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Dannaoui R, Hu R, Hu L, Tian ZQ, Svir I, Huang WH, Amatore C, Oleinick A. Vesicular neurotransmitters exocytosis monitored by amperometry: theoretical quantitative links between experimental current spikes shapes and intravesicular structures. Chem Sci 2024:d4sc04003a. [PMID: 39129778 PMCID: PMC11310864 DOI: 10.1039/d4sc04003a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2024] [Accepted: 07/30/2024] [Indexed: 08/13/2024] Open
Abstract
Single cell amperometry has proven to be a powerful and well-established method for characterizing single vesicular exocytotic events elicited at the level of excitable cells under various experimental conditions. Nevertheless, most of the reported characteristics are descriptive, being mostly concerned with the morphological characteristics of the recorded current spikes (maximum current intensities, released charge, rise and fall times, etc.) which are certainly important but do not provide sufficient kinetic information on exocytotic mechanisms due to lack of quantitative models. Here, continuing our previous efforts to provide rigorous models rationalizing the kinetic structures of frequently encountered spike types (spikes with unique exponential decay tails and kiss-and-run events), we describe a new theoretical approach enabling a quantitative kinetic modeling of all types of exocytotic events giving rise to current spikes exhibiting exponential decay tails. This model follows directly from the fact that the condensation of long intravesicular polyelectrolytic strands by high concentrations of monocationic neurotransmitter molecules leads to a matrix structure involving two compartments in constant kinetic exchanges during release. This kinetic model has been validated theoretically (direct and inverse problems) and its experimental interest established by the analysis of the amperometric spikes relative to chromaffin and PC12 cells previously published by some of us.
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Affiliation(s)
- Reina Dannaoui
- Département de Chimie, PASTEUR, Ecole Normale Supérieure, PSL Université, Sorbonne Université, CNRS 24 rue Lhomond Paris 75005 France
| | - Ren Hu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 P.R. China
| | - Lihui Hu
- Département de Chimie, PASTEUR, Ecole Normale Supérieure, PSL Université, Sorbonne Université, CNRS 24 rue Lhomond Paris 75005 France
| | - Zhong-Qun Tian
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 P.R. China
| | - Irina Svir
- Département de Chimie, PASTEUR, Ecole Normale Supérieure, PSL Université, Sorbonne Université, CNRS 24 rue Lhomond Paris 75005 France
| | - Wei-Hua Huang
- College of Chemistry and Molecular Sciences, Wuhan University Wuhan 430072 P.R. China
| | - Christian Amatore
- Département de Chimie, PASTEUR, Ecole Normale Supérieure, PSL Université, Sorbonne Université, CNRS 24 rue Lhomond Paris 75005 France
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 P.R. China
| | - Alexander Oleinick
- Département de Chimie, PASTEUR, Ecole Normale Supérieure, PSL Université, Sorbonne Université, CNRS 24 rue Lhomond Paris 75005 France
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2
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Colin C, Levallois P, Botsos-Margerit U, Clément F, Zigah D, Arbault S. Easy cleaning plus stable activation of glassy carbon electrode surface by oxygen plasma. Bioelectrochemistry 2023; 154:108551. [PMID: 37677984 DOI: 10.1016/j.bioelechem.2023.108551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 08/24/2023] [Accepted: 08/25/2023] [Indexed: 09/09/2023]
Abstract
Glassy carbon (GC) electrodes are widely used in electroanalytical applications especially in bioelectrochemistry. Their use starts with an efficient surface cleaning and activation protocol, mostly based on surface polishing steps. We studied the use of an oxygen plasma exposure of GC electrodes to replace common polishing procedures. The cyclic voltammetry (CV) responses of ferrocyanide and ferrocene-dimethanol were used to compare brand new, surface-polished and plasma-treated GC electrodes. Plasma treatment induces CV responses with improved features, close to theoretical values, as compared to other methods. The plasma effects were quasi-stable over a week when electrodes were stored in water, this being explained by increased surface energy and hydrophilicity. Furthermore, when electroreduction of diazonium was performed on GC electrodes, the surface blockade could be removed by the plasma. Thus, a short oxygen plasma treatment is prone to replace polishing protocols, that display person-dependent efficiency, in most of the experiments with GC electrodes.
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Affiliation(s)
- Camille Colin
- Univ. Bordeaux, Bordeaux INP, CNRS, ISM, UMR 5255, F-33400 Talence, France
| | - Pierre Levallois
- Univ. Bordeaux, Bordeaux INP, CNRS, ISM, UMR 5255, F-33400 Talence, France
| | | | - Franck Clément
- Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM UMR 5254, 64600 Anglet, France
| | - Dodzi Zigah
- Univ. Bordeaux, Bordeaux INP, CNRS, ISM, UMR 5255, F-33400 Talence, France; Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers, CNRS, F-86073 Poitiers, France.
| | - Stéphane Arbault
- Univ. Bordeaux, Bordeaux INP, CNRS, ISM, UMR 5255, F-33400 Talence, France; Univ. Bordeaux, CNRS, Bordeaux INP, CBMN, UMR 5248, F-33600 Pessac, France.
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3
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Su R, Wang S, McDargh Z, O'Shaughnessy B. Three membrane fusion pore families determine the pathway to pore dilation. Biophys J 2023; 122:3986-3998. [PMID: 37644721 PMCID: PMC10560699 DOI: 10.1016/j.bpj.2023.08.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 06/19/2023] [Accepted: 08/25/2023] [Indexed: 08/31/2023] Open
Abstract
During exocytosis secretory vesicles fuse with a target membrane and release neurotransmitters, hormones, or other bioactive molecules through a membrane fusion pore. The initially small pore may subsequently dilate for full contents release, as commonly observed in amperometric traces. The size, shape, and evolution of the pore is critical to the course of contents release, but exact fusion pore solutions accounting for membrane tension and bending energy constraints have not been available. Here, we obtained exact solutions for fusion pores between two membranes. We find three families: a narrow pore, a wide pore, and an intermediate tether-like pore. For high tensions these are close to the catenoidal and tether solutions recently reported for freely hinged membrane boundaries. We suggest membrane fusion initially generates a stable narrow pore, and the dilation pathway is a transition to the stable wide pore family. The unstable intermediate pore is the transition state that sets the energy barrier for this dilation pathway. Pore dilation is mechanosensitive, as the energy barrier is lowered by increased membrane tension. Finally, we study fusion pores in nanodiscs, powerful systems for the study of individual pores. We show that nanodiscs stabilize fusion pores by locking them into the narrow pore family.
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Affiliation(s)
- Rui Su
- Department of Chemical Engineering, Columbia University, New York City, New York
| | - Shuyuan Wang
- Department of Chemical Engineering, Columbia University, New York City, New York; Department of Physics, Columbia University, New York City, New York
| | - Zachary McDargh
- Department of Chemical Engineering, Columbia University, New York City, New York
| | - Ben O'Shaughnessy
- Department of Chemical Engineering, Columbia University, New York City, New York.
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4
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Cohen R, Mukai C, Nelson JL, Zenilman SS, Sosnicki DM, Travis AJ. A genetically targeted sensor reveals spatial and temporal dynamics of acrosomal calcium and sperm acrosome exocytosis. J Biol Chem 2022; 298:101868. [PMID: 35346690 PMCID: PMC9046242 DOI: 10.1016/j.jbc.2022.101868] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 03/19/2022] [Accepted: 03/23/2022] [Indexed: 01/16/2023] Open
Abstract
Secretion of the acrosome, a single vesicle located rostrally in the head of a mammalian sperm, through a process known as "acrosome exocytosis" (AE), is essential for fertilization. However, the mechanisms leading to and regulating this complex process are controversial. In particular, poor understanding of Ca2+ dynamics between sperm subcellular compartments and regulation of membrane fusion mechanisms have led to competing models of AE. Here, we developed a transgenic mouse expressing an Acrosome-targeted Sensor for Exocytosis (AcroSensE) to investigate the spatial and temporal Ca2+ dynamics in AE in live sperm. AcroSensE combines a genetically encoded Ca2+ indicator (GCaMP) fused with an mCherry indicator to spatiotemporally resolve acrosomal Ca2+ rise (ACR) and membrane fusion events, enabling real-time study of AE. We found that ACR is dependent on extracellular Ca2+ and that ACR precedes AE. In addition, we show that there are intermediate steps in ACR and that AE correlates better with the ACR rate rather than absolute Ca2+ amount. Finally, we demonstrate that ACR and membrane fusion progression kinetics and spatial patterns differ with different stimuli and that sites of initiation of ACR and sites of membrane fusion do not always correspond. These findings support a model involving functionally redundant pathways that enable a highly regulated, multistep AE in heterogeneous sperm populations, unlike the previously proposed "acrosome reaction" model.
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Affiliation(s)
- Roy Cohen
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
| | - Chinatsu Mukai
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Jacquelyn L Nelson
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Shoshana S Zenilman
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Danielle M Sosnicki
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Alexander J Travis
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA; Department of Public and Ecosystem Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
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5
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Aref M, Ranjbari E, Romiani A, Ewing AG. Intracellular injection of phospholipids directly alters exocytosis and the fraction of chemical release in chromaffin cells as measured by nano-electrochemistry. Chem Sci 2020; 11:11869-11876. [PMID: 34123212 PMCID: PMC8162797 DOI: 10.1039/d0sc03683h] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 10/06/2020] [Indexed: 12/02/2022] Open
Abstract
Using a nano-injection method, we introduced phospholipids having different intrinsic geometries into single secretory cells and used single cell amperometry (SCA) and intracellular vesicle impact electrochemical cytometry (IVIEC) with nanotip electrodes to monitor the effects of intracellular incubation on the exocytosis process and vesicular storage. Combining tools, this work provides new information to understand the impact of intracellular membrane lipid engineering on exocytotic release, vesicular content and fraction of chemical release. We also assessed the effect of membrane lipid alteration on catecholamine storage of isolated vesicles by implementing another amperometric technique, vesicle impact electrochemical cytometry (VIEC), outside the cell. Exocytosis analysis reveals that the intracellular nano-injection of phosphatidylcholine and lysophosphatidylcholine decreases the number of released catecholamines, whereas phosphatidylethanolamine shows the opposite effect. These observations support the emerging hypothesis that lipid curvature results in membrane remodeling through secretory pathways, and also provide new evidence for a critical role of the lipid localization in modulating the release process. Interestingly, the IVIEC data imply that total vesicular content is also affected by in situ supplementation of the cells with some lipids, while, the corresponding VIEC results show that the neurotransmitter content in isolated vesicles is not affected by altering the vesicle membrane lipids. This suggests that the intervention of phospholipids inside the cell has its effect on the cellular machinery for vesicle release rather than vesicle structure, and leads to the somewhat surprising conclusion that modulating release has a direct effect on vesicle structure, which is likely due to the vesicles opening and closing again during exocytosis. These findings could lead to a novel regulatory mechanism for the exocytotic or synaptic strength based on lipid heterogeneity across the cell membrane.
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Affiliation(s)
- Mohaddeseh Aref
- Department of Chemistry and Molecular Biology, University of Gothenburg Gothenburg Sweden
| | - Elias Ranjbari
- Department of Chemistry and Molecular Biology, University of Gothenburg Gothenburg Sweden
| | - Armaghan Romiani
- Department of Chemistry and Molecular Biology, University of Gothenburg Gothenburg Sweden
| | - Andrew G Ewing
- Department of Chemistry and Molecular Biology, University of Gothenburg Gothenburg Sweden
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He X, Ewing AG. Counteranions in the Stimulation Solution Alter the Dynamics of Exocytosis Consistent with the Hofmeister Series. J Am Chem Soc 2020; 142:12591-12595. [PMID: 32598145 PMCID: PMC7386575 DOI: 10.1021/jacs.0c05319] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
![]()
We
show that the Hofmeister series of ions can be used to explain
the cellular changes in exocytosis observed by single-cell amperometry
for different counteranions. The formation, expansion, and closing
of the membrane fusion pore during exocytosis was found to be strongly
dependent on the counteranion species in solution. With stimulation
of chaotropic anions (e.g., ClO4–), the
expansion and closing time of the fusion pore are longer, suggesting
chaotropes can extend the duration of exocytosis compared with kosmotropic
anions (e.g., Cl–). At a concentration of 30 mM,
the two parameters (e.g., t1/2 and tfall) that define the duration of exocytosis
vary with the Hofmeister series (Cl– < Br– < NO3– ≤ ClO4– < SCN–). More interestingly,
fewer (e.g., Nfoot/Nevents) and smaller (e.g., Ifoot) prespike events are observed when chaotropes are counterions in
the stimulation solution, and the values can be sorted by the reverse
Hofmeister series (Cl– ≥ Br– > NO3– > ClO4– > SCN–). Based on ion specificity,
an adsorption-repulsion
mechanism, we suggest that the exocytotic Hofmeister series effect
originates from a looser swelling lipid bilayer structure due to the
adsorption and electrostatic repulsion of chaotropes on the hydrophobic
portion of the membrane. Our results provide a chemical link between
the Hofmeister series and the cellular process of neurotransmitter
release via exocytosis and provide a better physical framework to
understand this important phenomenon.
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Affiliation(s)
- Xiulan He
- Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden
| | - Andrew G Ewing
- Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden
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7
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Keighron JD, Wang Y, Cans AS. Electrochemistry of Single-Vesicle Events. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2020; 13:159-181. [PMID: 32151142 DOI: 10.1146/annurev-anchem-061417-010032] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Neuronal transmission relies on electrical signals and the transfer of chemical signals from one neuron to another. Chemical messages are transmitted from presynaptic neurons to neighboring neurons through the triggered fusion of neurotransmitter-filled vesicles with the cell plasma membrane. This process, known as exocytosis, involves the rapid release of neurotransmitter solutions that are detected with high affinity by the postsynaptic neuron. The type and number of neurotransmitters released and the frequency of vesicular events govern brain functions such as cognition, decision making, learning, and memory. Therefore, to understand neurotransmitters and neuronal function, analytical tools capable of quantitative and chemically selective detection of neurotransmitters with high spatiotemporal resolution are needed. Electrochemistry offers powerful techniques that are sufficiently rapid to allow for the detection of exocytosis activity and provides quantitative measurements of vesicle neurotransmitter content and neurotransmitter release from individual vesicle events. In this review, we provide an overview of the most commonly used electrochemical methods for monitoring single-vesicle events, including recent developments and what is needed for future research.
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Affiliation(s)
- Jacqueline D Keighron
- Department of Chemical and Biological Sciences, New York Institute of Technology, Old Westbury, New York 11568, USA
| | - Yuanmo Wang
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden;
| | - Ann-Sofie Cans
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden;
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8
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Plasticity in exocytosis revealed through the effects of repetitive stimuli affect the content of nanometer vesicles and the fraction of transmitter released. Proc Natl Acad Sci U S A 2019; 116:21409-21415. [PMID: 31570594 DOI: 10.1073/pnas.1910859116] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Electrochemical techniques with disk and nano-tip electrodes, together with calcium imaging, were used to examine the effect of short-interval repetitive stimuli on both exocytosis and vesicular content in a model cell line. We show that the number of events decreases markedly with repeated stimuli suggesting a depletion of exocytosis machinery. However, repetitive stimuli induce a more stable fusion pore, leading to an increased amount of neurotransmitter release. In contrast, the total neurotransmitter content inside the vesicles decreases after repetitive stimuli, resulting in a higher average release fraction from each event. We suggest a possible mechanism regarding a link between activity-induced plasticity and fraction of release.
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9
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Zhang F, Guan Y, Yang Y, Hunt A, Wang S, Chen HY, Tao N. Optical Tracking of Nanometer-Scale Cellular Membrane Deformation Associated with Single Vesicle Release. ACS Sens 2019; 4:2205-2212. [PMID: 31348853 DOI: 10.1021/acssensors.9b01201] [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] [Indexed: 01/30/2023]
Abstract
Exocytosis involves interactions between secretory vesicles and the plasma membrane. Studying the membrane response is thus critical to understand this important cellular process and to differentiate different mediator release patterns. Here we introduce a label-free optical imaging method to detect the vesicle-membrane-interaction-induced membrane deformation associated with single exocytosis in mast cells. We show that the plasma membrane expands by a few tens of nanometers accompanying each vesicle-release event, but the dynamics of the membrane deformation varies from cell to cell, which reflect different exocytosis processes. Combining the temporal and spatial information allows us to resolve complex vesicle-release processes, such as two vesicle-release events that occur closely in time and location. Simultaneous following a vesicle release with fluorescence and membrane deformation tracking further allows us to determine the propagation speed of the vesicle-release-induced membrane deformation along the cell surface, which has an average value of 5.2 ± 1.8 μm/s.
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Affiliation(s)
- Fenni Zhang
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
- School of Electrical Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287, United States
| | - Yan Guan
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
- School of Electrical Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287, United States
| | - Yunze Yang
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
- School of Electrical Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287, United States
| | - Ashley Hunt
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
| | - Shaopeng Wang
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
| | - Hong-Yuan Chen
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
| | - Nongjian Tao
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
- School of Electrical Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287, United States
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10
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Shen M, Qu Z, DesLaurier J, Welle TM, Sweedler JV, Chen R. Single Synaptic Observation of Cholinergic Neurotransmission on Living Neurons: Concentration and Dynamics. J Am Chem Soc 2018; 140:7764-7768. [PMID: 29883110 DOI: 10.1021/jacs.8b01989] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Acetylcholine, the first neurotransmitter identified more than a century ago, plays critical roles in human activities and health; however, its synaptic concentration dynamics have remained unknown. Here, we demonstrate the in situ simultaneous measurements of synaptic cholinergic transmitter concentration and release dynamics. We used nanoscale electroanalytical methods: nanoITIES electrode of 15 nm in radius and nanoresolved scanning electrochemical microscopy (SECM). Time-resolved in situ measurements unveiled information on synaptic acetylcholine concentration and release dynamics of living Aplysia neurons. The measuring technique enabled the quantitative sensing of acetylcholine with negligible interference of other ionic and redox-active species. We measured cholinergic transmitter concentrations very close to the synapse, with values as high as 2.4 mM. We observed diverse synaptic transmitter concentration dynamics consisting of singlet, doublet and multiplet events with a signal-to-noise ratio of 6 to 130. The unprecedented details about synaptic neurotransmission unveiled are instrumental for understanding brain communication and diseases in a way distinctive from extra-synaptic studies.
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Affiliation(s)
- Mei Shen
- Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Matthews Avenue , Urbana , Illinois 61801 , United States
| | - Zizheng Qu
- Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Matthews Avenue , Urbana , Illinois 61801 , United States
| | - Justin DesLaurier
- Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Matthews Avenue , Urbana , Illinois 61801 , United States
| | - Theresa M Welle
- Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Matthews Avenue , Urbana , Illinois 61801 , United States
| | - Jonathan V Sweedler
- Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Matthews Avenue , Urbana , Illinois 61801 , United States
| | - Ran Chen
- Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Matthews Avenue , Urbana , Illinois 61801 , United States
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11
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Fathali H, Cans AS. Amperometry methods for monitoring vesicular quantal size and regulation of exocytosis release. Pflugers Arch 2017; 470:125-134. [PMID: 28951968 PMCID: PMC5748430 DOI: 10.1007/s00424-017-2069-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 09/12/2017] [Accepted: 09/14/2017] [Indexed: 11/30/2022]
Abstract
Chemical signaling strength during intercellular communication can be regulated by secretory cells through controlling the amount of signaling molecules that are released from a secretory vesicle during the exocytosis process. In addition, the chemical signal can also be influenced by the amount of neurotransmitters that is accumulated and stored inside the secretory vesicle compartment. Here, we present the development of analytical methodologies and cell model systems that have been applied in neuroscience research for gaining better insights into the biophysics and the molecular mechanisms, which are involved in the regulatory aspects of the exocytosis machinery affecting the output signal of chemical transmission at neuronal and neuroendocrine cells.
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Affiliation(s)
- Hoda Fathali
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 42196, Gothenburg, Sweden
| | - Ann-Sofie Cans
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 42196, Gothenburg, Sweden.
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12
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Ren L, Pour MD, Majdi S, Li X, Malmberg P, Ewing AG. Zinc Regulates Chemical-Transmitter Storage in Nanometer Vesicles and Exocytosis Dynamics as Measured by Amperometry. Angew Chem Int Ed Engl 2017; 56:4970-4975. [PMID: 28319311 PMCID: PMC5540326 DOI: 10.1002/anie.201700095] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Indexed: 01/12/2023]
Abstract
We applied electrochemical techniques with nano-tip electrodes to show that micromolar concentrations of zinc not only trigger changes in the dynamics of exocytosis, but also vesicle content in a model cell line. The vesicle catecholamine content in PC12 cells is significantly decreased after 100 μm zinc treatment, but, catecholamine release during exocytosis remains nearly the same. This contrasts with the number of molecules stored in the exocytosis vesicles, which decreases, and we find that the amount of catecholamine released from zinc-treated cells reaches nearly 100 % content expelled. Further investigation shows that zinc slows down exocytotic release. Our results provide the missing link between zinc and the regulation of neurotransmitter release processes, which might be important in memory formation and storage.
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Affiliation(s)
- Lin Ren
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Masoumeh Dowlatshahi Pour
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
- National Center for Imaging Mass Spectrometry, Chalmers University of Technology and Gothenburg University, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Soodabeh Majdi
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Xianchan Li
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Per Malmberg
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
- National Center for Imaging Mass Spectrometry, Chalmers University of Technology and Gothenburg University, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Andrew G Ewing
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
- National Center for Imaging Mass Spectrometry, Chalmers University of Technology and Gothenburg University, Kemivägen 10, 412 96, Gothenburg, Sweden
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivägen 10, 412 96, Gothenburg, Sweden
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13
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Ren L, Pour MD, Majdi S, Li X, Malmberg P, Ewing AG. Zinc Regulates Chemical-Transmitter Storage in Nanometer Vesicles and Exocytosis Dynamics as Measured by Amperometry. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201700095] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Lin Ren
- Department of Chemistry and Chemical Engineering; Chalmers University of Technology; Kemivägen 10 412 96 Gothenburg Sweden
| | - Masoumeh Dowlatshahi Pour
- Department of Chemistry and Chemical Engineering; Chalmers University of Technology; Kemivägen 10 412 96 Gothenburg Sweden
- National Center for Imaging Mass Spectrometry; Chalmers University of Technology and Gothenburg University; Kemivägen 10 412 96 Gothenburg Sweden
| | - Soodabeh Majdi
- Department of Chemistry and Molecular Biology; University of Gothenburg; Kemivägen 10 412 96 Gothenburg Sweden
| | - Xianchan Li
- Department of Chemistry and Molecular Biology; University of Gothenburg; Kemivägen 10 412 96 Gothenburg Sweden
| | - Per Malmberg
- Department of Chemistry and Chemical Engineering; Chalmers University of Technology; Kemivägen 10 412 96 Gothenburg Sweden
- National Center for Imaging Mass Spectrometry; Chalmers University of Technology and Gothenburg University; Kemivägen 10 412 96 Gothenburg Sweden
| | - Andrew G. Ewing
- Department of Chemistry and Chemical Engineering; Chalmers University of Technology; Kemivägen 10 412 96 Gothenburg Sweden
- National Center for Imaging Mass Spectrometry; Chalmers University of Technology and Gothenburg University; Kemivägen 10 412 96 Gothenburg Sweden
- Department of Chemistry and Molecular Biology; University of Gothenburg; Kemivägen 10 412 96 Gothenburg Sweden
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Finkenstaedt-Quinn SA, Gruba SM, Haynes CL. Variations in Fusion Pore Formation in Cholesterol-Treated Platelets. Biophys J 2016; 110:922-9. [PMID: 26910428 DOI: 10.1016/j.bpj.2015.12.034] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 12/21/2015] [Accepted: 12/31/2015] [Indexed: 11/24/2022] Open
Abstract
Exocytosis is a highly regulated intercellular communication process involving various membrane proteins, lipids, and cytoskeleton restructuring. These components help control granule fusion with the cell membrane, creating a pore through which granular contents are released into the extracellular environment. Platelets are an ideal model system for studying exocytosis due to their lack of a nucleus, resulting in decreased membrane regulation in response to cellular changes. In addition, platelets contain fewer granules than most other exocytosing cells, allowing straightforward measurement of individual granule release with carbon-fiber microelectrode amperometry. This technique monitors the concentration of serotonin, an electroactive molecule found in the dense-body granules of platelets, released as a function of time, with 50 μs time resolution, revealing biophysical characteristics of the fundamental exocytotic process. Variations in fusion pore formation and closure cause deviations from the classic current versus time spike profile and may influence diffusion of serotonin molecules from the site of granule fusion. Physiologically, the delivery of smaller packets of chemical messengers or the prolonged delivery of chemical messengers may represent how cells/organisms tune biological response. The goals of this work are twofold: 1) to categorize secretion features that deviate from the traditional mode of secretion and 2) to examine how changing the cholesterol composition of the platelet membrane results in changes in the pore formation process. Results herein indicate that the expected traditional mode of release is actually in the minority of granule content release events. In addition, results indicate that as the cholesterol content of the plasma membrane is increased, pore opening is less continuous.
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Affiliation(s)
| | - Sarah M Gruba
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota
| | - Christy L Haynes
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota.
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15
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Abstract
Exocytosis is the fundamental process by which cells communicate with each other. The events that lead up to the fusion of a vesicle loaded with chemical messenger with the cell membrane were the subject of a Nobel Prize in 2013. However, the processes occurring after the initial formation of a fusion pore are very much still in debate. The release of chemical messenger has traditionally been thought to occur through full distention of the vesicle membrane, hence assuming exocytosis to be all or none. In contrast to the all or none hypothesis, here we discuss the evidence that during exocytosis the vesicle-membrane pore opens to release only a portion of the transmitter content during exocytosis and then close again. This open and closed exocytosis is distinct from kiss-and-run exocytosis, in that it appears to be the main content released during regular exocytosis. The evidence for this partial release via open and closed exocytosis is presented considering primarily the quantitative evidence obtained with amperometry.
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16
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Keighron JD, Wigström J, Kurczy ME, Bergman J, Wang Y, Cans AS. Amperometric detection of single vesicle acetylcholine release events from an artificial cell. ACS Chem Neurosci 2015; 6:181-8. [PMID: 25565357 DOI: 10.1021/cn5002667] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Acetylcholine is a highly abundant nonelectroactive neurotransmitter in the mammalian central nervous system. Neurochemical release occurs on the millisecond time scale, requiring a fast, sensitive sensor such as an enzymatic amperometric electrode. Typically, the enzyme used for enzymatic electrochemical sensors is applied in excess to maximize signal. Here, in addition to sensitivity, we have also sought to maximize temporal resolution, by designing a sensor that is sensitive enough to work at near monolayer enzyme coverage. Reducing the enzyme layer thickness increases sensor temporal resolution by decreasing the distance and reducing the diffusion time for the enzyme product to travel to the sensor surface for detection. In this instance, the sensor consists of electrodeposited gold nanoparticle modified carbon fiber microelectrodes (CFMEs). Enzymes often are sensitive to curvature upon surface adsorption; thus, it was important to deposit discrete nanoparticles to maintain enzyme activity while depositing as much gold as possible to maximize enzyme coverage. To further enhance sensitivity, the enzymes acetylcholinesterase (AChE) and choline oxidase (ChO) were immobilized onto the gold nanoparticles at the previously determined optimal ratio (1:10 AChE/ChO) for most efficient sequential enzymatic activity. This optimization approach has enabled the rapid detection to temporally resolve single vesicle acetylcholine release from an artificial cell. The sensor described is a significant advancement in that it allows for the recording of acetylcholine release on the order of the time scale for neurochemical release in secretory cells.
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Affiliation(s)
- Jacqueline D. Keighron
- Department
of Chemical and Biological Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Joakim Wigström
- Department
of Chemical and Biological Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Michael E. Kurczy
- Department
of Chemical and Biological Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Jenny Bergman
- Department
of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden
| | - Yuanmo Wang
- Department
of Chemical and Biological Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Ann-Sofie Cans
- Department
of Chemical and Biological Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden
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17
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Amperometric detection of vesicular exocytosis from BON cells at carbon fiber microelectrodes. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2013.07.110] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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18
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Eloul S, Compton RG. Shielding of a Microdisc Electrode Surrounded by an Adsorbing Surface. ChemElectroChem 2014. [DOI: 10.1002/celc.201400005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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19
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20
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Fhaner MJ, Galligan JJ, Swain GM. Increased catecholamine secretion from single adrenal chromaffin cells in DOCA-salt hypertension is associated with potassium channel dysfunction. ACS Chem Neurosci 2013; 4:1404-13. [PMID: 23937098 DOI: 10.1021/cn400115v] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The mechanism of catecholamine release from single adrenal chromaffin cells isolated from normotensive and DOCA-salt hypertensive rats was investigated. These cells were used as a model for sympathetic nerves to better understand how exocytotic release of catecholamines is altered in this model of hypertension. Catecholamine secretion was evoked by local application of acetylcholine (1 mM) or high K+ (70 mM), and continuous amperometry was used to monitor catecholamine secretion as an oxidative current. The total number of catecholamine molecules secreted from a vesicle, the total number of vesicles fusing and secreting, and the duration of secretion in response to a stimulus were all significantly greater for chromaffin cells from hypertensive rats as compared to normotensive controls. The greater catecholamine secretion from DOCA-salt cells results, at least in part, from functionally impaired large conductance, Ca2+-activated (BK) and ATP-sensitive K+ channels. This work reveals that there is altered vesicular release of catecholamines from these cells (and possibly from perivascular sympathetic nerves) and this may contribute to increased vasomotor tone in DOCA-salt hypertension.
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Affiliation(s)
- Matthew J. Fhaner
- Department of Chemistry, ‡Department of Pharmacology and Toxicology, and §The Neuroscience
Program, Michigan State University, East Lansing, Michigan 48824, United States
| | - James J. Galligan
- Department of Chemistry, ‡Department of Pharmacology and Toxicology, and §The Neuroscience
Program, Michigan State University, East Lansing, Michigan 48824, United States
| | - Greg M. Swain
- Department of Chemistry, ‡Department of Pharmacology and Toxicology, and §The Neuroscience
Program, Michigan State University, East Lansing, Michigan 48824, United States
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21
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Oleinick A, Lemaître F, Collignon MG, Svir I, Amatore C. Vesicular release of neurotransmitters: converting amperometric measurements into size, dynamics and energetics of initial fusion pores. Faraday Discuss 2013; 164:33-55. [DOI: 10.1039/c3fd00028a] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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22
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Abstract
The basis for communication between nerve cells lies in the process of exocytosis, the fusion of neurotransmitter filled vesicles with the cell membrane resulting in release of the signaling molecules. Even though much is known about this process, the extent that the vesicles are emptied upon fusion is a topic that is being debated. We have analyzed amperometric peaks corresponding to release at PC12 cells and find stable plateau currents during the decay of peaks, indicating closing of the vesicle after incomplete release of its content. Using lipid incubations to alter the amount of transmitter released we were able to estimate the initial vesicular content, and from that, the fraction of release. We propose a process for most exocytosis events where the vesicle partially opens to release transmitter and then closes directly again, leaving the possibility for regulation of transmission within events.
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23
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Reed JA, Love SA, Lucero AE, Haynes CL, Canavan HE. Effect of polymer deposition method on thermoresponsive polymer films and resulting cellular behavior. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:2281-7. [PMID: 21506526 PMCID: PMC3978603 DOI: 10.1021/la102606k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Poly(N-isopropyl acrylamide) or pNIPAM is a thermoresponsive polymer that is widely studied for use in bioengineering applications. The interest in this polymer lies in the polymer's unique capability to undergo a sharp property change near physiological temperature, which aids in the spontaneous release of biological cells from substrates. Currently, there are many methods for depositing pNIPAM onto substrates, including atom-transfer radical polymerization (ATRP) and electron beam ionization. Each method yields pNIPAM-coated substrates with different surface characteristics that can influence cell behavior. In this work, we compare two methods of pNIPAM deposition: plasma deposition and codeposition with a sol-gel. The resulting pNIPAM films were analyzed for use as substrates for mammalian cell culture based on surface characterization (XPS, ToF-SIMS, AFM, contact angles), cell attachment/detachment studies, and an analysis of exocytosis function using carbon-fiber microelectrode amperometry (CFMA). We find that although both methods are useful for the deposition of functional pNIPAM films, plasma deposition is much preferred for cell-sheet engineering applications because of the films' thermoresponse, minimal change in cell density, and maintenance of supported cell exocytosis function.
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Affiliation(s)
- JA Reed
- Center for Biomedical Engineering, University of New Mexico
- Department of Chemical and Nuclear Engineering, University of New Mexico
| | - SA Love
- Department of Chemistry, University of Minnesota
| | - AE Lucero
- Center for Biomedical Engineering, University of New Mexico
- Department of Chemical and Nuclear Engineering, University of New Mexico
| | - CL Haynes
- Department of Chemistry, University of Minnesota
| | - HE Canavan
- Center for Biomedical Engineering, University of New Mexico
- Department of Chemical and Nuclear Engineering, University of New Mexico
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24
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Zanin MP, Phillips L, Mackenzie KD, Keating DJ. Aging differentially affects multiple aspects of vesicle fusion kinetics. PLoS One 2011; 6:e27820. [PMID: 22125627 PMCID: PMC3220683 DOI: 10.1371/journal.pone.0027820] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Accepted: 10/26/2011] [Indexed: 12/03/2022] Open
Abstract
How fusion pore formation during exocytosis affects the subsequent release of vesicle contents remains incompletely understood. It is unclear if the amount released per vesicle is dependent upon the nature of the developing fusion pore and whether full fusion and transient kiss and run exocytosis are regulated by similar mechanisms. We hypothesise that if consistent relationships exist between these aspects of exocytosis then they will remain constant across any age. Using amperometry in mouse chromaffin cells we measured catecholamine efflux during single exocytotic events at P0, 1 month and 6 months. At all ages we observed full fusion (amperometric spike only), full fusion preceded by fusion pore flickering (pre-spike foot (PSF) signal followed by a spike) and pure “kiss and run” exocytosis (represented by stand alone foot (SAF) signals). We observe age-associated increases in the size of all 3 modes of fusion but these increases occur at different ages. The release probability of PSF signals or full spikes alone doesn't alter across any age in comparison with an age-dependent increase in the incidence of “kiss and run” type events. However, the most striking changes we observe are age-associated changes in the relationship between vesicle size and the membrane bending energy required for exocytosis. Our data illustrates that vesicle size does not regulate release probability, as has been suggested, that membrane elasticity or flexural rigidity change with age and that the mechanisms controlling full fusion may differ from those controlling “kiss and run” fusion.
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Affiliation(s)
- Mark P. Zanin
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Lucy Phillips
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Kimberly D. Mackenzie
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Damien J. Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
- * E-mail:
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25
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Batchelor-McAuley C, Dickinson EJF, Rees NV, Toghill KE, Compton RG. New Electrochemical Methods. Anal Chem 2011; 84:669-84. [DOI: 10.1021/ac2026767] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christopher Batchelor-McAuley
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - Edmund J. F. Dickinson
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - Neil V. Rees
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - Kathryn E. Toghill
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom
| | - Richard G. Compton
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom
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26
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Kim D, Koseoglu S, Manning BM, Meyer AF, Haynes CL. Electroanalytical eavesdropping on single cell communication. Anal Chem 2011; 83:7242-9. [PMID: 21766792 PMCID: PMC3184337 DOI: 10.1021/ac200666c] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This article reviews measurement of single cell exocytosis with microelectrodes, covering history, basic instrumentation, cell types investigated, and fundamental insight gained.
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27
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Affiliation(s)
- Yuqing Lin
- Department of Chemistry, University of Gothenburg, S-41296, Gothenburg, Sweden
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28
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Friedrich R, Ashery U. From spike to graph--a complete automated single-spike analysis. J Neurosci Methods 2010; 193:271-80. [PMID: 20869399 DOI: 10.1016/j.jneumeth.2010.09.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Revised: 09/06/2010] [Accepted: 09/13/2010] [Indexed: 11/16/2022]
Abstract
Amperometry is a commonly used technique for detecting the kinetics of single-vesicle exocytosis with excellent temporal and spatial resolution. However, different methods of analyzing the amperometric signals can produce conflicting conclusions. We developed an efficient automated method for kinetics analysis of single spikes that does not filter the data and therefore prevents distortion of the results. The algorithm assesses the signal-to-noise ratios (SNRs) and accordingly, separates the signals using an adjustable two-threshold calculation. This enables comparing data with different SNRs from different setups. The software also includes a complete statistical analysis, with an automated selection of the most appropriate statistical tests and a graphical representation. The algorithms can be used for any other experimental results requiring the separation of signals from noise, making this method useful for many applications.
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Affiliation(s)
- Reut Friedrich
- Department of Neurobiology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv, Israel.
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29
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Amatore C, Oleinick AI, Svir I. Reconstruction of aperture functions during full fusion in vesicular exocytosis of neurotransmitters. Chemphyschem 2010; 11:159-74. [PMID: 19937905 DOI: 10.1002/cphc.200900647] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Individual vesicular exocytosis of adrenaline by dense core vesicles in chromaffin cells is considered here as a paradigm of many situations encountered in biology, nanosciences and drug delivery in which a spherical container releases in the external environment through gradual uncovering of its surface. A procedure for extracting the aperture (opening) function of a biological vesicle fusing with a cell membrane from the released molecular flux of neurotransmitter as monitored by amperometry has been devised based on semi-analytical expressions derived in a former work [C. Amatore, A. I. Oleinick, I. Svir, ChemPhysChem 2009, 10, DOI: 10.1002/cphc.200900646]. This precise analysis shows that in the absence of direct information about the radius of the vesicle or about the concentration of the adrenaline cation stored by the vesicle matrix, current spikes do not contain enough information to determine the maximum aperture angle. Yet, a statistical analysis establishes that this maximum aperture angle is most probably less than a few tens of degrees, which suggests that full fusion is a very improbable event.
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Affiliation(s)
- Christian Amatore
- Département de Chimie, Ecole Normale Supérieure, UMR CNRS-ENS-UPMC 8640 Pasteur, 24 rue Lhomond, 75231 Paris Cedex 05, France.
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