51
|
Lane-Donovan C, Herz J. ApoE, ApoE Receptors, and the Synapse in Alzheimer's Disease. Trends Endocrinol Metab 2017; 28:273-284. [PMID: 28057414 PMCID: PMC5366078 DOI: 10.1016/j.tem.2016.12.001] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 11/29/2016] [Accepted: 12/07/2016] [Indexed: 01/24/2023]
Abstract
As the population ages, neurodegenerative diseases such as Alzheimer's disease (AD) are becoming a significant burden on patients, their families, and health-care systems. Neurodegenerative processes may start up to 15 years before outward signs and symptoms of AD, as evidenced by data from AD patients and mouse models. A major genetic risk factor for late-onset AD is the ɛ4 isoform of apolipoprotein E (ApoE4), which is present in almost 20% of the population. In this review we discuss the contribution of ApoE receptor signaling to the function of each component of the tripartite synapse - the axon terminal, the postsynaptic dendritic spine, and the astrocyte - and examine how these systems fail in the context of ApoE4 and AD.
Collapse
Affiliation(s)
- Courtney Lane-Donovan
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Joachim Herz
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Center for Neuroscience, Department of Neuroanatomy, Albert Ludwig University, Freiburg, Germany.
| |
Collapse
|
52
|
α-Synuclein promotes dilation of the exocytotic fusion pore. Nat Neurosci 2017; 20:681-689. [PMID: 28288128 PMCID: PMC5404982 DOI: 10.1038/nn.4529] [Citation(s) in RCA: 193] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 02/05/2017] [Indexed: 01/08/2023]
Abstract
The protein α-synuclein has a central role in the pathogenesis of Parkinson’s disease (PD). Similar to other proteins that accumulate in neurodegenerative disease, however, the function of α-synuclein remains unknown. Localization to the nerve terminal suggests a role in neurotransmitter release and over-expression inhibits regulated exocytosis, but previous work has failed to identify a clear physiological defect in mice lacking all three synuclein isoforms. Using adrenal chromaffin cells and neurons, we now find that both over-expressed and endogenous synuclein serve to accelerate the kinetics of individual exocytotic events, promoting cargo discharge and reducing pore closure (‘kiss-and-run’). Thus, synuclein exerts dose-dependent effects on dilation of the exocytotic fusion pore. Remarkably, mutations that cause PD abrogate this property of α-synuclein without impairing its ability to inhibit exocytosis when over-expressed, indicating a selective defect in normal function.
Collapse
|
53
|
Selective molecular impairment of spontaneous neurotransmission modulates synaptic efficacy. Nat Commun 2017; 8:14436. [PMID: 28186166 PMCID: PMC5311059 DOI: 10.1038/ncomms14436] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 12/29/2016] [Indexed: 12/12/2022] Open
Abstract
Recent studies suggest that stimulus-evoked and spontaneous neurotransmitter release processes are mechanistically distinct. Here we targeted the non-canonical synaptic vesicle SNAREs Vps10p-tail-interactor-1a (vti1a) and vesicle-associated membrane protein 7 (VAMP7) to specifically inhibit spontaneous release events and probe whether these events signal independently of evoked release to the postsynaptic neuron. We found that loss of vti1a and VAMP7 impairs spontaneous high-frequency glutamate release and augments unitary event amplitudes by reducing postsynaptic eukaryotic elongation factor 2 kinase (eEF2K) activity subsequent to the reduction in N-methyl-D-aspartate receptor (NMDAR) activity. Presynaptic, but not postsynaptic, loss of vti1a and VAMP7 occludes NMDAR antagonist-induced synaptic potentiation in an intact circuit, confirming the role of these vesicular SNAREs in setting synaptic strength. Collectively, these results demonstrate that spontaneous neurotransmission signals independently of stimulus-evoked release and highlight its role as a key regulator of postsynaptic efficacy.
Collapse
|
54
|
Afuwape OAT, Wasser CR, Schikorski T, Kavalali ET. Synaptic vesicle pool-specific modification of neurotransmitter release by intravesicular free radical generation. J Physiol 2016; 595:1223-1238. [PMID: 27723113 DOI: 10.1113/jp273115] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 10/04/2016] [Indexed: 01/22/2023] Open
Abstract
KEY POINTS Synaptic transmission is mediated by the release of neurotransmitters from synaptic vesicles in response to stimulation or through the spontaneous fusion of a synaptic vesicle with the presynaptic plasma membrane. There is growing evidence that synaptic vesicles undergoing spontaneous fusion versus those fusing in response to stimuli are functionally distinct. In this study, we acutely probe the effects of intravesicular free radical generation on synaptic vesicles that fuse spontaneously or in response to stimuli. By targeting vesicles that preferentially release spontaneously, we can dissociate the effects of intravesicular free radical generation on spontaneous neurotransmission from evoked neurotransmission and vice versa. Taken together, these results further advance our knowledge of the synapse and the nature of the different synaptic vesicle pools mediating neurotransmission. ABSTRACT Earlier studies suggest that spontaneous and evoked neurotransmitter release processes are maintained by synaptic vesicles which are segregated into functionally distinct pools. However, direct interrogation of the link between this putative synaptic vesicle pool heterogeneity and neurotransmission has been difficult. To examine this link, we tagged vesicles with horseradish peroxidase (HRP) - a haem-containing plant enzyme - or antibodies against synaptotagmin-1 (syt1). Filling recycling vesicles in hippocampal neurons with HRP and subsequent treatment with hydrogen peroxide (H2 O2 ) modified the properties of neurotransmitter release depending on the route of HRP uptake. While strong depolarization-induced uptake of HRP suppressed evoked release and augmented spontaneous release, HRP uptake during mild activity selectively impaired evoked release, whereas HRP uptake at rest solely potentiated spontaneous release. Expression of a luminal HRP-tagged syt1 construct and subsequent H2 O2 application resulted in a similar increase in spontaneous release and suppression as well as desynchronization of evoked release, recapitulating the canonical syt1 loss-of-function phenotype. An antibody targeting the luminal domain of syt1, on the other hand, showed that augmentation of spontaneous release and suppression of evoked release phenotypes are dissociable depending on whether the antibody uptake occurred at rest or during depolarization. Taken together, these findings indicate that vesicles that maintain spontaneous and evoked neurotransmitter release preserve their identity during recycling and syt1 function in suppression of spontaneous neurotransmission can be acutely dissociated from syt1 function to synchronize synaptic vesicle exocytosis upon stimulation.
Collapse
Affiliation(s)
- Olusoji A T Afuwape
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX, 75390-9111, USA
| | - Catherine R Wasser
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX, 75390-9111, USA
| | - Thomas Schikorski
- Department of Anatomy, Universidad Central Del Caribe, Bayamon, PR, 00960, Puerto Rico
| | - Ege T Kavalali
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX, 75390-9111, USA.,Department of Physiology, UT Southwestern Medical Center, Dallas, TX, 75390-9111, USA
| |
Collapse
|
55
|
Actin Is Crucial for All Kinetically Distinguishable Forms of Endocytosis at Synapses. Neuron 2016; 92:1020-1035. [PMID: 27840001 DOI: 10.1016/j.neuron.2016.10.014] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 06/16/2016] [Accepted: 10/04/2016] [Indexed: 01/18/2023]
Abstract
Mechanical force is needed to mediate endocytosis. Whether actin, the most abundant force-generating molecule, is essential for endocytosis is highly controversial in mammalian cells, particularly synapses, likely due to the use of actin blockers, the efficiency and specificity of which are often unclear in the studied cell. Here we addressed this issue using a knockout approach combined with measurements of membrane capacitance and fission pore conductance, imaging of vesicular protein endocytosis, and electron microscopy. We found that two actin isoforms, β- and γ-actin, are crucial for slow, rapid, bulk, and overshoot endocytosis at large calyx-type synapses, and for slow endocytosis and bulk endocytosis at small hippocampal synapses. Polymerized actin provides mechanical force to form endocytic pits. Actin also facilitates replenishment of the readily releasable vesicle pool, likely via endocytic clearance of active zones. We conclude that polymerized actin provides mechanical force essential for all kinetically distinguishable forms of endocytosis at synapses.
Collapse
|
56
|
Endosome-mediated endocytic mechanism replenishes the majority of synaptic vesicles at mature CNS synapses in an activity-dependent manner. Sci Rep 2016; 6:31807. [PMID: 27534442 PMCID: PMC4989163 DOI: 10.1038/srep31807] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 07/26/2016] [Indexed: 11/30/2022] Open
Abstract
Whether synaptic vesicles (SVs) are recovered via endosome-mediated pathways is a matter of debate; however, recent evidence suggests that clathrin-independent bulk endocytosis (CIE) via endosomes is functional and preferentially replenishes SV pools during strong stimulation. Here, using brefeldin-A (BFA) to block CIE, we found that CIE retrieved a minority of SVs at developing CNS synapses during strong stimulation, but its contribution increased up to 61% at mature CNS synapses. Contrary to previous views, BFA not only blocked SV formation from the endosome but also blocked the endosome formation at the plasma membrane. Adaptor protein 1 and 3 (AP-1/3) have key roles in SV reformation from endosomes during CIE, and AP-1 also affects bulk endosome formation from the plasma membrane. Finally, temporary blocking of chronic or acute neuronal activity with tetrodotoxin in mature neurons redirected most SV retrieval to endosome-independent pathways. These results show that during high neuronal activity, CIE becomes the major endocytic pathway at mature CNS synapses. Moreover, mature neurons use clathrin-mediated endocytosis and the CIE pathway to different extents depending on their previous activity; this may result in activity-dependent alterations of the SV composition which ultimately influence transmitter release and contribute to synaptic plasticity.
Collapse
|
57
|
Candiello E, Kratzke M, Wenzel D, Cassel D, Schu P. AP-1/σ1A and AP-1/σ1B adaptor-proteins differentially regulate neuronal early endosome maturation via the Rab5/Vps34-pathway. Sci Rep 2016; 6:29950. [PMID: 27411398 PMCID: PMC4944158 DOI: 10.1038/srep29950] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 06/24/2016] [Indexed: 12/26/2022] Open
Abstract
The σ1 subunit of the AP-1 clathrin-coated-vesicle adaptor-protein
complex is expressed as three isoforms. Tissues express σ1A and one of
the σ1B and σ1C isoforms. Brain is the tissue with the
highest σ1A and σ1B expression. σ1B-deficiency
leads to severe mental retardation, accumulation of early endosomes in synapses and
fewer synaptic vesicles, whose recycling is slowed down. AP-1/σ1A and
AP-1/σ1B regulate maturation of these early endosomes into
multivesicular body late endosomes, thereby controlling synaptic vesicle protein
transport into a degradative pathway. σ1A binds ArfGAP1, and with higher
affinity brain-specific ArfGAP1, which bind Rabex-5.
AP-1/σ1A-ArfGAP1-Rabex-5 complex formation leads to more endosomal
Rabex-5 and enhanced, Rab5GTP-stimulated Vps34 PI3-kinase activity,
which is essential for multivesicular body endosome formation. Formation of
AP-1/σ1A-ArfGAP1-Rabex-5 complexes is prevented by σ1B
binding of Rabex-5 and the amount of endosomal Rabex-5 is reduced. AP-1 complexes
differentially regulate endosome maturation and coordinate protein recycling and
degradation, revealing a novel molecular mechanism by which they regulate protein
transport besides their established function in clathrin-coated-vesicle
formation.
Collapse
Affiliation(s)
- Ermes Candiello
- Georg-August University Göttingen, Department for Cellular Biochemistry, Humboldtallee 23, D-37073 Göttingen, Germany
| | - Manuel Kratzke
- Georg-August University Göttingen, Department for Cellular Biochemistry, Humboldtallee 23, D-37073 Göttingen, Germany
| | - Dirk Wenzel
- Electron microscopy, Max-Planck-Institut for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany
| | - Dan Cassel
- Israel Institute of Technology, Department Biology, Haifa 32000, Israel
| | - Peter Schu
- Georg-August University Göttingen, Department for Cellular Biochemistry, Humboldtallee 23, D-37073 Göttingen, Germany
| |
Collapse
|
58
|
Cork KM, Van Hook MJ, Thoreson WB. Mechanisms, pools, and sites of spontaneous vesicle release at synapses of rod and cone photoreceptors. Eur J Neurosci 2016; 44:2015-27. [PMID: 27255664 DOI: 10.1111/ejn.13288] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Revised: 05/21/2016] [Accepted: 05/24/2016] [Indexed: 01/31/2023]
Abstract
Photoreceptors have depolarized resting potentials that stimulate calcium-dependent release continuously from a large vesicle pool but neurons can also release vesicles without stimulation. We characterized the Ca(2+) dependence, vesicle pools, and release sites involved in spontaneous release at photoreceptor ribbon synapses. In whole-cell recordings from light-adapted horizontal cells (HCs) of tiger salamander retina, we detected miniature excitatory post-synaptic currents (mEPSCs) when no stimulation was applied to promote exocytosis. Blocking Ca(2+) influx by lowering extracellular Ca(2+) , by application of Cd(2+) and other agents reduced the frequency of mEPSCs but did not eliminate them, indicating that mEPSCs can occur independently of Ca(2+) . We also measured release presynaptically from rods and cones by examining quantal glutamate transporter anion currents. Presynaptic quantal event frequency was reduced by Cd(2+) or by increased intracellular Ca(2+) buffering in rods, but not in cones, that were voltage clamped at -70 mV. By inhibiting the vesicle cycle with bafilomycin, we found the frequency of mEPSCs declined more rapidly than the amplitude of evoked excitatory post-synaptic currents (EPSCs) suggesting a possible separation between vesicle pools in evoked and spontaneous exocytosis. We mapped sites of Ca(2+) -independent release using total internal reflectance fluorescence (TIRF) microscopy to visualize fusion of individual vesicles loaded with dextran-conjugated pHrodo. Spontaneous release in rods occurred more frequently at non-ribbon sites than evoked release events. The function of Ca(2+) -independent spontaneous release at continuously active photoreceptor synapses remains unclear, but the low frequency of spontaneous quanta limits their impact on noise.
Collapse
Affiliation(s)
- Karlene M Cork
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, 4050 Durham Research Center, University of Nebraska Medical Center, Omaha, NE, 68198-5840, USA.,Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA
| | - Matthew J Van Hook
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, 4050 Durham Research Center, University of Nebraska Medical Center, Omaha, NE, 68198-5840, USA
| | - Wallace B Thoreson
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, 4050 Durham Research Center, University of Nebraska Medical Center, Omaha, NE, 68198-5840, USA.,Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA
| |
Collapse
|
59
|
Ghosh D, Pinto S, Danglot L, Vandewauw I, Segal A, Van Ranst N, Benoit M, Janssens A, Vennekens R, Vanden Berghe P, Galli T, Vriens J, Voets T. VAMP7 regulates constitutive membrane incorporation of the cold-activated channel TRPM8. Nat Commun 2016; 7:10489. [PMID: 26843440 PMCID: PMC4742910 DOI: 10.1038/ncomms10489] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 12/18/2015] [Indexed: 02/06/2023] Open
Abstract
The cation channel TRPM8 plays a central role in the somatosensory system, as a key sensor of innocuously cold temperatures and cooling agents. Although increased functional expression of TRPM8 has been implicated in various forms of pathological cold hypersensitivity, little is known about the cellular and molecular mechanisms that determine TRPM8 abundance at the plasma membrane. Here we demonstrate constitutive transport of TRPM8 towards the plasma membrane in atypical, non-acidic transport vesicles that contain lysosomal-associated membrane protein 1 (LAMP1), and provide evidence that vesicle-associated membrane protein 7 (VAMP7) mediates fusion of these vesicles with the plasma membrane. In line herewith, VAMP7-deficient mice exhibit reduced functional expression of TRPM8 in sensory neurons and concomitant deficits in cold avoidance and icilin-induced cold hypersensitivity. Our results uncover a cellular pathway that controls functional plasma membrane incorporation of a temperature-sensitive TRP channel, and thus regulates thermosensitivity in vivo.
Collapse
Affiliation(s)
- Debapriya Ghosh
- Laboratory of Ion Channel Research and TRP Channel Research Platform Leuven (TRPLe), Department of Cellular and Molecular Medicine, University of Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| | - Silvia Pinto
- Laboratory of Ion Channel Research and TRP Channel Research Platform Leuven (TRPLe), Department of Cellular and Molecular Medicine, University of Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| | - Lydia Danglot
- Institut Jacques Monod, CNRS UMR 7592, University of Paris Diderot, F-75013 Paris, France
- INSERM ERL U950, Membrane Traffic in Health & disease Group, F-75013 Paris, France
| | - Ine Vandewauw
- Laboratory of Ion Channel Research and TRP Channel Research Platform Leuven (TRPLe), Department of Cellular and Molecular Medicine, University of Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| | - Andrei Segal
- Laboratory of Ion Channel Research and TRP Channel Research Platform Leuven (TRPLe), Department of Cellular and Molecular Medicine, University of Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| | - Nele Van Ranst
- Laboratory of Ion Channel Research and TRP Channel Research Platform Leuven (TRPLe), Department of Cellular and Molecular Medicine, University of Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| | - Melissa Benoit
- Laboratory of Ion Channel Research and TRP Channel Research Platform Leuven (TRPLe), Department of Cellular and Molecular Medicine, University of Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| | - Annelies Janssens
- Laboratory of Ion Channel Research and TRP Channel Research Platform Leuven (TRPLe), Department of Cellular and Molecular Medicine, University of Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| | - Rudi Vennekens
- Laboratory of Ion Channel Research and TRP Channel Research Platform Leuven (TRPLe), Department of Cellular and Molecular Medicine, University of Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| | - Pieter Vanden Berghe
- Laboratory for Enteric NeuroScience, Department of Clinical and Experimental Medicine, University of Leuven, B-3000 Leuven, Belgium
- Translational Research Centre for Gastrointestinal Disorders, KU Leuven, Herestraat 49 box 701, B-3000 Leuven, Belgium
| | - Thierry Galli
- Institut Jacques Monod, CNRS UMR 7592, University of Paris Diderot, F-75013 Paris, France
- INSERM ERL U950, Membrane Traffic in Health & disease Group, F-75013 Paris, France
| | - Joris Vriens
- Laboratory of Ion Channel Research and TRP Channel Research Platform Leuven (TRPLe), Department of Cellular and Molecular Medicine, University of Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
- Laboratory of Experimental Gynaecology, Department of Development and Regeneration, University of Leuven, Herestraat 49 box 611, B-3000 Leuven, Belgium
| | - Thomas Voets
- Laboratory of Ion Channel Research and TRP Channel Research Platform Leuven (TRPLe), Department of Cellular and Molecular Medicine, University of Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| |
Collapse
|
60
|
Harper CB, Papadopulos A, Martin S, Matthews DR, Morgan GP, Nguyen TH, Wang T, Nair D, Choquet D, Meunier FA. Botulinum neurotoxin type-A enters a non-recycling pool of synaptic vesicles. Sci Rep 2016; 6:19654. [PMID: 26805017 PMCID: PMC4726273 DOI: 10.1038/srep19654] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 11/20/2015] [Indexed: 02/03/2023] Open
Abstract
Neuronal communication relies on synaptic vesicles undergoing regulated exocytosis and recycling for multiple rounds of fusion. Whether all synaptic vesicles have identical protein content has been challenged, suggesting that their recycling ability may differ greatly. Botulinum neurotoxin type-A (BoNT/A) is a highly potent neurotoxin that is internalized in synaptic vesicles at motor nerve terminals and induces flaccid paralysis. Recently, BoNT/A was also shown to undergo retrograde transport, suggesting it might enter a specific pool of synaptic vesicles with a retrograde trafficking fate. Using high-resolution microscopy techniques including electron microscopy and single molecule imaging, we found that the BoNT/A binding domain is internalized within a subset of vesicles that only partially co-localize with cholera toxin B-subunit and have markedly reduced VAMP2 immunoreactivity. Synaptic vesicles loaded with pHrodo-BoNT/A-Hc exhibited a significantly reduced ability to fuse with the plasma membrane in mouse hippocampal nerve terminals when compared with pHrodo-dextran-containing synaptic vesicles and pHrodo-labeled anti-GFP nanobodies bound to VAMP2-pHluorin or vGlut-pHluorin. Similar results were also obtained at the amphibian neuromuscular junction. These results reveal that BoNT/A is internalized in a subpopulation of synaptic vesicles that are not destined to recycle, highlighting the existence of significant molecular and functional heterogeneity between synaptic vesicles.
Collapse
Affiliation(s)
- Callista B Harper
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| | - Andreas Papadopulos
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| | - Sally Martin
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| | - Daniel R Matthews
- The University of Queensland, Queensland Brain Institute, Brisbane, Queensland 4072, Australia
| | - Garry P Morgan
- The University of Queensland, Centre for Microscopy and Microanalysis, Brisbane, Queensland 4072, Australia
| | - Tam H Nguyen
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| | - Tong Wang
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| | - Deepak Nair
- Interdisciplinary Institute for Neuroscience, The University of Bordeaux, Bordeaux, 33000, France.,Centre for Neuroscience, Indian Institute of Science, Bangalore, 560012, India
| | - Daniel Choquet
- Interdisciplinary Institute for Neuroscience, The University of Bordeaux, Bordeaux, 33000, France
| | - Frederic A Meunier
- The University of Queensland, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, Brisbane, Queensland 4072, Australia
| |
Collapse
|
61
|
Chamberland S, Tóth K. Functionally heterogeneous synaptic vesicle pools support diverse synaptic signalling. J Physiol 2015; 594:825-35. [PMID: 26614712 DOI: 10.1113/jp270194] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Accepted: 11/23/2015] [Indexed: 12/15/2022] Open
Abstract
Synaptic communication between neurons is a highly dynamic process involving specialized structures. At the level of the presynaptic terminal, neurotransmission is ensured by fusion of vesicles to the membrane, which releases neurotransmitter in the synaptic cleft. Depending on the level of activity experienced by the terminal, the spatiotemporal properties of calcium invasion will dictate the timing and the number of vesicles that need to be released. Diverse presynaptic firing patterns are translated to neurotransmitter release with a distinct temporal feature. Complex patterns of neurotransmitter release can be achieved when different vesicles respond to distinct calcium dynamics in the presynaptic terminal. Specific vesicles from different pools are recruited during various modes of release as the particular molecular composition of their membrane proteins define their functional properties. Such diversity endows the presynaptic terminal with the ability to respond to distinct physiological signals via the mobilization of specific subpopulation of vesicles. There are several mechanisms by which a diverse vesicle population could be generated in single presynaptic terminals, including distinct recycling pathways that utilize various adaptor proteins. Several additional factors could potentially contribute to the development of a heterogeneous vesicle pool such as specialized release sites, spatial segregation within the terminal and specialized delivery pathways. Among these factors molecular heterogeneity plays a central role in defining the functional properties of different subpopulations of vesicles.
Collapse
Affiliation(s)
- Simon Chamberland
- Quebec Mental Health Institute, Department of Psychiatry and Neuroscience, Université Laval, Quebec City, Quebec, Canada, G1J 2G3
| | - Katalin Tóth
- Quebec Mental Health Institute, Department of Psychiatry and Neuroscience, Université Laval, Quebec City, Quebec, Canada, G1J 2G3
| |
Collapse
|
62
|
Crawford DC, Kavalali ET. Molecular underpinnings of synaptic vesicle pool heterogeneity. Traffic 2015; 16:338-64. [PMID: 25620674 DOI: 10.1111/tra.12262] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 01/06/2015] [Indexed: 12/31/2022]
Abstract
Neuronal communication relies on chemical synaptic transmission for information transfer and processing. Chemical neurotransmission is initiated by synaptic vesicle fusion with the presynaptic active zone resulting in release of neurotransmitters. Classical models have assumed that all synaptic vesicles within a synapse have the same potential to fuse under different functional contexts. In this model, functional differences among synaptic vesicle populations are ascribed to their spatial distribution in the synapse with respect to the active zone. Emerging evidence suggests, however, that synaptic vesicles are not a homogenous population of organelles, and they possess intrinsic molecular differences and differential interaction partners. Recent studies have reported a diverse array of synaptic molecules that selectively regulate synaptic vesicles' ability to fuse synchronously and asynchronously in response to action potentials or spontaneously irrespective of action potentials. Here we discuss these molecular mediators of vesicle pool heterogeneity that are found on the synaptic vesicle membrane, on the presynaptic plasma membrane, or within the cytosol and consider some of the functional consequences of this diversity. This emerging molecular framework presents novel avenues to probe synaptic function and uncover how synaptic vesicle pools impact neuronal signaling.
Collapse
Affiliation(s)
- Devon C Crawford
- Department of Neuroscience, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9111, USA
| | | |
Collapse
|
63
|
Nicholson-Fish JC, Kokotos AC, Gillingwater TH, Smillie KJ, Cousin MA. VAMP4 Is an Essential Cargo Molecule for Activity-Dependent Bulk Endocytosis. Neuron 2015; 88:973-984. [PMID: 26607000 PMCID: PMC4678114 DOI: 10.1016/j.neuron.2015.10.043] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 09/22/2015] [Accepted: 10/15/2015] [Indexed: 11/23/2022]
Abstract
The accurate formation of synaptic vesicles (SVs) and incorporation of their protein cargo during endocytosis is critical for the maintenance of neurotransmission. During intense neuronal activity, a transient and acute accumulation of SV cargo occurs at the plasma membrane. Activity-dependent bulk endocytosis (ADBE) is the dominant SV endocytosis mode under these conditions; however, it is currently unknown how ADBE mediates cargo retrieval. We examined the retrieval of different SV cargo molecules during intense stimulation using a series of genetically encoded pH-sensitive reporters in neuronal cultures. The retrieval of only one reporter, VAMP4-pHluorin, was perturbed by inhibiting ADBE. This selective recovery was confirmed by the enrichment of endogenous VAMP4 in purified bulk endosomes formed by ADBE. VAMP4 was also essential for ADBE, with a cytoplasmic di-leucine motif being critical for this role. Therefore, VAMP4 is the first identified ADBE cargo and is essential for this endocytosis mode to proceed. VAMP4 is the first identified ADBE cargo VAMP4 is essential for ADBE Most synaptic vesicle cargoes are not selectively recovered by ADBE
Collapse
Affiliation(s)
- Jessica C Nicholson-Fish
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland
| | - Alexandros C Kokotos
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland
| | - Thomas H Gillingwater
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland
| | - Karen J Smillie
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland.
| | - Michael A Cousin
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland.
| |
Collapse
|
64
|
Werner C, Pauli M, Doose S, Weishaupt A, Haselmann H, Grünewald B, Sauer M, Heckmann M, Toyka KV, Asan E, Sommer C, Geis C. Human autoantibodies to amphiphysin induce defective presynaptic vesicle dynamics and composition. Brain 2015; 139:365-79. [DOI: 10.1093/brain/awv324] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 09/25/2015] [Indexed: 12/16/2022] Open
Abstract
Abstract
See Irani (doi:10.1093/awv364) for a scientific commentary on this article.
Stiff-person syndrome is the prototype of a central nervous system disorder with autoantibodies targeting presynaptic antigens. Patients with paraneoplastic stiff-person syndrome may harbour autoantibodies to the BAR (Bin/Amphiphysin/Rvs) domain protein amphiphysin, which target its SH3 domain. These patients have neurophysiological signs of compromised central inhibition and respond to symptomatic treatment with medication enhancing GABAergic transmission. High frequency neurotransmission as observed in tonic GABAergic interneurons relies on fast exocytosis of neurotransmitters based on compensatory endocytosis. As amphiphysin is involved in clathrin-mediated endocytosis, patient autoantibodies are supposed to interfere with this function, leading to disinhibition by reduction of GABAergic neurotransmission. We here investigated the effects of human anti-amphiphysin autoantibodies on structural components of presynaptic boutons ex vivo and in vitro using electron microscopy and super-resolution direct stochastic optical reconstruction microscopy. Ultrastructural analysis of spinal cord presynaptic boutons was performed after in vivo intrathecal passive transfer of affinity-purified human anti-amphiphysin autoantibodies in rats and revealed signs of markedly disabled clathrin-mediated endocytosis. This was unmasked at high synaptic activity and characterized by a reduction of the presynaptic vesicle pool, clathrin coated intermediates, and endosome-like structures. Super-resolution microscopy of inhibitory GABAergic presynaptic boutons in primary neurons revealed that specific human anti-amphiphysin immunoglobulin G induced an increase of the essential vesicular protein synaptobrevin 2 and a reduction of synaptobrevin 7. This constellation suggests depletion of resting pool vesicles and trapping of releasable pool vesicular proteins at the plasma membrane. Similar effects were found in amphiphysin-deficient neurons from knockout mice. Application of specific patient antibodies did not show additional effects. Blocking alternative pathways of clathrin-independent endocytosis with brefeldin A reversed the autoantibody induced effects on molecular vesicle composition. Endophilin as an interaction partner of amphiphysin showed reduced clustering within presynaptic terminals. Collectively, these results point towards an autoantibody-induced structural disorganization in GABAergic synapses with profound changes in presynaptic vesicle pools, activation of alternative endocytic pathways, and potentially compensatory rearrangement of proteins involved in clathrin-mediated endocytosis. Our findings provide novel insights into synaptic pathomechanisms in a prototypic antibody-mediated central nervous system disease, which may serve as a proof-of-principle example in this evolving group of autoimmune disorders associated with autoantibodies to synaptic antigens.
Collapse
Affiliation(s)
- Christian Werner
- 1 Hans-Berger Department of Neurology, Jena University Hospital, Erlanger Allee 101, 07747 Jena, Germany
- 2 Department of Neurology, University of Würzburg, Josef-Schneider Str. 11, 97080 Würzburg, Germany
| | - Martin Pauli
- 3 Department of Neurophysiology, Institute of Physiology, University of Würzburg, Roentgenring 9, 97070 Würzburg, Germany
| | - Sören Doose
- 4 Department of Biotechnology and Biophysics, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Andreas Weishaupt
- 2 Department of Neurology, University of Würzburg, Josef-Schneider Str. 11, 97080 Würzburg, Germany
| | - Holger Haselmann
- 1 Hans-Berger Department of Neurology, Jena University Hospital, Erlanger Allee 101, 07747 Jena, Germany
- 2 Department of Neurology, University of Würzburg, Josef-Schneider Str. 11, 97080 Würzburg, Germany
- 5 Center for Sepsis Control and Care (CSCC), Jena University Hospital, Erlanger Allee 101, 07747 Jena, Germany
| | - Benedikt Grünewald
- 1 Hans-Berger Department of Neurology, Jena University Hospital, Erlanger Allee 101, 07747 Jena, Germany
- 2 Department of Neurology, University of Würzburg, Josef-Schneider Str. 11, 97080 Würzburg, Germany
- 5 Center for Sepsis Control and Care (CSCC), Jena University Hospital, Erlanger Allee 101, 07747 Jena, Germany
| | - Markus Sauer
- 4 Department of Biotechnology and Biophysics, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Manfred Heckmann
- 3 Department of Neurophysiology, Institute of Physiology, University of Würzburg, Roentgenring 9, 97070 Würzburg, Germany
| | - Klaus V. Toyka
- 2 Department of Neurology, University of Würzburg, Josef-Schneider Str. 11, 97080 Würzburg, Germany
| | - Esther Asan
- 6 Institute for Anatomy and Cell Biology, University of Würzburg, Koellikerstrasse 6, 97070 Würzburg, Germany
| | - Claudia Sommer
- 2 Department of Neurology, University of Würzburg, Josef-Schneider Str. 11, 97080 Würzburg, Germany
| | - Christian Geis
- 1 Hans-Berger Department of Neurology, Jena University Hospital, Erlanger Allee 101, 07747 Jena, Germany
- 2 Department of Neurology, University of Würzburg, Josef-Schneider Str. 11, 97080 Würzburg, Germany
- 5 Center for Sepsis Control and Care (CSCC), Jena University Hospital, Erlanger Allee 101, 07747 Jena, Germany
| |
Collapse
|
65
|
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins constitute the core membrane fusion machinery of intracellular transport and intercellular communication. A little more than ten years ago, it was proposed that the long N-terminal domain of a subset of SNAREs, henceforth called the longin domain, could be a crucial regulator with multiple functions in membrane trafficking. Structural, biochemical and cell biology studies have now produced a large set of data that support this hypothesis and indicate a role for the longin domain in regulating the sorting and activity of SNAREs. Here, we review the first decade of structure-function data on the three prototypical longin SNAREs: Ykt6, VAMP7 and Sec22b. We will, in particular, highlight the conserved molecular mechanisms that allow longin domains to fold back onto the fusion-inducing SNARE coiled-coil domain, thereby inhibiting membrane fusion, and describe the interactions of longin SNAREs with proteins that regulate their intracellular sorting. This dual function of the longin domain in regulating both the membrane localization and membrane fusion activity of SNAREs points to its role as a key regulatory module of intracellular trafficking.
Collapse
Affiliation(s)
- Frédéric Daste
- Université Paris Diderot, Sorbonne Paris Cité, Institut Jacques Monod, CNRS UMR 7592, Membrane Traffic in Health & Disease, INSERM ERL U950, Paris F-75013, France
| | - Thierry Galli
- Université Paris Diderot, Sorbonne Paris Cité, Institut Jacques Monod, CNRS UMR 7592, Membrane Traffic in Health & Disease, INSERM ERL U950, Paris F-75013, France
| | - David Tareste
- Université Paris Diderot, Sorbonne Paris Cité, Institut Jacques Monod, CNRS UMR 7592, Membrane Traffic in Health & Disease, INSERM ERL U950, Paris F-75013, France
| |
Collapse
|
66
|
Rey SA, Smith CA, Fowler MW, Crawford F, Burden JJ, Staras K. Ultrastructural and functional fate of recycled vesicles in hippocampal synapses. Nat Commun 2015; 6:8043. [PMID: 26292808 PMCID: PMC4560786 DOI: 10.1038/ncomms9043] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 07/11/2015] [Indexed: 12/24/2022] Open
Abstract
Efficient recycling of synaptic vesicles is thought to be critical for sustained information transfer at central terminals. However, the specific contribution that retrieved vesicles make to future transmission events remains unclear. Here we exploit fluorescence and time-stamped electron microscopy to track the functional and positional fate of vesicles endocytosed after readily releasable pool (RRP) stimulation in rat hippocampal synapses. We show that most vesicles are recovered near the active zone but subsequently take up random positions in the cluster, without preferential bias for future use. These vesicles non-selectively queue, advancing towards the release site with further stimulation in an actin-dependent manner. Nonetheless, the small subset of vesicles retrieved recently in the stimulus train persist nearer the active zone and exhibit more privileged use in the next RRP. Our findings reveal heterogeneity in vesicle fate based on nanoscale position and timing rules, providing new insights into the origins of future pool constitution.
Collapse
Affiliation(s)
- Stephanie A Rey
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK
| | | | - Milena W Fowler
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK
| | - Freya Crawford
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK
| | - Jemima J Burden
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Kevin Staras
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK
| |
Collapse
|
67
|
The structure and function of presynaptic endosomes. Exp Cell Res 2015; 335:172-9. [DOI: 10.1016/j.yexcr.2015.04.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 04/23/2015] [Indexed: 11/19/2022]
|
68
|
Pathak D, Shields LY, Mendelsohn BA, Haddad D, Lin W, Gerencser AA, Kim H, Brand MD, Edwards RH, Nakamura K. The role of mitochondrially derived ATP in synaptic vesicle recycling. J Biol Chem 2015; 290:22325-36. [PMID: 26126824 DOI: 10.1074/jbc.m115.656405] [Citation(s) in RCA: 177] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Indexed: 01/03/2023] Open
Abstract
Synaptic mitochondria are thought to be critical in supporting neuronal energy requirements at the synapse, and bioenergetic failure at the synapse may impair neural transmission and contribute to neurodegeneration. However, little is known about the energy requirements of synaptic vesicle release or whether these energy requirements go unmet in disease, primarily due to a lack of appropriate tools and sensitive assays. To determine the dependence of synaptic vesicle cycling on mitochondrially derived ATP levels, we developed two complementary assays sensitive to mitochondrially derived ATP in individual, living hippocampal boutons. The first is a functional assay for mitochondrially derived ATP that uses the extent of synaptic vesicle cycling as a surrogate for ATP level. The second uses ATP FRET sensors to directly measure ATP at the synapse. Using these assays, we show that endocytosis has high ATP requirements and that vesicle reacidification and exocytosis require comparatively little energy. We then show that to meet these energy needs, mitochondrially derived ATP is rapidly dispersed in axons, thereby maintaining near normal levels of ATP even in boutons lacking mitochondria. As a result, the capacity for synaptic vesicle cycling is similar in boutons without mitochondria as in those with mitochondria. Finally, we show that loss of a key respiratory subunit implicated in Leigh disease markedly decreases mitochondrially derived ATP levels in axons, thus inhibiting synaptic vesicle cycling. This proves that mitochondria-based energy failure can occur and be detected in individual neurons that have a genetic mitochondrial defect.
Collapse
Affiliation(s)
- Divya Pathak
- From the Gladstone Institute of Neurological Disease, San Francisco, California 94158
| | - Lauren Y Shields
- From the Gladstone Institute of Neurological Disease, San Francisco, California 94158, the Department of Neurology and Graduate Programs in Neuroscience and Biomedical Sciences, University of California at San Francisco, San Francisco, California 94158
| | - Bryce A Mendelsohn
- From the Gladstone Institute of Neurological Disease, San Francisco, California 94158, the Department of Pediatrics, University of California at San Francisco, San Francisco, California 94143, and
| | - Dominik Haddad
- From the Gladstone Institute of Neurological Disease, San Francisco, California 94158
| | - Wei Lin
- From the Gladstone Institute of Neurological Disease, San Francisco, California 94158
| | - Akos A Gerencser
- the Buck Institute for Research on Aging, Novato, California 94945
| | - Hwajin Kim
- From the Gladstone Institute of Neurological Disease, San Francisco, California 94158
| | - Martin D Brand
- the Buck Institute for Research on Aging, Novato, California 94945
| | - Robert H Edwards
- the Department of Neurology and Graduate Programs in Neuroscience and Biomedical Sciences, University of California at San Francisco, San Francisco, California 94158
| | - Ken Nakamura
- From the Gladstone Institute of Neurological Disease, San Francisco, California 94158, the Department of Neurology and Graduate Programs in Neuroscience and Biomedical Sciences, University of California at San Francisco, San Francisco, California 94158,
| |
Collapse
|
69
|
Di Giovanni J, Sheng ZH. Regulation of synaptic activity by snapin-mediated endolysosomal transport and sorting. EMBO J 2015; 34:2059-77. [PMID: 26108535 DOI: 10.15252/embj.201591125] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 05/29/2015] [Indexed: 11/09/2022] Open
Abstract
Recycling synaptic vesicles (SVs) transit through early endosomal sorting stations, which raises a fundamental question: are SVs sorted toward endolysosomal pathways? Here, we used snapin mutants as tools to assess how endolysosomal sorting and trafficking impact presynaptic activity in wild-type and snapin(-/-) neurons. Snapin acts as a dynein adaptor that mediates the retrograde transport of late endosomes (LEs) and interacts with dysbindin, a subunit of the endosomal sorting complex BLOC-1. Expressing dynein-binding defective snapin mutants induced SV accumulation at presynaptic terminals, mimicking the snapin(-/-) phenotype. Conversely, over-expressing snapin reduced SV pool size by enhancing SV trafficking to the endolysosomal pathway. Using a SV-targeted Ca(2+) sensor, we demonstrate that snapin-dysbindin interaction regulates SV positional priming through BLOC-1/AP-3-dependent sorting. Our study reveals a bipartite regulation of presynaptic activity by endolysosomal trafficking and sorting: LE transport regulates SV pool size, and BLOC-1/AP-3-dependent sorting fine-tunes the Ca(2+) sensitivity of SV release. Therefore, our study provides new mechanistic insights into the maintenance and regulation of SV pool size and synchronized SV fusion through snapin-mediated LE trafficking and endosomal sorting.
Collapse
Affiliation(s)
- Jerome Di Giovanni
- Synaptic Functions Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Zu-Hang Sheng
- Synaptic Functions Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| |
Collapse
|
70
|
Morton A, Marland JRK, Cousin MA. Synaptic vesicle exocytosis and increased cytosolic calcium are both necessary but not sufficient for activity-dependent bulk endocytosis. J Neurochem 2015; 134:405-15. [PMID: 25913068 PMCID: PMC4950031 DOI: 10.1111/jnc.13132] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 03/23/2015] [Accepted: 03/30/2015] [Indexed: 01/22/2023]
Abstract
Activity‐dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle (SV) endocytosis mode in central nerve terminals during intense neuronal activity. By definition this mode is triggered by neuronal activity; however, key questions regarding its mechanism of activation remain unaddressed. To determine the basic requirements for ADBE triggering in central nerve terminals, we decoupled SV fusion events from activity‐dependent calcium influx using either clostridial neurotoxins or buffering of intracellular calcium. ADBE was monitored both optically and morphologically by observing uptake of the fluid phase markers tetramethylrhodamine‐dextran and horse radish peroxidase respectively. Ablation of SV fusion with tetanus toxin resulted in the arrest of ADBE, but had no effect on other calcium‐dependent events such as activity‐dependent dynamin I dephosphorylation, indicating that SV exocytosis is necessary for triggering. Furthermore, the calcium chelator EGTA abolished ADBE while leaving SV exocytosis intact, demonstrating that ADBE is triggered by intracellular free calcium increases outside the active zone. Activity‐dependent dynamin I dephosphorylation was also arrested in EGTA‐treated neurons, consistent with its proposed role in triggering ADBE. Thus, SV fusion and increased cytoplasmic free calcium are both necessary but not sufficient individually to trigger ADBE.![]() Activity‐dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle (SV) endocytosis mode in central nerve terminals during intense neuronal activity. To determine the minimal requirements for ADBE triggering, we decoupled SV fusion events from activity‐dependent calcium influx using either clostridial neurotoxins or buffering of intracellular calcium. We found that SV fusion and increased cytoplasmic free calcium are both necessary but not sufficient to trigger ADBE.
Collapse
Affiliation(s)
- Andrew Morton
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland
| | - Jamie R K Marland
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland
| | - Michael A Cousin
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland
| |
Collapse
|
71
|
Dynamin-related protein 1 is required for normal mitochondrial bioenergetic and synaptic function in CA1 hippocampal neurons. Cell Death Dis 2015; 6:e1725. [PMID: 25880092 PMCID: PMC4650558 DOI: 10.1038/cddis.2015.94] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 02/15/2015] [Accepted: 03/02/2015] [Indexed: 12/11/2022]
Abstract
Disrupting particular mitochondrial fission and fusion proteins leads to the death of specific neuronal populations; however, the normal functions of mitochondrial fission in neurons are poorly understood, especially in vivo, which limits the understanding of mitochondrial changes in disease. Altered activity of the central mitochondrial fission protein dynamin-related protein 1 (Drp1) may contribute to the pathophysiology of several neurologic diseases. To study Drp1 in a neuronal population affected by Alzheimer's disease (AD), stroke, and seizure disorders, we postnatally deleted Drp1 from CA1 and other forebrain neurons in mice (CamKII-Cre, Drp1lox/lox (Drp1cKO)). Although most CA1 neurons survived for more than 1 year, their synaptic transmission was impaired, and Drp1cKO mice had impaired memory. In Drp1cKO cell bodies, we observed marked mitochondrial swelling but no change in the number of mitochondria in individual synaptic terminals. Using ATP FRET sensors, we found that cultured neurons lacking Drp1 (Drp1KO) could not maintain normal levels of mitochondrial-derived ATP when energy consumption was increased by neural activity. These deficits occurred specifically at the nerve terminal, but not the cell body, and were sufficient to impair synaptic vesicle cycling. Although Drp1KO increased the distance between axonal mitochondria, mitochondrial-derived ATP still decreased similarly in Drp1KO boutons with and without mitochondria. This indicates that mitochondrial-derived ATP is rapidly dispersed in Drp1KO axons, and that the deficits in axonal bioenergetics and function are not caused by regional energy gradients. Instead, loss of Drp1 compromises the intrinsic bioenergetic function of axonal mitochondria, thus revealing a mechanism by which disrupting mitochondrial dynamics can cause dysfunction of axons.
Collapse
|
72
|
Synaptic vesicle pools: Principles, properties and limitations. Exp Cell Res 2015; 335:150-6. [PMID: 25814361 DOI: 10.1016/j.yexcr.2015.03.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 03/14/2015] [Indexed: 11/21/2022]
|
73
|
Abstract
Fast synaptic communication in the brain requires synchronous vesicle fusion that is evoked by action potential-induced Ca(2+) influx. However, synaptic terminals also release neurotransmitters by spontaneous vesicle fusion, which is independent of presynaptic action potentials. A functional role for spontaneous neurotransmitter release events in the regulation of synaptic plasticity and homeostasis, as well as the regulation of certain behaviours, has been reported. In addition, there is evidence that the presynaptic mechanisms underlying spontaneous release of neurotransmitters and their postsynaptic targets are segregated from those of evoked neurotransmission. These findings challenge current assumptions about neuronal signalling and neurotransmission, as they indicate that spontaneous neurotransmission has an autonomous role in interneuronal communication that is distinct from that of evoked release.
Collapse
|
74
|
Kononenko N, Haucke V. Molecular Mechanisms of Presynaptic Membrane Retrieval and Synaptic Vesicle Reformation. Neuron 2015; 85:484-96. [DOI: 10.1016/j.neuron.2014.12.016] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
75
|
Abstract
Disruptions in mitochondrial dynamics may contribute to the selective degeneration of dopamine (DA) neurons in Parkinson's disease (PD). However, little is known about the normal functions of mitochondrial dynamics in these neurons, especially in axons where degeneration begins, and this makes it difficult to understand the disease process. To study one aspect of mitochondrial dynamics-mitochondrial fission-in mouse DA neurons, we deleted the central fission protein dynamin-related protein 1 (Drp1). Drp1 loss rapidly eliminates the DA terminals in the caudate-putamen and causes cell bodies in the midbrain to degenerate and lose α-synuclein. Without Drp1, mitochondrial mass dramatically decreases, especially in axons, where the mitochondrial movement becomes uncoordinated. However, in the ventral tegmental area (VTA), a subset of midbrain DA neurons characterized by small hyperpolarization-activated cation currents (Ih) is spared, despite near complete loss of their axonal mitochondria. Drp1 is thus critical for targeting mitochondria to the nerve terminal, and a disruption in mitochondrial fission can contribute to the preferential death of nigrostriatal DA neurons.
Collapse
|
76
|
A nanoscale resolution view on synaptic vesicle dynamics. Synapse 2014; 69:256-67. [DOI: 10.1002/syn.21795] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 11/20/2014] [Accepted: 11/27/2014] [Indexed: 12/31/2022]
|
77
|
Truckenbrodt S, Rizzoli SO. Spontaneous vesicle recycling in the synaptic bouton. Front Cell Neurosci 2014; 8:409. [PMID: 25538561 PMCID: PMC4259163 DOI: 10.3389/fncel.2014.00409] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 11/11/2014] [Indexed: 11/13/2022] Open
Abstract
The trigger for synaptic vesicle exocytosis is Ca2+, which enters the synaptic bouton following action potential stimulation. However, spontaneous release of neurotransmitter also occurs in the absence of stimulation in virtually all synaptic boutons. It has long been thought that this represents exocytosis driven by fluctuations in local Ca2+ levels. The vesicles responding to these fluctuations are thought to be the same ones that release upon stimulation, albeit potentially triggered by different Ca2+ sensors. This view has been challenged by several recent works, which have suggested that spontaneous release is driven by a separate pool of synaptic vesicles. Numerous articles appeared during the last few years in support of each of these hypotheses, and it has been challenging to bring them into accord. We speculate here on the origins of this controversy, and propose a solution that is related to developmental effects. Constitutive membrane traffic, needed for the biogenesis of vesicles and synapses, is responsible for high levels of spontaneous membrane fusion in young neurons, probably independent of Ca2+. The vesicles releasing spontaneously in such neurons are not related to other synaptic vesicle pools and may represent constitutively releasing vesicles (CRVs) rather than bona fide synaptic vesicles. In mature neurons, constitutive traffic is much dampened, and the few remaining spontaneous release events probably represent bona fide spontaneously releasing synaptic vesicles (SRSVs) responding to Ca2+ fluctuations, along with a handful of CRVs that participate in synaptic vesicle turnover.
Collapse
Affiliation(s)
- Sven Truckenbrodt
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, European Neuroscience Institute, Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain Göttingen, Germany ; International Max Planck Research School for Molecular Biology Göttingen, Germany
| | - Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, European Neuroscience Institute, Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain Göttingen, Germany
| |
Collapse
|
78
|
Kokotos AC, Cousin MA. Synaptic vesicle generation from central nerve terminal endosomes. Traffic 2014; 16:229-40. [PMID: 25346420 DOI: 10.1111/tra.12235] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 10/15/2014] [Accepted: 10/20/2014] [Indexed: 01/01/2023]
Abstract
Central nerve terminals contain a small number of synaptic vesicles (SVs) that must sustain the fidelity of neurotransmission across a wide range of stimulation intensities. For this to be achieved, nerve terminals integrate a number of complementary endocytosis modes whose activation spans the breadth of these neuronal stimulation patterns. Two such modes are ultrafast endocytosis and activity-dependent bulk endocytosis, which are triggered by stimuli at either end of the physiological range. Both endocytosis modes generate endosomes directly from the nerve terminal plasma membrane, before the subsequent production of SVs from these structures. This review will discuss the current knowledge relating to the molecular mechanisms involved in the generation of SVs from nerve terminal endosomes, how this relates to other mechanisms of SV production and the functional role of such SVs.
Collapse
Affiliation(s)
- Alexandros C Kokotos
- Centre for Integrative Physiology, George Square, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | | |
Collapse
|
79
|
Leitz J, Kavalali ET. Fast retrieval and autonomous regulation of single spontaneously recycling synaptic vesicles. eLife 2014; 3:e03658. [PMID: 25415052 PMCID: PMC4270043 DOI: 10.7554/elife.03658] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 11/21/2014] [Indexed: 11/13/2022] Open
Abstract
Presynaptic terminals release neurotransmitters spontaneously in a manner that can be regulated by Ca(2+). However, the mechanisms underlying this regulation are poorly understood because the inherent stochasticity and low probability of spontaneous fusion events has curtailed their visualization at individual release sites. Here, using pH-sensitive optical probes targeted to synaptic vesicles, we visualized single spontaneous fusion events and found that they are retrieved extremely rapidly with faster re-acidification kinetics than their action potential-evoked counterparts. These fusion events were coupled to postsynaptic NMDA receptor-driven Ca(2+) signals, and at elevated Ca(2+) concentrations there was an increase in the number of vesicles that would undergo fusion. Furthermore, spontaneous vesicle fusion propensity in a synapse was Ca(2+)-dependent but regulated autonomously: independent of evoked fusion probability at the same synapse. Taken together, these results expand classical quantal analysis to incorporate endocytic and exocytic phases of single fusion events and uncover autonomous regulation of spontaneous fusion.
Collapse
Affiliation(s)
- Jeremy Leitz
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, United States
| | - Ege T Kavalali
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States
| |
Collapse
|
80
|
Evstratova A, Chamberland S, Faundez V, Tóth K. Vesicles derived via AP-3-dependent recycling contribute to asynchronous release and influence information transfer. Nat Commun 2014; 5:5530. [PMID: 25410111 PMCID: PMC4239664 DOI: 10.1038/ncomms6530] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 10/10/2014] [Indexed: 12/21/2022] Open
Abstract
Action potentials trigger synchronous and asynchronous neurotransmitter release. Temporal properties of both types of release could be altered in an activity-dependent manner. While the effects of activity-dependent changes in synchronous release on postsynaptic signal integration have been studied, the contribution of asynchronous release to information transfer during natural stimulus patterns is unknown. Here we find that during trains of stimulations, asynchronous release contributes to the precision of action potential firing. Our data show that this form of release is selectively diminished in AP-3b2 KO animals, which lack functional neuronal AP-3, an adaptor protein regulating vesicle formation from endosomes generated during bulk endocytosis. We find that in the absence of neuronal AP-3, asynchronous release is attenuated and the activity-dependent increase in the precision of action potential timing is compromised. Lack of asynchronous release decreases the capacity of synaptic information transfer and renders synaptic communication less reliable in response to natural stimulus patterns.
Collapse
Affiliation(s)
- Alesya Evstratova
- Department of Psychiatry and Neuroscience, Quebec Mental Health Institute, Université Laval, Quebec City, Quebec, Canada G1J 2G3
| | - Simon Chamberland
- Department of Psychiatry and Neuroscience, Quebec Mental Health Institute, Université Laval, Quebec City, Quebec, Canada G1J 2G3
| | - Victor Faundez
- Department of Cell Biology, Emory University, Atlanta, Georgia 30322, USA
| | - Katalin Tóth
- Department of Psychiatry and Neuroscience, Quebec Mental Health Institute, Université Laval, Quebec City, Quebec, Canada G1J 2G3
| |
Collapse
|
81
|
Ramirez DMO, Kavalali ET. The role of non-canonical SNAREs in synaptic vesicle recycling. CELLULAR LOGISTICS 2014; 2:20-27. [PMID: 22645707 PMCID: PMC3355972 DOI: 10.4161/cl.20114] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
An increasing number of studies suggest that distinct pools of synaptic vesicles drive specific forms of neurotransmission. Interspersed with these functional studies are analyses of the synaptic vesicle proteome which have consistently detected the presence of so-called “non-canonical” SNAREs that typically function in fusion and trafficking of other subcellular structures within the neuron. The recent identification of certain non-canonical vesicular SNAREs driving spontaneous (e.g., VAMP7 and vti1a) or evoked asynchronous (e.g., VAMP4) release integrates and corroborates existing data from functional and proteomic studies and implies that at least some complement of non-canonical SNAREs resident on synaptic vesicles function in neurotransmission. Here, we discuss the specific roles in neurotransmission of proteins homologous to each member of the classical neuronal SNARE complex consisting of synaptobrevin2, syntaxin-1 and SNAP-25.
Collapse
|
82
|
Santos MS, Foss SM, Park CK, Voglmaier SM. Protein interactions of the vesicular glutamate transporter VGLUT1. PLoS One 2014; 9:e109824. [PMID: 25334008 PMCID: PMC4198130 DOI: 10.1371/journal.pone.0109824] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 09/08/2014] [Indexed: 11/18/2022] Open
Abstract
Exocytotic release of glutamate depends upon loading of the neurotransmitter into synaptic vesicles by vesicular glutamate transporters, VGLUTs. The major isoforms, VGLUT1 and 2, exhibit a complementary pattern of expression in synapses of the adult rodent brain that correlates with the probability of release and potential for plasticity. Indeed, expression of different VGLUT protein isoforms confers different properties of release probability. Expression of VGLUT1 or 2 protein also determines the kinetics of synaptic vesicle recycling. To identify molecular determinants that may be related to reported differences in VGLUT trafficking and glutamate release properties, we investigated some of the intrinsic differences between the two isoforms. VGLUT1 and 2 exhibit a high degree of sequence homology, but differ in their N- and C-termini. While the C-termini of VGLUT1 and 2 share a dileucine-like trafficking motif and a proline-, glutamate-, serine-, and threonine-rich PEST domain, only VGLUT1 contains two polyproline domains and a phosphorylation consensus sequence in a region of acidic amino acids. The interaction of a VGLUT1 polyproline domain with the endocytic protein endophilin recruits VGLUT1 to a fast recycling pathway. To identify trans-acting cellular proteins that interact with the distinct motifs found in the C-terminus of VGLUT1, we performed a series of in vitro biochemical screening assays using the region encompassing the polyproline motifs, phosphorylation consensus sites, and PEST domain. We identify interactors that belong to several classes of proteins that modulate cellular function, including actin cytoskeletal adaptors, ubiquitin ligases, and tyrosine kinases. The nature of these interactions suggests novel avenues to investigate the modulation of synaptic vesicle protein recycling.
Collapse
Affiliation(s)
- Magda S. Santos
- Department of Psychiatry, University of California San Francisco, School of Medicine, San Francisco, California, United States of America
| | - Sarah M. Foss
- Department of Psychiatry, University of California San Francisco, School of Medicine, San Francisco, California, United States of America
- Graduate Program in Cell Biology, University of California San Francisco, School of Medicine, San Francisco, California, United States of America
| | - C. Kevin Park
- Department of Psychiatry, University of California San Francisco, School of Medicine, San Francisco, California, United States of America
| | - Susan M. Voglmaier
- Department of Psychiatry, University of California San Francisco, School of Medicine, San Francisco, California, United States of America
| |
Collapse
|
83
|
Saiepour MH, Chakravarthy S, Min R, Levelt CN. Competition and Homeostasis of Excitatory and Inhibitory Connectivity in the Adult Mouse Visual Cortex. Cereb Cortex 2014; 25:3713-22. [PMID: 25316336 PMCID: PMC4585512 DOI: 10.1093/cercor/bhu245] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
During cortical development, synaptic competition regulates the formation and adjustment of neuronal connectivity. It is unknown whether synaptic competition remains active in the adult brain and how inhibitory neurons participate in this process. Using morphological and electrophysiological measurements, we show that expressing a dominant-negative form of the TrkB receptor (TrkB.T1) in the majority of pyramidal neurons in the adult visual cortex does not affect excitatory synapse densities. This is in stark contrast to the previously reported loss of excitatory input which occurs if the exact same transgene is expressed in sparse neurons at the same age. This indicates that synaptic competition remains active in adulthood. Additionally, we show that interneurons not expressing the TrkB.T1 transgene may have a competitive advantage and obtain more excitatory synapses when most neighboring pyramidal neurons do express the transgene. Finally, we demonstrate that inhibitory synapses onto pyramidal neurons are reduced when TrkB signaling is interfered with in most pyramidal neurons but not when few pyramidal neurons have this deficit. This adjustment of inhibitory innervation is therefore not a cell-autonomous consequence of decreased TrkB signaling but more likely a homeostatic mechanism compensating for activity changes at the population level.
Collapse
Affiliation(s)
- M Hadi Saiepour
- Department of Molecular Visual Plasticity, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Amsterdam 1105, The Netherlands
| | - Sridhara Chakravarthy
- Department of Molecular Visual Plasticity, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Amsterdam 1105, The Netherlands
| | - Rogier Min
- Department of Molecular Visual Plasticity, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Amsterdam 1105, The Netherlands
| | - Christiaan N Levelt
- Department of Molecular Visual Plasticity, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Amsterdam 1105, The Netherlands
| |
Collapse
|
84
|
Revelo NH, Kamin D, Truckenbrodt S, Wong AB, Reuter-Jessen K, Reisinger E, Moser T, Rizzoli SO. A new probe for super-resolution imaging of membranes elucidates trafficking pathways. ACTA ACUST UNITED AC 2014; 205:591-606. [PMID: 24862576 PMCID: PMC4033769 DOI: 10.1083/jcb.201402066] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
mCLING is a novel membrane probe for the study of membrane trafficking with demonstrated value in both live and fixed cells across a wide range of biological systems. The molecular composition of the organelles involved in membrane recycling is difficult to establish as a result of the absence of suitable labeling tools. We introduce in this paper a novel probe, named membrane-binding fluorophore-cysteine-lysine-palmitoyl group (mCLING), which labels the plasma membrane and is taken up during endocytosis. It remains attached to membranes after fixation and permeabilization and can therefore be used in combination with immunostaining and super-resolution microscopy. We applied mCLING to mammalian-cultured cells, yeast, bacteria, primary cultured neurons, Drosophila melanogaster larval neuromuscular junctions, and mammalian tissue. mCLING enabled us to study the molecular composition of different trafficking organelles. We used it to address several questions related to synaptic vesicle recycling in the auditory inner hair cells from the organ of Corti and to investigate molecular differences between synaptic vesicles that recycle actively or spontaneously in cultured neurons. We conclude that mCLING enables the investigation of trafficking membranes in a broad range of preparations.
Collapse
Affiliation(s)
- Natalia H Revelo
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, GermanyDepartment of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany International Max Planck Research School for Neurosciences, 37077 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| | - Dirk Kamin
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, GermanyDepartment of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany
| | - Sven Truckenbrodt
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, GermanyDepartment of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany International Max Planck Research School for Molecular Biology, 37077 Göttingen, Germany
| | - Aaron B Wong
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany International Max Planck Research School for Neurosciences, 37077 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| | - Kirsten Reuter-Jessen
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| | - Ellen Reisinger
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| | - Tobias Moser
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| | - Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, GermanyDepartment of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| |
Collapse
|
85
|
Abstract
Secretory carrier membrane protein 5 (SCAMP5), a recently identified candidate gene for autism, is brain specific and highly abundant in synaptic vesicles (SVs), but its function is currently unknown. Here, we found that knockdown (KD) of endogenous SCAMP5 by SCAMP5-specific shRNAs in cultured rat hippocampal neurons resulted in a reduction in total vesicle pool size as well as in recycling pool size, but the recycling/resting pool ratio was significantly increased. SCAMP5 KD slowed endocytosis after stimulation, but impaired it severely during strong stimulation. We also found that KD dramatically lowered the threshold of activity at which SV endocytosis became unable to compensate for the ongoing exocytosis occurring during a stimulus. Reintroducing shRNA-resistant SCAMP5 reversed these endocytic defects. Therefore, our results suggest that SCAMP5 functions during high neuronal activity when a heavy load is imposed on endocytosis. Our data also raise the possibility that the reduction in expression of SCAMP5 in autistic patients may be related to the synaptic dysfunction observed in autism.
Collapse
|
86
|
Cheng X, Zhang X, Gao Q, Ali Samie M, Azar M, Tsang WL, Dong L, Sahoo N, Li X, Zhuo Y, Garrity AG, Wang X, Ferrer M, Dowling J, Xu L, Han R, Xu H. The intracellular Ca²⁺ channel MCOLN1 is required for sarcolemma repair to prevent muscular dystrophy. Nat Med 2014; 20:1187-92. [PMID: 25216637 PMCID: PMC4192061 DOI: 10.1038/nm.3611] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 05/19/2014] [Indexed: 12/15/2022]
Abstract
The integrity of the plasma membrane is maintained through an active repair process, especially for skeletal and cardiac muscle cells, in which contraction-induced mechanical damage frequently occurs in vivo1,2. Muscular dystrophies (MDs) are a group of muscle diseases characterized by skeletal muscle wasting and weakness3,4. An important cause of MD is defective repair of sarcolemmal injuries, and sarcolemma repair requires Ca2+ sensor proteins5–8 and Ca2+-dependent delivery of intracellular vesicles to injury sites5,8,9. TRPML1 (ML1) is an endosomal and lysosomal Ca2+ channel and its human mutations cause Mucolipidosis IV, a neurodegenerative disease with motor disabilities10,11. Here, we report that ML1-null mice develop a primary, early-onset muscular dystrophy independent of neural degeneration. Although the dystrophin-glycoprotein complex and the known membrane repair proteins are normally expressed, membrane resealing was defective in ML1-null muscle fibers or upon acute and pharmacological inhibition of ML1 channel activity or vesicular Ca2+ release. Injury facilitated the trafficking and exocytosis of vesicles by upmodulating ML1 channel activity. In the dystrophic mdx mouse model, overexpression of ML1 decreased muscle pathology. Collectively, we have identified an intracellular Ca2+ channel that regulates membrane repair in skeletal muscle via Ca2+-dependent vesicle exocytosis.
Collapse
Affiliation(s)
- Xiping Cheng
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Xiaoli Zhang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Qiong Gao
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Mohammad Ali Samie
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Marlene Azar
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Wai Lok Tsang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Libing Dong
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Nirakar Sahoo
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Xinran Li
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Yue Zhuo
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Abigail G Garrity
- 1] Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA. [2] Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA
| | - Xiang Wang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Marc Ferrer
- National Center for Advancing Translational Science, National Institutes of Health, Maryland, USA
| | - James Dowling
- 1] Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, Michigan, USA. [2] Division of Neurology, Hospital for Sick Children, Toronto, Ontario, Canada [3] Program of Genetic and Genome Biology, Hospital for Sick Children, Toronto, Ontario, Canada [4] Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada [5] Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Li Xu
- Department of Cell and Molecular Physiology, Loyola University Chicago Health Sciences Division, Chicago, Illinois, USA
| | - Renzhi Han
- Department of Cell and Molecular Physiology, Loyola University Chicago Health Sciences Division, Chicago, Illinois, USA
| | - Haoxing Xu
- 1] Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA. [2] Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA
| |
Collapse
|
87
|
Drosophila melanogaster as a genetic model system to study neurotransmitter transporters. Neurochem Int 2014; 73:71-88. [PMID: 24704795 DOI: 10.1016/j.neuint.2014.03.015] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 03/20/2014] [Accepted: 03/24/2014] [Indexed: 12/30/2022]
Abstract
The model genetic organism Drosophila melanogaster, commonly known as the fruit fly, uses many of the same neurotransmitters as mammals and very similar mechanisms of neurotransmitter storage, release and recycling. This system offers a variety of powerful molecular-genetic methods for the study of transporters, many of which would be difficult in mammalian models. We review here progress made using Drosophila to understand the function and regulation of neurotransmitter transporters and discuss future directions for its use.
Collapse
|
88
|
Abstract
Synaptic vesicle recycling is one of the best-studied cellular pathways. Many of the proteins involved are known, and their interactions are becoming increasingly clear. However, as for many other pathways, it is still difficult to understand synaptic vesicle recycling as a whole. While it is generally possible to point out how synaptic reactions take place, it is not always easy to understand what triggers or controls them. Also, it is often difficult to understand how the availability of the reaction partners is controlled: how the reaction partners manage to find each other in the right place, at the right time. I present here an overview of synaptic vesicle recycling, discussing the mechanisms that trigger different reactions, and those that ensure the availability of reaction partners. A central argument is that synaptic vesicles bind soluble cofactor proteins, with low affinity, and thus control their availability in the synapse, forming a buffer for cofactor proteins. The availability of cofactor proteins, in turn, regulates the different synaptic reactions. Similar mechanisms, in which one of the reaction partners buffers another, may apply to many other processes, from the biogenesis to the degradation of the synaptic vesicle.
Collapse
Affiliation(s)
- Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen European Neuroscience Institute, Göttingen, Germany
| |
Collapse
|
89
|
Pantano S, Montecucco C. The blockade of the neurotransmitter release apparatus by botulinum neurotoxins. Cell Mol Life Sci 2014; 71:793-811. [PMID: 23749048 PMCID: PMC11113401 DOI: 10.1007/s00018-013-1380-7] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 05/15/2013] [Accepted: 05/16/2013] [Indexed: 12/22/2022]
Abstract
The high toxicity of the seven serotypes of botulinum neurotoxins (BoNT/A to G), together with their specificity and reversibility, includes them in the list A of potential bioterrorism weapons and, at the same time, among the therapeutics of choice for a variety of human syndromes. They invade nerve terminals and cleave specifically the three proteins which form the heterotrimeric SNAP REceptors (SNARE) complex that mediates neurotransmitter release. The BoNT-induced cleavage of the SNARE proteins explains by itself the paralysing activity of the BoNTs because the truncated proteins cannot form the SNARE complex. However, in the case of BoNT/A, the most widely used toxin in therapy, additional factors come into play as it only removes a few residues from the synaptosomal associate protein of 25 kDa C-terminus and this results in a long duration of action. To explain these facts and other experimental data, we present here a model for the assembly of the neuroexocytosis apparatus in which Synaptotagmin and Complexin first assist the zippering of the SNARE complex, and then stabilize and clamp an octameric radial assembly of the SNARE complexes.
Collapse
Affiliation(s)
- Sergio Pantano
- Institut Pasteur de Montevideo, Calle Mataojo 2020, CP 11400 Montevideo, Uruguay
| | - Cesare Montecucco
- Department of Biomedical Sciences, University of Padova, Padua, Italy
- Institute of Neuroscience, National Research Council, Viale G. Colombo 3, 35121 Padua, Italy
| |
Collapse
|
90
|
Mishima T, Fujiwara T, Sanada M, Kofuji T, Kanai-Azuma M, Akagawa K. Syntaxin 1B, but not syntaxin 1A, is necessary for the regulation of synaptic vesicle exocytosis and of the readily releasable pool at central synapses. PLoS One 2014; 9:e90004. [PMID: 24587181 PMCID: PMC3938564 DOI: 10.1371/journal.pone.0090004] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 01/24/2014] [Indexed: 11/24/2022] Open
Abstract
Two syntaxin 1 (STX1) isoforms, HPC-1/STX1A and STX1B, are coexpressed in neurons and function as neuronal target membrane (t)-SNAREs. However, little is known about their functional differences in synaptic transmission. STX1A null mutant mice develop normally and do not show abnormalities in fast synaptic transmission, but monoaminergic transmissions are impaired. In the present study, we found that STX1B null mutant mice died within 2 weeks of birth. To examine functional differences between STX1A and 1B, we analyzed the presynaptic properties of glutamatergic and GABAergic synapses in STX1B null mutant and STX1A/1B double null mutant mice. We found that the frequency of spontaneous quantal release was lower and the paired-pulse ratio of evoked postsynaptic currents was significantly greater in glutamatergic and GABAergic synapses of STX1B null neurons. Deletion of STX1B also accelerated synaptic vesicle turnover in glutamatergic synapses and decreased the size of the readily releasable pool in glutamatergic and GABAergic synapses. Moreover, STX1A/1B double null neurons showed reduced and asynchronous evoked synaptic vesicle release in glutamatergic and GABAergic synapses. Our results suggest that although STX1A and 1B share a basic function as neuronal t-SNAREs, STX1B but not STX1A is necessary for the regulation of spontaneous and evoked synaptic vesicle exocytosis in fast transmission.
Collapse
Affiliation(s)
- Tatsuya Mishima
- Department of Cell Physiology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
- * E-mail:
| | - Tomonori Fujiwara
- Department of Cell Physiology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Masumi Sanada
- Department of Cell Physiology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Takefumi Kofuji
- Radio Isotope Laboratory, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Masami Kanai-Azuma
- Department of Anatomy, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Kimio Akagawa
- Department of Cell Physiology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| |
Collapse
|
91
|
Kavalali ET, Jorgensen EM. Visualizing presynaptic function. Nat Neurosci 2013; 17:10-6. [PMID: 24369372 DOI: 10.1038/nn.3578] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 10/14/2013] [Indexed: 12/15/2022]
Abstract
Synaptic communication in the nervous system is initiated by the fusion of synaptic vesicles with the presynaptic plasma membrane and subsequent neurotransmitter release. In the 1980s, this process was characterized by electron microscopy, albeit without the ability to follow processes in living cells. In the last two decades, fluorescence imaging methods have been developed that report synaptic vesicle fusion, endocytosis and recycling. These probes have provided unprecedented insight into synaptic vesicle trafficking in individual synaptic terminals and revealed heterogeneity in recycling pathways as well as synaptic vesicle populations. These methods either take advantage of uptake of fluorescent probes into recycling vesicles or exogenous expression of synaptic vesicle proteins tagged with a pH-sensitive fluorescent marker at regions facing the vesicle lumen. We provide an overview of these methods, with particular emphasis on the challenges associated with their use and the opportunities for future investigations.
Collapse
Affiliation(s)
- Ege T Kavalali
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Erik M Jorgensen
- 1] Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, USA. [2] Department of Biology, University of Utah, Salt Lake City, Utah, USA
| |
Collapse
|
92
|
Abstract
Neurotransmitter release from synaptic vesicle fusion is the fundamental mechanism for neuronal communication at synapses. Evoked release following an action potential has been well characterized for its function in activating the postsynaptic cell, but the significance of spontaneous release is less clear. Using transgenic tools to image single synaptic vesicle fusion events at individual release sites (active zones) in Drosophila, we characterized the spatial and temporal dynamics of exocytotic events that occur spontaneously or in response to an action potential. We also analyzed the relationship between these two modes of fusion at single release sites. A majority of active zones participate in both modes of fusion, although release probability is not correlated between the two modes of release and is highly variable across the population. A subset of active zones is specifically dedicated to spontaneous release, indicating a population of postsynaptic receptors is uniquely activated by this mode of vesicle fusion. Imaging synaptic transmission at individual release sites also revealed general rules for spontaneous and evoked release, and indicate that active zones with similar release probability can cluster spatially within individual synaptic boutons. These findings suggest neuronal connections contain two information channels that can be spatially segregated and independently regulated to transmit evoked or spontaneous fusion signals.
Collapse
|
93
|
Gordon SL, Cousin MA. The Sybtraps: control of synaptobrevin traffic by synaptophysin, α-synuclein and AP-180. Traffic 2013; 15:245-54. [PMID: 24279465 PMCID: PMC3992847 DOI: 10.1111/tra.12140] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Revised: 11/22/2013] [Accepted: 11/26/2013] [Indexed: 01/18/2023]
Abstract
Synaptobrevin II (sybII) is a key fusogenic molecule on synaptic vesicles (SVs) therefore the active maintenance of both its conformation and location in sufficient numbers on this organelle is critical in both mediating and sustaining neurotransmitter release. Recently three proteins have been identified having key roles in the presentation, trafficking and retrieval of sybII during the fusion and endocytosis of SVs. The nerve terminal protein α-synuclein catalyses sybII entry into SNARE complexes, whereas the monomeric adaptor protein AP-180 is required for sybII retrieval during SV endocytosis. Overarching these events is the tetraspan SV protein synaptophysin, which is a major sybII interaction partner on the SV. This review will evaluate recent studies to propose working models for the control of sybII traffic by synaptophysin and other Sybtraps (sybII trafficking partners) and suggest how dysfunction in sybII traffic may contribute to human disease.
Collapse
Affiliation(s)
- Sarah L Gordon
- Membrane Biology Group, Centre for Integrative Physiology, George Square, University of Edinburgh, Scotland, EH8 9XD, UK
| | | |
Collapse
|
94
|
Mullin AP, Gokhale A, Moreno-De-Luca A, Sanyal S, Waddington JL, Faundez V. Neurodevelopmental disorders: mechanisms and boundary definitions from genomes, interactomes and proteomes. Transl Psychiatry 2013; 3:e329. [PMID: 24301647 PMCID: PMC4030327 DOI: 10.1038/tp.2013.108] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 10/22/2013] [Indexed: 02/08/2023] Open
Abstract
Neurodevelopmental disorders such as intellectual disability, autism spectrum disorder and schizophrenia lack precise boundaries in their clinical definitions, epidemiology, genetics and protein-protein interactomes. This calls into question the appropriateness of current categorical disease concepts. Recently, there has been a rising tide to reformulate neurodevelopmental nosological entities from biology upward. To facilitate this developing trend, we propose that identification of unique proteomic signatures that can be strongly associated with patient's risk alleles and proteome-interactome-guided exploration of patient genomes could define biological mechanisms necessary to reformulate disorder definitions.
Collapse
Affiliation(s)
- A P Mullin
- Department of Cell Biology, Emory University School of Medicine, Center for Social Translational Neuroscience, Emory University, Atlanta, GA, USA
| | - A Gokhale
- Department of Cell Biology, Emory University School of Medicine, Center for Social Translational Neuroscience, Emory University, Atlanta, GA, USA
| | - A Moreno-De-Luca
- Autism and Developmental Medicine Institute, Genomic Medicine Institute, Geisinger Health System, Danville, PA, USA
| | - S Sanyal
- Department of Cell Biology, Emory University School of Medicine, Center for Social Translational Neuroscience, Emory University, Atlanta, GA, USA,Biogen-Idec, 14 Cambridge Center, Cambridge, MA, USA
| | - J L Waddington
- Molecular & Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - V Faundez
- Department of Cell Biology, Emory University School of Medicine, Center for Social Translational Neuroscience, Emory University, Atlanta, GA, USA,Center for Social Translational Neuroscience, Emory University, Atlanta, GA, USA,Department of Cell Biology, Emory University School of Medicine, Center for Social Translational Neuroscience, Emory University, Atlanta, GA 30322, USA. E-mail:
| |
Collapse
|
95
|
Bourne JN, Chirillo MA, Harris KM. Presynaptic ultrastructural plasticity along CA3→CA1 axons during long-term potentiation in mature hippocampus. J Comp Neurol 2013; 521:3898-912. [PMID: 23784793 PMCID: PMC3838200 DOI: 10.1002/cne.23384] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 04/30/2013] [Accepted: 06/07/2013] [Indexed: 11/12/2022]
Abstract
In area CA1 of the mature hippocampus, synaptogenesis occurs within 30 minutes after the induction of long-term potentiation (LTP); however, by 2 hours many small dendritic spines are lost, and those remaining have larger synapses. Little is known, however, about associated changes in presynaptic vesicles and axonal boutons. Axons in CA1 stratum radiatum were evaluated with 3D reconstructions from serial section electron microscopy at 30 minutes and 2 hours after induction of LTP by theta-burst stimulation (TBS). The frequency of axonal boutons with a single postsynaptic partner was decreased by 33% at 2 hours, corresponding perfectly to the 33% loss specifically of small dendritic spines (head diameters <0.45 μm). Docked vesicles were reduced at 30 minutes and then returned to control levels by 2 hours following induction of LTP. By 2 hours there were fewer small synaptic vesicles overall in the presynaptic vesicle pool. Clathrin-mediated endocytosis was used as a marker of local activity, and axonal boutons containing clathrin-coated pits showed a more pronounced decrease in presynaptic vesicles at both 30 minutes and 2 hours after induction of LTP relative to control values. Putative transport packets, identified as a cluster of less than 10 axonal vesicles occurring between synaptic boutons, were stable at 30 minutes but markedly reduced by 2 hours after the induction of LTP. APV blocked these effects, suggesting that the loss of axonal boutons and presynaptic vesicles was dependent on N-methyl-D-aspartic acid (NMDA) receptor activation during LTP. These findings show that specific presynaptic ultrastructural changes complement postsynaptic ultrastructural plasticity during LTP.
Collapse
Affiliation(s)
- Jennifer N Bourne
- Center for Learning and Memory, Section of Neurobiology, Institute for Neuroscience, University of Texas, Austin, Texas, 78712; Department of Physiology and Biophysics, University of Colorado, Anschutz Medical Campus, Aurora, CO, 80045
| | | | | |
Collapse
|
96
|
Kaeser PS, Regehr WG. Molecular mechanisms for synchronous, asynchronous, and spontaneous neurotransmitter release. Annu Rev Physiol 2013; 76:333-63. [PMID: 24274737 DOI: 10.1146/annurev-physiol-021113-170338] [Citation(s) in RCA: 286] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Most neuronal communication relies upon the synchronous release of neurotransmitters, which occurs through synaptic vesicle exocytosis triggered by action potential invasion of a presynaptic bouton. However, neurotransmitters are also released asynchronously with a longer, variable delay following an action potential or spontaneously in the absence of action potentials. A compelling body of research has identified roles and mechanisms for synchronous release, but asynchronous release and spontaneous release are less well understood. In this review, we analyze how the mechanisms of the three release modes overlap and what molecular pathways underlie asynchronous and spontaneous release. We conclude that the modes of release have key fusion processes in common but may differ in the source of and necessity for Ca(2+) to trigger release and in the identity of the Ca(2+) sensor for release.
Collapse
Affiliation(s)
- Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115; ,
| | | |
Collapse
|
97
|
Bal M, Leitz J, Reese AL, Ramirez DMO, Durakoglugil M, Herz J, Monteggia LM, Kavalali ET. Reelin mobilizes a VAMP7-dependent synaptic vesicle pool and selectively augments spontaneous neurotransmission. Neuron 2013; 80:934-46. [PMID: 24210904 DOI: 10.1016/j.neuron.2013.08.024] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2013] [Indexed: 02/07/2023]
Abstract
Reelin is a glycoprotein that is critical for proper layering of neocortex during development as well as dynamic regulation of glutamatergic postsynaptic signaling in mature synapses. Here, we show that Reelin also acts presynaptically, resulting in robust rapid enhancement of spontaneous neurotransmitter release without affecting properties of evoked neurotransmission. This effect of Reelin requires a modest but significant increase in presynaptic Ca(2+) initiated via ApoER2 signaling. The specificity of Reelin action on spontaneous neurotransmitter release is encoded at the level of vesicular SNARE machinery as it requires VAMP7 and SNAP-25 but not synaptobrevin2, VAMP4, or vti1a. These results uncover a presynaptic regulatory pathway that utilizes the heterogeneity of synaptic vesicle-associated SNAREs and selectively augments action potential-independent neurotransmission.
Collapse
Affiliation(s)
- Manjot Bal
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | | | | | | | | | | | | | | |
Collapse
|
98
|
Molino D, Galli T. Biogenesis and transport of membrane domains-potential implications in brain pathologies. Biochimie 2013; 96:75-84. [PMID: 24075975 DOI: 10.1016/j.biochi.2013.09.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 09/12/2013] [Indexed: 11/28/2022]
Abstract
Lipids in biological membranes show astonishing chemical diversity, but they also show some key conserved structures in different organisms. In addition, some of their biophysical properties have been related to specific functions. In this review, we aim to discuss the role of sphingolipids- and cholesterol-rich micro- and nano-membrane domains (MD) and highlight their pivotal role in lipid-protein clustering processes, vesicle biogenesis and membrane fusion. We further review potential connections between human pathologies and defects in MD biosynthesis, recycling and homeostasis. Brain, which is second only to the adipose tissues in term of lipid abundance, is particularly affected by MD defects which are linked to neurodegenerative disorders. Finally we propose a potential connection between MD and several nutrient-related processes and envision how diet and autophagy could bring insights towards understanding the impact of global lipid homeostasis on human health and disease.
Collapse
Affiliation(s)
- Diana Molino
- Institut Jacques Monod, UMR 7592, CNRS, Université Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France; INSERM ERL U950, Membrane Traffic in Neuronal and Epithelial Morphogenesis, F-75013 Paris, France.
| | | |
Collapse
|
99
|
Morgan JR, Comstra HS, Cohen M, Faundez V. Presynaptic membrane retrieval and endosome biology: defining molecularly heterogeneous synaptic vesicles. Cold Spring Harb Perspect Biol 2013; 5:a016915. [PMID: 24086045 DOI: 10.1101/cshperspect.a016915] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The release and uptake of neurotransmitters by synaptic vesicles is a tightly controlled process that occurs in response to diverse stimuli at morphologically disparate synapses. To meet these architectural and functional synaptic demands, it follows that there should be diversity in the mechanisms that control their secretion and retrieval and possibly in the composition of synaptic vesicles within the same terminal. Here we pay particular attention to areas where such diversity is generated, such as the variance in exocytosis/endocytosis coupling, SNAREs defining functionally diverse synaptic vesicle populations and the adaptor-dependent sorting machineries capable of generating vesicle diversity. We argue that there are various synaptic vesicle recycling pathways at any given synapse and discuss several lines of evidence that support the role of the endosome in synaptic vesicle recycling.
Collapse
Affiliation(s)
- Jennifer R Morgan
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts 02543
| | | | | | | |
Collapse
|
100
|
Abstract
The vesicular glutamate transporters (VGLUTs) package glutamate into synaptic vesicles, and the two principal isoforms VGLUT1 and VGLUT2 have been suggested to influence the properties of release. To understand how a VGLUT isoform might influence transmitter release, we have studied their trafficking and previously identified a dileucine-like endocytic motif in the C terminus of VGLUT1. Disruption of this motif impairs the activity-dependent recycling of VGLUT1, but does not eliminate its endocytosis. We now report the identification of two additional dileucine-like motifs in the N terminus of VGLUT1 that are not well conserved in the other isoforms. In the absence of all three motifs, rat VGLUT1 shows limited accumulation at synaptic sites and no longer responds to stimulation. In addition, shRNA-mediated knockdown of clathrin adaptor proteins AP-1 and AP-2 shows that the C-terminal motif acts largely via AP-2, whereas the N-terminal motifs use AP-1. Without the C-terminal motif, knockdown of AP-1 reduces the proportion of VGLUT1 that responds to stimulation. VGLUT1 thus contains multiple sorting signals that engage distinct trafficking mechanisms. In contrast to VGLUT1, the trafficking of VGLUT2 depends almost entirely on the conserved C-terminal dileucine-like motif: without this motif, a substantial fraction of VGLUT2 redistributes to the plasma membrane and the transporter's synaptic localization is disrupted. Consistent with these differences in trafficking signals, wild-type VGLUT1 and VGLUT2 differ in their response to stimulation.
Collapse
|