1
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Current Methods to Unravel the Functional Properties of Lysosomal Ion Channels and Transporters. Cells 2022; 11:cells11060921. [PMID: 35326372 PMCID: PMC8946281 DOI: 10.3390/cells11060921] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 03/04/2022] [Accepted: 03/05/2022] [Indexed: 02/07/2023] Open
Abstract
A distinct set of channels and transporters regulates the ion fluxes across the lysosomal membrane. Malfunctioning of these transport proteins and the resulting ionic imbalance is involved in various human diseases, such as lysosomal storage disorders, cancer, as well as metabolic and neurodegenerative diseases. As a consequence, these proteins have stimulated strong interest for their suitability as possible drug targets. A detailed functional characterization of many lysosomal channels and transporters is lacking, mainly due to technical difficulties in applying the standard patch-clamp technique to these small intracellular compartments. In this review, we focus on current methods used to unravel the functional properties of lysosomal ion channels and transporters, stressing their advantages and disadvantages and evaluating their fields of applicability.
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2
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Pham Ba VA, Pham Van Bach N, Nguyen Luong T, Nguyen KV. Semiconducting Carbon Nanotube-Based Nanodevices for Monitoring the Effects of Chlorphenamine on the Activities of Intracellular Ca 2+ Stores. JOURNAL OF ANALYTICAL METHODS IN CHEMISTRY 2022; 2022:9019262. [PMID: 35284149 PMCID: PMC8906990 DOI: 10.1155/2022/9019262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 02/04/2022] [Indexed: 06/14/2023]
Abstract
We report a flexible and noninvasive method based on field-effect transistors hybridizing semiconducting single-walled carbon nanotubes for monitoring the effects of histamine on Ca2+ release from the intracellular stores of a nonexcitable cell. These nanodevices allowed us to evaluate the real-time electrophysiological activities of HeLa cells under the stimulation of histamine via the recording of the conductance changes of the devices. These changes resulted from the binding of histamine to its receptor type 1 on the HeLa cell membrane. Moreover, the effects of chlorphenamine, an antihistamine, on the electrophysiological activities of a single HeLa cell were also evaluated, indicating that the pretreatment of the cell with chlorpheniramine decreased intracellular Ca2+ release. Significantly, we only utilized a single nanodevice to perform the measurements for multiple cells pretreated with various concentrations of chlorphenamine. This enabled the statistically meaningful analysis of drug effects on cells without errors from device variations. Obtained results indicated the novel advantages of our method such as real-time monitoring and quantitative capability. Our devices, therefore, can be efficient tools for biomedical applications such as electrophysiology research and drug screening.
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Affiliation(s)
- Viet Anh Pham Ba
- Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Hanoi, Vietnam
- Department of Environmental Toxicology and Monitoring, Hanoi University of Natural Resources and Environment, Hanoi, Vietnam
| | - Ngoc Pham Van Bach
- Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Hanoi, Vietnam
- Space Technology Institute, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | - Thien Nguyen Luong
- Space Technology Institute, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | - Khoa Viet Nguyen
- Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Hanoi, Vietnam
- Institute of Mechanics, Vietnam Academy of Science and Technology, Hanoi, Vietnam
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3
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KRAP tethers IP 3 receptors to actin and licenses them to evoke cytosolic Ca 2+ signals. Nat Commun 2021; 12:4514. [PMID: 34301929 PMCID: PMC8302619 DOI: 10.1038/s41467-021-24739-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 07/01/2021] [Indexed: 02/06/2023] Open
Abstract
Regulation of IP3 receptors (IP3Rs) by IP3 and Ca2+ allows regenerative Ca2+ signals, the smallest being Ca2+ puffs, which arise from coordinated openings of a few clustered IP3Rs. Cells express thousands of mostly mobile IP3Rs, yet Ca2+ puffs occur at a few immobile IP3R clusters. By imaging cells with endogenous IP3Rs tagged with EGFP, we show that KRas-induced actin-interacting protein (KRAP) tethers IP3Rs to actin beneath the plasma membrane. Loss of KRAP abolishes Ca2+ puffs and the global increases in cytosolic Ca2+ concentration evoked by more intense stimulation. Over-expressing KRAP immobilizes additional IP3R clusters and results in more Ca2+ puffs and larger global Ca2+ signals. Endogenous KRAP determines which IP3Rs will respond: it tethers IP3R clusters to actin alongside sites where store-operated Ca2+ entry occurs, licenses IP3Rs to evoke Ca2+ puffs and global cytosolic Ca2+ signals, implicates the actin cytoskeleton in IP3R regulation and may allow local activation of Ca2+ entry.
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4
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Márquez-Nogueras KM, Hortua Triana MA, Chasen NM, Kuo IY, Moreno SN. Calcium signaling through a transient receptor channel is important for Toxoplasma gondii growth. eLife 2021; 10:63417. [PMID: 34106044 PMCID: PMC8216714 DOI: 10.7554/elife.63417] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 06/08/2021] [Indexed: 12/24/2022] Open
Abstract
Transient receptor potential (TRP) channels participate in calcium ion (Ca2+) influx and intracellular Ca2+ release. TRP channels have not been studied in Toxoplasma gondii or any other apicomplexan parasite. In this work, we characterize TgGT1_310560, a protein predicted to possess a TRP domain (TgTRPPL-2), and determined its role in Ca2+ signaling in T. gondii, the causative agent of toxoplasmosis. TgTRPPL-2 localizes to the plasma membrane and the endoplasmic reticulum (ER) of T. gondii. The ΔTgTRPPL-2 mutant was defective in growth and cytosolic Ca2+ influx from both extracellular and intracellular sources. Heterologous expression of TgTRPPL-2 in HEK-3KO cells allowed its functional characterization. Patching of ER-nuclear membranes demonstrates that TgTRPPL-2 is a non-selective cation channel that conducts Ca2+. Pharmacological blockers of TgTRPPL-2 inhibit Ca2+ influx and parasite growth. This is the first report of an apicomplexan ion channel that conducts Ca2+ and may initiate a Ca2+ signaling cascade that leads to the stimulation of motility, invasion, and egress. TgTRPPL-2 is a potential target for combating toxoplasmosis.
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Affiliation(s)
- Karla Marie Márquez-Nogueras
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, United States.,Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, United States
| | | | - Nathan M Chasen
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, United States
| | - Ivana Y Kuo
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, United States
| | - Silvia Nj Moreno
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, United States.,Department of Cellular Biology, University of Georgia, Athens, United States
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5
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Vais H, Wang M, Mallilankaraman K, Payne R, McKennan C, Lock JT, Spruce LA, Fiest C, Chan MYL, Parker I, Seeholzer SH, Foskett JK, Mak DOD. ER-luminal [Ca 2+] regulation of InsP 3 receptor gating mediated by an ER-luminal peripheral Ca 2+-binding protein. eLife 2020; 9:e53531. [PMID: 32420875 PMCID: PMC7259957 DOI: 10.7554/elife.53531] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 05/15/2020] [Indexed: 12/17/2022] Open
Abstract
Modulating cytoplasmic Ca2+ concentration ([Ca2+]i) by endoplasmic reticulum (ER)-localized inositol 1,4,5-trisphosphate receptor (InsP3R) Ca2+-release channels is a universal signaling pathway that regulates numerous cell-physiological processes. Whereas much is known regarding regulation of InsP3R activity by cytoplasmic ligands and processes, its regulation by ER-luminal Ca2+ concentration ([Ca2+]ER) is poorly understood and controversial. We discovered that the InsP3R is regulated by a peripheral membrane-associated ER-luminal protein that strongly inhibits the channel in the presence of high, physiological [Ca2+]ER. The widely-expressed Ca2+-binding protein annexin A1 (ANXA1) is present in the nuclear envelope lumen and, through interaction with a luminal region of the channel, can modify high-[Ca2+]ER inhibition of InsP3R activity. Genetic knockdown of ANXA1 expression enhanced global and local elementary InsP3-mediated Ca2+ signaling events. Thus, [Ca2+]ER is a major regulator of InsP3R channel activity and InsP3R-mediated [Ca2+]i signaling in cells by controlling an interaction of the channel with a peripheral membrane-associated Ca2+-binding protein, likely ANXA1.
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Affiliation(s)
- Horia Vais
- Department of Physiology, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
| | - Min Wang
- Department of Physiology, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
| | - Karthik Mallilankaraman
- Department of Physiology, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
| | - Riley Payne
- Department of Physiology, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
| | - Chris McKennan
- Department of Statistics, University of PittsburghPittsburghUnited States
| | - Jeffrey T Lock
- Department of Neurobiology and Behavior, University of CaliforniaIrvineUnited States
| | - Lynn A Spruce
- Proteomics Core Facility, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
| | - Carly Fiest
- Department of Physiology, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
| | - Matthew Yan-lok Chan
- Department of Physiology, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
| | - Ian Parker
- Department of Neurobiology and Behavior, University of CaliforniaIrvineUnited States
- Department of Physiology and Biophysics, University of CaliforniaIrvineUnited States
| | - Steven H Seeholzer
- Proteomics Core Facility, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
| | - J Kevin Foskett
- Department of Physiology, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
| | - Don-On Daniel Mak
- Department of Physiology, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
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6
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Shah SI, Demuro A, Mak DOD, Parker I, Pearson JE, Ullah G. TraceSpecks: A Software for Automated Idealization of Noisy Patch-Clamp and Imaging Data. Biophys J 2019; 115:9-21. [PMID: 29972815 DOI: 10.1016/j.bpj.2018.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 05/15/2018] [Accepted: 06/04/2018] [Indexed: 10/28/2022] Open
Abstract
Experimental records of single molecules or ion channels from fluorescence microscopy and patch-clamp electrophysiology often include high-frequency noise and baseline fluctuations that are not generated by the system under investigation and have to be removed. Moreover, multiple channels or conductance levels can be present at a time in the data that need to be quantified to accurately understand the behavior of the system. Manual procedures for removing these fluctuations and extracting conducting states or multiple channels are laborious, prone to subjective bias, and likely to hinder the processing of often very large data sets. We introduce a maximal likelihood formalism for separating signal from a noisy and drifting background such as fluorescence traces from imaging of elementary Ca2+ release events called puffs arising from clusters of channels, and patch-clamp recordings of ion channels. Parameters such as the number of open channels or conducting states, noise level, and background signal can all be optimized using the expectation-maximization algorithm. We implement our algorithm following the Baum-Welch approach to expectation-maximization in the portable Java language with a user-friendly graphical interface and test the algorithm on both synthetic and experimental data from the patch-clamp electrophysiology of Ca2+ channels and fluorescence microscopy of a cluster of Ca2+ channels and Ca2+ channels with multiple conductance levels. The resulting software is accurate, fast, and provides detailed information usually not available through manual analysis. Options for visual inspection of the raw and processed data with key parameters are provided, in addition to a range of statistics such as the mean open probabilities, mean open times, mean close times, dwell-time distributions for different number of channels open or conductance levels, amplitude distribution of all opening events, and number of transitions between different number of open channels or conducting levels in asci format with a single click.
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Affiliation(s)
| | - Angelo Demuro
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, California
| | - Don-On Daniel Mak
- Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Ian Parker
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, California; Department of Physiology and Biophysics, University of California, Irvine, Irvine, California
| | - John E Pearson
- Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, New Mexico
| | - Ghanim Ullah
- Department of Physics, University of South Florida, Tampa, Florida.
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7
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Potapenko E, Negrão NW, Huang G, Docampo R. The acidocalcisome inositol-1,4,5-trisphosphate receptor of Trypanosoma brucei is stimulated by luminal polyphosphate hydrolysis products. J Biol Chem 2019; 294:10628-10637. [PMID: 31138655 DOI: 10.1074/jbc.ra119.007906] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 05/27/2019] [Indexed: 12/21/2022] Open
Abstract
Acidocalcisomes are acidic calcium stores rich in polyphosphate (polyP) and are present in trypanosomes and also in a diverse range of other organisms. Ca2+ is released from these organelles through a channel, inositol 1,4,5-trisphosphate receptor (TbIP3R), which is essential for growth and infectivity of the parasite Trypanosoma brucei However, the mechanism by which TbIP3R controls Ca2+ release is unclear. In this work, we expressed TbIP3R in a chicken B lymphocyte cell line in which the genes for all three vertebrate IP3Rs were stably ablated (DT40-3KO). We show that IP3-mediated Ca2+ release depends on Ca2+ but not on ATP concentration and is inhibited by heparin, caffeine, and 2-aminomethoxydiphenyl borate (2-APB). Excised patch clamp recordings from nuclear membranes of DT40 cells expressing only TbIP3R disclosed that luminal inorganic orthophosphate (Pi) or pyrophosphate (PPi), and neutral or alkaline pH can stimulate IP3-generated currents. In contrast, polyP or acidic pH did not induce these currents, and nuclear membranes obtained from cells expressing rat IP3R were unresponsive to polyP or its hydrolysis products. Our results are consistent with the notion that polyP hydrolysis products within acidocalcisomes or alkalinization of their luminal pH activate TbIP3R and Ca2+ release. We conclude that TbIP3R is well-adapted to its role as the major Ca2+ release channel of acidocalcisomes in T. brucei.
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Affiliation(s)
| | - Núria W Negrão
- From the Center for Tropical and Emerging Global Diseases and.,Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| | - Guozhong Huang
- From the Center for Tropical and Emerging Global Diseases and
| | - Roberto Docampo
- From the Center for Tropical and Emerging Global Diseases and .,Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
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8
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Leanza L, Checchetto V, Biasutto L, Rossa A, Costa R, Bachmann M, Zoratti M, Szabo I. Pharmacological modulation of mitochondrial ion channels. Br J Pharmacol 2019; 176:4258-4283. [PMID: 30440086 DOI: 10.1111/bph.14544] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 10/15/2018] [Accepted: 10/22/2018] [Indexed: 12/17/2022] Open
Abstract
The field of mitochondrial ion channels has undergone a rapid development during the last three decades, due to the molecular identification of some of the channels residing in the outer and inner membranes. Relevant information about the function of these channels in physiological and pathological settings was gained thanks to genetic models for a few, mitochondria-specific channels. However, many ion channels have multiple localizations within the cell, hampering a clear-cut determination of their function by pharmacological means. The present review summarizes our current knowledge about the ins and outs of mitochondrial ion channels, with special focus on the channels that have received much attention in recent years, namely, the voltage-dependent anion channels, the permeability transition pore (also called mitochondrial megachannel), the mitochondrial calcium uniporter and some of the inner membrane-located potassium channels. In addition, possible strategies to overcome the difficulties of specifically targeting mitochondrial channels versus their counterparts active in other membranes are discussed, as well as the possibilities of modulating channel function by small peptides that compete for binding with protein interacting partners. Altogether, these promising tools along with large-scale chemical screenings set up to identify new, specific channel modulators will hopefully allow us to pinpoint the actual function of most mitochondrial ion channels in the near future and to pharmacologically affect important pathologies in which they are involved, such as neurodegeneration, ischaemic damage and cancer. LINKED ARTICLES: This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.
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Affiliation(s)
- Luigi Leanza
- Department of Biology, University of Padova, Padova, Italy
| | | | - Lucia Biasutto
- CNR Institute of Neurosciences, Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Andrea Rossa
- Department of Chemical Sciences, University of Padova, Padova, Italy
| | - Roberto Costa
- Department of Biology, University of Padova, Padova, Italy
| | | | - Mario Zoratti
- CNR Institute of Neurosciences, Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Ildiko Szabo
- Department of Biology, University of Padova, Padova, Italy.,CNR Institute of Neurosciences, Department of Biomedical Sciences, University of Padova, Padova, Italy
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9
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Rossi AM, Taylor CW. IP3 receptors – lessons from analyses ex cellula. J Cell Sci 2018; 132:132/4/jcs222463. [DOI: 10.1242/jcs.222463] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
ABSTRACT
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are widely expressed intracellular channels that release Ca2+ from the endoplasmic reticulum (ER). We review how studies of IP3Rs removed from their intracellular environment (‘ex cellula’), alongside similar analyses of ryanodine receptors, have contributed to understanding IP3R behaviour. Analyses of permeabilized cells have demonstrated that the ER is the major intracellular Ca2+ store, and that IP3 stimulates Ca2+ release from this store. Radioligand binding confirmed that the 4,5-phosphates of IP3 are essential for activating IP3Rs, and facilitated IP3R purification and cloning, which paved the way for structural analyses. Reconstitution of IP3Rs into lipid bilayers and patch-clamp recording from the nuclear envelope have established that IP3Rs have a large conductance and select weakly between Ca2+ and other cations. Structural analyses are now revealing how IP3 binding to the N-terminus of the tetrameric IP3R opens the pore ∼7 nm away from the IP3-binding core (IBC). Communication between the IBC and pore passes through a nexus of interleaved domains contributed by structures associated with the pore and cytosolic domains, which together contribute to a Ca2+-binding site. These structural analyses provide evidence to support the suggestion that IP3 gates IP3Rs by first stimulating Ca2+ binding, which leads to pore opening and Ca2+ release.
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Affiliation(s)
- Ana M. Rossi
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W. Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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10
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Yang L, Gu W, Cheung KH, Yan L, Tong BCK, Jiang Y, Yang J. InsP 3R-SEC5 interaction on phagosomes modulates innate immunity to Candida albicans by promoting cytosolic Ca 2+ elevation and TBK1 activity. BMC Biol 2018; 16:46. [PMID: 29703257 PMCID: PMC5921305 DOI: 10.1186/s12915-018-0507-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 03/20/2018] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Candida albicans (C. albicans) invasion triggers antifungal innate immunity, and the elevation of cytoplasmic Ca2+ levels via the inositol 1,4,5-trisphosphate receptor (InsP3R) plays a critical role in this process. However, the molecular pathways linking the InsP3R-mediated increase in Ca2+ and immune responses remain elusive. RESULTS In the present study, we find that during C. albicans phagocytosis in macrophages, exocyst complex component 2 (SEC5) promotes InsP3R channel activity by binding to its C-terminal α-helix (H1), increasing cytosolic Ca2+ concentrations ([Ca2+]c). Immunofluorescence reveals enriched InsP3R-SEC5 complex formation on phagosomes, while disruption of the InsP3R-SEC5 interaction by recombinant H1 peptides attenuates the InsP3R-mediated Ca2+ elevation, leading to impaired phagocytosis. Furthermore, we show that C. albicans infection promotes the recruitment of Tank-binding kinase 1 (TBK1) by the InsP3R-SEC5 interacting complex, leading to the activation of TBK1. Subsequently, activated TBK1 phosphorylates interferon regulatory factor 3 (IRF-3) and mediates type I interferon responses, suggesting that the InsP3R-SEC5 interaction may regulate antifungal innate immune responses not only by elevating cytoplasmic Ca2+ but also by activating the TBK1-IRF-3 pathway. CONCLUSIONS Our data have revealed an important role of the InsP3R-SEC5 interaction in innate immune responses against C. albicans.
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Affiliation(s)
- Long Yang
- School of Pharmacy, Second Military Medical University, 325 Guohe Road, Shanghai, 200433, China.,Jinan Military General Hospital, 25 Shifan Road, Jinan, 250031, China
| | - Wenwen Gu
- NHFPC Key Laboratory of Reproduction Regulation, Shanghai Institute of Planned Parenthood Research, 2140 Xie Tu Road, Shanghai, 200032, China
| | - King-Ho Cheung
- School of Chinese Medicine, Hong Kong Baptist University, Hong Kong SAR, China
| | - Lan Yan
- School of Pharmacy, Second Military Medical University, 325 Guohe Road, Shanghai, 200433, China
| | | | - Yuanying Jiang
- School of Pharmacy, Second Military Medical University, 325 Guohe Road, Shanghai, 200433, China. .,School of Medicine, Tongji University, Shanghai, 200433, China.
| | - Jun Yang
- NHFPC Key Laboratory of Reproduction Regulation, Shanghai Institute of Planned Parenthood Research, 2140 Xie Tu Road, Shanghai, 200032, China.
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11
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Toglia P, Ullah G, Pearson JE. Analyzing optical imaging of Ca 2+ signals via TIRF microscopy: The limits on resolution due to chemical rates and depth of the channels. Cell Calcium 2017; 67:65-73. [PMID: 29029792 DOI: 10.1016/j.ceca.2017.08.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/22/2017] [Accepted: 08/23/2017] [Indexed: 11/17/2022]
Abstract
High resolution total internal reflection (TIRF) microscopy (TIRFM) together with detailed computational modeling provides a powerful approach towards the understanding of a wide range of Ca2+ signals mediated by the ubiquitous inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) channel. Exploiting this fruitful collaboration further requires close agreement between the models and observations. However, elementary Ca2+ release events, puffs, imaged through TIRFM do not show the rapid single-channel openings and closings during and between puffs as are present in simulated puffs using data-driven single channel models. TIRFM also shows a rapid equilibration of 10ms after a channel opens or closes which is not achievable in simulation using standard Ca2+ diffusion coefficients and reaction rates between indicator dye and Ca2+. Furthermore, TIRFM imaging cannot decipher the depth of the channel with respect to the microscope, which will affect the change in fluorescence that the microscope detects, thereby affecting its sensitivity to fast single-channel activity. Using the widely used Ca2+ diffusion coefficients and reaction rates, our simulations show equilibration rates that are eight times slower than TIRFM imaging. We show that to get equilibrium rates consistent with observed values, the diffusion coefficients and reaction rates have to be significantly higher than the values reported in the literature, and predict the channel depth to be 200-250nm. Finally, we show that with the addition of noise, short events due to 1-2ms opening and closing of channels that are observed in computational models can be missed in TIRFM.
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Affiliation(s)
- Patrick Toglia
- Department of Physics, University of South Florida, Tampa, FL 33620, USA
| | - Ghanim Ullah
- Department of Physics, University of South Florida, Tampa, FL 33620, USA.
| | - John E Pearson
- T-6 Theoretical Biology and Biophysics Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
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12
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Characterization of Two-Pore Channel 2 by Nuclear Membrane Electrophysiology. Sci Rep 2016; 6:20282. [PMID: 26838264 PMCID: PMC4738322 DOI: 10.1038/srep20282] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Accepted: 12/30/2015] [Indexed: 02/07/2023] Open
Abstract
Lysosomal calcium (Ca2+) release mediated by NAADP triggers signalling cascades that regulate many cellular processes. The identification of two-pore channel 2 (TPC2) as the NAADP receptor advances our understanding of lysosomal Ca2+ signalling, yet the lysosome is not amenable to traditional patch-clamp electrophysiology. Previous attempts to record TPC2 single-channel activity put TPC2 outside its native environment, which not reflect TPC2’s true physiological properties. To test the feasibility of using nuclear membrane electrophysiology for TPC2 channel characterization, we constructed a stable human TPC2-expressing DT40TKO cell line that lacks endogenous InsP3R and RyR (DT40TKO-hTPC2). Immunostaining revealed hTPC2 expression on the ER and nuclear envelope. Intracellular dialysis of NAADP into Fura-2-loaded DT40TKO-hTPC2 cells elicited cytosolic Ca2+ transients, suggesting that hTPC2 was functionally active. Using nuclear membrane electrophysiology, we detected a ~220 pS single-channel current activated by NAADP with K+ as the permeant ion. The detected single-channel recordings displayed a linear current-voltage relationship, were sensitive to Ned-19 inhibition, were biphasically regulated by NAADP concentration, and regulated by PKA phosphorylation. In summary, we developed a cell model for the characterization of the TPC2 channel and the nuclear membrane patch-clamp technique provided an alternative approach to rigorously investigate the electrophysiological properties of TPC2 with minimal manipulation.
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13
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Yarotskyy V, Dirksen RT. Monovalent cationic channel activity in the inner membrane of nuclei from skeletal muscle fibers. Biophys J 2015; 107:2027-36. [PMID: 25418088 DOI: 10.1016/j.bpj.2014.09.030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 09/24/2014] [Accepted: 09/30/2014] [Indexed: 12/28/2022] Open
Abstract
Nuclear ion channels remain among the least studied and biophysically characterized channels. Although considerable progress has been made in characterizing calcium release channels in the nuclear membrane, very little is known regarding the properties of nuclear monovalent cationic channels. Here, we describe a method to isolate nuclei from adult skeletal muscle fibers that are suitable for electrophysiological experiments. Using this approach, we show for the first time, to our knowledge, that a nuclear monovalent cationic channel (NMCC) is prominently expressed in the inner membrane of nuclei isolated from flexor digitorum brevis skeletal muscle fibers of adult mice. In isotonic 140 mM KCl, the skeletal muscle NMCC exhibits a unitary conductance of ?160 pS and high, voltage-independent open probability. Based on single-channel reversal potential measurements, NMCCs are slightly more permeable to potassium ions over sodium (PK/PNa = 2.68 ± 0.21) and cesium (PK/PCs = 1.39 ± 0.03) ions. In addition, NMCCs do not permeate divalent cations, are inhibited by calcium ions, and demonstrate weak rectification in asymmetric Ca(2+)-containing solutions. Together, these studies characterize a voltage-independent NMCC in skeletal muscle, the properties of which are ideally suited to serve as a countercurrent mechanism during calcium release from the nuclear envelope.
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Affiliation(s)
- Viktor Yarotskyy
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York.
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York
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14
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Xu H, Martinoia E, Szabo I. Organellar channels and transporters. Cell Calcium 2015; 58:1-10. [PMID: 25795199 DOI: 10.1016/j.ceca.2015.02.006] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 02/20/2015] [Indexed: 12/22/2022]
Abstract
Decades of intensive research have led to the discovery of most plasma membrane ion channels and transporters and the characterization of their physiological functions. In contrast, although over 80% of transport processes occur inside the cells, the ion flux mechanisms across intracellular membranes (the endoplasmic reticulum, Golgi apparatus, endosomes, lysosomes, mitochondria, chloroplasts, and vacuoles) are difficult to investigate and remain poorly understood. Recent technical advances in super-resolution microscopy, organellar electrophysiology, organelle-targeted fluorescence imaging, and organelle proteomics have pushed a large step forward in the research of intracellular ion transport. Many new organellar channels are molecularly identified and electrophysiologically characterized. Additionally, molecular identification of many of these ion channels/transporters has made it possible to study their physiological functions by genetic and pharmacological means. For example, organellar channels have been shown to regulate important cellular processes such as programmed cell death and photosynthesis, and are involved in many different pathologies. This special issue (SI) on organellar channels and transporters aims to provide a forum to discuss the recent advances and to define the standard and open questions in this exciting and rapidly developing field. Along this line, a new Gordon Research Conference dedicated to the multidisciplinary study of intracellular membrane transport proteins will be launched this coming summer.
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Affiliation(s)
- Haoxing Xu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 3089 Natural Science Building (Kraus), 830 North University Avenue, Ann Arbor, MI 48109-1048, USA.
| | - Enrico Martinoia
- Institute of Plant Biology, University of Zürich, Zollikerstr. 107, CH-8008 Zürich, Switzerland.
| | - Ildiko Szabo
- Department of Biology, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy; CNR Neuroscience Institute, Viale G. Colombo 3, 35121 Padova, Italy.
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Mak DOD, Foskett JK. Inositol 1,4,5-trisphosphate receptors in the endoplasmic reticulum: A single-channel point of view. Cell Calcium 2014; 58:67-78. [PMID: 25555684 DOI: 10.1016/j.ceca.2014.12.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 12/09/2014] [Accepted: 12/10/2014] [Indexed: 10/24/2022]
Abstract
As an intracellular Ca(2+) release channel at the endoplasmic reticulum membrane, the ubiquitous inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) plays a crucial role in the generation, propagation and regulation of intracellular Ca(2+) signals that regulate numerous physiological and pathophysiological processes. This review provides a concise account of the fundamental single-channel properties of the InsP3R channel: its conductance properties and its regulation by InsP3 and Ca(2+), its physiological ligands, studied using nuclear patch clamp electrophysiology.
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Affiliation(s)
- Don-On Daniel Mak
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
| | - J Kevin Foskett
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States; Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
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General anesthetic isoflurane modulates inositol 1,4,5-trisphosphate receptor calcium channel opening. Anesthesiology 2014; 121:528-37. [PMID: 24878495 DOI: 10.1097/aln.0000000000000316] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Pharmacological evidence suggests that inhalational general anesthetics induce neurodegeneration in vitro and in vivo through overactivation of inositol trisphosphate receptor (InsP3R) Ca-release channels, but it is not clear whether these effects are due to direct modulation of channel activity by the anesthetics. METHODS Using single-channel patch clamp electrophysiology, the authors examined the gating of rat recombinant type 3 InsP3R (InsP3R-3) Ca-release channels in isolated nuclei (N = 3 to 15) from chicken lymphocytes modulated by isoflurane at clinically relevant concentrations in the absence and presence of physiological levels of the agonist inositol 1,4,5-trisphosphate (InsP3). The authors also examined the effects of isoflurane on InsP3R-mediated Ca release from the endoplasmic reticulum and changes in intracellular Ca concentration ([Ca]i). RESULTS Clinically relevant concentrations (approximately 1 minimal alveolar concentration) of the commonly used general anesthetic, isoflurane, activated InsP3R-3 channels with open probability similar to channels activated by 1 µM InsP3 (Po ≈ 0.2). This isoflurane modulation of InsP3R-3 Po depended biphasically on [Ca]i. Combination of isoflurane with subsaturating levels of InsP3 in patch pipettes resulted in at least two-fold augmentations of InsP3R-3 channel Po compared with InsP3 alone. These effects were not noted in the presence of saturating [InsP3]. Application of isoflurane to DT40 cells resulted in a 30% amplification of InsP3R-mediated [Ca]i oscillations, whereas InsP3-induced increase in [Ca]i and cleaved caspase-3 activity were enhanced by approximately 2.5-fold. CONCLUSION These results suggest that the InsP3R may be a direct molecular target of isoflurane and plays a role in the mechanisms of anesthetic-mediated pharmacological or neurotoxic effects.
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Wagner LE, Groom LA, Dirksen RT, Yule DI. Characterization of ryanodine receptor type 1 single channel activity using "on-nucleus" patch clamp. Cell Calcium 2014; 56:96-107. [PMID: 24972488 DOI: 10.1016/j.ceca.2014.05.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 05/27/2014] [Accepted: 05/28/2014] [Indexed: 12/13/2022]
Abstract
In this study, we provide the first description of the biophysical and pharmacological properties of ryanodine receptor type 1 (RyR1) expressed in a native membrane using the on-nucleus configuration of the patch clamp technique. A stable cell line expressing rabbit RyR1 was established (HEK-RyR1) using the FLP-in 293 cell system. In contrast to untransfected cells, RyR1 expression was readily demonstrated by immunoblotting and immunocytochemistry in HEK-RyR1 cells. In addition, the RyR1 agonists 4-CMC and caffeine activated Ca(2+) release that was inhibited by high concentrations of ryanodine. On nucleus patch clamp was performed in nuclei prepared from HEK-RyR1 cells. Raising the [Ca(2+)] in the patch pipette resulted in the appearance of a large conductance cation channel with well resolved kinetics and the absence of prominent subconductance states. Current versus voltage relationships were ohmic and revealed a chord conductance of ∼750pS or 450pS in symmetrical 250mM KCl or CsCl, respectively. The channel activity was markedly enhanced by caffeine and exposure to ryanodine resulted in the appearance of a subconductance state with a conductance ∼40% of the full channel opening with a Po near unity. In total, these properties are entirely consistent with RyR1 channel activity. Exposure of RyR1 channels to cyclic ADP ribose (cADPr), nicotinic acid adenine dinucleotide phosphate (NAADP) or dantrolene did not alter the single channel activity stimulated by Ca(2+), and thus, it is unlikely these molecules directly modulate RyR1 channel activity. In summary, we describe an experimental platform to monitor the single channel properties of RyR channels. We envision that this system will be influential in characterizing disease-associated RyR mutations and the molecular determinants of RyR channel modulation.
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Affiliation(s)
- Larry E Wagner
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Ave, Rochester, NY 14642, United States
| | - Linda A Groom
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Ave, Rochester, NY 14642, United States
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Ave, Rochester, NY 14642, United States
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Ave, Rochester, NY 14642, United States.
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Bezprozvanny I. Bilayer measurement of endoplasmic reticulum Ca2+ channels. Cold Spring Harb Protoc 2013; 2013:2013/11/pdb.top066225. [PMID: 24184754 DOI: 10.1101/pdb.top066225] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Reconstitution of ion channels into planar lipid bilayers (also called black lipid membranes or BLM) is the most widely used method to conduct physiological studies of intracellular ion channels, including endoplasmic reticulum (ER) calcium (Ca(2+)) channels. The two main types of Ca(2+) release channels in the ER membrane are ryanodine receptors (RyanRs) and inositol(1,4,5)-trisphosphate receptors (InsP3Rs). Use of the BLM reconstitution technique enabled the initial description of the functional properties of InsP3R and RyanR at the single-channel level more than 20 years ago. Since then, BLM reconstitution methods have been used to study physiological modulation and to perform structure-function analysis of these channels, and to study pathological changes in the function of InsP3R and RyanR in various disease states. The BLM technique has also been useful for studies of other intracellular Ca(2+) channels, such as ER Ca(2+) leak presenilin channels and NAADP-gated lysosomal Ca(2+) channels encoded by TPC2. In this article, basic protocols used for BLM studies of ER Ca(2+) channels are introduced.
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Affiliation(s)
- Ilya Bezprozvanny
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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Mak DOD, Vais H, Cheung KH, Foskett JK. Nuclear patch-clamp electrophysiology of Ca2+ channels. Cold Spring Harb Protoc 2013; 2013:885-91. [PMID: 24003194 DOI: 10.1101/pdb.prot073064] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Patch-clamping the outer or inner nuclear membrane of isolated nuclei is very similar to patch-clamping the plasma membrane of isolated cells. This protocol describes in detail all the steps required to successfully obtain nuclear membrane patches, in various configurations, from both the outer and inner nuclear membranes of isolated nuclei.
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Affiliation(s)
- Don-On Daniel Mak
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Mak DOD, Vais H, Cheung KH, Foskett JK. Isolating nuclei from cultured cells for patch-clamp electrophysiology of intracellular Ca(2+) channels. Cold Spring Harb Protoc 2013; 2013:880-4. [PMID: 24003193 DOI: 10.1101/pdb.prot073056] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Nuclear patch-clamp experiments can be performed with intact nuclei or with nuclei from which the outer nuclear membrane has been removed. This protocol presents procedures for harvesting different types of cultured cells, isolating nuclei, and exposing the inner nuclear membrane by agitating in the presence of sodium citrate. Particulars about obtaining and maintaining the cells of interest in culture are not described here. However, care should be taken not to allow the cells to grow beyond a density of 2-3 × 10(6) cells/mL because this may decrease both the cell viability and the success rate of detecting active inositol 1,4,5-trisphosphate receptor (InsP3R) channels in nuclear patches.
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Affiliation(s)
- Don-On Daniel Mak
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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