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De Faveri F, Marcotti W, Ceriani F. Sensory adaptation at ribbon synapses in the zebrafish lateral line. J Physiol 2021; 599:3677-3696. [PMID: 34047358 PMCID: PMC7612133 DOI: 10.1113/jp281646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 05/20/2021] [Indexed: 11/22/2022] Open
Abstract
Adaptation is used by sensory systems to adjust continuously their sensitivity to match changes in environmental stimuli. In the auditory and vestibular systems, the release properties of glutamate-containing vesicles at the hair-cell ribbon synapses play a crucial role in sensory adaptation, thus shaping the neural response to sustained stimulation. How ribbon synapses regulate the release of glutamate and how they modulate afferent responses in vivo is still largely unknown. Here, we have used two-photon imaging and electrophysiology to investigate the synaptic transfer characteristics of the hair cells in the context of sensory adaptation in live zebrafish. Prolonged and repeated water-jet stimulation of the hair-cell stereociliary bundles caused adaptation of the action potential firing rate elicited in the afferent neurons. By monitoring glutamate at ribbon synapses using time-lapse imaging, we identified two kinetically distinct release components: a rapid response that was exhausted within 50-100 ms and a slower and sustained response lasting the entire stimulation. After repeated stimulations, the recovery of the fast component followed a biphasic time course. Depression of glutamate release was largely responsible for the rapid firing rate adaptation recorded in the afferent neurons. However, postsynaptic Ca2+ responses had a slower recovery time course than that of glutamate release, indicating that they are also likely to contribute to the afferent firing adaptation. Hair cells also exhibited a form of adaptation during inhibitory bundle stimulations. We conclude that hair cells have optimised their synaptic machinery to encode prolonged stimuli and to maintain their sensitivity to new incoming stimuli.
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Affiliation(s)
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, UK.,Neuroscience Institute, University of Sheffield, Sheffield, UK
| | - Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
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Wang K, Zhao Y, Chen D, Huang C, Fan B, Long R, Hsieh CH, Wang J, Wu MH, Chen J. The Instrumentation of a Microfluidic Analyzer Enabling the Characterization of the Specific Membrane Capacitance, Cytoplasm Conductivity, and Instantaneous Young's Modulus of Single Cells. Int J Mol Sci 2017. [PMID: 28629175 PMCID: PMC5485982 DOI: 10.3390/ijms18061158] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
This paper presents the instrumentation of a microfluidic analyzer enabling the characterization of single-cell biophysical properties, which includes seven key components: a microfluidic module, a pressure module, an imaging module, an impedance module, two LabVIEW platforms for instrument operation and raw data processing, respectively, and a Python code for data translation. Under the control of the LabVIEW platform for instrument operation, the pressure module flushes single cells into the microfluidic module with raw biophysical parameters sampled by the imaging and impedance modules and processed by the LabVIEW platform for raw data processing, which were further translated into intrinsic cellular biophysical parameters using the code developed in Python. Based on this system, specific membrane capacitance, cytoplasm conductivity, and instantaneous Young's modulus of three cell types were quantified as 2.76 ± 0.57 μF/cm², 1.00 ± 0.14 S/m, and 3.79 ± 1.11 kPa for A549 cells (ncell = 202); 1.88 ± 0.31 μF/cm², 1.05 ± 0.16 S/m, and 3.74 ± 0.75 kPa for 95D cells (ncell = 257); 2.11 ± 0.38 μF/cm², 0.87 ± 0.11 S/m, and 5.39 ± 0.89 kPa for H460 cells (ncell = 246). As a semi-automatic instrument with a throughput of roughly 1 cell per second, this prototype instrument can be potentially used for the characterization of cellular biophysical properties.
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Affiliation(s)
- Ke Wang
- State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China.
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China.
| | - Yang Zhao
- Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China.
| | - Deyong Chen
- State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China.
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China.
| | - Chengjun Huang
- Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China.
| | - Beiyuan Fan
- State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China.
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China.
| | - Rong Long
- Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309, USA.
| | - Chia-Hsun Hsieh
- Division of Haematology/Oncology, Department of Internal Medicine, Chang Gung Memorial Hospital at Linkou, Taoyuan City 33302, Taiwan.
| | - Junbo Wang
- State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China.
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China.
| | - Min-Hsien Wu
- Division of Haematology/Oncology, Department of Internal Medicine, Chang Gung Memorial Hospital at Linkou, Taoyuan City 33302, Taiwan.
- Graduate Institute of Biochemical and Biomedical Engineering, Chang Gung University, Taoyuan City 33302, Taiwan.
| | - Jian Chen
- State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China.
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China.
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Collins SC, Do HW, Hastoy B, Hugill A, Adam J, Chibalina MV, Galvanovskis J, Godazgar M, Lee S, Goldsworthy M, Salehi A, Tarasov AI, Rosengren AH, Cox R, Rorsman P. Increased Expression of the Diabetes Gene SOX4 Reduces Insulin Secretion by Impaired Fusion Pore Expansion. Diabetes 2016; 65:1952-61. [PMID: 26993066 PMCID: PMC4996324 DOI: 10.2337/db15-1489] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 03/08/2016] [Indexed: 12/27/2022]
Abstract
The transcription factor Sox4 has been proposed to underlie the increased type 2 diabetes risk linked to an intronic single nucleotide polymorphism in CDKAL1 In a mouse model expressing a mutant form of Sox4, glucose-induced insulin secretion is reduced by 40% despite normal intracellular Ca(2+) signaling and depolarization-evoked exocytosis. This paradox is explained by a fourfold increase in kiss-and-run exocytosis (as determined by single-granule exocytosis measurements) in which the fusion pore connecting the granule lumen to the exterior expands to a diameter of only 2 nm, which does not allow the exit of insulin. Microarray analysis indicated that this correlated with an increased expression of the exocytosis-regulating protein Stxbp6. In a large collection of human islet preparations (n = 63), STXBP6 expression and glucose-induced insulin secretion correlated positively and negatively with SOX4 expression, respectively. Overexpression of SOX4 in the human insulin-secreting cell EndoC-βH2 interfered with granule emptying and inhibited hormone release, the latter effect reversed by silencing STXBP6 These data suggest that increased SOX4 expression inhibits insulin secretion and increased diabetes risk by the upregulation of STXBP6 and an increase in kiss-and-run exocytosis at the expense of full fusion. We propose that pharmacological interventions promoting fusion pore expansion may be effective in diabetes therapy.
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Affiliation(s)
- Stephan C Collins
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K. Université de Bourgogne Franche-Comté, Burgundy, France
| | - Hyun Woong Do
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K
| | - Benoit Hastoy
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K
| | - Alison Hugill
- Mammalian Genetics Unit, MRC Harwell, Oxfordshire, U.K
| | - Julie Adam
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K
| | - Margarita V Chibalina
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K
| | - Juris Galvanovskis
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K. Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, U.K
| | - Mahdieh Godazgar
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K
| | - Sheena Lee
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, U.K
| | | | - Albert Salehi
- Lund University Diabetes Centre, Department of Clinical Sciences, Skåne University Hospital Malmö, Lund University, Malmö, Sweden Department of Neuroscience and Physiology, University of Göteborg, Göteborg, Sweden
| | - Andrei I Tarasov
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K. Oxford National Institute of Health Research, Biomedical Research Centre, Churchill Hospital, Oxford, U.K
| | - Anders H Rosengren
- Lund University Diabetes Centre, Department of Clinical Sciences, Skåne University Hospital Malmö, Lund University, Malmö, Sweden
| | - Roger Cox
- Mammalian Genetics Unit, MRC Harwell, Oxfordshire, U.K
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Radcliffe Department of Medicine, Oxford, U.K. Department of Neuroscience and Physiology, University of Göteborg, Göteborg, Sweden Oxford National Institute of Health Research, Biomedical Research Centre, Churchill Hospital, Oxford, U.K
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Balletta A, Lorenz D, Rummel A, Gerhard R, Bigalke H, Wegner F. Clostridium difficile toxin B inhibits the secretory response of human mast cell line-1 (HMC-1) cells stimulated with high free-Ca²⁺ and GTPγS. Toxicology 2014; 328:48-56. [PMID: 25497110 DOI: 10.1016/j.tox.2014.12.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 11/19/2014] [Accepted: 12/09/2014] [Indexed: 01/06/2023]
Abstract
Clostridium difficile toxins A and B (TcdA and TcdB) belong to the class of large clostridial cytotoxins and inactivate by glucosylation some low molecular mass GTPases of the Rho-family (predominantly Rho, Rac and Cdc42), known as regulators of the actin cytoskeleton. TcdA and B also represent the main virulence factors of the anaerobic gram-positive bacterium that is the causal agent of pseudomembranous colitis. In our study, TcdB was chosen instead of TcdA for the well-known higher cytotoxic potency. Inactivation of Rho-family GTPases by this toxin in our experimental conditions induced morphological changes and reduction of electron-dense mast cell-specific granules in human mast cell line-1 (HMC-1) cells, but not cell death or permeabilisation of plasma-membranes. Previously reported patch-clamp dialysis experiments revealed that high intracellular free-Ca(2+) and GTPγS concentrations are capable of inducing exocytosis as indicated by significant membrane capacitance (Cm) increases in HMC-1 cells. In this study, we investigated the direct effects of TcdB upon HMC-1 cell "stimulated" Cm increase, as well as on "constitutive" secretion of hexosaminidase and interleukin-16 (IL-16). Compared to untreated control cells, HMC-1 cells incubated with TcdB for 3-24h exhibited a significant reduction of the mean absolute and relative Cm increase in response to free-Ca(2+) and GTPγS suggesting an inhibition of secretory processes by TcdB. In conclusion, the HMC-1 cell line represents a suitable model for the study of direct effects of C. difficile toxins on human mast cell secretory activity.
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Affiliation(s)
- Andrea Balletta
- Department of Toxicology, Hannover Medical School, Carl Neuberg Str. 1, 30625 Hannover, Germany; Department of Neurology, Hannover Medical School, Carl Neuberg Str. 1, 30625 Hannover, Germany.
| | - Dorothea Lorenz
- Department of Cellular Imaging and Electron Microscopy, Leibniz Institute of Molecular Pharmacology, Robert Rössle Str. 10, 13125 Berlin, Germany.
| | - Andreas Rummel
- Department of Toxicology, Hannover Medical School, Carl Neuberg Str. 1, 30625 Hannover, Germany.
| | - Ralf Gerhard
- Department of Toxicology, Hannover Medical School, Carl Neuberg Str. 1, 30625 Hannover, Germany.
| | - Hans Bigalke
- Department of Toxicology, Hannover Medical School, Carl Neuberg Str. 1, 30625 Hannover, Germany.
| | - Florian Wegner
- Department of Neurology, Hannover Medical School, Carl Neuberg Str. 1, 30625 Hannover, Germany.
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Rituper B, Guček A, Jorgačevski J, Flašker A, Kreft M, Zorec R. High-resolution membrane capacitance measurements for the study of exocytosis and endocytosis. Nat Protoc 2013; 8:1169-83. [PMID: 23702833 DOI: 10.1038/nprot.2013.069] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In order to understand exocytosis and endocytosis, it is necessary to study these processes directly. An elegant way to do this is by measuring plasma membrane capacitance (C(m)), a parameter proportional to cell surface area, the fluctuations of which are due to fusion and fission of secretory and other vesicles. Here we describe protocols that enable high-resolution C(m) measurements in macroscopic and microscopic modes. Macroscopic mode, performed in whole-cell configuration, is used for measuring bulk C(m) changes in the entire membrane area, and it enables the introduction of exocytosis stimulators or inhibitors into the cytosol through the patch pipette. Microscopic mode, performed in cell-attached configuration, enables measurements of C(m) with attofarad resolution and allows characterization of fusion pore properties. Although we usually apply these protocols to primary pituitary cells and astrocytes, they can be adapted and used for other cell types. After initial hardware setup and culture preparation, several C(m) measurements can be performed daily.
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Affiliation(s)
- Boštjan Rituper
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, Ljubljana, Slovenia
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Gregory FD, Pangrsic T, Calin-Jageman IE, Moser T, Lee A. Harmonin enhances voltage-dependent facilitation of Cav1.3 channels and synchronous exocytosis in mouse inner hair cells. J Physiol 2013; 591:3253-69. [PMID: 23613530 DOI: 10.1113/jphysiol.2013.254367] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cav1.3 channels mediate Ca(2+) influx that triggers exocytosis of glutamate at cochlear inner hair cell (IHC) synapses. Harmonin is a PDZ-domain-containing protein that interacts with the C-terminus of the Cav1.3 α1 subunit (α11.3) and controls cell surface Cav1.3 levels by promoting ubiquitin-dependent proteosomal degradation. However, PDZ-domain-containing proteins have diverse functions and regulate other Cav1.3 properties, which could collectively influence presynaptic transmitter release. Here, we report that harmonin binding to the α11.3 distal C-terminus (dCT) enhances voltage-dependent facilitation (VDF) of Cav1.3 currents both in transfected HEK293T cells and in mouse inner hair cells. In HEK293T cells, this effect of harmonin was greater for Cav1.3 channels containing the auxiliary Cav β1 than with the β2 auxiliary subunit. Cav1.3 channels lacking the α11.3 dCT were insensitive to harmonin modulation. Moreover, the 'deaf-circler' dfcr mutant form of harmonin, which does not interact with the α11.3 dCT, did not promote VDF. In mature IHCs from mice expressing the dfcr harmonin mutant, Cav1.3 VDF was less than in control IHCs. This difference was not observed between control and dfcr IHCs prior to hearing onset. Membrane capacitance recordings from dfcr IHCs revealed a role for harmonin in synchronous exocytosis and in increasing the efficiency of Ca(2+) influx for triggering exocytosis. Collectively, our results indicate a multifaceted presynaptic role of harmonin in IHCs in regulating Cav1.3 Ca(2+) channels and exocytosis.
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Affiliation(s)
- Frederick D Gregory
- Department of Molecular Physiology and Biophysics, University of Iowa, 5-610 Bowen Science Building, 51 Newton Rd, Iowa City, IA 52242, USA
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Lindau M. High resolution electrophysiological techniques for the study of calcium-activated exocytosis. Biochim Biophys Acta Gen Subj 2011; 1820:1234-42. [PMID: 22209782 DOI: 10.1016/j.bbagen.2011.12.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 12/09/2011] [Accepted: 12/10/2011] [Indexed: 11/30/2022]
Abstract
BACKGROUND Neurotransmitters, neuropeptides and hormones are released from secretory vesicles of nerve terminals and neuroendocrine cells by calcium-activated exocytosis. A key step in this process is the formation of a fusion pore between the vesicle membrane and the plasma membrane. Exocytotic fusion leads to an increase in plasma membrane area that can be measured as a proportional increase in plasma membrane capacitance. SCOPE OF REVIEW High resolution capacitance measurements in single cells, nerve terminals and small membrane patches have become possible with the development of the patch clamp technique. This review discusses the methods of whole cell patch clamp capacitance measurements and their use in conjunction with voltage clamp pulse stimulation and with stimulation by photorelease of caged calcium. It also discusses patch capacitance measurements for the study of single exocytotic events and fusion pore properties in neuroendocrine cells and nerve terminals. MAJOR CONCLUSIONS Capacitance measurements provide high resolution information on the extent and time course of fusion for the characterization of vesicle pools and the kinetics of exocytosis. They allow the characterization of the mode of fusion including distinction of single vesicle full fusion, transient kiss-and-run fusion or multivesicular compound exocytosis. Furthermore, measurement of fusion pore conductances and their dynamic behavior has enabled the characterization of fusion pore properties in a way that resembles the characterization of ion channel function through single channel recordings. GENERAL SIGNIFICANCE The combination of patch clamp capacitance measurements with pharmacological and molecular manipulations of exocytosis is emerging as a powerful approach to investigate the molecular mechanisms of calcium-activated exocytotic fusion pore formation. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signalling.
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Affiliation(s)
- Manfred Lindau
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.
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Zhang H, Qu A, Luo J, Luo J. Error analysis of Cm measurement under the whole-cell patch-clamp recording. J Neurosci Methods 2009; 185:307-14. [PMID: 19835911 DOI: 10.1016/j.jneumeth.2009.10.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 10/03/2009] [Accepted: 10/06/2009] [Indexed: 10/20/2022]
Abstract
We present a method for analysing propagation errors in membrane capacitance (C(m)) measurements under the whole-cell patch-clamp configuration, which mainly focusses on errors in C(m) estimates due to the 'residual' fast capacitance (DeltaC(p)). The method employs a quasi-phasor diagram for visualisation of the analysis. Our results show that both under- and over-compensation of fast capacitance will cause errors in C(m), and errors in the magnitude and in the phase angle of cell admittance make their respective and opposite contributions to propagation errors in C(m). Within optimal frequencies, over-compensation of fast capacitance will cause a smaller propagation error in C(m) and produce more accurate C(m) estimates than under-compensation of fast capacitance will do. Information about how other cell parameters, such as smaller series resistance, baseline C(m) value and the stimulus frequency, change the total error in C(m) due to DeltaC(p) is also provided. Guidelines for accurate C(m) recordings are given to make it easy for users to perform their own error analysis.
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Affiliation(s)
- Hao Zhang
- Institute of Biophysics and Biochemistry, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, Hubei Province, People's Republic of China
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Yaradanakul A, Wang TM, Lariccia V, Lin MJ, Shen C, Liu X, Hilgemann DW. Massive Ca-induced membrane fusion and phospholipid changes triggered by reverse Na/Ca exchange in BHK fibroblasts. ACTA ACUST UNITED AC 2008; 132:29-50. [PMID: 18562498 PMCID: PMC2442179 DOI: 10.1085/jgp.200709865] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Baby hamster kidney (BHK) fibroblasts increase their cell capacitance by 25-100% within 5 s upon activating maximal Ca influx via constitutively expressed cardiac Na/Ca exchangers (NCX1). Free Ca, measured with fluo-5N, transiently exceeds 0.2 mM with total Ca influx amounting to approximately 5 mmol/liter cell volume. Capacitance responses are half-maximal when NCX1 promotes a free cytoplasmic Ca of 0.12 mM (Hill coefficient approximately 2). Capacitance can return to baseline in 1-3 min, and responses can be repeated several times. The membrane tracer, FM 4-64, is taken up during recovery and can be released at a subsequent Ca influx episode. Given recent interest in signaling lipids in membrane fusion, we used green fluorescent protein (GFP) fusions with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) and diacylglycerol (DAG) binding domains to analyze phospholipid changes in relation to these responses. PI(4,5)P(2) is rapidly cleaved upon activating Ca influx and recovers within 2 min. However, PI(4,5)P(2) depletion by activation of overexpressed hM1 muscarinic receptors causes only little membrane fusion, and subsequent fusion in response to Ca influx remains massive. Two results suggest that DAG may be generated from sources other than PI(4,5)P in these protocols. First, acylglycerols are generated in response to elevated Ca, even when PI(4,5)P(2) is metabolically depleted. Second, DAG-binding C1A-GFP domains, which are brought to the cell surface by exogenous ligands, translocate rapidly back to the cytoplasm in response to Ca influx. Nevertheless, inhibitors of PLCs and cPLA2, PI(4,5)P(2)-binding peptides, and PLD modification by butanol do not block membrane fusion. The cationic agents, FM 4-64 and heptalysine, bind profusely to the extracellular cell surface during membrane fusion. While this binding might reflect phosphatidylserine (PS) "scrambling" between monolayers, it is unaffected by a PS-binding protein, lactadherin, and by polylysine from the cytoplasmic side. Furthermore, the PS indicator, annexin-V, binds only slowly after fusion. Therefore, we suggest that the luminal surfaces of membrane vesicles that fuse to the plasmalemma may be rather anionic. In summary, our results provide no support for any regulatory or modulatory role of phospholipids in Ca-induced membrane fusion in fibroblasts.
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Affiliation(s)
- Alp Yaradanakul
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
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Borges R, Camacho M, Gillis KD. Measuring secretion in chromaffin cells using electrophysiological and electrochemical methods. Acta Physiol (Oxf) 2008; 192:173-84. [PMID: 18021323 DOI: 10.1111/j.1748-1716.2007.01814.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Our present understanding of exocytosis of catecholamines has benefited tremendously from the arrival of single-cell electrochemical methods (amperometry and voltammetry), electrophysiological techniques (whole-cell and patch capacitance) and from the combination of both techniques (patch amperometry). In this brief review, we will outline the strengths and limitations of amperometric and electrophysiological methods and highlight the major contribution obtained with the use of these techniques in chromaffin cells.
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Affiliation(s)
- R Borges
- Unidad de Farmacología, Facultad de Medicina, Universidad de La Laguna, Tenerife, Spain.
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