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Eisner D, Neher E, Taschenberger H, Smith G. Physiology of intracellular calcium buffering. Physiol Rev 2023; 103:2767-2845. [PMID: 37326298 DOI: 10.1152/physrev.00042.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 05/08/2023] [Accepted: 06/11/2023] [Indexed: 06/17/2023] Open
Abstract
Calcium signaling underlies much of physiology. Almost all the Ca2+ in the cytoplasm is bound to buffers, with typically only ∼1% being freely ionized at resting levels in most cells. Physiological Ca2+ buffers include small molecules and proteins, and experimentally Ca2+ indicators will also buffer calcium. The chemistry of interactions between Ca2+ and buffers determines the extent and speed of Ca2+ binding. The physiological effects of Ca2+ buffers are determined by the kinetics with which they bind Ca2+ and their mobility within the cell. The degree of buffering depends on factors such as the affinity for Ca2+, the Ca2+ concentration, and whether Ca2+ ions bind cooperatively. Buffering affects both the amplitude and time course of cytoplasmic Ca2+ signals as well as changes of Ca2+ concentration in organelles. It can also facilitate Ca2+ diffusion inside the cell. Ca2+ buffering affects synaptic transmission, muscle contraction, Ca2+ transport across epithelia, and the killing of bacteria. Saturation of buffers leads to synaptic facilitation and tetanic contraction in skeletal muscle and may play a role in inotropy in the heart. This review focuses on the link between buffer chemistry and function and how Ca2+ buffering affects normal physiology and the consequences of changes in disease. As well as summarizing what is known, we point out the many areas where further work is required.
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Affiliation(s)
- David Eisner
- Division of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom
| | - Erwin Neher
- Membrane Biophysics Laboratory, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
| | - Holger Taschenberger
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Godfrey Smith
- School of Cardiovascular and Metabolic Health, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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2
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Hennes A, Devroe J, De Clercq K, Ciprietti M, Held K, Luyten K, Van Ranst N, Maenhoudt N, Peeraer K, Vankelecom H, Voets T, Vriens J. Protease secretions by the invading blastocyst induce calcium oscillations in endometrial epithelial cells via the protease-activated receptor 2. Reprod Biol Endocrinol 2023; 21:37. [PMID: 37060079 PMCID: PMC10105462 DOI: 10.1186/s12958-023-01085-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 03/23/2023] [Indexed: 04/16/2023] Open
Abstract
BACKGROUND Early embryo implantation is a complex phenomenon characterized by the presence of an implantation-competent blastocyst and a receptive endometrium. Embryo development and endometrial receptivity must be synchronized and an adequate two-way dialogue between them is necessary for maternal recognition and implantation. Proteases have been described as blastocyst-secreted proteins involved in the hatching process and early implantation events. These enzymes stimulate intracellular calcium signaling pathways in endometrial epithelial cells (EEC). However, the exact molecular players underlying protease-induced calcium signaling, the subsequent downstream signaling pathways and the biological impact of its activation remain elusive. METHODS To identify gene expression of the receptors and ion channels of interest in human and mouse endometrial epithelial cells, RNA sequencing, RT-qPCR and in situ hybridization experiments were conducted. Calcium microfluorimetric experiments were performed to study their functional expression. RESULTS We showed that trypsin evoked intracellular calcium oscillations in EEC of mouse and human, and identified the protease-activated receptor 2 (PAR2) as the molecular entity initiating protease-induced calcium responses in EEC. In addition, this study unraveled the molecular players involved in the downstream signaling of PAR2 by showing that depletion and re-filling of intracellular calcium stores occurs via PLC, IP3R and the STIM1/Orai1 complex. Finally, in vitro experiments in the presence of a specific PAR2 agonist evoked an upregulation of the 'Window of implantation' markers in human endometrial epithelial cells. CONCLUSIONS These findings provide new insights into the blastocyst-derived protease signaling and allocate a key role for PAR2 as maternal sensor for signals released by the developing blastocyst.
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Grants
- C14/18/106 Research Council of the KU Leuven
- C14/18/106 Research Council of the KU Leuven
- C14/18/106 Research Council of the KU Leuven
- C14/18/106 Research Council of the KU Leuven
- G.0D1417N, G.084515N, G.0A6719N, 12R4622N, 12U7918N Fonds Wetenschappelijk Onderzoek
- G.0D1417N, G.084515N, G.0A6719N, 12R4622N, 12U7918N Fonds Wetenschappelijk Onderzoek
- G.0D1417N, G.084515N, G.0A6719N, 12R4622N, 12U7918N Fonds Wetenschappelijk Onderzoek
- G.0D1417N, G.084515N, G.0A6719N, 12R4622N, 12U7918N Fonds Wetenschappelijk Onderzoek
- G.0D1417N, G.084515N, G.0A6719N, 12R4622N, 12U7918N Fonds Wetenschappelijk Onderzoek
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Affiliation(s)
- Aurélie Hennes
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 Box 611, 3000, Leuven, Belgium
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, VIB Center for Brain & Disease Research, KU Leuven, Herestraat 49 Box 802, 3000, Leuven, Belgium
| | - Johanna Devroe
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 Box 611, 3000, Leuven, Belgium
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, VIB Center for Brain & Disease Research, KU Leuven, Herestraat 49 Box 802, 3000, Leuven, Belgium
- Leuven University Fertility Center, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Katrien De Clercq
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 Box 611, 3000, Leuven, Belgium
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, VIB Center for Brain & Disease Research, KU Leuven, Herestraat 49 Box 802, 3000, Leuven, Belgium
| | - Martina Ciprietti
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 Box 611, 3000, Leuven, Belgium
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, VIB Center for Brain & Disease Research, KU Leuven, Herestraat 49 Box 802, 3000, Leuven, Belgium
| | - Katharina Held
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 Box 611, 3000, Leuven, Belgium
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, VIB Center for Brain & Disease Research, KU Leuven, Herestraat 49 Box 802, 3000, Leuven, Belgium
| | - Katrien Luyten
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 Box 611, 3000, Leuven, Belgium
| | - Nele Van Ranst
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, VIB Center for Brain & Disease Research, KU Leuven, Herestraat 49 Box 802, 3000, Leuven, Belgium
| | - Nina Maenhoudt
- Laboratory of Tissue Plasticity in Health and Disease, Cluster of Stem Cell and Developmental Biology, Department of Development and Regeneration, KU Leuven, Herestraat 49 Box 804, 3000, Leuven, Belgium
| | - Karen Peeraer
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 Box 611, 3000, Leuven, Belgium
- Leuven University Fertility Center, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Hugo Vankelecom
- Laboratory of Tissue Plasticity in Health and Disease, Cluster of Stem Cell and Developmental Biology, Department of Development and Regeneration, KU Leuven, Herestraat 49 Box 804, 3000, Leuven, Belgium
| | - Thomas Voets
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, VIB Center for Brain & Disease Research, KU Leuven, Herestraat 49 Box 802, 3000, Leuven, Belgium
| | - Joris Vriens
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 Box 611, 3000, Leuven, Belgium.
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, VIB Center for Brain & Disease Research, KU Leuven, Herestraat 49 Box 802, 3000, Leuven, Belgium.
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Seward EP, Wykes RC. Membrane Capacitance Measurements of Stimulus-Evoked Exocytosis in Adrenal Chromaffin Cells. Methods Mol Biol 2023; 2565:187-202. [PMID: 36205895 DOI: 10.1007/978-1-0716-2671-9_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Research using membrane capacitance (Cm) measurements in adrenal chromaffin cells has transformed our understanding of the molecular mechanisms controlling regulated exocytosis. This is in part due to the exquisite temporal resolution of the technique, and the possibility of combining quantification of exo-/endocytosis at the whole-cell level, with the ability to simultaneously monitor and control the calcium signals triggering vesicle fusion. In this regard, experiments performed with Cm measurements complement amperometry experiments that give a measure of secreted transmitter and the behavior of the fusion pore, and fluorescent microscopy studies used to monitor vesicle and protein dynamics in imaged regions of the cell. In this chapter, we provide a detailed account of the methodology used to perform whole-cell patch clamp measurements of Cm in combination with voltage-clamp recordings of voltage-gated calcium channels to quantify stimulus-secretion coupling in chromaffin cells. Stimulus protocols developed for investigation of functionally distinct releasable vesicle pools are also described.
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Affiliation(s)
| | - Robert C Wykes
- Department of Clinical and Experimental Epilepsy, Queen Square Institute of Neurology, University College London, London, UK
- Nanomedicine Lab, Faculty of Biology Medicine & Health, University of Manchester, Manchester, UK
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Shkryl VM. The spatio-temporal properties of calcium transients in hippocampal pyramidal neurons in vitro. Front Cell Neurosci 2022; 16:1054950. [PMID: 36589284 PMCID: PMC9795003 DOI: 10.3389/fncel.2022.1054950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 11/24/2022] [Indexed: 12/15/2022] Open
Abstract
The spatio-temporal properties of calcium signals were studied in cultured pyramidal neurons of the hippocampus using two-dimensional fluorescence microscopy and ratiometric dye Fura-2. Depolarization-induced Ca2+ transients revealed an asynchronous delayed increase in free Ca2+ concentration. We found that the level of free resting calcium in the cell nucleus is significantly lower compared to the soma, sub-membrane, and dendritic tree regions. Calcium release from the endoplasmic reticulum under the action of several stimuli (field stimulation, high K+ levels, and caffeine) occurs in all areas studied. Under depolarization, calcium signals developed faster in the dendrites than in other areas, while their amplitude was significantly lower since larger and slower responses inside the soma. The peak value of the calcium response to the application of 10 mM caffeine, ryanodine receptors (RyRs) agonist, does not differ in the sub-membrane zone, central region, and nucleus but significantly decreases in the dendrites. In the presence of caffeine, the delay of Ca2+ signals between various areas under depolarization significantly declined. Thirty percentage of the peak amplitude of Ca2+ transients at prolonged electric field stimulation corresponded to calcium release from the ER store by RyRs, while short-term stimulation did not depend on them. 20 μM dantrolene, RyRs inhibitor, significantly reduces Ca2+ transient under high K+ levels depolarization of the neuron. RyRs-mediated enhancement of the Ca2+ signal is more pronounced in the central part and nucleus compared to the sub-membrane or dendrites regions of the neuron. In summary, using the ratiometric imaging allowed us to obtain additional information about the involvement of RyRs in the intracellular dynamics of Ca2+ signals induced by depolarization or electrical stimulation train, with an underlying change in Ca2+ concentration in various regions of interest in hippocampal pyramidal neurons.
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Becchetti A, Duranti C, Arcangeli A. Dynamics and physiological meaning of complexes between ion channels and integrin receptors: the case of Kv11.1. Am J Physiol Cell Physiol 2022; 322:C1138-C1150. [PMID: 35442831 DOI: 10.1152/ajpcell.00107.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The cellular functions are regulated by a complex interplay of diffuse and local signals. Experimental work in cell physiology has led to recognize that understanding a cell's dynamics requires a deep comprehension of local fluctuations of cytosolic regulators. Macromolecular complexes are major determinants of local signaling. Multi-enzyme assemblies limit the diffusion restriction to reaction kinetics by direct exchange of metabolites. Likewise, close coupling of ion channels and transporters modulate the ion concentration around a channel mouth or transporter binding site. Extreme signal locality is brought about by conformational coupling between membrane proteins, as is typical of mechanotransduction. A paradigmatic case is integrin-mediated cell adhesion. Sensing the extracellular microenvironment and providing an appropriate response is essential in growth and development and has innumerable pathological implications. The process involves bidirectional signal transduction by complex supra-molecular structures that link integrin receptors to ion channels and transporters, growth factor receptors, cytoskeletal elements and other regulatory elements. The dynamics of such complexes is only beginning to be understood. A thoroughly studied example is the association between integrin receptors and the voltage-gated K+ channels Kv11.1. These channels are widely expressed in early embryos, where their physiological roles are poorly understood and apparently different from the shaping of action potential firing in the adult. Hints about these roles come from studies in cancer cells, where Kv11.1 is often overexpressed and appears to re-assume functions, such as controlling cell proliferation/differentiation, apoptosis and migration. Kv11.1 is implicated in these processes through its linking to integrin subunits.
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Affiliation(s)
- Andrea Becchetti
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano, Italy
| | - Claudia Duranti
- Department of Experimental and Clinical Medicine. University of Florence, Firenze, Italy
| | - Annarosa Arcangeli
- Department of Experimental and Clinical Medicine. University of Florence, Firenze, Italy
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Serrat R, Oliveira-Pinto A, Marsicano G, Pouvreau S. Imaging mitochondrial calcium dynamics in the central nervous system. J Neurosci Methods 2022; 373:109560. [PMID: 35320763 DOI: 10.1016/j.jneumeth.2022.109560] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 03/04/2022] [Accepted: 03/06/2022] [Indexed: 12/28/2022]
Abstract
Mitochondrial calcium handling is a particularly active research area in the neuroscience field, as it plays key roles in the regulation of several functions of the central nervous system, such as synaptic transmission and plasticity, astrocyte calcium signaling, neuronal activity… In the last few decades, a panel of techniques have been developed to measure mitochondrial calcium dynamics, relying mostly on photonic microscopy, and including synthetic sensors, hybrid sensors and genetically encoded calcium sensors. The goal of this review is to endow the reader with a deep knowledge of the historical and latest tools to monitor mitochondrial calcium events in the brain, as well as a comprehensive overview of the current state of the art in brain mitochondrial calcium signaling. We will discuss the main calcium probes used in the field, their mitochondrial targeting strategies, their key properties and major drawbacks. In addition, we will detail the main roles of mitochondrial calcium handling in neuronal tissues through an extended report of the recent studies using mitochondrial targeted calcium sensors in neuronal and astroglial cells, in vitro and in vivo.
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Affiliation(s)
- Roman Serrat
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1215 NeuroCentre Magendie, France; University of Bordeaux, Bordeaux 33077, France
| | - Alexandre Oliveira-Pinto
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1215 NeuroCentre Magendie, France; University of Bordeaux, Bordeaux 33077, France
| | - Giovanni Marsicano
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1215 NeuroCentre Magendie, France; University of Bordeaux, Bordeaux 33077, France
| | - Sandrine Pouvreau
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1215 NeuroCentre Magendie, France; University of Bordeaux, Bordeaux 33077, France.
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7
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Hess S, Pouzat C, Paeger L, Pippow A, Kloppenburg P. Analysis of neuronal Ca 2+ handling properties by combining perforated patch clamp recordings and the added buffer approach. Cell Calcium 2021; 97:102411. [PMID: 34082340 DOI: 10.1016/j.ceca.2021.102411] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 03/25/2021] [Accepted: 04/15/2021] [Indexed: 12/11/2022]
Abstract
Ca2+ functions as an important intracellular signal for a wide range of cellular processes. These processes are selectively activated by controlled spatiotemporal dynamics of the free cytosolic Ca2+. Intracellular Ca2+ dynamics are regulated by numerous cellular parameters. Here, we established a new way to determine neuronal Ca2+ handling properties by combining the 'added buffer' approach [1] with perforated patch-clamp recordings [2]. Since the added buffer approach typically employs the standard whole-cell configuration for concentration-controlled Ca2+ indicator loading, it only allows for the reliable estimation of the immobile fraction of intracellular Ca2+ buffers. Furthermore, crucial components of intracellular signaling pathways are being washed out during prolonged whole-cell recordings, leading to cellular deterioration. By combining the added buffer approach with perforated patch-clamp recordings, these issues are circumvented, allowing the precise quantification of the cellular Ca2+ handling properties, including immobile as well as mobile Ca2+ buffers.
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Affiliation(s)
- Simon Hess
- Institute for Zoology, Biocenter, Cologne Excellence Cluster in Aging Associated Diseases (CECAD), and Center of Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Christophe Pouzat
- Université de Paris, CNRS, MAP5 UMR 8145, 45, rue des Saints-Pères, 75006 Paris, France
| | - Lars Paeger
- Institute for Zoology, Biocenter, Cologne Excellence Cluster in Aging Associated Diseases (CECAD), and Center of Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Andreas Pippow
- Institute for Zoology, Biocenter, Cologne Excellence Cluster in Aging Associated Diseases (CECAD), and Center of Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Peter Kloppenburg
- Institute for Zoology, Biocenter, Cologne Excellence Cluster in Aging Associated Diseases (CECAD), and Center of Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany.
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A calcium optimum for cytotoxic T lymphocyte and natural killer cell cytotoxicity. Semin Cell Dev Biol 2020; 115:10-18. [PMID: 33358089 DOI: 10.1016/j.semcdb.2020.12.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 11/24/2020] [Accepted: 12/08/2020] [Indexed: 02/07/2023]
Abstract
Cytotoxic T lymphocytes (CTL) and natural killer (NK) cells are required for host defense. They destroy malignant target cells like cancer cells. Among metal cations, Ca2+ plays a prescinded role for CTL and NK cytotoxicity as it is the only cation used as ubiquitous second messenger. Measuring intracellular Ca2+ concentrations [Ca2+]int in single cells has greatly changed our understanding of Ca2+ signaling. Yet, comparing the role of Ca2+ in the pre-[Ca2+]int and [Ca2+]int measurement era reveals that even in the pre-[Ca2+]int measurement era (before 1980), the functions of Ca2+ and some other metal cations for the cytotoxic immune response were well established. It was even shown that Ca2+ influx across the plasma membrane but not Ca2+ release from intracellular sources is relevant for lymphocyte cytotoxicity and that very little Ca2+ is needed for efficient lymphocyte cytotoxicity against cancer cells. In the [Ca2+]int measurement era after 1980, many of the important findings were better and more quantitatively refined and in addition the molecules important for Ca2+ transport were defined. The unexpected finding that there is a Ca2+ optimum of CTL and NK cell cytotoxicity deserves some attention and may be important for anti-cancer therapy.
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Held K, Aloi VD, Freitas ACN, Janssens A, Segal A, Przibilla J, Philipp SE, Wang YT, Voets T, Vriens J. Pharmacological properties of TRPM3 isoforms are determined by the length of the pore loop. Br J Pharmacol 2020; 179:3560-3575. [PMID: 32780479 PMCID: PMC9290681 DOI: 10.1111/bph.15223] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 06/17/2020] [Accepted: 07/08/2020] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND AND PURPOSE Transient receptor potential melastatin 3 (TRPM3) is a non-selective cation channel that plays a pivotal role in the peripheral nervous system as a transducer of painful heat signals. Alternative splicing gives rise to several TRPM3 variants. The functional consequences of these splice isoforms are poorly understood. Here, the pharmacological properties of TRPM3 variants arising from alternative splicing in the pore-forming region were compared. EXPERIMENTAL APPROACH Calcium microfluorimetry and patch clamp recordings were used to compare the properties of heterologously expressed TRPM3α1 (long pore variant) and TRPM3α2-α6 (short pore variants). Furthermore, site-directed mutagenesis was done to investigate the influence of the length of the pore loop on the channel function. KEY RESULTS All short pore loop TRPM3α variants (TRPM3α2-α6) were activated by the neurosteroid pregnenolone sulphate (PS) and by nifedipine, whereas the long pore loop variant TRPM3α1 was insensitive to either compound. In contrast, TRPM3α1 was robustly activated by clotrimazole, a compound that does not directly activate the short pore variants but potentiates their responses to PS. Clotrimazole-activated TRPM3α1 currents were largely insensitive to established TRPM3α2 antagonists and were only partially inhibited upon activation of the μ opioid receptor. Finally, by creating a set of mutant channels with pore loops of intermediate length, we showed that the length of the pore loop dictates differential channel activation by PS and clotrimazole. CONCLUSION AND IMPLICATIONS Alternative splicing in the pore-forming region of TRPM3 defines the channel's pharmacological properties, which depend critically on the length of the pore-forming loop.
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Affiliation(s)
- Katharina Held
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Leuven, Belgium.,Laboratory of Ion Channel Research, VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium.,Department of Molecular Medicine, KU Leuven, Leuven, Belgium.,DM Centre for Brain Health, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Vincenzo Davide Aloi
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Leuven, Belgium.,Laboratory of Ion Channel Research, VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium.,Department of Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Ana Cristina Nogueira Freitas
- Laboratory of Ion Channel Research, VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium.,Department of Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Annelies Janssens
- Laboratory of Ion Channel Research, VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium.,Department of Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Andrei Segal
- Laboratory of Ion Channel Research, VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium.,Department of Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Julia Przibilla
- Experimental and Clinical Pharmacology and Toxicology/Center for Molecular Signaling (PZMS), Saarland University, Homburg, Germany
| | - Stephan Ernst Philipp
- Experimental and Clinical Pharmacology and Toxicology/Center for Molecular Signaling (PZMS), Saarland University, Homburg, Germany
| | - Yu Tian Wang
- DM Centre for Brain Health, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Thomas Voets
- Laboratory of Ion Channel Research, VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium.,Department of Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Joris Vriens
- Laboratory of Endometrium, Endometriosis and Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
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10
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Naik PA. Modeling the mechanics of calcium regulation in T lymphocyte: A finite element method approach. INT J BIOMATH 2020. [DOI: 10.1142/s1793524520500382] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Changes in cellular Ca[Formula: see text] concentration control a variety of physiological activities including hormone and neurotransmitter release, muscular contraction, synaptic plasticity, ionic channel permeability, apoptosis, enzyme activity, gene transcription and reproduction process. Spatial–temporal Ca[Formula: see text] dynamics due to Ca[Formula: see text] release, buffering and re-uptaking plays a central role in studying the Ca[Formula: see text] regulation in T lymphocytes. In most cases, Ca[Formula: see text] has its major signaling function when it is elevated in the cytosolic compartment. In this paper, a two-dimensional mathematical model to study spatiotemporal variations of intracellular Ca[Formula: see text] concentration in T lymphocyte cell is proposed and investigated. The cell is assumed to be a circular shaped geometrical domain for the representation of properties of Ca[Formula: see text] dynamics within the cell including important parameters. Ca[Formula: see text] binding proteins for the dynamics of Ca[Formula: see text] are itself buffer and other physiological parameters located in Ca[Formula: see text] stores. The model incorporates the important biophysical processes like diffusion, reaction, voltage-gated Ca[Formula: see text] channel, leak from endoplasmic reticulum (ER), efflux from cytosol to ER via sarco–ER Ca[Formula: see text] adenosine triphosphate (SERCA) pumps, buffers and Na[Formula: see text] exchanger. The proposed mathematical model is solved using a finite difference method and the finite element method. Appropriate initial and boundary conditions are incorporated in the model based on biophysical conditions of the problem. Computer simulations in MATLAB R2019b are employed to investigate mathematical models of reaction–diffusion equation. The effect of source, buffer, Na[Formula: see text]/Ca[Formula: see text] exchanger, etc. on spatial and temporal patterns of Ca[Formula: see text] in T lymphocyte has been studied with the help of numerical results. From the obtained results, it is observed that, the coordinated combination of the incorporated parameters plays a significant role in Ca[Formula: see text] regulation in T lymphocytes. ER leak and voltage-gated Ca[Formula: see text] channel provides the necessary Ca[Formula: see text] to the cell when required for its proper functioning, while on the other side buffers, SERCA pump and Na[Formula: see text]/Ca[Formula: see text] exchanger makes balance in the Ca[Formula: see text] concentration, so as to prevent the cell from death as higher concentration for longer time is harmful for the cell and can cause cell death.
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Affiliation(s)
- Parvaiz Ahmad Naik
- School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, P. R. China
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11
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Naik PA, Zu J. Modeling and simulation of spatial-temporal calcium distribution in T lymphocyte cell by using a reaction-diffusion equation. J Bioinform Comput Biol 2020; 18:2050013. [PMID: 32372713 DOI: 10.1142/s0219720020500134] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
T lymphocytes are white blood cells that play a central role in cell-mediated immunity. Ca2+ has its major signaling function when it is elevated in the cytosolic compartment. The free cytosolic Ca2+ dynamics plays a very important role in the activation, and fate decision process in the T lymphocytes. Here, we develop a quantitative spatio-temporal Ca2+ dynamic model which includes, the Ca2+ releasing channels ER leak and voltage-gated Ca2+ channel, buffering and re-uptaking mechanism in the T lymphocytes. In this model, the cell is represented as a circular-shaped geometrical domain. This representation introduces modeling flexibility needed for detailed representation of the properties of Ca2+ dynamics in the cell including important parameters. The proposed mathematical model is solved using a finite difference method and the finite element method. Appropriate initial and boundary conditions are incorporated in the model based on biophysical conditions of the problem. Computer simulations in MATLAB R2010a are employed to investigate mathematical models of reaction-diffusion equation. The estimation is based on reaction-diffusion equation associated with biophysical and biochemical reactions taking place in the cell. From our results, it is observed that, the coordinated combination of the incorporated parameters plays a significant role in Ca2+ regulation in T lymphocytes. ER leak and voltage-gated Ca2+ channel provides the necessary Ca2+ to the cell when required for its proper functioning, while on the other side buffers and Na+/Ca2+ exchanger makes balance in the Ca2+ concentration, so as to prevent the cell from death as higher concentration for longer time is harmful for the cell and can cause cell death. These results have been used to study the relationship of Ca2+ concentration with parameters like VGCC, Na+/Ca2+ exchanger, ER leak and buffers. The significance of the study reveals that there is a significant variation in Ca2+ profiles due to the effect of VGCC, Na+/Ca2+ exchanger, ER leak, and buffers. The results give us better insights of coordinated effect of VGCC, Na+/Ca2+ exchanger, ER leak, and buffers on Ca2+ distribution in T lymphocytes. T lymphocytes are the primary host cells to receive the viral infections which transmits the signal then to other cell types. The proper quantity of Ca2+ concentration makes T lymphocytes more active and healthier to fight the infection properly and can protect the immune system from various fatal viral infections. Thus, the application of the study lies in the field of immunology to protect a susceptible from various viral infectious diseases like HIV, HBV, HINI, etc. by strengthening the immune system. The outcomes of the study reveal that the applied finite element method is computationally very strong and effective to analyze differential equations that arise in Ca2+ dynamics.
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Affiliation(s)
- Parvaiz Ahmad Naik
- School of Mathematics and Statistics, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, P. R. China
| | - Jian Zu
- School of Mathematics and Statistics, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, P. R. China
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Schwaller B. Cytosolic Ca 2+ Buffers Are Inherently Ca 2+ Signal Modulators. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a035543. [PMID: 31308146 DOI: 10.1101/cshperspect.a035543] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
For precisely regulating intracellular Ca2+ signals in a time- and space-dependent manner, cells make use of various components of the "Ca2+ signaling toolkit," including Ca2+ entry and Ca2+ extrusion systems. A class of cytosolic Ca2+-binding proteins termed Ca2+ buffers serves as modulators of such, mostly short-lived Ca2+ signals. Prototypical Ca2+ buffers include parvalbumins (α and β isoforms), calbindin-D9k, calbindin-D28k, and calretinin. Although initially considered to function as pure Ca2+ buffers, that is, as intracellular Ca2+ signal modulators controlling the shape (amplitude, decay, spread) of Ca2+ signals, evidence has accumulated that calbindin-D28k and calretinin have additional Ca2+ sensor functions. These other functions are brought about by direct interactions with target proteins, thereby modulating their targets' function/activity. Dysregulation of Ca2+ buffer expression is associated with several neurologic/neurodevelopmental disorders including autism spectrum disorder (ASD) and schizophrenia. In some cases, the presence of these proteins is presumed to confer a neuroprotective effect, as evidenced in animal models of Parkinson's or Alzheimer's disease.
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Affiliation(s)
- Beat Schwaller
- Department of Anatomy, Section of Medicine, University of Fribourg, CH-1700 Fribourg, Switzerland
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13
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Gilabert JA. Cytoplasmic Calcium Buffering: An Integrative Crosstalk. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:163-182. [PMID: 31646510 DOI: 10.1007/978-3-030-12457-1_7] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Calcium (Ca2+) buffering is part of an integrative crosstalk between different mechanisms and elements involved in the control of free Ca2+ ions persistence in the cytoplasm and hence, in the Ca2+-dependence of many intracellular processes. Alterations of Ca2+ homeostasis and signaling from systemic to subcellular levels also play a pivotal role in the pathogenesis of many diseases.Compared with Ca2+ sequestration towards intracellular Ca2+ stores, Ca2+ buffering is a rapid process occurring in a subsecond scale. Any molecule (or binding site) with the ability to bind Ca2+ ions could be considered, at least in principle, as a buffer. However, the term Ca2+ buffer is applied only to a small subset of Ca2+ binding proteins containing acidic side-chain residues.Ca2+ buffering in the cytoplasm mainly relies on mobile and immobile or fixed buffers controlling the diffusion of free Ca2+ ions inside the cytosol both temporally and spatially. Mobility of buffers depends on their molecular weight, but other parameters as their concentration, affinity for Ca2+ or Ca2+ binding and dissociation kinetics next to their diffusional mobility also contribute to make Ca2+ signaling one of the most complex signaling activities of the cell.The crosstalk between all the elements involved in the intracellular Ca2+ dynamics is a process of extreme complexity due to the diversity of structural and molecular elements involved but permit a highly regulated spatiotemporal control of the signal mediated by Ca2+ ions. The basis of modeling tools to study Ca2+ dynamics are also presented.
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Affiliation(s)
- Juan A Gilabert
- Department of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Complutense University of Madrid, Madrid, Spain.
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14
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Sánchez-Gómez L, Guerrero-Hernández A, Santillán M. Polymerization of sarcoplasmic-reticulum calcium-binding proteins might explain observed reticulum kinetics-on-demand behavior. J Theor Biol 2019; 482:109986. [PMID: 31465729 DOI: 10.1016/j.jtbi.2019.08.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 08/20/2019] [Accepted: 08/26/2019] [Indexed: 11/20/2022]
Abstract
Reported experimental results, in which transient elevations of sarcoplasmic calcium levels are induced by caffeine in smooth muscle cells, apparently contradict the principle of mass conservation. The commonly accepted model assumes that the total number of Ca2+ binding sites is fixed. A former work dealing with this problem proved that assuming the presence within the reticulum of calcium sequestering proteins whose total number of calcium binding sites increases as the existent sites get occupied, is enough to explain the above referred counter-intuitive experimental results. However, no chemical explanation was given to account for this binding-site count increase. In the present work, we propose a chemical-kinetics scheme for the binding of calcium to calsequestrin (a protein found within the reticulum) and the polymerization of this protein. On the one hand, this scheme is in agreement with reported results on calsequestrin binding kinetics, but it is also fully capable of explaining the observed intriguing performance of the sarcoplasmic reticulum. We further explore the behavior of the resulting nonlinear dynamic system and discuss possible physiological implications of the proposed scheme.
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Affiliation(s)
- Laura Sánchez-Gómez
- Centro de Investigación y de Estudios Avanzados del IPN, Unidad Monterrey, Vía del Conocimiento 201, Apodaca, NL 66600, México
| | - Agustín Guerrero-Hernández
- Centro de Investigación y de Estudios Avanzados del IPN, Unidad Zacatenco, Departamento de Bioquímica, Av. Instituto Politécnico Nacional 2508, Ciudad de México, 07000, México
| | - Moisés Santillán
- Centro de Investigación y de Estudios Avanzados del IPN, Unidad Monterrey, Vía del Conocimiento 201, Apodaca, NL 66600, México.
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15
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Rethinking calcium profiles around single channels: the exponential and periodic calcium nanodomains. Sci Rep 2019; 9:17196. [PMID: 31748584 PMCID: PMC6868209 DOI: 10.1038/s41598-019-53095-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 10/24/2019] [Indexed: 11/25/2022] Open
Abstract
Many fundamental calcium-dependent physiological processes are triggered by high local calcium levels that are established around the sites of calcium entry into the cell (channels). They are dubbed as calcium nanodomains but their exact profiles are still elusive. The concept of calcium nanodomains stems from a linear model of calcium diffusion and is only valid when calcium increases are smaller than the concentration of cytoplasmic buffers. Recent data indicates that much higher calcium levels cause buffer saturation. Therefore, I sought explicit solutions of a nonlinear reaction-diffusion model and found a dichotomous solution. For small fluxes, the steady state calcium profile is quasi-exponential, and when calcium exceeds buffer concentration a spatial periodicity appears. Analytical results are supported by Monte-Carlo simulations. I also imaged 1D- and radial calcium distributions around single α-synuclein channels in cell-free conditions. Measured Ca profiles are consistent with theoretical predictions. I propose that the periodic calcium patterns may well arise under certain conditions and their specific functional role has to be established.
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16
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Carbone E, Borges R, Eiden LE, García AG, Hernández‐Cruz A. Chromaffin Cells of the Adrenal Medulla: Physiology, Pharmacology, and Disease. Compr Physiol 2019; 9:1443-1502. [DOI: 10.1002/cphy.c190003] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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17
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Fang Q, Zhao Y, Lindau M. Precise Time Superresolution by Event Correlation Microscopy. Biophys J 2019; 116:1732-1747. [PMID: 31027888 DOI: 10.1016/j.bpj.2019.03.034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 03/19/2019] [Accepted: 03/21/2019] [Indexed: 10/27/2022] Open
Abstract
Fluorescence imaging is often used to monitor dynamic cellular functions under conditions of very low light intensities to avoid photodamage to the cell and rapid photobleaching. Determination of the time of a fluorescence change relative to a rapid high time-resolution event, such as an action potential or pulse stimulation, is challenged by the low photon rate and the need to use imaging frame durations that limit the time resolution. To overcome these limitations, we developed a time superresolution method named event correlation microscopy that aligns repetitive events with respect to the high time-resolution events. We describe the algorithm of the method, its step response function, and a theoretical, computational, and experimental analysis of its precision, providing guidelines for camera exposure time settings depending on imaging signal properties and camera parameters for optimal time resolution. We also demonstrate the utility of the method to recover rapid nonstepwise kinetics by deconvolution fits. The event correlation microscopy method provides time superresolution beyond the photon rate limit and imaging frame duration with well-defined precision.
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Affiliation(s)
- Qinghua Fang
- Laboratory for Nanoscale Cell Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Ying Zhao
- Laboratory for Nanoscale Cell Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Manfred Lindau
- Laboratory for Nanoscale Cell Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany; School of Applied and Engineering Physics, Cornell University, Ithaca, New York.
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18
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Catoni C, Calì T, Brini M. Calcium, Dopamine and Neuronal Calcium Sensor 1: Their Contribution to Parkinson's Disease. Front Mol Neurosci 2019; 12:55. [PMID: 30967759 PMCID: PMC6440390 DOI: 10.3389/fnmol.2019.00055] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 02/14/2019] [Indexed: 01/11/2023] Open
Abstract
Parkinson’s disease (PD) is a debilitating neurodegenerative disorder characterized by loss of dopaminergic neurons in the substantia nigra pars compacta. The causes of PD in humans are still unknown, although metabolic characteristics of the neurons affected by the disease have been implicated in their selective susceptibility. Mitochondrial dysfunction and proteostatic stress are recognized to be important in the pathogenesis of both familial and sporadic PD, and they both culminate in bioenergetic deficits. Exposure to calcium overload has recently emerged as a key determinant, and pharmacological treatment that inhibits Ca2+ entry diminishes neuronal damage in chemical models of PD. In this review, we first introduce general concepts on neuronal Ca2+ signaling and then summarize the current knowledge on fundamental properties of substantia nigra pars compacta dopaminergic neurons, on the role of the interplay between Ca2+ and dopamine signaling in neuronal activity and susceptibility to cell death. We also discuss the possible involvement of a “neglected” player, the Neuronal Calcium Sensor-1 (NCS-1), which has been shown to participate to dopaminergic signaling by regulating dopamine dependent receptor desensitization in normal brain but, data supporting a direct role in PD pathogenesis are still missing. However, it is intriguing to speculate that the Ca2+-dependent modulation of NCS-1 activity could eventually counteract dopaminergic neurons degeneration.
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Affiliation(s)
| | - Tito Calì
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Marisa Brini
- Department of Biology, University of Padova, Padua, Italy
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19
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Hennes A, Held K, Boretto M, De Clercq K, Van den Eynde C, Vanhie A, Van Ranst N, Benoit M, Luyten C, Peeraer K, Tomassetti C, Meuleman C, Voets T, Vankelecom H, Vriens J. Functional expression of the mechanosensitive PIEZO1 channel in primary endometrial epithelial cells and endometrial organoids. Sci Rep 2019; 9:1779. [PMID: 30741991 PMCID: PMC6370865 DOI: 10.1038/s41598-018-38376-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 12/20/2018] [Indexed: 12/27/2022] Open
Abstract
Successful pregnancy requires the establishment of a complex dialogue between the implanting embryo and the endometrium. Knowledge regarding molecular candidates involved in this early communication process is inadequate due to limited access to primary human endometrial epithelial cells (EEC). Since pseudo-pregnancy in rodents can be induced by mechanical scratching of an appropriately primed uterus, this study aimed to investigate the expression of mechanosensitive ion channels in EEC. Poking of EEC provoked a robust calcium influx and induced an increase in current densities, which could be blocked by an inhibitor of mechanosensitive ion channels. Interestingly, RNA expression studies showed high expression of PIEZO1 in EEC of mouse and human. Additional analysis provided further evidence for the functional expression of PIEZO1 since stimulation with Yoda1, a chemical agonist of PIEZO1, induced increases in intracellular calcium concentrations and current densities in EEC. Moreover, the ion channel profile of human endometrial organoids (EMO) was validated as a representative model for endometrial epithelial cells. Mechanical and chemical stimulation of EMO induced strong calcium responses supporting the hypothesis of mechanosensitive ion channel expression in endometrial epithelial cells. In conclusion, EEC and EMO functionally express the mechanosensitive PIEZO1 channel that could act as a potential target for the development of novel treatments to further improve successful implantation processes.
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Affiliation(s)
- Aurélie Hennes
- Laboratory of Endometrium, Endometriosis & Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 611, 3000, Leuven, Belgium
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49 box 802, 3000, Leuven, Belgium
| | - Katharina Held
- Laboratory of Endometrium, Endometriosis & Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 611, 3000, Leuven, Belgium
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49 box 802, 3000, Leuven, Belgium
| | - Matteo Boretto
- Laboratory of Tissue Plasticity in Health and Disease, Cluster of Stem Cell and Developmental Biology, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 804, 3000, Leuven, Belgium
| | - Katrien De Clercq
- Laboratory of Endometrium, Endometriosis & Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 611, 3000, Leuven, Belgium
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49 box 802, 3000, Leuven, Belgium
| | - Charlotte Van den Eynde
- Laboratory of Endometrium, Endometriosis & Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 611, 3000, Leuven, Belgium
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49 box 802, 3000, Leuven, Belgium
| | - Arne Vanhie
- Laboratory of Endometrium, Endometriosis & Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 611, 3000, Leuven, Belgium
- Leuven University Fertility Centre, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Nele Van Ranst
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49 box 802, 3000, Leuven, Belgium
| | - Melissa Benoit
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49 box 802, 3000, Leuven, Belgium
| | - Catherine Luyten
- Laboratory of Endometrium, Endometriosis & Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 611, 3000, Leuven, Belgium
| | - Karen Peeraer
- Laboratory of Endometrium, Endometriosis & Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 611, 3000, Leuven, Belgium
- Leuven University Fertility Centre, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Carla Tomassetti
- Laboratory of Endometrium, Endometriosis & Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 611, 3000, Leuven, Belgium
- Leuven University Fertility Centre, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Christel Meuleman
- Laboratory of Endometrium, Endometriosis & Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 611, 3000, Leuven, Belgium
- Leuven University Fertility Centre, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Thomas Voets
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Herestraat 49 box 802, 3000, Leuven, Belgium
| | - Hugo Vankelecom
- Laboratory of Tissue Plasticity in Health and Disease, Cluster of Stem Cell and Developmental Biology, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 804, 3000, Leuven, Belgium
| | - Joris Vriens
- Laboratory of Endometrium, Endometriosis & Reproductive Medicine, Department of Development and Regeneration, KU Leuven, Herestraat 49 box 611, 3000, Leuven, Belgium.
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20
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Gq-Coupled Muscarinic Receptor Enhancement of KCNQ2/3 Channels and Activation of TRPC Channels in Multimodal Control of Excitability in Dentate Gyrus Granule Cells. J Neurosci 2018; 39:1566-1587. [PMID: 30593498 DOI: 10.1523/jneurosci.1781-18.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 12/17/2018] [Accepted: 12/20/2018] [Indexed: 12/21/2022] Open
Abstract
KCNQ (Kv7, "M-type") K+ channels and TRPC (transient receptor potential, "canonical") cation channels are coupled to neuronal discharge properties and are regulated via Gq/11-protein-mediated signals. Stimulation of Gq/11-coupled receptors both consumes phosphatidylinositol 4,5-bisphosphate (PIP2) via phosphalipase Cβ hydrolysis and stimulates PIP2 synthesis via rises in Ca2+ i and other signals. Using brain-slice electrophysiology and Ca2+ imaging from male and female mice, we characterized threshold K+ currents in dentate gyrus granule cells (DGGCs) and CA1 pyramidal cells, the effects of Gq/11-coupled muscarinic M1 acetylcholine (M1R) stimulation on M current and on neuronal discharge properties, and elucidated the intracellular signaling mechanisms involved. We observed disparate signaling cascades between DGGCs and CA1 neurons. DGGCs displayed M1R enhancement of M-current, rather than suppression, due to stimulation of PIP2 synthesis, which was paralleled by increased PIP2-gated G-protein coupled inwardly rectifying K+ currents as well. Deficiency of KCNQ2-containing M-channels ablated the M1R-induced enhancement of M-current in DGGCs. Simultaneously, M1R stimulation in DGGCs induced robust increases in [Ca2+]i, mostly due to TRPC currents, consistent with, and contributing to, neuronal depolarization and hyperexcitability. CA1 neurons did not display such multimodal signaling, but rather M current was suppressed by M1R stimulation in these cells, similar to the previously described actions of M1R stimulation on M-current in peripheral ganglia that mostly involves PIP2 depletion. Therefore, these results point to a pleiotropic network of cholinergic signals that direct cell-type-specific, precise control of hippocampal function with strong implications for hyperexcitability and epilepsy.SIGNIFICANCE STATEMENT At the neuronal membrane, protein signaling cascades consisting of ion channels and metabotropic receptors govern the electrical properties and neurotransmission of neuronal networks. Muscarinic acetylcholine receptors are G-protein-coupled metabotropic receptors that control the excitability of neurons through regulating ion channels, intracellular Ca2+ signals, and other second-messenger cascades. We have illuminated previously unknown actions of muscarinic stimulation on the excitability of hippocampal principal neurons that include M channels, TRPC (transient receptor potential, "canonical") cation channels, and powerful regulation of lipid metabolism. Our results show that these signaling pathways, and mechanisms of excitability, are starkly distinct between peripheral ganglia and brain, and even between different principal neurons in the hippocampus.
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21
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Caffeine chelates calcium in the lumen of the endoplasmic reticulum. Biochem J 2018; 475:3639-3649. [PMID: 30389846 DOI: 10.1042/bcj20180532] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 10/14/2018] [Accepted: 11/01/2018] [Indexed: 12/29/2022]
Abstract
Cytosolic Ca2+ signals are often amplified by massive calcium release from the endoplasmic reticulum (ER). This calcium-induced calcium release (CICR) occurs by activation of an ER Ca2+ channel, the ryanodine receptor (RyR), which is facilitated by both cytosolic- and ER Ca2+ levels. Caffeine sensitizes RyR to Ca2+ and promotes ER Ca2+ release at basal cytosolic Ca2+ levels. This outcome is frequently used as a readout for the presence of CICR. By monitoring ER luminal Ca2+ with the low-affinity genetic Ca2+ probe erGAP3, we find here that application of 50 mM caffeine rapidly reduces the Ca2+ content of the ER in HeLa cells by ∼50%. Interestingly, this apparent ER Ca2+ release does not go along with the expected cytosolic Ca2+ increase. These results can be explained by Ca2+ chelation by caffeine inside the ER. Ca2+-overloaded mitochondria also display a drop of the matrix Ca2+ concentration upon caffeine addition. In contrast, in the cytosol, with a low free Ca2+ concentration (10-7 M), no chelation is observed. Expression of RyR3 sensitizes the responses to caffeine with effects both in the ER (increase in Ca2+ release) and in the cytosol (increase in Ca2+ peak) at low caffeine concentrations (0.3-1 mM) that have no effects in control cells. Our results illustrate the fact that simultaneous monitoring of both cytosolic- and ER Ca2+ are necessary to understand the action of caffeine and raise concerns against the use of high concentrations of caffeine as a readout of the presence of CICR.
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22
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Fettiplace R, Nam JH. Tonotopy in calcium homeostasis and vulnerability of cochlear hair cells. Hear Res 2018; 376:11-21. [PMID: 30473131 DOI: 10.1016/j.heares.2018.11.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 11/05/2018] [Accepted: 11/08/2018] [Indexed: 12/18/2022]
Abstract
Ototoxicity, noise overstimulation, or aging, can all produce hearing loss with similar properties, in which outer hair cells (OHCs), principally those at the high-frequency base of the cochlea, are preferentially affected. We suggest that the differential vulnerability may partly arise from differences in Ca2+ balance among cochlear locations. Homeostasis is determined by three factors: Ca2+ influx mainly via mechanotransducer (MET) channels; buffering by calcium-binding proteins and organelles like mitochondria; and extrusion by the plasma membrane CaATPase pump. We review quantification of these parameters and use our experimentally-determined values to model changes in cytoplasmic and mitochondrial Ca2+ during Ca2+ influx through the MET channels. We suggest that, in OHCs, there are two distinct micro-compartments for Ca2+ handling, one in the hair bundle and the other in the cell soma. One conclusion of the modeling is that there is a tonotopic gradient in the ability of OHCs to handle the Ca2+ load, which correlates with their vulnerability to environmental challenges. High-frequency basal OHCs are the most susceptible because they have much larger MET currents and have smaller dimensions than low-frequency apical OHCs.
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Affiliation(s)
- Robert Fettiplace
- Department of Neuroscience, University of Wisconsin, Madison, WI, 53706, USA.
| | - Jong-Hoon Nam
- Departments of Mechanical Engineering and Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
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23
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McMahon SM, Jackson MB. An Inconvenient Truth: Calcium Sensors Are Calcium Buffers. Trends Neurosci 2018; 41:880-884. [PMID: 30287084 DOI: 10.1016/j.tins.2018.09.005] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 08/28/2018] [Accepted: 09/11/2018] [Indexed: 12/13/2022]
Abstract
Recent advances in Ca2+ imaging have given neuroscientists a tool to follow the activity of large numbers of individual neurons simultaneously in vivo in the brains of animals as they are presented with sensory stimulation, respond to environmental challenges, and engage in behaviors. The Ca2+ sensors used to transduce changes in cellular Ca2+ into changes in fluorescence must bind Ca2+ to produce a signal. By binding Ca2+, these sensors can act as buffers, often reducing the magnitude of a Ca2+ change severalfold, and producing a proportional slowing of the rates of change. Ca2+ probes can thus distort the patterns of activity they are intended to study and modify ongoing Ca2+ signaling functions. Recognizing these factors will enhance the use of in vivo Ca2+ imaging in the investigation of neural circuit function.
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Affiliation(s)
- Shane M McMahon
- Department of Neuroscience, University of Wisconsin, Madison, WI, USA
| | - Meyer B Jackson
- Department of Neuroscience, University of Wisconsin, Madison, WI, USA.
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24
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Hughes JW, Ustione A, Lavagnino Z, Piston DW. Regulation of islet glucagon secretion: Beyond calcium. Diabetes Obes Metab 2018; 20 Suppl 2:127-136. [PMID: 30230183 PMCID: PMC6148361 DOI: 10.1111/dom.13381] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 05/03/2018] [Accepted: 05/23/2018] [Indexed: 12/19/2022]
Abstract
The islet of Langerhans plays a key role in glucose homeostasis through regulated secretion of the hormones insulin and glucagon. Islet research has focused on the insulin-secreting β-cells, even though aberrant glucagon secretion from α-cells also contributes to the aetiology of diabetes. Despite its importance, the mechanisms controlling glucagon secretion remain controversial. Proper α-cell function requires the islet milieu, where β- and δ-cells drive and constrain α-cell dynamics. The response of glucagon to glucose is similar between isolated islets and that measured in vivo, so it appears that the glucose dependence requires only islet-intrinsic factors and not input from blood flow or the nervous system. Elevated intracellular free Ca2+ is needed for α-cell exocytosis, but interpreting Ca2+ data is tricky since it is heterogeneous among α-cells at all physiological glucose levels. Total Ca2+ activity in α-cells increases slightly with glucose, so Ca2+ may serve a permissive, rather than regulatory, role in glucagon secretion. On the other hand, cAMP is a more promising candidate for controlling glucagon secretion and is itself driven by paracrine signalling from β- and δ-cells. Another pathway, juxtacrine signalling through the α-cell EphA receptors, stimulated by β-cell ephrin ligands, leads to a tonic inhibition of glucagon secretion. We discuss potential combinations of Ca2+ , cAMP, paracrine and juxtacrine factors in the regulation of glucagon secretion, focusing on recent data in the literature that might unify the field towards a quantitative understanding of α-cell function.
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Affiliation(s)
- Jing W. Hughes
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Alessandro Ustione
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
| | - Zeno Lavagnino
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
| | - David W. Piston
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
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25
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Tran V, Stricker C. Diffusion of Ca 2+ from Small Boutons en Passant into the Axon Shapes AP-Evoked Ca 2+ Transients. Biophys J 2018; 115:1344-1356. [PMID: 30103908 DOI: 10.1016/j.bpj.2018.07.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 07/01/2018] [Accepted: 07/16/2018] [Indexed: 01/16/2023] Open
Abstract
Not only the amplitude but also the time course of a presynaptic Ca2+ transient determine multiple aspects of synaptic transmission. In small bouton-type synapses, the mechanisms underlying the Ca2+ decay kinetics have not been fully investigated. Here, factors that shape an action-potential-evoked Ca2+ transient were quantitatively studied in synaptic boutons of neocortical layer 5 pyramidal neurons. Ca2+ transients were measured with different concentrations of fluorescent Ca2+ indicators and analyzed based on a single-compartment model. We found a small endogenous Ca2+-binding ratio (7 ± 2) and a high activity of Ca2+ transporters (0.64 ± 0.03 ms-1), both of which enable rapid clearance of Ca2+ from the boutons. However, contrary to predictions of the single-compartment model, the decay time course of the measured Ca2+ transients was biexponential and became prolonged during repetitive stimulation. Measurements of [Ca2+]i along the adjoining axon, together with an experimentally constrained model, showed that the initial fast decay of the Ca2+ transients predominantly arose from the diffusion of Ca2+ from the boutons into the axon. Therefore, for small boutons en passant, factors like terminal volume, axon diameter, and the concentration of mobile Ca2+-binding molecules are critical determinants of Ca2+ dynamics and thus Ca2+-dependent processes, including short-term synaptic plasticity.
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Affiliation(s)
- Van Tran
- Eccles Institute of Neuroscience, JCSMR.
| | - Christian Stricker
- Eccles Institute of Neuroscience, JCSMR; ANU Medical School, ANU, Acton, Australian Capital Territory, Australia
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26
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Hydrogen sulphide facilitates exocytosis by regulating the handling of intracellular calcium by chromaffin cells. Pflugers Arch 2018; 470:1255-1270. [DOI: 10.1007/s00424-018-2147-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 04/10/2018] [Accepted: 04/17/2018] [Indexed: 01/09/2023]
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27
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An improved measurement of the Ca2+-binding affinity of fluorescent Ca2+ indicators. Cell Calcium 2018; 71:86-94. [DOI: 10.1016/j.ceca.2018.01.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 12/11/2017] [Accepted: 01/07/2018] [Indexed: 01/18/2023]
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28
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Boonen B, Alpizar YA, Sanchez A, López-Requena A, Voets T, Talavera K. Differential effects of lipopolysaccharide on mouse sensory TRP channels. Cell Calcium 2018; 73:72-81. [PMID: 29689522 DOI: 10.1016/j.ceca.2018.04.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 03/24/2018] [Accepted: 04/10/2018] [Indexed: 12/24/2022]
Abstract
Acute neurogenic inflammation and pain associated to bacterial infection have been traditionally ascribed to sensitization and activation of sensory nerve afferents secondary to immune cell stimulation. However, we recently showed that lipopolysaccharides (LPS) directly activate the Transient Receptor Potential channels TRPA1 in sensory neurons and TRPV4 in airway epithelial cells. Here we investigated whether LPS activates other sensory TRP channels expressed in sensory neurons. Using intracellular Ca2+ imaging and patch-clamp we determined the effects of LPS on recombinant TRPV1, TRPV2, TRPM3 and TRPM8, heterologously expressed in HEK293T cells. We found that LPS activates TRPV1, although with lower potency than for TRPA1. Activation of TRPV1 by LPS was not affected by mutations of residues required for activation by electrophilic agents or by diacylglycerol and capsaicin. On the other hand, LPS weakly activated TRPM3, activated TRPM8 at 25 °C, but not at 35 °C, and was ineffective on TRPV2. Experiments performed in mouse dorsal root ganglion (DRG) neurons revealed that genetic ablation of Trpa1 did not abolish the responses to LPS, but remain detected in 30% of capsaicin-sensitive cells. The population of neurons responding to LPS was dramatically lower in double Trpa1/Trpv1 KO neurons. Our results show that, in addition to TRPA1, other TRP channels in sensory neurons can be targets of LPS, suggesting that they may contribute to trigger and regulate innate defenses against gram-negative bacterial infections.
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Affiliation(s)
- Brett Boonen
- Laboratory for Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, O&N1 Herestraat 49 - box 802, 3000, Leuven, Belgium
| | - Yeranddy A Alpizar
- Laboratory for Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, O&N1 Herestraat 49 - box 802, 3000, Leuven, Belgium
| | - Alicia Sanchez
- Laboratory for Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, O&N1 Herestraat 49 - box 802, 3000, Leuven, Belgium
| | - Alejandro López-Requena
- Laboratory for Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, O&N1 Herestraat 49 - box 802, 3000, Leuven, Belgium
| | - Thomas Voets
- Laboratory for Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, O&N1 Herestraat 49 - box 802, 3000, Leuven, Belgium
| | - Karel Talavera
- Laboratory for Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, O&N1 Herestraat 49 - box 802, 3000, Leuven, Belgium.
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29
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Abstract
Calcium signals control a plethora of essential cellular functions ranging from secretion and contraction to gene expression and sensory signaling cascades. An essential part of intracellular calcium signals originates from the transmembrane flux of calcium ions, which is mainly mediated through different calcium-permeable cation channels with variable calcium selectivity. Opening of individual calcium permeable channels induces a local cytosolic calcium rise that can be highly restricted in time and space. Here, we provide a short overview of the current knowledge about calcium permeation and localized calcium signals in transient receptor potential (TRP) channels. We also present a brief survey of some fundamental theoretical aspects of the local calcium signals generated upon opening of single calcium-permeable channels, and compare theoretical predictions with published experimental data on TRP channel-mediated local calcium signals.
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30
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Lin KH, Taschenberger H, Neher E. Dynamics of volume-averaged intracellular Ca 2+ in a rat CNS nerve terminal during single and repetitive voltage-clamp depolarizations. J Physiol 2017; 595:3219-3236. [PMID: 27957749 DOI: 10.1113/jp272773] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 11/28/2016] [Indexed: 12/28/2022] Open
Abstract
KEY POINTS The intracellular concentration of free calcium ions ([Ca2+ ]i ) in a nerve terminal controls both transmitter release and synaptic plasticity. The rapid triggering of transmitter release depends on the local micro- or nanodomain of highly elevated [Ca2+ ]i in the vicinity of open voltage-gated Ca2+ channels, whereas short-term synaptic plasticity is often controlled by global changes in residual [Ca2+ ]i , averaged over the whole nerve terminal volume. Here we describe dynamic changes of such global [Ca2+ ]i in the calyx of Held - a giant mammalian glutamatergic nerve terminal, which is particularly suited for biophysical studies. We provide quantitative data on Ca2+ inflow, Ca2+ buffering and Ca2+ clearance. These data allow us to predict changes in [Ca2+ ]i in the nerve terminal in response to a wide range of stimulus protocols at high temporal resolution and provide a basis for the modelling of short-term plasticity of glutamatergic synapses. ABSTRACT Many aspects of short-term synaptic plasticity (STP) are controlled by relatively slow changes in the presynaptic intracellular concentration of free calcium ions ([Ca2+ ]i ) that occur in the time range of a few milliseconds to several seconds. In nerve terminals, [Ca2+ ]i equilibrates diffusionally during such slow changes, such that the globally measured, residual [Ca2+ ]i that persists after the collapse of local domains is often the appropriate parameter governing STP. Here, we study activity-dependent dynamic changes in global [Ca2+ ]i at the rat calyx of Held nerve terminal in acute brainstem slices using patch-clamp and microfluorimetry. We use low concentrations of a low-affinity Ca2+ indicator dye (100 μm Fura-6F) in order not to overwhelm endogenous Ca2+ buffers. We first study voltage-clamped terminals, dialysed with pipette solutions containing minimal amounts of Ca2+ buffers, to determine Ca2+ binding properties of endogenous fixed buffers as well as the mechanisms of Ca2+ clearance. Subsequently, we use pipette solutions including 500 μm EGTA to determine the Ca2+ binding kinetics of this chelator. We provide a formalism and parameters that allow us to predict [Ca2+ ]i changes in calyx nerve terminals in response to a wide range of stimulus protocols. Unexpectedly, the Ca2+ affinity of EGTA under the conditions of our measurements was substantially lower (KD = 543 ± 51 nm) than measured in vitro, mainly as a consequence of a higher than previously assumed dissociation rate constant (2.38 ± 0.20 s-1 ), which we need to postulate in order to model the measured presynaptic [Ca2+ ]i transients.
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Affiliation(s)
- Kun-Han Lin
- Emeritus Group Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | - Holger Taschenberger
- Emeritus Group Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany.,Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany.,DFG-Research Centre for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37073, Göttingen, Germany
| | - Erwin Neher
- Emeritus Group Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany.,DFG-Research Centre for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37073, Göttingen, Germany
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31
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Kim IA, Taylor ZD, Cheng H, Sebastian C, Maccabi A, Garritano J, Tajudeen B, Razfar A, Palma Diaz F, Yeh M, Stafsudd O, Grundfest W, St. John M. Dynamic Optical Contrast Imaging: A Technique to Differentiate Parathyroid Tissue from Surrounding Tissues. Otolaryngol Head Neck Surg 2017; 156:480-483. [DOI: 10.1177/0194599816686294] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The variable location and indistinct features of parathyroid glands can make their intraoperative identification challenging. Currently, there exists no routine use of localization methods during surgery. Dynamic optical contrast imaging (DOCI) leverages a novel realization of temporally dependent measurements of tissue autofluorescence that allows the acquisition of specific tissue properties. A prospective series of patients with primary hyperparathyroidism was examined. Parathyroid lesions and surrounding tissues were collected; fluorescence decay images were acquired via DOCI. Ex vivo samples (81 patients) were processed for histologic assessment. DOCI extracts relative fluorescence decay information in a surgically relevant field of view with a clinically accessible acquisition time <2 minutes. Analysis of DOCI revealed microscopic characterization sufficient for tissue type identification consistent with histology ( P < .05). DOCI is capable of efficiently distinguishing parathyroid tissue from adjacent tissues. Such an intraoperative tool would be transformative, helping surgeons to identify lesions, preserve healthy tissue, and improve patient outcomes.
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Affiliation(s)
- Irene A. Kim
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
- Head and Neck Cancer Program, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
| | - Zachary D. Taylor
- Head and Neck Cancer Program, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California–Los Angeles, Los Angeles, California, USA
- Department of Surgery, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
| | - Harrison Cheng
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California–Los Angeles, Los Angeles, California, USA
| | - Christine Sebastian
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
- Head and Neck Cancer Program, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
| | - Ashkan Maccabi
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California–Los Angeles, Los Angeles, California, USA
| | - James Garritano
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California–Los Angeles, Los Angeles, California, USA
| | - Bobby Tajudeen
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
- Head and Neck Cancer Program, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
| | - Ali Razfar
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
- Head and Neck Cancer Program, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
| | - Fernando Palma Diaz
- Department of Pathology, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
| | - Michael Yeh
- Department of Surgery, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
| | - Oscar Stafsudd
- Department of Electrical Engineering, Henry Samueli School of Engineering and Applied Sciences, University of California–Los Angeles, Los Angeles, California, USA
| | - Warren Grundfest
- Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California–Los Angeles, Los Angeles, California, USA
- Department of Surgery, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
- Department of Electrical Engineering, Henry Samueli School of Engineering and Applied Sciences, University of California–Los Angeles, Los Angeles, California, USA
| | - Maie St. John
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
- Head and Neck Cancer Program, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
- Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California–Los Angeles, Los Angeles, California, USA
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32
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Shang S, Zhu F, Liu B, Chai Z, Wu Q, Hu M, Wang Y, Huang R, Zhang X, Wu X, Sun L, Wang Y, Wang L, Xu H, Teng S, Liu B, Zheng L, Zhang C, Zhang F, Feng X, Zhu D, Wang C, Liu T, Zhu MX, Zhou Z. Intracellular TRPA1 mediates Ca2+ release from lysosomes in dorsal root ganglion neurons. J Cell Biol 2016; 215:369-381. [PMID: 27799370 PMCID: PMC5100290 DOI: 10.1083/jcb.201603081] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 08/16/2016] [Accepted: 10/04/2016] [Indexed: 11/22/2022] Open
Abstract
Transient receptor potential A1 (TRPA1) is a nonselective cation channel implicated in thermosensation and inflammatory pain. In this study, we show that TRPA1 (activated by allyl isothiocyanate, acrolein, and 4-hydroxynonenal) elevates the intracellular Ca2+ concentration ([Ca2+]i) in dorsal root ganglion (DRG) neurons in the presence and absence of extracellular Ca2+ Pharmacological and immunocytochemical analyses revealed the presence of TRPA1 channels both on the plasma membrane and in endolysosomes. Confocal line-scan imaging demonstrated Ca2+ signals elicited from individual endolysosomes ("lysosome Ca2+ sparks") by TRPA1 activation. In physiological solutions, the TRPA1-mediated endolysosomal Ca2+ release contributed to ∼40% of the overall [Ca2+]i rise and directly triggered vesicle exocytosis and calcitonin gene-related peptide release, which greatly enhanced the excitability of DRG neurons. Thus, in addition to working via Ca2+ influx, TRPA1 channels trigger vesicle release in sensory neurons by releasing Ca2+ from lysosome-like organelles.
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Affiliation(s)
- Shujiang Shang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China.,Laboratory Animal Center, Peking University, Beijing 100871, China.,School of Life Science, Peking University, Beijing 100871, China
| | - Feipeng Zhu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Bin Liu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Zuying Chai
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Qihui Wu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Meiqin Hu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Yuan Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Rong Huang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Xiaoyu Zhang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Xi Wu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Lei Sun
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Yeshi Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Li Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Huadong Xu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Sasa Teng
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Bing Liu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Lianghong Zheng
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Chen Zhang
- School of Life Science, Peking University, Beijing 100871, China
| | - Fukang Zhang
- Institute for Biomedical Science of Pain, Capital Medical University, Beijing 100069, China
| | - Xinghua Feng
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Desheng Zhu
- Laboratory Animal Center, Peking University, Beijing 100871, China
| | - Changhe Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Tao Liu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Michael X Zhu
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Zhuan Zhou
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
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33
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Ullah G, Ullah A. Mode switching of Inositol 1,4,5-trisphosphate receptor channel shapes the Spatiotemporal scales of Ca 2+ signals. J Biol Phys 2016; 42:507-524. [PMID: 27154029 PMCID: PMC5059592 DOI: 10.1007/s10867-016-9419-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 04/12/2016] [Indexed: 01/24/2023] Open
Abstract
The inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) channel is crucial for the generation and modulation of highly specific intracellular Ca2+ signals performing numerous functions in animal cells. However, the single channel behavior during Ca2+ signals of different spatiotemporal scales is not well understood. To elucidate the correlation between the gating dynamics of single InsP3Rs and spatiotemporal Ca2+ patterns, we simulate a cluster of InsP3Rs under varying ligand concentrations and extract comprehensive gating statistics of all channels during events of different sizes and durations. Our results show that channels gating predominantly in the low activity mode with negligible occupancy of intermediate and high modes leads to single channel Ca2+ release event blips. Increasing occupancies of intermediate and high modes results in events with increasing size. When the channel has more than 50% probability of gating in the intermediate and high modes, the cluster generates very large puffs that would most likely result in global Ca2+ signals. The size, duration and frequency of Ca2+ signals all increase linearly with the total probability of channel gating in the intermediate and high modes. To our knowledge, this is the first study that quantitatively relates the modal characteristics of InsP3R to the shaping of different spatiotemporal scales of Ca2+ signals.
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Affiliation(s)
- Ghanim Ullah
- Department of Physics, University of South Florida, Tampa, FL, 33620, USA.
| | - Aman Ullah
- Department of Molecular Neuroscience, Krasnow Institute for Advanced Study, George Mason University, Fairfax, VA, 22030, USA
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34
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Mondragão MA, Schmidt H, Kleinhans C, Langer J, Kafitz KW, Rose CR. Extrusion versus diffusion: mechanisms for recovery from sodium loads in mouse CA1 pyramidal neurons. J Physiol 2016; 594:5507-27. [PMID: 27080107 PMCID: PMC5043027 DOI: 10.1113/jp272431] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 04/07/2016] [Indexed: 12/20/2022] Open
Abstract
KEY POINTS Neuronal activity causes local or global sodium signalling in neurons, depending on the pattern of synaptic activity. Recovery from global sodium loads critically relies on Na(+) /K(+) -ATPase and an intact energy metabolism in both somata and dendrites. For recovery from local sodium loads in dendrites, Na(+) /K(+) -ATPase activity is not required per se. Instead, recovery is predominately mediated by lateral diffusion, exhibiting rates that are 10-fold higher than for global sodium signals. Recovery from local dendritic sodium increases is still efficient during short periods of energy deprivation, indicating that fast diffusion of sodium to non-stimulated regions strongly reduces local energy requirements. ABSTRACT Excitatory activity is accompanied by sodium influx into neurones as a result of the opening of voltage- and ligand-activated channels. Recovery from resulting sodium transients has mainly been attributed to Na(+) /K(+) -ATPase (NKA). Because sodium ions are highly mobile, diffusion could provide an additional pathway. We tested this in hippocampal neurones using whole-cell patch-clamp recordings and sodium imaging. Somatic sodium transients induced by local glutamate application recovered at a maximum rate of 8 mm min(-1) (∼0.03 mm min(-1 ) μm(-2) ). Somatic sodium extrusion was accelerated at higher temperature and blocked by ouabain, emphasizing its dependence on NKA. Moreover, it was slowed down during inhibition of glycolysis by sodium fluoride (NaF). Local glutamate application to dendrites revealed a 10-fold higher apparent dendritic sodium extrusion rate compared to somata. Recovery was almost unaltered by increased temperature, ouabain or NaF. We found that sodium diffused along primary dendrites with a diffusion coefficient of ∼330 μm²/s. During global glutamate application, impeding substantial net diffusion, apparent dendritic extrusion rates were reduced to somatic rates and also affected by NaF. Numerical simulations confirmed the essential role of NKA for the recovery of somatic, but not dendritic sodium loads. Our data show that sodium export upon global sodium increases is largely mediated by NKA and depends on an intact energy metabolism. For recovery from local dendritic sodium increases, diffusion dominates over extrusion, operating efficiently even during short periods of energy deprivation. Although sodium will eventually be extruded by the NKA, its diffusion-based fast dissemination to non-stimulated regions might reduce local energy requirements.
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Affiliation(s)
- Miguel A Mondragão
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Hartmut Schmidt
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Christian Kleinhans
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Julia Langer
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Karl W Kafitz
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
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Sun W, Matthews EA, Nicolas V, Schoch S, Dietrich D. NG2 glial cells integrate synaptic input in global and dendritic calcium signals. eLife 2016; 5. [PMID: 27644104 PMCID: PMC5052029 DOI: 10.7554/elife.16262] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 09/17/2016] [Indexed: 12/30/2022] Open
Abstract
Synaptic signaling to NG2-expressing oligodendrocyte precursor cells (NG2 cells) could be key to rendering myelination of axons dependent on neuronal activity, but it has remained unclear whether NG2 glial cells integrate and respond to synaptic input. Here we show that NG2 cells perform linear integration of glutamatergic synaptic inputs and respond with increasing dendritic calcium elevations. Synaptic activity induces rapid Ca2+ signals mediated by low-voltage activated Ca2+ channels under strict inhibitory control of voltage-gated A-type K+ channels. Ca2+ signals can be global and originate throughout the cell. However, voltage-gated channels are also found in thin dendrites which act as compartmentalized processing units and generate local calcium transients. Taken together, the activity-dependent control of Ca2+ signals by A-type channels and the global versus local signaling domains make intracellular Ca2+ in NG2 cells a prime signaling molecule to transform neurotransmitter release into activity-dependent myelination. DOI:http://dx.doi.org/10.7554/eLife.16262.001
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Affiliation(s)
- Wenjing Sun
- Department of Neurosurgery, University Clinic Bonn, Bonn, Germany
| | | | - Vicky Nicolas
- Department of Neurosurgery, University Clinic Bonn, Bonn, Germany
| | - Susanne Schoch
- Department of Neuropathology, University Clinic Bonn, Bonn, Germany
| | - Dirk Dietrich
- Department of Neurosurgery, University Clinic Bonn, Bonn, Germany
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36
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Maccari I, Zhao R, Peglow M, Schwarz K, Hornak I, Pasche M, Quintana A, Hoth M, Qu B, Rieger H. Cytoskeleton rotation relocates mitochondria to the immunological synapse and increases calcium signals. Cell Calcium 2016; 60:309-321. [PMID: 27451384 DOI: 10.1016/j.ceca.2016.06.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 06/24/2016] [Accepted: 06/24/2016] [Indexed: 11/18/2022]
Abstract
Ca2+ microdomains and spatially resolved Ca2+ signals are highly relevant for cell function. In T cells, local Ca2+ signaling at the immunological synapse (IS) is required for downstream effector functions. We present experimental evidence that the relocation of the MTOC towards the IS during polarization drags mitochondria along with the microtubule network. From time-lapse fluorescence microscopy we conclude that mitochondria rotate together with the cytoskeleton towards the IS. We hypothesize that this movement of mitochondria towards the IS together with their functionality of absorption and spatial redistribution of Ca2+ is sufficient to significantly increase the cytosolic Ca2+ concentration. To test this hypothesis we developed a whole cell model for Ca2+ homoeostasis involving specific geometries for mitochondria and use the model to calculate the spatial distribution of Ca2+ concentrations within the cell body as a function of the rotation angle and the distance from the IS. We find that an inhomogeneous distribution of PMCA pumps on the cell membrane, in particular an accumulation of PMCA at the IS, increases the global Ca2+ concentration and decreases the local Ca2+ concentration at the IS with decreasing distance of the MTOC from the IS. Unexpectedly, a change of CRAC/Orai activity is not required to explain the observed Ca2+ changes. We conclude that rotation-driven relocation of the MTOC towards the IS together with an accumulation of PMCA pumps at the IS are sufficient to control the observed Ca2+ dynamics in T-cells during polarization.
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Affiliation(s)
- Ilaria Maccari
- Theoretical Physics, Saarland University, 66041 Saarbrücken, Germany
| | - Renping Zhao
- Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, 66421 Homburg, Germany
| | - Martin Peglow
- Theoretical Physics, Saarland University, 66041 Saarbrücken, Germany
| | - Karsten Schwarz
- Theoretical Physics, Saarland University, 66041 Saarbrücken, Germany
| | - Ivan Hornak
- Theoretical Physics, Saarland University, 66041 Saarbrücken, Germany
| | - Mathias Pasche
- Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, 66421 Homburg, Germany
| | - Ariel Quintana
- Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, 66421 Homburg, Germany
| | - Markus Hoth
- Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, 66421 Homburg, Germany.
| | - Bin Qu
- Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, 66421 Homburg, Germany
| | - Heiko Rieger
- Theoretical Physics, Saarland University, 66041 Saarbrücken, Germany.
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37
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DeCaen PG, Liu X, Abiria S, Clapham DE. Atypical calcium regulation of the PKD2-L1 polycystin ion channel. eLife 2016; 5. [PMID: 27348301 PMCID: PMC4922860 DOI: 10.7554/elife.13413] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 05/12/2016] [Indexed: 11/13/2022] Open
Abstract
Native PKD2-L1 channel subunits are present in primary cilia and other restricted cellular spaces. Here we investigate the mechanism for the channel's unusual regulation by external calcium, and rationalize this behavior to its specialized function. We report that the human PKD2-L1 selectivity filter is partially selective to calcium ions (Ca(2+)) moving into the cell, but blocked by high internal Ca(2+)concentrations, a unique feature of this transient receptor potential (TRP) channel family member. Surprisingly, we find that the C-terminal EF-hands and coiled-coil domains do not contribute to PKD2-L1 Ca(2+)-induced potentiation and inactivation. We propose a model in which prolonged channel activity results in calcium accumulation, triggering outward-moving Ca(2+) ions to block PKD2-L1 in a high-affinity interaction with the innermost acidic residue (D523) of the selectivity filter and subsequent long-term channel inactivation. This response rectifies Ca(2+) flow, enabling Ca(2+) to enter but not leave small compartments such as the cilium.
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Affiliation(s)
- Paul G DeCaen
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Xiaowen Liu
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Sunday Abiria
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - David E Clapham
- Department of Cardiology, Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
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38
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Okeke E, Parker T, Dingsdale H, Concannon M, Awais M, Voronina S, Molgó J, Begg M, Metcalf D, Knight AE, Sutton R, Haynes L, Tepikin AV. Epithelial-mesenchymal transition, IP3 receptors and ER-PM junctions: translocation of Ca2+ signalling complexes and regulation of migration. Biochem J 2016; 473:757-67. [PMID: 26759379 PMCID: PMC4785603 DOI: 10.1042/bj20150364] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 12/21/2015] [Accepted: 01/12/2016] [Indexed: 12/22/2022]
Abstract
Disconnection of a cell from its epithelial neighbours and the formation of a mesenchymal phenotype are associated with profound changes in the distribution of cellular components and the formation of new cellular polarity. We observed a dramatic redistribution of inositol trisphosphate receptors (IP3Rs) and stromal interaction molecule 1 (STIM1)-competent endoplasmic reticulum-plasma membrane junctions (ER-PM junctions) when pancreatic ductal adenocarcinoma (PDAC) cells disconnect from their neighbours and undergo individual migration. In cellular monolayers IP3Rs are juxtaposed with tight junctions. When individual cells migrate away from their neighbours IP3Rs preferentially accumulate at the leading edge where they surround focal adhesions. Uncaging of inositol trisphosphate (IP3) resulted in prominent accumulation of paxillin in focal adhesions, highlighting important functional implications of the observed novel structural relationships. ER-PM junctions and STIM1 proteins also migrate to the leading edge and position closely behind the IP3Rs, creating a stratified distribution of Ca(2+) signalling complexes in this region. Importantly, migration of PDAC cells was strongly suppressed by selective inhibition of IP3Rs and store-operated Ca(2+) entry (SOCE), indicating that these mechanisms are functionally required for migration.
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Affiliation(s)
- Emmanuel Okeke
- Department of Cellular and Molecular Physiology, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
| | - Tony Parker
- Department of Cellular and Molecular Physiology, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
| | - Hayley Dingsdale
- Department of Cellular and Molecular Physiology, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
| | - Matthew Concannon
- Department of Cellular and Molecular Physiology, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
| | - Muhammad Awais
- NIHR Liverpool Pancreas Biomedical Research Unit, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
| | - Svetlana Voronina
- Department of Cellular and Molecular Physiology, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
| | - Jordi Molgó
- CEA, Institut de Biologie et Technologies de Saclay (iBiTec-S), Service d'Ingénierie Moléculaire des Protéines (SIMOPRO), bâtiment 152, 91191 Gif-sur-Yvette Cedex, France Institut des Neurosciences Paris-Saclay, UMR 9197, CNRS/Université Paris-Sud, CNRS, 91190-Gif sur Yvette Cedex, France
| | - Malcolm Begg
- Respiratory Therapy Area Unit, Medicines Research Centre, GlaxoSmithKline, Stevenage SG1 2NY, England, U.K
| | - Daniel Metcalf
- Biotechnology Group, National Physical Laboratory, Hampton Road, Teddington TW11 0LW, U.K
| | - Alex E Knight
- Biotechnology Group, National Physical Laboratory, Hampton Road, Teddington TW11 0LW, U.K
| | - Robert Sutton
- NIHR Liverpool Pancreas Biomedical Research Unit, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
| | - Lee Haynes
- Department of Cellular and Molecular Physiology, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
| | - Alexei V Tepikin
- Department of Cellular and Molecular Physiology, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K.
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He LL, Zhang QF, Wang LC, Dai JX, Wang CH, Zheng LH, Zhou Z. Muscarinic inhibition of nicotinic transmission in rat sympathetic neurons and adrenal chromaffin cells. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2014.0188. [PMID: 26009767 DOI: 10.1098/rstb.2014.0188] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Little is known about the interactions between nicotinic and muscarinic acetylcholine receptors (nAChRs and mAChRs). Here we report that methacholine (MCh), a selective agonist of mAChRs, inhibited up to 80% of nicotine-induced nAChR currents in sympathetic superior cervical ganglion neurons and adrenal chromaffin cells. The muscarine-induced inhibition (MiI) substantially reduced ACh-induced membrane currents through nAChRs and quantal neurotransmitter release. The MiI was time- and temperature-dependent. The slow recovery of nAChR current after washout of MCh, as well as the high value of Q10 (3.2), suggested, instead of a direct open-channel blockade, an intracellular metabotropic process. The effects of GTP-γ-S, GDP-β-S and pertussis toxin suggested that MiI was mediated by G-protein signalling. Inhibitors of protein kinase C (bisindolymaleimide-Bis), protein kinase A (H89) and PIP2 depletion attenuated the MiI, indicating that a second messenger pathway is involved in this process. Taken together, these data suggest that mAChRs negatively modulated nAChRs via a G-protein-mediated second messenger pathway. The time dependence suggests that MiI may provide a novel mechanism for post-synaptic adaptation in all cells/neurons and synapses expressing both types of AChRs.
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Affiliation(s)
- Lin-Ling He
- State Key Laboratory of Biomembrane and Membrane Biotechnology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and PKU-IDG/McGovern Institute for Brain Research and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, People's Republic of China Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Quan-Feng Zhang
- State Key Laboratory of Biomembrane and Membrane Biotechnology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and PKU-IDG/McGovern Institute for Brain Research and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Lie-Cheng Wang
- State Key Laboratory of Biomembrane and Membrane Biotechnology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and PKU-IDG/McGovern Institute for Brain Research and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Jing-Xia Dai
- State Key Laboratory of Biomembrane and Membrane Biotechnology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and PKU-IDG/McGovern Institute for Brain Research and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Chang-He Wang
- State Key Laboratory of Biomembrane and Membrane Biotechnology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and PKU-IDG/McGovern Institute for Brain Research and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Liang-Hong Zheng
- State Key Laboratory of Biomembrane and Membrane Biotechnology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and PKU-IDG/McGovern Institute for Brain Research and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Zhuan Zhou
- State Key Laboratory of Biomembrane and Membrane Biotechnology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and PKU-IDG/McGovern Institute for Brain Research and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, People's Republic of China
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40
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McMahon SM, Chang CW, Jackson MB. Multiple cytosolic calcium buffers in posterior pituitary nerve terminals. ACTA ACUST UNITED AC 2016; 147:243-54. [PMID: 26880753 PMCID: PMC4772375 DOI: 10.1085/jgp.201511525] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 01/06/2016] [Indexed: 01/03/2023]
Abstract
Researchers have measured the ability of nerve terminals to buffer Ca2+ entering in response to electrical activity to better understand plasticity of hormone release. Cytosolic Ca2+ buffers bind to a large fraction of Ca2+ as it enters a cell, shaping Ca2+ signals both spatially and temporally. In this way, cytosolic Ca2+ buffers regulate excitation-secretion coupling and short-term plasticity of release. The posterior pituitary is composed of peptidergic nerve terminals, which release oxytocin and vasopressin in response to Ca2+ entry. Secretion of these hormones exhibits a complex dependence on the frequency and pattern of electrical activity, and the role of cytosolic Ca2+ buffers in controlling pituitary Ca2+ signaling is poorly understood. Here, cytosolic Ca2+ buffers were studied with two-photon imaging in patch-clamped nerve terminals of the rat posterior pituitary. Fluorescence of the Ca2+ indicator fluo-8 revealed stepwise increases in free Ca2+ after a series of brief depolarizing pulses in rapid succession. These Ca2+ increments grew larger as free Ca2+ rose to saturate the cytosolic buffers and reduce the availability of Ca2+ binding sites. These titration data revealed two endogenous buffers. All nerve terminals contained a buffer with a Kd of 1.5–4.7 µM, and approximately half contained an additional higher-affinity buffer with a Kd of 340 nM. Western blots identified calretinin and calbindin D28K in the posterior pituitary, and their in vitro binding properties correspond well with our fluorometric analysis. The high-affinity buffer washed out, but at a rate much slower than expected from diffusion; washout of the low-affinity buffer could not be detected. This work has revealed the functional impact of cytosolic Ca2+ buffers in situ in nerve terminals at a new level of detail. The saturation of these cytosolic buffers will amplify Ca2+ signals and may contribute to use-dependent facilitation of release. A difference in the buffer compositions of oxytocin and vasopressin nerve terminals could contribute to the differences in release plasticity of these two hormones.
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Affiliation(s)
- Shane M McMahon
- Biophysics PhD Program, Department of Neuroscience, and Physiology PhD Program, University of Wisconsin, Madison, WI 53705
| | - Che-Wei Chang
- Biophysics PhD Program, Department of Neuroscience, and Physiology PhD Program, University of Wisconsin, Madison, WI 53705 Biophysics PhD Program, Department of Neuroscience, and Physiology PhD Program, University of Wisconsin, Madison, WI 53705
| | - Meyer B Jackson
- Biophysics PhD Program, Department of Neuroscience, and Physiology PhD Program, University of Wisconsin, Madison, WI 53705
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41
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Kinetics on Demand Is a Simple Mathematical Solution that Fits Recorded Caffeine-Induced Luminal SR Ca2+ Changes in Smooth Muscle Cells. PLoS One 2015; 10:e0138195. [PMID: 26390403 PMCID: PMC4577101 DOI: 10.1371/journal.pone.0138195] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 08/27/2015] [Indexed: 12/02/2022] Open
Abstract
The process of Ca2+ release from sarcoplasmic reticulum (SR) comprises 4 phases in smooth muscle cells. Phase 1 is characterized by a large increase of the intracellular Ca2+ concentration ([Ca2+]i) with a minimal reduction of the free luminal SR [Ca2+] ([Ca2+]FSR). Importantly, active SR Ca2+ ATPases (SERCA pumps) are necessary for phase 1 to occur. This situation cannot be explained by the standard kinetics that involves a fixed amount of luminal Ca2+ binding sites. A new mathematical model was developed that assumes an increasing SR Ca2+ buffering capacity in response to an increase of the luminal SR [Ca2+] that is called Kinetics-on-Demand (KonD) model. This approach can explain both phase 1 and the refractory period associated with a recovered [Ca2+]FSR. Additionally, our data suggest that active SERCA pumps are a requisite for KonD to be functional; otherwise luminal SR Ca2+ binding proteins switch to standard kinetics. The importance of KonD Ca2+ binding properties is twofold: a more efficient Ca2+ release process and that [Ca2+]FSR and Ca2+-bound to SR proteins ([Ca2+]BSR) can be regulated separately allowing for Ca2+ release to occur (provided by Ca2+-bound to luminal Ca2+ binding proteins) without an initial reduction of the [Ca2+]FSR.
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42
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Abstract
Calcium influx during action potentials triggers neurotransmitter release at presynaptic active zones. Calcium buffers limit the spread of calcium and restrict neurotransmitter release to the vicinity of calcium channels. To sustain synchronous release during repetitive activity, rapid removal of calcium from the active zone is essential, but the underlying mechanisms are unclear. Therefore, we focused on cerebellar mossy fiber synapses, which are among the fastest synapses in the mammalian brain and found very weak presynaptic calcium buffering. One might assume that strong calcium buffering has the potential to efficiently remove calcium from active zones. In contrast, our results show that weak calcium buffering speeds active zone calcium clearance. Thus, the strength of presynaptic buffering limits the rate of synaptic transmission. Fast synchronous neurotransmitter release at the presynaptic active zone is triggered by local Ca2+ signals, which are confined in their spatiotemporal extent by endogenous Ca2+ buffers. However, it remains elusive how rapid and reliable Ca2+ signaling can be sustained during repetitive release. Here, we established quantitative two-photon Ca2+ imaging in cerebellar mossy fiber boutons, which fire at exceptionally high rates. We show that endogenous fixed buffers have a surprisingly low Ca2+-binding ratio (∼15) and low affinity, whereas mobile buffers have high affinity. Experimentally constrained modeling revealed that the low endogenous buffering promotes fast clearance of Ca2+ from the active zone during repetitive firing. Measuring Ca2+ signals at different distances from active zones with ultra-high-resolution confirmed our model predictions. Our results lead to the concept that reduced Ca2+ buffering enables fast active zone Ca2+ signaling, suggesting that the strength of endogenous Ca2+ buffering limits the rate of synchronous synaptic transmission.
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43
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Filadi R, Pozzan T. Generation and functions of second messengers microdomains. Cell Calcium 2015; 58:405-14. [PMID: 25861743 DOI: 10.1016/j.ceca.2015.03.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 03/17/2015] [Accepted: 03/18/2015] [Indexed: 01/09/2023]
Abstract
A compelling example of the mechanisms by which the cells can organize and decipher complex and different functional activities is the convergence of a multitude of stimuli into signalling cascades, involving only few intracellular second messengers. The possibility of restricting these signalling events in distinct microdomains allows a fine and selective tuning of very different tasks. In this review, we will discuss the mechanisms that control the formation and the spatial distribution of Ca(2+) and cAMP microdomains, providing some examples of their functional consequences.
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Affiliation(s)
- Riccardo Filadi
- Department of Biomedical Sciences, University of Padova, Italy
| | - Tullio Pozzan
- Department of Biomedical Sciences, University of Padova, Italy; CNR Institute of Neuroscience, Padova Section, Padova, Italy; Venetian Institute of Molecular Medicine (VIMM), Padova, Italy.
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44
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De Clercq K, Held K, Van Bree R, Meuleman C, Peeraer K, Tomassetti C, Voets T, D'Hooghe T, Vriens J. Functional expression of transient receptor potential channels in human endometrial stromal cells during the luteal phase of the menstrual cycle. Hum Reprod 2015; 30:1421-36. [PMID: 25820697 DOI: 10.1093/humrep/dev068] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 03/05/2015] [Indexed: 12/21/2022] Open
Abstract
STUDY QUESTION Are members of the transient receptor potential (TRP) channel superfamily functionally expressed in the human endometrial stroma? SUMMARY ANSWER The Ca(2+)-permeable ion channels TRPV2, TRPV4, TRPC6 and TRPM7 are functionally expressed in primary endometrial stromal cells. WHAT IS KNOWN ALREADY Intercellular communication between epithelial and stromal endometrial cells is required to initiate decidualization, a prerequisite for successful implantation. TRP channels are possible candidates as signal transducers involved in cell-cell communication, but no fingerprint is available of the functional distribution of TRP channels in the human endometrium during the luteal phase of the menstrual cycle. STUDY DESIGN, SIZE, DURATION Endometrial biopsy samples (previously frozen) from patients of reproductive age with regular menstrual cycles, who were undergoing diagnostic laparoscopic surgery for pain and/or infertility, were analysed. Samples were obtained from the menstrual (Days 1-5, n = 3), follicular (Days 6-14, n = 6), early luteal (Days 15-20, n = 5) and late luteal (Days 21-28, n = 5) phases. In addition, a total of 13 patient samples taken during the luteal phase were used to set up primary cell cultures for further experiments. PARTICIPANTS/MATERIALS, SETTING, METHODS Quantitative real-time PCR (qRT-PCR), immunocytochemistry, Fura2-based Ca(2+)-microfluorimetry and whole-cell patch clamp experiments were performed to study the functional expression pattern of TRP channels. Specific pharmacological agents, such as Δ(9)-tetrahydrocannabinol, GSK1016790A and 1-oleoyl-2-acetyl-glycerol, were used to functionally assess the expression of TRPV2, TRPV4 and TRPC6, respectively. MAIN RESULTS AND THE ROLE OF CHANCE Expression of TRPV2, TRPV4, TRPC1, TRPC4, TRPC6, TRPM4 and TRPM7 was detected at the mRNA level in endometrial biopsies (n = 19) and in primary endometrial stromal cell cultures obtained from patients during the luteal phase (n = 5) of the menstrual cycle. Messenger RNA levels of TRPV2, TRPC4 and TRPC6 were significantly increased (P < 0.01) in the late luteal phase compared with the early luteal phase. Immunocytochemistry experiments showed a positive staining for TRPV2, TRPV4, TRPC6 and TRPM7 in the plasma membrane and in the cytoplasm of primary endometrial stromal cells. Ca(2+)-microfluorimetry revealed significant increases (P < 0.001) in intracellular Ca(2+) levels when stromal cells were incubated with specific activators of TRPV2, TRPV4 and TRPC6. Further functional characterization was performed using whole-cell patch clamp experiments. Taken together, these data provide evidence for the functional activity of TRPV2, TRPV4, TRPC6 and TRPM7 channels in primary stromal cell cultures. LIMITATIONS, REASONS FOR CAUTION Although mRNA levels are detected for TRPV6, TRPC1, TRPC4 and TRPM4, the limited supply of specific antibodies and lack of selective pharmacological agents restricted any additional analysis of these ion channels. WIDER IMPLICATIONS OF THE FINDINGS Embryo implantation is a dynamic developmental process that integrates many signalling molecules into a precisely orchestrated programme. Our findings identified certain members of the TRP superfamily as candidate sensors in the epithelial-stromal crosstalk. These results are very helpful to unravel the signalling cascade required for successful embryo implantation. In addition, this knowledge could lead to new strategies to correct implantation failure and facilitate the development of novel non-hormonal contraceptives. STUDY FUNDING/ COMPETING INTERESTS This work was supported by grants from the Research Foundation-Flanders (G.0856.13N to J.V.), the Research Council of the KU Leuven (OT/13/113 to J.V. and T.D. and PF-TRPLe to T.V.) and by the Planckaert-De Waele fund (to J.V.). K.D.C. and K.H. are funded by the FWO Belgium. None of the authors have a conflict of interest.
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Affiliation(s)
- Katrien De Clercq
- Laboratory of Obstetrics and Experimental Gynaecology, KU Leuven, Herestraat 49 box 611, B-3000 Leuven, Belgium
| | - Katharina Held
- Laboratory of Obstetrics and Experimental Gynaecology, KU Leuven, Herestraat 49 box 611, B-3000 Leuven, Belgium Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), KU Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| | - Rieta Van Bree
- Laboratory of Obstetrics and Experimental Gynaecology, KU Leuven, Herestraat 49 box 611, B-3000 Leuven, Belgium
| | - Christel Meuleman
- Department of Obstetrics and Gynaecology, Leuven University Fertility Centre, University Hospital Gasthuisberg, B-3000 Leuven, Belgium
| | - Karen Peeraer
- Department of Obstetrics and Gynaecology, Leuven University Fertility Centre, University Hospital Gasthuisberg, B-3000 Leuven, Belgium
| | - Carla Tomassetti
- Department of Obstetrics and Gynaecology, Leuven University Fertility Centre, University Hospital Gasthuisberg, B-3000 Leuven, Belgium
| | - Thomas Voets
- Laboratory of Ion Channel Research and TRP Research Platform Leuven (TRPLe), KU Leuven, Herestraat 49 box 802, B-3000 Leuven, Belgium
| | - Thomas D'Hooghe
- Department of Obstetrics and Gynaecology, Leuven University Fertility Centre, University Hospital Gasthuisberg, B-3000 Leuven, Belgium
| | - Joris Vriens
- Laboratory of Obstetrics and Experimental Gynaecology, KU Leuven, Herestraat 49 box 611, B-3000 Leuven, Belgium
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45
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Matthews EA, Dietrich D. Buffer mobility and the regulation of neuronal calcium domains. Front Cell Neurosci 2015; 9:48. [PMID: 25750615 PMCID: PMC4335178 DOI: 10.3389/fncel.2015.00048] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 01/31/2015] [Indexed: 11/13/2022] Open
Abstract
The diffusion of calcium inside neurons is determined in part by the intracellular calcium binding species that rapidly bind to free calcium ions upon entry. It has long been known that some portion of a neuron's intracellular calcium binding capacity must be fixed or poorly mobile, as calcium diffusion is strongly slowed in the intracellular environment relative to diffusion in cytosolic extract. The working assumption was that these immobile calcium binding sites are provided by structural proteins bound to the cytoskeleton or intracellular membranes and may thereby be relatively similar in composition and capacity across different cell types. However, recent evidence suggests that the immobile buffering capacity can vary greatly between cell types and that some mobile calcium binding proteins may alter their mobility upon binding calcium, thus blurring the line between mobile and immobile. The ways in which immobile buffering capacity might be relevant to different calcium domains within neurons has been explored primarily through modeling. In certain regimes, the presence of immobile buffers and the interaction between mobile and immobile buffers have been shown to result in complex spatiotemporal patterns of free calcium. In total, these experimental and modeling findings call for a more nuanced consideration of the local intracellular calcium microenvironment. In this review we focus on the different amounts, affinities, and mobilities of immobile calcium binding species; propose a new conceptual category of physically diffusible but functionally immobile buffers; and discuss how these buffers might interact with mobile calcium binding partners to generate characteristic calcium domains.
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Affiliation(s)
- Elizabeth A. Matthews
- Experimental Neurophysiology, Department of Neurosurgery, University Clinic BonnBonn, Germany
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Samigullin D, Fatikhov N, Khaziev E, Skorinkin A, Nikolsky E, Bukharaeva E. Estimation of presynaptic calcium currents and endogenous calcium buffers at the frog neuromuscular junction with two different calcium fluorescent dyes. Front Synaptic Neurosci 2015; 6:29. [PMID: 25709579 PMCID: PMC4285738 DOI: 10.3389/fnsyn.2014.00029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 12/12/2014] [Indexed: 12/02/2022] Open
Abstract
At the frog neuromuscular junction, under physiological conditions, the direct measurement of calcium currents and of the concentration of intracellular calcium buffers—which determine the kinetics of calcium concentration and neurotransmitter release from the nerve terminal—has hitherto been technically impossible. With the aim of quantifying both Ca2+ currents and the intracellular calcium buffers, we measured fluorescence signals from nerve terminals loaded with the low-affinity calcium dye Magnesium Green or the high-affinity dye Oregon Green BAPTA-1, simultaneously with microelectrode recordings of nerve-action potentials and end-plate currents. The action-potential-induced fluorescence signals in the nerve terminals developed much more slowly than the postsynaptic response. To clarify the reasons for this observation and to define a spatiotemporal profile of intracellular calcium and of the concentration of mobile and fixed calcium buffers, mathematical modeling was employed. The best approximations of the experimental calcium transients for both calcium dyes were obtained when the calcium current had an amplitude of 1.6 ± 0.08 pA and a half-decay time of 1.2 ± 0.06 ms, and when the concentrations of mobile and fixed calcium buffers were 250 ± 13 μM and 8 ± 0.4 mM, respectively. High concentrations of endogenous buffers define the time course of calcium transients after an action potential in the axoplasm, and may modify synaptic plasticity.
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Affiliation(s)
- Dmitry Samigullin
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia ; Open Laboratory of Neuropharmacology, Kazan Federal University Kazan, Russia ; Department of Radiophotonics and Microwave Technologies, Kazan National Research Technical University named after A. N. Tupolev Kazan, Russia
| | - Nijaz Fatikhov
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia
| | - Eduard Khaziev
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia ; Open Laboratory of Neuropharmacology, Kazan Federal University Kazan, Russia
| | - Andrey Skorinkin
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia ; Department of Neurobiology and Radioelectronics, Kazan Federal University Kazan, Russia
| | - Eugeny Nikolsky
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia ; Open Laboratory of Neuropharmacology, Kazan Federal University Kazan, Russia ; Department of Medical and Biological Physics, Kazan State Medical University Kazan, Russia
| | - Ellya Bukharaeva
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia ; Open Laboratory of Neuropharmacology, Kazan Federal University Kazan, Russia
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Rose T, Goltstein PM, Portugues R, Griesbeck O. Putting a finishing touch on GECIs. Front Mol Neurosci 2014; 7:88. [PMID: 25477779 PMCID: PMC4235368 DOI: 10.3389/fnmol.2014.00088] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 10/29/2014] [Indexed: 01/12/2023] Open
Abstract
More than a decade ago genetically encoded calcium indicators (GECIs) entered the stage as new promising tools to image calcium dynamics and neuronal activity in living tissues and designated cell types in vivo. From a variety of initial designs two have emerged as promising prototypes for further optimization: FRET (Förster Resonance Energy Transfer)-based sensors and single fluorophore sensors of the GCaMP family. Recent efforts in structural analysis, engineering and screening have broken important performance thresholds in the latest generation for both classes. While these improvements have made GECIs a powerful means to perform physiology in living animals, a number of other aspects of sensor function deserve attention. These aspects include indicator linearity, toxicity and slow response kinetics. Furthermore creating high performance sensors with optically more favorable emission in red or infrared wavelengths as well as new stably or conditionally GECI-expressing animal lines are on the wish list. When the remaining issues are solved, imaging of GECIs will finally have crossed the last milestone, evolving from an initial promise into a fully matured technology.
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Affiliation(s)
- Tobias Rose
- Max-Planck-Institute of Neurobiology Martinsried, Germany
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An alien divalent ion reveals a major role for Ca²⁺ buffering in controlling slow transmitter release. J Neurosci 2014; 34:12622-35. [PMID: 25232102 DOI: 10.1523/jneurosci.1990-14.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Ca(2+)-dependent transmitter release occurs in a fast and in a slow phase, but the differential roles of Ca(2+) buffers and Ca(2+) sensors in shaping release kinetics are still controversial. Replacing extracellular Ca(2+) by Sr(2+) causes decreased fast release but enhanced slow release at many synapses. Here, we established presynaptic Sr(2+) uncaging and made quantitative Sr(2+)- and Ca(2+)-imaging experiments at the mouse calyx of Held synapse, to reveal the interplay between Ca(2+) sensors and Ca(2+) buffers in the control of fast and slow release. We show that Sr(2+) activates the fast, Synaptotagmin-2 (Syt2) sensor for vesicle fusion with sixfold lower affinity but unchanged high cooperativity. Surprisingly, Sr(2+) also activates the slow sensor that remains in Syt2 knock-out synapses with a lower efficiency, and Sr(2+) was less efficient than Ca(2+) in the limit of low concentrations in wild-type synapses. Quantitative imaging experiments show that the buffering capacity of the nerve terminal is markedly lower for Sr(2+) than for Ca(2+) (~5-fold). This, together with an enhanced Sr(2+) permeation through presynaptic Ca(2+) channels (~2-fold), admits a drastically higher spatially averaged Sr(2+) transient compared with Ca(2+). Together, despite the lower affinity of Sr(2+) at the fast and slow sensors, the massively higher amplitudes of spatially averaged Sr(2+) transients explain the enhanced late release. This also allows us to conclude that Ca(2+) buffering normally controls late release and prevents the activation of the fast release sensor by residual Ca(2+).
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In situ Ca2+ titration in the fluorometric study of intracellular Ca2+ binding. Cell Calcium 2014; 56:504-12. [PMID: 25465896 DOI: 10.1016/j.ceca.2014.10.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 10/15/2014] [Accepted: 10/20/2014] [Indexed: 12/15/2022]
Abstract
Imaging with Ca(2+)-sensitive fluorescent dye has provided a wealth of insight into the dynamics of cellular Ca(2+) signaling. The spatiotemporal evolution of intracellular free Ca(2+) observed in imaging experiments is shaped by binding and unbinding to cytoplasmic Ca(2+) buffers, as well as the fluorescent indicator used for imaging. These factors must be taken into account in the interpretation of Ca(2+) imaging data, and can be exploited to investigate endogenous Ca(2+) buffer properties. Here we extended the use of Ca(2+) fluorometry in the characterization of Ca(2+) binding molecules within cells, building on a method of titration of intracellular Ca(2+) binding sites in situ with measured amounts of Ca(2+) entering through voltage-gated Ca(2+) channels. We developed a systematic procedure for fitting fluorescence data acquired during a series of voltage steps to models with multiple Ca(2+) binding sites. The method was tested on simulated data, and then applied to 2-photon fluorescence imaging data from rat posterior pituitary nerve terminals patch clamp-loaded with the Ca(2+) indicator fluo-8. Focusing on data sets well described by a single endogenous Ca(2+) buffer and dye, this method yielded estimates of the endogenous buffer concentration and Kd, the dye Kd, and the fraction of Ca(2+) inaccessible cellular volume. The in situ Kd of fluo-8 thus obtained was indistinguishable from that measured in vitro. This method of calibrating Ca(2+)-sensitive fluorescent dyes in situ has significant advantages over previous methods. Our analysis of Ca(2+) titration fluorometric data makes more effective use of the experimental data, and provides a rigorous treatment of multivariate errors and multiple Ca(2+) binding species. This method offers a versatile approach to the study of endogenous Ca(2+) binding molecules in their physiological milieu.
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Woehler A, Lin KH, Neher E. Calcium-buffering effects of gluconate and nucleotides, as determined by a novel fluorimetric titration method. J Physiol 2014; 592:4863-75. [PMID: 25194050 DOI: 10.1113/jphysiol.2014.281097] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Significantly more Ca(2+) influx is required for eliciting release of neurotransmitter during whole cell patch clamp recording in the Calyx of Held, when gluconate with 3 mm free ATP is used as pipette filling solution, as compared to a methanesulfonate-based solution with excess Mg(2+). This reduction in efficiency of Ca(2+) in eliciting release is due to low-affinity Ca(2+) binding of both gluconate and ATP(2-) anions. To study these effects we developed a simple fluorimeteric titration procedure, which reports the dissociation constant, KD, of a given Ca(2+) indicator dye, multiplied by 1 plus the sum of Ca(2+) binding ratios of any anions, which act as low-affinity Ca(2+) ligands. For solutions without Ca(2+) binding anions we find KD values for Fura2FF ranging from 11.5 ± 1.7 to 15.6 ± 7.47 μm depending on the dominant anion used. For Fura6F and KCl-based solutions we find KD = 17.8 ± 1.3 μm. For solutions with gluconate as the main anion and for solutions that contain nucleotides, such as ATP and GTP, we find much higher values for the product. Assuming that the KD of the indicator dye is equal to that of KCl-based solutions we calculate the summed Ca(2+) binding ratios and find a value of 3.55 for a solution containing 100 mm potassium gluconate and 4 mm ATP. Gluconate contributes a value of 1.75 to this number, while the contribution of ATP depends strongly on the presence of Mg(2+) and varies from 0.8 (with excess Mg(2+)) to 13.8 (in the presence of 3 mm free ATP). Methanesulfonate has negligible Ca(2+) binding capacity. These results explain the reduced efficiency of Ca(2+) influx in the presence of gluconate or nucleotides, as these anions are expected to intercept Ca(2+) ions at short distance.
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Affiliation(s)
- Andrew Woehler
- Max-Planck-Institute for Biophysical Chemistry, Göttingen, 37077, Germany DFG-Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, 37073, Germany
| | - Kun-Han Lin
- Max-Planck-Institute for Biophysical Chemistry, Göttingen, 37077, Germany
| | - Erwin Neher
- Max-Planck-Institute for Biophysical Chemistry, Göttingen, 37077, Germany DFG-Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, 37073, Germany
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