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Wang X, Yu X, Gavardinas K, Dey A, Zhang HY, Porter G, Porras L, Yu L, Guo H, Reidy CA, Haas JV, Xu Y, Kowala MC, Jadhav PK, Wetterau JR. Effect of an NHE3 inhibitor in combination with an NPT2b inhibitor on gastrointestinal phosphate absorption in Rodent models. PLoS One 2024; 19:e0292091. [PMID: 38277356 PMCID: PMC10817170 DOI: 10.1371/journal.pone.0292091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 09/12/2023] [Indexed: 01/28/2024] Open
Abstract
Many of the pathological consequences of chronic kidney disease can be attributed to an elevation in serum phosphate levels. Current therapies focused on decreasing intestinal phosphate absorption to treat hyperphosphatemia are inadequate. The most effective therapeutic strategy may be to target multiple absorptive pathways. In this study, the ability of a novel inhibitor of the intestinal sodium hydrogen exchanger 3 (NHE3), LY3304000, which inhibits paracellular, diffusional uptake of phosphate, to work in combination with an inhibitor of the active transporter, sodium dependent phosphate cotransporter 2b (NPT2b), LY3358966, was explored. LY3304000 modestly inhibited the acute uptake of phosphate into plasma of rats, while surprisingly, it doubled the rate of phosphate uptake in mice, an animal model dominated by NPT2b mediated acute phosphate uptake. In rats, LY3004000 and LY3358966 work in concert to inhibit acute phosphate uptake. On top of LY3358966, LY3304000 further decreased the acute uptake of phosphate into plasma. Studies measuring the recovery of radiolabeled phosphate in the intestine demonstrated LY3304000 and LY3358966 synergistically inhibited the absorption of phosphate in rats. We hypothesize the synergism is because the NHE3 inhibitor, LY3304000, has two opposing effects on intestinal phosphate absorption in rats, first it decreases diffusion mediated paracellular phosphate absorption, while second, it simultaneously increases phosphate absorption through the NPT2b pathway. NHE3 inhibition decreases proton export from enterocytes and raises the cell surface pH. In vitro, NPT2b mediated phosphate transport is increased at higher pHs. The increased NPT2b mediated transport induced by NHE3 inhibition is masked in rats which have relatively low levels of NPT2b mediated phosphate transport, by the more robust inhibition of diffusion mediated phosphate absorption. Thus, the inhibition of NPT2b mediated phosphate transport in rats in the presence of NHE3 inhibition has an effect that exceeds its effect in the absence of NHE3 inhibition, leading to the observed synergism on phosphate absorption between NPT2b and NHE3 inhibition.
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Affiliation(s)
- Xiaojun Wang
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Xiaohong Yu
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Kostas Gavardinas
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Asim Dey
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Hong Y. Zhang
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Gina Porter
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Leah Porras
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Lan Yu
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Haihong Guo
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Charles A. Reidy
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Joseph V. Haas
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Yanping Xu
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Mark C. Kowala
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Prabhakar K. Jadhav
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - John R. Wetterau
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
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Poet M, Vigier N, Bouret Y, Jarretou G, Gautier R, Bendahhou S, Balter V, Montanes M, Thibon F, Counillon L. Biological fractionation of lithium isotopes by cellular Na +/H + exchangers unravels fundamental transport mechanisms. iScience 2023; 26:106887. [PMID: 37324528 PMCID: PMC10265516 DOI: 10.1016/j.isci.2023.106887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 03/08/2023] [Accepted: 05/10/2023] [Indexed: 06/17/2023] Open
Abstract
Lithium (Li) has a wide range of uses in science, medicine, and industry, but its isotopy is underexplored, except in nuclear science and in geoscience. 6Li and 7Li isotopic ratio exhibits the second largest variation on earth's surface and constitutes a widely used tool for reconstructing past oceans and climates. As large variations have been measured in mammalian organs, plants or marine species, and as 6Li elicits stronger effects than natural Li (∼95% 7Li), a central issue is the identification and quantification of biological influence of Li isotopes distribution. We show that membrane ion channels and Na+-Li+/H+ exchangers (NHEs) fractionate Li isotopes. This systematic 6Li enrichment is driven by membrane potential for channels, and by intracellular pH for NHEs, where it displays cooperativity, a hallmark of dimeric transport. Evidencing that transport proteins discriminate between isotopes differing by one neutron opens new avenues for transport mechanisms, Li physiology, and paleoenvironments.
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Affiliation(s)
- Mallorie Poet
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire (LP2M), Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - Nathalie Vigier
- Oceanography Laboratory of Villefranche (LOV, IMEV), CNRS, Sorbonne University, Villefranche-sur-Mer, France
| | - Yann Bouret
- Université Côte d’Azur, CNRS, Institut de Physique de Nice (INPHYNI), Nice, France
- École Normale Supérieure de Lyon, CNRS, Laboratoire de Géologie de Lyon, Lyon, France
| | - Gisèle Jarretou
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire (LP2M), Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - Romain Gautier
- Université Côte d’Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Valbonne, France
| | - Saïd Bendahhou
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire (LP2M), Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - Vincent Balter
- École Normale Supérieure de Lyon, CNRS, Laboratoire de Géologie de Lyon, Lyon, France
| | - Maryline Montanes
- Oceanography Laboratory of Villefranche (LOV, IMEV), CNRS, Sorbonne University, Villefranche-sur-Mer, France
| | - Fanny Thibon
- Oceanography Laboratory of Villefranche (LOV, IMEV), CNRS, Sorbonne University, Villefranche-sur-Mer, France
| | - Laurent Counillon
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire (LP2M), Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
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Rolver MG, Holland LKK, Ponniah M, Prasad NS, Yao J, Schnipper J, Kramer S, Elingaard‐Larsen L, Pedraz‐Cuesta E, Liu B, Pardo LA, Maeda K, Sandelin A, Pedersen SF. Chronic acidosis rewires cancer cell metabolism through PPARα signaling. Int J Cancer 2023; 152:1668-1684. [PMID: 36533672 PMCID: PMC10108231 DOI: 10.1002/ijc.34404] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 11/25/2022] [Accepted: 12/06/2022] [Indexed: 12/23/2022]
Abstract
The mechanisms linking tumor microenvironment acidosis to disease progression are not understood. Here, we used mammary, pancreatic, and colon cancer cells to show that adaptation to growth at an extracellular pH (pHe ) mimicking acidic tumor niches is associated with upregulated net acid extrusion capacity and elevated intracellular pH at physiological pHe , but not at acidic pHe . Using metabolic profiling, shotgun lipidomics, imaging and biochemical analyses, we show that the acid adaptation-induced phenotype is characterized by a shift toward oxidative metabolism, increased lipid droplet-, triacylglycerol-, peroxisome content and mitochondrial hyperfusion. Peroxisome proliferator-activated receptor-α (PPARA, PPARα) expression and activity are upregulated, at least in part by increased fatty acid uptake. PPARα upregulates genes driving increased mitochondrial and peroxisomal mass and β-oxidation capacity, including mitochondrial lipid import proteins CPT1A, CPT2 and SLC25A20, electron transport chain components, peroxisomal proteins PEX11A and ACOX1, and thioredoxin-interacting protein (TXNIP), a negative regulator of glycolysis. This endows acid-adapted cancer cells with increased capacity for utilizing fatty acids for metabolic needs, while limiting glycolysis. As a consequence, the acid-adapted cells exhibit increased sensitivity to PPARα inhibition. We conclude that PPARα is a key upstream regulator of metabolic changes favoring cancer cell survival in acidic tumor niches.
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Affiliation(s)
- Michala G. Rolver
- Section for Cell Biology and Physiology, Department of BiologyUniversity of CopenhagenCopenhagenDenmark
| | - Lya K. K. Holland
- Cell Death and Metabolism, Center for Autophagy, Recycling and Disease, Danish Cancer Society Research CenterCopenhagenDenmark
| | - Muthulakshmi Ponniah
- Section for Cell Biology and Physiology, Department of BiologyUniversity of CopenhagenCopenhagenDenmark
| | - Nanditha S. Prasad
- Section for Cell Biology and Physiology, Department of BiologyUniversity of CopenhagenCopenhagenDenmark
| | - Jiayi Yao
- The Bioinformatics Center, Department of BiologyUniversity of CopenhagenCopenhagenDenmark
- Biotech Research and Innovation Center, University of CopenhagenCopenhagenDenmark
| | - Julie Schnipper
- Laboratory of Cellular and Molecular Physiology, University of Picardie Jules VerneAmiensFrance
| | - Signe Kramer
- Section for Cell Biology and Physiology, Department of BiologyUniversity of CopenhagenCopenhagenDenmark
| | | | - Elena Pedraz‐Cuesta
- Section for Cell Biology and Physiology, Department of BiologyUniversity of CopenhagenCopenhagenDenmark
| | - Bin Liu
- Cell Death and Metabolism, Center for Autophagy, Recycling and Disease, Danish Cancer Society Research CenterCopenhagenDenmark
| | - Luis A. Pardo
- Oncophysiology Group, Max‐Planck‐Institute for Multidisciplinary SciencesGöttingenGermany
| | - Kenji Maeda
- Cell Death and Metabolism, Center for Autophagy, Recycling and Disease, Danish Cancer Society Research CenterCopenhagenDenmark
| | - Albin Sandelin
- The Bioinformatics Center, Department of BiologyUniversity of CopenhagenCopenhagenDenmark
- Biotech Research and Innovation Center, University of CopenhagenCopenhagenDenmark
| | - Stine Falsig Pedersen
- Section for Cell Biology and Physiology, Department of BiologyUniversity of CopenhagenCopenhagenDenmark
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Poet M, Doyen D, Van Obberghen E, Jarretou G, Bouret Y, Counillon L. How Does Our Knowledge on the Na+/H+ Exchanger NHE1 Obtained by Biochemical and Molecular Analyses Keep up With Its Recent Structure Determination? Front Physiol 2022; 13:907587. [PMID: 35910559 PMCID: PMC9334524 DOI: 10.3389/fphys.2022.907587] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 06/06/2022] [Indexed: 11/23/2022] Open
Abstract
Na+/H+ exchangers are membrane transporters conserved in all living systems and therefore are assumed to be amongst the most ancestral molecular devices that equipped the first protocells. Following the cloning and sequencing of its gene, the mammalian NHE1, that regulates pH and volume in all cells, has been thoroughly scrutinized by molecular and biochemical analyses. Those gave a series of crucial clues concerning its topology, dimeric organization, pharmacological profile, regulation, and the role of key amino acids. Recently thanks to cryogenic Electron Microscopy (Cryo-EM) the long-awaited molecular structures have been revealed. With this information in mind we will challenge the robustness of the earlier conclusions and highlight how the new information enriches our understanding of this key cellular player. At the mechanistic level, we will pinpoint how the NHE1 3D structures reveal that the previously identified amino acids and regions are organized to coordinate transported cations, and shape the allosteric transition that makes NHE1 able to sense intracellular pH and be regulated by signaling pathways.
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Affiliation(s)
- Mallorie Poet
- Université Côte d’Azur, CNRS, Laboratoire de PhysioMédecine Moléculaire (LP2M), Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - Denis Doyen
- Université Côte d’Azur, CNRS, Laboratoire de PhysioMédecine Moléculaire (LP2M), Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
- Centre Hospitalier Universitaire de Nice, Nice, France
| | - Emmanuel Van Obberghen
- Université Côte d’Azur, CNRS, Laboratoire de PhysioMédecine Moléculaire (LP2M), Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
- Centre Hospitalier Universitaire de Nice, Nice, France
| | - Gisèle Jarretou
- Université Côte d’Azur, CNRS, Laboratoire de PhysioMédecine Moléculaire (LP2M), Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - Yann Bouret
- Université Côte d’Azur, CNRS, Institut de Physique de Nice (INPHYNI), Valbonne, France
| | - Laurent Counillon
- Université Côte d’Azur, CNRS, Laboratoire de PhysioMédecine Moléculaire (LP2M), Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
- *Correspondence: Laurent Counillon,
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5
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'Warburg effect' controls tumor growth, bacterial, viral infections and immunity - Genetic deconstruction and therapeutic perspectives. Semin Cancer Biol 2022; 86:334-346. [PMID: 35820598 DOI: 10.1016/j.semcancer.2022.07.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 07/06/2022] [Accepted: 07/07/2022] [Indexed: 12/16/2022]
Abstract
The evolutionary pressure for life transitioning from extended periods of hypoxia to an increasingly oxygenated atmosphere initiated drastic selections for a variety of biochemical pathways supporting the robust life currently present on the planet. First, we discuss how fermentative glycolysis, a primitive metabolic pathway present at the emergence of life, is instrumental for the rapid growth of cancer, regenerating tissues, immune cells but also bacteria and viruses during infections. The 'Warburg effect', activated via Myc and HIF-1 in response to growth factors and hypoxia, is an essential metabolic and energetic pathway which satisfies nutritional and energetic demands required for rapid genome replication. Second, we present the key role of lactic acid, the end-product of fermentative glycolysis able to move across cell membranes in both directions via monocarboxylate transporting proteins (i.e. MCT1/4) contributing to cell-pH homeostasis but also to the complex immune response via acidosis of the tumour microenvironment. Importantly lactate is recycled in multiple organs as a major metabolic precursor of gluconeogenesis and energy source protecting cells and animals from harsh nutritional or oxygen restrictions. Third, we revisit the Warburg effect via CRISPR-Cas9 disruption of glucose-6-phosphate isomerase (GPI-KO) or lactate dehydrogenases (LDHA/B-DKO) in two aggressive tumours (melanoma B16-F10, human adenocarcinoma LS174T). Full suppression of lactic acid production reduces but does not suppress tumour growth due to reactivation of OXPHOS. In contrast, disruption of the lactic acid transporters MCT1/4 suppressed glycolysis, mTORC1, and tumour growth as a result of intracellular acidosis. Finally, we briefly discuss the current clinical developments of an MCT1 specific drug AZ3965, and the recent progress for a specific in vivo MCT4 inhibitor, two drugs of very high potential for future cancer clinical applications.
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6
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Doyen D, Poët M, Jarretou G, Pisani DF, Tauc M, Cougnon M, Argentina M, Bouret Y, Counillon L. Intracellular pH Control by Membrane Transport in Mammalian Cells. Insights Into the Selective Advantages of Functional Redundancy. Front Mol Biosci 2022; 9:825028. [PMID: 35252350 PMCID: PMC8896879 DOI: 10.3389/fmolb.2022.825028] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 01/06/2022] [Indexed: 12/16/2022] Open
Abstract
Intracellular pH is a vital parameter that is maintained close to neutrality in all mammalian cells and tissues and acidic in most intracellular compartments. After presenting the main techniques used for intracellular an vesicular pH measurements we will briefly recall the main molecular mechanisms that affect and regulate intracellular pH. Following this we will discuss the large functional redundancy found in the transporters of H+ or acid-base equivalents. For this purpose, we will use mathematical modeling to simulate cellular response to persistent and/or transient acidification, in the presence of different transporters, single or in combination. We will also test the presence or absence of intracellular buffering. This latter section will highlight how modeling can yield fundamental insight into deep biological questions such as the utility of functional redundancy in natural selection.
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Affiliation(s)
- Denis Doyen
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
- Centre Hospitalier Universitaire de Nice, Service de Médecine Intensive Réanimation, Hôpital Archet 1, Nice, France
| | - Mallorie Poët
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - Gisèle Jarretou
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - Didier F. Pisani
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - Michel Tauc
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - Marc Cougnon
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - Mederic Argentina
- Université Côte d’Azur, CNRS, Institut de Physique de Nice, INPHYNI, Nice, France
| | - Yann Bouret
- Centre Hospitalier Universitaire de Nice, Service de Médecine Intensive Réanimation, Hôpital Archet 1, Nice, France
| | - Laurent Counillon
- Université Côte d’Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, Nice, France
- Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
- *Correspondence: Laurent Counillon,
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Kovács BZ, Puskás LG, Nagy LI, Papp A, Gyöngyi Z, Fórizs I, Czuppon G, Somlyai I, Somlyai G. Blocking the Increase of Intracellular Deuterium Concentration Prevents the Expression of Cancer-Related Genes, Tumor Development, and Tumor Recurrence in Cancer Patients. Cancer Control 2022; 29:10732748211068963. [PMID: 35043700 PMCID: PMC8777325 DOI: 10.1177/10732748211068963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The possible role of the naturally occurring deuterium in the regulation of cell
division was first described in the 1990s. To investigate the mechanism of
influence of deuterium (D) on cell growth, expression of 236 cancer-related and
536 kinase genes were tested in deuterium-depleted (40 and 80 ppm) and
deuterium-enriched (300 ppm) media compared to natural D level (150 ppm). Among
genes with expression changes exceeding 30% and copy numbers over 30 (124 and
135 genes, respectively) 97.3% of them was upregulated at 300 ppm
D-concentration. In mice exposed to chemical carcinogen, one-year survival data
showed that deuterium-depleted water (DDW) with 30 ppm D as drinking water
prevented tumor development. One quarter of the treated male mice survived
344 days, the females 334 days, while one quarter of the control mice survived
only 188 and 156 days, respectively. In our human retrospective study 204
previously treated cancer patients with disease in remission, who consumed DDW,
were followed. Cumulative follow-up time was 1024 years, and average follow-up
time per patient, 5 years (median: 3.6 years). One hundred and fifty-six
patients out of 204 (77.9%) did not relapse during their 803 years cumulative
follow-up time. Median survival time (MST) was not calculable due to the
extremely low death rate (11 cancer-related deaths, 5.4% of the study
population). Importantly, 8 out of 11 deaths occurred several years after
stopping DDW consumption, confirming that regular consumption of DDW can prevent
recurrence of cancer. These findings point to the likely mechanism in which
consumption of DDW keeps D-concentration below natural levels, preventing the
D/H ratio from increasing to the threshold required for cell division. This in
turn can serve as a key to reduce the relapse rate of cancer patients and/or to
reduce cancer incidence in healthy populations.
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Affiliation(s)
- Beáta Zs. Kovács
- HYD LLC for Cancer Research and Drug Development, Budapest, Hungary
| | | | | | - András Papp
- Department of Public Health, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Zoltán Gyöngyi
- Department of Public Health, Medical School, University of Pécs, Pécs, Hungary
| | - István Fórizs
- Institute for Geological and Geochemical Research (IGGR), Research Centre for Astronomy and Earth Sciences, Eötvös Loránt Research Network, Budapest, Hungary
| | - György Czuppon
- Institute for Geological and Geochemical Research (IGGR), Research Centre for Astronomy and Earth Sciences, Eötvös Loránt Research Network, Budapest, Hungary
| | - Ildikó Somlyai
- HYD LLC for Cancer Research and Drug Development, Budapest, Hungary
| | - Gábor Somlyai
- HYD LLC for Cancer Research and Drug Development, Budapest, Hungary
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Glomerular Mesangial Cell pH Homeostasis Mediates Mineralocorticoid Receptor-Induced Cell Proliferation. Biomedicines 2021; 9:biomedicines9091117. [PMID: 34572303 PMCID: PMC8468551 DOI: 10.3390/biomedicines9091117] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/24/2021] [Accepted: 08/27/2021] [Indexed: 11/17/2022] Open
Abstract
Mineralocorticoids (e.g., aldosterone) support chronic inflammatory tissue damage, including glomerular mesangial injury leading to glomerulosclerosis. Furthermore, aldosterone leads to activation of the extracellular signal-regulated kinases (ERK1/2) in rat glomerular mesangial cells (GMC). Because ERK1/2 can affect cellular pH homeostasis via activation of Na+/H+-exchange (NHE) and the resulting cellular alkalinization may support proliferation, we tested the hypothesis that aldosterone affects pH homeostasis and thereby cell proliferation as well as collagen secretion also in primary rat GMC. Cytoplasmic pH and calcium were assessed by single-cell fluorescence ratio imaging, using the dyes BCECF or FURA2, respectively. Proliferation was determined by cell counting, thymidine incorporation and collagen secretion by collagenase-sensitive proline incorporation and ERK1/2-phosphorylation by Western blot. Nanomolar aldosterone induces a rapid cytosolic alkalinization which is prevented by NHE inhibition (10 µmol/L EIPA) and by blockade of the mineralocorticoid receptor (100 nmol/L spironolactone). pH changes were not affected by inhibition of HCO3- transporters and were not dependent on HCO3-. Aldosterone enhanced ERK1/2 phosphorylation and inhibition of ERK1/2-phosphorylation (10 µmol/L U0126) prevented aldosterone-induced alkalinization. Furthermore, aldosterone induced proliferation of GMC and collagen secretion, both of which were prevented by U0126 and EIPA. Cytosolic calcium was not involved in this aldosterone action. In conclusion, our data show that aldosterone can induce GMC proliferation via a MR and ERK1/2-mediated activation of NHE with subsequent cytosolic alkalinization. GMC proliferation leads to glomerular hypercellularity and dysfunction. This effect presents a possible mechanism contributing to mineralocorticoid receptor-induced pathogenesis of glomerular mesangial injury during chronic kidney disease.
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High Na + Salt Diet and Remodeling of Vascular Smooth Muscle and Endothelial Cells. Biomedicines 2021; 9:biomedicines9080883. [PMID: 34440087 PMCID: PMC8389691 DOI: 10.3390/biomedicines9080883] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/19/2021] [Accepted: 07/21/2021] [Indexed: 12/12/2022] Open
Abstract
Our knowledge on essential hypertension is vast, and its treatment is well known. Not all hypertensives are salt-sensitive. The available evidence suggests that even normotensive individuals are at high cardiovascular risk and lower survival rate, as blood pressure eventually rises later in life with a high salt diet. In addition, little is known about high sodium (Na+) salt diet-sensitive hypertension. There is no doubt that direct and indirect Na+ transporters, such as the Na/Ca exchanger and the Na/H exchanger, and the Na/K pump could be implicated in the development of high salt-induced hypertension in humans. These mechanisms could be involved following the destruction of the cell membrane glycocalyx and changes in vascular endothelial and smooth muscle cells membranes’ permeability and osmolarity. Thus, it is vital to determine the membrane and intracellular mechanisms implicated in this type of hypertension and its treatment.
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Zhou K, Amiri M, Salari A, Yu Y, Xu H, Seidler U, Nikolovska K. Functional characterization of the sodium/hydrogen exchanger 8 and its role in proliferation of colonic epithelial cells. Am J Physiol Cell Physiol 2021; 321:C471-C488. [PMID: 34288721 DOI: 10.1152/ajpcell.00582.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Intestinal NaCl, HCO3-, and fluid absorption are strongly dependent on apical Na+/H+ exchange. The intestine expresses three presumably apical sodium-hydrogen exchanger (NHE) isoforms: NHE2, NHE3, and NHE8. We addressed the role of NHE8 [solute carrier 9A8 (SLC9A8)] and its interplay with NHE2 (SLC9A2) in luminal proton extrusion during acute and chronic enterocyte acidosis and studied the differential effects of NHE8 and NHE2 on enterocyte proliferation. In contrast to NHE3, which was upregulated in differentiated versus undifferentiated colonoids, the expression of NHE2 and NHE8 remained constant during differentiation of colonoids and Caco2Bbe cells. Heterogeneously expressed Flag-tagged rat (r)Nhe8 and human (h)NHE8 translocated to the apical membrane of Caco2Bbe cells. rNhe8 and hNHE8, when expressed in NHE-deficient PS120 fibroblasts showed higher sensitivity to HOE642 compared to NHE2. Lentiviral shRNA knockdown of endogenous NHE2 in Caco2Bbe cells (C2Bbe/shNHE2) resulted in a decreased steady-state intracellular pH (pHi), an increased NHE8 mRNA expression, and augmented NHE8-mediated apical NHE activity. Lentiviral shRNA knockdown of endogenous NHE8 in Caco2Bbe cells (C2Bbe/shNHE8) resulted in a decreased steady-state pHi as well, accompanied by decreased NHE2 mRNA expression and activity, which together contributed to reduced apical NHE activity in the NHE8-knockdown cells. Chronic acidosis increased NHE8 but not NHE2 mRNA expression. Alterations in NHE2 and NHE8 expression/activity affected proliferation, with C2Bbe/shNHE2 cells having lower and C2Bbe/shNHE8 having higher proliferative capacity, accompanied by amplified ERK1/2 signaling pathway and increased EGFR expression in the latter cell line. Thus, both Na+/H+ exchangers have distinct functions during cellular homeostasis by triggering different signaling pathways to regulate cellular proliferation and pHi control.
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Affiliation(s)
- Kunyan Zhou
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Mahdi Amiri
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Azam Salari
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Yan Yu
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Hua Xu
- Department of Pediatrics, University of Arizona Health Science Center, Tucson, Arizona
| | - Ursula Seidler
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Katerina Nikolovska
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
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11
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Tharp KM, Higuchi-Sanabria R, Timblin GA, Ford B, Garzon-Coral C, Schneider C, Muncie JM, Stashko C, Daniele JR, Moore AS, Frankino PA, Homentcovschi S, Manoli SS, Shao H, Richards AL, Chen KH, Hoeve JT, Ku GM, Hellerstein M, Nomura DK, Saijo K, Gestwicki J, Dunn AR, Krogan NJ, Swaney DL, Dillin A, Weaver VM. Adhesion-mediated mechanosignaling forces mitohormesis. Cell Metab 2021; 33:1322-1341.e13. [PMID: 34019840 PMCID: PMC8266765 DOI: 10.1016/j.cmet.2021.04.017] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 02/09/2021] [Accepted: 04/26/2021] [Indexed: 12/11/2022]
Abstract
Mitochondria control eukaryotic cell fate by producing the energy needed to support life and the signals required to execute programed cell death. The biochemical milieu is known to affect mitochondrial function and contribute to the dysfunctional mitochondrial phenotypes implicated in cancer and the morbidities of aging. However, the physical characteristics of the extracellular matrix are also altered in cancerous and aging tissues. Here, we demonstrate that cells sense the physical properties of the extracellular matrix and activate a mitochondrial stress response that adaptively tunes mitochondrial function via solute carrier family 9 member A1-dependent ion exchange and heat shock factor 1-dependent transcription. Overall, our data indicate that adhesion-mediated mechanosignaling may play an unappreciated role in the altered mitochondrial functions observed in aging and cancer.
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Affiliation(s)
- Kevin M Tharp
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Ryo Higuchi-Sanabria
- Department of Molecular & Cellular Biology, Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA 94597, USA
| | - Greg A Timblin
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Breanna Ford
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, CA 94720, USA; Novartis, Berkeley Center for Proteomics and Chemistry Technologies and Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Carlos Garzon-Coral
- Chemical Engineering Department, Stanford University, Stanford, CA 94305, USA
| | - Catherine Schneider
- Novartis, Berkeley Center for Proteomics and Chemistry Technologies and Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Jonathon M Muncie
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Connor Stashko
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Joseph R Daniele
- MD Anderson Cancer Center, South Campus Research, Houston, CA 77054, USA
| | - Andrew S Moore
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Phillip A Frankino
- Department of Molecular & Cellular Biology, Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA 94597, USA
| | - Stefan Homentcovschi
- Department of Molecular & Cellular Biology, Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA 94597, USA
| | - Sagar S Manoli
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Hao Shao
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Alicia L Richards
- Quantitative Biosciences Institute (QBI), J. David Gladstone Institutes, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Kuei-Ho Chen
- Quantitative Biosciences Institute (QBI), J. David Gladstone Institutes, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Johanna Ten Hoeve
- UCLA Metabolomics Center, Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Gregory M Ku
- Diabetes Center, Division of Endocrinology and Metabolism, Department of Medicine, UCSF, San Francisco, CA 94143, USA
| | - Marc Hellerstein
- Novartis, Berkeley Center for Proteomics and Chemistry Technologies and Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Daniel K Nomura
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, CA 94720, USA; Novartis, Berkeley Center for Proteomics and Chemistry Technologies and Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Karou Saijo
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Jason Gestwicki
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Alexander R Dunn
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Nevan J Krogan
- Quantitative Biosciences Institute (QBI), J. David Gladstone Institutes, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Danielle L Swaney
- Quantitative Biosciences Institute (QBI), J. David Gladstone Institutes, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Andrew Dillin
- Department of Molecular & Cellular Biology, Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA 94597, USA
| | - Valerie M Weaver
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Bioengineering and Therapeutic Sciences and Department of Radiation Oncology, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, and The Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA.
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12
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Interplay between H1N1 influenza a virus infection, extracellular and intracellular respiratory tract pH, and host responses in a mouse model. PLoS One 2021; 16:e0251473. [PMID: 33979408 PMCID: PMC8115840 DOI: 10.1371/journal.pone.0251473] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 04/27/2021] [Indexed: 01/01/2023] Open
Abstract
During influenza A virus (IAV) entry, the hemagglutinin (HA) protein is triggered by endosomal low pH to undergo irreversible structural changes that mediate membrane fusion. HA proteins from different isolates vary in the pH at which they become activated in endosomes or become irreversible inactivated if exposed to extracellular acid. Little is known about extracellular pH in the upper respiratory tracts of mammals, how pH may shift during IAV infection, and its impact on replication of viruses that vary in HA activation pH. Here, we inoculated DBA/2J mice intranasally with A/TN/1-560/2009 (H1N1) (activation pH 5.5) or a mutant containing the destabilizing mutation HA1-Y17H (pH 6.0). We measured the kinetics of extracellular pH during infection using an optical pH-sensitive microsensor probe placed in the naris, nasal sinus, soft palate, and trachea. We also measured intracellular pH of single-cell suspensions of live, primary lung epithelial cells with various wavelength pH-sensitive dyes localized to cell membranes, cytosol, endosomes, secretory vesicles, microtubules, and lysosomes. Infection with either virus decreased extracellular pH and increased intracellular pH. Peak host immune responses were observed at 2 days post infection (DPI) and peak pH changes at 5 DPI. Extracellular and intracellular pH returned to baseline by 7 DPI in mice infected with HA1-Y17H and was restored later in wildtype-infected. Overall, IAV infection altered respiratory tract pH, which in turn modulated replication efficiency. This suggests a virus-host pH feedback loop that may select for IAV strains containing HA proteins of optimal pH stability, which may be approximately pH 5.5 in mice but may differ in other species.
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13
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Sjøgaard-Frich LM, Prestel A, Pedersen ES, Severin M, Kristensen KK, Olsen JG, Kragelund BB, Pedersen SF. Dynamic Na +/H + exchanger 1 (NHE1) - calmodulin complexes of varying stoichiometry and structure regulate Ca 2+-dependent NHE1 activation. eLife 2021; 10:60889. [PMID: 33655882 PMCID: PMC8009664 DOI: 10.7554/elife.60889] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 03/01/2021] [Indexed: 11/25/2022] Open
Abstract
Calmodulin (CaM) engages in Ca2+-dependent interactions with numerous proteins, including a still incompletely understood physical and functional interaction with the human Na+/H+-exchanger NHE1. Using nuclear magnetic resonance (NMR) spectroscopy, isothermal titration calorimetry, and fibroblasts stably expressing wildtype and mutant NHE1, we discovered multiple accessible states of this functionally important complex existing in different NHE1:CaM stoichiometries and structures. We determined the NMR solution structure of a ternary complex in which CaM links two NHE1 cytosolic tails. In vitro, stoichiometries and affinities could be tuned by variations in NHE1:CaM ratio and calcium ([Ca2+]) and by phosphorylation of S648 in the first CaM-binding α-helix. In cells, Ca2+-CaM-induced NHE1 activity was reduced by mimicking S648 phosphorylation and by mutation of the first CaM-binding α-helix, whereas it was unaffected by inhibition of Akt, one of several kinases phosphorylating S648. Our results demonstrate a diversity of NHE1:CaM interaction modes and suggest that CaM may contribute to NHE1 dimerization and thereby augment NHE1 regulation. We propose that a similar structural diversity is of relevance to many other CaM complexes.
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Affiliation(s)
- Lise M Sjøgaard-Frich
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Andreas Prestel
- Structural Biology and NMR Laboratory, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Emilie S Pedersen
- Structural Biology and NMR Laboratory, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Marc Severin
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Kristian Kølby Kristensen
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Johan G Olsen
- Structural Biology and NMR Laboratory, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Birthe B Kragelund
- Structural Biology and NMR Laboratory, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Stine Falsig Pedersen
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
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14
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Vistrup-Parry M, Sneddon WB, Bach S, Strømgaard K, Friedman PA, Mamonova T. Multisite NHERF1 phosphorylation controls GRK6A regulation of hormone-sensitive phosphate transport. J Biol Chem 2021; 296:100473. [PMID: 33639163 PMCID: PMC8042174 DOI: 10.1016/j.jbc.2021.100473] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 02/22/2021] [Accepted: 02/23/2021] [Indexed: 12/13/2022] Open
Abstract
The type II sodium-dependent phosphate cotransporter (NPT2A) mediates renal phosphate uptake. The NPT2A is regulated by parathyroid hormone (PTH) and fibroblast growth factor 23, which requires Na+/H+ exchange regulatory factor-1 (NHERF1), a multidomain PDZ-containing phosphoprotein. Phosphocycling controls the association between NHERF1 and the NPT2A. Here, we characterize the critical involvement of G protein–coupled receptor kinase 6A (GRK6A) in mediating PTH-sensitive phosphate transport by targeted phosphorylation coupled with NHERF1 conformational rearrangement, which in turn allows phosphorylation at a secondary site. GRK6A, through its carboxy-terminal PDZ recognition motif, binds NHERF1 PDZ1 with greater affinity than PDZ2. However, the association between NHERF1 PDZ2 and GRK6A is necessary for PTH action. Ser162, a PKCα phosphorylation site in PDZ2, regulates the binding affinity between PDZ2 and GRK6A. Substitution of Ser162 with alanine (S162A) blocks the PTH action but does not disrupt the interaction between NHERF1 and the NPT2A. Replacement of Ser162 with aspartic acid (S162D) abrogates the interaction between NHERF1 and the NPT2A and concurrently PTH action. We used amber codon suppression to generate a phosphorylated Ser162(pSer162)-PDZ2 variant. KD values determined by fluorescence anisotropy indicate that incorporation of pSer162 increased the binding affinity to the carboxy terminus of GRK6A 2-fold compared with WT PDZ2. Molecular dynamics simulations predict formation of an electrostatic network between pSer162 and Asp183 of PDZ2 and Arg at position −1 of the GRK6A PDZ-binding motif. Our results suggest that PDZ2 plays a regulatory role in PTH-sensitive NPT2A-mediated phosphate transport and phosphorylation of Ser162 in PDZ2 modulates the interaction with GRK6A.
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Affiliation(s)
- Maria Vistrup-Parry
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - W Bruce Sneddon
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Sofie Bach
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Kristian Strømgaard
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Peter A Friedman
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Tatyana Mamonova
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
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15
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Mamonova T, Friedman PA. Noncanonical Sequences Involving NHERF1 Interaction with NPT2A Govern Hormone-Regulated Phosphate Transport: Binding Outside the Box. Int J Mol Sci 2021; 22:1087. [PMID: 33499384 PMCID: PMC7866199 DOI: 10.3390/ijms22031087] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/15/2021] [Accepted: 01/19/2021] [Indexed: 12/27/2022] Open
Abstract
Na+/H+ exchange factor-1 (NHERF1), a multidomain PDZ scaffolding phosphoprotein, is required for the type II sodium-dependent phosphate cotransporter (NPT2A)-mediated renal phosphate absorption. Both PDZ1 and PDZ2 domains are involved in NPT2A-dependent phosphate uptake. Though harboring identical core-binding motifs, PDZ1 and PDZ2 play entirely different roles in hormone-regulated phosphate transport. PDZ1 is required for the interaction with the C-terminal PDZ-binding sequence of NPT2A (-TRL). Remarkably, phosphocycling at Ser290 distant from PDZ1, the penultimate step for both parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF23) regulation, controls the association between NHERF1 and NPT2A. PDZ2 interacts with the C-terminal PDZ-recognition motif (-TRL) of G Protein-coupled Receptor Kinase 6A (GRK6A), and that promotes phosphorylation of Ser290. The compelling biological puzzle is how PDZ1 and PDZ2 with identical GYGF core-binding motifs specifically recognize distinct binding partners. Binding determinants distinct from the canonical PDZ-ligand interactions and located "outside the box" explain PDZ domain specificity. Phosphorylation of NHERF1 by diverse kinases and associated conformational changes in NHERF1 add more complexity to PDZ-binding diversity.
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Affiliation(s)
- Tatyana Mamonova
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA;
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16
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Koltai T. Targeting the pH Paradigm at the Bedside: A Practical Approach. Int J Mol Sci 2020; 21:E9221. [PMID: 33287221 PMCID: PMC7730959 DOI: 10.3390/ijms21239221] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 11/27/2020] [Accepted: 11/28/2020] [Indexed: 02/07/2023] Open
Abstract
The inversion of the pH gradient in malignant tumors, known as the pH paradigm, is increasingly becoming accepted by the scientific community as a hallmark of cancer. Accumulated evidence shows that this is not simply a metabolic consequence of a dysregulated behavior, but rather an essential process in the physiopathology of accelerated proliferation and invasion. From the over-simplification of increased lactate production as the cause of the paradigm, as initially proposed, basic science researchers have arrived at highly complex and far-reaching knowledge, that substantially modified that initial belief. These new developments show that the paradigm entails a different regulation of membrane transporters, electrolyte exchangers, cellular and membrane enzymes, water trafficking, specialized membrane structures, transcription factors, and metabolic changes that go far beyond fermentative glycolysis. This complex world of dysregulations is still shuttered behind the walls of experimental laboratories and has not yet reached bedside medicine. However, there are many known pharmaceuticals and nutraceuticals that are capable of targeting the pH paradigm. Most of these products are well known, have low toxicity, and are also inexpensive. They need to be repurposed, and this would entail shorter clinical studies and enormous cost savings if we compare them with the time and expense required for the development of a new molecule. Will targeting the pH paradigm solve the "cancer problem"? Absolutely not. However, reversing the pH inversion would strongly enhance standard treatments, rendering them more efficient, and in some cases permitting lower doses of toxic drugs. This article's goal is to describe how to reverse the pH gradient inversion with existing drugs and nutraceuticals that can easily be used in bedside medicine, without adding toxicity to established treatments. It also aims at increasing awareness among practicing physicians that targeting the pH paradigm would be able to improve the results of standard therapies. Some clinical cases will be presented as well, showing how the pH gradient inversion can be treated at the bedside in a simple manner with repurposed drugs.
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Affiliation(s)
- Tomas Koltai
- Centro de Diagnostico y Tratamiento de la Obra Social del Personal de la Alimentacion, Talar de Pacheco, Buenos Aires 1617, Argentina
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17
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Koch LM, Birkeland ES, Battaglioni S, Helle X, Meerang M, Hiltbrunner S, Ibáñez AJ, Peter M, Curioni-Fontecedro A, Opitz I, Dechant R. Cytosolic pH regulates proliferation and tumour growth by promoting expression of cyclin D1. Nat Metab 2020; 2:1212-1222. [PMID: 33077976 DOI: 10.1038/s42255-020-00297-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 09/10/2020] [Indexed: 01/03/2023]
Abstract
Enhanced growth and proliferation of cancer cells are accompanied by profound changes in cellular metabolism. These metabolic changes are also common under physiological conditions, and include increased glucose fermentation accompanied by elevated cytosolic pH (pHc)1,2. However, how these changes contribute to enhanced cell growth and proliferation is unclear. Here, we show that elevated pHc specifically orchestrates an E2F-dependent transcriptional programme to drive cell proliferation by promoting cyclin D1 expression. pHc-dependent transcription of cyclin D1 requires the transcription factors CREB1, ATF1 and ETS1, and the histone acetyltransferases p300 and CBP. Biochemical characterization revealed that the CREB1-p300/CBP interaction acts as a pH sensor and coincidence detector, integrating different mitotic signals to regulate cyclin D1 transcription. We also show that elevated pHc contributes to increased cyclin D1 expression in malignant pleural mesotheliomas (MPMs), and renders these cells hypersensitive to pharmacological reduction of pHc. Taken together, these data demonstrate that elevated pHc is a critical cellular signal regulating G1 progression, and provide a mechanism linking elevated pHc to oncogenic activation of cyclin D1 in MPMs, and possibly other cyclin D1~dependent tumours. Thus, an increase of pHc may represent a functionally important, early event in the aetiology of cancer that is amenable to therapeutic intervention.
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Affiliation(s)
- Lisa Maria Koch
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
- Life science Zürich, PhD program for Molecular Life Sciences, Zurich, Switzerland
| | - Eivind Salmorin Birkeland
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
- Life science Zürich, PhD program for Molecular Life Sciences, Zurich, Switzerland
| | - Stefania Battaglioni
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
- Biozentrum, University of Basel, Basel, Switzerland
| | - Xiao Helle
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Mayura Meerang
- Department of Thoracic Surgery, University Hospital Zurich, Zurich, Switzerland
| | - Stefanie Hiltbrunner
- Department of Medical Oncology and Hematology, University Hospital Zurich, Comprehensive Cancer Center Zurich, University of Zurich, Zurich, Switzerland
| | - Alfredo J Ibáñez
- Core facility for Omics Research and Applied Biotechnology (ICOBA), Pontificia Universidad Católica del Perú, Lima, Peru
| | - Matthias Peter
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Alessandra Curioni-Fontecedro
- Department of Medical Oncology and Hematology, University Hospital Zurich, Comprehensive Cancer Center Zurich, University of Zurich, Zurich, Switzerland
| | - Isabelle Opitz
- Department of Thoracic Surgery, University Hospital Zurich, Zurich, Switzerland
| | - Reinhard Dechant
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland.
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18
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Abstract
Although students initially learn of ionic buffering in basic chemistry, buffering and acid-base transport in biology often is relegated to specialized classes, discussions, or situations. That said, for physiology, nephrology, pulmonology, and anesthesiology, these basic principles often are critically important for mechanistic understanding, medical treatments, and assessing therapy effectiveness. This short introductory perspective focuses on basic chemistry and transport of buffers and acid-base equivalents, provides an outline of basic science acid-base concepts, tools used to monitor intracellular pH, model cellular responses to pH buffer changes, and the more recent development and use of genetically encoded pH-indicators. Examples of newer genetically encoded pH-indicators (pHerry and pHire) are provided, and their use for in vitro, ex vivo, and in vivo experiments are described. The continued use and development of these basic tools provide increasing opportunities for both basic and potentially clinical investigations.
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Affiliation(s)
- Michael F Romero
- Physiology and Biomedical Engineering, Nephrology and Hypertension, Mayo Clinic College of Medicine and Science, Rochester, MN.
| | - Adam J Rossano
- Physiology and Biomedical Engineering, Nephrology and Hypertension, Mayo Clinic College of Medicine and Science, Rochester, MN
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19
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Becker HM, Deitmer JW. Transport Metabolons and Acid/Base Balance in Tumor Cells. Cancers (Basel) 2020; 12:cancers12040899. [PMID: 32272695 PMCID: PMC7226098 DOI: 10.3390/cancers12040899] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 04/03/2020] [Accepted: 04/04/2020] [Indexed: 02/07/2023] Open
Abstract
Solid tumors are metabolically highly active tissues, which produce large amounts of acid. The acid/base balance in tumor cells is regulated by the concerted interplay between a variety of membrane transporters and carbonic anhydrases (CAs), which cooperate to produce an alkaline intracellular, and an acidic extracellular, environment, in which cancer cells can outcompete their adjacent host cells. Many acid/base transporters form a structural and functional complex with CAs, coined "transport metabolon". Transport metabolons with bicarbonate transporters require the binding of CA to the transporter and CA enzymatic activity. In cancer cells, these bicarbonate transport metabolons have been attributed a role in pH regulation and cell migration. Another type of transport metabolon is formed between CAs and monocarboxylate transporters, which mediate proton-coupled lactate transport across the cell membrane. In this complex, CAs function as "proton antenna" for the transporter, which mediate the rapid exchange of protons between the transporter and the surroundings. These transport metabolons do not require CA catalytic activity, and support the rapid efflux of lactate and protons from hypoxic cancer cells to allow sustained glycolytic activity and cell proliferation. Due to their prominent role in tumor acid/base regulation and metabolism, transport metabolons might be promising drug targets for new approaches in cancer therapy.
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Affiliation(s)
- Holger M. Becker
- Institute of Physiological Chemistry, University of Veterinary Medicine Hannover, D-30559 Hannover, Germany
- Correspondence:
| | - Joachim W. Deitmer
- Department of Biology, University of Kaiserslautern, D-67653 Kaiserslautern, Germany;
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20
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The Interplay of Dysregulated pH and Electrolyte Imbalance in Cancer. Cancers (Basel) 2020; 12:cancers12040898. [PMID: 32272658 PMCID: PMC7226178 DOI: 10.3390/cancers12040898] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Revised: 04/01/2020] [Accepted: 04/02/2020] [Indexed: 12/11/2022] Open
Abstract
Cancer cells and tissues have an aberrant regulation of hydrogen ion dynamics driven by a combination of poor vascular perfusion, regional hypoxia, and increased the flux of carbons through fermentative glycolysis. This leads to extracellular acidosis and intracellular alkalinization. Dysregulated pH dynamics influence cancer cell biology, from cell transformation and tumorigenesis to proliferation, local growth, invasion, and metastasis. Moreover, this dysregulated intracellular pH (pHi) drives a metabolic shift to increased aerobic glycolysis and reduced mitochondrial oxidative phosphorylation, referred to as the Warburg effect, or Warburg metabolism, which is a selective feature of cancer. This metabolic reprogramming confers a thermodynamic advantage on cancer cells and tissues by protecting them against oxidative stress, enhancing their resistance to hypoxia, and allowing a rapid conversion of nutrients into biomass to enable cell proliferation. Indeed, most cancers have increased glucose uptake and lactic acid production. Furthermore, cancer cells have very dysregulated electrolyte balances, and in the interaction of the pH dynamics with electrolyte, dynamics is less well known. In this review, we highlight the interconnected roles of dysregulated pH dynamics and electrolytes imbalance in cancer initiation, progression, adaptation, and in determining the programming and reprogramming of tumor cell metabolism.
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21
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Moldogazieva NT, Mokhosoev IM, Terentiev AA. Metabolic Heterogeneity of Cancer Cells: An Interplay between HIF-1, GLUTs, and AMPK. Cancers (Basel) 2020; 12:E862. [PMID: 32252351 PMCID: PMC7226606 DOI: 10.3390/cancers12040862] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 03/30/2020] [Accepted: 03/31/2020] [Indexed: 02/06/2023] Open
Abstract
It has been long recognized that cancer cells reprogram their metabolism under hypoxia conditions due to a shift from oxidative phosphorylation (OXPHOS) to glycolysis in order to meet elevated requirements in energy and nutrients for proliferation, migration, and survival. However, data accumulated over recent years has increasingly provided evidence that cancer cells can revert from glycolysis to OXPHOS and maintain both reprogrammed and oxidative metabolism, even in the same tumor. This phenomenon, denoted as cancer cell metabolic plasticity or hybrid metabolism, depends on a tumor micro-environment that is highly heterogeneous and influenced by an intensity of vasculature and blood flow, oxygen concentration, and nutrient and energy supply, and requires regulatory interplay between multiple oncogenes, transcription factors, growth factors, and reactive oxygen species (ROS), among others. Hypoxia-inducible factor-1 (HIF-1) and AMP-activated protein kinase (AMPK) represent key modulators of a switch between reprogrammed and oxidative metabolism. The present review focuses on cross-talks between HIF-1, glucose transporters (GLUTs), and AMPK with other regulatory proteins including oncogenes such as c-Myc, p53, and KRAS; growth factor-initiated protein kinase B (PKB)/Akt, phosphatydyl-3-kinase (PI3K), and mTOR signaling pathways; and tumor suppressors such as liver kinase B1 (LKB1) and TSC1 in controlling cancer cell metabolism. The multiple switches between metabolic pathways can underlie chemo-resistance to conventional anti-cancer therapy and should be taken into account in choosing molecular targets to discover novel anti-cancer drugs.
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Affiliation(s)
- Nurbubu T. Moldogazieva
- Laboratory of Bioinformatics, I.M. Sechenov First Moscow State Medical University (Sechenov University), 119991 Moscow, Russia
| | - Innokenty M. Mokhosoev
- Department of Biochemistry and Molecular Biology, N.I. Pirogov Russian National Research Medical University, 117997 Moscow, Russia; (I.M.M.); (A.A.T.)
| | - Alexander A. Terentiev
- Department of Biochemistry and Molecular Biology, N.I. Pirogov Russian National Research Medical University, 117997 Moscow, Russia; (I.M.M.); (A.A.T.)
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22
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Harguindey S, Alfarouk K, Polo Orozco J, Hardonnière K, Stanciu D, Fais S, Devesa J. A New and Integral Approach to the Etiopathogenesis and Treatment of Breast Cancer Based upon Its Hydrogen Ion Dynamics. Int J Mol Sci 2020; 21:E1110. [PMID: 32046158 PMCID: PMC7036897 DOI: 10.3390/ijms21031110] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 02/04/2020] [Accepted: 02/06/2020] [Indexed: 12/11/2022] Open
Abstract
Despite all efforts, the treatment of breast cancer (BC) cannot be considered to be a success story. The advances in surgery, chemotherapy and radiotherapy have not been sufficient at all. Indeed, the accumulated experience clearly indicates that new perspectives and non-main stream approaches are needed to better characterize the etiopathogenesis and treatment of this disease. This contribution deals with how the new pH-centric anticancer paradigm plays a fundamental role in reaching a more integral understanding of the etiology, pathogenesis, and treatment of this multifactorial disease. For the first time, the armamentarium available for the treatment of the different types and phases of BC is approached here from a Unitarian perspective-based upon the hydrogen ion dynamics of cancer. The wide-ranged pH-related molecular, biochemical and metabolic model is able to embrace most of the fields and subfields of breast cancer etiopathogenesis and treatment. This single and integrated approach allows advancing towards a unidirectional, concerted and synergistic program of treatment. Further efforts in this line are likely to first improve the therapeutics of each subtype of this tumor and every individual patient in every phase of the disease.
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Affiliation(s)
- Salvador Harguindey
- Institute of Clinical Biology and Metabolism, Postas 13, 01004 Vitoria, Spain;
| | - Khalid Alfarouk
- Al-Ghad International Colleges for Applied Medical Sciences, Al-Madinah Al-Munawarah, Saudi Arabia and Alfarouk Biomedical Research LLC, Tampa, FL 33617, USA;
| | - Julián Polo Orozco
- Institute of Clinical Biology and Metabolism, Postas 13, 01004 Vitoria, Spain;
| | - Kévin Hardonnière
- Université Paris-Saclay, Inserm, Inflammation, Microbiome and Immunosurveillance, 92290 Châtenay-Malabry, France;
| | - Daniel Stanciu
- Scientific Direction, MCS Foundation For Life, 5623KR Eindhoven, The Netherlands;
| | - Stefano Fais
- Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità (National Institute of Health), Viale Regina Elena, 299, 00161 Rome, Italy;
| | - Jesús Devesa
- Scientific Direction, Foltra Medical Centre, Travesía de Montouto 24, 15886 Teo, Spain;
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23
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Becker HM. Carbonic anhydrase IX and acid transport in cancer. Br J Cancer 2020; 122:157-167. [PMID: 31819195 PMCID: PMC7051959 DOI: 10.1038/s41416-019-0642-z] [Citation(s) in RCA: 94] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 08/29/2019] [Accepted: 10/22/2019] [Indexed: 02/07/2023] Open
Abstract
Alterations in tumour metabolism and acid/base regulation result in the formation of a hostile environment, which fosters tumour growth and metastasis. Acid/base homoeostasis in cancer cells is governed by the concerted interplay between carbonic anhydrases (CAs) and various transport proteins, which either mediate proton extrusion or the shuttling of acid/base equivalents, such as bicarbonate and lactate, across the cell membrane. Accumulating evidence suggests that some of these transporters interact both directly and functionally with CAIX to form a protein complex coined the 'transport metabolon'. Transport metabolons formed between bicarbonate transporters and CAIX require CA catalytic activity and have a function in cancer cell migration and invasion. Another type of transport metabolon is formed by CAIX and monocarboxylate transporters. In this complex, CAIX functions as a proton antenna for the transporter, which drives the export of lactate and protons from the cell. Since CAIX is almost exclusively expressed in cancer cells, these transport metabolons might serve as promising targets to interfere with tumour pH regulation and energy metabolism. This review provides an overview of the current state of research on the function of CAIX in tumour acid/base transport and discusses how CAIX transport metabolons could be exploited in modern cancer therapy.
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Affiliation(s)
- Holger M Becker
- Institute of Physiological Chemistry, University of Veterinary Medicine Hannover, D-30559, Hannover, Germany.
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24
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Pedersen SF, Counillon L. The SLC9A-C Mammalian Na +/H + Exchanger Family: Molecules, Mechanisms, and Physiology. Physiol Rev 2019; 99:2015-2113. [PMID: 31507243 DOI: 10.1152/physrev.00028.2018] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na+ and H+ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na+/H+ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.
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Affiliation(s)
- S F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - L Counillon
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
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25
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Harguindey S, Polo Orozco J, Alfarouk KO, Devesa J. Hydrogen Ion Dynamics of Cancer and a New Molecular, Biochemical and Metabolic Approach to the Etiopathogenesis and Treatment of Brain Malignancies. Int J Mol Sci 2019; 20:ijms20174278. [PMID: 31480530 PMCID: PMC6747469 DOI: 10.3390/ijms20174278] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 08/28/2019] [Accepted: 08/30/2019] [Indexed: 12/13/2022] Open
Abstract
The treatment of cancer has been slowly but steadily progressing during the last fifty years. Some tumors with a high mortality in the past are curable nowadays. However, there is one striking exception: glioblastoma multiforme. No real breakthrough has been hitherto achieved with this tumor with ominous prognosis and very short survival. Glioblastomas, being highly glycolytic malignancies are strongly pH-dependent and driven by the sodium hydrogen exchanger 1 (NHE1) and other proton (H+) transporters. Therefore, this is one of those pathologies where the lessons recently learnt from the new pH-centered anticancer paradigm may soon bring a promising change to treatment. This contribution will discuss how the pH-centric molecular, biochemical and metabolic perspective may introduce some urgently needed and integral novel treatments. Such a prospective therapeutic approach for malignant brain tumors is developed here, either to be used alone or in combination with more standard therapies.
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Affiliation(s)
| | | | - Khalid O Alfarouk
- Al-Ghad International Colleges for Applied Medical Sciences, Al-Madinah Al-Munawarah 42316, Saudi Arabia
- Alfarouk Biomedical Research LLC, Tampa, FL 33617, USA
| | - Jesús Devesa
- Scientific Direction, Foltra Medical Centre, 15886 Teo, Spain
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26
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Structural and Functional Changes in the Na +/H + Exchanger Isoform 1, Induced by Erk1/2 Phosphorylation. Int J Mol Sci 2019; 20:ijms20102378. [PMID: 31091671 PMCID: PMC6566726 DOI: 10.3390/ijms20102378] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 05/08/2019] [Accepted: 05/09/2019] [Indexed: 12/15/2022] Open
Abstract
The human Na+/H+ exchanger isoform 1 (NHE1) is a plasma membrane transport protein that plays an important role in pH regulation in mammalian cells. Because of the generation of protons by intermediary metabolism as well as the negative membrane potential, protons accumulate within the cytosol. Extracellular signal-regulated kinase (ERK)-mediated regulation of NHE1 is important in several human pathologies including in the myocardium in heart disease, as well as in breast cancer as a trigger for growth and metastasis. NHE1 has a N-terminal, a 500 amino acid membrane domain, and a C-terminal 315 amino acid cytosolic domain. The C-terminal domain regulates the membrane domain and its effects on transport are modified by protein binding and phosphorylation. Here, we discuss the physiological regulation of NHE1 by ERK, with an emphasis on the critical effects on structure and function. ERK binds directly to the cytosolic domain at specific binding domains. ERK also phosphorylates NHE1 directly at multiple sites, which enhance NHE1 activity with subsequent downstream physiological effects. The NHE1 cytosolic regulatory tail possesses both ordered and disordered regions, and the disordered regions are stabilized by ERK-mediated phosphorylation at a phosphorylation motif. Overall, ERK pathway mediated phosphorylation modulates the NHE1 tail, and affects the activity, structure, and function of this membrane protein.
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27
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Domblides C, Lartigue L, Faustin B. Control of the Antitumor Immune Response by Cancer Metabolism. Cells 2019; 8:cells8020104. [PMID: 30708988 PMCID: PMC6406288 DOI: 10.3390/cells8020104] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 01/25/2019] [Accepted: 01/28/2019] [Indexed: 12/12/2022] Open
Abstract
The metabolic reprogramming of tumor cells and immune escape are two major hallmarks of cancer cells. The metabolic changes that occur during tumorigenesis, enabling survival and proliferation, are described for both solid and hematological malignancies. Concurrently, tumor cells have deployed mechanisms to escape immune cell recognition and destruction. Additionally, therapeutic blocking of tumor-mediated immunosuppression has proven to have an unprecedented positive impact in clinical oncology. Increased evidence suggests that cancer metabolism not only plays a crucial role in cancer signaling for sustaining tumorigenesis and survival, but also has wider implications in the regulation of antitumor immune signaling through both the release of signaling molecules and the expression of immune membrane ligands. Here, we review these molecular events to highlight the contribution of cancer cell metabolic reprogramming on the shaping of the antitumor immune response.
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Affiliation(s)
- Charlotte Domblides
- Bordeaux University, CNRS, UMR 5164, ImmunoConcEpT, 33000 Bordeaux, France.
- Department of Medical Oncology, Hôpital Saint-André, Bordeaux University Hospital-CHU, 33000 Bordeaux, France.
| | - Lydia Lartigue
- Curematch, Inc., 6440 Lusk Bvld, San Diego, CA 92121, USA.
| | - Benjamin Faustin
- Bordeaux University, CNRS, UMR 5164, ImmunoConcEpT, 33000 Bordeaux, France.
- Cellomet, CGFB, 146 Rue léo Saignat, F-33000 Bordeaux, France.
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28
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Selective Inhibition of the Lactate Transporter MCT4 Reduces Growth of Invasive Bladder Cancer. Mol Cancer Ther 2018; 17:2746-2755. [DOI: 10.1158/1535-7163.mct-18-0107] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 07/16/2018] [Accepted: 09/20/2018] [Indexed: 11/16/2022]
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29
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Flinck M, Kramer SH, Schnipper J, Andersen AP, Pedersen SF. The acid-base transport proteins NHE1 and NBCn1 regulate cell cycle progression in human breast cancer cells. Cell Cycle 2018; 17:1056-1067. [PMID: 29895196 DOI: 10.1080/15384101.2018.1464850] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Precise acid-base homeostasis is essential for maintaining normal cell proliferation and growth. Conversely, dysregulated acid-base homeostasis, with increased acid extrusion and marked extracellular acidification, is an enabling feature of solid tumors, yet the mechanisms through which intra- and extracellular pH (pHi, pHe) impact proliferation and growth are incompletely understood. The aim of this study was to determine the impact of pH, and specifically of the Na+/H+ exchanger NHE1 and Na+, HCO3- transporter NBCn1, on cell cycle progression and its regulators in human breast cancer cells. Reduction of pHe to 6.5, a common condition in tumors, significantly delayed cell cycle progression in MCF-7 human breast cancer cells. The NHE1 protein level peaked in S phase and that of NBCn1 in G2/M. Steady state pHi changed through the cell cycle, from 7.1 in early S phase to 6.8 in G2, recovering again in M phase. This pattern, as well as net acid extrusion capacity, was dependent on NHE1 and NBCn1. Accordingly, knockdown of either NHE1 or NBCn1 reduced proliferation, prolonged cell cycle progression in a manner involving S phase prolongation and delayed G2/M transition, and altered the expression pattern and phosphorylation of cell cycle regulatory proteins. Our work demonstrates, for the first time, that both NHE1 and NBCn1 regulate cell cycle progression in breast cancer cells, and we propose that this involves cell cycle phase-specific pHi regulation by the two transporters.
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Affiliation(s)
- Mette Flinck
- a Section for Cell Biology and Physiology, Department of Biology , University of Copenhagen , Copenhagen Ø , Denmark
| | - Signe Hoejland Kramer
- a Section for Cell Biology and Physiology, Department of Biology , University of Copenhagen , Copenhagen Ø , Denmark
| | - Julie Schnipper
- a Section for Cell Biology and Physiology, Department of Biology , University of Copenhagen , Copenhagen Ø , Denmark
| | - Anne Poder Andersen
- a Section for Cell Biology and Physiology, Department of Biology , University of Copenhagen , Copenhagen Ø , Denmark
| | - Stine Falsig Pedersen
- a Section for Cell Biology and Physiology, Department of Biology , University of Copenhagen , Copenhagen Ø , Denmark
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30
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Flinck M, Kramer SH, Pedersen SF. Roles of pH in control of cell proliferation. Acta Physiol (Oxf) 2018; 223:e13068. [PMID: 29575508 DOI: 10.1111/apha.13068] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 02/17/2018] [Accepted: 03/19/2018] [Indexed: 02/06/2023]
Abstract
Precise spatiotemporal regulation of intracellular pH (pHi ) is a prerequisite for normal cell function, and changes in pHi or pericellular pH (pHe ) exert important signalling functions. It is well established that proliferation of mammalian cells is dependent on a permissive pHi in the slightly alkaline range (7.0-7.2). It is also clear that mitogen signalling in nominal absence of HCO3- is associated with an intracellular alkalinization (~0.3 pH unit above steady-state pHi ), which is secondary to activation of Na+ /H+ exchange. However, it remains controversial whether this increase in pHi is part of the mitogenic signal cascade leading to cell cycle entry and progression, and whether it is relevant under physiological conditions. Furthermore, essentially all studies of pHi in mammalian cell proliferation have focused on the mitogen-induced G0-G1 transition, and the regulation and roles of pHi during the cell cycle remain poorly understood. The aim of this review is to summarize and critically discuss the possible roles of pHi and pHe in cell cycle progression. While the focus is on the mammalian cell cycle, important insights from studies in lower eukaryotes are also discussed. We summarize current evidence of links between cell cycle progression and pHi and discuss possible pHi - and pHe sensors and signalling pathways relevant to mammalian proliferation control. The possibility that changes in pHi during cell cycle progression may be an integral part of the checkpoint control machinery is explored. Finally, we discuss the relevance of links between pH and proliferation in the context of the perturbed pH homoeostasis and acidic microenvironment of solid tumours.
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Affiliation(s)
- M. Flinck
- Section for Cell Biology and Physiology; Department of Biology; Faculty of Science; University of Copenhagen; Copenhagen Denmark
| | - S. H. Kramer
- Section for Cell Biology and Physiology; Department of Biology; Faculty of Science; University of Copenhagen; Copenhagen Denmark
| | - S. F. Pedersen
- Section for Cell Biology and Physiology; Department of Biology; Faculty of Science; University of Copenhagen; Copenhagen Denmark
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31
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Parks SK, Cormerais Y, Durivault J, Pouyssegur J. Genetic disruption of the pHi-regulating proteins Na+/H+ exchanger 1 (SLC9A1) and carbonic anhydrase 9 severely reduces growth of colon cancer cells. Oncotarget 2018; 8:10225-10237. [PMID: 28055960 PMCID: PMC5354654 DOI: 10.18632/oncotarget.14379] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 11/30/2016] [Indexed: 02/06/2023] Open
Abstract
Hypoxia and extracellular acidosis are pathophysiological hallmarks of aggressive solid tumors. Regulation of intracellular pH (pHi) is essential for the maintenance of tumor cell metabolism and proliferation in this microenvironment and key proteins involved in pHi regulation are of interest for therapeutic development. Carbonic anhydrase 9 (CA9) is one of the most robustly regulated proteins by the hypoxia inducible factor (HIF) and contributes to pHi regulation. Here, we have investigated for the first time, the role of CA9 via complete genomic knockout (ko) and compared its impact on tumor cell physiology with the essential pHi regulator Na+/H+ exchanger 1 (NHE1). Initially, we established NHE1-ko LS174 cells with inducible CA9 knockdown. While increased sensitivity to acidosis for cell survival in 2-dimensions was not observed, clonogenic proliferation and 3-dimensional spheroid growth in particular were greatly reduced. To avoid potential confounding variables with use of tetracycline-inducible CA9 knockdown, we established CA9-ko and NHE1/CA9-dko cells. NHE1-ko abolished recovery from NH4Cl pre-pulse cellular acid loading while both NHE1 and CA9 knockout reduced resting pHi. NHE1-ko significantly reduced tumor cell proliferation both in normoxia and hypoxia while CA9-ko dramatically reduced growth in hypoxic conditions. Tumor xenografts revealed substantial reductions in tumor growth for both NHE1-ko and CA9-ko. A notable induction of CA12 occurred in NHE1/CA9-dko tumors indicating a potential means to compensate for loss of pH regulating proteins to maintain growth. Overall, these genomic knockout results strengthen the pursuit of targeting tumor cell pH regulation as an effective anti-cancer strategy.
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Affiliation(s)
- Scott K Parks
- Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco
| | - Yann Cormerais
- Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco
| | - Jerome Durivault
- Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco
| | - Jacques Pouyssegur
- Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco.,Institute for Research on Cancer & Aging (IRCAN), CNRS, INSERM, Centre A. Lacassagne, University of Nice-Sophia Antipolis, Nice, France
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32
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Babich V, Henry MK, Di Sole F. Application of Electrophysiology Measurement to Study the Activity of Electro-Neutral Transporters. J Vis Exp 2018. [PMID: 29443070 DOI: 10.3791/56630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The transport of ions through cell membranes ensures the fine control of ion content within and outside the cell that is indispensable for cell survival. These transport mechanisms are mediated by the activities of specialized transporter proteins. Specifically,pH dynamics are finely controlled by plasma membrane proton (H+) extrusion systems, such as the Na+/H+ exchanger (NHE) protein family. Despite extensive efforts to study the mechanisms underlying NHE regulation, our current understanding of the biophysical and molecular properties of the NHE family is inadequate because of the limited availability of methods to effectively measure NHE activity. In this manuscript, we used H+-selective electrodes during whole-cell patch clamping recording to measure NHE-induced H+ flux. We proposed this approach to overcome some limitations of typically used methods to measure NHE activity, such as radioactive uptake and fluorescent membrane permeants. Measurement of NHE activity using the described method enables high sensitivity and time resolution and more efficient control of intracellular H+ concentrations. H+-selective electrodes are based on the fact that transporter activity creates an ion gradient in close proximity to the cell membrane. An H+-selective electrode moving up to and away from the cell membrane in a repetitive, oscillatory fashion records a voltage difference that is dependent on H+ flux. While H+-selective electrodes are used to detect H+ flux moving out of the cell, the patch clamp method in the whole-cell configuration is used to control the intracellular ion composition. Moreover, application of the giant patch clamp technique allows modification of the intracellular composition of not only ions but also lipids. The transporter activity of NHE isoform 3 (NHE3) was measured using this technical approach to study the molecular basis of NHE3 regulation by phosphoinositides.
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Affiliation(s)
- Victor Babich
- Physiology and Pharmacology Department, Des Moines University; School of Liberal Arts and Sciences, Mercy College of Health Sciences
| | - Matthew K Henry
- Physiology and Pharmacology Department, Des Moines University
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33
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Abstract
The high metabolic demand of cancer cells leads to an accumulation of H+ ions in the tumour microenvironment. The disorganized tumour vasculature prevents an efficient wash-out of H+ ions released into the extracellular medium but also favours the development of tumour hypoxic regions associated with a shift towards glycolytic metabolism. Under hypoxia, the final balance of glycolysis, including breakdown of generated ATP, is the production of lactate and a stoichiometric amount of H+ ions. Another major source of H+ ions results from hydration of CO2 produced in the more oxidative tumour areas. All of these events occur at high rates in tumours to fulfil bioenergetic and biosynthetic needs. This Review summarizes the current understanding of how H+-generating metabolic processes segregate within tumours according to the distance from blood vessels and inversely how ambient acidosis influences tumour metabolism, reducing glycolysis while promoting mitochondrial activity. The Review also presents novel insights supporting the participation of acidosis in cancer progression via stimulation of autophagy and immunosuppression. Finally, recent advances in the different therapeutic modalities aiming to either block pH-regulatory systems or exploit acidosis will be discussed.
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Affiliation(s)
- Cyril Corbet
- Pole of Pharmacology and Therapeutics (FATH), Institut de Recherche Expérimentale et Clinique (IREC), Université Catholique de Louvain, 53 Avenue Mounier B1.53.09, B-1200 Brussels, Belgium
| | - Olivier Feron
- Pole of Pharmacology and Therapeutics (FATH), Institut de Recherche Expérimentale et Clinique (IREC), Université Catholique de Louvain, 53 Avenue Mounier B1.53.09, B-1200 Brussels, Belgium
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34
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Yuan Z, Du Y, He Y. Hyperbranched polyamine assisted synthesis of dual-luminescent gold composite with pH responsive character. Methods Appl Fluoresc 2017; 5:014011. [DOI: 10.1088/2050-6120/aa625d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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35
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Sikka A, M E Barnes E, Keun HC. The role of biophysics and engineering in investigating tumour pH and its regulation. CONVERGENT SCIENCE PHYSICAL ONCOLOGY 2017. [DOI: 10.1088/2057-1739/aa5cd9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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36
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Parks SK, Cormerais Y, Pouysségur J. Hypoxia and cellular metabolism in tumour pathophysiology. J Physiol 2017; 595:2439-2450. [PMID: 28074546 DOI: 10.1113/jp273309] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 12/01/2016] [Indexed: 12/17/2022] Open
Abstract
Cancer cells are optimised for growth and survival via an ability to outcompete normal cells in their microenvironment. Many of these advantageous cellular adaptations are promoted by the pathophysiological hypoxia that arises in solid tumours due to incomplete vascularisation. Tumour cells are thus faced with the challenge of an increased need for nutrients to support the drive for proliferation in the face of a diminished extracellular supply. Among the many modifications occurring in tumour cells, hypoxia inducible factors (HIFs) act as essential drivers of key pro-survival pathways via the promotion of numerous membrane and cytosolic proteins. Here we focus our attention on two areas: the role of amino acid uptake and the handling of metabolic acid (CO2 /H+ ) production. We provide evidence for a number of hypoxia-induced proteins that promote cellular anabolism and regulation of metabolic acid-base levels in tumour cells including amino-acid transporters (LAT1), monocarboxylate transporters, and acid-base regulating carbonic anhydrases (CAs) and bicarbonate transporters (NBCs). Emphasis is placed on current work manipulating multiple CA isoforms and NBCs, which is at an interesting crossroads of gas physiology as they are regulated by hypoxia to contribute to the cellular handling of CO2 and pHi regulation. Our research combined with others indicates that targeting of HIF-regulated membrane proteins in tumour cells will provide promising future anti-cancer therapeutic approaches and we suggest strategies that could be potentially used to enhance these tactics.
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Affiliation(s)
- Scott K Parks
- Medical Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine 1er, MC-98000, Monaco, Principality of Monaco
| | - Yann Cormerais
- Medical Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine 1er, MC-98000, Monaco, Principality of Monaco
| | - Jacques Pouysségur
- Medical Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine 1er, MC-98000, Monaco, Principality of Monaco.,Institute for Research on Cancer and Aging (IRCAN), CNRS, INSERM, Centre A. Lacassagne, University of Nice-Sophia Antipolis, Nice, France
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37
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White KA, Grillo-Hill BK, Barber DL. Cancer cell behaviors mediated by dysregulated pH dynamics at a glance. J Cell Sci 2017; 130:663-669. [PMID: 28202602 PMCID: PMC5339414 DOI: 10.1242/jcs.195297] [Citation(s) in RCA: 225] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Dysregulated pH is a common characteristic of cancer cells, as they have an increased intracellular pH (pHi) and a decreased extracellular pH (pHe) compared with normal cells. Recent work has expanded our knowledge of how dysregulated pH dynamics influences cancer cell behaviors, including proliferation, metastasis, metabolic adaptation and tumorigenesis. Emerging data suggest that the dysregulated pH of cancers enables these specific cell behaviors by altering the structure and function of selective pH-sensitive proteins, termed pH sensors. Recent findings also show that, by blocking pHi increases, cancer cell behaviors can be attenuated. This suggests ion transporter inhibition as an effective therapeutic approach, either singly or in combination with targeted therapies. In this Cell Science at a Glance article and accompanying poster, we highlight the interconnected roles of dysregulated pH dynamics in cancer initiation, progression and adaptation.
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Affiliation(s)
- Katharine A White
- Department of Cell and Tissue Biology, University of California San Francisco, San Francisco, CA 94143, USA
| | - Bree K Grillo-Hill
- Department of Biological Sciences, San José State University, San José, CA 95192, USA
| | - Diane L Barber
- Department of Cell and Tissue Biology, University of California San Francisco, San Francisco, CA 94143, USA
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38
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Targeting pH regulating proteins for cancer therapy-Progress and limitations. Semin Cancer Biol 2017; 43:66-73. [PMID: 28137473 DOI: 10.1016/j.semcancer.2017.01.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 01/24/2017] [Indexed: 12/21/2022]
Abstract
Tumour acidity induced by metabolic alterations and incomplete vascularisation sets cancer cells apart from normal cellular physiology. This distinguishing tumour characteristic has been an area of intense study, as cellular pH (pHi) disturbances disrupt protein function and therefore multiple cellular processes. Tumour cells effectively utilise pHi regulating machinery present in normal cells with enhancements provided by additional oncogenic or hypoxia induced protein modifications. This overall improvement of pH regulation enables maintenance of an alkaline pHi in the continued presence of external acidification (pHe). Considerable experimentation has revealed targets that successfully disrupt tumour pHi regulation in efforts to develop novel means to weaken or kill tumour cells. However, redundancy in these pH-regulating proteins, which include Na+/H+ exchangers (NHEs), carbonic anhydrases (CAs), Na+/HCO3- co-transporters (NBCs) and monocarboxylate transporters (MCTs) has prevented effective disruption of tumour pHi when individual protein targeting is performed. Here we synthesise recent advances in understanding both normoxic and hypoxic pH regulating mechanisms in tumour cells with an ultimate focus on the disruption of tumour growth, survival and metastasis. Interactions between tumour acidity and other cell types are also proving to be important in understanding therapeutic applications such as immune therapy. Promising therapeutic developments regarding pH manipulation along with current limitations are highlighted to provide a framework for future research directives.
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Abstract
The Na+/H+ exchanger NHE1 is at the crossroads of a large diversity of signaling pathways, whose activation modifies the cooperative response of the transporter to intracellular H+ ions. Here we show how the activation of the Na+/H+ exchanger NHE1 by the cleaved ligand of CD95 can be measured. We demonstrate two different methods designed to set intracellular pH at precise values. Then we show how these can be coupled to fast kinetics of lithium transport, which will enable to measure the NHE1 activity like for an enzyme, because they will yield rates of transport.
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Affiliation(s)
- Auréa Cophignon
- LP2M UMR 7370 Faculté de Médecine, Université Nice-Sophia Antipolis, 28 Avenue de Valombrose, 06107, Nice, France
- Laboratories of Excellence, Ion Channels Sciences and Therapeutics, Université Lille, Villeneuve d'Ascq, France
| | - Mallorie Poët
- LP2M UMR 7370 Faculté de Médecine, Université Nice-Sophia Antipolis, 28 Avenue de Valombrose, 06107, Nice, France
- Laboratories of Excellence, Ion Channels Sciences and Therapeutics, Université Lille, Villeneuve d'Ascq, France
| | - Michael Monet
- LP2M UMR 7370 Faculté de Médecine, Université Nice-Sophia Antipolis, 28 Avenue de Valombrose, 06107, Nice, France
- Laboratories of Excellence, Ion Channels Sciences and Therapeutics, Université Lille, Villeneuve d'Ascq, France
- LPCM EA4667, Université de Picardie Jules Verne, 33 rue st Leu, 80000, Amiens, France
| | - Michel Tauc
- LP2M UMR 7370 Faculté de Médecine, Université Nice-Sophia Antipolis, 28 Avenue de Valombrose, 06107, Nice, France
- Laboratories of Excellence, Ion Channels Sciences and Therapeutics, Université Lille, Villeneuve d'Ascq, France
| | - Laurent Counillon
- LP2M UMR 7370 Faculté de Médecine, Université Nice-Sophia Antipolis, 28 Avenue de Valombrose, 06107, Nice, France.
- Laboratories of Excellence, Ion Channels Sciences and Therapeutics, Université Lille, Villeneuve d'Ascq, France.
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Stock C, Pedersen SF. Roles of pH and the Na +/H + exchanger NHE1 in cancer: From cell biology and animal models to an emerging translational perspective? Semin Cancer Biol 2016; 43:5-16. [PMID: 28007556 DOI: 10.1016/j.semcancer.2016.12.001] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 12/10/2016] [Indexed: 01/30/2023]
Abstract
Acidosis is characteristic of the solid tumor microenvironment. Tumor cells, because they are highly proliferative and anabolic, have greatly elevated metabolic acid production. To sustain a normal cytosolic pH homeostasis they therefore need to either extrude excess protons or to neutralize them by importing HCO3-, in both cases causing extracellular acidification in the poorly perfused tissue microenvironment. The Na+/H+ exchanger isoform 1 (NHE1) is a ubiquitously expressed acid-extruding membrane transport protein, and upregulation of its expression and/or activity is commonly correlated with tumor malignancy. The present review discusses current evidence on how altered pH homeostasis, and in particular NHE1, contributes to tumor cell motility, invasion, proliferation, and growth and facilitates evasion of chemotherapeutic cell death. We summarize data from in vitro studies, 2D-, 3D- and organotypic cell culture, animal models and human tissue, which collectively point to pH-regulation in general, and NHE1 in particular, as potential targets in combination chemotherapy. Finally, we discuss the possible pitfalls, side effects and cellular escape mechanisms that need to be considered in the process of translating the plethora of basic research data into a clinical setting.
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Affiliation(s)
- Christian Stock
- Department of Gastroenterology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
| | - Stine Falsig Pedersen
- Department of Biology, Section for Cell Biology and Physiology, University of Copenhagen, Universitetsparken 13, 2100 Copenhagen, Denmark.
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The cleaved FAS ligand activates the Na(+)/H(+) exchanger NHE1 through Akt/ROCK1 to stimulate cell motility. Sci Rep 2016; 6:28008. [PMID: 27302366 PMCID: PMC4908414 DOI: 10.1038/srep28008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 05/17/2016] [Indexed: 12/20/2022] Open
Abstract
Transmembrane CD95L (Fas ligand) can be cleaved to release a promigratory soluble ligand, cl-CD95L, which can contribute to chronic inflammation and cancer cell dissemination. The motility signaling pathway elicited by cl-CD95L remains poorly defined. Here, we show that in the presence of cl-CD95L, CD95 activates the Akt and RhoA signaling pathways, which together orchestrate an allosteric activation of the Na+/H+ exchanger NHE1. Pharmacologic inhibition of Akt or ROCK1 independently blocks the cl-CD95L-induced migration. Confirming these pharmacologic data, disruption of the Akt and ROCK1 phosphorylation sites on NHE1 decreases cell migration in cells exposed to cl-CD95L. Together, these findings demonstrate that NHE1 is a novel molecular actor in the CD95 signaling pathway that drives the cl-CD95L-induced cell migration through both the Akt and RhoA signaling pathways.
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Modulating intracellular acidification by regulating the incubation time of proton caged compounds. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2016; 45:565-71. [DOI: 10.1007/s00249-016-1122-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 02/05/2016] [Accepted: 02/20/2016] [Indexed: 10/22/2022]
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Hirose Y, Yamaguchi M, Kawabata S, Murakami M, Nakashima M, Gotoh M, Yamamoto T. Effects of Extracellular pH on Dental Pulp Cells In Vitro. J Endod 2016; 42:735-41. [PMID: 26951958 DOI: 10.1016/j.joen.2016.01.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 01/15/2016] [Accepted: 01/27/2016] [Indexed: 01/09/2023]
Abstract
INTRODUCTION The proliferation and migration of dental pulp stem cells (DPSCs), a population comprised of dental pulp cells (DPCs), are important processes for pulp tissue repair. Dental pulp is exposed to changes in extracellular pH under various conditions, such as acidosis and exposure to caries-associated bacteria or a pulp capping agent. The objective of this study was to investigate the effects of extracellular pH on DPC proliferation and migration in vitro. METHODS To evaluate the proliferation potency of DPCs in various extracellular pH conditions, 2 × 10(4) cells were seeded into 35-mm dishes. The following day, we changed to NaHCO3-free medium, which was adjusted to different extracellular pH levels. RESULTS After 120 hours, DPCs cultured in media from a pH of 3.5 to 5.5 showed cell death, those cultured in conditions from a pH of 6.5 to 7.5 showed growth arrest or cell death, and those grown at a pH of 9.5 showed mild proliferation. The migratory activity of living DPCs was not affected by extracellular pH. For histologic analysis, human teeth possessing a small abscess in the coronal pulp chamber were sliced for histologic analysis. Proliferating cell nuclear antigen (PCNA) immunolocalization was used as an index of cell proliferation for the sections and cultured cells. Acidic extracellular pH conditions resulted in reduced numbers of PCNA-positive DPCs in the dishes. As for pulp tissue affected by a small abscess, a PCNA-negative pulp cell layer was observed in close proximity to the infectious lesion. CONCLUSIONS Together, these results suggest that an acidic extracellular pH condition is associated with DPC growth arrest or cell death.
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Affiliation(s)
- Yujiro Hirose
- Department of Urology, Nagoya University Graduate School of Medicine, Nagoya, Japan; Department of Dental Regenerative Medicine, Center of Advanced Medicine for Dental and Oral Diseases, National Center for Geriatrics and Gerontology, Obu, Japan; Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita, Japan
| | - Masaya Yamaguchi
- Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita, Japan
| | - Shigetada Kawabata
- Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, Suita, Japan
| | - Masashi Murakami
- Department of Dental Regenerative Medicine, Center of Advanced Medicine for Dental and Oral Diseases, National Center for Geriatrics and Gerontology, Obu, Japan
| | - Misako Nakashima
- Department of Dental Regenerative Medicine, Center of Advanced Medicine for Dental and Oral Diseases, National Center for Geriatrics and Gerontology, Obu, Japan
| | - Momokazu Gotoh
- Department of Urology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Tokunori Yamamoto
- Department of Urology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
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Exogenous control over intracellular acidification: Enhancement via proton caged compounds coupled to gold nanoparticles. Biochim Biophys Acta Gen Subj 2015; 1850:2304-7. [DOI: 10.1016/j.bbagen.2015.07.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 07/27/2015] [Accepted: 07/29/2015] [Indexed: 12/20/2022]
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Zheng G, Peng C, Jia X, Gu Y, Zhang Z, Deng Y, Wang C, Li N, Yin J, Liu X, Lu M, Tang H, He Z. ZEB1 transcriptionally regulated carbonic anhydrase 9 mediates the chemoresistance of tongue cancer via maintaining intracellular pH. Mol Cancer 2015; 14:84. [PMID: 25890268 PMCID: PMC4404088 DOI: 10.1186/s12943-015-0357-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 04/02/2015] [Indexed: 12/29/2022] Open
Abstract
Background Chemoresistance is a major obstacle in successfully treating cancers, and the mechanisms responsible for drug resistance are still far from understood. Carbonic anhydrase 9 (CA9) has been shown to be upregulated in the drug-resistant tongue cancer cell line Tca8113/PYM and to be associated with drug resistance. However, the mechanisms regulating CA9 expression and its role in drug resistance remain unclear. Methods Bioinformatic and experimental analysis involving ChIP and luciferase reporter assays were used to validate Zinc finger E-box-binding homeobox 1 (ZEB1) as a transcriptional regulator of CA9. Gene expression and protein levels were evaluated by quantitative RT-PCR and western blotting, respectively. Sensitivity to chemotherapy was examined using the MTS assay and Hoechst staining and analysis caspase-3 activity to evaluate changes in apoptosis. Intracellular pH (pHi) was measured using fluorescent pH-indicator BCECF-AM. Protein expression in patient tissue samples was examined by immunohistochemistry and survival of tongue cancer patients from which these samples were derived was also analyzed. Results ZEB1 bound to the promoter of CA9 to positively regulate CA9 expression in tongue cancer cells. Knockdown of CA9 using short interfering RNA (siRNA) abolished the chemoresistance resulting from ZEB1 overexpression in Tca8113 and SCC-25 cells, and CA9 overexpression attenuated chemosensitivity induced by ZEB1 knockdown in Tca8113/PYM cells. CA9 knockdown also prevented maintenance of pHi mediated by overexpression of ZEB1 in Tca8113 and SCC-25 cells following chemotherapy, associated with increased apoptosis and caspase-3 activation. Conversely, ectopic expression of CA9 suppressed decrease in pHi mediated by ZEB1 knockdown in Tca8113/PYM cells following chemotherapy, accompanied by decreased apoptosis and caspase-3 activation. Importantly, a positive correlation was observed between ZEB1 and CA9 protein expression in tongue cancer tissues, and expression of these proteins associated with a poor prognosis for patients. Conclusion Our finding that tumor cells regulate pHi in response to chemotherapy provides new insights into mechanisms of drug resistance during cancer treatment. Identification of the ZEB1–CA9 signaling axis as a biomarker of poor prognosis in tongue cancer will be valuable in future development of therapeutic strategies aimed at improving treatment efficacy, especially in terms of drug resistance associated with this disease.
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Affiliation(s)
- Guopei Zheng
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Cong Peng
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Xiaoting Jia
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Yixue Gu
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Zhijie Zhang
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Yingen Deng
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Chengkun Wang
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Nan Li
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Jiang Yin
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Xiaorong Liu
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Minying Lu
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
| | - Hailin Tang
- Department of Breast Oncology, Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, East Dongfeng Road 651#, Guangzhou, 510060, Guangdong, China.
| | - Zhimin He
- Cancer Hospital and Cancer Research Institute of Guangzhou Medical University, Hengzhigang Road 78#, Guangzhou, 510095, Guangdong, China.
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Milosavljevic N, Poët M, Monet M, Birgy-Barelli E, Léna I, Counillon L. Functional characterization of Na+/H+ exchangers of intracellular compartments using proton-killing selection to express them at the plasma membrane. J Vis Exp 2015:52453. [PMID: 25867523 PMCID: PMC4401382 DOI: 10.3791/52453] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Endosomal acidification is critical for a wide range of processes, such as protein recycling and degradation, receptor desensitization, and neurotransmitter loading in synaptic vesicles. This acidification is described to be mediated by proton ATPases, coupled to ClC chloride transporters. Highly-conserved electroneutral protons transporters, the Na+/H+ exchangers (NHE) 6, 7 and 9 are also expressed in these compartments. Mutations in their genes have been linked with human cognitive and neurodegenerative diseases. Paradoxically, their roles remain elusive, as their intracellular localization has prevented detailed functional characterization. This manuscript shows a method to solve this problem. This consists of the selection of mutant cell lines, capable of surviving acute cytosolic acidification by retaining intracellular NHEs at the plasma membrane. It then depicts two complementary protocols to measure the ion selectivity and activity of these exchangers: (i) one based on intracellular pH measurements using fluorescence video microscopy, and (ii) one based on the fast kinetics of lithium uptake. Such protocols can be extrapolated to measure other non-electrogenic transporters. Furthermore, the selection procedure presented here generates cells with an intracellular retention defective phenotype. Therefore these cells will also express other vesicular membrane proteins at the plasma membrane. The experimental strategy depicted here may therefore constitute a potentially powerful tool to study other intracellular proteins that will be then expressed at the plasma membrane together with the vesicular Na+/H+ exchangers used for the selection.
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Affiliation(s)
- Nina Milosavljevic
- Université Nice-Sophia Antipolis, Laboratoire de Physiomédecine Moléculaire, CNRS UMR7370, and Laboratories of Excellence Ion Channel Science and Therapeutics
| | - Mallorie Poët
- Université Nice-Sophia Antipolis, Laboratoire de Physiomédecine Moléculaire, CNRS UMR7370, and Laboratories of Excellence Ion Channel Science and Therapeutics
| | - Michael Monet
- Université Nice-Sophia Antipolis, Laboratoire de Physiomédecine Moléculaire, CNRS UMR7370, and Laboratories of Excellence Ion Channel Science and Therapeutics
| | - Eléonore Birgy-Barelli
- Université Nice-Sophia Antipolis, Laboratoire de Physiomédecine Moléculaire, CNRS UMR7370, and Laboratories of Excellence Ion Channel Science and Therapeutics
| | - Isabelle Léna
- Université Nice-Sophia Antipolis, Laboratoire de Physiomédecine Moléculaire, CNRS UMR7370, and Laboratories of Excellence Ion Channel Science and Therapeutics
| | - Laurent Counillon
- Université Nice-Sophia Antipolis, Laboratoire de Physiomédecine Moléculaire, CNRS UMR7370, and Laboratories of Excellence Ion Channel Science and Therapeutics;
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Grillo-Hill BK, Choi C, Jimenez-Vidal M, Barber DL. Increased H⁺ efflux is sufficient to induce dysplasia and necessary for viability with oncogene expression. eLife 2015; 4. [PMID: 25793441 PMCID: PMC4392478 DOI: 10.7554/elife.03270] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Accepted: 03/17/2015] [Indexed: 01/02/2023] Open
Abstract
Intracellular pH (pHi) dynamics is increasingly recognized as an important regulator of a range of normal and pathological cell behaviors. Notably, increased pHi is now acknowledged as a conserved characteristic of cancers and in cell models is confirmed to increase proliferation and migration as well as limit apoptosis. However, the significance of increased pHi for cancer in vivo remains unresolved. Using Drosophila melanogaster, we show that increased pHi is sufficient to induce dysplasia in the absence of other transforming cues and potentiates growth and invasion with oncogenic Ras. Using a genetically encoded biosensor we also confirm increased pHi in situ. Moreover, in Drosophila models and clonal human mammary cells we show that limiting H(+) efflux with oncogenic Raf or Ras induces acidosis and synthetic lethality. Further, we show lethality in invasive primary tumor cell lines with inhibiting H(+) efflux. Synthetic lethality with reduced H(+) efflux and activated oncogene expression could be exploited therapeutically to restrain cancer progression while limiting off-target effects.
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Affiliation(s)
- Bree K Grillo-Hill
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, United States
| | - Changhoon Choi
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, United States
| | - Maite Jimenez-Vidal
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, United States
| | - Diane L Barber
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, United States
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Sabbatella G, Antonaroli S, Diociauti M, Nucara A, Carbone M. Synthesis of proton caged disulphide compounds for gold nanoparticle functionalization. NEW J CHEM 2015. [DOI: 10.1039/c4nj01362j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Novel proton caged compounds have been synthesized, with a sulphur bridge to bind gold nanoparticles and release protons upon UV irradiation.
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Affiliation(s)
- Gianfranco Sabbatella
- Dept. of Chemistry
- University of Rome La Sapienza
- Rome
- Italy
- Dept. of Chemical Science and Technologies
| | - Simonetta Antonaroli
- Dept. of Chemical Science and Technologies
- University of Rome Tor Vergata
- Rome
- Italy
| | - Marco Diociauti
- Dept. of Technology and Health
- Istituto Superiore di Sanitá
- Rome
- Italy
| | | | - Marilena Carbone
- Dept. of Chemical Science and Technologies
- University of Rome Tor Vergata
- Rome
- Italy
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Cappellozza BI, Cooke RF, Reis MM, Marques RS, Guarnieri Filho TA, Perry GA, Jump DB, Lytle KA, Bohnert DW. Effects of protein supplementation frequency on physiological responses associated with reproduction in beef cows. J Anim Sci 2015; 93:386-94. [PMID: 25412746 DOI: 10.2527/jas.2014-8432] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The objective of this experiment was to determine if frequency of protein supplementation impacts physiological responses associated with reproduction in beef cows. Fourteen nonpregnant, nonlactating beef cows were ranked by age and BW and allocated to 3 groups. Groups were assigned to a 3 × 3 Latin square design, containing 3 periods of 21 d and the following treatments: 1) soybean meal supplementation daily (D), 2) soybean meal supplementation 3 times/week (3WK), and 3) soybean meal supplementation once/week (1WK). Within each period, cows were assigned to an estrus synchronization protocol: 100 μg of GnRH + controlled internal drug release device (CIDR) containing 1.38 g of progesterone (P4) on d 1, 25 mg of PGF2α on d 8, and CIDR removal + 100 μg of GnRH on d 11. Grass-seed straw was offered for ad libitum consumption. Soybean meal was individually supplemented at a daily rate of 1 kg/cow (as-fed basis). Moreover, 3WK was supplemented on d 0, 2, 4, 7, 9, 11, 14, 16, and 18 whereas 1WK was supplemented on d 4, 11, and 18. Blood samples were collected from 0 (before) to 72 h after supplementation on d 11 and 18 and analyzed for plasma urea-N (PUN). Samples collected from 0 to 12 h were also analyzed for plasma glucose, insulin, and P4 (d 18 only). Uterine flushing fluid was collected concurrently with blood sampling at 28 h for pH evaluation. Liver biopsies were performed concurrently with blood sampling at 0, 4, and 28 h and analyzed for mRNA expression of carbamoyl phosphate synthetase I (CPS-I; h 28) and CYP2C19 and CYP3A4 (h 0 and 4 on d 18). Plasma urea-N concentrations were greater (P < 0.01) for 1WK vs. 3WK from 20 to 72 h and greater (P < 0.01) for 1WK vs. D from 16 to 48 h and at 72 h after supplementation (treatment × hour interaction, P < 0.01). Moreover, PUN concentrations peaked at 28 h after supplementation for 3WK and 1WK (P < 0.01) and were greater (P < 0.01) at this time for 1WK vs. 3WK and D and for 3WK vs. D. Expression of CPS-I was greater (P < 0.01) for 1WK vs. D and 3WK. Uterine flushing pH tended (P ≤ 0.10) to be greater for 1WK vs. 3WK and D. No treatment effects were detected (P ≥ 0.15) on expression of CYP2C19 and CYP3A4, plasma glucose, and P4 concentrations, whereas plasma insulin concentrations were greater (P ≤ 0.03) in D and 3WK vs. 1WK. Hence, decreasing frequency of protein supplementation did not reduce uterine flushing pH or plasma P4 concentrations, which are known to impact reproduction in beef cows.
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Affiliation(s)
- B I Cappellozza
- Oregon State University, Eastern Oregon Agricultural Research Center, Burns 97720
| | - R F Cooke
- Oregon State University, Eastern Oregon Agricultural Research Center, Burns 97720
| | - M M Reis
- Oregon State University, Eastern Oregon Agricultural Research Center, Burns 97720
| | - R S Marques
- Oregon State University, Eastern Oregon Agricultural Research Center, Burns 97720
| | - T A Guarnieri Filho
- Oregon State University, Eastern Oregon Agricultural Research Center, Burns 97720 Faculdade de Medicina Veterinária e Zootecnia, UNESP - Univ. Estadual Paulista, Programa de Pós-Graduação em Zootecnia, Botucatu, SP, Brazil, 18618-970
| | - G A Perry
- Department of Animal Science, South Dakota State University, Brookings 57007
| | - D B Jump
- Nutrition Program, School of Biological and Population Health Sciences, Linus Pauling Institute, Oregon State University, Corvallis 97331
| | - K A Lytle
- Nutrition Program, School of Biological and Population Health Sciences, Linus Pauling Institute, Oregon State University, Corvallis 97331
| | - D W Bohnert
- Oregon State University, Eastern Oregon Agricultural Research Center, Burns 97720
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Frontzek F, Nitzlaff S, Horstmann M, Schwab A, Stock C. Functional interdependence of NHE1 and merlin in human melanoma cells. Biochem Cell Biol 2014; 92:530-40. [PMID: 25275700 DOI: 10.1139/bcb-2014-0041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Upregulation of the Na(+)/H(+) exchanger isoform 1 (NHE1) has been correlated with tumor malignancy. In contrast, moesin-radixin-ezrin-like protein (merlin) is a tumor suppressor that protects from cancerogenesis. Merlin is highly related to the members of the ezrin, radixin, and moesin (ERM) protein family that are directly attached to and functionally linked with NHE1. In addition, merlin inhibits the MAPK cascade and the Rho-GTPases known to activate NHE1 activity. The present study investigates whether NHE1 expression and activity affect merlin or, conversely, whether merlin has an impact on NHE1 in human melanoma (MV3) cells. Indeed, features of merlin-deficient MV3 cells point to a functional link: merlin-deficient cells showed a decreased NHE1 expression and, paradoxically, an increase in NHE1 activity as measured upon cytosolic acidification (NH4Cl prepulse method). Loss of merlin also led to an elevated cell motility that could be further increased by NHE1 overexpression, whereas NHE1 overexpression alone had no effect on migration. In contrast, neither NHE1 expression nor its activity had an impact on merlin expression. These results suggest a novel tumor suppressor function of merlin in melanoma cells: the inhibition of the proto-oncogenic NHE1 activity, possibly including its downstream signaling pathways.
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Affiliation(s)
- Fabian Frontzek
- Institute of Physiology II, University of Münster, Robert-Koch-Str. 27b, D-48149 Münster, Germany
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