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Lemos FO, Bultynck G, Parys JB. A comprehensive overview of the complex world of the endo- and sarcoplasmic reticulum Ca 2+-leak channels. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1868:119020. [PMID: 33798602 DOI: 10.1016/j.bbamcr.2021.119020] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 03/09/2021] [Accepted: 03/13/2021] [Indexed: 12/11/2022]
Abstract
Inside cells, the endoplasmic reticulum (ER) forms the largest Ca2+ store. Ca2+ is actively pumped by the SERCA pumps in the ER, where intraluminal Ca2+-binding proteins enable the accumulation of large amount of Ca2+. IP3 receptors and the ryanodine receptors mediate the release of Ca2+ in a controlled way, thereby evoking complex spatio-temporal signals in the cell. The steady state Ca2+ concentration in the ER of about 500 μM results from the balance between SERCA-mediated Ca2+ uptake and the passive leakage of Ca2+. The passive Ca2+ leak from the ER is often ignored, but can play an important physiological role, depending on the cellular context. Moreover, excessive Ca2+ leakage significantly lowers the amount of Ca2+ stored in the ER compared to normal conditions, thereby limiting the possibility to evoke Ca2+ signals and/or causing ER stress, leading to pathological consequences. The so-called Ca2+-leak channels responsible for Ca2+ leakage from the ER are however still not well understood, despite over 20 different proteins have been proposed to contribute to it. This review has the aim to critically evaluate the available evidence about the various channels potentially involved and to draw conclusions about their relative importance.
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Affiliation(s)
- Fernanda O Lemos
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut, Campus Gasthuisberg O/N-1 B-802, Herestraat 49, B-3000 Leuven, Belgium
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut, Campus Gasthuisberg O/N-1 B-802, Herestraat 49, B-3000 Leuven, Belgium
| | - Jan B Parys
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut, Campus Gasthuisberg O/N-1 B-802, Herestraat 49, B-3000 Leuven, Belgium.
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2
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Chinigò G, Fiorio Pla A, Gkika D. TRP Channels and Small GTPases Interplay in the Main Hallmarks of Metastatic Cancer. Front Pharmacol 2020; 11:581455. [PMID: 33132914 PMCID: PMC7550629 DOI: 10.3389/fphar.2020.581455] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 09/11/2020] [Indexed: 12/13/2022] Open
Abstract
Transient Receptor Potential (TRP) cations channels, as key regulators of intracellular calcium homeostasis, play a central role in the essential hallmarks of cancer. Among the multiple pathways in which TRPs may be involved, here we focus our attention on the ones involving small guanosine triphosphatases (GTPases), summarizing the main processes associated with the metastatic cascade, such as migration, invasion and tumor vascularization. In the last decade, several studies have highlighted a bidirectional interplay between TRPs and small GTPases in cancer progression: TRP channels may affect small GTPases activity via both Ca2+-dependent or Ca2+-independent pathways, and, conversely, some small GTPases may affect TRP channels activity through the regulation of their intracellular trafficking to the plasma membrane or acting directly on channel gating. In particular, we will describe the interplay between TRPC1, TRPC5, TRPC6, TRPM4, TRPM7 or TRPV4, and Rho-like GTPases in regulating cell migration, the cooperation of TRPM2 and TRPV2 with Rho GTPases in increasing cell invasiveness and finally, the crosstalk between TRPC1, TRPC6, TRPM8, TRPV4 and both Rho- and Ras-like GTPases in inducing aberrant tumor vascularization.
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Affiliation(s)
- Giorgia Chinigò
- Laboratory of Cellular and Molecular Angiogenesis, Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy.,Laboratoire de Cell Physiology, Université de Lille, Department of Life Sciences, Univ. Lille, Inserm, U1003-PHYCEL, Lille, France
| | - Alessandra Fiorio Pla
- Laboratory of Cellular and Molecular Angiogenesis, Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy.,Laboratoire de Cell Physiology, Université de Lille, Department of Life Sciences, Univ. Lille, Inserm, U1003-PHYCEL, Lille, France
| | - Dimitra Gkika
- Laboratoire de Cell Physiology, Université de Lille, Department of Life Sciences, Univ. Lille, Inserm, U1003-PHYCEL, Lille, France.,Univ. Lille, CNRS, INSERM, CHU Lille, Centre Oscar Lambret, UMR 9020-UMR 1277-Canther-Cancer Heterogeneity, Plasticity and Resistance to Therapies, Lille, France.,Institut Universitaire de France (IUF), Paris, France
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3
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Yang Y, Rong X, Lv X, Jiang W, Yang Y, Lai D, Xu S, Fu G. Inhibition of mevalonate pathway prevents ischemia-induced cardiac dysfunction in rats via RhoA-independent signaling pathway. Cardiovasc Ther 2018; 35. [PMID: 28665545 DOI: 10.1111/1755-5922.12285] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 05/31/2017] [Accepted: 06/27/2017] [Indexed: 11/27/2022] Open
Abstract
AIM We previously demonstrated that anoxia-mediated Ca2+ handling dysfunction could be ameliorated through inhibition of mevalonate pathway via RhoA- and Ras-related mechanisms in H9c2 cells. In this study, we further explored whether inhibition of mevalonate pathway is associated with cardiac remodeling and dysfunction in ischemic cardiomyopathy, and discussed the possible role of Ras, Rac and RhoA in cardiac dysfunction. METHODS We investigated the role of mevalonate pathway in cardiac remodeling and cardiomyocyte Ca2+ handling proteins expression in a rat model of cardiac dysfunction due to myocardial infarction (MI). After MI, adult male Sprague-Dawley rats were treated with drugs that antagonize key components in mevalonate pathway, including 3-hydroxy-3-methylglutaryl-CoA reductase, farnesyl pyrophosphate synthase, and Rho-kinase for 10 weeks. The protein expression of ryanodine receptor 2 (RyR2), sarcoplasmic reticulum Ca2+ ATPase (SERCA) 2a, phospholamban (PLB), phospho-PLB at serine-16 (PSer16-PLB), FKBP12.6, and RhoA as well as RyR2 and FKBP12.6 mRNA levels was evaluated. RESULTS Rosuvastatin and alendronate treatment prevented myocardial remodeling, improved cardiac function and reduced infarct size. Furthermore, rosuvastatin and alendronate promoted an increase in the protein expression of SERCA2a and PSer16-PLB/PLB ratio as well as partially restored the RyR2 and FKBP12.6 gene and protein expression. Fasudil failed to exert these beneficial effects. CONCLUSIONS These findings indicate that mevalonate pathway inhibition by rosuvastatin and alendronate prevents cardiac remodeling and dysfunction possibly through RhoA-independent mechanisms.
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Affiliation(s)
- Ying Yang
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Xiqing Rong
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Xue Lv
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Wenbing Jiang
- Department of Cardiology, Wenzhou People's Hospital, Wenzhou, China
| | - Yuan Yang
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Dongwu Lai
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Shiming Xu
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China.,Institute of Translational Medicine, College of Medicine, Zhejiang University, Hangzhou, China
| | - Guosheng Fu
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
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Yan X, Yan M, Guo Y, Singh G, Chen Y, Yu M, Wang D, Hillery CA, Chan AM. R-Ras Regulates Murine T Cell Migration and Intercellular Adhesion Molecule-1 Binding. PLoS One 2015; 10:e0145218. [PMID: 26710069 PMCID: PMC4692399 DOI: 10.1371/journal.pone.0145218] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Accepted: 11/30/2015] [Indexed: 12/04/2022] Open
Abstract
The trafficking of T-lymphocytes to peripheral draining lymph nodes is crucial for mounting an adaptive immune response. The role of chemokines in the activation of integrins via Ras-related small GTPases has been well established. R-Ras is a member of the Ras-subfamily of small guanosine-5’-triphosphate-binding proteins and its role in T cell trafficking has been investigated in R-Ras null mice (Rras−/−). An examination of the lymphoid organs of Rras−/− mice revealed a 40% reduction in the cellularity of the peripheral lymph nodes. Morphologically, the high endothelial venules of Rras−/− mice were more disorganized and less mature than those of wild-type mice. Furthermore, CD4+ and CD8+ T cells from Rras−/− mice had approximately 42% lower surface expression of L-selectin/CD62L. These aberrant peripheral lymph node phenotypes were associated with proliferative and trafficking defects in Rras−/− T cells. Furthermore, R-Ras could be activated by the chemokine, CCL21. Indeed, Rras−/− T cells had approximately 14.5% attenuation in binding to intercellular adhesion molecule 1 upon CCL21 stimulation. Finally, in a graft-versus host disease model, recipient mice that were transfused with Rras−/− T cells showed a significant reduction in disease severity when compared with mice transplanted with wild-type T cells. These findings implicate a role for R-Ras in T cell trafficking in the high endothelial venules during an effective immune response.
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Affiliation(s)
- Xiaocai Yan
- Department of Pediatrics, The Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Mingfei Yan
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong SAR
| | - Yihe Guo
- Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Gobind Singh
- Department of Oncological Sciences, The Mount Sinai School of Medicine, New York, New York, United States of America
| | - Yuhong Chen
- Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Mei Yu
- Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Demin Wang
- Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Cheryl A Hillery
- Department of Pediatrics, The Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America.,Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Andrew M Chan
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong SAR
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5
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McHugh BJ, Buttery R, Lad Y, Banks S, Haslett C, Sethi T. Integrin activation by Fam38A uses a novel mechanism of R-Ras targeting to the endoplasmic reticulum. J Cell Sci 2010; 123:51-61. [PMID: 20016066 DOI: 10.1242/jcs.056424] [Citation(s) in RCA: 149] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The integrin family of heterodimeric cell-surface receptors are fundamental in cell-cell and cell-matrix adhesion. Changes to either integrin-ligand affinity or integrin gene expression are central to a variety of disease processes, including inflammation, cardiovascular disease and cancer. In screening for novel activators of integrin-ligand affinity we identified the previously uncharacterised multi-transmembrane domain protein Fam38A, located at the endoplasmic reticulum (ER). siRNA knockdown of Fam38A in epithelial cells inactivates endogenous beta1 integrin, reducing cell adhesion. Fam38A mediates integrin activation by recruiting the small GTPase R-Ras to the ER, which activates the calcium-activated protease calpain by increasing Ca(2+) release from cytoplasmic stores. Fam38A-induced integrin activation is blocked by inhibition of either R-Ras or calpain activity, or by siRNA knockdown of talin, a well-described calpain substrate. This highlights a novel mechanism for integrin activation by Fam38A, utilising calpain and R-Ras signalling from the ER. These data represent the first description of a novel spatial regulator of R-Ras, of an alternative integrin activation-suppression pathway based on direct relocalisation of R-Ras to the ER, and of a mechanism linking R-Ras and calpain signalling from the ER with modulation of integrin-ligand affinity.
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Affiliation(s)
- Brian J McHugh
- MRC Centre for Inflammation Research, Queens Medical Research Institute, University of Edinburgh, EH16 4TJ, UK.
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Valsecchi F, Esseling JJ, Koopman WJH, Willems PHGM. Calcium and ATP handling in human NADH:ubiquinone oxidoreductase deficiency. Biochim Biophys Acta Mol Basis Dis 2009; 1792:1130-7. [PMID: 19171191 DOI: 10.1016/j.bbadis.2009.01.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Accepted: 01/04/2009] [Indexed: 02/07/2023]
Abstract
Proper cell functioning requires precise coordination between mitochondrial ATP production and local energy demand. Ionic calcium (Ca(2+)) plays a central role in this coupling because it activates mitochondrial oxidative phosphorylation (OXPHOS) during hormonal and electrical cell stimulation. To determine how mitochondrial dysfunction affects cytosolic and mitochondrial Ca(2+)/ATP handling, we performed life-cell quantification of these parameters in fibroblast cell lines derived from healthy subjects and patients with isolated deficiency of the first OXPHOS complex (CI). In resting patient cells, CI deficiency was associated with a normal mitochondrial ([ATP](m)) and cytosolic ([ATP](c)) ATP concentration, a normal cytosolic Ca(2+) concentration ([Ca(2+)](c)), but a reduced Ca(2+) content of the endoplasmic reticulum (ER). Furthermore, cellular NAD(P)H levels were increased, mitochondrial membrane potential was slightly depolarized, reactive oxygen species (ROS) levels were elevated and mitochondrial shape was altered. Upon stimulation with bradykinin (Bk), the peak increases in [Ca(2+)](c), mitochondrial Ca(2+) concentration ([Ca(2+)](m)), [ATP](c) and [ATP](m) were reduced in patient cells. In agreement with these results, ATP-dependent Ca(2+) removal from the cytosol was slower. Here, we review the interconnection between cytosolic, endoplasmic reticular and mitochondrial Ca(2+) and ATP handling, and summarize our findings in patient fibroblasts in an integrative model.
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Affiliation(s)
- Federica Valsecchi
- Department of Membrane Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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7
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Roscioni SS, Elzinga CRS, Schmidt M. Epac: effectors and biological functions. Naunyn Schmiedebergs Arch Pharmacol 2008; 377:345-57. [PMID: 18176800 DOI: 10.1007/s00210-007-0246-7] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Accepted: 12/05/2007] [Indexed: 12/17/2022]
Abstract
Epac1 (also known as cAMP-GEF-I) and Epac2 (also known as cAMP-GEF-II) are cyclic AMP-activated guanine nucleotide exchange factors for Ras-like GTPases. Since their discovery about 10 years ago, it is now accepted that Epac proteins are novel cAMP sensors that regulate several pivotal cellular processes, including calcium handling, cell proliferation, cell survival, cell differentiation, cell polarization, cell-cell adhesion events, gene transcription, secretion, ion transport, and neuronal signaling. Recent studies even indicated that Epac proteins might play a role in the regulation of inflammation and the development of cardiac hypertrophy. Meanwhile, a plethora of diverse effectors of Epac proteins have been assigned, such as Ras and Rho GTPases, phospholiase C-epsilon, phospholipase D, mitogen-activated protein kinases, protein kinase B/Akt, ion channels, secretory-granule associated proteins and regulators of the actin-microtubule network, the latter probably involved in the spatiotemporal dynamics of Epac-related signaling. This review highlights multi-faceted effectors and diverse biological functions driven by Epac proteins that might explain certain controversial signaling properties of cAMP.
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Affiliation(s)
- Sara S Roscioni
- Department of Molecular Pharmacology, University of Groningen, A. Deusinglaan 1, 9713 AV, Groningen, The Netherlands
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8
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De Jesús ML, Stope MB, Weernink PAO, Mahlke Y, Börgermann C, Ananaba VN, Rimmbach C, Rosskopf D, Michel MC, Jakobs KH, Schmidt M. Cyclic AMP-dependent and Epac-mediated activation of R-Ras by G protein-coupled receptors leads to phospholipase D stimulation. J Biol Chem 2006; 281:21837-21847. [PMID: 16754664 DOI: 10.1074/jbc.m604156200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activation of the Ras-related GTPase R-Ras, which has been implicated in the regulation of various cellular functions, by G protein-coupled receptors (GPCRs) was studied in HEK-293 cells stably expressing the M3 muscarinic acetylcholine receptor (mAChR), which can couple to several types of heterotrimeric G proteins. Activation of the receptor induced a very rapid and transient activation of R-Ras. Studies with inhibitors and activators of various signaling pathways indicated that R-Ras activation by the M3 mAChR is dependent on cyclic AMP formation but is independent of protein kinase A. Similar to the rather promiscuous M3 mAChR, two typical G(s)-coupled receptors also induced R-Ras activation. The receptor actions were mimicked by an Epac-specific cyclic AMP analog and suppressed by depletion of endogenous Epac1 by small interfering RNAs, as well as expression of a cyclic AMP binding-deficient Epac1 mutant, but not by expression of dominant negative Rap GTPases. In vitro studies demonstrated that Epac1 directly interacts with R-Ras and catalyzes GDP/GTP exchange at this GTPase. Finally, it is shown that the cyclic AMP- and Epac-activated R-Ras plays a major role in the M3 mAChR-mediated stimulation of phospholipase D but not phospholipase C. Collectively, our data indicate that GPCRs rapidly activate R-Ras, that R-Ras activation by the GPCRs is apparently directly induced by cyclic AMP-regulated Epac proteins, and that activated R-Ras specifically controls GPCR-mediated phospholipase D stimulation.
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Affiliation(s)
| | - Matthias B Stope
- Institut für Pharmakologie, Universitätsklinikum Essen, 45122 Essen, Germany
| | | | - Yvonne Mahlke
- Institut für Pharmakologie, Universitätsklinikum Essen, 45122 Essen, Germany
| | - Christof Börgermann
- Institut für Pharmakologie, Universitätsklinikum Essen, 45122 Essen, Germany
| | - Viktoria N Ananaba
- Institut für Pharmakologie, Universitätsklinikum Essen, 45122 Essen, Germany
| | - Christian Rimmbach
- Institut für Pharmakologie, Universitätsklinikum Essen, 45122 Essen, Germany
| | - Dieter Rosskopf
- Institut für Pharmakologie, Universitätsklinikum Essen, 45122 Essen, Germany
| | - Martin C Michel
- Department of Pharmacology and Pharmacotherapy, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands
| | - Karl H Jakobs
- Institut für Pharmakologie, Universitätsklinikum Essen, 45122 Essen, Germany
| | - Martina Schmidt
- Institut für Pharmakologie, Universitätsklinikum Essen, 45122 Essen, Germany; Department of Pharmacology and Pharmacotherapy, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
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9
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Koopman WJH, Visch HJ, Smeitink JAM, Willems PHGM. Simultaneous quantitative measurement and automated analysis of mitochondrial morphology, mass, potential, and motility in living human skin fibroblasts. Cytometry A 2006; 69:1-12. [PMID: 16342116 DOI: 10.1002/cyto.a.20198] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Understanding the interdependence of mitochondrial and cellular functioning in health and disease requires detailed knowledge about the coupling between mitochondrial structure, motility, and function. Currently, no rapid approach is available for simultaneous quantification of these parameters in single living cells. METHODS Human skin fibroblasts were pulse-loaded with the mitochondria-selective fluorescent cation rhodamine 123. Next, mitochondria were visualized using video-rate (30 Hz) confocal microscopy and real-time image averaging. To highlight the mitochondria, the acquired images were binarized using a novel image processing strategy. RESULTS Our approach enabled rapid and simultaneous quantification of mitochondrial morphology, mass, potential, and motility. It was found that acute inhibition of mitochondrial complex I (NADH:ubiquinone oxidoreductase) by means of rotenone transiently reduced mitochondrial branching, area, and potential. In contrast, mitochondrial motility was permanently reduced. CONCLUSIONS We present and validate a novel approach for rapid, unbiased, and simultaneous quantification of multiple mitochondrial parameters in living cells. Because this method is automated, large numbers of cells can be analyzed in a short period of time.
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Affiliation(s)
- Werner J H Koopman
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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10
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Ada-Nguema AS, Xenias H, Hofman JM, Wiggins CH, Sheetz MP, Keely PJ. The small GTPase R-Ras regulates organization of actin and drives membrane protrusions through the activity of PLCepsilon. J Cell Sci 2006; 119:1307-19. [PMID: 16537651 DOI: 10.1242/jcs.02835] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
R-Ras, an atypical member of the Ras subfamily of small GTPases, enhances integrin-mediated adhesion and signaling through a poorly understood mechanism. Dynamic analysis of cell spreading by total internal reflection fluorescence (TIRF) microscopy demonstrated that active R-Ras lengthened the duration of initial membrane protrusion, and promoted the formation of a ruffling lamellipod, rich in branched actin structures and devoid of filopodia. By contrast, dominant-negative R-Ras enhanced filopodia formation. Moreover, RNA interference (RNAi) approaches demonstrated that endogenous R-Ras contributed to cell spreading. These observations suggest that R-Ras regulates membrane protrusions through organization of the actin cytoskeleton. Our results suggest that phospholipase Cepsilon (PLCepsilon) is a novel R-Ras effector mediating the effects of R-Ras on the actin cytoskeleton and membrane protrusion, because R-Ras was co-precipitated with PLCepsilon and increased its activity. Knockdown of PLCepsilon with siRNA reduced the formation of the ruffling lamellipod in R-Ras cells. Consistent with this pathway, inhibitors of PLC activity, or chelating intracellular Ca2+ abolished the ability of R-Ras to promote membrane protrusions and spreading. Overall, these data suggest that R-Ras signaling regulates the organization of the actin cytoskeleton to sustain membrane protrusion through the activity of PLCepsilon.
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Affiliation(s)
- Aude S Ada-Nguema
- Department of Pharmacology, University of Wisconsin-Madison, Madison, WI 53706, USA
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Piwocka K, Vejda S, Cotter TG, O'Sullivan GC, McKenna SL. Bcr-Abl reduces endoplasmic reticulum releasable calcium levels by a Bcl-2-independent mechanism and inhibits calcium-dependent apoptotic signaling. Blood 2006; 107:4003-10. [PMID: 16469868 DOI: 10.1182/blood-2005-04-1523] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The Bcr-Abl oncoprotein plays a major role in the development and progression of chronic myeloid leukemia (CML). Several studies have suggested that the expression levels of Bcr-Abl are elevated at disease progression to blast crisis and that this plays a significant role in the achievement of drug resistance. We have established cell lines expressing low and high levels of Bcr-Abl to study the molecular mechanisms involved in disease progression and drug resistance. It is now known that the endoplasmic reticulum (ER) can play a major role in the regulation of apoptosis. We therefore investigated whether Bcr-Abl expression modulates ER homeostasis and interferes with ER-mediated apoptotic pathways to promote survival. Bcr-Abl-expressing cells exhibit a decreased amount of free releasable calcium in the ER as well as a weaker capacitative calcium entry response, relative to parental cells. This effect is independent of Bcl-2, which is a known modulator of ER calcium homeostasis. The reduction in ER releasable calcium results in inhibition of the ER/mitochondria-coupling process and mitochondrial calcium uptake. This study demonstrates a novel downstream consequence of Bcr-Abl signaling. The ability to negate calcium-dependent apoptotic signaling is likely to be a major prosurvival mechanism in Bcr-Abl-expressing cells.
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Affiliation(s)
- Katarzyna Piwocka
- Department of Biochemistry, BioSciences Institute, University College Cork, Cork, Ireland
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12
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Visch HJ, Koopman WJH, Leusink A, van Emst-de Vries SE, van den Heuvel LWPJ, Willems PHGM, Smeitink JAM. Decreased agonist-stimulated mitochondrial ATP production caused by a pathological reduction in endoplasmic reticulum calcium content in human complex I deficiency. Biochim Biophys Acta Mol Basis Dis 2005; 1762:115-23. [PMID: 16213125 DOI: 10.1016/j.bbadis.2005.09.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2005] [Revised: 08/15/2005] [Accepted: 09/01/2005] [Indexed: 10/25/2022]
Abstract
Although a large number of mutations causing malfunction of complex I (NADH:ubiquinone oxidoreductase) of the OXPHOS system is now known, their cell biological consequences remain obscure. We previously showed that the bradykinin (Bk)-induced increase in mitochondrial [ATP] ([ATP](M)) is significantly reduced in primary skin fibroblasts from a patient with an isolated complex I deficiency. The present work addresses the mechanism(s) underlying this impaired response. Luminometry of fibroblasts from 6 healthy subjects and 14 genetically characterized patients expressing mitochondria targeted luciferase revealed that the Bk-induced increase in [ATP](M) was significantly, but to a variable degree, decreased in 10 patients. The same variation was observed for the increases in mitochondrial [Ca(2+)] ([Ca(2+)](M)), measured with mitochondria targeted aequorin, and cytosolic [Ca(2+)] ([Ca(2+)](C)), measured with fura-2, and for the Ca(2+) content of the endoplasmic reticulum (ER), calculated from the increase in [Ca(2+)](C) evoked by thapsigargin, an inhibitor of the ER Ca(2+) ATPase. Regression analysis revealed that the increase in [ATP](M) was directly proportional to the increases in [Ca(2+)](C) and [Ca(2+)](M) and to the ER Ca(2+) content. Our findings provide evidence that a pathological reduction in ER Ca(2+) content is the direct cause of the impaired Bk-induced increase in [ATP](M) in human complex I deficiency.
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Affiliation(s)
- Henk-Jan Visch
- Department of Biochemistry for Molecular Life Sciences, Radboud University Nijmegen, The Netherlands
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13
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Koopman WJH, Willems PHGM, Oosterhof A, van Kuppevelt TH, Gielen SCAM. Amplitude modulation of nuclear Ca2+ signals in human skeletal myotubes: A possible role for nuclear Ca2+ buffering. Cell Calcium 2005; 38:141-52. [PMID: 16054687 DOI: 10.1016/j.ceca.2005.06.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 05/17/2005] [Accepted: 06/02/2005] [Indexed: 11/20/2022]
Abstract
Video-rate confocal microscopy of Indo-1-loaded human skeletal myotubes was used to assess the relationship between the changes in sarcoplasmic ([Ca(2+)](S)) and nuclear ([Ca(2+)](N)) Ca(2+) concentration during low- and high-frequency electrostimulation. A single stimulus of 10 ms duration transiently increased [Ca(2+)] in both compartments with the same time of onset. Rate and amplitude of the [Ca(2+)] rise were significantly lower in the nucleus (4.0- and 2.5-fold, respectively). Similarly, [Ca(2+)](N) decayed more slowly than [Ca(2+)](S) (mono-exponential time constants of 6.1 and 2.5 s, respectively). After return of [Ca(2+)] to the prestimulatory level, a train of 10 stimuli was applied at a frequency of 1 Hz. The amplitude of the first [Ca(2+)](S) transient was 25% lower than that of the preceding single transient. Thereafter, [Ca(2+)](S) increased stepwise to a maximum that equalled that of the single transient. Similarly, the amplitude of the first [Ca(2+)](N) transient was 20% lower than that of the preceding single transient. In contrast to [Ca(2+)](S), [Ca(2+)](N) then increased to a maximum that was 2.3-fold higher than that of the single transient and equalled that of [Ca(2+)](S). In the nucleus, and to a lesser extent in the sarcoplasm, [Ca(2+)] decreased faster at the end of the stimulus train than after the preceding single stimulus (time constants of 3.3 and 2.1 s, respectively). To gain insight into the molecular principles underlying the shaping of the nuclear Ca(2+) signal, a 3-D mathematical model was constructed. Intriguingly, quantitative modelling required the inclusion of a satiable nuclear Ca(2+) buffer. Alterations in the concentration of this putative buffer had dramatic effects on the kinetics of the nuclear Ca(2+) signal. This finding unveils a possible mechanism by which the skeletal muscle can adapt to changes in physiological demand.
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Affiliation(s)
- Werner J H Koopman
- Department of 160 Biochemistry NCMLS, Radboud University Nijmegen Medical Center, The Netherlands
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14
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Aspenström P. Integration of signalling pathways regulated by small GTPases and calcium. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1742:51-8. [PMID: 15590055 DOI: 10.1016/j.bbamcr.2004.09.029] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Revised: 09/21/2004] [Accepted: 09/24/2004] [Indexed: 10/26/2022]
Abstract
The Ras superfamily of small GTPases constitutes a large group of structurally and functionally related proteins. They function as signalling switches in numerous signalling cascades in the cell. During the recent years, an increased awareness of a communication between signalling systems employing Ras-like GTPases and signalling systems employing calcium has emerged. For instance, the intensity of the activation of Ras-like GTPases is regulated by calcium-dependent mechanisms, acting on proteins that facilitate the activation or inactivation of the small GTPases. Other Ras-like GTPases have a direct influence on calcium signalling by regulating the activity of certain calcium channels. In addition, several small GTPases collaborate with calcium signalling in regulating cellular processes, such as cell adhesion, cell migration and exocytosis.
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Affiliation(s)
- Pontus Aspenström
- Biomedical Center, Ludwig Institute for Cancer Research, Box 595, S-751 24 Uppsala, Sweden.
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15
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Koopman WJH, Verkaart S, Visch HJ, van der Westhuizen FH, Murphy MP, van den Heuvel LWPJ, Smeitink JAM, Willems PHGM. Inhibition of complex I of the electron transport chain causes O2-. -mediated mitochondrial outgrowth. Am J Physiol Cell Physiol 2005; 288:C1440-50. [PMID: 15647387 DOI: 10.1152/ajpcell.00607.2004] [Citation(s) in RCA: 221] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Recent evidence indicates that oxidative stress is central to the pathogenesis of a wide variety of degenerative diseases, aging, and cancer. Oxidative stress occurs when the delicate balance between production and detoxification of reactive oxygen species is disturbed. Mammalian cells respond to this condition in several ways, among which is a change in mitochondrial morphology. In the present study, we have used rotenone, an inhibitor of complex I of the respiratory chain, which is thought to increase mitochondrial O(2)(-)* production, and mitoquinone (MitoQ), a mitochondria-targeted antioxidant, to investigate the relationship between mitochondrial O(2)(-)* production and morphology in human skin fibroblasts. Video-rate confocal microscopy of cells pulse loaded with the mitochondria-specific cation rhodamine 123, followed by automated analysis of mitochondrial morphology, revealed that chronic rotenone treatment (100 nM, 72 h) significantly increased mitochondrial length and branching without changing the number of mitochondria per cell. In addition, this treatment caused a twofold increase in lipid peroxidation as determined with C11-BODIPY(581/591). Finally, digital imaging microscopy of cells loaded with hydroethidine, which is oxidized by O(2)(-)* to yield fluorescent ethidium, revealed that chronic rotenone treatment caused a twofold increase in the rate of O(2)(-)* production. MitoQ (10 nM, 72 h) did not interfere with rotenone-induced ethidium formation but abolished rotenone-induced outgrowth and lipid peroxidation. These findings show that increased mitochondrial O(2)(-)* production as a consequence of, for instance, complex I inhibition leads to mitochondrial outgrowth and that MitoQ acts downstream of this O(2)(-)* to prevent alterations in mitochondrial morphology.
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Affiliation(s)
- Werner J H Koopman
- Microscopal Imaging Center, Department of Biochemistry, Nijmegen Center for Molecular Life Sciences, Radboud University Medical Center, PO Box 9101, NL-6500 HB Nijmegen, The Netherlands
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16
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Visch HJ, Rutter GA, Koopman WJH, Koenderink JB, Verkaart S, de Groot T, Varadi A, Mitchell KJ, van den Heuvel LP, Smeitink JAM, Willems PHGM. Inhibition of mitochondrial Na+-Ca2+ exchange restores agonist-induced ATP production and Ca2+ handling in human complex I deficiency. J Biol Chem 2004; 279:40328-36. [PMID: 15269216 DOI: 10.1074/jbc.m408068200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human mitochondrial complex I (NADH:ubiquinone oxidoreductase) of the oxidative phosphorylation system is a multiprotein assembly comprising both nuclear and mitochondrially encoded subunits. Deficiency of this complex is associated with numerous clinical syndromes ranging from highly progressive, often early lethal encephalopathies, of which Leigh disease is the most frequent, to neurodegenerative disorders in adult life, including Leber's hereditary optic neuropathy and Parkinson disease. We show here that the cytosolic Ca2+ signal in response to hormonal stimulation with bradykinin was impaired in skin fibroblasts from children between the ages of 0 and 5 years with an isolated complex I deficiency caused by mutations in nuclear encoded structural subunits of the complex. Inhibition of mitochondrial Na+-Ca2+ exchange by the benzothiazepine CGP37157 completely restored the aberrant cytosolic Ca2+ signal. This effect of the inhibitor was paralleled by complete restoration of the bradykinin-induced increases in mitochondrial Ca2+ concentration and ensuing ATP production. Thus, impaired mitochondrial Ca2+ accumulation during agonist stimulation is a major consequence of human complex I deficiency, a finding that may provide the basis for the development of new therapeutic approaches to this disorder.
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Affiliation(s)
- Henk-Jan Visch
- Department of Biochemistry and Pediatrics, University Medical Center Nijmegen, The Netherlands
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Koopman WJH, Renders M, Oosterhof A, van Kuppevelt TH, van Engelen BGM, Willems PHGM. Upregulation of Ca2+ removal in human skeletal muscle: a possible role for Ca2+-dependent priming of mitochondrial ATP synthesis. Am J Physiol Cell Physiol 2003; 285:C1263-9. [PMID: 12839829 DOI: 10.1152/ajpcell.00097.2003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In muscle, ATP is required for the powerstroke of the myosin head, the detachment of actin and myosin filaments, and the reuptake of Ca2+ into the sarcoplasmic reticulum. During contraction-relaxation, large amounts of ATP are consumed at the sites of action of the myosin-ATPase and sarcoplasmic reticulum Ca2+-ATPase. The present study addresses the consequences of a reduction in mitochondrial ATP production capacity on sarcoplasmic Ca2+ handling. To this end, myotubes were cultured from patient quadriceps with a biochemically defined decrease in the maximal rate of mitochondrial ATP production and were loaded with indo 1 for imaging of sarcoplasmic Ca2+ changes in real time by confocal microscopy. Myotubes were field-stimulated with 10-ms pulses of 16 V to evoke transient rises in sarcoplasmic Ca2+ concentration ([Ca2+]S). Three single pulses, two pulse trains (1 Hz), and one single pulse were applied in succession to mimic changing workloads. Control myotubes displayed [Ca2+]S transients with an amplitude that was independent of the strength of the stimulus. Intriguingly, the rate of sarcoplasmic Ca2+ removal (CRR) was significantly upregulated during the second and subsequent transients. In myotubes with a reduced mitochondrial ATP production capacity, the amplitude of the [Ca2+]S transients was markedly increased at higher stimulus intensities. Moreover, upregulation of the CRR was significantly decreased compared with control. Taken together, these results are in good agreement with a tight coupling between mitochondrial ATP production and sarcoplasmic Ca2+ handling. Moreover, they support the existence of a relatively long-lasting mitochondrial memory for sarcoplasmic [Ca2+] rises. This memory, which manifested itself as an increase in CRR upon recurrent stimulation, was impaired in patient myotubes with a reduced mitochondrial ATP production capacity.
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Affiliation(s)
- Werner J H Koopman
- 160 Biochemistry NCMLS, University Medical Center Nijmegen, PO Box 9101, NL-6500 HB Nijmegen, The Netherlands
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