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Kuznetsov IA, Kuznetsov AV. How old are dense-core vesicles residing in en passant boutons: simulation of the mean age of dense-core vesicles in axonal arbours accounting for resident and transiting vesicle populations. Proc Math Phys Eng Sci 2020; 476:20200454. [PMID: 33071588 PMCID: PMC7544361 DOI: 10.1098/rspa.2020.0454] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 09/02/2020] [Indexed: 12/21/2023] Open
Abstract
In neurons, neuropeptides are synthesized in the soma and are then transported along the axon in dense-core vesicles (DCVs). DCVs are captured in varicosities located along the axon terminal called en passant boutons, which are active terminal sites that accumulate and release neurotransmitters. Recently developed experimental techniques allow for the estimation of the age of DCVs in various locations in the axon terminal. Accurate simulation of the mean age of DCVs in boutons requires the development of a model that would account for resident, transiting-anterograde and transiting-retrograde DCV populations. In this paper, such a model is developed. The model is applied to simulating DCV transport in Drosophila type II motoneurons. The model simulates DCV transport and capture in the axon terminals and makes it possible to predict the age density distribution of DCVs in en passant boutons as well as DCV mean age in boutons. The predicted prevalence of older organelles in distal boutons may explain the 'dying back' pattern of axonal degeneration observed in dopaminergic neurons in Parkinson's disease. The predicted difference of two hours between the age of older DCVs residing in distal boutons and the age of younger DCVs residing in proximal boutons is consistent with an approximate estimate of age difference deduced from experimental observations. The age density of resident DCVs is found to be bimodal, which is because DCVs are captured from two transiting states: the anterograde transiting state that contains younger DCVs and the retrograde transiting state that contains older DCVs.
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Affiliation(s)
- Ivan A. Kuznetsov
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Andrey V. Kuznetsov
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695-7910, USA
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Chondroitin sulfate proteoglycan-5 forms perisynaptic matrix assemblies in the adult rat cortex. Cell Signal 2020; 74:109710. [PMID: 32653642 DOI: 10.1016/j.cellsig.2020.109710] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 07/07/2020] [Indexed: 12/30/2022]
Abstract
Composition of the brain extracellular matrix changes in time as maturation proceeds. Chondroitin sulfate proteoglycan 5 (CSPG-5), also known as neuroglycan C, has been previously associated to differentiation since it shapes neurite growth and synapse forming. Here, we show that this proteoglycan persists in the postnatal rat brain, and its expression is higher in cortical regions with plastic properties, including hippocampus and the medial prefrontal cortex at the end of the second postnatal week. Progressively accumulating after birth, CSPG-5 typically concentrates around glutamatergic and GABAergic terminals in twelve-week old rat hippocampus. CSPG-5-containing perisynaptic matrix rings often appear at the peripheral margin of perineuronal nets. Electron microscopy and analysis of synaptosomal fraction showed that CSPG-5 accumulates around, and is associated to synapses, respectively. In vitro analyses suggest that neurons, but less so astrocytes, express CSPG-5 in rat primary neocortical cultures, and CSPG-5 produced by transfected neuroblastoma cells appear at endings and contact points of neurites. In human subjects, CSPG-5 expression shifts in brain areas of the default mode network of suicide victims, which may reflect an impact in the pathogenesis of psychiatric diseases or support diagnostic power.
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Wong Y, Luk K, Purtell K, Nanni SB, Stoessl AJ, Trudeau LE, Yue Z, Krainc D, Oertel W, Obeso JA, Volpicelli-Daley L. Neuronal vulnerability in Parkinson disease: Should the focus be on axons and synaptic terminals? Mov Disord 2019; 34:1406-1422. [PMID: 31483900 PMCID: PMC6879792 DOI: 10.1002/mds.27823] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 07/03/2019] [Accepted: 07/12/2019] [Indexed: 12/11/2022] Open
Abstract
While current effective therapies are available for the symptomatic control of PD, treatments to halt the progressive neurodegeneration still do not exist. Loss of dopamine neurons in the SNc and dopamine terminals in the striatum drive the motor features of PD. Multiple lines of research point to several pathways which may contribute to dopaminergic neurodegeneration. These pathways include extensive axonal arborization, mitochondrial dysfunction, dopamine's biochemical properties, abnormal protein accumulation of α-synuclein, defective autophagy and lysosomal degradation, and synaptic impairment. Thus, understanding the essential features and mechanisms of dopaminergic neuronal vulnerability is a major scientific challenge and highlights an outstanding need for fostering effective therapies against neurodegeneration in PD. This article, which arose from the Movement Disorders 2018 Conference, discusses and reviews the possible mechanisms underlying neuronal vulnerability and potential therapeutic approaches in PD. © 2019 International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Yvette Wong
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
| | - Kelvin Luk
- Department of Pathology and Laboratory Medicine, Center for Neurodegenerative Disease Research, Philadelphia, PA, 19104-4283, USA
| | - Kerry Purtell
- Department of Neurology, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, Hess Research Center 9th Floor, New York, NY 10029, USA
| | - Samuel Burke Nanni
- CNS Research Group, Department of Pharmacology and Physiology, Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
| | - A. Jon Stoessl
- University of British Columbia and Vancouver Coastal Health, Pacific Parkinson’s Research Centre & National Parkinson Foundation Centre of Excellence, 2221 Wesbrook Mall, Vancouver, BC, V6T 2B5, Canada
| | - Louis-Eric Trudeau
- CNS Research Group, Department of Pharmacology and Physiology, Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
| | - Zhenyu Yue
- Department of Neurology, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, 1470 Madison Avenue, Hess Research Center 9th Floor, New York, NY 10029, USA
| | - Dimitri Krainc
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
| | - Wolfgang Oertel
- Department of Neurology, Philipps University Marburg, Baldingerstraße 1, 35043, Marburg, Germany
| | - Jose A. Obeso
- HM CINAC, HM Puerta del Sur, Hospitales de Madrid, Mostoles Medical School, CEU-San Pablo University, and CIBERNED, Instituto Carlos III, Madrid, Spain
| | - Laura Volpicelli-Daley
- Department of Neurology, Center for Neurodegeneration and Experimental Therapeutics, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
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Kuznetsov IA, Kuznetsov AV. Modelling transport and mean age of dense core vesicles in large axonal arbours. Proc Math Phys Eng Sci 2019; 475:20190284. [PMID: 31534430 PMCID: PMC6735487 DOI: 10.1098/rspa.2019.0284] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 07/19/2019] [Indexed: 10/14/2023] Open
Abstract
A model simulating the transport of dense core vesicles (DCVs) in type II axonal terminals of Drosophila motoneurons has been developed. The morphology of type II terminals is characterized by the large number of en passant boutons. The lack of both scaled-up DCV transport and scaled-down DCV capture in boutons results in a less efficient supply of DCVs to distal boutons. Furthermore, the large number of boutons that DCVs pass as they move anterogradely until they reach the most distal bouton may lead to the capture of a majority of DCVs before they turn around in the most distal bouton to move in the retrograde direction. This may lead to a reduced retrograde flux of DCVs and a lack of DCV circulation in type II terminals. The developed model simulates DCV concentrations in boutons, DCV fluxes between the boutons, age density distributions of DCVs and the mean age of DCVs in various boutons. Unlike published experimental observations, our model predicts DCV circulation in type II terminals after these terminals are filled to saturation. This disagreement is likely because experimentally observed terminals were not at steady state, but rather were accumulating DCVs for later release. Our estimates show that the number of DCVs in the transiting state is much smaller than that in the resident state. DCVs travelling in the axon, rather than DCVs transiting in the terminal, may provide a reserve of DCVs for replenishing boutons after a release. The techniques for modelling transport of DCVs developed in our paper can be used to model the transport of other organelles in axons.
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Affiliation(s)
- I. A. Kuznetsov
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - A. V. Kuznetsov
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695-7910, USA
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Tao J, Bulgari D, Berkhoudt DA, Calderon MJ, Watkins SC, Fonseca Velez HJ, Sabeva N, Deitcher DL, Levitan ES. Drosophila Ptp4E regulates vesicular packaging for monoamine-neuropeptide co-transmission. J Cell Sci 2019; 132:jcs.224568. [PMID: 30837287 DOI: 10.1242/jcs.224568] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 02/25/2019] [Indexed: 12/12/2022] Open
Abstract
Many neurons influence their targets through co-release of neuropeptides and small-molecule transmitters. Neuropeptides are packaged into dense-core vesicles (DCVs) in the soma and then transported to synapses, while small-molecule transmitters such as monoamines are packaged by vesicular transporters that function at synapses. These separate packaging mechanisms point to activity, by inducing co-release as the sole scaler of co-transmission. Based on screening in Drosophila for increased presynaptic neuropeptides, the receptor protein tyrosine phosphatase (Rptp) Ptp4E was found to post-transcriptionally regulate neuropeptide content in single DCVs at octopamine synapses. This occurs without changing neuropeptide release efficiency, transport and DCV size measured by both stimulated emission depletion super-resolution and transmission electron microscopy. Ptp4E also controls the presynaptic abundance and activity of the vesicular monoamine transporter (VMAT), which packages monoamine transmitters for synaptic release. Thus, rather than rely on altering electrical activity, the Rptp regulates packaging underlying monoamine-neuropeptide co-transmission by controlling vesicular membrane transporter and luminal neuropeptide content.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Juan Tao
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Dinara Bulgari
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Drew A Berkhoudt
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Michael J Calderon
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Hector J Fonseca Velez
- Department of Neuroscience, Universidad Central del Caribe, Bayamón, Puerto Rico 00960, USA
| | - Nadezhda Sabeva
- Department of Neuroscience, Universidad Central del Caribe, Bayamón, Puerto Rico 00960, USA
| | - David L Deitcher
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - Edwin S Levitan
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
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Myopic (HD-PTP, PTPN23) selectively regulates synaptic neuropeptide release. Proc Natl Acad Sci U S A 2018; 115:1617-1622. [PMID: 29378961 DOI: 10.1073/pnas.1716801115] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Neurotransmission is mediated by synaptic exocytosis of neuropeptide-containing dense-core vesicles (DCVs) and small-molecule transmitter-containing small synaptic vesicles (SSVs). Exocytosis of both vesicle types depends on Ca2+ and shared secretory proteins. Here, we show that increasing or decreasing expression of Myopic (mop, HD-PTP, PTPN23), a Bro1 domain-containing pseudophosphatase implicated in neuronal development and neuropeptide gene expression, increases synaptic neuropeptide stores at the Drosophila neuromuscular junction (NMJ). This occurs without altering DCV content or transport, but synaptic DCV number and age are increased. The effect on synaptic neuropeptide stores is accounted for by inhibition of activity-induced Ca2+-dependent neuropeptide release. cAMP-evoked Ca2+-independent synaptic neuropeptide release also requires optimal Myopic expression, showing that Myopic affects the DCV secretory machinery shared by cAMP and Ca2+ pathways. Presynaptic Myopic is abundant at early endosomes, but interaction with the endosomal sorting complex required for transport III (ESCRT III) protein (CHMP4/Shrub) that mediates Myopic's effect on neuron pruning is not required for control of neuropeptide release. Remarkably, in contrast to the effect on DCVs, Myopic does not affect release from SSVs. Therefore, Myopic selectively regulates synaptic DCV exocytosis that mediates peptidergic transmission at the NMJ.
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