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Adinolfi E, De Marchi E, Grignolo M, Szymczak B, Pegoraro A. The P2X7 Receptor in Oncogenesis and Metastatic Dissemination: New Insights on Vesicular Release and Adenosinergic Crosstalk. Int J Mol Sci 2023; 24:13906. [PMID: 37762206 PMCID: PMC10531279 DOI: 10.3390/ijms241813906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 09/01/2023] [Accepted: 09/05/2023] [Indexed: 09/29/2023] Open
Abstract
The tumor niche is an environment rich in extracellular ATP (eATP) where purinergic receptors have essential roles in different cell subtypes, including cancer, immune, and stromal cells. Here, we give an overview of recent discoveries regarding the role of probably the best-characterized purinergic receptor in the tumor microenvironment: P2X7. We cover the activities of the P2X7 receptor and its human splice variants in solid and liquid cancer proliferation, dissemination, and crosstalk with immune and endothelial cells. Particular attention is paid to the P2X7-dependent release of microvesicles and exosomes, their content, including ATP and miRNAs, and, in general, P2X7-activated mechanisms favoring metastatic spread and niche conditioning. Moreover, the emerging role of P2X7 in influencing the adenosinergic axis, formed by the ectonucleotidases CD39 and CD73 and the adenosine receptor A2A in cancer, is analyzed. Finally, we cover how antitumor therapy responses can be influenced by or can change P2X7 expression and function. This converging evidence suggests that P2X7 is an attractive therapeutic target for oncological conditions.
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Affiliation(s)
- Elena Adinolfi
- Section of Experimental Medicine, Department of Medical Sciences, University of Ferrara, 44121 Ferrara, Italy; (E.D.M.); (M.G.); (A.P.)
| | - Elena De Marchi
- Section of Experimental Medicine, Department of Medical Sciences, University of Ferrara, 44121 Ferrara, Italy; (E.D.M.); (M.G.); (A.P.)
| | - Marianna Grignolo
- Section of Experimental Medicine, Department of Medical Sciences, University of Ferrara, 44121 Ferrara, Italy; (E.D.M.); (M.G.); (A.P.)
| | - Bartosz Szymczak
- Department of Biochemistry, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University in Torun, 87-100 Torun, Poland;
| | - Anna Pegoraro
- Section of Experimental Medicine, Department of Medical Sciences, University of Ferrara, 44121 Ferrara, Italy; (E.D.M.); (M.G.); (A.P.)
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2
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Borges R, Gu C, Machado JD, Ewing AG. The dynamic nature of exocytosis from large secretory vesicles. A view from electrochemistry and imaging. Cell Calcium 2023; 110:102699. [PMID: 36708611 DOI: 10.1016/j.ceca.2023.102699] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 01/16/2023] [Accepted: 01/19/2023] [Indexed: 01/22/2023]
Abstract
In this brief review, we discuss the factors that modulate the quantum size and the kinetics of exocytosis. We also discuss the determinants which motivate the type of exocytosis from the so-called kiss-and-run to full fusion and along the intermediate mode of partial release. Kiss-and-run release comprises the transient opening of a nanometer (approx. 2 nm diameter) fusion pore between vesicle and plasma membrane allowing a small amount of release. Partial release comprises a larger more extended opening of the pore to allow a larger fraction of released vesicle content and is what is observed as normal full release in most electrochemical measurements. Partial release appears to be dominant in dense core vesicles and perhaps synaptic vesicles. The concept of partial release leads to the fraction released as a plastic component of exocytosis. Partial vesicular distension and the kinetics of exocytosis can be modulated by second messengers, physiological modulators, and drugs. This concept adds a novel point of regulation for the exocytotic process.
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Affiliation(s)
- Ricardo Borges
- Pharmacology Unit, Medical School, Universidad de la Laguna, Tenerife. Spain
| | - Chaoyi Gu
- Department of Chemistry and Molecular Biology, University of Gothenburg, Sweden
| | - José-David Machado
- Pharmacology Unit, Medical School, Universidad de la Laguna, Tenerife. Spain
| | - Andrew G Ewing
- Department of Chemistry and Molecular Biology, University of Gothenburg, Sweden.
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3
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Vogl C, Neef J, Wichmann C. Methods for multiscale structural and functional analysis of the mammalian cochlea. Mol Cell Neurosci 2022; 120:103720. [DOI: 10.1016/j.mcn.2022.103720] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 02/13/2022] [Accepted: 03/08/2022] [Indexed: 01/11/2023] Open
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Won J, Pankratov Y, Jang MW, Kim S, Ju YH, Lee S, Lee SE, Kim A, Park S, Lee CJ, Heo WD. Opto-vTrap, an optogenetic trap for reversible inhibition of vesicular release, synaptic transmission, and behavior. Neuron 2021; 110:423-435.e4. [PMID: 34852235 DOI: 10.1016/j.neuron.2021.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 09/01/2021] [Accepted: 11/03/2021] [Indexed: 01/13/2023]
Abstract
Spatiotemporal control of brain activity by optogenetics has emerged as an essential tool to study brain function. For silencing brain activity, optogenetic probes, such as halorhodopsin and archaerhodopsin, inhibit transmitter release indirectly by hyperpolarizing membrane potentials. However, these probes cause an undesirable ionic imbalance and rebound spikes. Moreover, they are not applicable to use in non-excitable glial cells. Here we engineered Opto-vTrap, a light-inducible and reversible inhibition system to temporarily trap the transmitter-containing vesicles from exocytotic release. Light activation of Opto-vTrap caused full vesicle clusterization and complete inhibition of exocytosis within 1 min, which recovered within 30 min after light off. We found a significant reduction in synaptic and gliotransmission upon activation of Opto-vTrap in acute brain slices. Opto-vTrap significantly inhibited hippocampus-dependent memory retrieval with full recovery within an hour. We propose Opto-vTrap as a next-generation optogenetic silencer to control brain activity and behavior with minimal confounding effects.
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Affiliation(s)
- Joungha Won
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea; Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Yuriy Pankratov
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Minwoo Wendy Jang
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea; KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
| | - Sunpil Kim
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea; KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
| | - Yeon Ha Ju
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
| | - Sangkyu Lee
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
| | - Seung Eun Lee
- Virus Facility, Research Animal Resource Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea
| | - Arie Kim
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
| | - Soowon Park
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
| | - C Justin Lee
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea; KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea.
| | - Won Do Heo
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea; Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea; KAIST Institute for the BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
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5
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5 ns electric pulses induce Ca 2+-dependent exocytotic release of catecholamine from adrenal chromaffin cells. Bioelectrochemistry 2021; 140:107830. [PMID: 33965669 DOI: 10.1016/j.bioelechem.2021.107830] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Revised: 04/21/2021] [Accepted: 04/23/2021] [Indexed: 12/12/2022]
Abstract
Previously we reported that adrenal chromaffin cells exposed to a 5 ns, 5 MV/m pulse release the catecholamines norepinephrine (NE) and epinephrine (EPI) in a Ca2+-dependent manner. Here we determined that NE and EPI release increased with pulse number (one versus five and ten pulses at 1 Hz), established that release occurs by exocytosis, and characterized the exocytotic response in real-time. Evidence of an exocytotic mechanism was the appearance of dopamine-β-hydroxylase on the plasma membrane, and the demonstration by total internal reflection fluorescence microscopy studies that a train of five or ten pulses at 1 Hz triggered the release of the fluorescent dye acridine orange from secretory granules. Release events were Ca2+-dependent, longer-lived relative to those evoked by nicotinic receptor stimulation, and occurred with a delay of several seconds despite an immediate rise in Ca2+. In complementary studies, cells labeled with the plasma membrane fluorescent dye FM 1-43 and exposed to a train of ten pulses at 1 Hz underwent Ca2+-dependent increases in FM 1-43 fluorescence indicative of granule fusion with the plasma membrane due to exocytosis. These results demonstrate the effectiveness of ultrashort electric pulses for stimulating catecholamine release, signifying their promise as a novel electrostimulation modality for neurosecretion.
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6
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Guille-Collignon M, Lemaître F. Overview and outlook of the strategies devoted to electrofluorescence surveys: Application to single cell secretion analysis. Trends Analyt Chem 2020. [DOI: 10.1016/j.trac.2020.116055] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Klein O, Roded A, Hirschberg K, Fukuda M, Galli SJ, Sagi-Eisenberg R. Imaging FITC-dextran as a Reporter for Regulated Exocytosis. J Vis Exp 2018. [PMID: 29985342 DOI: 10.3791/57936] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Regulated exocytosis is a process by which cargo, which is stored in secretory granules (SGs), is released in response to a secretory trigger. Regulated exocytosis is fundamental for intercellular communication and is a key mechanism for the secretion of neurotransmitters, hormones, inflammatory mediators, and other compounds, by a variety of cells. At least three distinct mechanisms are known for regulated exocytosis: full exocytosis, where a single SG fully fuses with the plasma membrane, kiss-and-run exocytosis, where a single SG transiently fuses with the plasma membrane, and compound exocytosis, where several SGs fuse with each other, prior to or after SG fusion with the plasma membrane. The type of regulated exocytosis undertaken by a cell is often dictated by the type of secretory trigger. However, in many cells, a single secretory trigger can activate multiple modes of regulated exocytosis simultaneously. Despite their abundance and importance across cell types and species, the mechanisms that determine the different modes of secretion are largely unresolved. One of the main challenges in investigating the different modes of regulated exocytosis, is the difficulty in distinguishing between them as well as exploring them separately. Here we describe the use of fluorescein isothiocyanate (FITC)-dextran as an exocytosis reporter, and live cell imaging, to differentiate between the different pathways of regulated exocytosis, focusing on compound exocytosis, based on the robustness and duration of the exocytic events.
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Affiliation(s)
- Ofir Klein
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University
| | - Amit Roded
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University
| | - Koret Hirschberg
- Department of Pathology, Sackler Faculty of Medicine, Tel Aviv University
| | - Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University
| | - Stephen J Galli
- Departments of Pathology and of Microbiology and Immunology and Sean N. Parker Center for Allergy and Asthma Research, School of Medicine, Stanford University
| | - Ronit Sagi-Eisenberg
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University;
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8
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Verboogen DRJ, Ter Beest M, Honigmann A, van den Bogaart G. Secretory vesicles of immune cells contain only a limited number of interleukin 6 molecules. FEBS Lett 2018; 592:1535-1544. [PMID: 29570778 PMCID: PMC5969217 DOI: 10.1002/1873-3468.13036] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 02/12/2018] [Accepted: 03/13/2018] [Indexed: 01/06/2023]
Abstract
Immune cells communicate by releasing large quantities of cytokines. Although the mechanisms of cytokine secretion are increasingly understood, quantitative knowledge of the number of cytokines per vesicle is still lacking. Here, we measured with quantitative microscopy the release rate of vesicles potentially carrying interleukin‐6 (IL‐6) in human dendritic cells. By comparing this to the total secreted IL‐6, we estimate that secretory vesicles contain about 0.5–3 IL‐6 molecules, but with a large spread among cells/donors. Moreover, IL‐6 did not accumulate within most cells, indicating that synthesis and not trafficking is the bottleneck for IL‐6 production. IL‐6 accumulated in the Golgi apparatus only in ~ 10% of the cells. Understanding how immune cells produce cytokines is important for designing new immunomodulatory drugs.
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Affiliation(s)
- Daniëlle R J Verboogen
- Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Martin Ter Beest
- Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Alf Honigmann
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Geert van den Bogaart
- Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands.,Department of Molecular Immunology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, the Netherlands
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9
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Miller BA, Papke JB, Bindokas VP, Harkins AB. Light Activation of Calcein Inhibits Vesicle Release of Catecholamines. ACS Chem Neurosci 2017; 8:2309-2314. [PMID: 28707873 DOI: 10.1021/acschemneuro.7b00225] [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] [Indexed: 11/28/2022] Open
Abstract
Calcein, a fluorescent fluid phase marker, has been used to track and visualize cellular processes such as synaptic vesicle fusion. It is also the fluorophore for live cells in the commonly used Live/Dead viability assay. In pilot studies designed to determine fusion pore open size and vesicle movement in secretory cells, imaging analysis revealed that calcein reduced the number of vesicles released from the cells when stimulated with nicotine. Using amperometry to detect individual vesicle release events, we show that when calcein is present in the media, the number of vesicles that fuse with the cellular membrane is reduced when cells are stimulated with either nicotine or high K+. Experimentally, amperometric electrodes are not undergoing fouling in the presence of calcein. We hypothesized that calcein, when activated by light, releases reactive oxygen species that cause a reduction in secreted vesicles. We show that when calcein is protected from light during experimentation, little to no reduction of vesicle secretion occurred. Therefore, photoactivated calcein can cause deleterious results for measurements of cellular processes, likely to be the result of release of reactive oxygen species.
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Affiliation(s)
- Brooke A. Miller
- Department
of Pharmacology and Physiology, Saint Louis University, St. Louis, Missouri 63104, United States
| | - Jason B. Papke
- Department
of Pharmacology and Physiology, Saint Louis University, St. Louis, Missouri 63104, United States
| | - Vytas P. Bindokas
- Department
of Pharmacological and Physiological Sciences, University of Chicago, Chicago, Illinois 60637, United States
| | - Amy B. Harkins
- Department
of Pharmacology and Physiology, Saint Louis University, St. Louis, Missouri 63104, United States
- Department
of Biomedical Engineering, Saint Louis University, St. Louis, Missouri 63103, United States
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10
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High-resolution imaging of cellular dopamine efflux using a fluorescent nanosensor array. Proc Natl Acad Sci U S A 2017; 114:1789-1794. [PMID: 28179565 DOI: 10.1073/pnas.1613541114] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Intercellular communication via chemical signaling proceeds with both spatial and temporal components, but analytical tools, such as microfabricated electrodes, have been limited to just a few probes per cell. In this work, we use a nonphotobleaching fluorescent nanosensor array based on single-walled carbon nanotubes (SWCNTs) rendered selective to dopamine to study its release from PC12 neuroprogenitor cells at a resolution exceeding 20,000 sensors per cell. This allows the spatial and temporal dynamics of dopamine release, following K+ stimulation, to be measured at exceedingly high resolution. We observe localized, unlabeled release sites of dopamine spanning 100 ms to seconds that correlate with protrusions but not predominately the positive curvature associated with the tips of cellular protrusions as intuitively expected. The results illustrate how directionality of chemical signaling is shaped by membrane morphology, and highlight the advantages of nanosensor arrays that can provide high spatial and temporal resolution of chemical signaling.
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11
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Bost A, Shaib AH, Schwarz Y, Niemeyer BA, Becherer U. Large dense-core vesicle exocytosis from mouse dorsal root ganglion neurons is regulated by neuropeptide Y. Neuroscience 2017; 346:1-13. [PMID: 28089870 DOI: 10.1016/j.neuroscience.2017.01.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 01/03/2017] [Accepted: 01/04/2017] [Indexed: 12/12/2022]
Abstract
Peptidergic dorsal root ganglion (DRG) neurons transmit sensory and nociceptive information from the periphery to the central nervous system. Their synaptic activity is profoundly affected by neuromodulatory peptides stored and released from large dense-core vesicles (LDCVs). However, the mechanism of peptide secretion from DRG neurons is poorly understood. Using total internal reflection fluorescence microscopy (TIRFM), we visualized individual LDCVs loaded with fluorescent neuropeptide Y (NPY) and analyzed their stimulation-dependent release. We tested several protocols and found an overall low stimulation-secretion coupling that increased after raising intracellular Ca2+ concentration by applying a weak pre-stimulus. Interestingly, the stimulation protocol also influenced the mechanism of LDCV fusion. Depolarization of DRG neurons with a solution containing 60mM KCl triggered full fusion, kiss-and-run, and kiss-and-stay exocytosis with equal frequency. In contrast, field electrode stimulation primarily induced full fusion exocytosis. Finally, our results indicate that NPY can promote LDCV secretion. These results shed new light on the mechanism of NPY action during modulation of DRG neuron activity, an important pathway in the treatment of chronic pain.
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Affiliation(s)
- Anneka Bost
- Institute of Physiology, CIPMM, Saarland University, 66421 Homburg/Saar, Germany
| | - Ali H Shaib
- Institute of Physiology, CIPMM, Saarland University, 66421 Homburg/Saar, Germany
| | - Yvonne Schwarz
- Institute of Physiology, CIPMM, Saarland University, 66421 Homburg/Saar, Germany
| | - Barbara A Niemeyer
- Molecular Biophysics, CIPMM, Saarland University, 66421 Homburg/Saar, Germany
| | - Ute Becherer
- Institute of Physiology, CIPMM, Saarland University, 66421 Homburg/Saar, Germany.
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12
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Jarukanont D, Bonifas Arredondo I, Femat R, Garcia ME. Vesicle Motion during Sustained Exocytosis in Chromaffin Cells: Numerical Model Based on Amperometric Measurements. PLoS One 2015; 10:e0144045. [PMID: 26675312 PMCID: PMC4699451 DOI: 10.1371/journal.pone.0144045] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 11/12/2015] [Indexed: 01/26/2023] Open
Abstract
Chromaffin cells release catecholamines by exocytosis, a process that includes vesicle docking, priming and fusion. Although all these steps have been intensively studied, some aspects of their mechanisms, particularly those regarding vesicle transport to the active sites situated at the membrane, are still unclear. In this work, we show that it is possible to extract information on vesicle motion in Chromaffin cells from the combination of Langevin simulations and amperometric measurements. We developed a numerical model based on Langevin simulations of vesicle motion towards the cell membrane and on the statistical analysis of vesicle arrival times. We also performed amperometric experiments in bovine-adrenal Chromaffin cells under Ba2+ stimulation to capture neurotransmitter releases during sustained exocytosis. In the sustained phase, each amperometric peak can be related to a single release from a new vesicle arriving at the active site. The amperometric signal can then be mapped into a spike-series of release events. We normalized the spike-series resulting from the current peaks using a time-rescaling transformation, thus making signals coming from different cells comparable. We discuss why the obtained spike-series may contain information about the motion of all vesicles leading to release of catecholamines. We show that the release statistics in our experiments considerably deviate from Poisson processes. Moreover, the interspike-time probability is reasonably well described by two-parameter gamma distributions. In order to interpret this result we computed the vesicles’ arrival statistics from our Langevin simulations. As expected, assuming purely diffusive vesicle motion we obtain Poisson statistics. However, if we assume that all vesicles are guided toward the membrane by an attractive harmonic potential, simulations also lead to gamma distributions of the interspike-time probability, in remarkably good agreement with experiment. We also show that including the fusion-time statistics in our model does not produce any significant changes on the results. These findings indicate that the motion of the whole ensemble of vesicles towards the membrane is directed and reflected in the amperometric signals. Our results confirm the conclusions of previous imaging studies performed on single vesicles that vesicles’ motion underneath plasma membranes is not purely random, but biased towards the membrane.
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Affiliation(s)
- Daungruthai Jarukanont
- Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), Universität Kassel, Kassel, Germany
| | - Imelda Bonifas Arredondo
- División de Matemáticas Aplicadas, IPICYT, Camino a la Presa San José 2055, Lomas 4 Sección., San Luis Potosí, México
| | - Ricardo Femat
- División de Matemáticas Aplicadas, IPICYT, Camino a la Presa San José 2055, Lomas 4 Sección., San Luis Potosí, México
- * E-mail: (RF); (MEG)
| | - Martin E. Garcia
- Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), Universität Kassel, Kassel, Germany
- * E-mail: (RF); (MEG)
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Armstrong SM, Sugiyama MG, Fung KYY, Gao Y, Wang C, Levy AS, Azizi P, Roufaiel M, Zhu SN, Neculai D, Yin C, Bolz SS, Seidah NG, Cybulsky MI, Heit B, Lee WL. A novel assay uncovers an unexpected role for SR-BI in LDL transcytosis. Cardiovasc Res 2015; 108:268-77. [PMID: 26334034 DOI: 10.1093/cvr/cvv218] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 08/24/2015] [Indexed: 01/16/2023] Open
Abstract
AIMS Retention of low-density lipoprotein (LDL) cholesterol beneath the arterial endothelium initiates an inflammatory response culminating in atherosclerosis. Since the overlying endothelium is healthy and intact early on, it is likely that LDL passes through endothelial cells by transcytosis. However, technical challenges have made confirming this notion and elucidating the mechanisms of transcytosis difficult. We developed a novel assay for measuring LDL transcytosis in real time across coronary endothelial cell monolayers; we used this approach to identify the receptor involved. METHODS AND RESULTS Murine aortas were perfused ex vivo with LDL and dextran of a smaller molecular radius. LDL (but not dextran) accumulated under the endothelium, indicating that LDL transcytosis occurs in intact vessels. We then confirmed that LDL transcytosis occurs in vitro using human coronary artery endothelial cells. An assay was developed to quantify transcytosis of DiI-LDL in real time using total internal reflection fluorescence microscopy. DiI-LDL transcytosis was inhibited by excess unlabelled LDL, while degradation of the LDL receptor by PCSK9 had no effect. Instead, LDL colocalized partially with the scavenger receptor SR-BI and overexpression of SR-BI increased LDL transcytosis; knockdown by siRNA significantly reduced it. Excess HDL, the canonical SR-BI ligand, significantly decreased LDL transcytosis. Aortas from SR-BI-deficient mice were perfused ex vivo with LDL and accumulated significantly less sub-endothelial LDL compared with wild-type littermates. CONCLUSION We developed an assay to quantify LDL transcytosis across endothelial cells and discovered an unexpected role for SR-BI. Elucidating the mechanisms of LDL transcytosis may identify novel targets for the prevention or therapy of atherosclerosis.
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Affiliation(s)
- Susan M Armstrong
- Keenan Research Centre, St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8 Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada
| | - Michael G Sugiyama
- Keenan Research Centre, St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8 Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Karen Y Y Fung
- Keenan Research Centre, St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8
| | - Yizhuo Gao
- Keenan Research Centre, St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8
| | - Changsen Wang
- Keenan Research Centre, St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8
| | - Andrew S Levy
- Keenan Research Centre, St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8
| | - Paymon Azizi
- Keenan Research Centre, St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8
| | - Mark Roufaiel
- Toronto General Research Institute (TGRI), Toronto, Canada
| | - Su-Ning Zhu
- Toronto General Research Institute (TGRI), Toronto, Canada
| | | | - Charles Yin
- Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada
| | - Steffen-Sebastian Bolz
- Keenan Research Centre, St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8
| | | | - Myron I Cybulsky
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada Toronto General Research Institute (TGRI), Toronto, Canada
| | - Bryan Heit
- Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada
| | - Warren L Lee
- Keenan Research Centre, St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B 1W8 Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada Interdepartmental Division of Critical Care Medicine and the Department of Medicine, University of Toronto, Toronto, ON, Canada
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14
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Azizi PM, Zyla RE, Guan S, Wang C, Liu J, Bolz SS, Heit B, Klip A, Lee WL. Clathrin-dependent entry and vesicle-mediated exocytosis define insulin transcytosis across microvascular endothelial cells. Mol Biol Cell 2014; 26:740-50. [PMID: 25540431 PMCID: PMC4325843 DOI: 10.1091/mbc.e14-08-1307] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
How insulin traverses the continuous endothelium of the microvasculature has been poorly studied. Development of a novel assay to measure insulin transcytosis reveals an unexpected role for clathrin in insulin transendothelial transport. Insulin transcytosis is dynamin and clathrin dependent but does not require cholesterol or caveolin-1. Transport of insulin across the microvasculature is necessary to reach its target organs (e.g., adipose and muscle tissues) and is rate limiting in insulin action. Morphological evidence suggests that insulin enters endothelial cells of the microvasculature, and studies with large vessel–derived endothelial cells show insulin uptake; however, little is known about the actual transcytosis of insulin and how this occurs in the relevant microvascular endothelial cells. We report an approach to study insulin transcytosis across individual, primary human adipose microvascular endothelial cells (HAMECs), involving insulin uptake followed by vesicle-mediated exocytosis visualized by total internal reflection fluorescence microscopy. In this setting, fluorophore-conjugated insulin exocytosis depended on its initial binding and uptake, which was saturable and much greater than in muscle cells. Unlike its degradation within muscle cells, insulin was stable within HAMECs and escaped lysosomal colocalization. Insulin transcytosis required dynamin but was unaffected by caveolin-1 knockdown or cholesterol depletion. Instead, insulin transcytosis was significantly inhibited by the clathrin-mediated endocytosis inhibitor Pitstop 2 or siRNA-mediated clathrin depletion. Accordingly, insulin internalized for 1 min in HAMECs colocalized with clathrin far more than with caveolin-1. This study constitutes the first evidence of vesicle-mediated insulin transcytosis and highlights that its initial uptake is clathrin dependent and caveolae independent.
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Affiliation(s)
- Paymon M Azizi
- Institute of Medical Sciences, University of Toronto, Toronto, ON M5S 1A8, Canada Keenan Research Centre, St. Michael's Hospital, Toronto, ON M5B 1W8, Canada Programme in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Roman E Zyla
- Keenan Research Centre, St. Michael's Hospital, Toronto, ON M5B 1W8, Canada
| | - Sha Guan
- Institute of Medical Sciences, University of Toronto, Toronto, ON M5S 1A8, Canada Keenan Research Centre, St. Michael's Hospital, Toronto, ON M5B 1W8, Canada Programme in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Changsen Wang
- Keenan Research Centre, St. Michael's Hospital, Toronto, ON M5B 1W8, Canada
| | - Jun Liu
- Programme in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | | | - Bryan Heit
- Department of Microbiology and Immunology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Amira Klip
- Institute of Medical Sciences, University of Toronto, Toronto, ON M5S 1A8, Canada Programme in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Warren L Lee
- Institute of Medical Sciences, University of Toronto, Toronto, ON M5S 1A8, Canada Keenan Research Centre, St. Michael's Hospital, Toronto, ON M5B 1W8, Canada Department of Microbiology and Immunology, University of Western Ontario, London, ON N6A 5C1, Canada Interdepartmental Division of Critical Care, Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
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15
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Kurps J, Broeke JH, Cijsouw T, Kompatscher A, van Weering JRT, de Wit H. Quantitative image analysis tool to study the plasma membrane localization of proteins and cortical actin in neuroendocrine cells. J Neurosci Methods 2014; 236:1-10. [PMID: 25109903 DOI: 10.1016/j.jneumeth.2014.07.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 07/28/2014] [Accepted: 07/29/2014] [Indexed: 11/15/2022]
Abstract
BACKGROUND Adrenal chromaffin cells are a widely used model system to study regulated exocytosis and other membrane-associated processes. Alterations in the amount and localization of the proteins involved in these processes can be visualized with fluorescent probes that report the effect of different stimuli or genetic modifications. However, the quantitative analysis of such images remains difficult, especially when focused on specific locations, such as the plasma membrane. NEW METHOD We developed an image analysis algorithm, named plasma membrane analysis in chromaffin cells (PlasMACC). PlasMACC enables automatic detection of the plasma membrane region and quantitative analysis of multi-fluorescent signals from spherical cells. PlasMACC runs in the image analysis software ImageJ environment, it is user-friendly and freely available. RESULTS PlasMACC delivers detailed information about intensity, thickness and density of fluorescent signals at the plasma membrane of both living and fixed cells. Individual signals can be compared between cells and different signals within one cell can be correlated. PlasMACC can process conventional laser-scanning confocal images as well as data obtained by super-resolution methods such as structured illumination microscopy. COMPARISON WITH EXISTING METHOD(S) By comparing PlasMACC to methods currently used in the field, we show more consistent quantitative data due to the fully automated algorithm. PlasMACC also provides an expanded set of novel analysis parameters. CONCLUSION PlasMACC enables a detailed quantification of fluorescent signals at the plasma membrane of spherical cells in an unbiased and reliable fashion.
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Affiliation(s)
- Julia Kurps
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, Netherlands
| | - Jurjen H Broeke
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, Netherlands
| | - Tony Cijsouw
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, Netherlands
| | - Andreas Kompatscher
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, Netherlands
| | - Jan R T van Weering
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, Netherlands.
| | - Heidi de Wit
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, Netherlands
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16
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Matz M, Schumacher K, Hatlapatka K, Lorenz D, Baumann K, Rustenbeck I. Observer-independent quantification of insulin granule exocytosis and pre-exocytotic mobility by TIRF microscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2014; 20:206-218. [PMID: 24230985 DOI: 10.1017/s1431927613013767] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Total internal reflection fluorescence microscopy of fluorescently labeled secretory granules permits monitoring of exocytosis and the preceding granule behavior in one experiment. While observer-dependent evaluation may be sufficient to quantify exocytosis, most of the other information contained in the video files cannot be accessed this way. The present program performs observer-independent detection of exocytosis and tracking of the entire submembrane population of insulin granules. A precondition is the exact localization of the peak of the granule fluorescence. Tracking is based on the peak base radius, peak intensity, and the precrossing itineraries. Robustness of the tracking was shown by simulated tracks of original granule patterns. Mobility in the X-Y dimension is described by the caging diameter which in contrast to the widely used mean square displacement has an inherent time resolution. Observer-independent detection of exocytosis in MIN6 cells labeled with insulin-EGFP is based on the maximal decrease in fluorescence intensity and position of the centroid of the dissipating cloud of released material. Combining the quantification of KCl-induced insulin exocytosis with the analysis of prefusion mobility showed that during the last 3 s pre-exocytotic granules had a smaller caging diameter than control granules and that it increased significantly immediately before fusion.
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Affiliation(s)
- Magnus Matz
- Institute of Medicinal and Pharmaceutical Chemistry, University of Braunschweig, Braunschweig D38106, Germany
| | - Kirstin Schumacher
- Institute of Pharmacology and Toxicology, University of Braunschweig, Braunschweig D38106, Germany
| | - Kathrin Hatlapatka
- Institute of Pharmacology and Toxicology, University of Braunschweig, Braunschweig D38106, Germany
| | - Dirk Lorenz
- Institute of Analysis and Algebra, University of Braunschweig, Braunschweig D38106, Germany
| | - Knut Baumann
- Institute of Medicinal and Pharmaceutical Chemistry, University of Braunschweig, Braunschweig D38106, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology and Toxicology, University of Braunschweig, Braunschweig D38106, Germany
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17
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Abstract
Large dense core vesicle (LDCV) exocytosis in chromaffin cells follows a well characterized process consisting of docking, priming, and fusion. Total internal reflection fluorescence microscopy (TIRFM) studies suggest that some LDCVs, although being able to dock, are resistant to calcium-triggered release. This phenomenon termed dead-end docking has not been investigated until now. We characterized dead-end vesicles using a combination of membrane capacitance measurement and visualization of LDCVs with TIRFM. Stimulation of bovine chromaffin cells for 5 min with 6 μm free intracellular Ca2+ induced strong secretion and a large reduction of the LDCV density at the plasma membrane. Approximately 15% of the LDCVs were visible at the plasma membrane throughout experiments, indicating they were permanently docked dead-end vesicles. Overexpression of Munc18-2 or SNAP-25 reduced the fraction of dead-end vesicles. Conversely, expressing open-syntaxin increased the fraction of dead-end vesicles. These results indicate the existence of the unproductive target soluble N-ethylmaleimide-sensitive factor attachment protein receptor acceptor complex composed of 2:1 syntaxin-SNAP-25 in vivo. More importantly, they define a novel function for this acceptor complex in mediating dead-end docking.
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18
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Ges IA, Brindley RL, Currie KPM, Baudenbacher FJ. A microfluidic platform for chemical stimulation and real time analysis of catecholamine secretion from neuroendocrine cells. LAB ON A CHIP 2013; 13:4663-73. [PMID: 24126415 PMCID: PMC3892771 DOI: 10.1039/c3lc50779c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Release of neurotransmitters and hormones by calcium-regulated exocytosis is a fundamental cellular process that is disrupted in a variety of psychiatric, neurological, and endocrine disorders. As such, there is significant interest in targeting neurosecretion for drug and therapeutic development, efforts that will be aided by novel analytical tools and devices that provide mechanistic insight coupled with increased experimental throughput. Here, we report a simple, inexpensive, reusable, microfluidic device designed to analyze catecholamine secretion from small populations of adrenal chromaffin cells in real time, an important neuroendocrine component of the sympathetic nervous system and versatile neurosecretory model. The device is fabricated by replica molding of polydimethylsiloxane (PDMS) using patterned photoresist on silicon wafer as the master. Microfluidic inlet channels lead to an array of U-shaped "cell traps", each capable of immobilizing single or small groups of chromaffin cells. The bottom of the device is a glass slide with patterned thin film platinum electrodes used for electrochemical detection of catecholamines in real time. We demonstrate reliable loading of the device with small populations of chromaffin cells, and perfusion/repetitive stimulation with physiologically relevant secretagogues (carbachol, PACAP, KCl) using the microfluidic network. Evoked catecholamine secretion was reproducible over multiple rounds of stimulation, and graded as expected to different concentrations of secretagogue or removal of extracellular calcium. Overall, we show this microfluidic device can be used to implement complex stimulation paradigms and analyze the amount and kinetics of catecholamine secretion from small populations of neuroendocrine cells in real time.
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Affiliation(s)
- Igor A Ges
- Dept. of Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, Nashville, TN 37235-1631, USA.
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19
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Pattu V, Halimani M, Ming M, Schirra C, Hahn U, Bzeih H, Chang HF, Weins L, Krause E, Rettig J. In the crosshairs: investigating lytic granules by high-resolution microscopy and electrophysiology. Front Immunol 2013; 4:411. [PMID: 24348478 PMCID: PMC3841761 DOI: 10.3389/fimmu.2013.00411] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 11/11/2013] [Indexed: 12/17/2022] Open
Abstract
Cytotoxic T lymphocytes (CTLs) form an integral part of the adaptive immune system. Their main function is to eliminate bacteria- and virus-infected target cells by releasing perforin and granzymes (the lethal hit) contained within lytic granules (LGs), at the CTL-target-cell interface [the immunological synapse (IS)]. The formation of the IS as well as the final events at the IS leading to target-cell death are both highly complex and dynamic processes. In this review we highlight and discuss three high-resolution techniques that have proven invaluable in the effort to decipher key features of the mechanism of CTL effector function and in particular lytic granule maturation and fusion. Correlative light and electron microscopy allows the correlation between organelle morphology and localization of particular proteins, while total internal reflection fluorescence microscopy (TIRFM) enables the study of lytic granule dynamics at the IS in real time. The combination of TIRFM with patch-clamp membrane capacitance measurements finally provides a tool to quantify the size of fusing LGs at the IS.
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Affiliation(s)
- Varsha Pattu
- Institute of Physiology, Saarland University , Homburg, Saar , Germany
| | | | - Min Ming
- Institute of Physiology, Saarland University , Homburg, Saar , Germany
| | - Claudia Schirra
- Institute of Physiology, Saarland University , Homburg, Saar , Germany
| | - Ulrike Hahn
- Institute of Physiology, Saarland University , Homburg, Saar , Germany
| | - Hawraa Bzeih
- Institute of Physiology, Saarland University , Homburg, Saar , Germany
| | - Hsin-Fang Chang
- Institute of Physiology, Saarland University , Homburg, Saar , Germany
| | - Lisa Weins
- Institute of Physiology, Saarland University , Homburg, Saar , Germany
| | - Elmar Krause
- Institute of Physiology, Saarland University , Homburg, Saar , Germany
| | - Jens Rettig
- Institute of Physiology, Saarland University , Homburg, Saar , Germany
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20
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Kasai H, Takahashi N, Tokumaru H. Distinct Initial SNARE Configurations Underlying the Diversity of Exocytosis. Physiol Rev 2012; 92:1915-64. [DOI: 10.1152/physrev.00007.2012] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The dynamics of exocytosis are diverse and have been optimized for the functions of synapses and a wide variety of cell types. For example, the kinetics of exocytosis varies by more than five orders of magnitude between ultrafast exocytosis in synaptic vesicles and slow exocytosis in large dense-core vesicles. However, in all cases, exocytosis is mediated by the same fundamental mechanism, i.e., the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. It is often assumed that vesicles need to be docked at the plasma membrane and SNARE proteins must be preassembled before exocytosis is triggered. However, this model cannot account for the dynamics of exocytosis recently reported in synapses and other cells. For example, vesicles undergo exocytosis without prestimulus docking during tonic exocytosis of synaptic vesicles in the active zone. In addition, epithelial and hematopoietic cells utilize cAMP and kinases to trigger slow exocytosis of nondocked vesicles. In this review, we summarize the manner in which the diversity of exocytosis reflects the initial configurations of SNARE assembly, including trans-SNARE, binary-SNARE, unitary-SNARE, and cis-SNARE configurations. The initial SNARE configurations depend on the particular SNARE subtype (syntaxin, SNAP25, or VAMP), priming proteins (Munc18, Munc13, CAPS, complexin, or snapin), triggering proteins (synaptotagmins, Doc2, and various protein kinases), and the submembraneous cytomatrix, and they are the key to determining the kinetics of subsequent exocytosis. These distinct initial configurations will help us clarify the common SNARE assembly processes underlying exocytosis and membrane trafficking in eukaryotic cells.
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Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Hiroshi Tokumaru
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
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21
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Pasche M, Matti U, Hof D, Rettig J, Becherer U. Docking of LDCVs is modulated by lower intracellular [Ca2+] than priming. PLoS One 2012; 7:e36416. [PMID: 22590540 PMCID: PMC3349663 DOI: 10.1371/journal.pone.0036416] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 03/31/2012] [Indexed: 11/23/2022] Open
Abstract
Many regulatory steps precede final membrane fusion in neuroendocrine cells. Some parts of this preparatory cascade, including fusion and priming, are dependent on the intracellular Ca(2+) concentration ([Ca(2+)](i)). However, the functional implications of [Ca(2+)](i) in the regulation of docking remain elusive and controversial due to an inability to determine the modulatory effect of [Ca(2+)](i). Using a combination of TIRF-microscopy and electrophysiology we followed the movement of large dense core vesicles (LDCVs) close to the plasma membrane, simultaneously measuring membrane capacitance and [Ca(2+)](i). We found that a free [Ca(2+)](i) of 700 nM maximized the immediately releasable pool and minimized the lateral mobility of vesicles, which is consistent with a maximal increase of the pool size of primed LDCVs. The parameters that reflect docking, i.e. axial mobility and the fraction of LDCVs residing at the plasma membrane for less than 5 seconds, were strongly decreased at a free [Ca(2+)](i) of 500 nM. These results provide the first evidence that docking and priming occur at different free intracellular Ca(2+) concentrations, with docking efficiency being the most robust at 500 nM.
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Affiliation(s)
- Mathias Pasche
- Physiologisches Institut, Universität des Saarlandes, Homburg/Saar, Germany
| | - Ulf Matti
- Physiologisches Institut, Universität des Saarlandes, Homburg/Saar, Germany
| | - Detlef Hof
- Physiologisches Institut, Universität des Saarlandes, Homburg/Saar, Germany
| | - Jens Rettig
- Physiologisches Institut, Universität des Saarlandes, Homburg/Saar, Germany
| | - Ute Becherer
- Physiologisches Institut, Universität des Saarlandes, Homburg/Saar, Germany
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22
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Gutiérrez-Martín Y, Bustillo D, Gómez-Villafuertes R, Sánchez-Nogueiro J, Torregrosa-Hetland C, Binz T, Gutiérrez LM, Miras-Portugal MT, Artalejo AR. P2X7 receptors trigger ATP exocytosis and modify secretory vesicle dynamics in neuroblastoma cells. J Biol Chem 2011; 286:11370-81. [PMID: 21292765 PMCID: PMC3064193 DOI: 10.1074/jbc.m110.139410] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Previously, we reported that purinergic ionotropic P2X7 receptors negatively regulate neurite formation in Neuro-2a (N2a) mouse neuroblastoma cells through a Ca2+/calmodulin-dependent kinase II-related mechanism. In the present study we used this cell line to investigate a parallel though faster P2X7 receptor-mediated signaling pathway, namely Ca2+-regulated exocytosis. Selective activation of P2X7 receptors evoked exocytosis as assayed by high resolution membrane capacitance measurements. Using dual-wavelength total internal reflection microscopy, we have observed both the increase in near-membrane Ca2+ concentration and the exocytosis of fluorescently labeled vesicles in response to P2X7 receptor stimulation. Moreover, activation of P2X7 receptors also affects vesicle motion in the vertical and horizontal directions, thus, involving this receptor type in the control of early steps (docking and priming) of the secretory pathway. Immunocytochemical and RT-PCR experiments evidenced that N2a cells express the three neuronal SNAREs as well as vesicular nucleotide and monoamine (VMAT-1 and VMAT-2) transporters. Biochemical measurements indicated that ionomycin induced a significant release of ATP from N2a cells. Finally, P2X7 receptor stimulation and ionomycin increased the incidence of small transient inward currents, reminiscent of postsynaptic quantal events observed at synapses. Small transient inward currents were dependent on extracellular Ca2+ and were abolished by Brilliant Blue G, suggesting they were mediated by P2X7 receptors. Altogether, these results suggest the existence of a positive feedback mechanism mediated by P2X7 receptor-stimulated exocytotic release of ATP that would act on P2X7 receptors on the same or neighbor cells to further stimulate its own release and negatively control N2a cell differentiation.
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23
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Lam AD, Ismail S, Wu R, Yizhar O, Passmore DR, Ernst SA, Stuenkel EL. Mapping dynamic protein interactions to insulin secretory granule behavior with TIRF-FRET. Biophys J 2010; 99:1311-20. [PMID: 20713017 DOI: 10.1016/j.bpj.2010.06.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 05/26/2010] [Accepted: 06/04/2010] [Indexed: 10/19/2022] Open
Abstract
Biological processes are governed by extensive networks of dynamic molecular interactions. Yet, establishing a spatial and temporal map of these interactions and their direct relationship to specific cell functions has remained a challenge. Here, we implement sensitized emission Förster resonance energy transfer (FRET) stoichiometry under total internal reflection fluorescence (TIRF) microscopy. We demonstrate through quantitative analysis and modeling that evanescent fields must be precisely matched between FRET excitation wavelengths to isolate dynamic interactions between bimolecular FRET pairs that are not entirely membrane-delimited. We then use TIRF-FRET to monitor the behavior of individual insulin-containing secretory granules at the plasma membrane of living cells, while simultaneously tracking the dynamic interaction between the GTPase Rab27A and its effector Slp4A, on those same granules. Notably, insulin granules that underwent exocytosis demonstrated a specific increase in Rab27A-GTP/Slp4A FRET in the 5 s before membrane fusion, which coincided temporally with an increase in granule displacement and mobility. These results demonstrate an initial spatiotemporal mapping of a dynamic protein-protein interaction on individual secretory granules that is linked to a specific granule behavior in living cells.
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Affiliation(s)
- Alice D Lam
- Department of Molecular and Integrative Physiology and Neuroscience Program, University of Michigan, Ann Arbor, Michigan, USA
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24
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Müller O, Tian Q, Zantl R, Kahl V, Lipp P, Kaestner L. A system for optical high resolution screening of electrical excitable cells. Cell Calcium 2010; 47:224-33. [DOI: 10.1016/j.ceca.2009.11.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 10/15/2009] [Accepted: 11/27/2009] [Indexed: 11/28/2022]
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25
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Uchida M, Mouriño-Pérez RR, Roberson RW. Live-cell imaging of microtubule dynamics in hyphae of Neurospora crassa. Methods Mol Biol 2010; 638:259-268. [PMID: 20238275 DOI: 10.1007/978-1-60761-611-5_19] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Due to the large number of microtubules in the wild-type strain, total internal reflection fluorescence (TIRF) microscopy was used to study cortical microtubule dynamics in leading hyphae of Neurospora crassa expressing beta-tubulin-GFP. Detection of plus-end dynamics of individual microtubule was much improved with this approach compared to the other commonly used methods such as confocal and widefield fluorescence microscopy. In order to address the roles of motor proteins in microtubule dynamics, microtubule-motor mutant strains, deltankin and ro-1 were examined. Unlike the wild-type strain, there were fewer microtubules in these hyphal cells; therefore, imaging was done using widefield fluorescence microscopy. We have shown that polymerization and depolymerization rates as well as hyphal extension rates were reduced by one half relative to those of wild type. Therefore, we believe that the hyphal extension rates are dependent upon the dynamic characteristics of microtubules, which are then regulated by microtubule motors in N. crassa.
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Affiliation(s)
- Maho Uchida
- Department of Anatomy, University of California, San Francisco, CA, USA
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26
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Rickman C, Duncan RR. Munc18/Syntaxin interaction kinetics control secretory vesicle dynamics. J Biol Chem 2009; 285:3965-3972. [PMID: 19748891 PMCID: PMC2823538 DOI: 10.1074/jbc.m109.040402] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In neuronal and hormonal release, regulated exocytosis requires an essential set of proteins: the soluble N-ethylmaleimide sensitive-factor attachment receptor proteins (SNAREs) syntaxin 1, SNAP-25, VAMP, and their regulator, Munc18. Recently, it was found that Munc18-1 can interact with syntaxin 1 through distinct mechanisms: an inhibitory mode enveloping syntaxin (mode 1), sequestering it from SNARE protein interactions, and direct binding to an evolutionarily conserved N-terminal peptide of syntaxin (mode 2/3). The latter interaction has been proposed to control "priming" of the fusion reaction, defined using electrophysiology, but it is unknown how this interaction is regulated, and any dynamic effect at the molecular or vesicular level in cells remains undiscovered. We now show that a phosphorylation site in syntaxin 1 (Ser(14)) regulates the N-terminal interaction with Munc18-1. Probing syntaxin 1 association with Munc18-1, in real-time and in living cells, we found that modification of Ser(14) modulated the dynamics of this interaction, specifically at the plasma membrane. Destabilization of this dynamic interaction enhanced vesicle immobilization at the plasma membrane with a resulting inhibition of exocytosis.
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Affiliation(s)
- Colin Rickman
- From the Centre for Integrative Physiology, University of Edinburgh, George Square, Edinburgh EH8 9XD, Scotland, United Kingdom
| | - Rory R Duncan
- From the Centre for Integrative Physiology, University of Edinburgh, George Square, Edinburgh EH8 9XD, Scotland, United Kingdom.
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27
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Luccardini C, Yakovlev AV, Pasche M, Gaillard S, Li D, Rousseau F, Ly R, Becherer U, Mallet JM, Feltz A, Oheim M. Measuring mitochondrial and cytoplasmic Ca2+ in EGFP expressing cells with a low-affinity calcium Ruby and its dextran conjugate. Cell Calcium 2009; 45:275-83. [PMID: 19167753 DOI: 10.1016/j.ceca.2008.11.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 11/14/2008] [Accepted: 11/20/2008] [Indexed: 10/21/2022]
Abstract
The limited choice and poor performance of red-emitting calcium (Ca(2+)) indicators have hampered microfluorometric measurements of the intracellular free Ca(2+) concentration in cells expressing yellow- or green-fluorescent protein constructs. A long-wavelength Ca(2+) indicator would also permit a better discrimination against cellular autofluorescence than the commonly used fluorescein-based probes. Here, we report an improved synthesis and characterization of Calcium Ruby, a red-emitting probe consisting of an extended rhodamine chromophore (578/602 nm peak excitation/emission) conjugated to BAPTA and having an additional NH(2) linker arm. The low-affinity variant (K(D,Ca) approximately 30 microM) with a chloride in meta position that was specifically designed for the detection of large and rapid Ca(2+) transients. While Calcium Ruby is a mitochondrial Ca(2+)probe, its conjugation, via the NH(2) tail, to a 10,000 MW dextran abolishes the sub-cellular compartmentalization and generates a cytosolic Ca(2+) probe with an affinity matched to microdomain Ca(2+) signals. As an example, we show depolarization-evoked Ca(2+) signals triggering the exocytosis of individual chromaffin granules. Calcium Ruby should be of use in a wide range of applications involving dual- or triple labeling schemes or targeted sub-cellular Ca(2+) measurements.
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Quantal ATP release in rat beta-cells by exocytosis of insulin-containing LDCVs. Pflugers Arch 2008; 458:389-401. [PMID: 19018564 DOI: 10.1007/s00424-008-0610-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Accepted: 10/25/2008] [Indexed: 10/21/2022]
Abstract
Quantal release of adenosine triphosphate (ATP) was monitored in rat pancreatic beta-cells expressing P2X(2) receptors. Stimulation of exocytosis evoked rapidly activating and deactivating ATP-dependent transient inward currents (TICs). The unitary charge (q) of the events recorded at 0.2 microM [Ca(2+)](i) averaged 4.3 pC. The distribution of the 3 square root q of these events could be described by a single Gaussian. The rise times averaged approximately 5 ms over a wide range of TIC amplitudes. In beta-cells preloaded with 5-hydroxytryptamine (5-HT; accumulating in insulin granules), ATP was coreleased with 5-HT during >90% of the release events. Following step elevation of [Ca(2+)](i) to approximately 5 microM by photo release of caged Ca(2+), an increase in membrane capacitance was observed after 33 ms, whereas ATP release first became detectable after 43 ms. The step increase in [Ca(2+)](i) produced an initial large TIC followed by a series of smaller events that echoed the changes in membrane capacitance (DeltaC(m)). Mathematical modeling suggests that the large initial TIC reflects the superimposition of many unitary events. Exocytosis, measured as DeltaC(m) or TICs, was complete within 2 s after elevation of [Ca(2+)](i) with no sign of endocytosis masking the capacitance increase. The relationship between total charge (Q) and DeltaC(m) was linear with a slope of approximately 1.2 pC/fF. The latter value predicts a capacitance increase of 3.6 fF for the observed mean value of q, close to that expected for exocytosis of individual insulin granules. Our results indicate that measurements of ATP release and DeltaC(m) principally (> or =85-95%) report exocytosis of insulin granules.
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Ravier MA, Tsuboi T, Rutter GA. Imaging a target of Ca2+ signalling: dense core granule exocytosis viewed by total internal reflection fluorescence microscopy. Methods 2008; 46:233-8. [PMID: 18854212 PMCID: PMC2597054 DOI: 10.1016/j.ymeth.2008.09.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2008] [Accepted: 09/12/2008] [Indexed: 12/20/2022] Open
Abstract
Ca2+ ions are the most ubiquitous second messenger found in all cells, and play a significant role in controlling regulated secretion from neurons, endocrine, neuroendocrine and exocrine cells. Here, we describe microscopic techniques to image regulated secretion, a target of Ca2+ signalling. The first of these, total internal reflection fluorescence (TIRF), is well suited for optical sectioning at cell–substrate regions with an unusually thin region of fluorescence excitation (<150 nm). It is thus particularly useful for studies of regulated hormone secretion. A brief summary of this approach is provided, as well as a description of the physical basis for the technique and the tools to implement TIRF using a standard fluorescence microscope. We also detail the different fluorescent probes which can be used to detect secretion and how to analyze the data obtained. A comparison between TIRF and other imaging modalities including confocal and multiphoton microscopy is also included.
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Affiliation(s)
- Magalie A Ravier
- Unit of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, UCL 55.30 Avenue Hippocrate 55, B-1200 Brussels, Belgium
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Llobet A, Wu M, Lagnado L. The mouth of a dense-core vesicle opens and closes in a concerted action regulated by calcium and amphiphysin. ACTA ACUST UNITED AC 2008; 182:1017-28. [PMID: 18779374 PMCID: PMC2528570 DOI: 10.1083/jcb.200807034] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Secretion of hormones and peptides by neuroendocrine cells occurs through fast and slow modes of vesicle fusion but the mechanics of these processes are not understood. We used interference reflection microscopy to monitor deformations of the membrane surface and found that both modes of fusion involve the tightly coupled dilation and constriction of the vesicle. The rate of opening is calcium dependent and occurs rapidly at concentrations <5 muM [corrected] The fast mode of fusion is blocked selectively by a truncation mutant of amphiphysin. Vesicles do not collapse when fusion is triggered by strontium, rather they remain locked open and membrane scission is blocked. In contrast, constriction of the vesicle opening continues when endocytosis is blocked by inhibiting the function of dynamin. Thus, fast and slow modes of fusion involve similar membrane deformations and vesicle closure can be uncoupled from membrane scission. Regulation of these processes by calcium and amphiphysin may provide a mechanism for controlling the release of vesicle contents.
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Affiliation(s)
- Artur Llobet
- Medical Research Council Laboratory of Molecular Biology, Cambridge, England, UK.
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Yizhar O, Ashery U. Modulating vesicle priming reveals that vesicle immobilization is necessary but not sufficient for fusion-competence. PLoS One 2008; 3:e2694. [PMID: 18628949 PMCID: PMC2444019 DOI: 10.1371/journal.pone.0002694] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Accepted: 05/29/2008] [Indexed: 11/19/2022] Open
Abstract
In neurons and neuroendocrine cells, docked vesicles need to undergo priming to become fusion competent. Priming is a multi-step process that was shown to be associated with vesicle immobilization. However, it is not known whether vesicle immobilization is sufficient to acquire complete fusion competence. To extend our understanding of the physical manifestation of vesicle priming, we took advantage of tomosyn, a SNARE-related protein that specifically inhibits vesicle priming, and measured its effect on vesicle dynamics in live chromaffin cells using total internal reflection fluorescence microscopy. We show here that while in control cells vesicles undergo immobilization before fusion, vesicle immobilization is attenuated in tomosyn overexpressing cells. This in turn increases the turnover rate of vesicles near the membrane and attenuates the fusion of newcomer vesicles. Moreover, the release probability of immobile vesicles in tomosyn cells is significantly reduced, suggesting that immobilization is an early and necessary step in priming but is insufficient, as further molecular processes are needed to acquire complete fusion competence. Using tomosyn as a molecular tool we provide a mechanistic link between functional docking and priming and suggest that functional docking is the first step in vesicle priming, followed by molecular modifications that do not translate into changes in vesicle mobility.
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Affiliation(s)
- Ofer Yizhar
- Department of Neurobiology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Uri Ashery
- Department of Neurobiology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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TRPM7 facilitates cholinergic vesicle fusion with the plasma membrane. Proc Natl Acad Sci U S A 2008; 105:8304-8. [PMID: 18539771 DOI: 10.1073/pnas.0800881105] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
TRPM7, of the transient receptor potential (TRP) family, is both an ion channel and a kinase. Previously, we showed that TRPM7 is located in the membranes of acetylcholine (ACh)-secreting synaptic vesicles of sympathetic neurons, forms a molecular complex with proteins of the vesicular fusion machinery, and is critical for stimulated neurotransmitter release. Here, we targeted pHluorin to small synaptic-like vesicles (SSLV) in PC12 cells and demonstrate that it can serve as a single-vesicle plasma membrane fusion reporter. In PC12 cells, as in sympathetic neurons, TRPM7 is located in ACh-secreting SSLVs. TRPM7 knockdown by siRNA, or abolishing channel activity by expression of a dominant negative TRPM7 pore mutant, decreased the frequency of spontaneous and voltage-stimulated SSLV fusion events without affecting large dense core vesicle secretion. We conclude that the conductance of TRPM7 across the vesicle membrane is important in SSLV fusion.
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