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Yurinskaya VE, Vereninov AA. Cation-Chloride Cotransporters, Na/K Pump, and Channels in Cell Water and Ion Regulation: In silico and Experimental Studies of the U937 Cells Under Stopping the Pump and During Regulatory Volume Decrease. Front Cell Dev Biol 2021; 9:736488. [PMID: 34869320 PMCID: PMC8635019 DOI: 10.3389/fcell.2021.736488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 10/15/2021] [Indexed: 11/13/2022] Open
Abstract
Cation-coupled chloride cotransporters play a key role in generating the Cl- electrochemical gradient on the cell membrane, which is important for regulation of many cellular processes. However, a quantitative analysis of the interplay between numerous membrane transporters and channels in maintaining cell ionic homeostasis is still undeveloped. Here, we demonstrate a recently developed approach on how to predict cell ionic homeostasis dynamics when stopping the sodium pump in human lymphoid cells U937. The results demonstrate the reliability of the approach and provide the first quantitative description of unidirectional monovalent ion fluxes through the plasma membrane of an animal cell, considering all the main types of cation-coupled chloride cotransporters operating in a system with the sodium pump and electroconductive K+, Na+, and Cl- channels. The same approach was used to study ionic and water balance changes associated with regulatory volume decrease (RVD), a well-known cellular response underlying the adaptation of animal cells to a hypoosmolar environment. A computational analysis of cell as an electrochemical system demonstrates that RVD may happen without any changes in the properties of membrane transporters and channels due to time-dependent changes in electrochemical ion gradients. The proposed approach is applicable when studying truly active regulatory processes mediated by the intracellular signaling network. The developed software can be useful for calculation of the balance of the unidirectional fluxes of monovalent ions across the cell membrane of various cells under various conditions.
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Affiliation(s)
- Valentina E Yurinskaya
- Laboratory of Cell Physiology, Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
| | - Alexey A Vereninov
- Laboratory of Cell Physiology, Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
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2
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Yurinskaya V, Aksenov N, Moshkov A, Goryachaya T, Shemery A, Vereninov A. Flow fluorometry quantification of anion channel VRAC subunit LRRC8A at the membrane of living U937 cells. Channels (Austin) 2021; 14:45-52. [PMID: 32075501 PMCID: PMC7039630 DOI: 10.1080/19336950.2020.1730535] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Assessing the expression of channels on the cell membrane is a necessary step in studying the functioning of ion channels in living cells. We explore, first, if endogenous VRAC can be assayed using flow cytometry and a commercially available antibody against an extracellular loop of the LRRC8A, also known as SWELL1, subunit of the VRAC channel. The second goal is to determine if an increase in the number of VRAC channels at the cell membrane is responsible for an increase in chloride permeability of the membrane in two well-known cases: during staurosporine (STS)-induced apoptosis and after water balance disturbance caused by hypotonic medium. Human suspension lymphoid cells U937 were used as they are suitable for flow fluorometry and because we have recently studied their membrane chloride permeability during apoptosis. We found that surface expression of endogenous LRRC8A subunits can be quantified in living U937 cells using flow fluorometry with the Alomone Lab antibody. Further, we revealed that treatment of cells for 1 hour using STS or a hypotonic solution did not change the number of LRRC8A subunits to the extent that would correspond to changes in the membrane chloride permeability determined by ion content analysis. This indicates that prolonged increase in chloride permeability of the cell membrane during apoptotic cell shrinkage or cell volume regulation under hypotonicity in U937 cells occurs without altering cell surface expression of VRAC.
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Affiliation(s)
| | - Nikolay Aksenov
- Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
| | - Alexey Moshkov
- Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
| | - Tatyana Goryachaya
- Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
| | - Ashley Shemery
- School of Biomedical Sciences, Kent State University, Kent, OH, USA
| | - Alexey Vereninov
- Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
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Yurinskaya VE, Vereninov IA, Vereninov AA. Balance of Na +, K +, and Cl - Unidirectional Fluxes in Normal and Apoptotic U937 Cells Computed With All Main Types of Cotransporters. Front Cell Dev Biol 2020; 8:591872. [PMID: 33240889 PMCID: PMC7677585 DOI: 10.3389/fcell.2020.591872] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 09/30/2020] [Indexed: 12/30/2022] Open
Abstract
Fluxes of monovalent ions through the multiple pathways of the plasma membrane are highly interdependent, and their assessment by direct measurement is difficult or even impossible. Computation of the entire flux balance helps to identify partial flows and study the functional expression of individual transporters. Our previous computation of unidirectional fluxes in real cells ignored the ubiquitous cotransporters NKCC and KCC. Here, we present an analysis of the entire balance of unidirectional Na+, K+, and Cl- fluxes through the plasma membrane in human lymphoid U937 cells, taking into account not only the Na/K pump and electroconductive channels but all major types of cotransporters NC, NKCC, and KCC. Our calculations use flux equations based on the fundamental principles of macroscopic electroneutrality of the system, water balance, and the generally accepted thermodynamic dependence of ion fluxes on the driving force, and they do not depend on hypotheses about the molecular structure of the channel and transporters. A complete list of the major inward and outward Na+, K+, and Cl- fluxes is obtained for human lymphoid U937 cells at rest and during changes in the ion and water balance for the first 4 h of staurosporine-induced apoptosis. It is shown how the problem of the inevitable multiplicity of solutions to the flux equations, which arises with an increase in the number of ion pathways, can be solved in real cases by analyzing the ratio of ouabain-sensitive and ouabain-resistant parts of K+ (Rb+) influx (OSOR) and using additional experimental data on the effects of specific inhibitors. It is found that dynamics of changes in the membrane channels and transporters underlying apoptotic changes in the content of ions and water in cells, calculated without taking into account the KCC and NKCC cotransporters, differs only in details from that calculated for cells with KCC and NKCC. The developed approach to the assessment of unidirectional fluxes may be useful for understanding functional expression of ion channels and transporters in other cells under various conditions. Attached software allows reproduction of all calculated data under presented conditions and to study the effects of the condition variation.
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Affiliation(s)
- Valentina E Yurinskaya
- Laboratory of Cell Physiology, Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
| | - Igor A Vereninov
- Peter the Great St-Petersburg Polytechnic University, St-Petersburg, Russia
| | - Alexey A Vereninov
- Laboratory of Cell Physiology, Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
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Rana PS, Model MA. A Reverse-Osmosis Model of Apoptotic Shrinkage. Front Cell Dev Biol 2020; 8:588721. [PMID: 33195250 PMCID: PMC7644884 DOI: 10.3389/fcell.2020.588721] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 10/05/2020] [Indexed: 11/13/2022] Open
Abstract
The standard theory of apoptotic volume decrease (AVD) posits activation of potassium and/or chloride channels, causing an efflux of ions and osmotic loss of water. However, in view of the multitude of possible channels that are known to support apoptosis, a model based on specific signaling to a channel presents certain problems. We propose another mechanism of apoptotic dehydration based on cytoskeletal compression. As is well known, cytoskeleton is not strong enough to expel a substantial amount of water against an osmotic gradient. It is possible, however, that an increase in intracellular pressure may cause an initial small efflux of water, and that will create a small concentration gradient of ions, favoring their exit. If the channels are open, some ions will exit the cell, relieving the osmotic gradient; in this way, the process will be able to continue. Calculations confirm the possibility of such a mechanism. An increase in membrane permeability for water or ions may also result in dehydration if accompanied even by a constant cytoskeletal pressure. We review the molecular processes that may lead to apoptotic dehydration in the context of this model.
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Affiliation(s)
- Priyanka S Rana
- Department of Biological Sciences, Kent State University, Kent, OH, United States
| | - Michael A Model
- Department of Biological Sciences, Kent State University, Kent, OH, United States
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Yurinskaya VE, Vereninov IA, Vereninov AA. A Tool for Computation of Changes in Na +, K +, Cl - Channels and Transporters Due to Apoptosis by Data on Cell Ion and Water Content Alteration. Front Cell Dev Biol 2019; 7:58. [PMID: 31058149 PMCID: PMC6481184 DOI: 10.3389/fcell.2019.00058] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 03/29/2019] [Indexed: 11/13/2022] Open
Abstract
Monovalent ions are involved in a vast array of cellular processes. Their movement across the cell membrane is regulated by numerous channels and transporters. Identification of the pathways responsible for redistribution of ions and cell water in living cells is hampered by their strong interdependence. This difficulty can be overcome by computational analysis of the whole cell flux balance. Our previous computational studies were concerned with monovalent ion fluxes in cells under the conditions of balanced ion distribution or during transition processes after stopping the Na+/K+ pump. Here we analyze a more complex case-redistribution of ions during cell apoptosis when the parameters keep changing during the process. New experimental data for staurosporine-induced apoptosis of human lymphoma cells U937 have been obtained: the time course of changes in cellular K+, Na+, Cl-, and water content, as well as Rb+ fluxes as a marker of the Na/K pump activity. Using a newly developed computational tool, we found that alteration of ion and water balance was associated with a 55% decrease in the Na+/K+-ATPase rate coefficient over a 4-h period, with a time-dependent increase in potassium channel permeability, and a decrease in sodium channel permeability. The early decrease in [Cl-]i and cell volume were associated with an ~5-fold increase in chloride channel permeability. The developed approach and the presented executable file can be used to identify the channels and transporters responsible for alterations of cell ion and water balance not only during apoptosis but in other physiological scenarios.
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Affiliation(s)
- Valentina E. Yurinskaya
- Laboratory of Cell Physiology, Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
| | - Igor A. Vereninov
- Peter the Great St-Petersburg Polytechnic University, St-Petersburg, Russia
| | - Alexey A. Vereninov
- Laboratory of Cell Physiology, Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
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Marakhova I, Domnina A, Shatrova A, Borodkina A, Burova E, Pugovkina N, Zemelko V, Nikolsky N. Proliferation-related changes in K + content in human mesenchymal stem cells. Sci Rep 2019; 9:346. [PMID: 30674973 PMCID: PMC6344592 DOI: 10.1038/s41598-018-36922-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 11/27/2018] [Indexed: 12/23/2022] Open
Abstract
Intracellular monovalent ions have been shown to be important for cell proliferation, however, mechanisms through which ions regulate cell proliferation is not well understood. Ion transporters may be implicated in the intracellular signaling: Na+ and Cl− participate in regulation of intracellular pH, transmembrane potential, Ca2+ homeostasis. Recently, it is has been suggested that K+ may be involved in “the pluripotency signaling network”. Our study has been focused on the relations between K+ transport and stem cell proliferation. We compared monovalent cation transport in human mesenchymal stem cells (hMSCs) at different passages and at low and high densities of culture as well as during stress-induced cell cycle arrest and revealed a decline in K+ content per cell protein which was associated with accumulation of G1 cells in population and accompanied cell proliferation slowing. It is suggested that cell K+ may be important for successful cell proliferation as the main intracellular ion that participates in regulation of cell volume during cell cycle progression. It is proposed that cell K+ content as related to cell protein is a physiological marker of stem cell proliferation and may be used as an informative test for assessing the functional status of stem cells in vitro.
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Affiliation(s)
- Irina Marakhova
- Department of Intracellular Signaling and Transport, Institute of Cytology, Academy of Sciences, St-Petersburg, 194064, Russian Federation.
| | - Alisa Domnina
- Department of Intracellular Signaling and Transport, Institute of Cytology, Academy of Sciences, St-Petersburg, 194064, Russian Federation
| | - Alla Shatrova
- Department of Intracellular Signaling and Transport, Institute of Cytology, Academy of Sciences, St-Petersburg, 194064, Russian Federation
| | - Aleksandra Borodkina
- Department of Intracellular Signaling and Transport, Institute of Cytology, Academy of Sciences, St-Petersburg, 194064, Russian Federation
| | - Elena Burova
- Department of Intracellular Signaling and Transport, Institute of Cytology, Academy of Sciences, St-Petersburg, 194064, Russian Federation
| | - Natalja Pugovkina
- Department of Intracellular Signaling and Transport, Institute of Cytology, Academy of Sciences, St-Petersburg, 194064, Russian Federation
| | - Victoria Zemelko
- Department of Intracellular Signaling and Transport, Institute of Cytology, Academy of Sciences, St-Petersburg, 194064, Russian Federation
| | - Nikolay Nikolsky
- Department of Intracellular Signaling and Transport, Institute of Cytology, Academy of Sciences, St-Petersburg, 194064, Russian Federation
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Model MA, Petruccelli JC. Intracellular Macromolecules in Cell Volume Control and Methods of Their Quantification. CURRENT TOPICS IN MEMBRANES 2018; 81:237-289. [DOI: 10.1016/bs.ctm.2018.06.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Vereninov IA, Yurinskaya VE, Model MA, Vereninov AA. Unidirectional Flux Balance of Monovalent Ions in Cells with Na/Na and Li/Na Exchange: Experimental and Computational Studies on Lymphoid U937 Cells. PLoS One 2016; 11:e0153284. [PMID: 27159324 PMCID: PMC4861346 DOI: 10.1371/journal.pone.0153284] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 03/25/2016] [Indexed: 01/03/2023] Open
Abstract
Monovalent ion traffic across the cell membrane occurs via various pathways. Evaluation of individual fluxes in whole cell is hampered by their strong interdependence. This difficulty can be overcome by computational analysis of the whole cell flux balance. However, the previous computational studies disregarded ion movement of the self-exchange type. We have taken this exchange into account. The developed software allows determination of unidirectional fluxes of all monovalent ions via the major pathways both under the balanced state and during transient processes. We show how the problem of finding the rate coefficients can be solved by measurement of monovalent ion concentrations and some of the fluxes. Interdependence of fluxes due to the mandatory conditions of electroneutrality and osmotic balance and due to specific effects can be discriminated, enabling one to identify specific changes in ion transfer machinery under varied conditions. To test the effectiveness of the developed approach we made use of the fact that Li/Na exchange is known to be an analogue of the coupled Na/Na exchange. Thus, we compared the predicted and experimental data obtained on U937 cells under varied Li+ concentrations and following inhibition of the sodium pump with ouabain. We found that the coupled Na/Na exchange in U937 cells comprises a significant portion of the entire Na+ turnover. The data showed that the loading of the sodium pump by Li/Na exchange involved in the secondary active Li+ transport at 1-10 mM external Li+ is small. This result may be extrapolated to similar Li+ and Na+ flux relationships in erythrocytes and other cells in patients treated with Li+ in therapeutic doses. The developed computational approach is applicable for studying various cells and can be useful in education for demonstrating the effects of individual transporters and channels on ion gradients, cell water content and membrane potential.
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Affiliation(s)
- Igor A. Vereninov
- Peter the Great St-Petersburg Polytechnic University, St-Petersburg, Russia
| | - Valentina E. Yurinskaya
- Laboratory of Cell Physiology, Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
| | - Michael A. Model
- Department of Biological Sciences, Kent State University, Kent, Ohio, 44242, United States of America
| | - Alexey A. Vereninov
- Laboratory of Cell Physiology, Institute of Cytology, Russian Academy of Sciences, St-Petersburg, Russia
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Rubashkin AA. Ouabain switches Na+ transport to Na+/Na+ equivalent exchange in normal and apoptotic lymphoid cells. Biophysics (Nagoya-shi) 2013. [DOI: 10.1134/s000635091305014x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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10
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Simard JM, Woo SK, Gerzanich V. Transient receptor potential melastatin 4 and cell death. Pflugers Arch 2012; 464:573-82. [PMID: 23065026 PMCID: PMC3513597 DOI: 10.1007/s00424-012-1166-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 09/25/2012] [Accepted: 09/25/2012] [Indexed: 12/12/2022]
Abstract
Cell death proceeds by way of a variety of “cell death subroutines,” including several types of “apoptosis,” “regulated necrosis,” and others. “Accidental necrosis” due to profound adenosine triphosphate (ATP) depletion or oxidative stress is distinguished from regulated necrosis by the absence of death receptor signaling. However, both accidental and regulated necrosis have in common the process of “oncosis,” a physiological process characterized by Na+ influx and cell volume increase that, in necrotic cell death, is required to produce the characteristic features of membrane blebbing and membrane rupture. Here, we review emerging evidence that the monovalent cation channel, transient receptor potential melastatin 4 (TRPM4), is involved in the cell death process of oncosis. Potential involvement of TRPM4 in oncosis is suggested by the fact that the two principal regulators of TRPM4, intracellular ATP and Ca2+, are both altered during necrosis in the direction that causes TRPM4 channel opening. Under physiological conditions, activation of TRPM4 promotes Na+ influx and cell depolarization. Under pathological conditions, unchecked activation of TRPM4 leads to Na+ overload, cell volume increase, blebbing and cell membrane rupture, the latter constituting the irreversible end stage of necrosis. Emerging data indicate that TRPM4 plays a crucial role as end executioner in the accidental necrotic death of ATP-depleted or redox-challenged endothelial and epithelial cells, both in vitro and in vivo. Future studies will be needed to determine whether TRPM4 also plays a role in regulated necrosis and apoptosis.
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Affiliation(s)
- J Marc Simard
- Department of Neurosurgery, University of Maryland School of Medicine, 22 S. Greene Street, Baltimore, MD 21201-1595, USA.
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Yurinskaya VE, Moshkov AV, Wibberley AV, Lang F, Model MA, Vereninov AA. Dual Response of Human Leukemia U937 Cells to Hypertonic Shrinkage: Initial Regulatory Volume Increase (RVI) and Delayed Apoptotic Volume Decrease (AVD). Cell Physiol Biochem 2012; 30:964-73. [DOI: 10.1159/000341473] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/29/2012] [Indexed: 12/16/2022] Open
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Yurinskaya VE, Rubashkin AA, Shirokova AV, Vereninov AA. Regulatory volume increase (RVI) and apoptotic volume decrease (AVD) in U937 cells in hypertonic medium. ACTA ACUST UNITED AC 2011. [DOI: 10.1134/s1990519x11050129] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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13
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Yurinskaya VE, Rubashkin AA, Vereninov AA. Balance of unidirectional monovalent ion fluxes in cells undergoing apoptosis: why does Na+/K+ pump suppression not cause cell swelling? J Physiol 2011; 589:2197-211. [PMID: 21486767 DOI: 10.1113/jphysiol.2011.207571] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cells dying according to the apoptotic program, unlike cells dying via an unprogrammed mode, are able to avoid swelling and osmotic bursting with membrane disruption.There are indications that apoptosis is accompanied by suppression of the Na+/K+ pump and changes in the K+ and Cl− channels. It remains unclear how ion fluxes through individual ion pathways are integrated so as to induce loss of intracellular ions and concomitant apoptotic volume decrease. A decrease in activity of the sodium pump during apoptosis should cause cell swelling rather than shrinkage. We have made the first systemic analysis of the monovalent ion flux balance in apoptotic cells. Experimental data were obtained for human U937 cells treated with staurosporine for 4–5 h, which is known to induce apoptosis. The data include cellular Cl− content and fluxes, K+, Na+, water content and ouabain-sensitive and -resistant Rb+ fluxes.Unidirectional monovalent ion fluxeswere calculated using these data and a cell model comprising the double Donnan system with the Na+/K+ pump, Cl−, K+, Na+ channels, the Na+–K+–2Cl−cotransporter (NKCC), the Na+–Cl− cotransporter (NC), and the equivalent Cl−/Cl− exchange.Apoptotic cell shrinkage was found to be caused, depending on conditions, either by an increase in the integral channel permeability of membrane for K+ or by suppression of the pump coupledwith a decrease in the integral channel permeability of membrane for Na+. The decrease in the channel permeability of membrane for Na+ plays a crucial role in cell dehydration in apoptosis accompanied by suppression of the pump. Supplemental Table S1 is given for easy calculating flux balance under specified conditions.
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Rubashkin AA, Yurinskaya VE, Vereninov AA. Calculations of K+, Na+, and Cl− fluxes across cell membrane with Na+/K+ pump, NKCC, NC cotransport and ionic channels with non-Goldman rectification in K+-channels: Normal and apoptotic cells. ACTA ACUST UNITED AC 2010. [DOI: 10.1134/s1990519x10050093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Valencia-Cruz G, Shabala L, Delgado-Enciso I, Shabala S, Bonales-Alatorre E, Pottosin II, Dobrovinskaya OR. K(bg) and Kv1.3 channels mediate potassium efflux in the early phase of apoptosis in Jurkat T lymphocytes. Am J Physiol Cell Physiol 2009; 297:C1544-53. [PMID: 19794143 DOI: 10.1152/ajpcell.00064.2009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Microelectrode ion flux estimation (MIFE) and patch-clamp techniques were combined for noninvasive K(+) flux measurements and recording of activities of the dominant K(+) channels in the early phases of apoptosis in Jurkat cells. Staurosporine (STS, 1 microM) evoked rapid (peaking around 15 min) transient K(+) efflux, which then gradually decreased. This transient K(+) efflux occurred concurrently with the transient increase of the K(+) background (K(bg)) TWIK-related spinal cord K(+) channel-like current density, followed by a drastic decrease and concomitant membrane depolarization. The Kv1.3 current density remained almost constant. Kv1.3 activation was not altered by STS, whereas the inactivation was shifted to more positive potentials. Contribution of K(bg) and Kv1.3 channels to the transient and posttransient STS-induced K(+) efflux components, respectively, was confirmed by the effects of bupivacaine, predominantly blocking K(bg) current, and the Kv1.3-specific blocker margatoxin. Channel-mediated K(+) efflux provoked a substantial cellular shrinkage and affected the activation of caspases.
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