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Feghhi T, Hernandez RX, Stawarski M, Thomas CI, Kamasawa N, Lau AWC, Macleod GT. Computational modeling predicts ephemeral acidic microdomains in the glutamatergic synaptic cleft. Biophys J 2021; 120:5575-5591. [PMID: 34774503 DOI: 10.1016/j.bpj.2021.11.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 10/21/2021] [Accepted: 11/05/2021] [Indexed: 10/19/2022] Open
Abstract
At chemical synapses, synaptic vesicles release their acidic contents into the cleft, leading to the expectation that the cleft should acidify. However, fluorescent pH probes targeted to the cleft of conventional glutamatergic synapses in both fruit flies and mice reveal cleft alkalinization rather than acidification. Here, using a reaction-diffusion scheme, we modeled pH dynamics at the Drosophila neuromuscular junction as glutamate, ATP, and protons (H+) were released into the cleft. The model incorporates bicarbonate and phosphate buffering systems as well as plasma membrane calcium-ATPase activity and predicts substantial cleft acidification but only for fractions of a millisecond after neurotransmitter release. Thereafter, the cleft rapidly alkalinizes and remains alkaline for over 100 ms because the plasma membrane calcium-ATPase removes H+ from the cleft in exchange for calcium ions from adjacent pre- and postsynaptic compartments, thus recapitulating the empirical data. The extent of synaptic vesicle loading and time course of exocytosis have little influence on the magnitude of acidification. Phosphate but not bicarbonate buffering is effective at suppressing the magnitude and time course of the acid spike, whereas both buffering systems are effective at suppressing cleft alkalinization. The small volume of the cleft levies a powerful influence on the magnitude of alkalinization and its time course. Structural features that open the cleft to adjacent spaces appear to be essential for alleviating the extent of pH transients accompanying neurotransmission.
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Affiliation(s)
- Touhid Feghhi
- Department of Physics, College of Science, Florida Atlantic University, Boca Raton, Florida
| | - Roberto X Hernandez
- Integrative Biology & Neuroscience Graduate Program, Florida Atlantic University, Boca Raton, Florida; International Max Planck Research School for Brain and Behavior, Jupiter, Florida; Jupiter Life Sciences Initiative, Florida Atlantic University, Jupiter, Florida
| | - Michal Stawarski
- Wilkes Honors College, Florida Atlantic University, Jupiter, Florida
| | - Connon I Thomas
- Electron Microscopy Core Facility, Max Planck Florida Institute, Jupiter, Florida
| | - Naomi Kamasawa
- Electron Microscopy Core Facility, Max Planck Florida Institute, Jupiter, Florida
| | - A W C Lau
- Department of Physics, College of Science, Florida Atlantic University, Boca Raton, Florida
| | - Gregory T Macleod
- Jupiter Life Sciences Initiative, Florida Atlantic University, Jupiter, Florida; Wilkes Honors College, Florida Atlantic University, Jupiter, Florida; Brain Institute, Florida Atlantic University, Jupiter, Florida; Institute for Human Health & Disease Intervention, Florida Atlantic University, Jupiter, Florida.
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5
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Freyberg Z, Sonders MS, Aguilar JI, Hiranita T, Karam CS, Flores J, Pizzo AB, Zhang Y, Farino ZJ, Chen A, Martin CA, Kopajtic TA, Fei H, Hu G, Lin YY, Mosharov EV, McCabe BD, Freyberg R, Wimalasena K, Hsin LW, Sames D, Krantz DE, Katz JL, Sulzer D, Javitch JA. Mechanisms of amphetamine action illuminated through optical monitoring of dopamine synaptic vesicles in Drosophila brain. Nat Commun 2016; 7:10652. [PMID: 26879809 PMCID: PMC4757768 DOI: 10.1038/ncomms10652] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 01/06/2016] [Indexed: 01/04/2023] Open
Abstract
Amphetamines elevate extracellular dopamine, but the underlying mechanisms remain uncertain. Here we show in rodents that acute pharmacological inhibition of the vesicular monoamine transporter (VMAT) blocks amphetamine-induced locomotion and self-administration without impacting cocaine-induced behaviours. To study VMAT's role in mediating amphetamine action in dopamine neurons, we have used novel genetic, pharmacological and optical approaches in Drosophila melanogaster. In an ex vivo whole-brain preparation, fluorescent reporters of vesicular cargo and of vesicular pH reveal that amphetamine redistributes vesicle contents and diminishes the vesicle pH-gradient responsible for dopamine uptake and retention. This amphetamine-induced deacidification requires VMAT function and results from net H+ antiport by VMAT out of the vesicle lumen coupled to inward amphetamine transport. Amphetamine-induced vesicle deacidification also requires functional dopamine transporter (DAT) at the plasma membrane. Thus, we find that at pharmacologically relevant concentrations, amphetamines must be actively transported by DAT and VMAT in tandem to produce psychostimulant effects. Amphetamines are known to enhance extracellular dopamine levels, but the underlying mechanisms are unclear. Utilising a new pH biosensor for synaptic vesicles, the authors show that amphetamines diminish vesicle pH gradients, disrupting dopamine packaging and leading to increased neurotransmitter release.
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Affiliation(s)
- Zachary Freyberg
- Department of Psychiatry, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, USA
| | - Mark S Sonders
- Department of Psychiatry, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, USA.,Department of Neurology, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA
| | - Jenny I Aguilar
- Department of Psychiatry, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, USA
| | - Takato Hiranita
- Psychobiology Section, Intramural Research Program, Department of Health and Human Services, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, USA
| | - Caline S Karam
- Department of Psychiatry, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, USA
| | - Jorge Flores
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA
| | - Andrea B Pizzo
- Department of Psychiatry, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, USA
| | - Yuchao Zhang
- Department of Psychiatry, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, USA
| | - Zachary J Farino
- Department of Psychiatry, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, USA
| | - Audrey Chen
- Department of Psychiatry and Biobehavioral Sciences and Semel Institute for Neuroscience and Human Behavior, Hatos Center for Neuropharmacology, David Geffen School of Medicine University of California, Los Angeles, California 90095, USA
| | - Ciara A Martin
- UCLA Interdepartmental Program in Molecular Toxicology, University of California, Los Angeles, California 90095, USA
| | - Theresa A Kopajtic
- Psychobiology Section, Intramural Research Program, Department of Health and Human Services, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, USA
| | - Hao Fei
- Department of Psychiatry and Biobehavioral Sciences and Semel Institute for Neuroscience and Human Behavior, Hatos Center for Neuropharmacology, David Geffen School of Medicine University of California, Los Angeles, California 90095, USA
| | - Gang Hu
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Yi-Ying Lin
- School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Republic of China 10055
| | - Eugene V Mosharov
- Department of Neurology, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA
| | - Brian D McCabe
- Center for Motor Neuron Biology and Disease, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Department of Pathology and Cell Biology, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Department of Neuroscience, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA
| | - Robin Freyberg
- Department of Psychology, Stern College for Women, Yeshiva University, New York, New York 10016, USA
| | | | - Ling-Wei Hsin
- School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Republic of China 10055
| | - Dalibor Sames
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - David E Krantz
- Department of Psychiatry and Biobehavioral Sciences and Semel Institute for Neuroscience and Human Behavior, Hatos Center for Neuropharmacology, David Geffen School of Medicine University of California, Los Angeles, California 90095, USA
| | - Jonathan L Katz
- Psychobiology Section, Intramural Research Program, Department of Health and Human Services, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, USA
| | - David Sulzer
- Department of Psychiatry, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, USA.,Department of Neurology, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Department of Pharmacology, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA
| | - Jonathan A Javitch
- Department of Psychiatry, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, USA.,Department of Pharmacology, College of Physicians &Surgeons, Columbia University, New York, New York 10032, USA
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