1
|
Chichorro JG, Gambeta E, Baggio DF, Zamponi GW. Voltage-gated Calcium Channels as Potential Therapeutic Targets in Migraine. THE JOURNAL OF PAIN 2024; 25:104514. [PMID: 38522594 DOI: 10.1016/j.jpain.2024.03.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 03/06/2024] [Accepted: 03/12/2024] [Indexed: 03/26/2024]
Abstract
Migraine is a complex and highly incapacitating neurological disorder that affects around 15% of the general population with greater incidence in women, often at the most productive age of life. Migraine physiopathology is still not fully understood, but it involves multiple mediators and events in the trigeminovascular system and the central nervous system. The identification of calcitonin gene-related peptide as a key mediator in migraine physiopathology has led to the development of effective and highly selective antimigraine therapies. However, this treatment is neither accessible nor effective for all migraine sufferers. Thus, a better understanding of migraine mechanisms and the identification of potential targets are still clearly warranted. Voltage-gated calcium channels (VGCCs) are widely distributed in the trigeminovascular system, and there is accumulating evidence of their contribution to the mechanisms associated with headache pain. Several drugs used in migraine abortive or prophylactic treatment target VGCCs, which probably contributes to their analgesic effect. This review aims to summarize the current evidence of VGGC contribution to migraine physiopathology and to discuss how current pharmacological options for migraine treatment interfere with VGGC function. PERSPECTIVE: Calcitonin gene-related peptide (CGRP) represents a major migraine mediator, but few studies have investigated the relationship between CGRP and VGCCs. CGRP release is calcium channel-dependent and VGGCs are key players in familial migraine. Further studies are needed to determine whether VGCCs are suitable molecular targets for treating migraine.
Collapse
Affiliation(s)
- Juliana G Chichorro
- Biological Sciences Sector, Department of Pharmacology, Federal University of Parana, Curitiba, Parana, Brazil.
| | - Eder Gambeta
- Cumming School of Medicine, Department of Clinical Neuroscience, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Darciane F Baggio
- Biological Sciences Sector, Department of Pharmacology, Federal University of Parana, Curitiba, Parana, Brazil
| | - Gerald W Zamponi
- Cumming School of Medicine, Department of Clinical Neuroscience, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| |
Collapse
|
2
|
Chin M, Kaeser PS. The intracellular C-terminus confers compartment-specific targeting of voltage-gated calcium channels. Cell Rep 2024; 43:114428. [PMID: 38996073 DOI: 10.1016/j.celrep.2024.114428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 06/07/2024] [Accepted: 06/18/2024] [Indexed: 07/14/2024] Open
Abstract
To achieve the functional polarization that underlies brain computation, neurons sort protein material into distinct compartments. Ion channel composition, for example, differs between axons and dendrites, but the molecular determinants for their polarized trafficking remain obscure. Here, we identify mechanisms that target voltage-gated Ca2+ channels (CaVs) to distinct subcellular compartments. In hippocampal neurons, CaV2s trigger neurotransmitter release at the presynaptic active zone, and CaV1s localize somatodendritically. After knockout of all three CaV2s, expression of CaV2.1, but not CaV1.3, restores neurotransmitter release. We find that chimeric CaV1.3s with CaV2.1 intracellular C-termini localize to the active zone, mediate synaptic vesicle exocytosis, and render release sensitive to CaV1 blockers. This dominant targeting function of the CaV2.1 C-terminus requires the first EF hand in its proximal segment, and replacement of the CaV2.1 C-terminus with that of CaV1.3 abolishes CaV2.1 active zone localization and function. We conclude that CaV intracellular C-termini mediate compartment-specific targeting.
Collapse
Affiliation(s)
- Morven Chin
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
| |
Collapse
|
3
|
McCarthy CI, Kavalali ET. Nano-organization of synaptic calcium signaling. Biochem Soc Trans 2024; 52:1459-1471. [PMID: 38752834 DOI: 10.1042/bst20231385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 04/17/2024] [Accepted: 05/03/2024] [Indexed: 06/27/2024]
Abstract
Recent studies suggest an exquisite structural nano-organization within single synapses, where sites of evoked fusion - marked by clustering of synaptic vesicles, active zone proteins and voltage-gated calcium channels - are directly juxtaposed to postsynaptic receptor clusters within nanocolumns. This direct nanometer scale alignment between presynaptic fusion apparatus and postsynaptic receptors is thought to ensure the fidelity of synaptic signaling and possibly allow multiple distinct signals to occur without interference from each other within a single active zone. The functional specificity of this organization is made possible by the inherent nano-organization of calcium signals, where all the different calcium sources such as voltage-gated calcium channels, intracellular stores and store-operated calcium entry have dedicated local targets within their nanodomain to ensure precision of action. Here, we discuss synaptic nano-organization from the perspective of calcium signals, where some of the principal findings from early work in the 1980s continue to inspire current studies that exploit new genetic tools and super-resolution imaging technologies.
Collapse
Affiliation(s)
- Clara I McCarthy
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37240-7933, U.S.A
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37240-7933, U.S.A
| | - Ege T Kavalali
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37240-7933, U.S.A
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37240-7933, U.S.A
| |
Collapse
|
4
|
Ralowicz AJ, Hokeness S, Hoppa MB. Frequency of Spontaneous Neurotransmission at Individual Boutons Corresponds to the Size of the Readily Releasable Pool of Vesicles. J Neurosci 2024; 44:e1253232024. [PMID: 38383495 PMCID: PMC11063817 DOI: 10.1523/jneurosci.1253-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 02/09/2024] [Accepted: 02/13/2024] [Indexed: 02/23/2024] Open
Abstract
Synapses maintain two forms of neurotransmitter release to support communication in the brain. First, evoked neurotransmitter release is triggered by the invasion of an action potential (AP) across en passant boutons that form along axons. The probability of evoked release (Pr) varies substantially across boutons, even within a single axon. Such heterogeneity is the result of differences in the probability of a single synaptic vesicle (SV) fusing (Pv) and in the number of vesicles available for immediate release, known as the readily releasable pool (RRP). Spontaneous release (also known as a mini) is an important form of neurotransmission that occurs in the absence of APs. Because it cannot be triggered with electrical stimulation, much less is known about potential heterogeneity in the frequency of spontaneous release between boutons. We utilized a photostable and bright fluorescent indicator of glutamate release (iGluSnFR3) to quantify both spontaneous and evoked release at individual glutamatergic boutons. We found that the rate of spontaneous release is quite heterogenous at the level of individual boutons. Interestingly, when measuring both evoked and spontaneous release at single synapses, we found that boutons with the highest rates of spontaneous release also displayed the largest evoked responses. Using a new optical method to measure RRP at individual boutons, we found that this heterogeneity in spontaneous release was strongly correlated with the size of the RRP, but not related to Pv. We conclude that the RRP is a critical and dynamic aspect of synaptic strength that contributes to both evoked and spontaneous vesicle release.
Collapse
Affiliation(s)
- Amelia J Ralowicz
- Department of Biology, Dartmouth College, Hanover, New Hampshire 03755
| | - Sasipha Hokeness
- Department of Biology, Dartmouth College, Hanover, New Hampshire 03755
| | - Michael B Hoppa
- Department of Biology, Dartmouth College, Hanover, New Hampshire 03755
| |
Collapse
|
5
|
Tsentsevitsky AN, Khuzakhmetova VF, Bukharaeva EA, Petrov AM. The Mechanism of α2 adrenoreceptor-dependent Modulation of Neurotransmitter Release at the Neuromuscular Junctions. Neurochem Res 2024; 49:453-465. [PMID: 37897557 DOI: 10.1007/s11064-023-04052-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 09/26/2023] [Accepted: 10/17/2023] [Indexed: 10/30/2023]
Abstract
α2-Adrenoreceptors (ARs) are main Gi-protein coupled autoreceptors in sympathetic nerve terminals and targets for dexmedetomidine (DEX), a widely used sedative. We hypothesize that α2-ARs are also potent regulators of neuromuscular transmission via G protein-gated inwardly rectifying potassium (GIRK) channels. Using extracellular microelectrode recording of postsynaptic potentials, we found DEX-induced inhibition of spontaneous and evoked neurotransmitter release as well as desynchronization of evoked exocytotic events in the mouse diaphragm neuromuscular junction. These effects were suppressed by SKF-86,466, a selective α2-AR antagonist. An activator of GIRK channels ML297 had the same effects on neurotransmitter release as DEX. By contrast, inhibition of GIRK channels with tertiapin-Q prevented the action of DEX on evoked neurotransmitter release, but not on spontaneous exocytosis. The synaptic vesicle exocytosis is strongly dependent on Ca2+ influx through voltage-gated Ca2+ channels (VGCCs), which can be negatively regulated via α2-AR - GIRK channel axis. Indeed, inhibition of P/Q-, L-, N- or R-type VGCCs prevented the inhibitory action of DEX on evoked neurotransmitter release; antagonists of P/Q- and N-type channels also suppressed the DEX-mediated desynchronization of evoked exocytotic events. Furthermore, inhibition of P/Q-, L- or N-type VGCCs precluded the frequency decrease of spontaneous exocytosis upon DEX application. Thus, α2-ARs acting via GIRK channels and VGCCs (mainly, P/Q- and N-types) exert inhibitory effect on the neuromuscular communication by attenuating and desynchronizing evoked exocytosis. In addition, α2-ARs can suppress spontaneous exocytosis through GIRK channel-independent, but VGCC-dependent pathway.
Collapse
Affiliation(s)
- Andrei N Tsentsevitsky
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, 2/31 Lobachevsky St, Kazan, 420111, RT, Russia
| | - Venera F Khuzakhmetova
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, 2/31 Lobachevsky St, Kazan, 420111, RT, Russia
| | - Ellya A Bukharaeva
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, 2/31 Lobachevsky St, Kazan, 420111, RT, Russia
| | - Alexey M Petrov
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, 2/31 Lobachevsky St, Kazan, 420111, RT, Russia.
- Kazan State Medical University, 49 Butlerova St, Kazan, 420012, RT, Russia.
- Kazan Federal University, 18 Kremlyovskaya Street, Kazan, 420008, Russia.
| |
Collapse
|
6
|
Vasu SO, Kaphzan H. Direct Current Stimulation Modulates Synaptic Facilitation via Distinct Presynaptic Calcium Channels. Int J Mol Sci 2023; 24:16866. [PMID: 38069188 PMCID: PMC10706473 DOI: 10.3390/ijms242316866] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 11/23/2023] [Accepted: 11/23/2023] [Indexed: 12/18/2023] Open
Abstract
Transcranial direct current stimulation (tDCS) is a subthreshold neurostimulation technique known for ameliorating neuropsychiatric conditions. The principal mechanism of tDCS is the differential polarization of subcellular neuronal compartments, particularly the axon terminals that are sensitive to external electrical fields. Yet, the underlying mechanism of tDCS is not fully clear. Here, we hypothesized that direct current stimulation (DCS)-induced modulation of presynaptic calcium channel conductance alters axon terminal dynamics with regard to synaptic vesicle release. To examine the involvement of calcium-channel subtypes in tDCS, we recorded spontaneous excitatory postsynaptic currents (sEPSCs) from cortical layer-V pyramidal neurons under DCS while selectively inhibiting distinct subtypes of voltage-dependent calcium channels. Blocking P/Q or N-type calcium channels occluded the effects of DCS on sEPSCs, demonstrating their critical role in the process of DCS-induced modulation of spontaneous vesicle release. However, inhibiting T-type calcium channels did not occlude DCS-induced modulation of sEPSCs, suggesting that despite being active in the subthreshold range, T-type calcium channels are not involved in the axonal effects of DCS. DCS modulates synaptic facilitation by regulating calcium channels in axon terminals, primarily via controlling P/Q and N-type calcium channels, while T-type calcium channels are not involved in this mechanism.
Collapse
Affiliation(s)
| | - Hanoch Kaphzan
- Sagol Department of Neurobiology, University of Haifa, Haifa 3103301, Israel
| |
Collapse
|
7
|
Wang CS, Monteggia LM, Kavalali ET. Spatially non-overlapping Ca 2+ signals drive distinct forms of neurotransmission. Cell Rep 2023; 42:113201. [PMID: 37777959 PMCID: PMC10842353 DOI: 10.1016/j.celrep.2023.113201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 06/23/2023] [Accepted: 09/16/2023] [Indexed: 10/03/2023] Open
Abstract
Calcium (Ca2+) signaling is tightly regulated within a presynaptic bouton. Here, we visualize Ca2+ signals within hippocampal presynaptic boutons using GCaMP8s tagged to synaptobrevin, a synaptic vesicle protein. We identify evoked presynaptic Ca2+ transients (ePreCTs) that derive from synchronized voltage-gated Ca2+ channel openings, spontaneous presynaptic Ca2+ transients (sPreCTs) that originate from ryanodine sensitive Ca2+ stores, and a baseline Ca2+ signal that arises from stochastic voltage-gated Ca2+ channel openings. We find that baseline Ca2+, but not sPreCTs, contributes to spontaneous glutamate release. We employ photobleaching as a use-dependent tool to probe nano-organization of Ca2+ signals and observe that all three occur in non-overlapping domains within the synapse at near-resting conditions. However, increased depolarization induces intermixing of these Ca2+ domains via both local and non-local synaptic vesicle turnover. Our findings reveal nanosegregation of Ca2+ signals within a presynaptic terminal that derive from multiple sources and in turn drive specific modes of neurotransmission.
Collapse
Affiliation(s)
- Camille S Wang
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 3729-7933, USA
| | - Lisa M Monteggia
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 3729-7933, USA; Department of Pharmacology, Vanderbilt University, Nashville, TN 37240-7933, USA
| | - Ege T Kavalali
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 3729-7933, USA; Department of Pharmacology, Vanderbilt University, Nashville, TN 37240-7933, USA.
| |
Collapse
|
8
|
Norman CA, Krishnakumar SS, Timofeeva Y, Volynski KE. The release of inhibition model reproduces kinetics and plasticity of neurotransmitter release in central synapses. Commun Biol 2023; 6:1091. [PMID: 37891212 PMCID: PMC10611806 DOI: 10.1038/s42003-023-05445-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 10/11/2023] [Indexed: 10/29/2023] Open
Abstract
Calcium-evoked release of neurotransmitters from synaptic vesicles (SVs) is catalysed by SNARE proteins. The predominant view is that, at rest, complete assembly of SNARE complexes is inhibited ('clamped') by synaptotagmin and complexin molecules. Calcium binding by synaptotagmins releases this fusion clamp and triggers fast SV exocytosis. However, this model has not been quantitatively tested over physiological timescales. Here we describe an experimentally constrained computational modelling framework to quantitatively assess how the molecular architecture of the fusion clamp affects SV exocytosis. Our results argue that the 'release-of-inhibition' model can indeed account for fast calcium-activated SV fusion, and that dual binding of synaptotagmin-1 and synaptotagmin-7 to the same SNARE complex enables synergistic regulation of the kinetics and plasticity of neurotransmitter release. The developed framework provides a powerful and adaptable tool to link the molecular biochemistry of presynaptic proteins to physiological data and efficiently test the plausibility of calcium-activated neurotransmitter release models.
Collapse
Affiliation(s)
- Christopher A Norman
- University College London Institute of Neurology, University College London, London, WC1N 3BG, UK
- Department of Computer Science, University of Warwick, Coventry, CV4 7AL, UK
- Mathematics for Real-World Systems Centre for Doctoral Training, University of Warwick, Coventry, CV4 7AL, UK
| | - Shyam S Krishnakumar
- University College London Institute of Neurology, University College London, London, WC1N 3BG, UK.
- Department of Neurology, Yale Nanobiology Institute, Yale University School of Medicine, New Haven, CT, 06510, USA.
| | - Yulia Timofeeva
- University College London Institute of Neurology, University College London, London, WC1N 3BG, UK.
- Department of Computer Science, University of Warwick, Coventry, CV4 7AL, UK.
| | - Kirill E Volynski
- University College London Institute of Neurology, University College London, London, WC1N 3BG, UK.
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, 06510, USA.
| |
Collapse
|
9
|
Spicarova D, Nerandzic V, Muzik D, Pontearso M, Bhattacharyya A, Nagy I, Palecek J. Inhibition of synaptic transmission by anandamide precursor 20:4-NAPE is mediated by TRPV1 receptors under inflammatory conditions. Front Mol Neurosci 2023; 16:1188503. [PMID: 37426071 PMCID: PMC10325575 DOI: 10.3389/fnmol.2023.1188503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 05/24/2023] [Indexed: 07/11/2023] Open
Abstract
Transient receptor potential ion channel, vanilloid subfamily, type 1 (TRPV1) cation channel, and cannabinoid receptor 1 (CB1) are essential in the modulation of nociceptive signaling in the spinal cord dorsal horn that underlies different pathological pain states. TRPV1 and CB1 receptors share the endogenous agonist anandamide (AEA), produced from N-arachidonoylphosphatidylethanolamine (20:4-NAPE). We investigated the effect of the anandamide precursor 20:4-NAPE on synaptic activity in naive and inflammatory conditions. Patch-clamp recordings of miniature excitatory postsynaptic currents (mEPSCs) from superficial dorsal horn neurons in rat acute spinal cord slices were used. Peripheral inflammation was induced by subcutaneous injection of carrageenan. Under naive conditions, mEPSCs frequency (0.96 ± 0.11 Hz) was significantly decreased after 20 μM 20:4-NAPE application (55.3 ± 7.4%). This 20:4-NAPE-induced inhibition was blocked by anandamide-synthesizing enzyme N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD) inhibitor LEI-401. In addition, the inhibition was prevented by the CB1 receptor antagonist PF 514273 (0.2 μM) but not by the TRPV1 receptor antagonist SB 366791 (10 μM). Under inflammatory conditions, 20:4-NAPE (20 μM) also exhibited a significant inhibitory effect (74.5 ± 8.9%) on the mEPSCs frequency that was prevented by the TRPV1 receptor antagonist SB 366791 but not by PF 514273 application. Our results show that 20:4-NAPE application has a significant modulatory effect on spinal cord nociceptive signaling that is mediated by both TRPV1 and CB1 presynaptic receptors, whereas peripheral inflammation changes the underlying mechanism. The switch between TRPV1 and CB1 receptor activation by the AEA precursor 20:4-NAPE during inflammation may play an important role in nociceptive processing, hence the development of pathological pain.
Collapse
Affiliation(s)
- Diana Spicarova
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia
| | - Vladimir Nerandzic
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia
| | - David Muzik
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia
| | - Monica Pontearso
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia
| | - Anirban Bhattacharyya
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia
| | - Istvan Nagy
- Section of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Imperial College London, Faculty of Medicine, Chelsea and Westminster Hospital, London, United Kingdom
- Department of Physiology, University of Debrecen, Debrecen, Hungary
| | - Jiri Palecek
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia
| |
Collapse
|
10
|
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] [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.
Collapse
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
| |
Collapse
|
11
|
Mackay JP, Smith-Dijak AI, Koch ET, Zhang P, Fung E, Nassrallah WB, Buren C, Schmidt M, Hayden MR, Raymond LA. Axonal ER Ca 2+ Release Selectively Enhances Activity-Independent Glutamate Release in a Huntington Disease Model. J Neurosci 2023; 43:3743-3763. [PMID: 36944490 PMCID: PMC10198457 DOI: 10.1523/jneurosci.1593-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 03/08/2023] [Accepted: 03/15/2023] [Indexed: 03/23/2023] Open
Abstract
Action potential (AP)-independent (miniature) neurotransmission occurs at all chemical synapses but remains poorly understood, particularly in pathologic contexts. Axonal endoplasmic reticulum (ER) Ca2+ stores are thought to influence miniature neurotransmission, and aberrant ER Ca2+ handling is implicated in progression of Huntington disease (HD). Here, we report elevated mEPSC frequencies in recordings from YAC128 mouse (HD-model) neurons (from cortical cultures and striatum-containing brain slices, both from male and female animals). Pharmacological experiments suggest that this is mediated indirectly by enhanced tonic ER Ca2+ release. Calcium imaging, using an axon-localized sensor, revealed slow AP-independent ER Ca2+ release waves in both YAC128 and WT cultures. These Ca2+ waves occurred at similar frequencies in both genotypes but spread less extensively and were of lower amplitude in YAC128 axons, consistent with axonal ER Ca2+ store depletion. Surprisingly, basal cytosolic Ca2+ levels were lower in YAC128 boutons and YAC128 mEPSCs were less sensitive to intracellular Ca2+ chelation. Together, these data suggest that elevated miniature glutamate release in YAC128 cultures is associated with axonal ER Ca2+ depletion but not directly mediated by ER Ca2+ release into the cytoplasm. In contrast to increased mEPSC frequencies, cultured YAC128 cortical neurons showed less frequent AP-dependent (spontaneous) Ca2+ events in soma and axons, although evoked glutamate release detected by an intensity-based glutamate-sensing fluorescence reporter in brain slices was similar between genotypes. Our results indicate that axonal ER dysfunction selectively elevates miniature glutamate release from cortical terminals in HD. This, together with reduced spontaneous cortical neuron firing, may cause a shift from activity-dependent to -independent glutamate release in HD, with potential implications for fidelity and plasticity of cortical excitatory signaling.SIGNIFICANCE STATEMENT Miniature neurotransmitter release persists at all chemical neuronal synapses in the absence of action potential firing but remains poorly understood, particularly in disease states. We show enhanced miniature glutamate release from cortical neurons in the YAC128 mouse Huntington disease model. This effect is mediated by axonal ER Ca2+ store depletion, but is not obviously due to elevated ER-to-cytosol Ca2+ release. Conversely, YAC128 cortical pyramidal neurons fired fewer action potentials and evoked cortical glutamate release was similar between WT an YAC128 preparations, indicating axonal ER depletion selectively enhances miniature glutamate release in YAC128 mice. These results extend our understanding of action potential independent neurotransmission and highlight a potential involvement of elevated miniature glutamate release in Huntington disease pathology.
Collapse
Affiliation(s)
- James P Mackay
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health
| | - Amy I Smith-Dijak
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health
- Graduate Program in Neuroscience
| | - Ellen T Koch
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health
- Graduate Program in Neuroscience
| | - Peng Zhang
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health
- Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
| | - Evan Fung
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health
| | - Wissam B Nassrallah
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health
- MD/PhD Program
| | - Caodu Buren
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health
- Graduate Program in Neuroscience
| | - Mandi Schmidt
- Graduate Program in Neuroscience
- Centre for Molecular Medicine and Therapeutics, British Columbia Children's Hospital Research Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Michael R Hayden
- Centre for Molecular Medicine and Therapeutics, British Columbia Children's Hospital Research Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Lynn A Raymond
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health
| |
Collapse
|
12
|
Le Guellec B, Gomez LC, Malagon G, Collin T, Marty A. Depolarization-induced bursts of miniature synaptic currents in individual synapses of developing cerebellum. J Gen Physiol 2023; 155:e202213212. [PMID: 37010482 PMCID: PMC10072220 DOI: 10.1085/jgp.202213212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 12/07/2022] [Accepted: 03/13/2023] [Indexed: 04/04/2023] Open
Abstract
In central synapses, spontaneous transmitter release observed in the absence of action potential firing is often considered as a random process lacking time or space specificity. However, when studying miniature glutamatergic currents at cerebellar synapses between parallel fibers and molecular layer interneurons, we found that these currents were sometimes organized in bursts of events occurring at high frequency (about 30 Hz). Bursts displayed homogeneous quantal size amplitudes. Furthermore, in the presence of the desensitization inhibitor cyclothiazide, successive events within a burst displayed quantal amplitude occlusion. Based on these findings, we conclude that bursts originate in individual synapses. Bursts were enhanced by increasing either the external potassium concentration or the external calcium concentration, and they were strongly inhibited when blocking voltage-gated calcium channels by cadmium. Bursts were prevalent in elevated potassium concentration during the formation of the molecular layer but were infrequent later in development. Since postsynaptic AMPA receptors are largely calcium permeant in developing parallel fiber-interneuron synapses, we propose that bursts involve presynaptic calcium transients implicating presynaptic voltage-gated calcium channels, together with postsynaptic calcium transients implicating postsynaptic AMPA receptors. These simultaneous pre- and postsynaptic calcium transients may contribute to the formation and/or stabilization of synaptic connections.
Collapse
Affiliation(s)
- Bastien Le Guellec
- Université Paris Cité, Saints Pères Paris Institute for the Neurosciences, CNRS, Paris, France
| | - Laura C. Gomez
- Université Paris Cité, Saints Pères Paris Institute for the Neurosciences, CNRS, Paris, France
| | - Gerardo Malagon
- Université Paris Cité, Saints Pères Paris Institute for the Neurosciences, CNRS, Paris, France
| | - Thibault Collin
- Université Paris Cité, Saints Pères Paris Institute for the Neurosciences, CNRS, Paris, France
| | - Alain Marty
- Université Paris Cité, Saints Pères Paris Institute for the Neurosciences, CNRS, Paris, France
| |
Collapse
|
13
|
Cook DC, Ryan TA. GABA BR silencing of nerve terminals. eLife 2023; 12:e83530. [PMID: 37014052 PMCID: PMC10115440 DOI: 10.7554/elife.83530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Accepted: 04/03/2023] [Indexed: 04/05/2023] Open
Abstract
Control of neurotransmission efficacy is central to theories of how the brain computes and stores information. Presynaptic G-protein coupled receptors (GPCRs) are critical in this problem as they locally influence synaptic strength and can operate on a wide range of time scales. Among the mechanisms by which GPCRs impact neurotransmission is by inhibiting voltage-gated calcium (Ca2+) influx in the active zone. Here, using quantitative analysis of both single bouton Ca2+ influx and exocytosis, we uncovered an unexpected non-linear relationship between the magnitude of action potential driven Ca2+ influx and the concentration of external Ca2+ ([Ca2+]e). We find that this unexpected relationship is leveraged by GPCR signaling when operating at the nominal physiological set point for [Ca2+]e, 1.2 mM, to achieve complete silencing of nerve terminals. These data imply that the information throughput in neural circuits can be readily modulated in an all-or-none fashion at the single synapse level when operating at the physiological set point.
Collapse
Affiliation(s)
- Daniel C Cook
- Department of Anesthesiology, Weill Cornell Medical CollegeNew YorkUnited States
| | - Timothy A Ryan
- Department of Anesthesiology, Weill Cornell Medical CollegeNew YorkUnited States
- Department of Biochemistry, Weill Cornell Medical CollegeNew YorkUnited States
| |
Collapse
|
14
|
Leyva-Leyva M, Sandoval A, Morales-Lázaro SL, Corzo-López A, Felix R, González-Ramírez R. Identification of Dp140 and α1-syntrophin as novel molecular interactors of the neuronal Ca V2.1 channel. Pflugers Arch 2023; 475:595-606. [PMID: 36964781 DOI: 10.1007/s00424-023-02803-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 02/21/2023] [Accepted: 03/06/2023] [Indexed: 03/26/2023]
Abstract
The primary function of dystrophin is to form a link between the cytoskeleton and the extracellular matrix. In addition to this crucial structural function, dystrophin also plays an essential role in clustering and organizing several signaling proteins, including ion channels. Proteomic analysis of the whole rodent brain has stressed the role of some components of the dystrophin-associated glycoprotein complex (DGC) as potential interacting proteins of the voltage-gated Ca2+ channels of the CaV2 subfamily. The interaction of CaV2 with signaling and scaffolding proteins, such as the DGC components, may influence their function, stability, and location in neurons. This work aims to study the interaction between dystrophin and CaV2.1. Our immunoprecipitation data showed the presence of a complex formed by CaV2.1, CaVα2δ-1, CaVβ4e, Dp140, and α1-syntrophin in the brain. Furthermore, proximity ligation assays (PLA) showed that CaV2.1 and CaVα2δ-1 interact with dystrophin in the hippocampus and cerebellum. Notably, Dp140 and α1-syntrophin increase CaV2.1 protein stability, half-life, permanence in the plasma membrane, and current density through recombinant CaV2.1 channels. Therefore, we have identified the Dp140 and α1-syntrophin as novel interaction partners of CaV2.1 channels in the mammalian brain. Consistent with previous findings, our work provides evidence of the role of DGC in anchoring and clustering CaV channels in a macromolecular complex.
Collapse
Affiliation(s)
- Margarita Leyva-Leyva
- Department of Molecular Biology and Histocompatibility, "Dr. Manuel Gea González" General Hospital, Mexico City, Mexico
- Posgrado en Ciencias Biológicas, Unidad de Posgrado, Universidad Nacional Autónoma de México (UNAM), Ciudad de Mexico, México
| | - Alejandro Sandoval
- School of Medicine FES Iztacala, National Autonomous University of México (UNAM), Tlalnepantla, Mexico
| | - Sara Luz Morales-Lázaro
- Departamento de Neurociencia Cognitiva, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de Mexico, México
| | - Alejandra Corzo-López
- Department of Cell Biology, Centre for Research and Advanced Studies (Cinvestav), Mexico City, Mexico
| | - Ricardo Felix
- Department of Cell Biology, Centre for Research and Advanced Studies (Cinvestav), Mexico City, Mexico.
| | - Ricardo González-Ramírez
- Department of Molecular Biology and Histocompatibility, "Dr. Manuel Gea González" General Hospital, Mexico City, Mexico.
| |
Collapse
|
15
|
Grasskamp AT, Jusyte M, McCarthy AW, Götz TWB, Ditlevsen S, Walter AM. Spontaneous neurotransmission at evocable synapses predicts their responsiveness to action potentials. Front Cell Neurosci 2023; 17:1129417. [PMID: 36970416 PMCID: PMC10030884 DOI: 10.3389/fncel.2023.1129417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 02/16/2023] [Indexed: 03/29/2023] Open
Abstract
Synaptic transmission relies on presynaptic neurotransmitter (NT) release from synaptic vesicles (SVs) and on NT detection by postsynaptic receptors. Transmission exists in two principal modes: action-potential (AP) evoked and AP-independent, "spontaneous" transmission. AP-evoked neurotransmission is considered the primary mode of inter-neuronal communication, whereas spontaneous transmission is required for neuronal development, homeostasis, and plasticity. While some synapses appear dedicated to spontaneous transmission only, all AP-responsive synapses also engage spontaneously, but whether this encodes functional information regarding their excitability is unknown. Here we report on functional interdependence of both transmission modes at individual synaptic contacts of Drosophila larval neuromuscular junctions (NMJs) which were identified by the presynaptic scaffolding protein Bruchpilot (BRP) and whose activities were quantified using the genetically encoded Ca2+ indicator GCaMP. Consistent with the role of BRP in organizing the AP-dependent release machinery (voltage-dependent Ca2+ channels and SV fusion machinery), most active BRP-positive synapses (>85%) responded to APs. At these synapses, the level of spontaneous activity was a predictor for their responsiveness to AP-stimulation. AP-stimulation resulted in cross-depletion of spontaneous activity and both transmission modes were affected by the non-specific Ca2+ channel blocker cadmium and engaged overlapping postsynaptic receptors. Thus, by using overlapping machinery, spontaneous transmission is a continuous, stimulus independent predictor for the AP-responsiveness of individual synapses.
Collapse
Affiliation(s)
| | - Meida Jusyte
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
- Einstein Center for Neurosciences, Charité–Universitätsmedizin Berlin, Berlin, Germany
| | | | - Torsten W. B. Götz
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Susanne Ditlevsen
- Department of Mathematical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Alexander M. Walter
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
- Einstein Center for Neurosciences, Charité–Universitätsmedizin Berlin, Berlin, Germany
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
16
|
Dolphin AC. Distinct pools of synaptic vesicles are released by different calcium channels. Cell Calcium 2023; 112:102729. [PMID: 37011495 DOI: 10.1016/j.ceca.2023.102729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 03/27/2023] [Indexed: 03/30/2023]
Abstract
Mueller et al. [1] uncover distinct roles for CaV1 and CaV2 channels in neurotransmitter release at the C. elegans neuromuscular junction. Although nanodomain coupling occurs via clustered CaV2 channels, evidence is also presented that release of a separate vesicular pool is mediated by more peripheral, dispersed CaV1 channels, requiring obligatory coupling with RYR to amplify the Ca2+ signal.
Collapse
Affiliation(s)
- Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.
| |
Collapse
|
17
|
Pilch KS, Ramgoolam KH, Dolphin AC. Involvement of Ca V 2.2 channels and α 2 δ-1 in homeostatic synaptic plasticity in cultured hippocampal neurons. J Physiol 2022; 600:5333-5351. [PMID: 36377048 PMCID: PMC10107484 DOI: 10.1113/jp283600] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 11/08/2022] [Indexed: 11/16/2022] Open
Abstract
In the mammalian brain, presynaptic CaV 2 channels play a pivotal role in synaptic transmission by mediating fast neurotransmitter exocytosis via influx of Ca2+ into the active zone of presynaptic terminals. However, the distribution and modulation of CaV 2.2 channels at plastic hippocampal synapses remains to be elucidated. Here, we assess CaV 2.2 channels during homeostatic synaptic plasticity, a compensatory form of homeostatic control preventing excessive or insufficient neuronal activity during which extensive active zone remodelling has been described. We show that chronic silencing of neuronal activity in mature hippocampal cultures resulted in elevated presynaptic Ca2+ transients, mediated by increased levels of CaV 2.2 channels at the presynaptic site. This work focused further on the role of α2 δ-1 subunits, important regulators of synaptic transmission and CaV 2.2 channel abundance at the presynaptic membrane. We found that α2 δ-1 overexpression reduces the contribution of CaV 2.2 channels to total Ca2+ flux without altering the amplitude of the Ca2+ transients. Levels of endogenous α2 δ-1 decreased during homeostatic synaptic plasticity, whereas the overexpression of α2 δ-1 prevented homeostatic synaptic plasticity in hippocampal neurons. Together, this study reveals a key role for CaV 2.2 channels and novel roles for α2 δ-1 during synaptic plastic adaptation. KEY POINTS: The roles of CaV 2.2 channels and α2 δ-1 in homeostatic synaptic plasticity in hippocampal neurons in culture were examined. Chronic silencing of neuronal activity resulted in elevated presynaptic Ca2+ transients, mediated by increased levels of CaV 2.2 channels at presynaptic sites. The level of endogenous α2 δ-1 decreased during homeostatic synaptic plasticity, whereas overexpression of α2 δ-1 prevented homeostatic synaptic plasticity in hippocampal neurons. Together, this study reveals a key role for CaV 2.2 channels and novel roles for α2 δ-1 during synaptic plastic adaptation.
Collapse
Affiliation(s)
- Kjara S. Pilch
- Department of NeurosciencePhysiology and PharmacologyUniversity College LondonLondonUK
| | - Krishma H. Ramgoolam
- Department of NeurosciencePhysiology and PharmacologyUniversity College LondonLondonUK
| | - Annette C. Dolphin
- Department of NeurosciencePhysiology and PharmacologyUniversity College LondonLondonUK
| |
Collapse
|
18
|
Mancini M, Patel JC, Affinati AH, Witkovsky P, Rice ME. Leptin Promotes Striatal Dopamine Release via Cholinergic Interneurons and Regionally Distinct Signaling Pathways. J Neurosci 2022; 42:6668-6679. [PMID: 35906070 PMCID: PMC9436012 DOI: 10.1523/jneurosci.0238-22.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 07/06/2022] [Accepted: 07/14/2022] [Indexed: 11/21/2022] Open
Abstract
Dopamine (DA) is a critical regulator of striatal network activity and is essential for motor activation and reward-associated behaviors. Previous work has shown that DA is influenced by the reward value of food, as well as by hormonal factors that reguate food intake and energy expenditure. Changes in striatal DA signaling also have been linked to aberrant eating patterns. Here we test the effect of leptin, an adipocyte-derived hormone involved in feeding and energy homeostasis regulation, on striatal DA release and uptake. Immunohistochemical evaluation identified leptin receptor (LepR) expression throughout mouse striatum, including on striatal cholinergic interneurons (ChIs) and their extensive processes. Using fast-scan cyclic voltammetry (FSCV), we found that leptin causes a concentration-dependent increase in evoked extra-cellular DA concentration ([DA]o) in dorsal striatum (dStr) and nucleus accumbens (NAc) core and shell in male mouse striatal slices, and also an increase in the rate of DA uptake. Further, we found that leptin increases ChI excitability, and that the enhancing effect of leptin on evoked [DA]o is lost when nicotinic acetylcholine (ACh) receptors are antagonized or when examined in striatal slices from mice lacking ACh synthesis. Evaluation of signaling pathways underlying leptin's action revealed a requirement for intracellular Ca2+, and the involvement of different downstream pathways in dStr and NAc core versus NAc shell. These results provide the first evidence for dynamic regulation of DA release and uptake by leptin within brain motor and reward pathways, and highlight the involvement of ChIs in this process.SIGNIFICANCE STATEMENT Given the importance of striatal dopamine (DA) in reward, motivation, motor behavior and food intake, identifying the actions of metabolic hormones on DA release in striatal subregions should provide new insight into factors that influence DA-dependent motivated behaviors. We find that one of these hormones, leptin, boosts striatal DA release through a process involving striatal cholinergic interneurons (ChIs) and nicotinic acetylcholine (ACh) receptors. Moreover, we find that the intracellular cascades downstream from leptin receptor (LepR) activation that lead to enhanced DA release differ among striatal subregions. Thus, we not only show that leptin regulates DA release, but also identify characteristics of this process that could be harnessed to alter pathologic eating behaviors.
Collapse
Affiliation(s)
- Maria Mancini
- Department of Neuroscience and Physiology, New York University Grossman School of Medicine, New York, New York 10016
- Neuroscience Institute, New York University Grossman School of Medicine, New York, New York 10016
| | - Jyoti C Patel
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, New York 10016
| | - Alison H Affinati
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109
| | - Paul Witkovsky
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, New York 10016
| | - Margaret E Rice
- Department of Neuroscience and Physiology, New York University Grossman School of Medicine, New York, New York 10016
- Neuroscience Institute, New York University Grossman School of Medicine, New York, New York 10016
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, New York 10016
| |
Collapse
|
19
|
Adeoye T, Shah SI, Demuro A, Rabson DA, Ullah G. Upregulated Ca 2+ Release from the Endoplasmic Reticulum Leads to Impaired Presynaptic Function in Familial Alzheimer's Disease. Cells 2022; 11:2167. [PMID: 35883609 PMCID: PMC9315668 DOI: 10.3390/cells11142167] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 06/28/2022] [Accepted: 07/02/2022] [Indexed: 12/10/2022] Open
Abstract
Neurotransmitter release from presynaptic terminals is primarily regulated by rapid Ca2+ influx through membrane-resident voltage-gated Ca2+ channels (VGCCs). Moreover, accumulating evidence indicates that the endoplasmic reticulum (ER) is extensively present in axonal terminals of neurons and plays a modulatory role in synaptic transmission by regulating Ca2+ levels. Familial Alzheimer's disease (FAD) is marked by enhanced Ca2+ release from the ER and downregulation of Ca2+ buffering proteins. However, the precise consequence of impaired Ca2+ signaling within the vicinity of VGCCs (active zone (AZ)) on exocytosis is poorly understood. Here, we perform in silico experiments of intracellular Ca2+ signaling and exocytosis in a detailed biophysical model of hippocampal synapses to investigate the effect of aberrant Ca2+ signaling on neurotransmitter release in FAD. Our model predicts that enhanced Ca2+ release from the ER increases the probability of neurotransmitter release in FAD. Moreover, over very short timescales (30-60 ms), the model exhibits activity-dependent and enhanced short-term plasticity in FAD, indicating neuronal hyperactivity-a hallmark of the disease. Similar to previous observations in AD animal models, our model reveals that during prolonged stimulation (~450 ms), pathological Ca2+ signaling increases depression and desynchronization with stimulus, causing affected synapses to operate unreliably. Overall, our work provides direct evidence in support of a crucial role played by altered Ca2+ homeostasis mediated by intracellular stores in FAD.
Collapse
Affiliation(s)
- Temitope Adeoye
- Department of Physics, University of South Florida, Tampa, FL 33620, USA; (T.A.); (S.I.S.); (D.A.R.)
| | - Syed I. Shah
- Department of Physics, University of South Florida, Tampa, FL 33620, USA; (T.A.); (S.I.S.); (D.A.R.)
| | - Angelo Demuro
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA;
| | - David A. Rabson
- Department of Physics, University of South Florida, Tampa, FL 33620, USA; (T.A.); (S.I.S.); (D.A.R.)
| | - Ghanim Ullah
- Department of Physics, University of South Florida, Tampa, FL 33620, USA; (T.A.); (S.I.S.); (D.A.R.)
| |
Collapse
|
20
|
Mendonça PRF, Tagliatti E, Langley H, Kotzadimitriou D, Zamora-Chimal CG, Timofeeva Y, Volynski KE. Asynchronous glutamate release is enhanced in low release efficacy synapses and dispersed across the active zone. Nat Commun 2022; 13:3497. [PMID: 35715404 PMCID: PMC9206079 DOI: 10.1038/s41467-022-31070-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 05/31/2022] [Indexed: 11/09/2022] Open
Abstract
The balance between fast synchronous and delayed asynchronous release of neurotransmitters has a major role in defining computational properties of neuronal synapses and regulation of neuronal network activity. However, how it is tuned at the single synapse level remains poorly understood. Here, using the fluorescent glutamate sensor SF-iGluSnFR, we image quantal vesicular release in tens to hundreds of individual synaptic outputs from single pyramidal cells with 4 millisecond temporal and 75 nm spatial resolution. We find that the ratio between synchronous and asynchronous synaptic vesicle exocytosis varies extensively among synapses supplied by the same axon, and that the synchronicity of release is reduced at low release probability synapses. We further demonstrate that asynchronous exocytosis sites are more widely distributed within the release area than synchronous sites. Together, our results reveal a universal relationship between the two major functional properties of synapses - the timing and the overall efficacy of neurotransmitter release.
Collapse
Affiliation(s)
- Philipe R F Mendonça
- University College London Institute of Neurology, London, UK. .,Department of Physiology and Biophysics, Federal University of Minas Gerais, Gerais, Brazil.
| | - Erica Tagliatti
- University College London Institute of Neurology, London, UK
| | - Helen Langley
- University College London Institute of Neurology, London, UK
| | | | | | - Yulia Timofeeva
- University College London Institute of Neurology, London, UK. .,Department of Computer Science, University of Warwick, Coventry, UK.
| | | |
Collapse
|
21
|
Lei L, Zhu B, Qiao K, Zhou Y, Chen X, Men J, Yang L, Wang Q, Han J, Zhou B. New evidence for neurobehavioral toxicity of deltamethrin at environmentally relevant levels in zebrafish. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 822:153623. [PMID: 35124052 DOI: 10.1016/j.scitotenv.2022.153623] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/28/2022] [Accepted: 01/29/2022] [Indexed: 06/14/2023]
Abstract
Deltamethrin, a widely used type II pyrethroid insecticide, was reported with neurotoxicity to aquatic organisms, such as fish. However, the effects and potential mechanisms on the central nervous system remain largely unknown, especially under environmental concentrations. Therefore, we exposed adult female zebrafish to environmentally relevant levels of deltamethrin (30, 100, and 333 ng/L) for 21 days to assess neurobehavioral changes related to the central nervous system and explore the modes of action. Behavioral assays revealed significant increases in the swimming speeds, residence time near other fish and the shoaling cohesion in exposed fish. Transcriptomic results enriched the disrupted neural functions involving the glutamatergic and dopaminergic synapses in the brain. The qRT-PCR confirmed the upregulation of the factors for promoting the glutamate release. The measurement of neurotransmitters showed significantly increased content of the excitatory neurotransmitter glutamate in the brain. Taken together, deltamethrin exposure increased the glutamate level and promoted the release of such an excitatory neurotransmitter between the glutamatergic synapses in the brain, which eventually led to hyperactivity of social behaviors in adult zebrafish.
Collapse
Affiliation(s)
- Lei Lei
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Biran Zhu
- School of Basic Medical Sciences, Hubei University of Chinese Medicine, Wuhan 430065, China
| | - Kun Qiao
- Institute of Pesticide and Environmental Toxicology, Zhejiang University, Hangzhou 310058, China
| | - Yuxi Zhou
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiangping Chen
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Jun Men
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Lihua Yang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Qidong Wang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Jian Han
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
| | - Bingsheng Zhou
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| |
Collapse
|
22
|
Egashira Y, Kumade A, Ojida A, Ono F. Spontaneously Recycling Synaptic Vesicles Constitute Readily Releasable Vesicles in Intact Neuromuscular Synapses. J Neurosci 2022; 42:3523-3536. [PMID: 35332083 PMCID: PMC9053852 DOI: 10.1523/jneurosci.2005-21.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 03/08/2022] [Accepted: 03/10/2022] [Indexed: 12/14/2022] Open
Abstract
Emerging evidence shows that spontaneous synaptic transmission plays crucial roles on neuronal functions through presynaptic molecular mechanisms distinct from that of action potential (AP)-evoked transmission. However, whether the synaptic vesicle (SV) population undergoing the two forms of transmission is segregated remains controversial due in part to the conflicting results observed in cultured neurons. Here we address this issue in intact neuromuscular synapses using transgenic zebrafish larvae expressing two different indicators targeted in the SVs: a pH-sensitive fluorescent protein, pHluorin, and a tag protein, HaloTag. By establishing a quantitative measure of recycled SV fractions, we found that ∼85% of SVs were mobilized by high-frequency AP firings. In contrast, spontaneously recycling SVs were mobilized only from <8% of SVs with a time constant of 45 min at 25°C, although prolonged AP inhibition mobilized an additional population with a delayed onset. The mobilization of the early-onset population was less temperature-sensitive and resistant to tetanus toxin, whereas that of the late-onset population was more sensitive to temperature and was inhibited by tetanus toxin, indicating that prolonged AP inhibition activated a distinct molecular machinery for spontaneous SV fusion. Therefore, the early-onset population limited to <8% was likely the only source of spontaneous release that occurred physiologically. We further showed that this limited population was independent from those reluctant to fuse during AP firing and was used in both the hypertonic stimulation and the immediate phase of AP-evoked releases, thereby matching the characteristics of the readily releasable pool.SIGNIFICANCE STATEMENT Synaptic vesicles (SVs) are divided into functionally distinct pools depending on how they respond to action potential (AP) firing. The origin of SVs used for spontaneous fusion remains enigmatic despite intensive studies in cultured preparations. We addressed this question in intact neuromuscular synapses and provided two findings. First, prolonged AP inhibition activated a distinct population of fusion, which needs to be distinguished from genuine spontaneous fusion arising from a highly limited fraction. Second, the limited fraction observed early in the AP inhibition period exhibited the characteristics of readily releasable pool in the subsequent round of stimulation. Our study revealed that the origin of spontaneous SV fusion is restricted to the readily releasable pool among the SV pools involved in AP-evoked fusion.
Collapse
Affiliation(s)
- Yoshihiro Egashira
- Department of Physiology, Osaka Medical and Pharmaceutical University, Takatsuki, 569-8686, Japan
| | - Ayane Kumade
- Graduate School of Pharmaceutical Science, Kyushu University, Fukuoka, 812-8582, Japan
| | - Akio Ojida
- Graduate School of Pharmaceutical Science, Kyushu University, Fukuoka, 812-8582, Japan
| | - Fumihito Ono
- Department of Physiology, Osaka Medical and Pharmaceutical University, Takatsuki, 569-8686, Japan
| |
Collapse
|
23
|
Alten B, Guzikowski NJ, Zurawski Z, Hamm HE, Kavalali ET. Presynaptic mechanisms underlying GABA B-receptor-mediated inhibition of spontaneous neurotransmitter release. Cell Rep 2022; 38:110255. [PMID: 35045279 PMCID: PMC8793855 DOI: 10.1016/j.celrep.2021.110255] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/15/2021] [Accepted: 12/21/2021] [Indexed: 01/08/2023] Open
Abstract
Inhibition of neurotransmitter release by neurotransmitter substances constitutes a fundamental means of neuromodulation. In contrast to well-delineated mechanisms that underlie inhibition of evoked release via suppression of voltage-gated Ca2+ channels, processes that underlie neuromodulatory inhibition of spontaneous release remain unclear. Here, we interrogated inhibition of spontaneous glutamate and GABA release by presynaptic metabotropic GABAB receptors. Our findings show that this inhibition relies on Gβγ subunit action at the membrane, and it is largely independent of presynaptic Ca2+ signaling for both forms of release. In the case of spontaneous glutamate release, inhibition requires Gβγ interaction with the C terminus of the key fusion machinery component SNAP25, and it is modulated by synaptotagmin-1. Inhibition of spontaneous GABA release, on the other hand, is independent of these pathways and likely requires alternative Gβγ targets at the presynaptic terminal.
Collapse
Affiliation(s)
- Baris Alten
- Department of Pharmacology, Vanderbilt University, 7130A MRB III 465 21st Avenue South, Nashville, TN 37240-7933, USA,Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37240-7933, USA
| | - Natalie J. Guzikowski
- Department of Pharmacology, Vanderbilt University, 7130A MRB III 465 21st Avenue South, Nashville, TN 37240-7933, USA,Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37240-7933, USA
| | - Zack Zurawski
- Department of Pharmacology, Vanderbilt University, 7130A MRB III 465 21st Avenue South, Nashville, TN 37240-7933, USA
| | - Heidi E. Hamm
- Department of Pharmacology, Vanderbilt University, 7130A MRB III 465 21st Avenue South, Nashville, TN 37240-7933, USA
| | - Ege T. Kavalali
- Department of Pharmacology, Vanderbilt University, 7130A MRB III 465 21st Avenue South, Nashville, TN 37240-7933, USA,Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37240-7933, USA,Lead contact,Correspondence:
| |
Collapse
|
24
|
Vasu SO, Kaphzan H. Calcium channels control tDCS-induced spontaneous vesicle release from axon terminals. Brain Stimul 2022; 15:270-282. [DOI: 10.1016/j.brs.2022.01.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 01/06/2022] [Accepted: 01/06/2022] [Indexed: 12/29/2022] Open
|
25
|
Lee BJ, Yang CH, Lee SY, Lee SH, Kim Y, Ho WK. Voltage-gated calcium channels contribute to spontaneous glutamate release directly via nanodomain coupling or indirectly via calmodulin. Prog Neurobiol 2021; 208:102182. [PMID: 34695543 DOI: 10.1016/j.pneurobio.2021.102182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/05/2021] [Accepted: 10/18/2021] [Indexed: 11/19/2022]
Abstract
Neurotransmitter release occurs either synchronously with action potentials (evoked release) or spontaneously (spontaneous release). Whether the molecular mechanisms underlying evoked and spontaneous release are identical, especially whether voltage-gated calcium channels (VGCCs) can trigger spontaneous events, is still a matter of debate in glutamatergic synapses. To elucidate this issue, we characterized the VGCC dependence of miniature excitatory postsynaptic currents (mEPSCs) in various synapses with different coupling distances between VGCCs and synaptic vesicles, known as a critical factor in evoked release. We found that most of the extracellular calcium-dependent mEPSCs were attributable to VGCCs in cultured autaptic hippocampal neurons and the mature calyx of Held where VGCCs and vesicles were tightly coupled. Among loosely coupled synapses, mEPSCs were not VGCC-dependent at immature calyx of Held and CA1 pyramidal neuron synapses, whereas VGCCs contribution was significant at CA3 pyramidal neuron synapses. Interestingly, the contribution of VGCCs to spontaneous glutamate release in CA3 pyramidal neurons was abolished by a calmodulin antagonist, calmidazolium. These data suggest that coupling distance between VGCCs and vesicles determines VGCC dependence of spontaneous release at tightly coupled synapses, yet VGCC contribution can be achieved indirectly at loosely coupled synapses.
Collapse
Affiliation(s)
- Byoung Ju Lee
- Department of Biomedical Sciences, Seoul National University College of Natural Science, Seoul, Republic of Korea; Department of Physiology, Seoul National University College of Natural Science, Seoul, Republic of Korea
| | - Che Ho Yang
- Department of Biomedical Sciences, Seoul National University College of Natural Science, Seoul, Republic of Korea; Department of Physiology, Seoul National University College of Natural Science, Seoul, Republic of Korea; Department of Brain and Cognitive Science, Seoul National University College of Natural Science, Seoul, Republic of Korea
| | - Seung Yeon Lee
- Department of Biomedical Sciences, Seoul National University College of Natural Science, Seoul, Republic of Korea; Department of Physiology, Seoul National University College of Natural Science, Seoul, Republic of Korea
| | - Suk-Ho Lee
- Department of Biomedical Sciences, Seoul National University College of Natural Science, Seoul, Republic of Korea; Department of Physiology, Seoul National University College of Natural Science, Seoul, Republic of Korea; Neuroscience Research Institute, Seoul National University College of Medicine, Republic of Korea; Department of Brain and Cognitive Science, Seoul National University College of Natural Science, Seoul, Republic of Korea
| | - Yujin Kim
- Department of Physiology, Seoul National University College of Natural Science, Seoul, Republic of Korea; Neuroscience Research Institute, Seoul National University College of Medicine, Republic of Korea; Department of Brain and Cognitive Science, Seoul National University College of Natural Science, Seoul, Republic of Korea.
| | - Won-Kyung Ho
- Department of Biomedical Sciences, Seoul National University College of Natural Science, Seoul, Republic of Korea; Department of Physiology, Seoul National University College of Natural Science, Seoul, Republic of Korea; Neuroscience Research Institute, Seoul National University College of Medicine, Republic of Korea; Department of Brain and Cognitive Science, Seoul National University College of Natural Science, Seoul, Republic of Korea.
| |
Collapse
|
26
|
Satake SI, Konishi S. Topographical distance between presynaptic Ca 2+ channels and exocytotic Ca 2+ sensors contributes to differential facilitatory actions of roscovitine on neurotransmitter release at cerebellar glutamatergic and GABAergic synapses. Eur J Neurosci 2021; 54:7048-7062. [PMID: 34622493 DOI: 10.1111/ejn.15487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 09/27/2021] [Accepted: 09/29/2021] [Indexed: 11/29/2022]
Abstract
Calcium influx into presynaptic terminals through voltage-gated Ca2+ channels triggers univesicular or multivesicular release of neurotransmitters depending on the characteristics of the release machinery. However, the mechanisms underlying multivesicular release (MVR) and its regulation remain unclear. Previous studies showed that in rat cerebellum, the cyclin-dependent kinase inhibitor roscovitine profoundly increases excitatory postsynaptic current (EPSC) amplitudes at granule cell (GC)-Purkinje cell (PC) synapses by enhancing the MVR of glutamate. This compound can also moderately augment the amplitude and prolong the decay time of inhibitory postsynaptic currents (IPSCs) at molecular layer interneuron (MLI)-PC synapses via MVR enhancement and GABA spillover, thus allowing for persistent activation of perisynaptic GABA receptors. The enhanced MVR may depend on the driving force for Cav 2.1 channel-mediated Ca2+ influx. To determine whether the distinct spatiotemporal dynamics of presynaptic Ca2+ influence MVR, we compared the effects of slow and fast Ca2+ chelators, that is, EGTA and BAPTA, respectively, on roscovitine-induced actions at GC-PC and MLI-PC synapses. Membrane-permeable EGTA-AM decreased GC-PC EPSC and MLI-PC IPSC amplitudes to a similar extent but suppressed the roscovitine-induced enhancement of EPSCs. In contrast, BAPTA-AM attenuated the effects of roscovitine on IPSCs. These results suggest that roscovitine augmented glutamate release by activating the release machinery located distally from the Cav 2.1 channel clusters, while it enhanced GABA release in a manner less dependent on those at distal sites. Therefore, the spatial relationships among Ca2+ channels, buffers, and sensors are critical determinants of the differential facilitatory actions of roscovitine on glutamatergic and GABAergic synapses in the cerebellar cortex.
Collapse
Affiliation(s)
- Shin' Ichiro Satake
- Brain Research Support Center, National Institute for Physiological Sciences (NIPS), Okazaki, Japan.,School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Japan
| | - Shiro Konishi
- Department of Neurophysiology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki, Japan
| |
Collapse
|
27
|
Feng Z, Glebov OO. Synaptic NMDA receptor signalling controls R-type calcium channel recruitment. Eur J Neurosci 2021; 54:4133-4140. [PMID: 33901331 DOI: 10.1111/ejn.15250] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 04/09/2021] [Indexed: 11/29/2022]
Abstract
Regulation of extracellular Ca2+ influx by neuronal activity is a key mechanism underlying synaptic plasticity. At the neuronal synapse, activity-dependent Ca2+ entry involves N-methyl-D-aspartate receptors (NMDARs) and voltage-gated calcium channels (VGCCs); the relationship between NMDARs and VGCCs, however, is poorly understood. Here, we report that neuronal activity rapidly (1h) regulates recruitment of R-type VGCCs in hippocampal neurons through synaptic NMDAR signalling. This finding reveals a link between two key neuronal signalling pathways, suggesting a feedback mode for regulation of synaptic Ca2+ signalling.
Collapse
Affiliation(s)
- Zhendong Feng
- Institute of Neuroregeneration and Neurorehabilitation, Qingdao University, Qingdao, China
| | - Oleg O Glebov
- Institute of Neuroregeneration and Neurorehabilitation, Qingdao University, Qingdao, China
- Department of Old Age Psychiatry, The Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| |
Collapse
|
28
|
Bourgeois-Jaarsma Q, Miaja Hernandez P, Groffen AJ. Ca 2+ sensor proteins in spontaneous release and synaptic plasticity: Limited contribution of Doc2c, rabphilin-3a and synaptotagmin 7 in hippocampal glutamatergic neurons. Mol Cell Neurosci 2021; 112:103613. [PMID: 33753311 DOI: 10.1016/j.mcn.2021.103613] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 03/09/2021] [Accepted: 03/13/2021] [Indexed: 11/28/2022] Open
Abstract
Presynaptic neurotransmitter release is strictly regulated by SNARE proteins, Ca2+ and a number of Ca2+ sensors including synaptotagmins (Syts) and Double C2 domain proteins (Doc2s). More than seventy years after the original description of spontaneous release, the mechanism that regulates this process is still poorly understood. Syt-1, Syt7 and Doc2 proteins contribute predominantly, but not exclusively, to synchronous, asynchronous and spontaneous phases of release. The proteins share a conserved tandem C2 domain architecture, but are functionally diverse in their subcellular location, Ca2+-binding properties and protein interactions. In absence of Syt-1, Doc2a and -b, neurons still exhibit spontaneous vesicle fusion which remains Ca2+-sensitive, suggesting the existence of additional sensors. Here, we selected Doc2c, rabphilin-3a and Syt-7 as three potential Ca2+ sensors for their sequence homology with Syt-1 and Doc2b. We genetically ablated each candidate gene in absence of Doc2a and -b and investigated spontaneous and evoked release in glutamatergic hippocampal neurons, cultured either in networks or on microglial islands (autapses). The removal of Doc2c had no effect on spontaneous or evoked release. Syt-7 removal also did not affect spontaneous release, although it altered short-term plasticity by accentuating short-term depression. The removal of rabphilin caused an increased spontaneous release frequency in network cultures, an effect that was not observed in autapses. Taken together, we conclude that Doc2c and Syt-7 do not affect spontaneous release of glutamate in hippocampal neurons, while our results suggest a possible regulatory role of rabphilin-3a in neuronal networks. These findings importantly narrow down the repertoire of synaptic Ca2+ sensors that may be implicated in the spontaneous release of glutamate.
Collapse
Affiliation(s)
- Quentin Bourgeois-Jaarsma
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
| | - Pablo Miaja Hernandez
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
| | - Alexander J Groffen
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands; Department of Clinical Genetics, VU Medical Center, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
| |
Collapse
|
29
|
Parker PD, Suryavanshi P, Melone M, Sawant-Pokam PA, Reinhart KM, Kaufmann D, Theriot JJ, Pugliese A, Conti F, Shuttleworth CW, Pietrobon D, Brennan KC. Non-canonical glutamate signaling in a genetic model of migraine with aura. Neuron 2021; 109:611-628.e8. [PMID: 33321071 PMCID: PMC7889497 DOI: 10.1016/j.neuron.2020.11.018] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 10/09/2020] [Accepted: 11/17/2020] [Indexed: 12/13/2022]
Abstract
Migraine with aura is a common but poorly understood sensory circuit disorder. Monogenic models allow an opportunity to investigate its mechanisms, including spreading depolarization (SD), the phenomenon underlying migraine aura. Using fluorescent glutamate imaging, we show that awake mice carrying a familial hemiplegic migraine type 2 (FHM2) mutation have slower clearance during sensory processing, as well as previously undescribed spontaneous "plumes" of glutamate. Glutamatergic plumes overlapped anatomically with a reduced density of GLT-1a-positive astrocyte processes and were mimicked in wild-type animals by inhibiting glutamate clearance. Plume pharmacology and plume-like neural Ca2+ events were consistent with action-potential-independent spontaneous glutamate release, suggesting plumes are a consequence of inefficient clearance following synaptic release. Importantly, a rise in basal glutamate and plume frequency predicted the onset of SD in both FHM2 and wild-type mice, providing a novel mechanism in migraine with aura and, by extension, the other neurological disorders where SD occurs.
Collapse
Affiliation(s)
- Patrick D Parker
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA; Interdepartmental Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Pratyush Suryavanshi
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA; Interdepartmental Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Marcello Melone
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona 60020, Italy; Center for Neurobiology of Aging, IRCCS INRCA, Ancona 60020, Italy
| | - Punam A Sawant-Pokam
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Katelyn M Reinhart
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA; Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87106, USA
| | - Dan Kaufmann
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Jeremy J Theriot
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA
| | - Arianna Pugliese
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona 60020, Italy
| | - Fiorenzo Conti
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona 60020, Italy; Center for Neurobiology of Aging, IRCCS INRCA, Ancona 60020, Italy; Foundation for Molecular Medicine, Università Politecnica delle Marche, Ancona 60020, Italy
| | - C William Shuttleworth
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87106, USA
| | - Daniela Pietrobon
- Department of Biomedical Sciences and Padova Neuroscience Center (PNC), University of Padova, 35131 Padova, Italy; CNR Institute of Neuroscience, 35131 Padova, Italy.
| | - K C Brennan
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA.
| |
Collapse
|
30
|
Orexin-A differentially modulates inhibitory and excitatory synaptic transmission in rat inner retina. Neuropharmacology 2021; 187:108492. [PMID: 33582153 DOI: 10.1016/j.neuropharm.2021.108492] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 01/08/2021] [Accepted: 02/06/2021] [Indexed: 11/21/2022]
Abstract
In this work, modulation by orexin-A of the release of glutamate and GABA from bipolar and amacrine cells respectively was studied by examining the effects of the neuropeptide on miniature excitatory postsynaptic currents (mEPSCs) and miniature inhibitory postsynaptic currents (mIPSCs) of rat retinal ganglion cells (GCs). Using RNAscope in situ hybridization in combination with immunohistochemistry, we showed positive signals for orexin receptor-1 (OX1R) mRNA in the bipolar cell terminals and those for orexin receptor-2 (OX2R) mRNA in the amacrine cell terminals. With whole-cell patch-clamp recordings in rat retinal slices, we demonstrated that application of orexin-A reduced the interevent interval of mEPSCs of GCs through OX1R. However, it increased the interevent interval of mIPSCs, mediated by GABAA receptors, through OX2R. Furthermore, orexin-A-induced reduction of mEPSC interevent interval was abolished by the application of PI-PLC inhibitors or PKC inhibitors. In contrast, orexin-A-induced increase of GABAergic mIPSC interevent interval was mimicked by 8-Br-cAMP or an adenylyl cyclase activator, but was eliminated by PKA antagonists. Finally, application of nimodipine, an L-type Ca2+ channel blocker, increased both mEPSC and mIPSC interevent interval, and co-application of orexin-A no longer changed the mEPSCs and mIPSCs. We conclude that orexin-A increases presynaptic glutamate release onto GCs by activating L-type Ca2+ channels in bipolar cells, a process that is mediated by an OX1R/PI-PLC/PKC signaling pathway. However, orexin-A decreases presynaptic GABA release onto GCs by inhibiting L-type Ca2+ channels in amacrine cells, a process that is mediated by an OX2R/cAMP-PKA signaling pathway.
Collapse
|
31
|
Li S, Raychaudhuri S, Lee SA, Brockmann MM, Wang J, Kusick G, Prater C, Syed S, Falahati H, Ramos R, Bartol TM, Hosy E, Watanabe S. Asynchronous release sites align with NMDA receptors in mouse hippocampal synapses. Nat Commun 2021; 12:677. [PMID: 33514725 PMCID: PMC7846561 DOI: 10.1038/s41467-021-21004-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 01/08/2021] [Indexed: 01/30/2023] Open
Abstract
Neurotransmitter is released synchronously and asynchronously following an action potential. Our recent study indicates that the release sites of these two phases are segregated within an active zone, with asynchronous release sites enriched near the center in mouse hippocampal synapses. Here we demonstrate that synchronous and asynchronous release sites are aligned with AMPA receptor and NMDA receptor clusters, respectively. Computational simulations indicate that this spatial and temporal arrangement of release can lead to maximal membrane depolarization through AMPA receptors, alleviating the pore-blocking magnesium leading to greater activation of NMDA receptors. Together, these results suggest that release sites are likely organized to activate NMDA receptors efficiently.
Collapse
Affiliation(s)
- Shuo Li
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
- Department of Biological and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Sumana Raychaudhuri
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Stephen Alexander Lee
- Neurobiology Course, The Marine Biological Laboratory, Woods Hole, MA, USA
- Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - Marisa M Brockmann
- Institute of Neurophysiology, Charité Universitätsmedizin, Berlin, Germany
| | - Jing Wang
- ThermoFisher Scientific, Hillsboro, OR, USA
| | - Grant Kusick
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
- Biochemistry, Cellular and Molecular Biology Graduate Program, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Christine Prater
- Neurobiology Course, The Marine Biological Laboratory, Woods Hole, MA, USA
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Sarah Syed
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Hanieh Falahati
- Neurobiology Course, The Marine Biological Laboratory, Woods Hole, MA, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA
| | - Raul Ramos
- Neurobiology Course, The Marine Biological Laboratory, Woods Hole, MA, USA
- Department of Biology, Brandeis University, Waltham, MA, USA
| | - Tomas M Bartol
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Eric Hosy
- Centre National de la Recherche Scientifique, Bordeaux, France
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Bordeaux, France
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA.
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD, USA.
| |
Collapse
|
32
|
Tyurikova O, Zheng K, Nicholson E, Timofeeva Y, Semyanov A, Volynski KE, Rusakov DA. Fluorescence lifetime imaging reveals regulation of presynaptic Ca 2+ by glutamate uptake and mGluRs, but not somatic voltage in cortical neurons. J Neurochem 2021; 156:48-58. [PMID: 32418206 PMCID: PMC8436763 DOI: 10.1111/jnc.15094] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 04/21/2020] [Accepted: 05/08/2020] [Indexed: 11/28/2022]
Abstract
Brain function relies on vesicular release of neurotransmitters at chemical synapses. The release probability depends on action potential-evoked presynaptic Ca2+ entry, but also on the resting Ca2+ level. Whether these basic aspects of presynaptic calcium homeostasis show any consistent trend along the axonal path, and how they are controlled by local network activity, remains poorly understood. Here, we take advantage of the recently advanced FLIM-based method to monitor presynaptic Ca2+ with nanomolar sensitivity. We find that, in cortical pyramidal neurons, action potential-evoked calcium entry (range 10-300 nM), but not the resting Ca2+ level (range 10-100 nM), tends to increase with higher order of axonal branches. Blocking astroglial glutamate uptake reduces evoked Ca2+ entry but has little effect on resting Ca2+ whereas both appear boosted by the constitutive activation of group 1/2 metabotropic glutamate receptors. We find no consistent effect of transient somatic depolarization or hyperpolarization on presynaptic Ca2+ entry or its basal level. The results unveil some key aspects of presynaptic machinery in cortical circuits, shedding light on basic principles of synaptic connectivity in the brain.
Collapse
Affiliation(s)
- Olga Tyurikova
- Queen Square Institute of NeurologyUniversity College LondonLondonUK
- Shemyakin‐Ovchinnikov Institute of Bioorganic ChemistryRussian Academy of SciencesMoscowRussia
| | - Kaiyu Zheng
- Queen Square Institute of NeurologyUniversity College LondonLondonUK
| | | | - Yulia Timofeeva
- Queen Square Institute of NeurologyUniversity College LondonLondonUK
- Department of Computer Science, Centre for Complexity Science, University of WarwickCoventryUK
| | - Alexey Semyanov
- Shemyakin‐Ovchinnikov Institute of Bioorganic ChemistryRussian Academy of SciencesMoscowRussia
- Sechenov First Moscow State Medical UniversityMoscowRussia
| | | | - Dmitri A. Rusakov
- Queen Square Institute of NeurologyUniversity College LondonLondonUK
| |
Collapse
|
33
|
Dolphin AC. Functions of Presynaptic Voltage-gated Calcium Channels. FUNCTION (OXFORD, ENGLAND) 2020; 2:zqaa027. [PMID: 33313507 PMCID: PMC7709543 DOI: 10.1093/function/zqaa027] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 10/16/2020] [Accepted: 10/20/2020] [Indexed: 01/06/2023]
Abstract
Voltage-gated calcium channels are the principal conduits for depolarization-mediated Ca2+ entry into excitable cells. In this review, the biophysical properties of the relevant members of this family of channels, those that are present in presynaptic terminals, will be discussed in relation to their function in mediating neurotransmitter release. Voltage-gated calcium channels have properties that ensure they are specialized for particular roles, for example, differences in their activation voltage threshold, their various kinetic properties, and their voltage-dependence of inactivation. All these attributes play into the ability of the various voltage-gated calcium channels to participate in different patterns of presynaptic vesicular release. These include synaptic transmission resulting from single action potentials, and longer-term changes mediated by bursts or trains of action potentials, as well as release resulting from graded changes in membrane potential in specialized sensory synapses.
Collapse
Affiliation(s)
- Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, WC1E 6BT, UK,Address correspondence to A.C.D. (e-mail: )
| |
Collapse
|
34
|
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] [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.
Collapse
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.
| |
Collapse
|
35
|
Huson V, Meijer M, Dekker R, Ter Veer M, Ruiter M, van Weering JR, Verhage M, Cornelisse LN. Post-tetanic potentiation lowers the energy barrier for synaptic vesicle fusion independently of Synaptotagmin-1. eLife 2020; 9:55713. [PMID: 32831174 PMCID: PMC7500951 DOI: 10.7554/elife.55713] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 08/23/2020] [Indexed: 11/13/2022] Open
Abstract
Previously, we showed that modulation of the energy barrier for synaptic vesicle fusion boosts release rates supralinearly (Schotten, 2015). Here we show that mouse hippocampal synapses employ this principle to trigger Ca2+-dependent vesicle release and post-tetanic potentiation (PTP). We assess energy barrier changes by fitting release kinetics in response to hypertonic sucrose. Mimicking activation of the C2A domain of the Ca2+-sensor Synaptotagmin-1 (Syt1), by adding a positive charge (Syt1D232N) or increasing its hydrophobicity (Syt14W), lowers the energy barrier. Removing Syt1 or impairing its release inhibitory function (Syt19Pro) increases spontaneous release without affecting the fusion barrier. Both phorbol esters and tetanic stimulation potentiate synaptic strength, and lower the energy barrier equally well in the presence and absence of Syt1. We propose a model where tetanic stimulation activates Syt1-independent mechanisms that lower the energy barrier and act additively with Syt1-dependent mechanisms to produce PTP by exerting multiplicative effects on release rates.
Collapse
Affiliation(s)
- Vincent Huson
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands
| | - Marieke Meijer
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands
| | - Rien Dekker
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands
| | - Mirelle Ter Veer
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam, Netherlands
| | - Marvin Ruiter
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam, Netherlands
| | - Jan Rt van Weering
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands
| | - Matthijs Verhage
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands.,Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam, Netherlands
| | - Lennart Niels Cornelisse
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands
| |
Collapse
|
36
|
Mechanisms Underlying Enhancement of Spontaneous Glutamate Release by Group I mGluRs at a Central Auditory Synapse. J Neurosci 2020; 40:7027-7042. [PMID: 32801152 DOI: 10.1523/jneurosci.2771-19.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 08/04/2020] [Accepted: 08/07/2020] [Indexed: 02/06/2023] Open
Abstract
One emerging concept in neuroscience states that synaptic vesicles and the molecular machinery underlying spontaneous transmitter release are different from those underlying action potential-driven synchronized transmitter release. Differential neuromodulation of these two distinct release modes by metabotropic glutamate receptors (mGluRs) constitutes critical supporting evidence. However, the mechanisms underlying such a differential modulation are not understood. Here, we investigated the mechanisms of the modulation by group I mGluRs (mGluR Is) on spontaneous glutamate release in the medial nucleus of the trapezoid body (MNTB), an auditory brainstem nucleus critically involved in sound localization. Whole-cell patch recordings from brainstem slices of mice of both sexes were performed. Activation of mGluR I by 3,5-dihydroxyphenylglycine (3,5-DHPG; 200 μm) produced an inward current at -60 mV and increased spontaneous glutamate release in MNTB neurons. Pharmacological evidence indicated involvement of both mGluR1 and mGluR5, which was further supported for mGluR5 by immunolabeling results. The modulation was eliminated by blocking NaV channels (tetrodotoxin, 1 μm), persistent Na+ current (I NaP; riluzole, 10 μm), or CaV channels (CdCl2, 100 μm). Presynaptic calyx recordings revealed that 3,5-DHPG shifted the activation of I NaP to more hyperpolarized voltages and increased I NaP at resting membrane potential. Our data indicate that mGluR I enhances spontaneous glutamate release via regulation of I NaP and subsequent Ca2+-dependent processes under resting condition.SIGNIFICANCE STATEMENT For brain cells to communicate with each other, neurons release chemical messengers, termed neurotransmitters, in response to action potential invasion (evoked release). Neurons also release neurotransmitters spontaneously. Recent work has revealed different release machineries underlying these two release modes, and their different roles in synaptic development and plasticity. Our recent work discovered differential neuromodulation of these two release modes, but the mechanisms are not well understood. The present study showed that activation of group I metabotropic glutamate receptors enhanced spontaneous glutamate release in an auditory brainstem nucleus, while suppressing evoked release. The modulation is dependent on a persistent Na+ current and involves subsequent Ca2+ signaling, providing insight into the mechanisms underlying the different release modes in auditory processing.
Collapse
|
37
|
Chamberland S, Timofeeva Y, Evstratova A, Norman CA, Volynski K, Tóth K. Slow-decaying presynaptic calcium dynamics gate long-lasting asynchronous release at the hippocampal mossy fiber to CA3 pyramidal cell synapse. Synapse 2020; 74:e22178. [PMID: 32598500 PMCID: PMC7685170 DOI: 10.1002/syn.22178] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 06/23/2020] [Accepted: 06/24/2020] [Indexed: 01/21/2023]
Abstract
Action potentials trigger two modes of neurotransmitter release, with a fast synchronous component and a temporally delayed asynchronous release. Asynchronous release contributes to information transfer at synapses, including at the hippocampal mossy fiber (MF) to CA3 pyramidal cell synapse where it controls the timing of postsynaptic CA3 pyramidal neuron firing. Here, we identified and characterized the main determinants of asynchronous release at the MF–CA3 synapse. We found that asynchronous release at MF–CA3 synapses can last on the order of seconds following repetitive MF stimulation. Elevating the stimulation frequency or the external Ca2+ concentration increased the rate of asynchronous release, thus, arguing that presynaptic Ca2+ dynamics is the major determinant of asynchronous release rate. Direct MF bouton Ca2+ imaging revealed slow Ca2+ decay kinetics of action potential (AP) burst‐evoked Ca2+ transients. Finally, we observed that asynchronous release was preferentially mediated by Ca2+ influx through P/Q‐type voltage‐gated Ca2+ channels, while the contribution of N‐type VGCCs was limited. Overall, our results uncover the determinants of long‐lasting asynchronous release from MF terminals and suggest that asynchronous release could influence CA3 pyramidal cell firing up to seconds following termination of granule cell bursting.
Collapse
Affiliation(s)
- Simon Chamberland
- CERVO Brain Research Center, Department of Psychiatry and Neuroscience, Université Laval, Quebec, QC, Canada
| | - Yulia Timofeeva
- Department of Computer Science, University of Warwick, Coventry, UK.,Centre for Complexity Science, University of Warwick, Coventry, UK.,University College London Institute of Neurology, University College London, London, UK
| | - Alesya Evstratova
- CERVO Brain Research Center, Department of Psychiatry and Neuroscience, Université Laval, Quebec, QC, Canada
| | - Christopher A Norman
- Mathematics for Real-World Systems Centre for Doctoral Training, University of Warwick, Coventry, UK
| | - Kirill Volynski
- University College London Institute of Neurology, University College London, London, UK
| | - Katalin Tóth
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| |
Collapse
|
38
|
Bikbaev A, Ciuraszkiewicz-Wojciech A, Heck J, Klatt O, Freund R, Mitlöhner J, Enrile Lacalle S, Sun M, Repetto D, Frischknecht R, Ablinger C, Rohlmann A, Missler M, Obermair GJ, Di Biase V, Heine M. Auxiliary α2δ1 and α2δ3 Subunits of Calcium Channels Drive Excitatory and Inhibitory Neuronal Network Development. J Neurosci 2020; 40:4824-4841. [PMID: 32414783 PMCID: PMC7326358 DOI: 10.1523/jneurosci.1707-19.2020] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 03/31/2020] [Accepted: 05/09/2020] [Indexed: 01/21/2023] Open
Abstract
VGCCs are multisubunit complexes that play a crucial role in neuronal signaling. Auxiliary α2δ subunits of VGCCs modulate trafficking and biophysical properties of the pore-forming α1 subunit and trigger excitatory synaptogenesis. Alterations in the expression level of α2δ subunits were implicated in several syndromes and diseases, including chronic neuropathic pain, autism, and epilepsy. However, the contribution of distinct α2δ subunits to excitatory/inhibitory imbalance and aberrant network connectivity characteristic for these pathologic conditions remains unclear. Here, we show that α2δ1 overexpression enhances spontaneous neuronal network activity in developing and mature cultures of hippocampal neurons. In contrast, overexpression, but not downregulation, of α2δ3 enhances neuronal firing in immature cultures, whereas later in development it suppresses neuronal activity. We found that α2δ1 overexpression increases excitatory synaptic density and selectively enhances presynaptic glutamate release, which is impaired on α2δ1 knockdown. Overexpression of α2δ3 increases the excitatory synaptic density as well but also facilitates spontaneous GABA release and triggers an increase in the density of inhibitory synapses, which is accompanied by enhanced axonaloutgrowth in immature interneurons. Together, our findings demonstrate that α2δ1 and α2δ3 subunits play distinct but complementary roles in driving formation of structural and functional network connectivity during early development. An alteration in α2δ surface expression during critical developmental windows can therefore play a causal role and have a profound impact on the excitatory-to-inhibitory balance and network connectivity.SIGNIFICANCE STATEMENT The computational capacity of neuronal networks is determined by their connectivity. Chemical synapses are the main interface for transfer of information between individual neurons. The initial formation of network connectivity requires spontaneous electrical activity and the calcium channel-mediated signaling. We found that, in early development, auxiliary α2δ3 subunits of calcium channels foster presynaptic release of GABA, trigger formation of inhibitory synapses, and promote axonal outgrowth in inhibitory interneurons. In contrast, later in development, α2δ1 subunits promote the glutamatergic neurotransmission and synaptogenesis, as well as strongly enhance neuronal network activity. We propose that formation of connectivity in neuronal networks is associated with a concerted interplay of α2δ1 and α2δ3 subunits of calcium channels.
Collapse
Affiliation(s)
- Arthur Bikbaev
- RG Functional Neurobiology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz, 55128, Germany
| | - Anna Ciuraszkiewicz-Wojciech
- RG Molecular Physiology, Leibniz Institute for Neurobiology, Magdeburg, 39118, Germany
- Center for Behavioral Brain Sciences, Otto-von-Guericke University Magdeburg, Magdeburg, 39106, Germany
| | - Jennifer Heck
- RG Functional Neurobiology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz, 55128, Germany
| | - Oliver Klatt
- Institute for Anatomy and Molecular Neurobiology, University of Münster, Münster, 48149, Germany
| | - Romy Freund
- RG Molecular Physiology, Leibniz Institute for Neurobiology, Magdeburg, 39118, Germany
| | - Jessica Mitlöhner
- RG Brain Extracellular Matrix, Leibniz Institute for Neurobiology, Magdeburg, 39118, Germany
| | - Sara Enrile Lacalle
- RG Molecular Physiology, Leibniz Institute for Neurobiology, Magdeburg, 39118, Germany
| | - Miao Sun
- Institute for Anatomy and Molecular Neurobiology, University of Münster, Münster, 48149, Germany
| | - Daniele Repetto
- Institute for Anatomy and Molecular Neurobiology, University of Münster, Münster, 48149, Germany
| | - Renato Frischknecht
- RG Brain Extracellular Matrix, Leibniz Institute for Neurobiology, Magdeburg, 39118, Germany
- Department of Biology, Animal Physiology, Friedrich Alexander University of Erlangen-Nuremberg, Erlangen, 91058, Germany
| | - Cornelia Ablinger
- Institute of Physiology, Medical University Innsbruck, Innsbruck, 6020, Austria
| | - Astrid Rohlmann
- Institute for Anatomy and Molecular Neurobiology, University of Münster, Münster, 48149, Germany
| | - Markus Missler
- Institute for Anatomy and Molecular Neurobiology, University of Münster, Münster, 48149, Germany
| | - Gerald J Obermair
- Division Physiology, Karl Landsteiner University of Health Sciences, Krems, 3500, Austria
| | - Valentina Di Biase
- Institute of Molecular and Clinical Pharmacology, Medical University Innsbruck, Innsbruck, 6020, Austria
| | - Martin Heine
- RG Functional Neurobiology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz, 55128, Germany
- Center for Behavioral Brain Sciences, Otto-von-Guericke University Magdeburg, Magdeburg, 39106, Germany
| |
Collapse
|
39
|
Glebov OO. Tonic NMDA receptor signalling shapes endosomal organisation in mammalian cells. Sci Rep 2020; 10:9315. [PMID: 32518335 PMCID: PMC7283358 DOI: 10.1038/s41598-020-66071-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 04/21/2020] [Indexed: 12/02/2022] Open
Abstract
Calcium signalling through NMDA-type glutamate receptors (NMDARs) plays a key role in synaptic plasticity in the central nervous system (CNS). NMDAR expression has also been detected in other tissues and aberrant glutamate signalling has been linked to cancer; however, the significance of NMDAR function outside of the CNS remains unclear. Here, I show that removal of extracellular calcium rapidly decreases the size of early endosomes in primary human fibroblasts. This effect can be mimicked by blockade of NMDA-type glutamate receptors but not voltage-gated calcium channels (VGCCs), and can also be observed in primary hippocampal neurons and Jurkat T cells. Conversely, in a breast cancer cell line MDA-MB-231 NMDAR blockade results in an increase in endosomal size and decrease in number. These findings reveal that calcium signalling via glutamate receptors controls the structure of the endosomal system and suggest that aberrations in NMDAR-regulated membrane trafficking may be associated with cancer.
Collapse
Affiliation(s)
- Oleg O Glebov
- Institute of Neuroregeneration and Neurorehabilitation, Qingdao University, Qingdao, 266071, Shandong, China. .,Department of Old Age Psychiatry, Institute of Psychiatry, Psychology & Neuroscience, King's College London, 16 De Crespigny Park, London, SE5 8AF, UK.
| |
Collapse
|
40
|
Dolphin AC, Lee A. Presynaptic calcium channels: specialized control of synaptic neurotransmitter release. Nat Rev Neurosci 2020; 21:213-229. [PMID: 32161339 PMCID: PMC7873717 DOI: 10.1038/s41583-020-0278-2] [Citation(s) in RCA: 112] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/12/2020] [Indexed: 11/09/2022]
Abstract
Chemical synapses are heterogeneous junctions formed between neurons that are specialized for the conversion of electrical impulses into the exocytotic release of neurotransmitters. Voltage-gated Ca2+ channels play a pivotal role in this process as they are the major conduits for the Ca2+ ions that trigger the fusion of neurotransmitter-containing vesicles with the presynaptic membrane. Alterations in the intrinsic function of these channels and their positioning within the active zone can profoundly alter the timing and strength of synaptic output. Advances in optical and electron microscopic imaging, structural biology and molecular techniques have facilitated recent breakthroughs in our understanding of the properties of voltage-gated Ca2+ channels that support their presynaptic functions. Here we examine the nature of these channels, how they are trafficked to and anchored within presynaptic boutons, and the mechanisms that allow them to function optimally in shaping the flow of information through neural circuits.
Collapse
Affiliation(s)
- Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK.
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA, USA.
| |
Collapse
|
41
|
Heine M, Holcman D. Asymmetry Between Pre- and Postsynaptic Transient Nanodomains Shapes Neuronal Communication. Trends Neurosci 2020; 43:182-196. [DOI: 10.1016/j.tins.2020.01.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 01/12/2020] [Accepted: 01/13/2020] [Indexed: 10/25/2022]
|
42
|
Doc2 Proteins Are Not Required for the Increased Spontaneous Release Rate in Synaptotagmin-1-Deficient Neurons. J Neurosci 2020; 40:2606-2617. [PMID: 32098902 DOI: 10.1523/jneurosci.0309-19.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 01/10/2020] [Accepted: 01/23/2020] [Indexed: 11/21/2022] Open
Abstract
Regulated secretion is controlled by Ca2+ sensors with different affinities and subcellular distributions. Inactivation of Syt1 (synaptotagmin-1), the main Ca2+ sensor for synchronous neurotransmission in many neurons, enhances asynchronous and spontaneous release rates, suggesting that Syt1 inhibits other sensors with higher Ca2+ affinities and/or lower cooperativities. Such sensors could include Doc2a and Doc2b, which have been implicated in spontaneous and asynchronous neurotransmitter release and compete with Syt1 for binding SNARE complexes. Here, we tested this hypothesis using triple-knock-out mice. Inactivation of Doc2a and Doc2b in Syt1-deficient neurons did not reduce the high spontaneous release rate. Overexpression of Doc2b variants in triple-knock-out neurons reduced spontaneous release but did not rescue synchronous release. A chimeric construct in which the C2AB domain of Syt1 was substituted by that of Doc2b did not support synchronous release either. Conversely, the soluble C2AB domain of Syt1 did not affect spontaneous release. We conclude that the high spontaneous release rate in synaptotagmin-deficient neurons does not involve the binding of Doc2 proteins to Syt1 binding sites in the SNARE complex. Instead, our results suggest that the C2AB domains of Syt1 and Doc2b specifically support synchronous and spontaneous release by separate mechanisms. (Both male and female neurons were studied without sex determination.)SIGNIFICANCE STATEMENT Neurotransmission in the brain is regulated by presynaptic Ca2+ concentrations. Multiple Ca2+ sensor proteins contribute to synchronous (Syt1, Syt2), asynchronous (Syt7), and spontaneous (Doc2a/Doc2b) phases of neurotransmitter release. Genetic ablation of synchronous release was previously shown to affect other release phases, suggesting that multiple sensors may compete for similar release sites, together encoding stimulus-secretion coupling over a large range of synaptic Ca2+ concentrations. Here, we investigated the extent of functional overlap between Syt1, Doc2a, and Doc2b by reintroducing wild-type and mutant proteins in triple-knock-out neurons, and conclude that the sensors are highly specialized for different phases of release.
Collapse
|
43
|
Synaptotagmin 1 oligomers clamp and regulate different modes of neurotransmitter release. Proc Natl Acad Sci U S A 2020; 117:3819-3827. [PMID: 32015138 PMCID: PMC7035618 DOI: 10.1073/pnas.1920403117] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Release of neurotransmitters relies on submillisecond coupling of synaptic vesicle fusion to the triggering signal: AP-evoked presynaptic Ca2+ influx. The key player that controls exocytosis of the synaptic vesicle is the Ca2+ sensor synaptotagmin 1 (Syt1). While the Ca2+ activation of Syt1 has been extensively characterized, how Syt1 reversibly clamps vesicular fusion remains enigmatic. Here, using a targeted mutation combined with fluorescence imaging and electrophysiology, we show that the structural feature of Syt1 to self-oligomerize provides the molecular basis for clamping of spontaneous and asynchronous release but is not required for triggering of synchronous release. Our findings propose a mechanistic model that explains how Syt1 oligomers regulate different modes of transmitter release in neuronal synapses. Synaptotagmin 1 (Syt1) synchronizes neurotransmitter release to action potentials (APs) acting as the fast Ca2+ release sensor and as the inhibitor (clamp) of spontaneous and delayed asynchronous release. While the Syt1 Ca2+ activation mechanism has been well-characterized, how Syt1 clamps transmitter release remains enigmatic. Here we show that C2B domain-dependent oligomerization provides the molecular basis for the Syt1 clamping function. This follows from the investigation of a designed mutation (F349A), which selectively destabilizes Syt1 oligomerization. Using a combination of fluorescence imaging and electrophysiology in neocortical synapses, we show that Syt1F349A is more efficient than wild-type Syt1 (Syt1WT) in triggering synchronous transmitter release but fails to clamp spontaneous and synaptotagmin 7 (Syt7)-mediated asynchronous release components both in rescue (Syt1−/− knockout background) and dominant-interference (Syt1+/+ background) conditions. Thus, we conclude that Ca2+-sensitive Syt1 oligomers, acting as an exocytosis clamp, are critical for maintaining the balance among the different modes of neurotransmitter release.
Collapse
|
44
|
A lysosomal K + channel regulates large particle phagocytosis by facilitating lysosome Ca 2+ release. Sci Rep 2020; 10:1038. [PMID: 31974459 PMCID: PMC6978423 DOI: 10.1038/s41598-020-57874-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 12/31/2019] [Indexed: 12/13/2022] Open
Abstract
Macrophages are highly specialized in removing large particles including dead cells and cellular debris. When stimulated, delivery of the intracellular lysosomal membranes is required for the formation of plasmalemmal pseudopods and phagosomes. As a key lysosomal Ca2+ channel, Transient Receptor Potential Mucolipin-1 (TRPML1) regulates lysosomal exocytosis and subsequent phagosome biogenesis, thereby promoting phagocytosis of large extracellular particles. Recently, we have suggested that TRPML1-mediated lysosomal exocytosis is essentially dependent on lysosomal big conductance Ca2+-activated potassium (BK) channel. Therefore, we predict that lysosomal BK channels regulate large particle phagocytosis. In this study, by using RAW264.7 macrophage cell line and bone marrow-derived macrophages, we show that although BK is dispensable for small particle uptake, loss of BK significantly inhibits the ingestion of large particles whereas activating BK increases the uptake of large particles. BK facilitating effect on large particle ingestion is inhibited by either blocking TRPML1 or suppressing lysosomal exocytosis. Additionally, the increased uptake of large particles by activating TRPML1 is eliminated by inhibiting BK. These data suggest that BK and TRPML1 are functionally coupled to regulate large particle phagocytosis through modulating lysosomal exocytosis.
Collapse
|
45
|
Doc2b Ca 2+ binding site mutants enhance synaptic release at rest at the expense of sustained synaptic strength. Sci Rep 2019; 9:14408. [PMID: 31594980 PMCID: PMC6783474 DOI: 10.1038/s41598-019-50684-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Accepted: 09/11/2019] [Indexed: 12/01/2022] Open
Abstract
Communication between neurons involves presynaptic neurotransmitter release which can be evoked by action potentials or occur spontaneously as a result of stochastic vesicle fusion. The Ca2+-binding double C2 proteins Doc2a and –b were implicated in spontaneous and asynchronous evoked release, but the mechanism remains unclear. Here, we compared wildtype Doc2b with two Ca2+ binding site mutants named DN and 6A, previously classified as gain- and loss-of-function mutants. They carry the substitutions D218,220N or D163,218,220,303,357,359A respectively. We found that both mutants bound phospholipids at low Ca2+ concentrations and were membrane-associated in resting neurons, thus mimicking a Ca2+-activated state. Their overexpression in hippocampal primary cultured neurons had similar effects on spontaneous and evoked release, inducing high mEPSC frequencies and increased short-term depression. Together, these data suggest that the DN and 6A mutants both act as gain-of-function mutants at resting conditions.
Collapse
|
46
|
Buch D, Chabriat H. Lamotrigine in the Prevention of Migraine With Aura: A Narrative Review. Headache 2019; 59:1187-1197. [PMID: 31468532 DOI: 10.1111/head.13615] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/31/2019] [Indexed: 01/03/2023]
Abstract
BACKGROUND Lamotrigine is not recommended in the prevention of migraine in general but some reports suggest that it might be effective for treating specifically migraine with aura (MA). This review aims to summarize the related data from the literature and to better understand this discrepancy. METHODS All reports from the literature related to the use of lamotrigine in migraine with or without aura published prior to February 2019 found using PUBMED and the 2 keywords "migraine" AND "lamotrigine" were reviewed. Original studies, published in full, systematic reviews, and all case reports were synthetized. We also examined the risk profile, pharmacokinetics, and mode of action of lamotrigine in view of the presumed mechanism of MA. RESULTS Lamotrigine was tested in different populations of migraineurs, but previous studies had small sample sizes (n < 35) and might not have been powered enough for detecting a potential benefit of lamotrigine in MA. Accumulating data suggest that the drug can reduce both the frequency and severity of aura symptoms in multiple conditions and is well tolerated. CONCLUSION Lamotrigine appears promising for treating attacks of MA and related clinical manifestations because of its high potential of efficacy, low-risk profile, and cost. Additional studies are needed for testing lamotrigine in patients with MA.
Collapse
Affiliation(s)
- Dan Buch
- Neurology Department, DHU Neuro-Vasc, Hopital Lariboisière, Paris, France
| | - Hugues Chabriat
- Neurology Department, DHU Neuro-Vasc, Hopital Lariboisière, Paris, France.,INSERM U1161, Université Denis Diderot, Paris, France
| |
Collapse
|
47
|
Spontaneous Vesicle Fusion Is Differentially Regulated at Cholinergic and GABAergic Synapses. Cell Rep 2019; 22:2334-2345. [PMID: 29490270 DOI: 10.1016/j.celrep.2018.02.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 01/11/2018] [Accepted: 02/06/2018] [Indexed: 12/23/2022] Open
Abstract
The locomotion of C. elegans is balanced by excitatory and inhibitory neurotransmitter release at neuromuscular junctions. However, the molecular mechanisms that maintain the balance of synaptic transmission remain enigmatic. Here, we investigated the function of voltage-gated Ca2+ channels in triggering spontaneous release at cholinergic and GABAergic synapses. Recordings of the miniature excitatory/inhibitory postsynaptic currents (mEPSCs and mIPSCs, respectively) showed that UNC-2/CaV2 and EGL-19/CaV1 channels are the two major triggers for spontaneous release. Notably, however, Ca2+-independent spontaneous release was observed at GABAergic but not cholinergic synapses. Functional screening led to the identification of hypomorphic unc-64/Syntaxin-1A and snb-1/VAMP2 mutants in which mEPSCs are severely impaired, whereas mIPSCs remain unaltered, indicating differential regulation of these currents at cholinergic and GABAergic synapses. Moreover, Ca2+-independent spontaneous GABA release was nearly abolished in the hypomorphic unc-64 and snb-1 mutants, suggesting distinct mechanisms for Ca2+-dependent and Ca2+-independent spontaneous release.
Collapse
|
48
|
Burke KJ, Bender KJ. Modulation of Ion Channels in the Axon: Mechanisms and Function. Front Cell Neurosci 2019; 13:221. [PMID: 31156397 PMCID: PMC6533529 DOI: 10.3389/fncel.2019.00221] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 05/01/2019] [Indexed: 12/11/2022] Open
Abstract
The axon is responsible for integrating synaptic signals, generating action potentials (APs), propagating those APs to downstream synapses and converting them into patterns of neurotransmitter vesicle release. This process is mediated by a rich assortment of voltage-gated ion channels whose function can be affected on short and long time scales by activity. Moreover, neuromodulators control the activity of these proteins through G-protein coupled receptor signaling cascades. Here, we review cellular mechanisms and signaling pathways involved in axonal ion channel modulation and examine how changes to ion channel function affect AP initiation, AP propagation, and the release of neurotransmitter. We then examine how these mechanisms could modulate synaptic function by focusing on three key features of synaptic information transmission: synaptic strength, synaptic variability, and short-term plasticity. Viewing these cellular mechanisms of neuromodulation from a functional perspective may assist in extending these findings to theories of neural circuit function and its neuromodulation.
Collapse
Affiliation(s)
| | - Kevin J. Bender
- Neuroscience Graduate Program and Department of Neurology, Kavli Institute for Fundamental Neuroscience, Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
| |
Collapse
|
49
|
Guzman GA, Guzman RE, Jordan N, Hidalgo P. A Tripartite Interaction Among the Calcium Channel α 1- and β-Subunits and F-Actin Increases the Readily Releasable Pool of Vesicles and Its Recovery After Depletion. Front Cell Neurosci 2019; 13:125. [PMID: 31130843 PMCID: PMC6509170 DOI: 10.3389/fncel.2019.00125] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 03/13/2019] [Indexed: 11/13/2022] Open
Abstract
Neurotransmitter release is initiated by the influx of Ca2+via voltage-gated calcium channels. The accessory β-subunit (CaVβ) of these channels shapes synaptic transmission by associating with the pore-forming subunit (CaVα1) and up-regulating presynaptic calcium currents. Besides CaVα1, CaVβ interacts with several partners including actin filaments (F-actin). These filaments are known to associate with synaptic vesicles (SVs) at the presynaptic terminals and support their translocation within different pools, but the role of CaVβ/F-actin association on synaptic transmission has not yet been explored. We here study how CaVβ4, the major calcium channel β isoform in mamalian brain, modifies synaptic transmission in concert with F-actin in cultured hippocampal neurons. We analyzed the effect of exogenous CaVβ4 before and after pharmacological disruption of the actin cytoskeleton and dissected calcium channel-dependent and -independent functions by comparing the effects of the wild-type subunit with the one bearing a double mutation that impairs binding to CaVα1. We found that exogenously expressed wild-type CaVβ4 enhances spontaneous and depolarization-evoked excitatory postsynaptic currents (EPSCs) without altering synaptogenesis. CaVβ4 increases the size of the readily releasable pool (RRP) of SVs at resting conditions and accelerates their recovery after depletion. The enhanced neurotransmitter release induced by CaVβ4 is abolished upon disruption of the actin cytoskeleton. The CaVα1 association-deficient CaVβ4 mutant associates with actin filaments, but neither alters postsynaptic responses nor the time course of the RRP recovery. Furthermore, this mutant protein preserves the ability to increase the RRP size. These results indicate that the interplay between CaVβ4 and F-actin also support the recruitment of SVs to the RRP in a CaVα1-independent manner. Our studies show an emerging role of CaVβ in determining SV maturation toward the priming state and its replenishment after release. We envision that this subunit plays a role in coupling exocytosis to endocytosis during the vesicle cycle.
Collapse
Affiliation(s)
- Gustavo A Guzman
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, Jülich, Germany
| | - Raul E Guzman
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, Jülich, Germany
| | - Nadine Jordan
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, Jülich, Germany
| | - Patricia Hidalgo
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, Jülich, Germany.,Institute of Biochemistry, Heinrich-Heine University, Düsseldorf, Germany
| |
Collapse
|
50
|
Jensen TP, Zheng K, Cole N, Marvin JS, Looger LL, Rusakov DA. Multiplex imaging relates quantal glutamate release to presynaptic Ca 2+ homeostasis at multiple synapses in situ. Nat Commun 2019; 10:1414. [PMID: 30926781 PMCID: PMC6441074 DOI: 10.1038/s41467-019-09216-8] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 02/25/2019] [Indexed: 12/17/2022] Open
Abstract
Information processing by brain circuits depends on Ca2+-dependent, stochastic release of the excitatory neurotransmitter glutamate. Whilst optical glutamate sensors have enabled detection of synaptic discharges, understanding presynaptic machinery requires simultaneous readout of glutamate release and nanomolar presynaptic Ca2+ in situ. Here, we find that the fluorescence lifetime of the red-shifted Ca2+ indicator Cal-590 is Ca2+-sensitive in the nanomolar range, and employ it in combination with green glutamate sensors to relate quantal neurotransmission to presynaptic Ca2+ kinetics. Multiplexed imaging of individual and multiple synapses in identified axonal circuits reveals that glutamate release efficacy, but not its short-term plasticity, varies with time-dependent fluctuations in presynaptic resting Ca2+ or spike-evoked Ca2+ entry. Within individual presynaptic boutons, we find no nanoscopic co-localisation of evoked presynaptic Ca2+ entry with the prevalent glutamate release site, suggesting loose coupling between the two. The approach enables a better understanding of release machinery at central synapses.
Collapse
Affiliation(s)
- Thomas P Jensen
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK.
| | - Kaiyu Zheng
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK
| | - Nicholas Cole
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK
| | - Jonathan S Marvin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, 20147, VA, USA
| | - Loren L Looger
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, 20147, VA, USA
| | - Dmitri A Rusakov
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK.
| |
Collapse
|