1
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Klier PEZ, Roo R, Miller EW. Fluorescent indicators for imaging membrane potential of organelles. Curr Opin Chem Biol 2022; 71:102203. [PMID: 36084425 PMCID: PMC10259174 DOI: 10.1016/j.cbpa.2022.102203] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/18/2022] [Accepted: 07/21/2022] [Indexed: 01/27/2023]
Abstract
Plasma membrane potential is a key driver of the physiology of excitable cells like neurons and cardiomyocytes. Voltage-sensitive fluorescent indicators offer a powerful complement to traditional electrode-based approaches to measuring and monitoring membrane potential. Intracellular organelles can also generate membrane potential, yet the electrode- and fluorescent indicator-based approaches used for plasma membrane potential imaging are difficult to implement on intact organelles in their native environment. Here, we survey recent advances in developing and deploying voltage-sensitive fluorescent indicators to interrogate organelle membrane potential in intact cells.
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Affiliation(s)
- Pavel E Z Klier
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
| | - Ryan Roo
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
| | - Evan W Miller
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA; Department of Molecular & Cell Biology, University of California, Berkeley, CA, 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, CA, 94720, USA.
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2
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Methods of Measuring Mitochondrial Potassium Channels: A Critical Assessment. Int J Mol Sci 2022; 23:ijms23031210. [PMID: 35163132 PMCID: PMC8835872 DOI: 10.3390/ijms23031210] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 12/22/2022] Open
Abstract
In this paper, the techniques used to study the function of mitochondrial potassium channels are critically reviewed. The majority of these techniques have been known for many years as a result of research on plasma membrane ion channels. Hence, in this review, we focus on the critical evaluation of techniques used in the studies of mitochondrial potassium channels, describing their advantages and limitations. Functional analysis of mitochondrial potassium channels in comparison to that of plasmalemmal channels presents additional experimental challenges. The reliability of functional studies of mitochondrial potassium channels is often affected by the need to isolate mitochondria and by functional properties of mitochondria such as respiration, metabolic activity, swelling capacity, or high electrical potential. Three types of techniques are critically evaluated: electrophysiological techniques, potassium flux measurements, and biochemical techniques related to potassium flux measurements. Finally, new possible approaches to the study of the function of mitochondrial potassium channels are presented. We hope that this review will assist researchers in selecting reliable methods for studying, e.g., the effects of drugs on mitochondrial potassium channel function. Additionally, this review should aid in the critical evaluation of the results reported in various articles on mitochondrial potassium channels.
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3
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Mnatsakanyan N, Jonas EA. ATP synthase c-subunit ring as the channel of mitochondrial permeability transition: Regulator of metabolism in development and degeneration. J Mol Cell Cardiol 2020; 144:109-118. [PMID: 32461058 PMCID: PMC7877492 DOI: 10.1016/j.yjmcc.2020.05.013] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 05/07/2020] [Accepted: 05/20/2020] [Indexed: 12/29/2022]
Abstract
The mitochondrial permeability transition pore (mPTP) or mitochondrial megachannel is arguably one of the most mysterious phenomena in biology today. mPTP has been at the center of ongoing extensive scientific research for the last several decades. In this review we will discuss recent advances in the field that enhance our understanding of the molecular composition of mPTP, its regulatory mechanisms and its pathophysiological role. We will describe our recent findings on the role of ATP synthase c-subunit ring as a central player in mitochondrial permeability transition and as an important metabolic regulator during development and in degenerative diseases.
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Affiliation(s)
- Nelli Mnatsakanyan
- Section of Endocrinology, Department of Internal Medicine, Yale University, New Haven, CT, USA.
| | - Elizabeth Ann Jonas
- Section of Endocrinology, Department of Internal Medicine, Yale University, New Haven, CT, USA.
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4
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Carmeliet E. From Bernstein's rheotome to Neher-Sakmann's patch electrode. The action potential. Physiol Rep 2019; 7:e13861. [PMID: 30604910 PMCID: PMC6316177 DOI: 10.14814/phy2.13861] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 07/10/2018] [Accepted: 07/28/2018] [Indexed: 01/08/2023] Open
Abstract
The aim of this review was to provide an overview of the most important stages in the development of cellular electrophysiology. The period covered starts with Bernstein's formulation of the membrane hypothesis and the measurement of the nerve and muscle action potential. Technical innovations make discoveries possible. This was the case with the use of the squid giant axon, allowing the insertion of "large" intracellular electrodes and derivation of transmembrane potentials. Application of the newly developed voltage clamp method for measuring ionic currents, resulted in the formulation of the ionic theory. At the same time transmembrane measurements were made possible in smaller cells by the introduction of the microelectrode. An improvement of this electrode was the next major (r)evolution. The patch electrode made it possible to descend to the molecular level and record single ionic channel activity. The patch technique has been proven to be exceptionally versatile. In its whole-cell configuration it was the solution to measure voltage clamp currents in small cells. See also: https://doi.org/10.14814/phy2.13860 & https://doi.org/10.14814/phy2.13862.
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5
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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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6
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Gunderson CG, Peng Z, Zhang B. Collision and Coalescence of Single Attoliter Oil Droplets on a Pipet Nanopore. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:2699-2707. [PMID: 29400980 DOI: 10.1021/acs.langmuir.7b04090] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We describe the use of a quartz pipet nanopore to study the collision and coalescence of individual emulsion oil droplets and their subsequent nanopore translocation. Collision and coalescence of single toluene droplets at a nanopore orifice are driven primarily by electroosmosis and electrophoresis and lead to the fast growth of a trapped oil droplet. This results in a stepwise current response due to the coalesced oil droplet increasing its volume and its ability to partially block the nanopore's ionic current, allowing us to use the resistive-pulse method to resolve single droplet collisions. Further growth of the trapped oil droplet leads to a complete blockage of the nanopore and a nearly 100% current decay. The trapped oil droplet shows enormous mechanical stability at lower voltages and stays in its trapped status for hundreds of seconds. An increased voltage can be used to drive the trapped droplet into the pipet pore within several milliseconds. Simultaneous fluorescence imaging and amperometry were performed to examine droplet collision, coalescence, and translocation, further confirming the proposed mechanism of droplet-nanopore interaction. Moreover, we demonstrate the unique ability to perform fast voltammetric measurements on a nanopore-supported attoliter oil droplet and study its voltage-driven ion transfer processes.
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Affiliation(s)
- Christopher G Gunderson
- Department of Chemistry, University of Washington , Seattle, Washington 98195, United States
| | - Zhuoyu Peng
- Department of Chemistry, University of Washington , Seattle, Washington 98195, United States
| | - Bo Zhang
- Department of Chemistry, University of Washington , Seattle, Washington 98195, United States
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7
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Affiliation(s)
- Ede A Rancz
- Cortical Circuits Laboratory, Francis Crick Institute, London, UK
| | - Andreas T Schaefer
- Neurophysiology of Behaviour Laboratory, Francis Crick Institute, London, UK, and the Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK
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8
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Shapovalov G, Ritaine A, Bidaux G, Slomianny C, Borowiec AS, Gordienko D, Bultynck G, Skryma R, Prevarskaya N. Organelle membrane derived patches: reshaping classical methods for new targets. Sci Rep 2017; 7:14082. [PMID: 29074990 PMCID: PMC5658434 DOI: 10.1038/s41598-017-13968-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 10/04/2017] [Indexed: 12/12/2022] Open
Abstract
Intracellular ion channels are involved in multiple signaling processes, including such crucial ones as regulation of cellular motility and fate. With 95% of the cellular membrane belonging to intracellular organelles, it is hard to overestimate the importance of intracellular ion channels. Multiple studies have been performed on these channels over the years, however, a unified approach allowing not only to characterize their activity but also to study their regulation by partner proteins, analogous to the patch clamp “golden standard”, is lacking. Here, we present a universal approach that combines the extraction of intracellular membrane fractions with the preparation of patchable substrates that allows to characterize these channels in endogenous protein environment and to study their regulation by partner proteins. We validate this method by characterizing activity of multiple intracellular ion channels localized to different organelles and by providing detailed electrophysiological characterization of the regulation of IP3R activity by endogenous Bcl-2. Thus, after synthesis and reshaping of the well-established approaches, organelle membrane derived patch clamp provides the means to assess ion channels from arbitrary cellular membranes at the single channel level.
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Affiliation(s)
- George Shapovalov
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Abigaël Ritaine
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Gabriel Bidaux
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France.,Laboratoire INSERM U1060, CarMeN Laboratory, Claude Bernard Lyon 1 University, 8, avenue Rockfeller, F-69373, Lyon, France
| | - Christian Slomianny
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Anne-Sophie Borowiec
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France.,Laboratoire INSERM U1060, CarMeN Laboratory, Claude Bernard Lyon 1 University, 8, avenue Rockfeller, F-69373, Lyon, France
| | - Dmitri Gordienko
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Herestraat 49, BE-3000, Leuven, Belgium
| | - Roman Skryma
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Natalia Prevarskaya
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France. .,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France.
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9
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Mnatsakanyan N, Beutner G, Porter GA, Alavian KN, Jonas EA. Physiological roles of the mitochondrial permeability transition pore. J Bioenerg Biomembr 2017; 49:13-25. [PMID: 26868013 PMCID: PMC4981558 DOI: 10.1007/s10863-016-9652-1] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 02/04/2016] [Indexed: 01/01/2023]
Abstract
Neurons experience high metabolic demand during such processes as synaptic vesicle recycling, membrane potential maintenance and Ca2+ exchange/extrusion. The energy needs of these events are met in large part by mitochondrial production of ATP through the process of oxidative phosphorylation. The job of ATP production by the mitochondria is performed by the F1FO ATP synthase, a multi-protein enzyme that contains a membrane-inserted portion, an extra-membranous enzymatic portion and an extensive regulatory complex. Although required for ATP production by mitochondria, recent findings have confirmed that the membrane-confined portion of the c-subunit of the ATP synthase also houses a large conductance uncoupling channel, the mitochondrial permeability transition pore (mPTP), the persistent opening of which produces osmotic dysregulation of the inner mitochondrial membrane, uncoupling of oxidative phosphorylation and cell death. Recent advances in understanding the molecular components of mPTP and its regulatory mechanisms have determined that decreased uncoupling occurs in states of enhanced mitochondrial efficiency; relative closure of mPTP therefore contributes to cellular functions as diverse as cardiac development and synaptic efficacy.
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Affiliation(s)
- Nelli Mnatsakanyan
- Department Internal Medicine, Section of Endocrinology, Yale University, New Haven, CT, USA
| | - Gisela Beutner
- Department of Pediatrics (Cardiology), University of Rochester Medical Center, Rochester, NY, USA
| | - George A Porter
- Department of Pediatrics (Cardiology), University of Rochester Medical Center, Rochester, NY, USA
| | - Kambiz N Alavian
- Division of Brain Sciences, Department of Medicine, Imperial College London, London, UK
| | - Elizabeth A Jonas
- Department Internal Medicine, Section of Endocrinology, Yale University, New Haven, CT, USA.
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10
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Elustondo PA, Nichols M, Robertson GS, Pavlov EV. Mitochondrial Ca2+ uptake pathways. J Bioenerg Biomembr 2016; 49:113-119. [DOI: 10.1007/s10863-016-9676-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/05/2016] [Indexed: 12/19/2022]
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11
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Perry D, Paulose Nadappuram B, Momotenko D, Voyias PD, Page A, Tripathi G, Frenguelli BG, Unwin PR. Surface Charge Visualization at Viable Living Cells. J Am Chem Soc 2016; 138:3152-60. [DOI: 10.1021/jacs.5b13153] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- David Perry
- Department of Chemistry, ‡MOAC Doctoral Training Centre, §Division of Metabolic and Vascular
Health, Warwick Medical School, and ∥School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Binoy Paulose Nadappuram
- Department of Chemistry, ‡MOAC Doctoral Training Centre, §Division of Metabolic and Vascular
Health, Warwick Medical School, and ∥School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Dmitry Momotenko
- Department of Chemistry, ‡MOAC Doctoral Training Centre, §Division of Metabolic and Vascular
Health, Warwick Medical School, and ∥School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Philip D. Voyias
- Department of Chemistry, ‡MOAC Doctoral Training Centre, §Division of Metabolic and Vascular
Health, Warwick Medical School, and ∥School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Ashley Page
- Department of Chemistry, ‡MOAC Doctoral Training Centre, §Division of Metabolic and Vascular
Health, Warwick Medical School, and ∥School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Gyanendra Tripathi
- Department of Chemistry, ‡MOAC Doctoral Training Centre, §Division of Metabolic and Vascular
Health, Warwick Medical School, and ∥School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Bruno G. Frenguelli
- Department of Chemistry, ‡MOAC Doctoral Training Centre, §Division of Metabolic and Vascular
Health, Warwick Medical School, and ∥School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Patrick R. Unwin
- Department of Chemistry, ‡MOAC Doctoral Training Centre, §Division of Metabolic and Vascular
Health, Warwick Medical School, and ∥School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
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12
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Jonas EA, Porter GA, Beutner G, Mnatsakanyan N, Alavian KN. Cell death disguised: The mitochondrial permeability transition pore as the c-subunit of the F(1)F(O) ATP synthase. Pharmacol Res 2015; 99:382-92. [PMID: 25956324 PMCID: PMC4567435 DOI: 10.1016/j.phrs.2015.04.013] [Citation(s) in RCA: 61] [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: 02/12/2015] [Revised: 04/09/2015] [Accepted: 04/20/2015] [Indexed: 12/16/2022]
Abstract
Ion transport across the mitochondrial inner and outer membranes is central to mitochondrial function, including regulation of oxidative phosphorylation and cell death. Although essential for ATP production by mitochondria, recent findings have confirmed that the c-subunit of the ATP synthase also houses a large conductance uncoupling channel, the mitochondrial permeability transition pore (mPTP), the persistent opening of which produces osmotic dysregulation of the inner mitochondrial membrane and cell death. This review will discuss recent advances in understanding the molecular components of mPTP, its regulatory mechanisms and how these contribute directly to its physiological as well as pathological roles.
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Affiliation(s)
- Elizabeth A Jonas
- Department of Internal Medicine, Section of Endocrinology, Yale University, New Haven, CT, USA.
| | - George A Porter
- Department of Pediatrics (Cardiology), University of Rochester Medical Center, Rochester, NY, USA
| | - Gisela Beutner
- Department of Pediatrics (Cardiology), University of Rochester Medical Center, Rochester, NY, USA
| | - Nelli Mnatsakanyan
- Department of Internal Medicine, Section of Endocrinology, Yale University, New Haven, CT, USA
| | - Kambiz N Alavian
- Division of Brain Sciences, Department of Medicine, Imperial College London, UK
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13
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Jonas EA, Porter GA, Alavian KN. Bcl-xL in neuroprotection and plasticity. Front Physiol 2014; 5:355. [PMID: 25278904 PMCID: PMC4166110 DOI: 10.3389/fphys.2014.00355] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 09/02/2014] [Indexed: 01/14/2023] Open
Abstract
Accepted features of neurodegenerative disease include mitochondrial and protein folding dysfunction and activation of pro-death factors. Neurons that experience high metabolic demand or those found in organisms with genetic mutations in proteins that control cell stress may be more susceptible to aging and neurodegenerative disease. In neurons, events that normally promote growth, synapse formation, and plasticity are also often deployed to control neurotoxicity. Such protective strategies are coordinated by master stress-fighting proteins. One such specialized protein is the anti-cell death Bcl-2 family member Bcl-xL, whose myriad death-protecting functions include enhancement of bioenergetic efficiency, prevention of mitochondrial permeability transition channel activity, protection from mitochondrial outer membrane permeabilization (MOMP) to pro-apoptotic factors, and improvement in the rate of vesicular trafficking. Synapse formation and normal neuronal activity provide protection from neuronal death. Therefore, Bcl-xL brings about synapse formation as a neuroprotective strategy. In this review we will consider how this multi-functional master regulator protein uses many strategies to enhance synaptic and neuronal function and thus counteracts neurodegenerative stimuli.
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Affiliation(s)
- Elizabeth A Jonas
- Section of Endocrinology, Department of Internal Medicine, Yale University New Haven, CT, USA ; Department of Neurobiology, Yale University New Haven, CT, USA
| | - George A Porter
- Departments of Pediatrics (Cardiology), University of Rochester Medical Center Rochester, NY, USA ; Internal Medicine (Aab Cardiovascular Research Institute), University of Rochester Medical Center Rochester, NY, USA ; Department of Pharmacology and Physiology, University of Rochester Medical Center Rochester, NY, USA
| | - Kambiz N Alavian
- Division of Brain Sciences, Department of Medicine, Imperial College London London, UK
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14
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Abstract
The field of mitochondrial ion channels has recently seen substantial progress, including the molecular identification of some of the channels. An integrative approach using genetics, electrophysiology, pharmacology, and cell biology to clarify the roles of these channels has thus become possible. It is by now clear that many of these channels are important for energy supply by the mitochondria and have a major impact on the fate of the entire cell as well. The purpose of this review is to provide an up-to-date overview of the electrophysiological properties, molecular identity, and pathophysiological functions of the mitochondrial ion channels studied so far and to highlight possible therapeutic perspectives based on current information.
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15
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Jonas EA. Contributions of Bcl-xL to acute and long term changes in bioenergetics during neuronal plasticity. Biochim Biophys Acta Mol Basis Dis 2013; 1842:1168-78. [PMID: 24240091 DOI: 10.1016/j.bbadis.2013.11.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 11/05/2013] [Accepted: 11/07/2013] [Indexed: 12/23/2022]
Abstract
Mitochondria manufacture and release metabolites and manage calcium during neuronal activity and synaptic transmission, but whether long term alterations in mitochondrial function contribute to the neuronal plasticity underlying changes in organism behavior patterns is still poorly understood. Although normal neuronal plasticity may determine learning, in contrast a persistent decline in synaptic strength or neuronal excitability may portend neurite retraction and eventual somatic death. Anti-death proteins such as Bcl-xL not only provide neuroprotection at the neuronal soma during cell death stimuli, but also appear to enhance neurotransmitter release and synaptic growth and development. It is proposed that Bcl-xL performs these functions through its ability to regulate mitochondrial release of bioenergetic metabolites and calcium, and through its ability to rapidly alter mitochondrial positioning and morphology. Bcl-xL also interacts with proteins that directly alter synaptic vesicle recycling. Bcl-xL translocates acutely to sub-cellular membranes during neuronal activity to achieve changes in synaptic efficacy. After stressful stimuli, pro-apoptotic cleaved delta N Bcl-xL (ΔN Bcl-xL) induces mitochondrial ion channel activity leading to synaptic depression and this is regulated by caspase activation. During physiological states of decreased synaptic stimulation, loss of mitochondrial Bcl-xL and low level caspase activation occur prior to the onset of long term decline in synaptic efficacy. The degree to which Bcl-xL changes mitochondrial membrane permeability may control the direction of change in synaptic strength. The small molecule Bcl-xL inhibitor ABT-737 has been useful in defining the role of Bcl-xL in synaptic processes. Bcl-xL is crucial to the normal health of neurons and synapses and its malfunction may contribute to neurodegenerative disease.
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Affiliation(s)
- Elizabeth A Jonas
- Dept. of Internal Medicine, P.O. Box 208001, Yale University School of Medicine, New Haven, CT 06520, USA; Dept. of Neurobiology, P.O. Box 208020, Yale University School of Medicine, New Haven, CT 06520, USA.
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16
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Alavian KN, Dworetzky SI, Bonanni L, Zhang P, Sacchetti S, Mariggio MA, Onofrj M, Thomas A, Li H, Mangold JE, Signore AP, Demarco U, Demady DR, Nabili P, Lazrove E, Smith PJS, Gribkoff VK, Jonas EA. Effects of dexpramipexole on brain mitochondrial conductances and cellular bioenergetic efficiency. Brain Res 2012; 1446:1-11. [PMID: 22364637 DOI: 10.1016/j.brainres.2012.01.046] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 01/18/2012] [Indexed: 02/01/2023]
Abstract
Cellular stress or injury can result in mitochondrial dysfunction, which has been linked to many chronic neurological disorders including amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). Stressed and dysfunctional mitochondria exhibit an increase in large conductance mitochondrial membrane currents and a decrease in bioenergetic efficiency. Inefficient energy production puts cells, and particularly neurons, at risk of death when energy demands exceed cellular energy production. Here we show that the candidate ALS drug dexpramipexole (DEX; KNS-760704; ((6R)-4,5,6,7-tetrahydro-N6-propyl-2,6-benzothiazole-diamine) and cyclosporine A (CSA) inhibited increases in ion conductance in whole rat brain-derived mitochondria induced by calcium or treatment with a proteasome inhibitor, although only CSA inhibited calcium-induced permeability transition in liver-derived mitochondria. In several cell lines, including cortical neurons in culture, DEX significantly decreased oxygen consumption while maintaining or increasing production of adenosine triphosphate (ATP). DEX also normalized the metabolic profile of injured cells and was protective against the cytotoxic effects of proteasome inhibition. These data indicate that DEX increases the efficiency of oxidative phosphorylation, possibly by inhibition of a CSA-sensitive mitochondrial conductance.
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Affiliation(s)
- Kambiz N Alavian
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
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17
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Rossi AM, Tovey SC, Rahman T, Prole DL, Taylor CW. Analysis of IP3 receptors in and out of cells. Biochim Biophys Acta Gen Subj 2011; 1820:1214-27. [PMID: 22033379 DOI: 10.1016/j.bbagen.2011.10.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 10/07/2011] [Accepted: 10/08/2011] [Indexed: 10/16/2022]
Abstract
BACKGROUND Inositol 1,4,5-trisphosphate receptors (IP3R) are expressed in almost all animal cells. Three mammalian genes encode closely related IP3R subunits, which assemble into homo- or hetero-tetramers to form intracellular Ca2+ channels. SCOPE OF THE REVIEW In this brief review, we first consider a variety of complementary methods that allow the links between IP3 binding and channel gating to be defined. How does IP3 binding to the IP3-binding core in each IP3R subunit cause opening of a cation-selective pore formed by residues towards the C-terminal? We then describe methods that allow IP3, Ca2+ signals and IP3R mobility to be examined in intact cells. A final section briefly considers genetic analyses of IP3R signalling. MAJOR CONCLUSIONS All IP3R are regulated by both IP3 and Ca2+. This allows them to initiate and regeneratively propagate intracellular Ca2+ signals. The elementary Ca2+ release events evoked by IP3 in intact cells are mediated by very small numbers of active IP3R and the Ca2+-mediated interactions between them. The spatial organization of these Ca2+ signals and their stochastic dependence on so few IP3Rs highlight the need for methods that allow the spatial organization of IP3R signalling to be addressed with single-molecule resolution. GENERAL SIGNIFICANCE A variety of complementary methods provide insight into the structural basis of IP3R activation and the contributions of IP3-evoked Ca2+ signals to cellular physiology. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signaling.
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Rahman T, Taylor CW. Nuclear Patch-Clamp Recording from Inositol 1,4,5-Trisphosphate Receptors. Methods Cell Biol 2010; 99:199-224. [DOI: 10.1016/b978-0-12-374841-6.00008-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Taylor CW, Rahman T, Tovey SC, Dedos SG, Taylor EJA, Velamakanni S. IP3 receptors: some lessons from DT40 cells. Immunol Rev 2009; 231:23-44. [PMID: 19754888 DOI: 10.1111/j.1600-065x.2009.00807.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Inositol-1,4,5-trisphosphate receptors (IP3Rs) are intracellular Ca2+ channels that are regulated by IP3 and Ca2+ and are modulated by many additional signals. These properties allow them to initiate and, via Ca2+-induced Ca2+ release, regeneratively propagate Ca2+ signals evoked by receptors that stimulate formation of IP3. The ubiquitous expression of IP3R highlights their importance, but it also presents problems when attempting to resolve the behavior of defined IP3R. DT40 cells are a pre-B-lymphocyte cell line in which high rates of homologous recombination afford unrivalled opportunities to disrupt endogenous genes. DT40-knockout cells with both alleles of each of the three IP3R genes disrupted provide the only null-background for analysis of homogenous recombinant IP3R. We review the properties of DT40 cells and consider three areas where they have contributed to understanding IP3R behavior. Patch-clamp recording from the nuclear envelope and Ca2+ release from intracellular stores loaded with a low-affinity Ca2+ indicator address the mechanisms leading to activation of IP(3)R. We show that IP3 causes intracellular IP3R to cluster and re-tune their responses to IP3 and Ca2+, better equipping them to mediate regenerative Ca2+ signals. Finally, we show that DT40 cells reliably count very few IP3R into the plasma membrane, where they mediate about half the Ca2+ entry evoked by the B-cell antigen receptor.
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Affiliation(s)
- Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, UK.
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Taylor CW, Pantazaka E. Targeting and clustering of IP3 receptors: key determinants of spatially organized Ca2+ signals. CHAOS (WOODBURY, N.Y.) 2009; 19:037102. [PMID: 19798811 DOI: 10.1063/1.3127593] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3R) are intracellular Ca2+ channels that are almost ubiquitously expressed in animal cells. The spatiotemporal complexity of the Ca2+ signals evoked by IP3R underlies their versatility in cellular signaling. Here we review the mechanisms that contribute to the subcellular targeting of IP3R and the dynamic interplay between IP3R that underpin their ability to generate complex intracellular Ca2+ signals.
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Shemer I, Brinne B, Tegnér J, Grillner S. Electrotonic signals along intracellular membranes may interconnect dendritic spines and nucleus. PLoS Comput Biol 2008; 4:e1000036. [PMID: 18369427 PMCID: PMC2266990 DOI: 10.1371/journal.pcbi.1000036] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2007] [Accepted: 02/13/2008] [Indexed: 11/20/2022] Open
Abstract
Synapses on dendritic spines of pyramidal neurons show a remarkable ability to induce phosphorylation of transcription factors at the nuclear level with a short latency, incompatible with a diffusion process from the dendritic spines to the nucleus. To account for these findings, we formulated a novel extension of the classical cable theory by considering the fact that the endoplasmic reticulum (ER) is an effective charge separator, forming an intrinsic compartment that extends from the spine to the nuclear membrane. We use realistic parameters to show that an electrotonic signal may be transmitted along the ER from the dendritic spines to the nucleus. We found that this type of signal transduction can additionally account for the remarkable ability of the cell nucleus to differentiate between depolarizing synaptic signals that originate from the dendritic spines and back-propagating action potentials. This study considers a novel computational role for dendritic spines, and sheds new light on how spines and ER may jointly create an additional level of processing within the single neuron. Our study incorporates the fact that the endoplasmic reticulum (ER) forms a complete continuum from the spine head to the nuclear envelope and suggests that electrical current flow in a neuron may be better described by a cable-within-a-cable system, where synaptic current flows simultaneously in the medium between the cell membrane and the ER, and within the ER (the internal cable). Our paper provides a novel extension to the classical cable theory (namely, cable-within-cable theory) and presents several interesting predictions. We show that some of these predictions are supported by recent experiments, whereas the principal hypothesis may shed new light on some puzzling observations related to signaling from synapse-to-nucleus. Overall, we show that intracellular-level electrophysiology may introduce principles that appear counter-intuitive with views originating from conventional cellular-level electrophysiology.
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Affiliation(s)
- Isaac Shemer
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
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Hickman JA, Hardwick JM, Kaczmarek LK, Jonas EA. Bcl-xL inhibitor ABT-737 reveals a dual role for Bcl-xL in synaptic transmission. J Neurophysiol 2007; 99:1515-22. [PMID: 18160428 DOI: 10.1152/jn.00598.2007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A role for BCL-xL in regulating neuronal activity is suggested by its dramatic effects on synaptic function and mitochondrial channel activity. When recombinant BCL-xL is injected into the giant presynaptic terminal of squid stellate ganglion or applied directly to mitochondrial outer membranes within the living terminal, it potentiates synaptic transmission acutely, and it produces mitochondrial channel activity. The squid, however, is a genetically intractable model, making it difficult to apply genetic tools in squid to explore the role of endogenous BCL-xL in synaptic function. Therefore the small molecule inhibitor ABT-737, a mimetic of the BH3-only protein BAD, binding to the BH3-binding domain pocket, was tested in squid, revealing a dual role for BCL-xL. ABT-737 slowed recovery of synaptic responses after repetitive synaptic activity, indicating that endogenous BCL-xL is necessary for timely recovery of rapidly firing synapses. Unexpectedly, however, ABT-737 also protected neurons from hypoxia-induced synaptic rundown and from increased permeability of the mitochondrial outer membrane during hypoxia. This implies that endogenous BCL-xL or a modified form of BCL-xL, such as the N-truncated, proteolytic, pro-apoptotic cleavage product, DeltaN BCL-xL, contributes to injurious responses of the hypoxic synapse. To determine if ABT-737 is also an inhibitor of DeltaN BCL-xL, recombinant DeltaN BCL-xL protein was injected into the synapse. ABT-737 potently inhibited synaptic rundown induced by recombinant DeltaN BCL-xL. These observations support the possibility that endogenous proteolysis or a functionally equivalent modification of BCL-xL is responsible for the deleterious effects of hypoxia on synaptic activity.
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Affiliation(s)
- John A Hickman
- Institut de Recherches Servier, Croissy sur Seine, France
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Abstract
The inositol 1,4,5-trisphosphate (InsP3) receptors (InsP3Rs) are a family of Ca2+ release channels localized predominately in the endoplasmic reticulum of all cell types. They function to release Ca2+ into the cytoplasm in response to InsP3 produced by diverse stimuli, generating complex local and global Ca2+ signals that regulate numerous cell physiological processes ranging from gene transcription to secretion to learning and memory. The InsP3R is a calcium-selective cation channel whose gating is regulated not only by InsP3, but by other ligands as well, in particular cytoplasmic Ca2+. Over the last decade, detailed quantitative studies of InsP3R channel function and its regulation by ligands and interacting proteins have provided new insights into a remarkable richness of channel regulation and of the structural aspects that underlie signal transduction and permeation. Here, we focus on these developments and review and synthesize the literature regarding the structure and single-channel properties of the InsP3R.
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Affiliation(s)
- J Kevin Foskett
- Department of Physiology, University of Pennsylvania, Philadelphia 19104-6085, USA.
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24
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Jonas EA, Hardwick JM, Kaczmarek LK. Actions of BAX on mitochondrial channel activity and on synaptic transmission. Antioxid Redox Signal 2005; 7:1092-100. [PMID: 16115013 DOI: 10.1089/ars.2005.7.1092] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Changes in mitochondrial architecture and permeability facilitate programmed cell death. The BCL-2 family protein BAX is implicated in the formation of large "death channels" in outer mitochondrial membranes. We found that BAX-induced channels on mitochondria may have alternative functions. By patch clamping mitochondrial membranes inside the presynaptic terminal of the living squid giant synapse, we made direct measurements of channel activity produced by BAX application. Only infrequently did BAX application result in large conductance channels similar to those produced by a proapoptotic BCL-xL fragment or by application of a BH3-only peptide. Instead, the majority of outer mitochondrial channels induced by BAX had much smaller conductances than those found previously for the proapoptotic protein. Injection of BAX into the presynaptic terminal did not abolish synaptic transmission, contrary to previous findings with the proapoptotic fragment of BCL-xL. Instead, injection of BAX caused an increase in neurotransmitter release, as has also been found for the full-length antiapoptotic BCL-xL protein. We suggest that BAX can act to enhance synaptic efficacy in a normal physiological setting. Furthermore, the occasional large openings may reflect the function of "activated" BAX either to facilitate cell death or to play a physiological role in decreasing synaptic activity.
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Affiliation(s)
- Elizabeth A Jonas
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA.
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Abstract
Mitochondria are abundant within neuronal presynaptic terminals, where they provide energy for sustained neurotransmitter secretion. Injection of Bcl-xL protein into squid giant presynaptic terminal potentiates neurotransmitter release, while a naturally occurring, proteolytic fragment of BCL-xL causes rundown of synaptic function. The cleaved form of BCL-xL generates large, multiconductance ion channel activity in synaptic mitochondrial outer membranes. A rapid onset of synaptic rundown can also be produced by depriving the synapse of oxygen, and hypoxia also induces large channel activity in mitochondrial outer membranes. Channel activity induced by cleaved BCL-xL or by hypoxia is attenuated by NADH, an inhibitor of the voltage-dependent anion channel (VDAC) of mitochondrial outer membranes. Finally, the large conductances elicited by hypoxia are prevented by the addition of a protease inhibitor that prevents cleavage of BCL-xL. The opposing activities of BCL-xL and its proteolytic fragment may regulate the release of ATP from mitochondria during synaptic transmission.
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Affiliation(s)
- Elizabeth Jonas
- Department of Internal Medicine (Endocrinology), Yale University School of Medicine, 333 Cedar St., PO Box 208020, New Haven, Connecticut 06520, USA.
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26
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Jonas EA, Hickman JA, Hardwick JM, Kaczmarek LK. Exposure to hypoxia rapidly induces mitochondrial channel activity within a living synapse. J Biol Chem 2004; 280:4491-7. [PMID: 15561723 DOI: 10.1074/jbc.m410661200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
One of the earliest effects of hypoxia on neuronal function is to produce a run-down of synaptic transmission, and more prolonged hypoxia results in neuronal death. An increase in the permeability of the outer mitochondrial membrane, controlled by BCL-2 family proteins, occurs in response to stimuli that trigger cell death. By patch clamping mitochondrial membranes inside the presynaptic terminal of a squid giant synapse, we have now found that several minutes of hypoxia trigger the opening of large multiconductance channels. The channel activity is induced concurrently with the attenuation of synaptic responses that occurs under hypoxic conditions. Hypoxia-induced channels are inhibited by NADH, an agent that inhibits large conductance channels produced by a pro-apoptotic fragment of BCL-xL in these synaptic mitochondria. The appearance of hypoxia-induced channels was also prevented by the caspase/cysteine protease inhibitor benzyloxycarbonyl-VAD-fluoromethyl ketone (Z-VAD-fmk), which inhibits proteolysis of BCL-xL during hypoxia. Both NADH and Z-VAD-fmk reduced significantly the rate of decline of synaptic responses during hypoxia. Our results indicate that an increase in outer mitochondrial channel activity is a very early event in the response of neurons to hypoxia and suggest that this increase in activity may contribute to the decline in synaptic function during hypoxia.
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Affiliation(s)
- Elizabeth A Jonas
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
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27
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Jonas EA, Hickman JA, Chachar M, Polster BM, Brandt TA, Fannjiang Y, Ivanovska I, Basañez G, Kinnally KW, Zimmerberg J, Hardwick JM, Kaczmarek LK. Proapoptotic N-truncated BCL-xL protein activates endogenous mitochondrial channels in living synaptic terminals. Proc Natl Acad Sci U S A 2004; 101:13590-5. [PMID: 15342906 PMCID: PMC518799 DOI: 10.1073/pnas.0401372101] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Neuronal death is often preceded by functional alterations at nerve terminals. Anti- and proapoptotic BCL-2 family proteins not only regulate the neuronal death pathway but also affect excitability of healthy neurons. We found that exposure of squid stellate ganglia to hypoxia, a death stimulus for neurons, causes a cysteine protease-dependent loss of full-length antiapoptotic BCL-xL, similar to previous findings in mammalian cells. Therefore, to determine the direct effect of the naturally occurring proapoptotic cleavage product of BCL-xL on mitochondria, recombinant N-truncated BCL-xL was applied to mitochondria inside the squid presynaptic terminal and to purified mitochondria isolated from yeast. N-truncated BCL-xL rapidly induced large multi-conductance channels with a maximal conductance significantly larger than those produced by full-length BCL-xL. This activity required the hydrophobic C terminus and the BH3 domain of BCL-xL. Moreover, N-truncated BCL-xL failed to produce any channel activity when applied to plasma membranes, suggesting that a component of the mitochondrial membrane is necessary for its actions. Consistent with this idea, the large channels induced by N-truncated BCL-xL are inhibited by NADH and require the presence of VDAC, a voltage-dependent anion channel present in the outer mitochondrial membrane. These observations suggest that the mitochondrial channels specific to full-length and N-truncated BCL-xL contribute to their opposite effects on synaptic transmission, and are consistent with their opposite effects on the cell death pathway.
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Affiliation(s)
- Elizabeth A Jonas
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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28
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Abstract
BCL-2 family proteins are known to regulate cell death during development by influencing the permeability of mitochondrial membranes. The anti-apoptotic BCL-2 family protein BCL-xL is highly expressed in the adult brain and localizes to mitochondria in the presynaptic terminal of the adult squid stellate ganglion. Application of recombinant BCL-xL through a patch pipette to mitochondria inside the giant presynaptic terminal triggered multiconductance channel activity in mitochondrial membranes. Furthermore, injection of full-length BCL-xL protein into the presynaptic terminal enhanced postsynaptic responses and enhanced the rate of recovery from synaptic depression, whereas a recombinant pro-apoptotic cleavage product of BCL-xL attenuated postsynaptic responses. The effect of BCL-xL on synaptic responses persisted in the presence of a blocker of mitochondrial calcium uptake and was mimicked by injection of ATP into the terminal. These studies indicate that the permeability of outer mitochondrial membranes influences synaptic transmission, and they raise the possibility that modulation of mitochondrial conductance by BCL-2 family proteins affects synaptic stability.
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29
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Abstract
A double pipette system for local, controlled drug infusion is presented. Two concentric pipettes can be manipulated separately and pressurized independently by a designated double holder. The inner pipette is loaded with the desirable solution (drug), and functions as a source, while the outer one is a sink. This gives a flow of the solution between the two pipettes that protrudes only a small distance into the surrounding fluid and does not diffuse away. Time resolution of the infusion is highly controllable, and oscillatory flow can be generated. Three implementations of the double pipette system are demonstrated. We show that local application of neurotransmitters in neuronal networks is an efficient way of stimulating activity in the network. We then present a wet micro lithography technique using topical application of proteins onto the substrate. Finally, we show that we can localize a given drug on a small targeted part of a cell.
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Affiliation(s)
- Ofer Feinerman
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel.
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30
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Abstract
Mitochondria are both morphologically and functionally diverse, and this variety is thought to have important biological ramifications. The development of methods to probe the properties of individual mitochondria is therefore of utmost importance. Recent advances have been made using in situ microscopy techniques and methods to investigate isolated mitochondria, including flow cytometry, capillary electrophoresis, patch-clamping and optical trapping. Such techniques have been used to study metabolism, mitochondrial calcium homeostasis, mitochondrial membrane potential, apoptosis, and other properties.
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Affiliation(s)
- Kathryn M Fuller
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
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31
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Gorelik J, Gu Y, Spohr HA, Shevchuk AI, Lab MJ, Harding SE, Edwards CRW, Whitaker M, Moss GWJ, Benton DCH, Sánchez D, Darszon A, Vodyanoy I, Klenerman D, Korchev YE. Ion channels in small cells and subcellular structures can be studied with a smart patch-clamp system. Biophys J 2002; 83:3296-303. [PMID: 12496097 PMCID: PMC1302405 DOI: 10.1016/s0006-3495(02)75330-7] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We have developed a scanning patch-clamp technique that facilitates single-channel recording from small cells and submicron cellular structures that are inaccessible by conventional methods. The scanning patch-clamp technique combines scanning ion conductance microscopy and patch-clamp recording through a single glass nanopipette probe. In this method the nanopipette is first scanned over a cell surface, using current feedback, to obtain a high-resolution topographic image. This same pipette is then used to make the patch-clamp recording. Because image information is obtained via the patch electrode it can be used to position the pipette onto a cell with nanometer precision. The utility of this technique is demonstrated by obtaining ion channel recordings from the top of epithelial microvilli and openings of cardiomyocyte T-tubules. Furthermore, for the first time we have demonstrated that it is possible to record ion channels from very small cells, such as sperm cells, under physiological conditions as well as record from cellular microstructures such as submicron neuronal processes.
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Affiliation(s)
- Julia Gorelik
- Division of Medicine, Imperial College of Science, Technology and Medicine, MRC Clinical Sciences Centre, DuCane Road, London W12 0NN, United Kingdom
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32
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Jentsch TJ, Stein V, Weinreich F, Zdebik AA. Molecular structure and physiological function of chloride channels. Physiol Rev 2002; 82:503-68. [PMID: 11917096 DOI: 10.1152/physrev.00029.2001] [Citation(s) in RCA: 934] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cl- channels reside both in the plasma membrane and in intracellular organelles. Their functions range from ion homeostasis to cell volume regulation, transepithelial transport, and regulation of electrical excitability. Their physiological roles are impressively illustrated by various inherited diseases and knock-out mouse models. Thus the loss of distinct Cl- channels leads to an impairment of transepithelial transport in cystic fibrosis and Bartter's syndrome, to increased muscle excitability in myotonia congenita, to reduced endosomal acidification and impaired endocytosis in Dent's disease, and to impaired extracellular acidification by osteoclasts and osteopetrosis. The disruption of several Cl- channels in mice results in blindness. Several classes of Cl- channels have not yet been identified at the molecular level. Three molecularly distinct Cl- channel families (CLC, CFTR, and ligand-gated GABA and glycine receptors) are well established. Mutagenesis and functional studies have yielded considerable insights into their structure and function. Recently, the detailed structure of bacterial CLC proteins was determined by X-ray analysis of three-dimensional crystals. Nonetheless, they are less well understood than cation channels and show remarkably different biophysical and structural properties. Other gene families (CLIC or CLCA) were also reported to encode Cl- channels but are less well characterized. This review focuses on molecularly identified Cl- channels and their physiological roles.
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Affiliation(s)
- Thomas J Jentsch
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany.
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Forshaw PJ, Atkins J, Ray DE, Glynn P. The catalytic domain of human neuropathy target esterase mediates an organophosphate-sensitive ionic conductance across liposome membranes. J Neurochem 2001; 79:400-6. [PMID: 11677268 DOI: 10.1046/j.1471-4159.2001.00562.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In humans and other vertebrates, reaction of organophosphates with a neuronal membrane protein, neuropathy target esterase (NTE), initiates events which culminate in axonal degeneration. The initiation process appears to involve modification of a property of the protein distinct from its esterase activity, subsequent to formation of a negatively charged adduct with the active site serine residue. Here, we show that membrane patches from liposomes containing NEST, a recombinant hydrophobic polypeptide comprising the esterase domain of human NTE, display a transmembrane ionic conductance with both stable and high-frequency flickering components. An asymmetric current-voltage relationship suggested that ion flow was favoured in one direction relative to the membrane and its associated NEST molecules. Flow of anions was slightly favoured compared with cations. The flickering current formed a much larger proportion of the overall conductance in patches containing wild-type NEST compared with the catalytically inactive S966A mutant form of the protein. The conductance across patches containing NEST, but not those with the S966A mutant, was significantly reduced after adding neuropathic organophosphates to the bathing medium. By contrast, non-neuropathic covalent inhibitors of the catalytic activity of NEST did not reduce NEST-mediated conductance. Future work may establish whether NTE itself mediates an organophosphate-sensitive ion flux across intracellular membranes within intact cells.
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Affiliation(s)
- P J Forshaw
- MRC Toxicology Unit, University of Leicester, Leicester, UK
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34
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Jonas EA, Buchanan J, Kaczmarek LK. Prolonged activation of mitochondrial conductances during synaptic transmission. Science 1999; 286:1347-50. [PMID: 10558987 DOI: 10.1126/science.286.5443.1347] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Although ion channels have been detected in mitochondria, scientists have not been able to record ion transport in mitochondria of intact cells. A variation of the patch clamp technique was used to record ion channel activity from intracellular organelles in the presynaptic terminal of the squid. Electron microscopy indicated that mitochondria are numerous in this terminal and are the only organelles compatible with the tips of the pipettes. Before synaptic stimulation, channel activity was infrequent and its conductance was small, although large conductances ( approximately 0.5 to 2.5 nanosiemens) could be detected occasionally. During a train of action potentials, the conductance of the mitochondrial membrane increased up to 60-fold. The conductance increased after a delay of several hundred milliseconds and continued to increase after stimulation had stopped. Recovery occurred over tens of seconds.
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Affiliation(s)
- E A Jonas
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
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35
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Van Den Brink GR, Bloemers SM, Van Den Blink B, Tertoolen LG, Van Deventer SJ, Peppelenbosch MP. Study of calcium signaling in non-excitable cells. Microsc Res Tech 1999; 46:418-33. [PMID: 10504218 DOI: 10.1002/(sici)1097-0029(19990915)46:6<418::aid-jemt9>3.0.co;2-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The fundamental importance of calcium signaling in the control of cellular physiology is widely recognized. A dramatic illustration of this is the fact that a Medline search for review articles containing the word "calcium" in the title reveals 4,629 hits, whereas the whole body of calcium signaling literature (approximately 2 x 10(6) pages) is more than enough to fill a decent-sized library. Most of this literature deals with calcium signaling in excitable cells types (mainly neurons and muscle cells), but non-excitable cell types are capable of calcium signaling as well. Although calcium fluxes in the latter cell types have attracted much less interest, the literature involved is still vast. Nevertheless, in this review article we hope to contribute some valuable insights to the field. First we shall discuss the experimental techniques available to the researcher interested in calcium signaling in non-excitable cell types with special attention to patch clamp electrophysiology. Subsequently, we shall review some of the results obtained with these techniques by focussing on the calcium-regulating mechanisms in non-excitable cells and discussing the importance of these mechanisms for physiology.
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Affiliation(s)
- G R Van Den Brink
- Laboratory for Experimental Internal Medicine, Academic Medical Center, NL-1105 AZ Amsterdam, The Netherlands
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36
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Szewczyk A. The intracellular potassium and chloride channels: properties, pharmacology and function (review). Mol Membr Biol 1998; 15:49-58. [PMID: 9724922 DOI: 10.3109/09687689809027518] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Channels selective for potassium or chloride ions are present in membranes of intracellular organelles such as sarcoplasmic (endoplasmic) reticulum, mitochondria, nucleus, synaptic vesicles, and chromaffin, and zymogen granules. They probably play an important role in cellular events such as compensation of electrical charges during transport of Ca2+, delta pH formation in mitochondria or V-ATPase containing membrane granules, and regulation of volume changes, due to potassium and chloride transport into intracellular organelles. Intracellular potassium and chloride channels could also be the target for pharmacologically active compounds. This mini-review describes the basic properties, pharmacology, and current hypotheses concerning the functional role of intracellular potassium and chloride channels.
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Affiliation(s)
- A Szewczyk
- Nencki Institute of Experimental Biology, Warsaw, Poland
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