1
|
Zhou Y, Nomigni MT, Gaigneaux A, Tolle F, Wright HL, Bueb JL, Bréchard S. miRNA-132-5p mediates a negative feedback regulation of IL-8 secretion through S100A8/A9 downregulation in neutrophil-like HL-60 cells. Front Immunol 2024; 14:1274378. [PMID: 38292491 PMCID: PMC10824955 DOI: 10.3389/fimmu.2023.1274378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 12/19/2023] [Indexed: 02/01/2024] Open
Abstract
Background Neutrophils are an important source of pro-inflammatory and immunomodulatory cytokines. This makes neutrophils efficient drivers of interactions with immune and non-immune cells to maintain homeostasis and modulate the inflammatory process by notably regulating the release of cytokines. Ca2+-dependent regulatory mechanism encompassing cytokine secretion by neutrophils are not still identified. In this context, we propose to define new insights on the role of Ca2+-binding proteins S100A8/A9 and on the regulatory role of miRNA-132-5p, which was identified as a regulator of S100A8/A9 expression, on IL-8 secretion. Methods Differentiated HL-60 cells, a human promyelocytic leukemia cell line that can be induced to differentiate into neutrophil-like cells, were used as a model of human neutrophils and treated with N- formyl-methionyl-leucyl-phenylalanine (fMLF), a bacterial peptide that activates neutrophils. shRNA knockdown was used to define the role of selected targets (S100A8/A9 and miRNA-132-5p) on IL-8 secretion. Results and discussion Different types of cytokines engage different signaling pathways in the secretion process. IL-8 release is tightly regulated by Ca2+ binding proteins S100A8/A9. miRNA-132-5p is up-regulated over time upon fMLF stimulation and decreases S100A8/A9 expression and IL-8 secretion. Conclusion These findings reveal a novel regulatory loop involving S100A8/A9 and miRNA-132-5p that modulates IL-8 secretion by neutrophils in inflammatory conditions. This loop could be a potential target for therapeutic intervention in inflammatory diseases.
Collapse
Affiliation(s)
- Yang Zhou
- Department of Life Sciences and Medicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Milène Tetsi Nomigni
- Department of Life Sciences and Medicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Anthoula Gaigneaux
- Department of Life Sciences and Medicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Fabrice Tolle
- Department of Life Sciences and Medicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Helen L. Wright
- Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Jean-Luc Bueb
- Department of Life Sciences and Medicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Sabrina Bréchard
- Department of Life Sciences and Medicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| |
Collapse
|
2
|
Hann J, Bueb JL, Tolle F, Bréchard S. Calcium signaling and regulation of neutrophil functions: Still a long way to go. J Leukoc Biol 2019; 107:285-297. [PMID: 31841231 DOI: 10.1002/jlb.3ru0719-241r] [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] [Received: 07/12/2019] [Revised: 11/08/2019] [Accepted: 12/01/2019] [Indexed: 12/22/2022] Open
Abstract
Neutrophils are the most abundant leukocytes in blood and disruption in their functions often results in an increased risk of serious infections and inflammatory autoimmune diseases. Following recent discoveries in their influence over disease progression, a resurgence of interest for neutrophil biology has taken place. The multitude of signaling pathways activated by the engagement of numerous types of receptors, with which neutrophils are endowed, reflects the functional complexity of these cells. It is therefore not surprising that there remains a huge lack in the understanding of molecular mechanisms underlining neutrophil functions. Moreover, studies on neutrophils are undoubtedly limited by the difficulty to efficiently edit the cell's genome. Over the past 30 years, compelling evidence has clearly highlighted that Ca2+ -signaling is governing the key processes associated with neutrophil functions. The confirmation of the role of an elevation of intracellular Ca2+ concentration has come from studies on NADPH oxidase activation and phagocytosis. In this review, we give an overview and update of our current knowledge on the role of Ca2+ mobilization in the regulation of pro-inflammatory functions of neutrophils. In particular, we stress the importance of Ca2+ in the formation of NETs and cytokine secretion in the light of newest findings. This will allow us to embrace how much further we have to go to understand the complex dynamics of Ca2+ -dependent mechanisms in order to gain more insights into the role of neutrophils in the pathogenesis of inflammatory diseases. The potential for therapeutics to regulate the neutrophil functions, such as Ca2+ influx inhibitors to prevent autoimmune and chronic inflammatory diseases, has been discussed in the last part of the review.
Collapse
Affiliation(s)
- J Hann
- Life Sciences Research Unit, Immune Cells and Inflammatory Diseases Group, University of Luxembourg, Belvaux, Luxembourg
| | - J-L Bueb
- Life Sciences Research Unit, Immune Cells and Inflammatory Diseases Group, University of Luxembourg, Belvaux, Luxembourg
| | - F Tolle
- Life Sciences Research Unit, Immune Cells and Inflammatory Diseases Group, University of Luxembourg, Belvaux, Luxembourg
| | - S Bréchard
- Life Sciences Research Unit, Immune Cells and Inflammatory Diseases Group, University of Luxembourg, Belvaux, Luxembourg
| |
Collapse
|
3
|
Henkel AW, Mouihate A, Welzel O. Differential Release of Exocytosis Marker Dyes Indicates Stimulation-Dependent Regulation of Synaptic Activity. Front Neurosci 2019; 13:1047. [PMID: 31632237 PMCID: PMC6783566 DOI: 10.3389/fnins.2019.01047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 09/18/2019] [Indexed: 02/05/2023] Open
Abstract
There is a general consensus that synaptic vesicular release by a full collapse process is the primary machinery of synaptic transmission. However, competing view suggests that synaptic vesicular release operates via a kiss-and-run mechanism. By monitoring the release dynamics of a synaptic vesicular marker, FM1-43 from individual synapses in hippocampal neurons, we found evidence that the release of synaptic vesicle was delayed by several seconds after the start of field stimulation. This phenomenon was associated with modified opening kinetics of fusion pores. Detailed analysis revealed that some synapses were completely inactive for a few seconds after stimulation, despite immediate calcium influx. This delay in vesicular release was modulated by various stimulation protocols and different frequencies, indicating an activity-dependent regulation mechanism for neurotransmitter exocytosis. Staurosporine, a drug known to induce “kiss-and-run” exocytosis, increased the proportion of delayed synapses as well as the delay duration, while fluoxetine acted contrarily. Besides being a serotonin reuptake inhibitor, it directly enhanced vesicle mobilization and reduced synaptic fatigue. Exocytosis was never delayed, when it was monitored with pH-sensitive probes, synaptopHlourin and αSyt-CypHerE5 antibody, indicating an instantaneous formation of a fusion pore that allowed rapid equilibration of vesicular lumenal pH but prevented FM1-43 release because of its slow dissociation from the inner vesicular membrane. Our observations suggest that synapses operate via a sequential “kiss-and-run” and “full-collapse” exocytosis mechanism. The initially narrow vesicular pore allows the equilibration of intravesicular pH which then progresses toward full fusion, causing FM1-43 release.
Collapse
Affiliation(s)
- Andreas W Henkel
- Department of Physiology, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait
| | - Abdeslam Mouihate
- Department of Physiology, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait
| | - Oliver Welzel
- Department of Psychiatry and Psychotherapy, University Hospital Erlangen, Erlangen, Germany
| |
Collapse
|
4
|
Abstract
Ca2+-dependent secretion is a process by which important signaling molecules that are produced within a cell-including proteins and neurotransmitters-are expelled to the extracellular environment. The cellular mechanism that underlies secretion is referred to as exocytosis. Many years of work have revealed that exocytosis in neurons and neuroendocrine cells is tightly coupled to Ca2+ and orchestrated by a series of protein-protein/protein-lipid interactions. Here, we highlight landmark discoveries that have informed our current understanding of the process. We focus principally on reductionist studies performed using powerful model secretory systems and cell-free reconstitution assays. In recent years, molecular cloning and genetics have implicated the involvement of a sizeable number of proteins in exocytosis. We expect reductionist approaches will be central to attempts to resolve their roles. The Journal of General Physiology will continue to be an outlet for much of this work, befitting its tradition of publishing strongly mechanistic, basic research.
Collapse
Affiliation(s)
- Arun Anantharam
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Alex J B Kreutzberger
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA
| |
Collapse
|
5
|
Haldar S, Mekhedov E, McCormick CD, Blank PS, Zimmerberg J. Lipid-dependence of target membrane stability during influenza viral fusion. J Cell Sci 2018; 132:jcs.218321. [PMID: 29967032 DOI: 10.1242/jcs.218321] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 06/21/2018] [Indexed: 12/11/2022] Open
Abstract
Although influenza kills about a half million people each year, even after excluding pandemics, there is only one set of antiviral drugs: neuraminidase inhibitors. By using a new approach utilizing giant unilamellar vesicles and infectious X-31 influenza virus, and testing for the newly identified pore intermediate of membrane fusion, we observed ∼30-87% poration, depending upon lipid composition. Testing the hypothesis that spontaneous curvature (SC) of the lipid monolayer controls membrane poration, our Poisson model and Boltzmann energetic considerations suggest a transition from a leaky to a non-leaky fusion pathway depending on the SC of the target membrane. When the target membrane SC is below approximately -0.20 nm-1 fusion between influenza virus and target membrane is predominantly non-leaky while above that fusion is predominantly leaky, suggesting that influenza hemagglutinin (HA)-catalyzed topological conversion of target membranes during fusion is associated with a loss of membrane integrity.
Collapse
Affiliation(s)
- Sourav Haldar
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Elena Mekhedov
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Chad D McCormick
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Paul S Blank
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Joshua Zimmerberg
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| |
Collapse
|
6
|
Barroso-Flores J, Herrera-Valdez MA, Galarraga E, Bargas J. Models of Short-Term Synaptic Plasticity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1015:41-57. [PMID: 29080020 DOI: 10.1007/978-3-319-62817-2_3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We focus on dynamical descriptions of short-term synaptic plasticity. Instead of focusing on the molecular machinery that has been reviewed recently by several authors, we concentrate on the dynamics and functional significance of synaptic plasticity, and review some mathematical models that reproduce different properties of the dynamics of short term synaptic plasticity that have been observed experimentally. The complexity and shortcomings of these models point to the need of simple, yet physiologically meaningful models. We propose a simplified model to be tested in synapses displaying different types of short-term plasticity.
Collapse
Affiliation(s)
- Janet Barroso-Flores
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, DF, 04510, Mexico.
| | - Marco A Herrera-Valdez
- Departamento de Matemáticas, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, DF, 04510, Mexico.
| | - Elvira Galarraga
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, DF, 04510, Mexico
| | - José Bargas
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, DF, 04510, Mexico
| |
Collapse
|
7
|
Liu J, Hussey PJ. Dissecting the regulation of pollen tube growth by modeling the interplay of hydrodynamics, cell wall and ion dynamics. FRONTIERS IN PLANT SCIENCE 2014; 5:392. [PMID: 25157262 PMCID: PMC4127481 DOI: 10.3389/fpls.2014.00392] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 07/22/2014] [Indexed: 05/30/2023]
Abstract
Hydrodynamics, cell wall and ion dynamics are all important properties that regulate pollen tube growth. Currently, the two main pollen tube growth models, the cell wall model and the hydrodynamic model do not appear to be reconcilable. Here we develop an integrative model for pollen tube growth and show that our model reproduces key experimental observations: (1) that the hypertonic condition leads to a much longer oscillatory period and that the hypotonic condition halves the oscillatory period; (2) that oscillations in turgor are experimentally undetectable; (3) that increasing the extracellular calcium concentration or decreasing the pH decreases the growth oscillatory amplitude; (4) that knockout of Raba4d, a member of the Rab family of small GTPase proteins, decreases pollen tube length after germination for 24 h. Using the model generated here, we reveal that (1) when cell wall extensibility is large, pollen tube may sustain growth at different volume changes and maintain relatively stable turgor; (2) turgor increases if cell wall extensibility decreases; (3) increasing turgor due to decrease in osmolarity in the media, although very small, increases volume change. However, increasing turgor due to decrease in cell wall extensibility decreases volume change. In this way regulation of pollen tube growth by turgor is context dependent. By changing the osmolarity in the media, the main regulatory points are extracellular osmolarity for water flow and turgor for the volume encompassed by the cell wall. However, if the viscosity of cell wall changes, the main regulatory points are turgor for water flow and wall extensibility for the volume encompassed by the cell wall. The novel methodology developed here reveals the underlying context-dependent regulatory principle of pollen tube growth.
Collapse
Affiliation(s)
- Junli Liu
- School of Biological and Biomedical Sciences, Durham UniversityDurham, UK
| | - Patrick J. Hussey
- School of Biological and Biomedical Sciences, Durham UniversityDurham, UK
| |
Collapse
|
8
|
Mooney J, Thakur S, Kahng P, Trapani JG, Poccia D. Quantification of exocytosis kinetics by DIC image analysis of cortical lawns. J Chem Biol 2014; 7:43-55. [PMID: 24711858 DOI: 10.1007/s12154-013-0104-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 09/01/2013] [Indexed: 12/13/2022] Open
Abstract
Cortical lawns prepared from sea urchin eggs have offered a robust in vitro system for study of regulated exocytosis and membrane fusion events since their introduction by Vacquier almost 40 years ago (Vacquier in Dev Biol 43:62-74, 1975). Lawns have been imaged by phase contrast, darkfield, differential interference contrast, and electron microscopy. Quantification of exocytosis kinetics has been achieved primarily by light scattering assays. We present simple differential interference contrast image analysis procedures for quantifying the kinetics and extent of exocytosis in cortical lawns using an open vessel that allows rapid solvent equilibration and modification. These preparations maintain the architecture of the original cortices, allow for cytological and immunocytochemical analyses, and permit quantification of variation within and between lawns. When combined, these methods can shed light on factors controlling the rate of secretion in a spatially relevant cellular context. We additionally provide a subroutine for IGOR Pro® that converts raw data from line scans of cortical lawns into kinetic profiles of exocytosis. Rapid image acquisition reveals spatial variations in time of initiation of individual granule fusion events with the plasma membrane not previously reported.
Collapse
Affiliation(s)
- James Mooney
- Program in Neuroscience, Amherst College, Amherst, MA 01002 USA
| | - Saumitra Thakur
- Program in Neuroscience, Amherst College, Amherst, MA 01002 USA
| | - Peter Kahng
- Department of Biology, Amherst College, Amherst, MA 01002 USA
| | - Josef G Trapani
- Department of Biology, Amherst College, Amherst, MA 01002 USA ; Program in Neuroscience, Amherst College, Amherst, MA 01002 USA
| | - Dominic Poccia
- Department of Biology, Amherst College, Amherst, MA 01002 USA ; Program in Neuroscience, Amherst College, Amherst, MA 01002 USA
| |
Collapse
|
9
|
Abbineni PS, Hibbert JE, Coorssen JR. Critical role of cortical vesicles in dissecting regulated exocytosis: overview of insights into fundamental molecular mechanisms. THE BIOLOGICAL BULLETIN 2013; 224:200-217. [PMID: 23995744 DOI: 10.1086/bblv224n3p200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Regulated exocytosis is one of the defining features of eukaryotic cells, underlying many conserved and essential functions. Definitively assigning specific roles to proteins and lipids in this fundamental mechanism is most effectively accomplished using a model system in which distinct stages of exocytosis can be effectively separated. Here we discuss the establishment of sea urchin cortical vesicle fusion as a model to study regulated exocytosis-a system in which the docked, release-ready, and late Ca(2+)-triggered steps of exocytosis are isolated and can be quantitatively assessed using the rigorous coupling of functional and molecular assays. We provide an overview of the insights this has provided into conserved molecular mechanisms and how these have led to and integrate with findings from other regulated exocytotic cells.
Collapse
Affiliation(s)
- Prabhodh S Abbineni
- Department of Molecular Physiology, School of Medicine, University of Western Sydney, NSW, Australia
| | | | | |
Collapse
|
10
|
Coorssen JR, Zorec R. Regulated exocytosis per partes. Cell Calcium 2012; 52:191-5. [PMID: 22784668 DOI: 10.1016/j.ceca.2012.06.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Revised: 06/13/2012] [Accepted: 06/13/2012] [Indexed: 12/13/2022]
Abstract
This Special Issue (SI) of Cell Calcium focuses on regulated exocytosis, a recent evolutionary invention of eukaryotic cells. This essential cellular process consists of several stages: (i) the delivery of membrane bound vesicles to specific plasma membrane sites, (ii) where the merger between the vesicle and the plasma membranes occurs, (iii) leading to the formation of an aqueous channel through which vesicle content starts to be discharged to the cell exterior, (iv) after the full incorporation of the vesicle membrane into the plasma membrane, the added vesicle membrane is retrieved back into the cytoplasm by endocytosis. (v) When a fusion pore opens it may close again, a process known as transient fusion pore opening (also kiss-and-run exocytosis). In some cell types these stages are extremely shortlived, as in some neurons, and thus relatively inaccessible to experimentation. In other cell types the transition between these stages is orders of magnitude slower and can be studied in more detail. However, despite the intense investigations of this critical biological process over the last decades, the molecular mechanisms underlying regulated exocytosis have yet to be fully resolved. We thus still lack a comprehensive physiological insight into the nature of the progressive and coupled stages of exocytosis. Such a molecular-level understanding would help to fully reconstruct this process in vitro, as well as identify potential therapeutic targets for a range of diseases and dysfunctions. There are 18 papers in this SI which have been organized into three sections: Rapid regulated exocytosis and calcium homeostasis with an introduction by Erwin Neher, Molecular mechanisms of regulated exocytosis, and Cell models for regulated exocytosis. Here we briefly outline and integrate the messages of these sections.
Collapse
|
11
|
Cohen R, Corwith K, Holowka D, Baird B. Spatiotemporal resolution of mast cell granule exocytosis reveals correlation with Ca2+ wave initiation. J Cell Sci 2012; 125:2986-94. [PMID: 22393234 DOI: 10.1242/jcs.102632] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mast cell activation initiated by antigen-mediated crosslinking of IgE receptors results in stimulated exocytosis of secretory lysosomes in the process known as degranulation. Much has been learned about the molecular mechanisms important for this process, including the crucial role of Ca(2+) mobilization, but spatio-temporal relationships between stimulated Ca(2+) mobilization and granule exocytosis are incompletely understood. Here we use a novel imaging-based method that uses fluorescein isothiocyanate (FITC)-dextran as a reporter for granule exocytosis in RBL mast cells and takes advantage of the pH sensitivity of FITC. We demonstrate the selectivity of FITC-dextran, accumulated by fluid-phase uptake, as a marker for secretory lysosomes, and we characterize its capacity to delineate different exocytotic events, including full fusion, kiss-and-run transient fusion and compound exocytosis. Using this method, we find strong dependence of degranulation kinetics on the duration of cell to substrate attachment. We combine imaging of degranulation and Ca(2+) dynamics to demonstrate a spatial relationship between the sites of Ca(2+) wave initiation in extended cell protrusions and exocytosis under conditions of limited antigen stimulation. In addition, we find that the spatially proximal Ca(2+) signaling and secretory events correlate with participation of TRPC1 channels in Ca(2+) mobilization.
Collapse
Affiliation(s)
- Roy Cohen
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA
| | | | | | | |
Collapse
|
12
|
Kroeger JH, Zerzour R, Geitmann A. Regulator or driving force? The role of turgor pressure in oscillatory plant cell growth. PLoS One 2011; 6:e18549. [PMID: 21541026 PMCID: PMC3081820 DOI: 10.1371/journal.pone.0018549] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Accepted: 03/03/2011] [Indexed: 11/25/2022] Open
Abstract
Turgor generates the stress that leads to the expansion of plant cell walls during cellular growth. This has been formalized by the Lockhart equation, which can be derived from the physical laws of the deformation of viscoelastic materials. However, the experimental evidence for such a direct correlation between growth rate and turgor is inconclusive. This has led to challenges of the Lockhart model. We model the oscillatory growth of pollen tubes to investigate this relationship. We couple the Lockhart equation to the dynamical equations for the change in material properties. We find that the correct implementation of the Lockhart equation within a feedback loop leading to low amplitude oscillatory growth predicts that in this system changes in the global turgor do not influence the average growth rate in a linear manner, consistent with experimental observations. An analytic analysis of our model demonstrates in which regime the average growth rate becomes uncorrelated from the turgor pressure.
Collapse
Affiliation(s)
- Jens H. Kroeger
- Department of Physiology, Centre for Nonlinear Dynamics, McGill University, Montréal, Québec, Canada
| | - Rabah Zerzour
- Département de Sciences Biologiques, Institut de Recherche en Biologie Végétale, Université de Montréal, Montréal, Québec, Canada
| | - Anja Geitmann
- Département de Sciences Biologiques, Institut de Recherche en Biologie Végétale, Université de Montréal, Montréal, Québec, Canada
| |
Collapse
|
13
|
Brunner Y, Schvartz D, Couté Y, Sanchez JC. Proteomics of regulated secretory organelles. MASS SPECTROMETRY REVIEWS 2009; 28:844-867. [PMID: 19301366 DOI: 10.1002/mas.20211] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Regulated secretory organelles are important subcellular structures of living cells that allow the release in the extracellular space of crucial compounds, such as hormones and neurotransmitters. Therefore, the regulation of biogenesis, trafficking, and exocytosis of regulated secretory organelles has been intensively studied during the last 30 years. However, due to the large number of different regulated secretory organelles, only a few of them have been specifically characterized. New insights into regulated secretory organelles open crucial perspectives for a better comprehension of the mechanisms that govern cell secretion. The combination of subcellular fractionation, protein separation, and mass spectrometry is also possible to study regulated secretory organelles at the proteome level. In this review, we present different strategies used to isolate regulated secretory organelles, separate their protein content, and identify the proteins by mass spectrometry. The biological significance of regulated secretory organelles-proteomic analysis is discussed as well.
Collapse
Affiliation(s)
- Yannick Brunner
- Biomedical Proteomics Research Group, University Medical Center, Geneva, Switzerland
| | | | | | | |
Collapse
|
14
|
Furber KL, Dean KT, Coorssen JR. Dissecting the mechanism of Ca2+-triggered membrane fusion: probing protein function using thiol reactivity. Clin Exp Pharmacol Physiol 2009; 37:208-17. [PMID: 19671061 DOI: 10.1111/j.1440-1681.2009.05278.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
1. Ca(2+)-triggered membrane fusion involves the coordinated actions of both lipids and proteins, but the specific mechanisms remain poorly understood. The urchin cortical vesicle model is a stage-specific native preparation fully enabling the directly coupled functional-molecular analyses necessary to identify critical components of fast triggered membrane fusion. 2. Recent work on lipidic components has established a direct role for cholesterol in the fusion mechanism via local contribution of negative curvature to readily enable the formation of transient lipidic fusion intermediates. In addition, cholesterol- and sphingomyelin-enriched domains regulate the efficiency of fusion by focally organizing other components to ensure an optimized response to the triggering Ca(2+) transient. 3. There is less known about the identity of proteins involved in the Ca(2+)-triggering steps of membrane fusion. Thiol reagents can be used as unbiased tools to probe protein functions. Comparisons of several thiol-reactive reagents have identified different effects on Ca(2+) sensitivity and the extent of fusion, suggesting that there are at least two distinct thiol sites that participate in the fusion mechanism: one that regulates the efficiency of Ca(2+) sensing/triggering and one that may function during the membrane merger event itself. 4. To identify the proteins that regulate Ca(2+) sensitivity, the fluorescent thiol reagent Lucifer yellow iodoacetamide was used to potentiate fusion and simultaneously tag the proteins involved. Ongoing work involves the isolation of cholesterol-enriched membrane fractions to reduce the complexity of the labelled proteome, narrowing the number of candidate proteins.
Collapse
Affiliation(s)
- Kendra L Furber
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
| | | | | |
Collapse
|
15
|
Kroeger JH, Geitmann A, Grant M. Model for calcium dependent oscillatory growth in pollen tubes. J Theor Biol 2008; 253:363-74. [PMID: 18471831 DOI: 10.1016/j.jtbi.2008.02.042] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2007] [Revised: 02/25/2008] [Accepted: 02/27/2008] [Indexed: 01/28/2023]
Abstract
Experiments have shown that pollen tubes grow in an oscillatory mode, the mechanism of which is poorly understood. We propose a theoretical growth model of pollen tubes exhibiting such oscillatory behaviour. The pollen tube and the surrounding medium are represented by two immiscible fluids separated by an interface. The physical variables are pressure, surface tension, density and viscosity, which depend on relevant biological quantities, namely calcium concentration and thickness of the cell wall. The essential features generally believed to control oscillating growth are included in the model, namely a turgor pressure, a viscous cell wall which yields under pressure, stretch-activated calcium channels which transport calcium ions into the cytoplasm and an exocytosis rate dependent on the cytosolic calcium concentration in the apex of the cell. We find that a calcium dependent vesicle recycling mechanism is necessary to obtain an oscillating growth rate in our model. We study the variation in the frequency of the growth rate by changing the extracellular calcium concentration and the density of ion channels in the membrane. We compare the predictions of our model with experimental data on the frequency of oscillation versus growth speed, calcium concentration and density of calcium channels.
Collapse
Affiliation(s)
- Jens H Kroeger
- Ernest Rutherford Physics Building, McGill University, 3600 Rue University, Montréal, Québec H3A2T8, Canada.
| | | | | |
Collapse
|
16
|
Specific lipids supply critical negative spontaneous curvature--an essential component of native Ca2+-triggered membrane fusion. Biophys J 2008; 94:3976-86. [PMID: 18227127 DOI: 10.1529/biophysj.107.123984] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Ca(2+)-triggered merger of two apposed membranes is the defining step of regulated exocytosis. CHOL is required at critical levels in secretory vesicle membranes to enable efficient, native membrane fusion: CHOL-sphingomyelin enriched microdomains organize the site and regulate fusion efficiency, and CHOL directly supports the capacity for membrane merger by virtue of its negative spontaneous curvature. Specific, structurally dissimilar lipids substitute for CHOL in supporting the ability of vesicles to fuse: diacylglycerol, alphaT, and phosphatidylethanolamine support triggered fusion in CHOL-depleted vesicles, and this correlates quantitatively with the amount of curvature each imparts to the membrane. Lipids of lesser negative curvature than cholesterol do not support fusion. The fundamental mechanism of regulated bilayer merger requires not only a defined amount of membrane-negative curvature, but this curvature must be provided by molecules having a specific, critical spontaneous curvature. Such a local lipid composition is energetically favorable, ensuring the necessary "spontaneous" lipid rearrangements that must occur during native membrane fusion-Ca(2+)-triggered fusion pore formation and expansion. Thus, different fusion sites or vesicle types can use specific alternate lipidic components, or combinations thereof, to facilitate and modulate the fusion pore.
Collapse
|
17
|
Hibbert JE, Butt RH, Coorssen JR. Actin is not an essential component in the mechanism of calcium-triggered vesicle fusion. Int J Biochem Cell Biol 2005; 38:461-71. [PMID: 16309945 DOI: 10.1016/j.biocel.2005.10.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2005] [Accepted: 10/17/2005] [Indexed: 10/25/2022]
Abstract
Actin has been suggested as an essential component in the membrane fusion stage of exocytosis. In some model systems disruption of the actin filament network associated with exocytotic membranes results in a decrease in secretion. Here we analyze the fast Ca2+-triggered membrane fusion steps of regulated exocytosis using a stage-specific preparation of native secretory vesicles (SV) to directly test whether actin plays an essential role in this mechanism. Although present on secretory vesicles, selective pharmacological inhibition of actin did not affect the Ca2+-sensitivity, extent, or kinetics of membrane fusion, nor did the addition of exogenous actin or an anti-actin antibody. There was also no discernable affect on inter-vesicle contact (docking). Overall, the results do not support a direct role for actin in the fast, Ca2+-triggered steps of regulated membrane fusion. It would appear that actin acts elsewhere within the exocytotic cycle.
Collapse
Affiliation(s)
- Julie E Hibbert
- Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, Calgary, Alta., Canada T2N 4N1
| | | | | |
Collapse
|
18
|
Churchward MA, Rogasevskaia T, Höfgen J, Bau J, Coorssen JR. Cholesterol facilitates the native mechanism of Ca2+-triggered membrane fusion. J Cell Sci 2005; 118:4833-48. [PMID: 16219690 DOI: 10.1242/jcs.02601] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The process of regulated exocytosis is defined by the Ca2+-triggered fusion of two apposed membranes, enabling the release of vesicular contents. This fusion step involves a number of energetically complex steps and requires both protein and lipid membrane components. The role of cholesterol has been investigated using isolated release-ready native cortical secretory vesicles to analyze the Ca2+-triggered fusion step of exocytosis. Cholesterol is a major component of vesicle membranes and we show here that selective removal from membranes, selective sequestering within membranes, or enzymatic modification causes a significant inhibition of the extent, Ca2+ sensitivity and kinetics of fusion. Depending upon the amount incorporated, addition of exogenous cholesterol to cholesterol-depleted membranes consistently recovers the extent, but not the Ca2+ sensitivity or kinetics of fusion. Membrane components of comparable negative curvature selectively recover the ability to fuse, but are unable to recover the kinetics and Ca2+ sensitivity of vesicle fusion. This indicates at least two specific positive roles for cholesterol in the process of membrane fusion: as a local membrane organizer contributing to the efficiency of fusion, and, by virtue of its intrinsic negative curvature, as a specific molecule working in concert with protein factors to facilitate the minimal molecular machinery for fast Ca2+-triggered fusion.
Collapse
Affiliation(s)
- Matthew A Churchward
- Department of Physiology and Biophysics, Hotchkiss Brain Institute, University of Calgary, Health Sciences Centre, Faculty of Medicine, Calgary, Alberta, T2N 4N1, Canada
| | | | | | | | | |
Collapse
|
19
|
Rickman C, Craxton M, Osborne S, Davletov B. Comparative analysis of tandem C2 domains from the mammalian synaptotagmin family. Biochem J 2004; 378:681-6. [PMID: 14713287 PMCID: PMC1223993 DOI: 10.1042/bj20031407] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2003] [Revised: 10/30/2003] [Accepted: 11/12/2003] [Indexed: 11/17/2022]
Abstract
Intracellular membrane traffic is governed by a conserved set of proteins, including Syts (synaptotagmins). The mammalian Syt family includes 15 isoforms. Syts are membrane proteins that possess tandem C2 domains (C2AB) implicated in calcium-dependent phospholipid binding. We performed a pair-wise amino acid sequence comparison, together with functional studies of rat Syt C2ABs, to examine common and divergent properties within the mammalian family. Sequence analysis indicates three different C2AB classes, the members of which share a high degree of sequence similarity. All the other C2ABs are highly divergent in sequence. Nearly half of the Syt family does not exhibit calcium/phospholipid binding in comparison to Syt I, the major brain isoform. Syts do, however, possess a more conserved function, namely calcium-independent binding to target SNARE (soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor) heterodimers. All tested isoforms, except Syt XII and Syt XIII, bound the target SNARE heterodimer comprising syntaxin 1 and SNAP-25 (25 kDa synaptosome-associated protein). Our present study suggests that many Syt isoforms can function in membrane trafficking to interact with the target SNARE heterodimer on the pathway to calcium-triggered membrane fusion.
Collapse
Affiliation(s)
- Colin Rickman
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
| | | | | | | |
Collapse
|
20
|
Mittal A, Leikina E, Chernomordik LV, Bentz J. Kinetically differentiating influenza hemagglutinin fusion and hemifusion machines. Biophys J 2003; 85:1713-24. [PMID: 12944286 PMCID: PMC1303345 DOI: 10.1016/s0006-3495(03)74601-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Membrane fusion mediated by influenza virus hemagglutinin (HA) yields different phenotypes depending on the surface density of activated HAs. A key question is whether different phenotypes arise from different fusion machines or whether different numbers of identical fusion machines yield different probabilistic outcomes. If fusion were simply a less probable event than hemifusion, requiring a larger number of identical fusion machines to occur first, then two predictions can be made. First, fusion should have a shorter average delay time than hemifusion, since there are more machines. Second, fusion should have a longer execution time of lipid mixing after it begins than hemifusion, since the full event cannot be faster than the partial event. Using a new automated video microscopy technique, we simultaneously monitored many HA-expressing cells fusing with erythrocytes and identified individual cell pairs with either full or only partial redistribution of fluorescent lipids. The full lipid mixing phenotype also showed contents mixing, i.e., fusion. Kinetic screening of the digitized fluorescence data showed that the execution of lipid mixing after the onset is faster for fusion than hemifusion. We found no correlation between the delay times before the onset of lipid mixing and the final fusion phenotype. We also found that the execution time for fusion was faster than that for hemifusion. Thus, we provide the first experimental evidence for fusion and hemifusion arising from different machines.
Collapse
Affiliation(s)
- Aditya Mittal
- Department of Bioscience and Biotechnology, Drexel University, Philadelphia, Pennsylvania 19104, USA
| | | | | | | |
Collapse
|
21
|
Szule JA, Jarvis SE, Hibbert JE, Spafford JD, Braun JEA, Zamponi GW, Wessel GM, Coorssen JR. Calcium-triggered membrane fusion proceeds independently of specific presynaptic proteins. J Biol Chem 2003; 278:24251-4. [PMID: 12764142 DOI: 10.1074/jbc.c300197200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Complexes of specific presynaptic proteins have been hypothesized to drive or catalyze the membrane fusion steps of exocytosis. Here we use a stage-specific preparation to test the roles of SNAREs, synaptotagmin, and SNARE-binding proteins in the mechanism of Ca2+-triggered membrane fusion. Excess exogenous proteins, sufficient to block SNARE interactions, did not inhibit either the Ca2+ sensitivity, extent, or kinetics of fusion. In contrast, despite a limited effect on SNARE and synaptotagmin densities, treatments with high doses of chymotrypsin markedly inhibited fusion. Conversely, low doses of chymotrypsin had no effect on the Ca2+ sensitivity or extent of fusion but did alter the kinetic profile, indicating a more direct involvement of other proteins in the triggered fusion pathway. SNAREs, synaptotagmin, and their immediate binding partners are critical to exocytosis at a stage other than membrane fusion, although they may still influence the triggered steps.
Collapse
Affiliation(s)
- Joseph A Szule
- Department of Physiology and Biophysics, Cellular and Molecular Neurobiology Research Group, University of Calgary, Health Sciences Centre, Faculty of Medicine, Alberta T2N 4N1, Canada
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Coorssen JR, Blank PS, Albertorio F, Bezrukov L, Kolosova I, Chen X, Backlund PS, Zimmerberg J. Regulated secretion: SNARE density, vesicle fusion and calcium dependence. J Cell Sci 2003; 116:2087-97. [PMID: 12692190 DOI: 10.1242/jcs.00374] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
SNAREs such as VAMP, SNAP-25 and syntaxin are essential for intracellular trafficking, but what are their exact molecular roles and how are their interactions with other proteins manifest? Capitalizing on the differential sensitivity of SNAREs to exogenous proteases, we quantified the selective removal of identified SNAREs from native secretory vesicles without loss of fusion competence. Using previously established fusion assays and a high sensitivity immunoblotting protocol, we analyzed the relationship between these SNARE proteins and Ca2+-triggered membrane fusion. Neither the extent of fusion nor the number of intermembrane fusion complexes per vesicle were correlated with the measured density of identified egg cortical vesicle (CV) SNAREs. Without syntaxin, CVs remained fusion competent. Surprisingly, for one (but not another) protease the Ca2+ dependence of fusion was correlated with CV SNARE density, suggesting a native protein complex that associates with SNAREs, the architecture of which ensures high Ca2+ sensitivity. As SNAREs may function during CV docking in vivo, and as further proteolysis after SNARE removal eventually ablates fusion, we hypothesize that the triggered steps of regulated fusion (Ca2+ sensitivity and the catalysis and execution of fusion) require additional proteins that function downstream of SNAREs.
Collapse
Affiliation(s)
- Jens R Coorssen
- Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1855, USA
| | | | | | | | | | | | | | | |
Collapse
|
23
|
Lu X, Ellis-Davies GCR, Levitan ES. Calcium requirements for exocytosis do not delimit the releasable neuropeptide pool. Cell Calcium 2003; 33:267-71. [PMID: 12618147 DOI: 10.1016/s0143-4160(03)00009-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Recently, it was proposed that secretory vesicles have widely varying Ca(2+) thresholds for exocytosis. This model can explain adaptation of secretory responses and predicts that incomplete release is a consequence of insufficient Ca(2+). However, membrane capacitance-based measurements have not supported varying Ca(2+) thresholds. Here, Green Fluorescent Protein (GFP) imaging is used to test whether a Ca(2+) limitation determines the size of the releasable neuropeptide pool in differentiated PC12 cells. We show that depolarization-evoked release correlates with failure to sustain fully elevated [Ca(2+)](i). However, this is coincidental because release remains incomplete when [Ca(2+)](i) is maintained at a relatively high level by application of an ionophore or by dialysis with a buffered Ca(2+) solution. Furthermore, in contradiction with the existence of high threshold vesicles, stimulating maximal release with moderate [Ca(2+)](i) prevents secretory responses to large increases in [Ca(2+)](i) induced by photolysis of the caged dimethoxynitrophenyl-EGTA-4 (DMNPE-4). Thus, optical measurements show that limited capacity for neuropeptide release in response to depolarization is not caused by an insufficient duration of [Ca(2+)](i) elevation or by variation among vesicles in Ca(2+) sensitivity for exocytosis.
Collapse
Affiliation(s)
- Xinghua Lu
- Department of Pharmacology, E1351 Biomedical Science Tower, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | | | | |
Collapse
|