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Abstract
The PMCA is an ATP-driven Ca2+ pump critical for the maintenance of low cytosolic calcium. The PMCA has an important but paradoxical role in cell death and survival. The PMCA can be differentially regulated by caspase/calpain cleavage. Glycolytic ATP supply may be sufficient to fuel the PMCA during metabolic stress. The ATP sensitivity of the PMCA can be regulated by acidic phospholipids.
The plasma membrane Ca2+-ATPase (PMCA) is a ubiquitously expressed, ATP-driven Ca2+ pump that is critical for maintaining low resting cytosolic Ca2+ ([Ca2+]i) in all eukaryotic cells. Since cytotoxic Ca2+ overload has such a central role in cell death, the PMCA represents an essential “linchpin” for the delicate balance between cell survival and cell death. In general, impaired PMCA activity and reduced PMCA expression leads to cytotoxic Ca2+ overload and Ca2+ dependent cell death, both apoptosis and necrosis, whereas maintenance of PMCA activity or PMCA overexpression is generally accepted as being cytoprotective. However, the PMCA has a paradoxical role in cell death depending on the cell type and cellular context. The PMCA can be differentially regulated by Ca2+-dependent proteolysis, can be maintained by a localised glycolytic ATP supply, even in the face of global ATP depletion, and can be profoundly affected by the specific phospholipid environment that it sits within the membrane. The major focus of this review is to highlight some of the controversies surrounding the paradoxical role of the PMCA in cell death and survival, challenging the conventional view of ATP-dependent regulation of the PMCA and how this might influence cell fate.
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Affiliation(s)
- Jason I E Bruce
- Division of Molecular & Clinical Cancer Sciences, School of Medical Sciences, Faculty of Biology, Medicine and Health, University of Manchester, United Kingdom.
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2
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James AD, Patel W, Butt Z, Adiamah M, Dakhel R, Latif A, Uggenti C, Swanton E, Imamura H, Siriwardena AK, Bruce JIE. The Plasma Membrane Calcium Pump in Pancreatic Cancer Cells Exhibiting the Warburg Effect Relies on Glycolytic ATP. J Biol Chem 2015; 290:24760-71. [PMID: 26294767 PMCID: PMC4598988 DOI: 10.1074/jbc.m115.668707] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Indexed: 12/15/2022] Open
Abstract
Evidence suggests that the plasma membrane Ca2+-ATPase (PMCA), which is critical for maintaining a low intracellular Ca2+ concentration ([Ca2+]i), utilizes glycolytically derived ATP in pancreatic ductal adenocarcinoma (PDAC) and that inhibition of glycolysis in PDAC cell lines results in ATP depletion, PMCA inhibition, and an irreversible [Ca2+]i overload. We explored whether this is a specific weakness of highly glycolytic PDAC by shifting PDAC cell (MIA PaCa-2 and PANC-1) metabolism from a highly glycolytic phenotype toward mitochondrial metabolism and assessing the effects of mitochondrial versus glycolytic inhibitors on ATP depletion, PMCA inhibition, and [Ca2+]i overload. The highly glycolytic phenotype of these cells was first reversed by depriving MIA PaCa-2 and PANC-1 cells of glucose and supplementing with α-ketoisocaproate or galactose. These culture conditions resulted in a significant decrease in both glycolytic flux and proliferation rate, and conferred resistance to ATP depletion by glycolytic inhibition while sensitizing cells to mitochondrial inhibition. Moreover, in direct contrast to cells exhibiting a high glycolytic rate, glycolytic inhibition had no effect on PMCA activity and resting [Ca2+]i in α-ketoisocaproate- and galactose-cultured cells, suggesting that the glycolytic dependence of the PMCA is a specific vulnerability of PDAC cells exhibiting the Warburg phenotype.
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Affiliation(s)
| | | | | | | | | | | | - Carolina Uggenti
- the Faculty of Medical and Human Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | | | - Hiromi Imamura
- the Hakubi Center for Advanced Research and Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan, and
| | - Ajith K Siriwardena
- the Hepatobiliary Surgery Unit, Manchester Royal Infirmary, Manchester M13 9NT, United Kingdom
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3
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James AD, Chan A, Erice O, Siriwardena AK, Bruce JIE. Glycolytic ATP fuels the plasma membrane calcium pump critical for pancreatic cancer cell survival. J Biol Chem 2013; 288:36007-19. [PMID: 24158437 PMCID: PMC3861649 DOI: 10.1074/jbc.m113.502948] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Pancreatic cancer is an aggressive cancer with poor prognosis and limited treatment options. Cancer cells rapidly proliferate and are resistant to cell death due, in part, to a shift from mitochondrial metabolism to glycolysis. We hypothesized that this shift is important in regulating cytosolic Ca2+ ([Ca2+]i), as the ATP-dependent plasma membrane Ca2+ ATPase (PMCA) is critical for maintaining low [Ca2+]i and thus cell survival. The present study aimed to determine the relative contribution of mitochondrial versus glycolytic ATP in fuelling the PMCA in human pancreatic cancer cells. We report that glycolytic inhibition induced profound ATP depletion, PMCA inhibition, [Ca2+]i overload, and cell death in PANC1 and MIA PaCa-2 cells. Conversely, inhibition of mitochondrial metabolism had no effect, suggesting that glycolytic ATP is critical for [Ca2+]i homeostasis and thus survival. Targeting the glycolytic regulation of the PMCA may, therefore, be an effective strategy for selectively killing pancreatic cancer while sparing healthy cells.
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Affiliation(s)
- Andrew D James
- From the Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, United Kingdom and
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4
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Bruce JI. Plasma membrane calcium pump regulation by metabolic stress. World J Biol Chem 2010; 1:221-8. [PMID: 21537477 PMCID: PMC3083969 DOI: 10.4331/wjbc.v1.i7.221] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2010] [Revised: 06/30/2010] [Accepted: 07/07/2010] [Indexed: 02/05/2023] Open
Abstract
The plasma membrane Ca2+-ATPase (PMCA) is an ATP-driven pump that is critical for the maintenance of low resting [Ca2+]i in all eukaryotic cells. Metabolic stress, either due to inhibition of mitochondrial or glycolytic metabolism, has the capacity to cause ATP depletion and thus inhibit PMCA activity. This has potentially fatal consequences, particularly for non-excitable cells in which the PMCA is the major Ca2+ efflux pathway. This is because inhibition of the PMCA inevitably leads to cytosolic Ca2+ overload and the consequent cell death. However, the relationship between metabolic stress, ATP depletion and inhibition of the PMCA is not as simple as one would have originally predicted. There is increasing evidence that metabolic stress can lead to the inhibition of PMCA activity independent of ATP or prior to substantial ATP depletion. In particular, there is evidence that the PMCA has its own glycolytic ATP supply that can fuel the PMCA in the face of impaired mitochondrial function. Moreover, membrane phospholipids, mitochondrial membrane potential, caspase/calpain cleavage and oxidative stress have all been implicated in metabolic stress-induced inhibition of the PMCA. The major focus of this review is to challenge the conventional view of ATP-dependent regulation of the PMCA and bring together some of the alternative or additional mechanisms by which metabolic stress impairs PMCA activity resulting in cytosolic Ca2+ overload and cytotoxicity.
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Affiliation(s)
- Jason Ie Bruce
- Jason IE Bruce, Faculty of Life Sciences, The University of Manchester, Manchester M13 9NT, United Kingdom
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5
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Baggaley EM, Elliott AC, Bruce JIE. Oxidant-induced inhibition of the plasma membrane Ca2+-ATPase in pancreatic acinar cells: role of the mitochondria. Am J Physiol Cell Physiol 2008; 295:C1247-60. [PMID: 18787078 DOI: 10.1152/ajpcell.00083.2008] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Impairment of the normal spatiotemporal pattern of intracellular Ca(2+) ([Ca(2+)](i)) signaling, and in particular, the transition to an irreversible "Ca(2+) overload" response, has been implicated in various pathophysiological states. In some diseases, including pancreatitis, oxidative stress has been suggested to mediate this Ca(2+) overload and the associated cell injury. We have previously demonstrated that oxidative stress with hydrogen peroxide (H(2)O(2)) evokes a Ca(2+) overload response and inhibition of plasma membrane Ca(2+)-ATPase (PMCA) in rat pancreatic acinar cells (Bruce JI and Elliott AC. Am J Physiol Cell Physiol 293: C938-C950, 2007). The aim of the present study was to further examine this oxidant-impaired inhibition of the PMCA, focusing on the role of the mitochondria. Using a [Ca(2+)](i) clearance assay in which mitochondrial Ca(2+) uptake was blocked with Ru-360, H(2)O(2) (50 microM-1 mM) markedly inhibited the PMCA activity. This H(2)O(2)-induced inhibition of the PMCA correlated with mitochondrial depolarization (assessed using tetramethylrhodamine methylester fluorescence) but could occur without significant ATP depletion (assessed using Magnesium Green fluorescence). The H(2)O(2)-induced PMCA inhibition was sensitive to the mitochondrial permeability transition pore (mPTP) inhibitors, cyclosporin-A and bongkrekic acid. These data suggest that oxidant-induced opening of the mPTP and mitochondrial depolarization may lead to an inhibition of the PMCA that is independent of mitochondrial Ca(2+) handling and ATP depletion, and we speculate that this may involve the release of a mitochondrial factor. Such a phenomenon may be responsible for the Ca(2+) overload response, and for the transition between apoptotic and necrotic cell death thought to be important in many disease states.
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Affiliation(s)
- Erin M Baggaley
- Faculty of Life Sciences, 2nd Floor Core Technology Facility, 46 Grafton St., Univ. of Manchester, Manchester M13 9NT, UK
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Vanagas L, Rossi RC, Caride AJ, Filoteo AG, Strehler EE, Rossi JPF. Plasma membrane calcium pump activity is affected by the membrane protein concentration: evidence for the involvement of the actin cytoskeleton. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1641-9. [PMID: 17481573 PMCID: PMC2041878 DOI: 10.1016/j.bbamem.2007.03.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 03/08/2007] [Accepted: 03/17/2007] [Indexed: 11/23/2022]
Abstract
Plasma membrane calcium pumps (PMCAs) are integral membrane proteins that actively expel Ca(2+) from the cell. Specific Ca(2+)-ATPase activity of erythrocyte membranes increased steeply up to 1.5-5 times when the membrane protein concentration decreased from 50 microg/ml to 1 microg/ml. The activation by dilution was also observed for ATP-dependent Ca(2+) uptake into vesicles from Sf9 cells over-expressing the PMCA 4b isoform, confirming that it is a property of the PMCA. Dilution of the protein did not modify the activation by ATP, Ca(2+) or Ca(2+)-calmodulin. Treatment with non-ionic detergents did not abolish the dilution effect, suggesting that it was not due to resealing of the membrane vesicles. Pre-incubation of erythrocyte membranes with Cytochalasin D under conditions that promote actin polymerization abolished the dilution effect. Highly-purified, micellar PMCA showed no dilution effect and was not affected by Cytochalasin D. Taken together, these results suggest that the concentration-dependent behavior of the PMCA activity was due to interactions with cytoskeletal proteins. The dilution effect was also observed with different PMCA isoforms, indicating that this is a general phenomenon for all PMCAs.
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Affiliation(s)
- Laura Vanagas
- IQUIFIB, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956 (1113) Buenos Aires, Argentina
| | - Rolando C. Rossi
- IQUIFIB, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956 (1113) Buenos Aires, Argentina
| | - Ariel J. Caride
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA
| | - Adelaida G. Filoteo
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA
| | - Emanuel E. Strehler
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA
| | - Juan Pablo F.C. Rossi
- IQUIFIB, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956 (1113) Buenos Aires, Argentina
- Corresponding author: Address mail:
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7
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Filomatori CV, Rega AF. On the mechanism of activation of the plasma membrane Ca2+-ATPase by ATP and acidic phospholipids. J Biol Chem 2003; 278:22265-71. [PMID: 12660230 DOI: 10.1074/jbc.m302657200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activation of purified and phospholipid-depleted plasma membrane Ca2+-ATPase by phospholipids and ATP was studied. Enzyme activity increased with [ATP] along biphasic curves representing the sum of two Michaelis-Menten equations. Acidic phospholipids (phosphatidylinositol (PI) and phosphatidylserine (PS)) increased Vmax without affecting apparent affinities of the ATP sites. In the presence of 20 microm ATP, phosphorylation of the enzyme preincubated with Ca2+ (CaE1) was very fast (kapp congruent with 400 s-1). vo of phosphorylation of CaE1 increased with [ATP] along a Michaelis-Menten curve (Km of 15 microm) and was phospholipid-independent. Without Ca2+ preincubation (E1 + E2), vo of phosphorylation was also phospholipid-independent, but was slower and increased with [ATP] along biphasic curves. The high affinity component reflected rapid phosphorylation of CaE1, the low affinity component the E2 --> E1 shift, which accelerated to a rate higher than that of the ATPase activity when ATP was bound to the regulatory site. Dephosphorylation of EP did not occur without ATP. Dephosphorylation increased along a biphasic curve with increasing [ATP], showing that ATP accelerated dephosphorylation independently of phospholipid. PI, but not phosphatidylethanolamine (PE), accelerated dephosphorylation even in the absence of ATP. kapp for dephosphorylation was 57 s-1 at 0 microM ATP; that rate was further increased by ATP. Steady-state [EP] x kapp for dephosphorylation varied with [ATP], and matched the Ca2+-ATPase activity measured under the same conditions. Apparently, the catalytic cycle is rate-limited by dephosphorylation. Acidic phospholipids stimulate Ca2+-ATPase activity by accelerating dephosphorylation, while ATP accelerates both dephosphorylation and the conformational change from E2 to E1, further stimulating the ATPase activity.
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Affiliation(s)
- Claudia V Filomatori
- Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Junín 956, 1113 Buenos Aires, Argentina
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Freire MM, Mignaco JA, de Carvalho-Alves PC, Barrabin H, Scofano HM. 3-O-methylfluorescein phosphate as a fluorescent substrate for plasma membrane Ca2+-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1553:238-48. [PMID: 11997133 DOI: 10.1016/s0005-2728(01)00245-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
3-O-methylfluorescein phosphate hydrolysis, catalyzed by purified erythrocyte Ca2+-ATPase in the absence of Ca2+, was slow in the basal state, activated by phosphatidylserine and controlled proteolysis, but not by calmodulin. p-Nitrophenyl phosphate competitively inhibits hydrolysis in the absence of Ca2+, while ATP inhibits it with a complex kinetics showing a high and a low affinity site for ATP. Labeling with fluorescein isothiocyanate impairs the high affinity binding of ATP, but does not appreciably modify the binding of any of the pseudosubstrates. In the presence of calmodulin, an increase in the Ca2+ concentration produces a bell-shaped curve with a maximum at 50 microM Ca2+. At optimal Ca2+ concentration, hydrolysis of 3-O-methylfluorescein phosphate proceeds in the presence of fluorescein isothiocyanate, is competitively inhibited by p-nitrophenyl phosphate and, in contrast to the result observed in the absence of Ca2+, it is activated by calmodulin. In marked contrast with other pseudosubstrates, hydrolysis of 3-O-methylfluorescein phosphate supports Ca2+ transport. This highly specific activity can be used as a continuous fluorescent marker or as a tool to evaluate partial steps from the reaction cycle of plasma membrane Ca2+-ATPases.
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Affiliation(s)
- Monica M Freire
- Departamento de Bioquímica Médica, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, CEP 21941-590, Rio de Janeiro, Brazil
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9
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Romero PJ, Salas V. Alteration by EGTA of the human red cell Ca(2+)-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1240:115-7. [PMID: 8541281 DOI: 10.1016/0005-2736(95)00206-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The effect of EGTA on Ca(2+)-ATPase activity was studied in fragmented membranes and solubilized preparations from human red cells. A dual action was found. At low concentrations (0.1-1 mM), EGTA increased Ca2+ affinity without affecting Vmax. By contrast, at high concentrations (5-10 mM), EGTA was inhibitory. Both effects were partially reversible.
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Affiliation(s)
- P J Romero
- Instituto de Biología Experimental, Facultad de Ciencias, Universidad Central de Venezuela, Caracas, Venezuela
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10
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Gagliardino JJ, Rossi JP. Ca(2+)-ATPase in pancreatic islets: its possible role in the regulation of insulin secretion. DIABETES/METABOLISM REVIEWS 1994; 10:1-17. [PMID: 7956672 DOI: 10.1002/dmr.5610100102] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- J J Gagliardino
- CENEXA-Centro de Endocrinología Experimental y Aplicada (UNLP-CONICET), La Plata, Argentina
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11
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de Carvalho-Alves PC, Freire MM, Barrabin H, Scofano HM. Regulation of the erythrocyte Ca(2+)-ATPase at high pH. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 220:1029-36. [PMID: 8143719 DOI: 10.1111/j.1432-1033.1994.tb18708.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The activation of the Ca(2+)-ATPase from erythrocyte membranes at high pH has been investigated. Following alkalinization and in the absence of regulators, the enzyme exhibits a very high affinity for Ca2+ and a decreased maximal velocity. Either addition of calmodulin, addition of acidic phospholipids, or controlled trypsinization decreases the concentration of effector required to elicit half-maximal activation of the enzyme for calcium to similar values. The increase in affinity for Ca2+, however, is smaller than that observed at neutral pH. The maximal velocity at high pH becomes insensitive to both calmodulin and controlled proteolysis, although calmodulin binds to the protein with similar affinities at pH 7.0 and 8.0, as indicated by similarity in binding to a calmodulin-Sepharose resin and in dependence on calmodulin concentrations when the pH is increased. In contrast to the attenuated effects of calmodulin and proteolysis, at pH 8.0 the enzyme is susceptible to stimulation by phospholipids, indicating that the pathway for transduction of the signal from phospholipids is distinct from that pathway engaged by calmodulin and/or trypsinization. At pH 8.0, phosphatidylinositol induces the modulatory effect of ATP at the regulatory site but calmodulin does not. We suggest that the intraenzymic connection between the calmodulin-binding, autoinhibitory peptide and the nucleotide domain of the enzyme is impaired upon alkalinization, which would account for the differing abilities of the activators to modulate the ATP effects.
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Affiliation(s)
- P C de Carvalho-Alves
- Departamento de Bioquímica Médica, ICB, CCS, Universidade Federal de Rio de Janeiro, Brasil
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12
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Fermin J, Romero PJ. Activation of the human red cell calcium ATPase by calcium pretreatment. J Membr Biol 1994; 137:271-7. [PMID: 8182735 DOI: 10.1007/bf00232595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Some kinetic parameters of the human red cell Ca(2+)-ATPase were studied on calmodulin-free membrane fragments following preincubation at 37 degrees C. After 30 min treatment with EGTA (1 mM) plus dithioerythritol (1 mM), a Vmax of about 0.4 mumol Pi/mg x hr and a Ks of 0.3 microM Ca2+ were found. When Mg2+ (10 mM) or Ca2+ (10 microM) were also added during preincubation, Vmax, but not Ks was altered. Ca2+ was more effective than Mg2+, thus increasing Vmax to about 1.3 mumol P/mg x hr. The presence of both Ca2+ and Mg2+ during pretreatment decreased Ks to 0.15 microM, while having no apparent effect on Vmax. Conversely, addition of ATP (2 mM) with either Ca2+ or Ca2+ plus Mg2+ increased Vmax without affecting Ks. Preincubation with Ca2+ for periods longer than 30 min further increased Vmax and reduced Ks to levels as low as found with calmodulin treatment. The Ca2+ activation was not prevented by adding proteinase inhibitors (iodoacetamide, 10 mM; leupeptin, 200 microM; pepstatin A, 100 microM; phenylmethanesulfonyl fluoride, 100 microM). The electrophoretic pattern of membranes preincubated with or without Mg2+, Ca2+ or Ca2+ plus Mg2+ did not differ significantly from each other. Moreover, immunodetection of Ca(2+)-ATPase by means of polyclonal antibodies revealed no mobility change after the various treatments. The above stimulation was not altered by neomycin (200 microM), washing with EGTA (5 mM) or by both incubating and washing with delipidized serum albumin (1 mg/ml), or omitting dithioerythritol from the preincubation medium.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J Fermin
- Instituto de Biología Experimental, Fac. Ciencias, Universidad Central de Venezuela, Caracas
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Pasa TC, Otero A, Barrabin H, Scofano HM. Distinct mechanisms of inhibition of purified cardiac sarcolemma Ca(2+)-ATPase by two calmodulin antagonists. Biochem Pharmacol 1992; 43:1797-803. [PMID: 1533519 DOI: 10.1016/0006-2952(92)90712-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effects of calmidazolium and compound 48/80 were studied in four different states of activation of the purified Ca(2+)-ATPase from cardiac sarcolemma: "basal" or unactivated, activated by calmodulin, activated by phosphatidylserine, and activated by controlled trypsinization. When assayed in the presence of phosphatidylcholine as the sole phospholipid (basal state), the purified enzyme was resistant to inhibition by calmidazolium (0.1 to 3 microM). In the same range, calmidazolium inhibited the enzyme activated by controlled proteolysis as well as the calmodulin-activated enzyme regardless of the calmodulin concentration. The phosphatidylserine-activated enzyme was inhibited at higher calmidazolium concentrations due to non-specific trapping of the inhibitor by the excess of phospholipid. Addition of calmidazolium did not modify the K0.5 for calcium activation of ATP hydrolysis by the enzyme. The inhibition by calmidazolium was counteracted by Pi. Compound 48/80 also had no effect on the enzyme when only phosphatidylcholine was present and, like calmidazolium, it inhibited the calmodulin-activated enzyme and the phosphatidylserine-activated enzyme. The apparent Ki for inhibition by compound 48/80 was dependent on the calmodulin concentration. However, the enzyme activated by controlled trypsinization was insensitive to compound 48/80. Binding of 48/80 to the enzyme in the presence of phosphatidylserine or calmodulin reversed the increased affinity for Ca2+ caused by these activators.
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Affiliation(s)
- T C Pasa
- Departamento de Bioquimica, Universidade Federal do Rio de Janeiro, Brasil
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14
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Lehotsky J, Raeymaekers L, Missiaen L, Wuytack F, De Smedt H, Casteels R. Stimulation of the catalytic cycle of the Ca2+ pump of porcine plasma-membranes by negatively charged phospholipids. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1105:118-24. [PMID: 1314667 DOI: 10.1016/0005-2736(92)90169-m] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The (Ca(2+)+Mg2+)-ATPase of the plasma membrane is activated by negatively charged phospholipids. The mechanism of this activation was investigated by studying the effect of negatively charged phospholipids on the steady-state phosphointermediate level and on the p-nitrophenylphosphatase activity. Both parameters were differentially affected by different acidic phospholipids. The level of phosphoprotein intermediate was not affected by phosphatidylserine (20% of total phospholipid), but it was increased by 60% by phosphatidylinositol 4-phosphate. Phosphatidylserine increased the p-nitrophenylphosphatase activity, whereas phosphatidylinositol 4-phosphate had no significant effect. It is suggested that phosphatidylinositol 4-phosphate mainly affects a reaction step which leads to accelerated formation of the phosphointermediate, whereas the action of phosphatidylserine would affect two reaction steps, one upstream and one downstream of the phosphointermediate.
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Affiliation(s)
- J Lehotsky
- Laboratory of Physiology, K.U. Leuven, Belgium
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15
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Donnet C, Caride AJ, Fernández HN, Rossi JP. Differential reactivity of lysine residues of the red blood cell Ca2+ pump involved in the E1-E2 conformational equilibrium. Biochem J 1991; 279 ( Pt 1):121-7. [PMID: 1656936 PMCID: PMC1151555 DOI: 10.1042/bj2790121] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
1. Modification of Lys residues of the Ca(2+)-ATPase from human red blood cells with methyl acetimidate (MA) inhibited up to 70% of the Ca(2+)-ATPase activity. Furthermore, calmodulin-activated p-nitrophenyl phosphatase activity was fully inhibited at non-limiting concentrations of MA. 2. Treatment with MA inhibited phosphorylation of the Ca(2+)-ATPase. 3. When the enzyme was treated with 7.2 mM-MA in the presence of 100 microM-Ca2+, Ca(2+)-ATPase activity was decreased by 33%, whereas when the membranes were treated with MA in the presence of 50 microM-VO4(3-), this activity was decreased by only 8%. 4. When membranes were either proteolysed or preincubated with 1 mM-Ca2+, MA quickly inactivated the Ca(2+)-ATPase (k = 1.2 min-1). On the other hand, inactivation of membranes preincubated in the absence of Ca2+ and Mg2+ was slow (k = 0.08 min-1). 5. When the activity was measured in the absence of calmodulin, MA decreased to the same extent the values of KCa (the apparent dissociation constant for Ca2+) and Vmax, but in the presence of calmodulin the treatment decreased Vmax. only. 6. The results are consistent with the idea that MA reacts readily with the Ca(2+)-ATPase when the enzyme is in an E1 conformation, but not an E2 conformation, and that, reciprocally, treatment of the enzyme with MA shifts the enzyme to E1. 7. Provided that Ca2+ is present, ATP, with low apparent affinity (K0.5 = 195 microM), protected against inactivation by MA. However, MA treatment did not change the Km values of either the high-affinity or the low-affinity site for ATP, suggesting that protection results from a shift to a conformation in which the Lys residues are inaccessible to MA.
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Affiliation(s)
- C Donnet
- Instituto de Química y Fisicoquímica Biólogicas, (UBA-CONICET), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina
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16
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Novel effects of calmodulin and calmodulin antagonists on the plasma membrane (Ca2+ + Mg2+)-ATPase from rabbit kidney proximal tubules. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)99217-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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17
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Rossi JP, Caride AJ. Inhibition of the phosphatase activity of the red cell membrane Ca2+ pump by acidic phospholipids. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1061:49-55. [PMID: 1847298 DOI: 10.1016/0005-2736(91)90267-c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The effect of phospholipids was tested on the p-nitrophenylphosphatase activity of the Ca2+ pump. Acidic phospholipids like phosphatidylserine and phosphatidylinositol inhibited the phosphatase activity, while neutral phospholipids like phosphatidylcholine did not. This result contrasts sharply with the known activating effect of acidic phospholipids on the Ca2(+)-ATPase activity of the pump. It is known that the phosphatase activity of the Ca2+ pump can be elicited either by calmodulin and Ca2+ or by ATP and Ca2+. Unlike calmodulin, acidic phospholipids failed to stimulate the phosphatase activity. Furthermore, calmodulin-activated phosphatase was completely inhibited by acidic phospholipids. Maximal inhibition of the ATP-activated phosphatase was only 70%. Inhibition by acidic phospholipids was non-competitive regarding to calmodulin, suggesting that acidic phospholipids and calmodulin do not bind to the same domain of the pump. The presence of Ca2+ was essential for the inhibition, and the apparent affinity for Ca2+ for this effect was increased by acidic phospholipids. Results are consistent with the idea that acidic phospholipids stabilize an enzyme-Ca complex lacking phosphatase activity.
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Affiliation(s)
- J P Rossi
- Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina
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Caride AJ, Rossi JP, Garrahan PJ, Rega AF. Does calmodulin regulate the affinity of the human red cell Ca2+ pump for ATP? BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1027:21-4. [PMID: 2144455 DOI: 10.1016/0005-2736(90)90042-m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
(1) We have reexamined the effects of calmodulin and of the calmodulin antagonist, compound 48/80 on the interaction of ATP at its low-affinity site in the Ca2(+)-ATPase from human red cells. (2) At variance with our earlier proposal (Biochim. Biophys. Acta (1985) 816, 379-386) calmodulin increased the maximum effect of ATP without changing the apparent affinity for ATP at the low-affinity site. Accordingly, ATP increased the maximum activation by calmodulin without altering the apparent affinity of the Ca2(+)-ATPase for calmodulin. (3) Confirming our previous observation (Biochim. Biophys. Acta (1985) 816, 379-386) compound 48/80 lowered the apparent affinity of the Ca2(+)-ATPase for ATP at the low-affinity site. This has to be attributed to a direct effect of this compound on the enzyme rather than to its effect as calmodulin antagonist.
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Affiliation(s)
- A J Caride
- Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina
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Missiaen L, De Smedt H, Droogmans G, Wuytack F, Raeymaekers L, Casteels R. Ruthenium red and compound 48/80 inhibit the smooth-muscle plasma-membrane Ca2+ pump via interaction with associated polyphosphoinositides. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1023:449-54. [PMID: 1692244 DOI: 10.1016/0005-2736(90)90138-e] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We will demonstrate the compound 48/80 and ruthenium red inhibit the smooth-muscle plasma-membrane Ca2+ pump by counteracting the stimulant effect of negatively charged phospholipids. Both substances did not affect the purified enzyme re-activated by pure phosphatidylcholine or phosphatidylinositol and measured in the absence of calmodulin, indicating that under these conditions they did not have a direct effect on the ATPase protein. Ruthenium red and compound 48/80 however inhibited the (Ca2(+) + Mg2+)-ATPase in the presence of phosphatidylinositol 4-phosphate and especially phosphatidylinositol 4,5-bisphosphate. The K0.5 for inhibition was 25 microM ruthenium red and 9 micrograms/ml of compound 48/80. The inhibition by ruthenium red developed slowly with half maximal inhibition occurring after about 75 s while that by compound 48/80 developed immediately within the time required for mixing. The efficacy of ruthenium red increased as the concentration of the acidic phospholipid increased, while no such cooperativity was observed for compound 48/80. Ruthenium red reduced the Vmax for Ca2+ without affecting the affinity for Ca2+, while compound 48/80 decreased both parameters. In conclusion, although ruthenium red and compound 48/80 affect the ATPase differently, both substances most likely inhibit the plasma-membrane Ca2+ pumping by counteracting the stimulation by negatively charged phospholipids.
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Affiliation(s)
- L Missiaen
- Physiological Laboratory, K.U. Leuven, Belgium
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