in the context of AT inflammation is in line with previous studies but for the first time provides data on the specific behavior of individual ATMs and on the life cycle of CLS with unprecedented spatiotemporal resolution.
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Affiliation(s)
- Martin Gericke
- Institute of Anatomy, Leipzig University, Leipzig, Germany; and
| | - Ulrike Weyer
- Institute of Anatomy, Leipzig University, Leipzig, Germany; and
| | - Julia Braune
- Institute of Anatomy, Leipzig University, Leipzig, Germany; and
| | - Ingo Bechmann
- Institute of Anatomy, Leipzig University, Leipzig, Germany; and
| | - Jens Eilers
- Carl-Ludwig Institute of Physiology, Leipzig University, Leipzig, Germany
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Brachtendorf S, Eilers J, Schmidt H. A use-dependent increase in release sites drives facilitation at calretinin-deficient cerebellar parallel-fiber synapses. Front Cell Neurosci 2015; 9:27. [PMID: 25691858 PMCID: PMC4315043 DOI: 10.3389/fncel.2015.00027] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [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: 12/02/2014] [Accepted: 01/15/2015] [Indexed: 12/13/2022] Open
Abstract
Endogenous Ca(2+)-binding proteins affect synaptic transmitter release and short-term plasticity (STP) by buffering presynaptic Ca(2+) signals. At parallel-fiber (PF)-to-Purkinje neuron (PN) synapses in the cerebellar cortex loss of calretinin (CR), the major buffer at PF terminals, results in increased presynaptic Ca(2+) transients and an almost doubling of the initial vesicular releases probability (p r). Surprisingly, however, it has been reported that loss of CR from PF synapses does not alter paired-pulse facilitation (PPF), while it affects presynaptic Ca(2+) signals as well as p r. Here, we addressed this puzzling observation by analyzing the frequency- and Ca(2+)-dependence of PPF at unitary PF-to-PN synapses of wild-type (WT) and CR-deficient (CR(-/-)) mice using paired recordings and computer simulations. Our analysis revealed that PPF in CR(-/-) is indeed smaller than in the WT, to a degree, however, that indicates that rapid vesicle replenishment and recruitment of additional release sites dominate the synaptic efficacy of the second response. These Ca(2+)-driven processes operate more effectively in the absence of CR, thereby, explaining the preservation of robust PPF in the mutants.
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Affiliation(s)
- Simone Brachtendorf
- Medical Faculty, Carl-Ludwig-Institute for Physiology, University of Leipzig Leipzig, Germany
| | - Jens Eilers
- Medical Faculty, Carl-Ludwig-Institute for Physiology, University of Leipzig Leipzig, Germany
| | - Hartmut Schmidt
- Medical Faculty, Carl-Ludwig-Institute for Physiology, University of Leipzig Leipzig, Germany
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20
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Michaelis M, Nieswandt B, Stegner D, Eilers J, Kraft R. STIM1, STIM2, and Orai1 regulate store-operated calcium entry and purinergic activation of microglia. Glia 2014; 63:652-63. [PMID: 25471906 DOI: 10.1002/glia.22775] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 11/14/2014] [Indexed: 11/09/2022]
Abstract
Activation of microglia is the first and main immune response to brain injury. Release of the nucleotides ATP, ADP, and UDP from damaged cells regulate microglial migration and phagocytosis via purinergic P2Y receptors. We hypothesized that store-operated Ca(2+) entry (SOCE), the prevalent Ca(2+) influx mechanism in non-excitable cells, is a potent mediator of microglial responses to extracellular nucleotides. Expression analyses of STIM Ca(2+) sensors and Orai Ca(2+) channel subunits, that comprise the molecular machinery of SOCE, showed relevant levels of STIM1, STIM2, and Orai1 in cultured mouse microglia. STIM1 expression and SOCE were down-regulated by treatment of microglia with lipopolysaccharide, suggesting that inflammation limits SOCE by lower STIM1 abundance. Ca(2+) entry induced by cyclopiazonic acid, ATP, the P2Y6 receptor agonist UDP, or the P2Y12 receptor agonist 2-methylthio-ADP (2-MeSADP) was clearly affected in microglia from Stim1(-/-) , Stim2(-/-) , and Orai1(-/-) mice. SOCE blockers or ablation of STIM1, STIM2, or Orai1 severely impaired nucleotide-induced migration and phagocytosis in microglia. Thus, this study assigns SOCE, regulated by STIM1, STIM2, and Orai1 an essential role in purinergic signaling and activation of microglia.
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Affiliation(s)
- Marlen Michaelis
- Carl-Ludwig-Institute for Physiology, University of Leipzig, 04103, Leipzig, Germany
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21
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Mortensen LS, Schmidt H, Farsi Z, Barrantes-Freer A, Rubio ME, Ufartes R, Eilers J, Sakaba T, Stühmer W, Pardo LA. KV 10.1 opposes activity-dependent increase in Ca²⁺ influx into the presynaptic terminal of the parallel fibre-Purkinje cell synapse. J Physiol 2014; 593:181-96. [PMID: 25556795 DOI: 10.1113/jphysiol.2014.281600] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 10/13/2014] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS Voltage-gated KV 10.1 potassium channels are widely expressed in the mammalian brain but their function remains poorly understood. We report that KV 10.1 is enriched in the presynaptic terminals and does not take part in somatic action potentials. In parallel fibre synapses in the cerebellar cortex, we find that KV 10.1 regulates Ca(2+) influx and neurotransmitter release during repetitive high-frequency activity. Our results describe the physiological role of mammalian KV 10.1 for the first time and help understand the fine-tuning of synaptic transmission. The voltage-gated potassium channel KV 10.1 (Eag1) is widely expressed in the mammalian brain, but its physiological function is not yet understood. Previous studies revealed highest expression levels in hippocampus and cerebellum and suggested a synaptic localization of the channel. The distinct activation kinetics of KV 10.1 indicate a role during repetitive activity of the cell. Here, we confirm the synaptic localization of KV 10.1 both biochemically and functionally and that the channel is sufficiently fast at physiological temperature to take part in repolarization of the action potential (AP). We studied the role of the channel in cerebellar physiology using patch clamp and two-photon Ca(2+) imaging in KV 10.1-deficient and wild-type mice. The excitability and action potential waveform recorded at granule cell somata was unchanged, while Ca(2+) influx into axonal boutons was enhanced in mutants in response to stimulation with three APs, but not after a single AP. Furthermore, mutants exhibited a frequency-dependent increase in facilitation at the parallel fibre-Purkinje cell synapse at high firing rates. We propose that KV 10.1 acts as a modulator of local AP shape specifically during high-frequency burst firing when other potassium channels suffer cumulative inactivation.
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Affiliation(s)
- Lena Sünke Mortensen
- Max-Planck-Institute of Experimental Medicine, 37075, Göttingen, Germany; International Max Planck Research School Neurosciences, 37077, Göttingen, Germany
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Haase J, Weyer U, Immig K, Klöting N, Blüher M, Eilers J, Bechmann I, Gericke M. Local proliferation of macrophages in adipose tissue during obesity-induced inflammation. Diabetologia 2014; 57:562-71. [PMID: 24343232 DOI: 10.1007/s00125-013-3139-y] [Citation(s) in RCA: 171] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 11/19/2013] [Indexed: 12/18/2022]
Abstract
AIMS/HYPOTHESIS Obesity is frequently associated with low-grade inflammation of adipose tissue (AT), and the increase in adipose tissue macrophages (ATMs) is linked to an increased risk of type 2 diabetes. Macrophages have been regarded as post-mitotic, but recent observations have challenged this view. In this study, we tested the hypothesis that macrophages proliferate within AT in diet-induced obesity in mice and humans. METHODS We studied the expression of proliferation markers by immunofluorescence, PCR and flow cytometry in three different models of mouse obesity as well as in humans (n = 239). The cell fate of dividing macrophages was assessed by live imaging of AT explants. RESULTS We show that ATMs undergo mitosis within AT, predominantly within crown-like structures (CLS). We found a time-dependent increase in ATM proliferation when mice were fed a high-fat diet. Upregulation of CD206 and CD301 in proliferating ATMs indicated preferential M2 polarisation. Live imaging within AT explants from mice revealed that macrophages emigrate out of the CLS to become resident in the interstitium. In humans, we confirmed the increased expression of proliferation markers of CD68(+) macrophages in CLS and demonstrated a higher mRNA expression of the proliferation marker Ki67 in AT from obese patients. CONCLUSIONS/INTERPRETATION Local proliferation contributes to the increase in M2 macrophages in AT. Our data confirm CLS as the primary site of proliferation and a new source of ATMs and support a model of different recruitment mechanisms for classically activated (M1) and alternatively activated (M2) macrophages in obesity.
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Affiliation(s)
- Julia Haase
- Institute of Anatomy, Leipzig University, Liebigstraße 13, 04103, Leipzig, Germany
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Arendt O, Schwaller B, Brown EB, Eilers J, Schmidt H. Restricted diffusion of calretinin in cerebellar granule cell dendrites implies Ca²⁺-dependent interactions via its EF-hand 5 domain. J Physiol 2013; 591:3887-99. [PMID: 23732647 DOI: 10.1113/jphysiol.2013.256628] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Ca²⁺-binding proteins (CaBPs) are important regulators of neuronal Ca²⁺ signalling, acting either as buffers that shape Ca²⁺ transients and Ca²⁺ diffusion and/or as Ca²⁺ sensors. The diffusional mobility represents a crucial functional parameter of CaBPs, describing their range-of-action and possible interactions with binding partners. Calretinin (CR) is a CaBP widely expressed in the nervous system with strong expression in cerebellar granule cells. It is involved in regulating excitability and synaptic transmission of granule cells, and its absence leads to impaired motor control. We quantified the diffusional mobility of dye-labelled CR in mouse granule cells using two-photon fluorescence recovery after photobleaching. We found that movement of macromolecules in granule cell dendrites was not well described by free Brownian diffusion and that CR diffused unexpectedly slow compared to fluorescein dextrans of comparable size. During bursts of action potentials, which were associated with dendritic Ca²⁺ transients, the mobility of CR was further reduced. Diffusion was significantly accelerated by a peptide embracing EF-hand 5 of CR. Our results suggest long-lasting, Ca²⁺-dependent interactions of CR with large and/or immobile binding partners. These interactions render CR a poorly mobile Ca²⁺ buffer and point towards a Ca²⁺ sensor function of CR.
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Affiliation(s)
- Oliver Arendt
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University Leipzig, Germany
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Bornschein G, Arendt O, Hallermann S, Brachtendorf S, Eilers J, Schmidt H. Paired-pulse facilitation at recurrent Purkinje neuron synapses is independent of calbindin and parvalbumin during high-frequency activation. J Physiol 2013; 591:3355-70. [PMID: 23671160 DOI: 10.1113/jphysiol.2013.254128] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Paired-pulse facilitation (PPF) is a dynamic enhancement of transmitter release considered crucial in CNS information processing. The mechanisms of PPF remain controversial and may differ between synapses. Endogenous Ca(2+) buffers such as parvalbumin (PV) and calbindin-D28k (CB) are regarded as important modulators of PPF, with PV acting as an anti-facilitating buffer while saturation of CB can promote PPF. We analysed transmitter release and PPF at intracortical, recurrent Purkinje neuron (PN) to PN synapses, which show PPF during high-frequency activation (200 Hz) and strongly express both PV and CB. We quantified presynaptic Ca(2+) dynamics and quantal release parameters in wild-type (WT), and CB and PV deficient mice. Lack of CB resulted in increased volume averaged presynaptic Ca(2+) amplitudes and in increased release probability, while loss of PV had no significant effect on these parameters. Unexpectedly, none of the buffers significantly influenced PPF, indicating that neither CB saturation nor residual free Ca(2+) ([Ca(2+)]res) was the main determinant of PPF. Experimentally constrained, numerical simulations of Ca(2+)-dependent release were used to estimate the contributions of [Ca(2+)]res, CB, PV, calmodulin (CaM), immobile buffer fractions and Ca(2+) remaining bound to the release sensor after the first of two action potentials ('active Ca(2+)') to PPF. This analysis indicates that PPF at PN-PN synapses does not result from either buffer saturation or [Ca(2+)]res but rather from slow Ca(2+) unbinding from the release sensor.
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Affiliation(s)
- Grit Bornschein
- Carl-Ludwig Institute for Physiology, University of Leipzig, Liebigstr. 27, 04103 Leipzig, Germany
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Schmidt H, Brachtendorf S, Arendt O, Hallermann S, Ishiyama S, Bornschein G, Gall D, Schiffmann S, Heckmann M, Eilers J. Nanodomain Coupling at an Excitatory Cortical Synapse. Curr Biol 2013; 23:244-9. [DOI: 10.1016/j.cub.2012.12.007] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Revised: 12/06/2012] [Accepted: 12/07/2012] [Indexed: 10/27/2022]
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Collot M, Loukou C, Yakovlev AV, Wilms CD, Li D, Evrard A, Zamaleeva A, Bourdieu L, Léger JF, Ropert N, Eilers J, Oheim M, Feltz A, Mallet JM. Calcium rubies: a family of red-emitting functionalizable indicators suitable for two-photon Ca2+ imaging. J Am Chem Soc 2012; 134:14923-31. [PMID: 22816677 DOI: 10.1021/ja304018d] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We designed Calcium Rubies, a family of functionalizable BAPTA-based red-fluorescent calcium (Ca(2+)) indicators as new tools for biological Ca(2+) imaging. The specificity of this Ca(2+)-indicator family is its side arm, attached on the ethylene glycol bridge that allows coupling the indicator to various groups while leaving open the possibility of aromatic substitutions on the BAPTA core for tuning the Ca(2+)-binding affinity. Using this possibility we now synthesize and characterize three different CaRubies with affinities between 3 and 22 μM. Their long excitation and emission wavelengths (peaks at 586/604 nm) allow their use in otherwise challenging multicolor experiments, e.g., when combining Ca(2+) uncaging or optogenetic stimulation with Ca(2+) imaging in cells expressing fluorescent proteins. We illustrate this capacity by the detection of Ca(2+) transients evoked by blue light in cultured astrocytes expressing CatCh, a light-sensitive Ca(2+)-translocating channelrhodopsin linked to yellow fluorescent protein. Using time-correlated single-photon counting, we measured fluorescence lifetimes for all CaRubies and demonstrate a 10-fold increase in the average lifetime upon Ca(2+) chelation. Since only the fluorescence quantum yield but not the absorbance of the CaRubies is Ca(2+)-dependent, calibrated two-photon fluorescence excitation measurements of absolute Ca(2+) concentrations are feasible.
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Affiliation(s)
- Mayeul Collot
- UPMC Université Paris 06, Ecole Normale Supérieure, Paris, F-75005 France
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Levy S, Wilms CD, Brumer E, Kahn J, Pnueli L, Arava Y, Eilers J, Gitler D. SpRET: highly sensitive and reliable spectral measurement of absolute FRET efficiency. Microsc Microanal 2011; 17:176-90. [PMID: 21333032 DOI: 10.1017/s1431927610094493] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Contemporary research aims to understand biological processes not only by identifying participating proteins, but also by characterizing the dynamics of their interactions. Because Förster's Resonance Energy Transfer (FRET) is invaluable for the latter undertaking, its usage is steadily increasing. However, FRET measurements are notoriously error-prone, especially when its inherent efficiency is low, a not uncommon situation. Furthermore, many FRET methods are either difficult to implement, are not appropriate for observation of cellular dynamics, or report instrument-specific indices that hamper communication of results within the scientific community. We present here a novel comprehensive spectral methodology, SpRET, which substantially increases both the reliability and sensitivity of FRET microscopy, even under unfavorable conditions such as weak fluorescence or the presence of noise. While SpRET overcomes common pitfalls such as interchannel crosstalk and direct excitation of the acceptor, it also excels in removal of autofluorescence or background contaminations and in correcting chromatic aberrations, often overlooked factors that severely undermine FRET experiments. Finally, SpRET quantitatively reports absolute rather than relative FRET efficiency values, as well as the acceptor-to-donor molar ratio, which is critical for full and proper interpretation of FRET experiments. Thus, SpRET serves as an advanced, improved, and powerful tool in the cell biologist's toolbox.
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Affiliation(s)
- Shiri Levy
- Department of Physiology and Neurobiology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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Hallermann S, Fejtova A, Schmidt H, Weyhersmüller A, Silver RA, Gundelfinger ED, Eilers J. Bassoon speeds vesicle reloading at a central excitatory synapse. Neuron 2011; 68:710-23. [PMID: 21092860 PMCID: PMC3004039 DOI: 10.1016/j.neuron.2010.10.026] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2010] [Indexed: 01/02/2023]
Abstract
Sustained rate-coded signals encode many types of sensory modalities. Some sensory synapses possess specialized ribbon structures, which tether vesicles, to enable high-frequency signaling. However, central synapses lack these structures, yet some can maintain signaling over a wide bandwidth. To analyze the underlying molecular mechanisms, we investigated the function of the active zone core component Bassoon in cerebellar mossy fiber to granule cell synapses. We show that short-term synaptic depression is enhanced in Bassoon knockout mice during sustained high-frequency trains but basal synaptic transmission is unaffected. Fluctuation and quantal analysis as well as quantification with constrained short-term plasticity models revealed that the vesicle reloading rate was halved in the absence of Bassoon. Thus, our data show that the cytomatrix protein Bassoon speeds the reloading of vesicles to release sites at a central excitatory synapse.
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Affiliation(s)
- Stefan Hallermann
- Carl Ludwig Institute of Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany.
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Guzman SJ, Schmidt H, Franke H, Krügel U, Eilers J, Illes P, Gerevich Z. P2Y1 receptors inhibit long-term depression in the prefrontal cortex. Neuropharmacology 2010; 59:406-15. [PMID: 20570683 DOI: 10.1016/j.neuropharm.2010.05.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2009] [Revised: 05/26/2010] [Accepted: 05/27/2010] [Indexed: 01/11/2023]
Abstract
Long-term depression (LTD) is a form of synaptic plasticity that may contribute to information storage in the central nervous system. Here we report that LTD can be elicited in layer 5 pyramidal neurons of the rat prefrontal cortex by pairing low frequency stimulation with a modest postsynaptic depolarization. The induction of LTD required the activation of both metabotropic glutamate receptors of the mGlu1 subtype and voltage-sensitive Ca(2+) channels (VSCCs) of the T/R, P/Q and N types, leading to the stimulation of intracellular inositol trisphosphate (IP3) receptors by IP3 and Ca(2+). The subsequent release of Ca(2+) from intracellular stores activated the protein phosphatase cascade involving calcineurin and protein phosphatase 1. The activation of purinergic P2Y(1) receptors blocked LTD. This effect was prevented by P2Y(1) receptor antagonists and was absent in mice lacking P2Y(1) but not P2Y(2) receptors. We also found that activation of P2Y(1) receptors inhibits Ca(2+) transients via VSCCs in the apical dendrites and spines of pyramidal neurons. In addition, we show that the release of ATP under hypoxia is able to inhibit LTD by acting on postsynaptic P2Y(1) receptors. In conclusion, these data suggest that the reduction of Ca(2+) influx via VSCCs caused by the activation of P2Y(1) receptors by ATP is the possible mechanism for the inhibition of LTD in prefrontal cortex.
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Affiliation(s)
- Segundo J Guzman
- Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, Härtelstr. 16-18, 04107 Leipzig, Germany.
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Berna-Erro A, Braun A, Kraft R, Kleinschnitz C, Schuhmann MK, Stegner D, Wultsch T, Eilers J, Meuth SG, Stoll G, Nieswandt B. STIM2 regulates capacitive Ca2+ entry in neurons and plays a key role in hypoxic neuronal cell death. Sci Signal 2009; 2:ra67. [PMID: 19843959 DOI: 10.1126/scisignal.2000522] [Citation(s) in RCA: 212] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Excessive cytosolic calcium ion (Ca(2+)) accumulation during cerebral ischemia triggers neuronal cell death, but the underlying mechanisms are poorly understood. Capacitive Ca(2+) entry (CCE) is a process whereby depletion of intracellular Ca(2+) stores causes the activation of plasma membrane Ca(2+) channels. In nonexcitable cells, CCE is controlled by the endoplasmic reticulum (ER)-resident Ca(2+) sensor STIM1, whereas the closely related protein STIM2 has been proposed to regulate basal cytosolic and ER Ca(2+) concentrations and make only a minor contribution to CCE. Here, we show that STIM2, but not STIM1, is essential for CCE and ischemia-induced cytosolic Ca(2+) accumulation in neurons. Neurons from Stim2(-/-) mice showed significantly increased survival under hypoxic conditions compared to neurons from wild-type controls both in culture and in acute hippocampal slice preparations. In vivo, Stim2(-/-) mice were markedly protected from neurological damage in a model of focal cerebral ischemia. These results implicate CCE in ischemic neuronal cell death and establish STIM2 as a critical mediator of this process.
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Affiliation(s)
- Alejandro Berna-Erro
- Rudolf Virchow Center, DFG Research Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, D15 97080, Würzburg, Germany
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31
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Lappe-Siefke C, Loebrich S, Hevers W, Waidmann OB, Schweizer M, Fehr S, Fritschy JM, Dikic I, Eilers J, Wilson SM, Kneussel M. The ataxia (axJ) mutation causes abnormal GABAA receptor turnover in mice. PLoS Genet 2009; 5:e1000631. [PMID: 19759851 PMCID: PMC2744266 DOI: 10.1371/journal.pgen.1000631] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Accepted: 08/04/2009] [Indexed: 11/26/2022] Open
Abstract
Ataxia represents a pathological coordination failure that often involves functional disturbances in cerebellar circuits. Purkinje cells (PCs) characterize the only output neurons of the cerebellar cortex and critically participate in regulating motor coordination. Although different genetic mutations are known that cause ataxia, little is known about the underlying cellular mechanisms. Here we show that a mutated axJ gene locus, encoding the ubiquitin-specific protease 14 (Usp14), negatively influences synaptic receptor turnover. AxJ mouse mutants, characterized by cerebellar ataxia, display both increased GABAA receptor (GABAAR) levels at PC surface membranes accompanied by enlarged IPSCs. Accordingly, we identify physical interaction of Usp14 and the GABAAR α1 subunit. Although other currently unknown changes might be involved, our data show that ubiquitin-dependent GABAAR turnover at cerebellar synapses contributes to axJ-mediated behavioural impairment. Cerebellar ataxia describes a combination of motor symptoms and uncoordinated movements that originates from various hereditary and non-hereditary diseases. Although functional disturbances of cerebellar inhibitory output signals are thought to cause ataxia, the underlying molecular mechanisms are barely understood and medical treatment therefore remains difficult. We analysed a behavioural abnormality up to the molecular level in a mouse mutant (axJ) representing a model for ataxia. The axJ mutation reduces the expression level of a ubiquitin protease (Usp14) leading to an abnormal turnover of neurotransmitter receptors. Despite other yet unknown changes in axJ mutants, our data show that intracellular protein turnover contributes to a motor behavioural syndrome.
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Affiliation(s)
- Corinna Lappe-Siefke
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany
| | - Sven Loebrich
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany
| | - Wulf Hevers
- Carl-Ludwig-Institut für Physiologie, Universität Leipzig, Leipzig, Germany
| | - Oliver B. Waidmann
- Institut für Biochemie II, Universität Frankfurt, Frankfurt, Germany
- Klinik für Innere Medizin 1, Schwerpunkt Gastroenterologie und Hepatologie, Universität Frankfurt, Frankfurt, Germany
| | - Michaela Schweizer
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany
| | - Susanne Fehr
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany
| | - Jean-Marc Fritschy
- Institute of Pharmacology und Toxicology, University of Zurich, Zurich, Switzerland
| | - Ivan Dikic
- Institut für Biochemie II, Universität Frankfurt, Frankfurt, Germany
| | - Jens Eilers
- Carl-Ludwig-Institut für Physiologie, Universität Leipzig, Leipzig, Germany
| | - Scott M. Wilson
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Matthias Kneussel
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany
- * E-mail:
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Abstract
This protocol describes the loading of individual cells with fluorescent probes via patch pipettes. The patch-clamp methodology has been successfully used for single-cell dye labeling in cultured neurons, brain slices, and in vivo preparations. A broad range of dyes can be used with this loading technique. Markers for morphological reconstruction (e.g., Lucifer yellow); ion-sensitive indicator dyes for monitoring second-messenger cascades (e.g., fura-2); and dye-labeled proteins for fluorescence resonance energy transfer (FRET), fluorescence correlation spectroscopy (FCS), and fluorescence recovery after photobleaching (FRAP) studies are all suitable for patch-clamp loading. The most widespread application of this technique has been for Ca(2+) imaging. Whole-cell patch-clamp recordings represent a versatile loading technique that allows combined electrophysiological and optical measurements at a quantitative level.
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Schaarschmidt G, Schewtschik S, Kraft R, Wegner F, Eilers J, Schwarz J, Schmidt H. A new culturing strategy improves functional neuronal development of human neural progenitor cells. J Neurochem 2009; 109:238-47. [DOI: 10.1111/j.1471-4159.2009.05954.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Groszer M, Keays DA, Deacon RM, de Bono JP, Prasad-Mulcare S, Gaub S, Baum MG, French CA, Nicod J, Coventry JA, Enard W, Fray M, Brown SD, Nolan PM, Pääbo S, Channon KM, Costa RM, Eilers J, Ehret G, Rawlins JNP, Fisher SE. Impaired synaptic plasticity and motor learning in mice with a point mutation implicated in human speech deficits. Curr Biol 2008; 18:354-62. [PMID: 18328704 PMCID: PMC2917768 DOI: 10.1016/j.cub.2008.01.060] [Citation(s) in RCA: 194] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Revised: 01/28/2008] [Accepted: 01/29/2008] [Indexed: 01/17/2023]
Abstract
The most well-described example of an inherited speech and language disorder is that observed in the multigenerational KE family, caused by a heterozygous missense mutation in the FOXP2 gene. Affected individuals are characterized by deficits in the learning and production of complex orofacial motor sequences underlying fluent speech and display impaired linguistic processing for both spoken and written language. The FOXP2 transcription factor is highly similar in many vertebrate species, with conserved expression in neural circuits related to sensorimotor integration and motor learning. In this study, we generated mice carrying an identical point mutation to that of the KE family, yielding the equivalent arginine-to-histidine substitution in the Foxp2 DNA-binding domain. Homozygous R552H mice show severe reductions in cerebellar growth and postnatal weight gain but are able to produce complex innate ultrasonic vocalizations. Heterozygous R552H mice are overtly normal in brain structure and development. Crucially, although their baseline motor abilities appear to be identical to wild-type littermates, R552H heterozygotes display significant deficits in species-typical motor-skill learning, accompanied by abnormal synaptic plasticity in striatal and cerebellar neural circuits.
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Affiliation(s)
- Matthias Groszer
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
| | - David A. Keays
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
| | - Robert M.J. Deacon
- Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, United Kingdom
| | - Joseph P. de Bono
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DU, United Kingdom
| | - Shweta Prasad-Mulcare
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Room TS-20D, MSC 9411, Bethesda, Maryland 20852-9411
| | - Simone Gaub
- Institute of Neurobiology, University of Ulm, 89069 Ulm, Germany
| | - Muriel G. Baum
- Carl-Ludwig-Institute for Physiology, University of Leipzig, 04103 Leipzig, Germany
| | - Catherine A. French
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
| | - Jérôme Nicod
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
| | - Julie A. Coventry
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
| | - Wolfgang Enard
- Max-Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany
| | - Martin Fray
- Medical Research Council Mammalian Genetics Unit, Harwell, Didcot, Oxfordshire OX11 0RD, United Kingdom
| | - Steve D.M. Brown
- Medical Research Council Mammalian Genetics Unit, Harwell, Didcot, Oxfordshire OX11 0RD, United Kingdom
| | - Patrick M. Nolan
- Medical Research Council Mammalian Genetics Unit, Harwell, Didcot, Oxfordshire OX11 0RD, United Kingdom
| | - Svante Pääbo
- Max-Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany
| | - Keith M. Channon
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DU, United Kingdom
| | - Rui M. Costa
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Room TS-20D, MSC 9411, Bethesda, Maryland 20852-9411
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, University of Leipzig, 04103 Leipzig, Germany
| | - Günter Ehret
- Institute of Neurobiology, University of Ulm, 89069 Ulm, Germany
| | - J. Nicholas P. Rawlins
- Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, United Kingdom
| | - Simon E. Fisher
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
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Livingston J, Schmid B, Redemann J, Russell PB, Ramirez SA, Eilers J, Gore W, Howard S, Pommier J, Fetzer EJ, Seemann SW, Borbas E, Wolfe DE, Thompson AM. Comparison of water vapor measurements by airborne Sun photometer and near-coincident in situ and satellite sensors during INTEX/ITCT 2004. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jd007733] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Russell PB, Livingston JM, Redemann J, Schmid B, Ramirez SA, Eilers J, Kahn R, Chu DA, Remer L, Quinn PK, Rood MJ, Wang W. Multi-grid-cell validation of satellite aerosol property retrievals in INTEX/ITCT/ICARTT 2004. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jd007606] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Abstract
The Ca(2+) -binding protein (CaBP) parvalbumin (PV) is strongly expressed in cerebellar Purkinje neurones (PNs). It is considered a pure Ca(2+) buffer, lacking any Ca(2+) sensor function. Consistent with this notion, no PV ligand was found in dendrites of PNs. Recently, however, we observed for a related CaBP that ligand-targeting differs substantially between dendrites and axons. Thus, here we quantified the diffusion of dye-labelled PV in axons, somata and nuclei of PNs by two-photon fluorescence recovery after photobleaching (FRAP). In all three compartments the fluorescence rapidly returned to baseline, indicating that no large or immobile PV ligand was present. In the axon, FRAP was well described by a one-dimensional diffusion equation and a diffusion coefficient (D) of 12 (IQR 6-20) micro m(2)/s. For the soma and nucleus a three-dimensional model yielded similar D values. The diffusional mobility in these compartments was approximately 3 times smaller than in dendrites. Based on control experiments with fluorescein dextrans, we attributed this reduced mobility of PV to different cytoplasmic properties rather than to specific PV interactions in these compartments. Our findings support the notion that PV functions as a pure Ca(2+) buffer and will aid simulations of neuronal Ca(2+) signalling.
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Affiliation(s)
- Hartmut Schmidt
- Carl-Ludwig-Institut für Physiologie, Abteilung Neurophysiologie, Medizinische Fakultät, Universität Leipzig, Leipzig, Germany.
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Schmidt H, Kunerth S, Wilms C, Strotmann R, Eilers J. Spino-dendritic cross-talk in rodent Purkinje neurons mediated by endogenous Ca2+-binding proteins. J Physiol 2007; 581:619-29. [PMID: 17347272 PMCID: PMC2075171 DOI: 10.1113/jphysiol.2007.127860] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The range of actions of the second messenger Ca(2+) is a key determinant of neuronal excitability and plasticity. For dendritic spines, there is on-going debate regarding how diffusional efflux of Ca(2+) affects spine signalling. However, the consequences of spino-dendritic coupling for dendritic Ca(2+) homeostasis and downstream signalling cascades have not been explored to date. We addressed this question by four-dimensional computer simulations, which were based on Ca(2+)-imaging data from mice that either express or lack distinct endogenous Ca(2+)-binding proteins. Our simulations revealed that single active spines do not affect dendritic Ca(2+) signalling. Neighbouring, coactive spines, however, induce sizeable increases in dendritic [Ca(2+)](i) when they process slow synaptic Ca(2+) signals, such as those implicated in the induction of long-term plasticity. This spino-dendritic coupling is mediated by buffered diffusion, specifically by diffusing calbindin-bound Ca(2+). This represents a central mechanism for activating calmodulin in dendritic shafts and therefore a novel form of signal integration in spiny dendrites.
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Affiliation(s)
- Hartmut Schmidt
- Carl-Ludwig-Institut für Physiologie, Liebigstrasse 27, 04103 Leipzig, Germany.
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Abstract
We analyzed the suitability of various Ca2+-indicator dyes for quantitative two-photon fluorescence-lifetime imaging. Although fura-2, fluo-3, BTC and calcein did not show useful Ca2+-dependent lifetime changes, calcium orange, calcium green-1, oregon green-2 and -5N, as well as magnesium green allowed to quantify the Ca2+-free and Ca2+-bound dye fractions by a double-exponential lifetime analysis. For the latter dyes, we derived calibration formalisms that correct for lifetime distortions by dye impurities and Ca2+-dependent extinction coefficients.
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Affiliation(s)
- Christian D Wilms
- University Leipzig, Carl-Ludwig-Institute for Physiology, Liebigstr. 27, 04103 Leipzig, Germany.
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Wood J, Eilers J, DeVetten M, Freifeld A. 421: Improving yield from blood cultures for transplant patients. Biol Blood Marrow Transplant 2007. [DOI: 10.1016/j.bbmt.2007.01.051] [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: 11/24/2022]
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Wilms CD, Schmidt H, Eilers J. Quantitative two-photon Ca2+ imaging via fluorescence lifetime analysis. Cell Calcium 2006; 40:73-9. [PMID: 16690123 DOI: 10.1016/j.ceca.2006.03.006] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Revised: 03/10/2006] [Accepted: 03/16/2006] [Indexed: 11/26/2022]
Abstract
Two-photon microscopy (TPM) revolutionized Ca2+ imaging by allowing recordings in the depth of intact tissue and live organisms. A serious limitation in TPM, however, is the lack of an accurate and straightforward approach for the quantification of Ca2+ signals, an ability that became an invaluable tool in fluorescence microscopy. Here, we present time-correlated fluorescence lifetime imaging (tcFLIM) as a ratiometric method for the quantification of Ca2+ signals in TPM. The fluorescence lifetime of the Ca2+-indicator dye Oregon Green BAPTA-1 (OGB-1) can be recorded using the approximately 80 MHz excitation pulses utilized in TPM. It shows a Ca2+ dependence that can be explained by the Ca2+-affinity, spectral properties and purity of the dye. Pixel-wise lifetime recordings, controlled by a laser-scanning microscope, allowed quantitative Ca2+ imaging in full-frame and linescan mode. Although we focused on the high-affinity Ca2+ indicator OGB-1, our tcFLIM-based quantification is applicable to other Ca2+ dyes and to fluorescence indicators in general.
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Affiliation(s)
- Christian D Wilms
- Leipzig University, Carl-Ludwig-Institute for Physiology, Liebigstr. 27, 04103 Leipzig, Germany.
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Schmid B, Ferrare R, Flynn C, Elleman R, Covert D, Strawa A, Welton E, Turner D, Jonsson H, Redemann J, Eilers J, Ricci K, Hallar AG, Clayton M, Michalsky J, Smirnov A, Holben B, Barnard J. How well do state-of-the-art techniques measuring the vertical profile of tropospheric aerosol extinction compare? ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005jd005837] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Schmidt H, Schwaller B, Eilers J. Calbindin D28k targets myo-inositol monophosphatase in spines and dendrites of cerebellar Purkinje neurons. Proc Natl Acad Sci U S A 2005; 102:5850-5. [PMID: 15809430 PMCID: PMC556286 DOI: 10.1073/pnas.0407855102] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2004] [Indexed: 11/18/2022] Open
Abstract
The Ca(2+)-binding protein calbindin D28k (CB) is vital for the normal function of the central nervous system but its specific functional role is largely unclear. CB is typically described as a mobile Ca(2+)buffer that shapes the spatiotemporal extent of cellular Ca(2+)signals. Recent biochemical data, however, indicate that CB also has characteristics of a Ca(2+) sensor and activates myo-inositol monophosphatase (IMPase), a key enzyme of the inositol-1,4,5-trisphosphate signaling cascade and an assumed target of mood-stabilizing drugs in the treatment of bipolar disorder. Here, we show that CB interacts with IMPase in cerebellar Purkinje neurons, a cell type well known to rely on inositol-1,4,5-trisphosphate-dependent synaptic integration. Quantification of the mobility of dye-labeled CB with two-photon fluorescence recovery after photobleaching revealed that a substantial fraction of CB is immobilized in spines and dendrites, but not in axons. Immobilization occurs over several seconds, is increased by suprathreshold synaptic activity, and can be relieved by a synthetic peptide that resembles the putative CB-binding site of IMPase, indicating that CB binds to immobilized IMPase. Measurements of the apparent diffusion coefficients of CB imply that CB does not interact with cytosolic IMPase or that the latter is present only in minute amounts in the spiny dendrites of Purkinje neurons. Our results suggest that CB acts as an activity-dependent sensor that targets membrane/cytoskeleton-bound IMPase in central neurons.
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Affiliation(s)
- Hartmut Schmidt
- Carl-Ludwig-Institut für Physiologie, Abteilung Neurophysiologie, Medizinische Fakultät, Universität Leipzig, 04103 Leipzig, Germany.
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Schmidt H, Stiefel KM, Racay P, Schwaller B, Eilers J. Mutational analysis of dendritic Ca2+ kinetics in rodent Purkinje cells: role of parvalbumin and calbindin D28k. J Physiol 2003; 551:13-32. [PMID: 12813159 PMCID: PMC2343131 DOI: 10.1113/jphysiol.2002.035824] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The mechanisms governing the kinetics of climbing fibre-mediated Ca2+ transients in spiny dendrites of cerebellar Purkinje cells (PCs) were quantified with high-resolution confocal Ca2+ imaging. Ca2+ dynamics in parvalbumin (PV-/-) and parvalbumin/calbindin D28k null-mutant (PV/CB-/-) mice were compared with responses in wild-type (WT) animals. In the WT, Ca2+ transients in dendritic shafts were characterised by double exponential decay kinetics that were not due to buffered Ca2+ diffusion or saturation of the indicator dye. Ca2+ transients in PV-/- PCs reached the same peak amplitude as in the WT but the biphasic nature of the decay was less pronounced, an effect that could be attributed to PV's slow binding kinetics. In contrast, peak amplitudes in PV/CB-/- PCs were about two times higher than in the WT and the decay became nearly monophasic. Numerical simulations indicate that the residual deviation from a single exponential decay in PV/CB-/- is due to saturation of the Ca2+ indicator dye. Furthermore, the simulations imply that the effect of uncharacterised endogenous Ca2+ binding proteins is negligible, that buffered diffusion and dye saturation significantly affects spineous Ca2+ transients but not those in the dendritic shafts, and that neither CB nor PV undergoes saturation in spines or dendrites during climbing fibre-evoked Ca2+ transients. Calbindin's medium-affinity binding sites are fast enough to reduce the peak amplitude of the Ca2+ signal. However, similar to PV, delayed binding by CB leads to biphasic Ca2+ decay kinetics. Our results suggest that the distinct kinetics of PV and CB underlie the biphasic kinetics of synaptically evoked Ca2+ transients in dendritic shafts of PCs.
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Affiliation(s)
- Hartmut Schmidt
- Department of Neurophysiology, Max-Planck-Institute for Brain Research, 60528 Frankfurt, Germany
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Schmidt H, Brown EB, Schwaller B, Eilers J. Diffusional mobility of parvalbumin in spiny dendrites of cerebellar Purkinje neurons quantified by fluorescence recovery after photobleaching. Biophys J 2003; 84:2599-608. [PMID: 12668468 PMCID: PMC1302826 DOI: 10.1016/s0006-3495(03)75065-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Ca(2+)-binding proteins (CaBPs) represent key factors for the modulation of cellular Ca(2+) dynamics. Especially in thin extensions of nerve cells, Ca(2+) binding and buffered diffusion of Ca(2+) by CaBPs is assumed to effectively control the spatio-temporal extend of Ca(2+) signals. However, no quantitative data about the mobility of specific CaBPs in the neuronal cytosol are available. We quantified the diffusion of the endogenous CaPB parvalbumin (PV) in spiny dendrites of cerebellar Purkinje neurons with two-photon fluorescence recovery after photobleaching. Fluorescently labeled PV diffused readily between spines and dendrites with a median time constant of 49 ms (37-61 ms, interquartile range). Based on published data on spine geometry, this value corresponds to an apparent diffusion coefficient of 43 microm(2) s(-1) (34-56 microm(2) s(-1)). The absence of large or immobile binding partners for PV was confirmed in PV null-mutant mice. Our data validate the common but so far unproven assumption that PV is highly mobile in neurons and will facilitate simulations of neuronal Ca(2+) buffering. Our experimental approach represents a versatile tool for quantifying the mobility of proteins in neuronal dendrites.
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Affiliation(s)
- Hartmut Schmidt
- Department of Neurophysiology, Max-Planck-Institute for Brain Research, 60528 Frankfurt, Germany.
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Loewenstein M, Jost H, Grose J, Eilers J, Lynch D, Jensen S, Marmie J. Argus: a new instrument for the measurement of the stratospheric dynamical tracers, N2O and CH4. Spectrochim Acta A Mol Biomol Spectrosc 2002; 58:2329-2345. [PMID: 12353683 DOI: 10.1016/s1386-1425(02)00048-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We describe here a new instrument for the simultaneous, in situ measurement of the stratospheric tracer molecules, nitrous oxide (N2O) and methane (CH4). Argus is unique in its small size making it well suited for limited payload atmospheric research platforms. Argus employs second harmonic spectroscopy using tunable lead-salt diode lasers emitting in the mid-infrared. We first explain the Argus design philosophy followed by detailed descriptions of the instrument's optical, mechanical, and thermal sub-systems. Argus employs an in-flight calibration system providing real time calibrations and tightly constrained uncertainty estimates of the returned data. Data analysis is carried out using non-linear least-squares model fits to the acquired second harmonic spectra. A sampling of Argus data acquired on a recent stratospheric research campaign in the Arctic winter is presented.
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Abstract
1. Cellular responses to GABA(A) receptor activation were studied in developing cerebellar Purkinje neurones (PNs) in brain slices obtained from 2- to 22-day-old rats. Two-photon fluorescence imaging of fura-2-loaded cells and perforated-patch recordings were used to monitor intracellular Ca2+ transients and to estimate the reversal potential of GABA-induced currents, respectively. 2. During the 1st postnatal week, focal application of GABA or the GABA(A) receptor agonist muscimol evoked transient increases in [Ca2+]i in immature PNs. These Ca2+ transients were reversibly abolished by the GABA(A) receptor antagonist bicuculline and by Ni2+, a blocker of voltage-activated Ca2+ channels. 3. Perforated-patch recordings were used to measure the reversal potential of GABA-evoked currents (E(GABA)) at different stages of development. It was found that E(GABA) was about -44 mV at postnatal day 3 (P3), it shifted to gradually more negative values during the 1st week and finally equilibrated at -87 mV at around the end of the 2nd postnatal week. This transition was well described by a sigmoidal function. The largest change in E(GABA) was -7 mV x day(-1), which occurred at around P6. 4. The transition in GABA-mediated signalling occurs during a period in which striking changes in PN morphology and synaptic connectivity are known to take place. Since such changes were shown to be Ca2+ dependent, we propose that GABA-evoked Ca2+ signalling is one of the critical determinants for the normal development of cerebellar PNs.
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Affiliation(s)
- J Eilers
- Abteilung Neurophysiologie, Max-Planck-Institut für Hirnforschung, 60528 Frankfurt, Germany.
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Affiliation(s)
- N Haas
- Department of Dermatology, Humboldt-University Berlin, Germany
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Sonis ST, Oster G, Fuchs H, Bellm L, Bradford WZ, Edelsberg J, Hayden V, Eilers J, Epstein JB, LeVeque FG, Miller C, Peterson DE, Schubert MM, Spijkervet FK, Horowitz M. Oral mucositis and the clinical and economic outcomes of hematopoietic stem-cell transplantation. J Clin Oncol 2001; 19:2201-5. [PMID: 11304772 DOI: 10.1200/jco.2001.19.8.2201] [Citation(s) in RCA: 439] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PURPOSE To explore the relationship between oral mucositis and selected clinical and economic outcomes in blood and marrow transplant patients. PATIENTS AND METHODS Subjects consisted of 92 transplant patients from eight centers who participated in a multinational pilot study of a new oral mucositis scoring system (Oral Mucositis Assessment Scale [OMAS]). In the pilot study, patients were evaluated for erythema and ulceration/pseudomembrane formation beginning on the first day of conditioning and continuing for 28 days. We examined the relationship between patients' peak OMAS scores and days with fever (body temperature > 38.0 degrees C), the occurrence of significant infection, days of total parenteral nutrition (TPN), and days of injectable narcotic therapy (all over 28 days), days in hospital (over 60 days), total hospital charges for the index admission, and vital status at 100 days. RESULTS Patients' peak OMAS scores spanned the full range of possible values (0 to 5) and were significantly (P <.05) correlated with all of the outcomes of interest except days with fever (P =.21). In analyses controlling for type of graft (autologous v allogeneic) and study center, a 1-point increase in peak OMAS score was associated with (1) 1.0 additional day with fever (P <.01), (2) a 2.1-fold increase in risk of significant infection (P <.01), (3) 2.7 additional days of TPN (P <.0001), (4) 2.6 additional days of injectable narcotic therapy (P <.0001), (5) 2.6 additional days in hospital (P <.01), (6) $25,405 in additional hospital charges (P <.0001), and (7) a 3.9-fold increase in 100-day mortality risk (P <.01). Mean hospital charges were $42,749 higher among patients with evidence of ulceration compared with those without (P =.06). CONCLUSION Oral mucositis is associated with significantly worse clinical and economic outcomes in blood and marrow transplantation.
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Affiliation(s)
- S T Sonis
- Brigham and Women's Hospital and Harvard School of Dental Medicine, Boston, MA, USA
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