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Contreras RG, Torres-Carrillo A, Flores-Maldonado C, Shoshani L, Ponce A. Na +/K +-ATPase: More than an Electrogenic Pump. Int J Mol Sci 2024; 25:6122. [PMID: 38892309 PMCID: PMC11172918 DOI: 10.3390/ijms25116122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 05/20/2024] [Accepted: 05/23/2024] [Indexed: 06/21/2024] Open
Abstract
The sodium pump, or Na+/K+-ATPase (NKA), is an essential enzyme found in the plasma membrane of all animal cells. Its primary role is to transport sodium (Na+) and potassium (K+) ions across the cell membrane, using energy from ATP hydrolysis. This transport creates and maintains an electrochemical gradient, which is crucial for various cellular processes, including cell volume regulation, electrical excitability, and secondary active transport. Although the role of NKA as a pump was discovered and demonstrated several decades ago, it remains the subject of intense research. Current studies aim to delve deeper into several aspects of this molecular entity, such as describing its structure and mode of operation in atomic detail, understanding its molecular and functional diversity, and examining the consequences of its malfunction due to structural alterations. Additionally, researchers are investigating the effects of various substances that amplify or decrease its pumping activity. Beyond its role as a pump, growing evidence indicates that in various cell types, NKA also functions as a receptor for cardiac glycosides like ouabain. This receptor activity triggers the activation of various signaling pathways, producing significant morphological and physiological effects. In this report, we present the results of a comprehensive review of the most outstanding studies of the past five years. We highlight the progress made regarding this new concept of NKA and the various cardiac glycosides that influence it. Furthermore, we emphasize NKA's role in epithelial physiology, particularly its function as a receptor for cardiac glycosides that trigger intracellular signals regulating cell-cell contacts, proliferation, differentiation, and adhesion. We also analyze the role of NKA β-subunits as cell adhesion molecules in glia and epithelial cells.
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Affiliation(s)
| | | | | | | | - Arturo Ponce
- Department of Physiology, Biophysics and Neurosciences, CINVESTAV-IPN, Mexico City 07360, Mexico; (R.G.C.); (A.T.-C.); (C.F.-M.); (L.S.)
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2
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Depierre P, Ginet V, Truttmann AC, Puyal J. Neuronal autosis is Na +/K +-ATPase alpha 3-dependent and involved in hypoxic-ischemic neuronal death. Cell Death Dis 2024; 15:363. [PMID: 38796484 PMCID: PMC11127954 DOI: 10.1038/s41419-024-06750-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 05/14/2024] [Accepted: 05/15/2024] [Indexed: 05/28/2024]
Abstract
Macroautophagy (hereafter called autophagy) is an essential physiological process of degradation of organelles and long-lived proteins. The discovery of autosis, a Na+/K+-ATPase (ATP1)-dependent type of autophagic cell death with specific morphological and biochemical features, has strongly contributed to the acceptance of a pro-death role of autophagy. However, the occurrence and relevance of autosis in neurons has never been clearly investigated, whereas we previously provided evidence that autophagy mechanisms could be involved in neuronal death in different in vitro and in vivo rodent models of hypoxia-ischemia (HI) and that morphological features of autosis were observed in dying neurons following rat perinatal cerebral HI. In the present study, we demonstrated that neuronal autosis could occur in primary cortical neurons using two different stimulations enhancing autophagy flux and neuronal death: a neurotoxic concentration of Tat-BECN1 (an autophagy-inducing peptide) and a hypoxic/excitotoxic stimulus (mimicking neuronal death induced by cerebral HI). Both stimulations induce autophagic neuronal death (dependent on canonical autophagic genes and independent on apoptotic, necroptotic or ferroptotic pathways) with all morphological and biochemical (ATP1a-dependent) features of autosis. However, we demonstrated that autosis is not dependent on the ubiquitous subunit ATP1a1 in neurons, as in dividing cell types, but on the neuronal specific ATP1a3 subunit. We also provided evidence that, in different in vitro and in vivo models where autosis is induced, ATP1a3-BECN1 interaction is increased and prevented by cardiac glycosides treatment. Interestingly, an increase in ATP1a3-BECN1 interaction is also detected in dying neurons in the autoptic brains of human newborns with severe hypoxic-ischemic encephalopathy (HIE). Altogether, these results suggest that ATP1a3-BECN1-dependent autosis could play an important role in neuronal death in HI conditions, paving the way for the development of new neuroprotective strategies in hypoxic-ischemic conditions including in severe case of human HIE.
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Affiliation(s)
- Pauline Depierre
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Vanessa Ginet
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
- Clinic of Neonatology, Department of Women, Mother and Child, University Hospital Center of Vaud, Lausanne, Switzerland
| | - Anita C Truttmann
- Clinic of Neonatology, Department of Women, Mother and Child, University Hospital Center of Vaud, Lausanne, Switzerland
| | - Julien Puyal
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland.
- CURML, University Center of Legal Medicine, Lausanne University Hospital, Lausanne, Switzerland.
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Harich OO, Gavriliuc OI, Ordodi VL, Tirziu A, Paunescu V, Panaitescu C, Bojin MF. In Vitro Study of the Multimodal Effect of Na +/K + ATPase Blocker Ouabain on the Tumor Microenvironment and Malignant Cells. Biomedicines 2023; 11:2205. [PMID: 37626702 PMCID: PMC10452365 DOI: 10.3390/biomedicines11082205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 07/31/2023] [Accepted: 08/03/2023] [Indexed: 08/27/2023] Open
Abstract
Na+/K+ ATPase is a protein involved in the active transport of ions across the cellular membrane. Ouabain is a cardiotonic glycoside that, by inhibiting the Na+/K+ pump, interferes with cell processes mediated directly by the pump, but also indirectly influences other cellular processes such as cell cycle and proliferation, growth, cell differentiation, angiogenesis, migration, adhesion, and invasion. We used the SK-BR-3 breast cancer cell line, mesenchymal stem cells (MSCs), and tumor-associated fibroblasts (TAFs) in vitro to determine the effects of ouabain exposure on these cellular types. The results showed a multi-level effect of ouabain mainly on tumor cells, in a dose-dependent manner, while the TAFs and their normal counterparts were not significantly influenced. Following exposure to ouabain, the SK-BR-3 cells changed their morphologic appearance, decreased the expression of immunophenotypic markers (CD29, Her2, VEGF), the proliferation rate was significantly decreased (Ki67 index), the cells were blocked in the G0 phase of the cell cycle and suffered necrosis. These data were correlated with the variable expression of α and β Na+/K+ pump subunits in tumor cells, resulting in decreased ability to adhere to the VCAM-1 substrate in functional flow chamber studies. Being indicative of the pro-apoptotic and inhibitory effect of ouabain on tumor invasion and metastasis, the results support the addition of ouabain to the oncological therapeutic arsenal, trailing the "repurposing drugs" approach.
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Affiliation(s)
- Octavia-Oana Harich
- Department of Functional Sciences, Immuno-Physiology and Biotechnologies Center, “Victor Babes” University of Medicine and Pharmacy, No. 2 Eftimie Murgu Square, 300041 Timisoara, Romania; (O.-O.H.); (V.-L.O.); (A.T.); (V.P.); (C.P.); (M.-F.B.)
| | - Oana-Isabella Gavriliuc
- Department of Functional Sciences, Immuno-Physiology and Biotechnologies Center, “Victor Babes” University of Medicine and Pharmacy, No. 2 Eftimie Murgu Square, 300041 Timisoara, Romania; (O.-O.H.); (V.-L.O.); (A.T.); (V.P.); (C.P.); (M.-F.B.)
| | - Valentin-Laurentiu Ordodi
- Department of Functional Sciences, Immuno-Physiology and Biotechnologies Center, “Victor Babes” University of Medicine and Pharmacy, No. 2 Eftimie Murgu Square, 300041 Timisoara, Romania; (O.-O.H.); (V.-L.O.); (A.T.); (V.P.); (C.P.); (M.-F.B.)
- Faculty of Industrial Chemistry and Environmental Engineering, “Politehnica” University Timisoara, No 2 Victoriei Square, 300006 Timisoara, Romania
| | - Alexandru Tirziu
- Department of Functional Sciences, Immuno-Physiology and Biotechnologies Center, “Victor Babes” University of Medicine and Pharmacy, No. 2 Eftimie Murgu Square, 300041 Timisoara, Romania; (O.-O.H.); (V.-L.O.); (A.T.); (V.P.); (C.P.); (M.-F.B.)
| | - Virgil Paunescu
- Department of Functional Sciences, Immuno-Physiology and Biotechnologies Center, “Victor Babes” University of Medicine and Pharmacy, No. 2 Eftimie Murgu Square, 300041 Timisoara, Romania; (O.-O.H.); (V.-L.O.); (A.T.); (V.P.); (C.P.); (M.-F.B.)
- Center for Gene and Cellular Therapies in the Treatment of Cancer Timisoara-OncoGen, Clinical Emergency County Hospital “Pius Brinzeu” Timisoara, No. 156 Liviu Rebreanu, 300723 Timisoara, Romania
| | - Carmen Panaitescu
- Department of Functional Sciences, Immuno-Physiology and Biotechnologies Center, “Victor Babes” University of Medicine and Pharmacy, No. 2 Eftimie Murgu Square, 300041 Timisoara, Romania; (O.-O.H.); (V.-L.O.); (A.T.); (V.P.); (C.P.); (M.-F.B.)
- Center for Gene and Cellular Therapies in the Treatment of Cancer Timisoara-OncoGen, Clinical Emergency County Hospital “Pius Brinzeu” Timisoara, No. 156 Liviu Rebreanu, 300723 Timisoara, Romania
| | - Maria-Florina Bojin
- Department of Functional Sciences, Immuno-Physiology and Biotechnologies Center, “Victor Babes” University of Medicine and Pharmacy, No. 2 Eftimie Murgu Square, 300041 Timisoara, Romania; (O.-O.H.); (V.-L.O.); (A.T.); (V.P.); (C.P.); (M.-F.B.)
- Center for Gene and Cellular Therapies in the Treatment of Cancer Timisoara-OncoGen, Clinical Emergency County Hospital “Pius Brinzeu” Timisoara, No. 156 Liviu Rebreanu, 300723 Timisoara, Romania
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A Low Dose of Ouabain Alters the Metabolic Profile of Adult Rats Experiencing Intrauterine Growth Restriction in a Sex-Specific Manner. Reprod Sci 2022; 30:1594-1607. [PMID: 36333644 DOI: 10.1007/s43032-022-01118-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022]
Abstract
Intrauterine growth restriction (IUGR) increases the risk of type 2 diabetes mellitus (T2DM) and metabolic diseases. The pancreas of fetuses with IUGR is usually characterized by pancreatic dysplasia and reduced levels of insulin secretion caused by the diminished replication of β-cells. Previous studies showed that a low dose of ouabain could reduce the apoptosis of embryonic nephric cells during IUGR and partially restore the number of nephrons at birth. The rescued kidneys functioned well and decreased the prevalence of hypertension. Thus, we hypothesized that ouabain could rescue pancreatic development during IUGR and reduce the morbidity of T2DM and metabolic diseases. Maternal malnutrition was used to induce the IUGR model, and then a low dose of ouabain was administered to rats with IUGR during pregnancy. Throughout the experiment, we monitored the pattern of weight increase and evaluated the metabolic parameters in the offspring in different stages. Male, but not female, offspring in the IUGR group presented catch-up growth. Ouabain could benefit the impaired glucose tolerance of male offspring; however, this desirable effect was eliminated by aging. The insulin sensitivity was significantly impaired in male offspring with IUGR, but it was improved by ouabain, even during old age. However, in the female offspring, low birth weight appeared to be a beneficial factor even in old age; administering ouabain exacerbated these favorable effects. Our data suggested that IUGR influenced glucose metabolism in a sex-specific manner and ouabain treatment during pregnancy exerted strongly contrasting effects in male and female rats.
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Leite JA, Pôças E, Maia GS, Barbosa L, Quintas LEM, Kawamoto EM, da Silva MLC, Scavone C, de Carvalho LED. Effect of ouabain on calcium signaling in rodent brain: A systematic review of in vitro studies. Front Pharmacol 2022; 13:916312. [PMID: 36105192 PMCID: PMC9465813 DOI: 10.3389/fphar.2022.916312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Accepted: 07/20/2022] [Indexed: 11/26/2022] Open
Abstract
The Na+/K+-ATPase is an integral membrane ion pump, essential to maintaining osmotic balance in cells in the presence of cardiotonic steroids; more specifically, ouabain can be an endogenous modulator of the Na+/K+-ATPase. Here, we conducted a systematic review of the in vitro effects of cardiotonic steroids on Ca2+ in the brain of rats and mice. Methods: The review was carried out using the PubMed, Virtual Health Library, and EMBASE databases (between 12 June 2020 and 30 June 2020) and followed the guidelines described in the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). Results: in total, 829 references were identified in the electronic databases; however, only 20 articles were considered, on the basis of the inclusion criteria. The studies demonstrated the effects of ouabain on Ca2+ signaling in synaptosomes, brain slices, and cultures of rat and mouse cells. In addition to the well-known cytotoxic effects of high doses of ouabain, resulting from indirect stimulation of the reverse mode of the Na+/Ca2+ exchanger and increased intracellular Ca2+, other effects have been reported. Ouabain-mediated Ca2+ signaling was able to act increasing cholinergic, noradrenergic and glutamatergic neurotransmission. Furthermore, ouabain significantly increased intracellular signaling molecules such as InsPs, IP3 and cAMP. Moreover treatment with low doses of ouabain stimulated myelin basic protein synthesis. Ouabain-induced intracellular Ca2+ increase may promote the activation of important cell signaling pathways involved in cellular homeostasis and function. Thus, the study of the application of ouabain in low doses being promising for application in neurological diseases. Systematic Review Registration:https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020204498, identifier CRD42020204498.
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Affiliation(s)
- Jacqueline Alves Leite
- Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, Brazil
| | - Elisa Pôças
- Campus Realengo, Instituto Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Gisele Silva Maia
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindu, São Paulo, Brazil
| | - Leandro Barbosa
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindu, São Paulo, Brazil
| | - Luis Eduardo M. Quintas
- Laboratório de Farmacologia Bioquímica e Molecular, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Elisa Mitiko Kawamoto
- Departamento de Farmacologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | | | - Cristoforo Scavone
- Departamento de Farmacologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Luciana E. Drumond de Carvalho
- Laboratório de Bioquímica Celular, Universidade Federal de São João del Rei, Campus Centro-Oeste Dona Lindu, São Paulo, Brazil
- *Correspondence: Luciana E. Drumond de Carvalho,
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6
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Long Q, Feng L, Li Y, Zuo T, Chang L, Zhang Z, Xu P. Time-resolved quantitative phosphoproteomics reveals cellular responses induced by caffeine and coumarin. Toxicol Appl Pharmacol 2022; 449:116115. [PMID: 35691368 DOI: 10.1016/j.taap.2022.116115] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Revised: 05/27/2022] [Accepted: 06/06/2022] [Indexed: 11/30/2022]
Abstract
Protein phosphorylation is a critical way that cells respond to external signals and environmental stresses. However, the patterns of cellular response to chemicals at different times were largely unknown. Here, we used quantitative phosphoproteomics to analyze the cellular response of kinases and signaling pathways, as well as pattern change of phosphorylated substrates in HepG2 cells that were exposed to caffeine and coumarin for 10 min and 24 h. Comparing the 10 min and 24 h groups, 33 kinases were co-responded and 32 signaling pathways were co-enriched in caffeine treated samples, while 48 kinases and 34 signaling pathways were co-identified in coumarin treated samples. Instead, the percentage of co-identified phosphorylated substrates only accounted for 4.31% and 9.57% between 10 min and 24 h in caffeine and coumarin treated samples, respectively. The results showed that specific chemical exposure led to a bunch of the same kinases and signaling pathways changed in HepG2 cells, while the phosphorylated substrates were different. In addition, it was found that insulin signaling pathway was significantly enriched by both the caffeine and coumarin treatment. The pattern changes in phosphorylation of protein substrates, kinases and signaling pathways with varied chemicals and different time course shed light on the potential mechanism of cellular responses to endless chemical stimulation.
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Affiliation(s)
- Qi Long
- School of Basic Medicine, Anhui Medical University, Hefei 230032, China; State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, Beijing 102206, China
| | - Lijie Feng
- School of Basic Medicine, Anhui Medical University, Hefei 230032, China
| | - Yuan Li
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, Beijing 102206, China; School of Medicine, Guizhou University, Guiyang 550025, China
| | - Tao Zuo
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, Beijing 102206, China
| | - Lei Chang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, Beijing 102206, China
| | - Zhenpeng Zhang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, Beijing 102206, China.
| | - Ping Xu
- School of Basic Medicine, Anhui Medical University, Hefei 230032, China; State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Research Unit of Proteomics & Research and Development of New Drug of Chinese Academy of Medical Sciences, Institute of Lifeomics, Beijing 102206, China; School of Medicine, Guizhou University, Guiyang 550025, China; School of Public Health, China Medical University, Shenyang 110122, China; Hebei Province Key Lab of Research and Application on Microbial Diversity, College of Life Sciences, Hebei University, Baoding 071002, China.
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7
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Integrated Analysis of mRNAs and Long Non-Coding RNAs Expression of Oviduct That Provides Novel Insights into the Prolificacy Mechanism of Goat ( Capra hircus). Genes (Basel) 2022; 13:genes13061031. [PMID: 35741792 PMCID: PMC9222479 DOI: 10.3390/genes13061031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 05/27/2022] [Accepted: 06/06/2022] [Indexed: 02/04/2023] Open
Abstract
Artificial directional selection has replaced natural selection and resulted in trait differences across breeds in domestic animal breeding. However, the molecular mechanism by which the oviduct regulates litter size remains largely elusive in goats during the follicular phase. Accumulating data have linked lncRNAs to reproductive activities; however, little is known about the modulation mechanism in the oviduct. Herein, RNA-seq was used to measure mRNA and lncRNA expression levels in low- and high-fecundity goats. We observed distinctive differences in mRNA and lncRNA in terms of different kidding numbers and detected the differential expression of 1640 mRNA transcripts and 271 lncRNA transcripts. Enrichment analysis of differentially expressed mRNAs (DEGs) suggested that multiple pathways, such as the AMPK, PI3K–Akt, calcium signaling pathway, oocyte meiosis, ABC transporter, and ECM–receptor interaction pathways, directly or indirectly affected goat reproduction. Additionally, coexpression of differentially expressed lncRNAs (DEL)-genes analysis showed that XLOC_021615, XLOC_119780, and XLOC_076450 were trans-acting as the DEGs ATAD2, DEPDC5, and TRPM6, respectively, and could regulate embryo development. Moreover, XLOC_020079, XLOC_107361, XLOC_169844, XLOC_252348 were the trans-regulated elements of the DEGs ARHGEF2 and RAPGEF6, and the target DEGs CPEB3 of XLOC_089239, XLOC_090063, XLOC_107409, XLOC_153574, XLOC_211271, XLOC_251687 were associated with prolificacy. Collectively, our study has offered a thorough dissection of the oviduct lncRNA and mRNA landscapes in goats. These results could serve as potential targets of the oviduct affecting fertility in goats.
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Bernhem K, Fontana JM, Svensson D, Zhang L, Nilsson LM, Scott L, Blom H, Brismar H, Aperia A. Super-resolution microscopy reveals that Na +/K +-ATPase signaling protects against glucose-induced apoptosis by deactivating Bad. Cell Death Dis 2021; 12:739. [PMID: 34315852 PMCID: PMC8316575 DOI: 10.1038/s41419-021-04025-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 07/14/2021] [Accepted: 07/14/2021] [Indexed: 11/08/2022]
Abstract
Activation of the apoptotic pathway is a major cause of progressive loss of function in chronic diseases such as neurodegenerative and diabetic kidney diseases. There is an unmet need for an anti-apoptotic drug that acts in the early stage of the apoptotic process. The multifunctional protein Na+,K+-ATPase has, in addition to its role as a transporter, a signaling function that is activated by its ligand, the cardiotonic steroid ouabain. Several lines of evidence suggest that sub-saturating concentrations of ouabain protect against apoptosis of renal epithelial cells, a common complication and major cause of death in diabetic patients. Here, we induced apoptosis in primary rat renal epithelial cells by exposing them to an elevated glucose concentration (20 mM) and visualized the early steps in the apoptotic process using super-resolution microscopy. Treatment with 10 nM ouabain interfered with the onset of the apoptotic process by inhibiting the activation of the BH3-only protein Bad and its translocation to mitochondria. This occurred before the pro-apoptotic protein Bax had been recruited to mitochondria. Two ouabain regulated and Akt activating Ca2+/calmodulin-dependent kinases were found to play an essential role in the ouabain anti-apoptotic effect. Our results set the stage for further exploration of ouabain as an anti-apoptotic drug in diabetic kidney disease as well as in other chronic diseases associated with excessive apoptosis.
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Affiliation(s)
- Kristoffer Bernhem
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Solna, Sweden
| | - Jacopo M Fontana
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Solna, Sweden
| | - Daniel Svensson
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden
| | - Liang Zhang
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden
| | - Linnéa M Nilsson
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Solna, Sweden
| | - Lena Scott
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden
| | - Hans Blom
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Solna, Sweden
| | - Hjalmar Brismar
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Solna, Sweden.
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden.
| | - Anita Aperia
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden
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9
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Jeong H, Yu Y, Johansson HJ, Schroeder FC, Lehtiö J, Vacanti NM. Correcting for Naturally Occurring Mass Isotopologue Abundances in Stable-Isotope Tracing Experiments with PolyMID. Metabolites 2021; 11:310. [PMID: 34066041 PMCID: PMC8151723 DOI: 10.3390/metabo11050310] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 05/03/2021] [Accepted: 05/05/2021] [Indexed: 11/20/2022] Open
Abstract
Stable-isotope tracing is a method to measure intracellular metabolic pathway utilization by feeding a cellular system a stable-isotope-labeled tracer nutrient. The power of the method to resolve differential pathway utilization is derived from the enrichment of metabolites in heavy isotopes that are synthesized from the tracer nutrient. However, the readout is complicated by the presence of naturally occurring heavy isotopes that are not derived from the tracer nutrient. Herein we present an algorithm, and a tool that applies it (PolyMID-Correct, part of the PolyMID software package), to computationally remove the influence of naturally occurring heavy isotopes. The algorithm is applicable to stable-isotope tracing data collected on low- and high- mass resolution mass spectrometers. PolyMID-Correct is open source and available under an MIT license.
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Affiliation(s)
- Heesoo Jeong
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA;
| | - Yan Yu
- Boyce Thompson Institute and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA; (Y.Y.); (F.C.S.)
| | - Henrik J. Johansson
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, 17165 Solna, Sweden; (H.J.J.); (J.L.)
| | - Frank C. Schroeder
- Boyce Thompson Institute and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA; (Y.Y.); (F.C.S.)
| | - Janne Lehtiö
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, 17165 Solna, Sweden; (H.J.J.); (J.L.)
| | - Nathaniel M. Vacanti
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA;
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, 17165 Solna, Sweden; (H.J.J.); (J.L.)
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10
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Bejček J, Spiwok V, Kmoníčková E, Rimpelová S. Na +/K +-ATPase Revisited: On Its Mechanism of Action, Role in Cancer, and Activity Modulation. Molecules 2021; 26:molecules26071905. [PMID: 33800655 PMCID: PMC8061769 DOI: 10.3390/molecules26071905] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/18/2021] [Accepted: 03/24/2021] [Indexed: 01/08/2023] Open
Abstract
Maintenance of Na+ and K+ gradients across the cell plasma membrane is an essential process for mammalian cell survival. An enzyme responsible for this process, sodium-potassium ATPase (NKA), has been currently extensively studied as a potential anticancer target, especially in lung cancer and glioblastoma. To date, many NKA inhibitors, mainly of natural origin from the family of cardiac steroids (CSs), have been reported and extensively studied. Interestingly, upon CS binding to NKA at nontoxic doses, the role of NKA as a receptor is activated and intracellular signaling is triggered, upon which cancer cell death occurs, which lies in the expression of different NKA isoforms than in healthy cells. Two major CSs, digoxin and digitoxin, originally used for the treatment of cardiac arrhythmias, are also being tested for another indication—cancer. Such drug repositioning has a big advantage in smoother approval processes. Besides this, novel CS derivatives with improved performance are being developed and evaluated in combination therapy. This article deals with the NKA structure, mechanism of action, activity modulation, and its most important inhibitors, some of which could serve not only as a powerful tool to combat cancer, but also help to decipher the so-far poorly understood NKA regulation.
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Affiliation(s)
- Jiří Bejček
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 3, 166 28 Prague 6, Czech Republic; (J.B.); (V.S.)
| | - Vojtěch Spiwok
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 3, 166 28 Prague 6, Czech Republic; (J.B.); (V.S.)
| | - Eva Kmoníčková
- Department of Pharmacology, Second Faculty of Medicine, Charles University, Plzeňská 311, 150 00 Prague, Czech Republic;
| | - Silvie Rimpelová
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 3, 166 28 Prague 6, Czech Republic; (J.B.); (V.S.)
- Faculty of Medicine in Pilsen, Charles University, Alej Svobody 76, 323 00 Pilsen, Czech Republic
- Correspondence: ; Tel.: +420-220-444-360
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11
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Lopachev AV, Lagarkova MA, Lebedeva OS, Ezhova MA, Kazanskaya RB, Timoshina YA, Khutorova AV, Akkuratov EE, Fedorova TN, Gainetdinov RR. Ouabain-Induced Gene Expression Changes in Human iPSC-Derived Neuron Culture Expressing Dopamine and cAMP-Regulated Phosphoprotein 32 and GABA Receptors. Brain Sci 2021; 11:brainsci11020203. [PMID: 33562186 PMCID: PMC7915459 DOI: 10.3390/brainsci11020203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/27/2021] [Accepted: 02/03/2021] [Indexed: 12/22/2022] Open
Abstract
Cardiotonic steroids (CTS) are specific inhibitors and endogenous ligands of a key enzyme in the CNS-the Na+, K+-ATPase, which maintains and creates an ion gradient on the plasma membrane of neurons. CTS cause the activation of various signaling cascades and changes in gene expression in neurons and other cell types. It is known that intracerebroventricular injection of cardiotonic steroid ouabain causes mania-like behavior in rodents, in part due to activation of dopamine-related signaling cascades in the dopamine and cAMP-regulated phosphoprotein 32 (DARPP-32) expressing medium spiny neurons in the striatum. Dopaminergic projections in the striatum innervate these GABAergic medium spiny neurons. The objective of this study was to assess changes in the expression of all genes in human iPSC-derived expressing DARPP-32 and GABA receptors neurons under the influence of ouabain. We noted a large number of statistically significant upregulated and downregulated genes after a 16-h incubation with non-toxic concentration (30 nM) of ouabain. These changes in the transcriptional activity were accomplished with activation of MAP-kinase ERK1/2 and transcriptional factor cAMP response element-binding protein (CREB). Thus, it can be concluded that 30 nM ouabain incubated for 16 h with human iPSC-derived expressing DARPP-32 and GABA receptors neurons activates genes associated with neuronal maturation and synapse formation, by increasing the expression of genes associated with translation, vesicular transport, and increased electron transport chain function. At the same time, the expression of genes associated with proliferation, migration, and early development of neurons decreases. These data indicate that non-toxic concentrations of ouabain may induce neuronal maturation, neurite growth, and increased synaptogenesis in dopamine-receptive GABAergic neurons, suggesting formation of plasticity and the establishment of new neuronal junctions.
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Affiliation(s)
- Alexander V. Lopachev
- Laboratory of Clinical and Experimental Neurochemistry, Research Center of Neurology, 125367 Moscow, Russia; (Y.A.T.); (A.V.K.); (T.N.F.)
- Correspondence:
| | - Maria A. Lagarkova
- Laboratory of Cell Biology, Federal Research and Clinical Center of Physical-Chemical Medicine Federal Medical Biological Agency, 119435 Moscow, Russia; (M.A.L.); (O.S.L.)
| | - Olga S. Lebedeva
- Laboratory of Cell Biology, Federal Research and Clinical Center of Physical-Chemical Medicine Federal Medical Biological Agency, 119435 Moscow, Russia; (M.A.L.); (O.S.L.)
| | - Margarita A. Ezhova
- Laboratory of Plant Genomics, Institute for Information Transmission Problems of the Russian Academy of Sciences, 127051 Moscow, Russia;
- Center of Life Sciences, Skolkovo Institute of Science and Technology, 121205 Moscow, Russia
| | - Rogneda B. Kazanskaya
- Biological Department, Saint Petersburg State University, 199034 St. Petersburg, Russia;
| | - Yulia A. Timoshina
- Laboratory of Clinical and Experimental Neurochemistry, Research Center of Neurology, 125367 Moscow, Russia; (Y.A.T.); (A.V.K.); (T.N.F.)
- Biological Department, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Anastasiya V. Khutorova
- Laboratory of Clinical and Experimental Neurochemistry, Research Center of Neurology, 125367 Moscow, Russia; (Y.A.T.); (A.V.K.); (T.N.F.)
- Biological Department, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Evgeny E. Akkuratov
- Department of Applied Physics, Royal Institute of Technology, Science for Life Laboratory, 171 65 Stockholm, Sweden;
| | - Tatiana N. Fedorova
- Laboratory of Clinical and Experimental Neurochemistry, Research Center of Neurology, 125367 Moscow, Russia; (Y.A.T.); (A.V.K.); (T.N.F.)
| | - Raul R. Gainetdinov
- Institute of Translational Biomedicine and Saint Petersburg University Hospital, Saint Petersburg State University, 199034 St. Petersburg, Russia;
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12
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Bubis JA, Gorshkov V, Gorshkov MV, Kjeldsen F. PhosphoShield: Improving Trypsin Digestion of Phosphoproteins by Shielding the Negatively Charged Phosphate Moiety. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:2053-2060. [PMID: 32840367 DOI: 10.1021/jasms.0c00171] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Protein phosphorylation is a post-translational modification that is essential to cellular signaling, cellular function, and associated disease progression. Bottom-up proteomics based on enzymatic digestion is the most widely used approach for identifying and quantifying phosphoproteins in complex biological samples. Researchers have largely optimized the experimental conditions for trypsin digestion, and it is now a routine procedure. However, trypsin digestion is impaired by the presence of phosphorylated residues in the protein sequence. This impairment arises from the fact that there are commonly salt bridges between a negatively charged phosphate group and the side chain of protonated arginine or lysine. On average, 55% of all phosphopeptides have their phosphosites located less than three amino acid residues from a cleavage site. Salt bridges reduce the cleavage accessibility for trypsin by masking the basic site chain groups of arginine and lysine. Thus, there are frequent missed cleavages in the vicinity of phosphorylation sites, thereby lessening both the depth of proteome coverage and the quantification accuracy of phosphoproteomics. In this work, we propose a method termed PhosphoShield to mitigate salt bridge formation by adding a digallium complex that exhibits a high binding affinity to the phosphate group. We tested our method using quantitative mass spectrometry analysis of the phosphoproteome of human liver cancer cells (HepG2). PhosphoShield enhances the cleavage frequency of at least 17% of tryptic phosphopeptides having cleavage sites close to the phosphate group.
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Affiliation(s)
- Julia A Bubis
- V. L. Talrose Institute for Energy Problems of Chemical Physics, N. N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119334 Moscow, Russia
- Moscow Institute of Physics and Technology (State University), 141700 Dolgoprudny, Russia
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Vladimir Gorshkov
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Mikhail V Gorshkov
- V. L. Talrose Institute for Energy Problems of Chemical Physics, N. N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119334 Moscow, Russia
| | - Frank Kjeldsen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
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13
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Pirkmajer S, Bezjak K, Matkovič U, Dolinar K, Jiang LQ, Miš K, Gros K, Milovanova K, Pirkmajer KP, Marš T, Kapilevich L, Chibalin AV. Ouabain Suppresses IL-6/STAT3 Signaling and Promotes Cytokine Secretion in Cultured Skeletal Muscle Cells. Front Physiol 2020; 11:566584. [PMID: 33101052 PMCID: PMC7544989 DOI: 10.3389/fphys.2020.566584] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 08/25/2020] [Indexed: 12/16/2022] Open
Abstract
The cardiotonic steroids (CTS), such as ouabain and marinobufagenin, are thought to be adrenocortical hormones secreted during exercise and the stress response. The catalytic α-subunit of Na,K-ATPase (NKA) is a CTS receptor, whose largest pool is located in skeletal muscles, indicating that muscles are a major target for CTS. Skeletal muscles contribute to adaptations to exercise by secreting interleukin-6 (IL-6) and plethora of other cytokines, which exert paracrine and endocrine effects in muscles and non-muscle tissues. Here, we determined whether ouabain, a prototypical CTS, modulates IL-6 signaling and secretion in the cultured human skeletal muscle cells. Ouabain (2.5–50 nM) suppressed the abundance of STAT3, a key transcription factor downstream of the IL-6 receptor, as well as its basal and IL-6-stimulated phosphorylation. Conversely, ouabain (50 nM) increased the phosphorylation of ERK1/2, Akt, p70S6K, and S6 ribosomal protein, indicating activation of the ERK1/2 and the Akt-mTOR pathways. Proteasome inhibitor MG-132 blocked the ouabain-induced suppression of the total STAT3, but did not prevent the dephosphorylation of STAT3. Ouabain (50 nM) suppressed hypoxia-inducible factor-1α (HIF-1α), a modulator of STAT3 signaling, but gene silencing of HIF-1α and/or its partner protein HIF-1β did not mimic effects of ouabain on the phosphorylation of STAT3. Ouabain (50 nM) failed to suppress the phosphorylation of STAT3 and HIF-1α in rat L6 skeletal muscle cells, which express the ouabain-resistant α1-subunit of NKA. We also found that ouabain (100 nM) promoted the secretion of IL-6, IL-8, GM-CSF, and TNF-α from the skeletal muscle cells of healthy subjects, and the secretion of GM-CSF from cells of subjects with the type 2 diabetes. Marinobufagenin (10 nM), another important CTS, did not alter the secretion of these cytokines. In conclusion, our study shows that ouabain suppresses the IL-6 signaling via STAT3, but promotes the secretion of IL-6 and other cytokines, which might represent a negative feedback in the IL-6/STAT3 pathway. Collectively, our results implicate a role for CTS and NKA in regulation of the IL-6 signaling and secretion in skeletal muscle.
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Affiliation(s)
- Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Katja Bezjak
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Urška Matkovič
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Klemen Dolinar
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Lake Q Jiang
- Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Katarina Miš
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Katarina Gros
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Kseniya Milovanova
- Department of Sports and Health Tourism, Sports Physiology and Medicine, National Research Tomsk State University, Tomsk, Russia
| | - Katja Perdan Pirkmajer
- Department of Rheumatology, University Medical Centre Ljubljana, Ljubljana, Slovenia.,Department of Internal Medicine, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Tomaž Marš
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Leonid Kapilevich
- Department of Sports and Health Tourism, Sports Physiology and Medicine, National Research Tomsk State University, Tomsk, Russia.,Central Scientific Laboratory, Siberian State Medical University, Tomsk, Russia
| | - Alexander V Chibalin
- Integrative Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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14
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Akkuratov EE, Westin L, Vazquez-Juarez E, de Marothy M, Melnikova AK, Blom H, Lindskog M, Brismar H, Aperia A. Ouabain Modulates the Functional Interaction Between Na,K-ATPase and NMDA Receptor. Mol Neurobiol 2020; 57:4018-4030. [PMID: 32651756 PMCID: PMC7467916 DOI: 10.1007/s12035-020-01984-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 06/08/2020] [Indexed: 12/18/2022]
Abstract
The N-methyl-D-aspartate (NMDA) receptor plays an essential role in glutamatergic transmission and synaptic plasticity and researchers are seeking for different modulators of NMDA receptor function. One possible mechanism for its regulation could be through adjacent membrane proteins. NMDA receptors coprecipitate with Na,K-ATPase, indicating a potential interaction of these two proteins. Ouabain, a mammalian cardiotonic steroid that specifically binds to Na,K-ATPase and affects its conformation, can protect from some toxic effects of NMDA receptor activation. Here we have examined whether NMDA receptor activity and downstream effects can be modulated by physiological ouabain concentrations. The spatial colocalization between NMDA receptors and the Na,K-ATPase catalytic subunits on dendrites of cultured rat hippocampal neurons was analyzed with super-resolution dSTORM microscopy. The functional interaction was analyzed with calcium imaging of single hippocampal neurons exposed to 10 μM NMDA in presence and absence of ouabain and by determination of the ouabain effect on NMDA receptor–dependent long-term potentiation. We show that NMDA receptors and the Na,K-ATPase catalytic subunits alpha1 and alpha3 exist in same protein complex and that ouabain in nanomolar concentration consistently reduces the calcium response to NMDA. Downregulation of the NMDA response is not associated with internalization of the receptor or with alterations in its state of Src phosphorylation. Ouabain in nanomolar concentration elicits a long-term potentiation response. Our findings suggest that ouabain binding to a fraction of Na,K-ATPase molecules that cluster with the NMDA receptors will, via a conformational effect on the NMDA receptors, cause moderate but consistent reduction of NMDA receptor response at synaptic activation.
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Affiliation(s)
- Evgeny E Akkuratov
- Science for Life Laboratory, Department of Applied Physics, Kungliga Tekniska Högskolan, Stockholm, Sweden
| | - Linda Westin
- Science for Life Laboratory, Department of Women's and Children's health, Karolinska Institutet, Stockholm, Sweden
| | - Erika Vazquez-Juarez
- Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden
| | - Minttu de Marothy
- Science for Life Laboratory, Department of Women's and Children's health, Karolinska Institutet, Stockholm, Sweden
| | - Aleksandra K Melnikova
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia, 119234
| | - Hans Blom
- Science for Life Laboratory, Department of Applied Physics, Kungliga Tekniska Högskolan, Stockholm, Sweden
| | - Maria Lindskog
- Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden
| | - Hjalmar Brismar
- Science for Life Laboratory, Department of Applied Physics, Kungliga Tekniska Högskolan, Stockholm, Sweden.
| | - Anita Aperia
- Science for Life Laboratory, Department of Women's and Children's health, Karolinska Institutet, Stockholm, Sweden
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15
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Blaustein MP, Hamlyn JM. Ouabain, endogenous ouabain and ouabain-like factors: The Na + pump/ouabain receptor, its linkage to NCX, and its myriad functions. Cell Calcium 2020; 86:102159. [PMID: 31986323 DOI: 10.1016/j.ceca.2020.102159] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Revised: 01/01/2020] [Accepted: 01/03/2020] [Indexed: 12/12/2022]
Abstract
In this brief review we discuss some aspects of the Na+ pump and its roles in mediating the effects of ouabain and endogenous ouabain (EO): i) in regulating the cytosolic Ca2+ concentration ([Ca2+]CYT) via Na/Ca exchange (NCX), and ii) in activating a number of protein kinase (PK) signaling cascades that control a myriad of cell functions. Importantly, [Ca2+]CYT and the other signaling pathways intersect at numerous points because of the influence of Ca2+ and calmodulin in modulating some steps in those other pathways. While both mechanisms operate in virtually all cells and tissues, this article focuses primarily on their functions in the cardiovascular system, the central nervous system (CNS) and the kidneys.
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Affiliation(s)
- Mordecai P Blaustein
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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