1
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Hsieh YF, Liu GY, Lee YJ, Yang JJ, Sándor K, Sarang Z, Bononi A, Pinton P, Tretter L, Szondy Z, Tsay GJ. Transglutaminase 2 contributes to apoptosis induction in Jurkat T cells by modulating Ca2+ homeostasis via cross-linking RAP1GDS1. PLoS One 2013; 8:e81516. [PMID: 24349085 PMCID: PMC3859493 DOI: 10.1371/journal.pone.0081516] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 10/23/2013] [Indexed: 12/22/2022] Open
Abstract
Background Transglutaminase 2 (TG2) is a protein cross-linking enzyme known to be associated with the in vivo apoptosis program of T cells. However, its role in the T cell apoptosis program was not investigated yet. Results Here we report that timed overexpression of both the wild type (wt) and the cross-linking mutant of TG2 induced apoptosis in Jurkat T cells, the wt being more effective. Part of TG2 colocalised with mitochondria. WtTG2-induced apoptosis was characterized by enhanced mitochondrial Ca2+ uptake. Ca2+-activated wtTG2 cross-linked RAP1, GTP-GDP dissociation stimulator 1, an unusual guanine exchange factor acting on various small GTPases, to induce a yet uncharacterized signaling pathway that was able to promote the Ca2+ release from the endoplasmic reticulum via both Ins3P and ryanodine sensitive receptors leading to a consequently enhanced mitochondrial Ca2+uptake. Conclusions Our data indicate that TG2 might act as a Ca2+ sensor to amplify endoplasmic reticulum-derived Ca2+ signals to enhance mitochondria Ca2+ uptake. Since enhanced mitochondrial Ca2+ levels were previously shown to sensitize mitochondria for various apoptotic signals, our data demonstrate a novel mechanism through which TG2 can contribute to the induction of apoptosis in certain cell types. Since, as compared to knock out cells, physiological levels of TG2 affected Ca2+ signals in mouse embryonic fibroblasts similar to Jurkat cells, our data might indicate a more general role of TG2 in the regulation of mitochondrial Ca2+ homeostasis.
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Affiliation(s)
- Yu-Fan Hsieh
- Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan
| | - Guang-Yaw Liu
- Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan
| | - Yi-Ju Lee
- Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan
| | - Jiann-Jou Yang
- Department of Biomedical Sciences, Chung Shan Medical University, Taichung, Taiwan
| | - Katalin Sándor
- Department of Biochemistry and Molecular Biology, Research Center of Molecular Medicine, University of Debrecen, Debrecen, Hungary
| | - Zsolt Sarang
- Department of Biochemistry and Molecular Biology, Research Center of Molecular Medicine, University of Debrecen, Debrecen, Hungary
| | - Angela Bononi
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, Interdisciplinary Center for the Study of Inflammation (ICSI), Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Paolo Pinton
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, Interdisciplinary Center for the Study of Inflammation (ICSI), Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - László Tretter
- Department of Medical Biochemistry, Semmelweis University, Neurobiochemical Group of Hungarian Academy of Sciences, Budapest, Hungary
| | - Zsuzsa Szondy
- Department of Biochemistry and Molecular Biology, Research Center of Molecular Medicine, University of Debrecen, Debrecen, Hungary
- * E-mail: (ZS); (GJT)
| | - Gregory J. Tsay
- Institute of Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan
- Department of Internal Medicine, Chung Shan Medical University Hospital, Taichung, Taiwan
- * E-mail: (ZS); (GJT)
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2
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Bobe R, Bredoux R, Corvazier E, Lacabaratz-Porret C, Martin V, Kovács T, Enouf J. How many Ca2+ATPase isoforms are expressed in a cell type? A growing family of membrane proteins illustrated by studies in platelets. Platelets 2009; 16:133-50. [PMID: 16011958 DOI: 10.1080/09537100400016847] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Ca(2+) signaling plays a key role in normal and abnormal platelet functions. Understanding platelet Ca(2+) signaling requires the knowledge of proteins involved in this process. Among these proteins are Ca(2+)ATPases or Ca(2+) pumps that deplete the cytosol of Ca(2+) ions. Here, we will particularly focus on two Ca(2+) pump families: the plasma membrane Ca(2+)ATPases (PMCAs) that extrude cytosolic Ca(2+) towards the extracellular medium and the sarco/endoplasmic reticulum Ca(2+)ATPases (SERCAs) that pump Ca(2+) into the endoplasmic reticulum (ER). In the present review, we will summarize data on platelet Ca(2+)ATPases including their identification and biogenesis. First of all, we will present the Ca(2+)ATPase genes and their isoforms expressed in platelets. We will especially focus on a member of the SERCA family, SERCA3, recently found to give rise to a number of species-specific isoforms. Next, we will describe the differences in Ca(2+)ATPase patterns observed in human and rat platelets. Last, we will analyze how the expression of Ca(2+)ATPase isoforms changes during megakaryocytic maturation and show that megakaryocytopoiesis is associated with a profound reorganization of the expression and/or activity of Ca(2+)ATPases. Taken together, these data provide new aspects of investigations to better understand normal and abnormal platelet Ca(2+) signaling.
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Affiliation(s)
- R Bobe
- INSERM U.689 E6, IFR139 Lariboisière, Hôpital Lariboisière, 8 Rue Guy Patin, 75475 Paris Cedex 10, France
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3
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Morel E, Marcantoni A, Gastineau M, Birkedal R, Rochais F, Garnier A, Lompré AM, Vandecasteele G, Lezoualc'h F. cAMP-binding protein Epac induces cardiomyocyte hypertrophy. Circ Res 2005; 97:1296-304. [PMID: 16269655 DOI: 10.1161/01.res.0000194325.31359.86] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
cAMP is one of the most important second messenger in the heart. The discovery of Epac as a guanine exchange factor (GEF), which is directly activated by cAMP, raises the question of the role of this protein in cardiac cells. Here we show that Epac activation leads to morphological changes and induces expression of cardiac hypertrophic markers. This process is associated with a Ca2+-dependent activation of the small GTPase, Rac. In addition, we found that Epac activates a prohypertrophic signaling pathway, which involves the Ca2+ sensitive phosphatase, calcineurin, and its primary downstream effector, NFAT. Rac is involved in Epac-induced NFAT dependent cardiomyocyte hypertrophy. Blockade of either calcineurin or Rac activity blunts the hypertrophic response elicited by Epac indicating these signaling molecules coordinately regulate cardiac gene expression and cellular growth. Our results thus open new insights into the signaling pathways by which cAMP may mediate its biological effects and identify Epac as a new positive regulator of cardiac growth.
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Affiliation(s)
- Eric Morel
- Cardiologie Cellulaire et Moléculaire, Inserm U-446, IFR-75, Faculté de Pharmacie, Université Paris XI, 5 Rue JB Clément, 92296 Chātenay Malabry, France
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4
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Abstract
An impressive array of cytosolic calcium ([Ca2+](i)) signals exert control over a broad range of physiological processes. The specificity and fidelity of these [Ca2+](i) signals is encoded by the frequency, amplitude, and sub-cellular localization of the response. It is believed that the distinct characteristics of [Ca2+](i) signals underlies the differential activation of effectors and ultimately cellular events. This "shaping" of [Ca2+](i) signals can be achieved by the influence of additional signaling pathways modulating the molecular machinery responsible for generating [Ca2+](i) signals. There is a particularly rich source of potential sites of crosstalk between the cAMP and the [Ca2+](i) signaling pathways. This review will focus on the predominant molecular loci at which these classical signaling systems interact to impact the spatio-temporal pattern of [Ca2+](i) signaling in non-excitable cells.
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Affiliation(s)
- Jason I E Bruce
- Department of Pharmacology & Physiology, School of Medicine and Dentistry, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA.
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5
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den Dekker E, Heemskerk JWM, Gorter G, van der Vuurst H, Donath J, Kroner C, Mikoshiba K, Akkerman JWN. Cyclic AMP raises intracellular Ca(2+) in human megakaryocytes independent of protein kinase A. Arterioscler Thromb Vasc Biol 2002; 22:179-86. [PMID: 11788480 DOI: 10.1161/hq0102.101515] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The immature megakaryoblastic cell line MEG-01 responds to iloprost with an increase in cytosolic Ca(2+) and cAMP. The Ca(2+) response is almost absent in CHRF-288-11 cells, but cAMP formation is preserved in this more mature megakaryoblastic cell line. Also, in human hematopoietic stem cells, iloprost induces a Ca(2+) response and cAMP formation. The Ca(2+) response is downregulated during megakaryocytopoiesis, but cAMP formation remains unchanged. The Ca(2+) increase may be caused by cAMP-mediated inhibition of Ca(2+) sequestration, because it is (1) independent of Ca(2+) entry; (2) mimicked by forskolin, an activator of adenylyl cyclase, and isobutylmethylxanthine, an inhibitor of phosphodiesterases; and (3) preserved in the presence of inhibitors of protein kinase A and inositol-1,4,5-triphosphate receptors. The small GTPase Rap1 has been implicated in the control of Ca(2+) sequestration. Indeed, Rap1 activation parallels the iloprost- and forskolin-induced Ca(2+) increase and is unaffected by the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N',-tetraacetic acid-AM. These findings reveal a novel mechanism for elevating cytosolic Ca(2+) by cAMP, possibly via GTP-Rap1.
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Affiliation(s)
- Els den Dekker
- Thrombosis and Haemostasis Laboratory, Department of Haematology, University Medical Center Utrecht, The Netherlands.
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6
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Kovács T, Felföldi F, Papp B, Pászty K, Bredoux R, Enouf J. All three splice variants of the human sarco/endoplasmic reticulum Ca2+-ATPase 3 gene are translated to proteins: a study of their co-expression in platelets and lymphoid cells. Biochem J 2001; 358:559-68. [PMID: 11535119 PMCID: PMC1222092 DOI: 10.1042/0264-6021:3580559] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The molecular cloning of two previously unknown human sarco/endoplasmic reticulum Ca(2+)-ATPase 3 (SERCA3) 3'-end transcripts, 3b and 3c, has been recently published. Data were lacking, however, for the presence of these SERCA3 variants in different tissue or cell types at the protein level. Here we report the co-expression of three human SERCA3 protein isoforms in platelets and T lymphoid Jurkat cells. Isoform-specific polyclonal anti-peptide antibodies have been generated that recognize specifically the SERCA3a, 3b or 3c splice variants at their C-termini, and this has been confirmed by peptide-competition experiments as well. None of these antibodies cross-reacted with the housekeeping SERCA2b isoform co-expressed endogenously with SERCA3 proteins in non-muscle cells. Although all three SERCA3 isoforms could be detected in platelets, the 3a form was the most abundantly expressed species. Its size matched the apparent size of SERCA3a over-expressed in HEK-293 cells. Immunoprecipitation of the SERCA3 variants from platelet membranes using a PL/IM 430-affinity matrix provided evidence that the putative pan-anti-SERCA3 antibody, PL/IM 430, recognizes all SERCA3 protein isoforms. The epitope for the PL/IM 430 antibody could be localized in a 40 kDa N-terminal tryptic fragment common to all three SERCA3 variants. Comparative Western-blot analysis showed that the expression level of the SERCA3a, 3b and 3c isoforms was more than 10 times lower in Jurkat cells than in platelets, whereas expression of the ubiquitous SERCA2b was nearly identical. This work highlights new Ca(2+)-transporting proteins of haematopoietic cells and provides specific antibodies for their detection.
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Affiliation(s)
- T Kovács
- National Institute of Haematology and Immunology, H-1113 Budapest, Daróczi u. 24, Hungary.
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7
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Franklin IK, Winz RA, Hubbard MJ. Endoplasmic reticulum Ca2+-ATPase pump is up-regulated in calcium-transporting dental enamel cells: a non-housekeeping role for SERCA2b. Biochem J 2001; 358:217-24. [PMID: 11485570 PMCID: PMC1222050 DOI: 10.1042/0264-6021:3580217] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Dental enamel-forming cells face a major challenge to avoid the cytotoxic effects of excess calcium. We have characterized sarcoplasmic/endoplasmic reticulum calcium-ATPase pumps (SERCA) in rat enamel cells to address the proposal that non-mitochondrial calcium stores play a dominant role in transcellular calcium transport. A single major isoform, SERCA2b, was detected during the protein-secretory and calcium-transport stages of enamel formation using reverse-transcriptase PCR, cDNA cloning, Northern analysis and immunoblotting. Most importantly, SERCA2b exhibited a specific 3-fold up-regulation to high expression levels during calcium transport, as determined by quantitative immunoblotting and ATPase assays. Sensitivity of the calcium-dependent ATPase to thapsigargin and three other SERCA inhibitors was characterized. These findings indicate that enamel cells are well-equipped to sequester calcium in endoplasmic reticulum stores and so protect against calcium toxicity, associate SERCA with transcellular calcium transport for the first time, and establish SERCA2b as a molecular and pharmacological target for future investigations of calcium transcytosis. The observed physiological regulation in enamel cells contradicts the widespread perception that SERCA2b is restricted to general housekeeping duties.
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Affiliation(s)
- I K Franklin
- Department of Biochemistry, University of Otago, PO Box 56, 710 Cumberland Street, Dunedin, New Zealand
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8
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Watson EL. GTP-binding proteins and regulated exocytosis. CRITICAL REVIEWS IN ORAL BIOLOGY AND MEDICINE : AN OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION OF ORAL BIOLOGISTS 2000; 10:284-306. [PMID: 10759410 DOI: 10.1177/10454411990100030301] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Regulated exocytosis, which occurs in response to stimuli, is a two-step process involving the docking of secretory granules (SGs) at specific sites on the plasma membrane (PM), with subsequent fusion and release of granule contents. This process plays a crucial role in a number of tissues, including exocrine glands, chromaffin cells, platelets, and mast cells. Over the years, our understanding of the proteins involved in vesicular trafficking has increased dramatically. Evidence from genetic, biochemical, immunological, and functional assays supports a role for ras-like monomeric GTP-binding proteins (smgs) as well as heterotrimeric GTP-binding protein (G-protein) subunits in various steps of the vesicular trafficking pathway, including the transport of secretory vesicles to the PM. Data suggest that the function of GTP-binding proteins is likely related to their localization to specific cellular compartments. The presence of both G-proteins and smgs on secretory vesicles/granules implicates a role for these proteins in the final stages of exocytosis. Molecular mechanisms of exocytosis have been postulated, with the identification of a number of proteins that modify, regulate, and interact with GTP-binding proteins, and with the advent of approaches that assess the functional importance of GTP-binding proteins in downstream, exocytotic events. Further, insight into vesicle targeting and fusion has come from the characterization of a SNAP receptor (SNARE) complex composed of vesicle, PM, and soluble membrane trafficking components, and identification of a functional linkage between GTP-binding and SNARES.
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Affiliation(s)
- E L Watson
- Department of Oral Biology, University of Washington, Health Sciences Center, Seattle 98195-7132, USA
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9
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Pászty K, Kovács T, Lacabaratz-Porret C, Papp B, Enouf J, Filoteo AG, Penniston JT, Enyedi A. Expression of hPMCA4b, the major form of the plasma membrane calcium pump in megakaryoblastoid cells is greatly reduced in mature human platelets. Cell Calcium 1998; 24:129-35. [PMID: 9803313 DOI: 10.1016/s0143-4160(98)90080-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Antibodies 5F10 and JA3 (raised against the erythrocyte Ca2+ pump) were used to identify hPMCA4b as the major form of the plasma membrane Ca2+ pump in human platelets and in three human megakaryoblastoid cell lines, MEG 01, DAMI and CHRF 288-11. 5F10 was used because it has been shown to recognize all known isoforms of the hPMCA and JA3 because it reacts exclusively with hPMCA4b [Caride A.J., Filoteo A.G., Enyedi A., Verma A.K., Penniston J.T. Detection of isoform 4 of the plasma membrane calcium pump in human tissues by using isoform-specific monoclonal antibodies. Biochem J 1996; 316: 353-359]. In addition to hPMCA4b, hPMCA1b was also detected in the megakaryoblastoid cells by using isoform-specific polyclonal antibodies. The apparent size of this isoform, however, was smaller than that seen in HeLa and COS-7 cell membranes indicating the presence of a modified form of hPMCA1b. In platelets, no evidence of the expression of hPMCA1b could be found. The amount of PMCA in these cells was compared with that of the constitutive form of the sarco/endoplasmic reticulum Ca2+ pump in non-muscle cells (SERCA2b) and also with the amount of PMCA in human erythrocytes. A very low level of the plasma membrane Ca2+ pump was found in platelets while in their precursor cells the expression of this Ca2+ pump was much more abundant. Whereas the expression level of PMCA decreased dramatically in mature human platelets, the expression of SERCA2b did not change substantially upon megakaryocytic differentiation.
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Affiliation(s)
- K Pászty
- National Institute of Haematology and Immunology, Budapest, Hungary
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10
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D'Silva NJ, Jacobson KL, Ott SM, Watson EL. Beta-adrenergic-induced cytosolic redistribution of Rap1 in rat parotid acini: role in secretion. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C1667-73. [PMID: 9611133 DOI: 10.1152/ajpcell.1998.274.6.c1667] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Rap1 has recently been identified on the secretory granule membrane and plasma membrane of rat parotid acinar cells (N. J. D'Silva, D. DiJulio, C. B. Belton, K. L. Jacobson, and E. L. Watson. J. Histochem. Cytochem. 45: 965-973, 1997). In the present study, we examined the cellular redistribution of Rap1 following treatment of acini with isoproterenol (ISO), the beta-adrenergic agonist, and determined the relationship between translocation and amylase release. In the presence of ISO, Rap1 translocated to the cytosol in a concentration- and time-dependent manner; this effect was not mimicked by the muscarinic agonist, carbachol. Translocation was maximal at 1 microM ISO and paralleled amylase release immediately after ISO stimulation. Rap1 translocation and amylase release were blocked by the beta-adrenergic antagonist, propranolol, whereas okadaic acid, a downstream secretory inhibitor, significantly blocked amylase release but did not inhibit Rap1 redistribution. Results suggest that the translocation of Rap1 is causally related to secretion and that the role of Rap1 in secretion is at a site proximal to the exocytotic event.
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Affiliation(s)
- N J D'Silva
- Department of Oral Biology, University of Washington, Seattle, Washington 98195, USA
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11
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Lacabaratz-Porret C, Corvazier E, Kovàcs T, Bobe R, Bredoux R, Launay S, Papp B, Enouf J. Platelet sarco/endoplasmic reticulum Ca2+ATPase isoform 3b and Rap 1b: interrelation and regulation in physiopathology. Biochem J 1998; 332 ( Pt 1):173-81. [PMID: 9576865 PMCID: PMC1219465 DOI: 10.1042/bj3320173] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Platelet Ca2+ signalling involves intracellular Ca2+ pools, whose content is controlled by sarco/endoplasmic reticulum Ca2+ATPases (SERCAs). Among these, a key role is played by the inositol trisphosphate-sensitive Ca2+ pool, associated with the SERCA 3b isoform. We have investigated the control of this Ca2+ pool through the cAMP-dependent phosphorylation of the GTP-binding protein, Rap (Ras-proximate) 1b. We first looked for this Ca2+ pool target of regulation by studying the expression of the different SERCA and Rap 1 proteins in human platelets and various cell lines, by Western blotting and reverse transcription-PCR. Since co-expression of Rap 1b and SERCA 3b was obtained, we looked for their protein-protein interaction as a function of the cAMP-dependent phosphorylation of Rap 1b. Co-immunoprecipitations of SERCA 3b and Rap 1b proteins were found in the absence of phosphorylation, induced by the catalytic subunit of the cAMP-dependent protein kinase (csPKA). In contrast, upon pre-treatment of platelet membranes with csPKA, the SERCA 3b dissociated from the Rap 1b protein, in agreement with a role of its phosphorylated state in their interaction. Finally, we looked for adaptation of this complex in a platelet pathological model of hypertension. We investigated the expression of both proteins, as well as the cAMP-dependent phosphorylation of Rap 1b and SERCA 3b activity in platelets from control normotensive Wistar-Kyoto rats and from spontaneously hypertensive rats (SHRs). A decrease in SERCA 3b activity was associated with a decrease in Rap 1b endogenous phosphorylation in SHR platelets, consistent with a functional role in the regulation of the SERCA 3b-associated Ca2+ pool.
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Affiliation(s)
- C Lacabaratz-Porret
- Institut National de la Santé et de la Recherche Médicale U 348, IFR Circulation Lariboisière, Hôpital Lariboisière, 8 rue Guy Patin, 75475 Paris Cedex 10, France
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12
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Treiman M, Caspersen C, Christensen SB. A tool coming of age: thapsigargin as an inhibitor of sarco-endoplasmic reticulum Ca(2+)-ATPases. Trends Pharmacol Sci 1998; 19:131-5. [PMID: 9612087 DOI: 10.1016/s0165-6147(98)01184-5] [Citation(s) in RCA: 469] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Thapsigargin is the most widely used inhibitor of the ubiquitous sarco-endoplasmic reticulum Ca(2+)-ATPases in mammalian cells. Over the past ten years, this guaianolide compound of plant origin has become a popular tool in a host of studies directed at elucidating the mechanisms of intracellular Ca2+ signalling. Its remarkable potency and selectivity have been instrumental in widening our view of the function of intracellular Ca2+ stores to include such key aspects as store-operated Ca2+ entry or the involvement of the stores in protein synthesis or cell growth. In this article Marek Treiman, Casper Caspersen and Søren Brøgger Christensen review the key pharmacological features of thapsigargin action; they also discuss some of the ways in which its unique properties have shown to be important for obtaining new insights into the biology of Ca2+ stores, and how these properties might encompass a therapeutic potential. In parallel, attention is drawn to some of the limitations and pitfalls encountered when working with thapsigargin.
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Affiliation(s)
- M Treiman
- Department of Medical Physiology, Panum Institute, Copenhagen, Denmark
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13
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Roullet JB, Le Quan Sang KH, Luft U, Watanabe M, Otsuka K, McCarron DA, Devynck MA. Inhibition of Ca2+ uptake into A7r5 vascular smooth muscle cells by farnesol: lack of effect on membrane fluidity and Ca2+-ATPase activities. J Hypertens 1997; 15:1723-8. [PMID: 9488229 DOI: 10.1097/00004872-199715120-00079] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Previous studies have shown that farnesol, a 15-carbon nonsterol derivative of mevalonic acid, inhibits vasoconstriction. Because of its lipophilic properties, we hypothesized that farnesol increased membrane dynamics, thus reducing uptake of Ca2+ and contraction. OBJECTIVE To characterize the effect of farnesol on cell membrane fluidity. DESIGN The study was conducted using A7r5 cells, a rat aortic vascular smooth muscle cell line. Inhibition of Ca2+ uptake by farnesol was first established in these cells. Then, the effect of farnesol on membrane dynamics was determined. Finally, to ascertain that activation of Ca2+ extrusion and reuptake processes by farnesol did not occur, Ca2+-ATPase activity was examined. METHODS Membrane fluidity in cell homogenates was estimated using two fluorescent dyes (1,6-diphenyl-1,3,5-hexatriene) and (1-[-(trimethylamino)-phenyl]-6-phenyl-1,3,5-hexatriene). Ca2+ uptake was determined by monitoring the changes in cytosolic Ca2+ concentration ([Ca2+]i) in fura-2-loaded cells after addition of KCI. Ca2+-ATPase activity was measured in 100000 x g cell fractions. RESULTS Farnesol reduced KCI-induced (Ca2+]i transients significantly (P < 0.001), but did not modify membrane dynamic properties [0.214+/-0.007 versus 0.218+/-0.007 (n = 10) and 0.142+/-0.002 versus 0.146+/-0.003 (n = 5) for 1 -[-(trimethylamino)-phenyl]-6-phenyl-1,3,5-hexatriene and 1,6-diphenyl-1,3,5-hexatriene anisotropies, respectively; NS]. Administration of up to 30 micromol/l farnesol did not affect Ca2+-ATPase activity. CONCLUSION Farnesol inhibits KCI-dependent rise of [Ca2+]i in A7r5 cells. This effect of farnesol is not related to a global change in plasma membrane lipid organization or to activation of Ca2+ pumps. Other mechanisms such as direct inhibition of voltage-dependent Ca2+ channels could therefore explain the biologic action of farnesol in the vascular tissue.
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Affiliation(s)
- J B Roullet
- Department of Nephrology, Hypertension and Clinical Pharmacology, Oregon Sciences Health University, Portland 97201, USA
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14
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Isoform Diversity and Regulation of Organellar-Type Ca2+-Transport ATPases. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1569-2558(08)60156-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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15
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Geisler M, Jakobs B, Richter J, Schumann J. Cotranscription of a GTPase gene from the cyanobacterium Synechocystis PCC 6803 and a P-type Ca(2+)-ATPase gene. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1309:189-93. [PMID: 8982253 DOI: 10.1016/s0167-4781(96)00168-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A GTPase gene adjacent to the Ca(2+)-ATPase gene from Synechocystis PCC 6803 has been sequenced. It encodes for a protein of 456 amino acids revealing high homology to so-called 50K proteins of Bacillus subtilis and Pseudomonas putida. Cotranscription of GTPase and Ca(2+)-ATPase genes has been shown by reverse transcription PCR.
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Affiliation(s)
- M Geisler
- Institut für Biochemie der Pflanzen, Heinrich-Heine-Universität Düsseldorf, Germany
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16
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Váradi A, Molnár E, Ostenson CG, Ashcroft SJ. Isoforms of endoplasmic reticulum Ca(2+)-ATPase are differentially expressed in normal and diabetic islets of Langerhans. Biochem J 1996; 319 ( Pt 2):521-7. [PMID: 8912690 PMCID: PMC1217799 DOI: 10.1042/bj3190521] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Glucose-dependent sequestration of Ca2+ into endoplasmic reticulum and its subsequent release play an important role in the control of intracellular Ca2+ concentration, which regulates insulin secretion in pancreatic beta-cells. The active uptake of cytosolic Ca2+ into endoplasmic reticulum is mediated by sarco-(endo)plasmic reticulum Ca(2+)-ATPases (SERCAs). We found, using RT-PCR with isoform-specific primers, that SERCA 2 and SERCA 3 mRNAs are co-expressed in human and rat islets of Langerhans and in the RINm5F beta-cell line. Immunochemical analysis also revealed the existence of two SERCA proteins with molecular masses of 110 and 115 kDa in beta-cell membranes. The 115 kDa protein was identified as SERCA 2b by its reaction with an isoform-specific antibody and the 110 kDa protein most probably corresponds to SERCA 3. The presence of two functionally different SERCA isoforms raises the possibility that they are located in distinct Ca2+ stores. There is evidence that altered Ca2+ handling in the beta-cell may contribute to the decreased insulin secretion seen in non-insulin dependent diabetes mellitus (NIDDM). We therefore investigated SERCA 2 and SERCA 3 mRNA expression by quantitative RT-PCR in islets prepared from Goto-Kakizaki (GK) rats, a non-obese spontaneous model of NIDDM. We found a significant reduction (about 68%) in SERCA 3 isoform expression. Since SERCA 2 expression was not significantly reduced, these genes are independently regulated and probably play distinct roles in islets of Langerhans. The marked decrease of SERCA 3 expression may constitute a defect in Ca2+ signalling in GK rat islets which could be a component of NIDDM.
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Affiliation(s)
- A Váradi
- University of Oxford, Nuffield Department of Clinical Biochemistry, John Radcliffe Hospital Headington, UK
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17
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Wuytack F, Dode L, Baba-Aissa F, Raeymaekers L. The SERCA3-type of organellar Ca2+ pumps. Biosci Rep 1995; 15:299-306. [PMID: 8825032 DOI: 10.1007/bf01788362] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Of all the SERCA pumps, SERCA3 was the latest to be described and the least well known. Its primary structure deviates more than usual from the other members of the SERCA family. It is not known whether its remarkably low affinity for Ca2+ (K0.5 > 1 microM) observed upon expression in the COS cell system occurs also in its normal cellular context. SERCA3 is particularly expressed at high levels in different types of blood cells and related cells like platelets, lymphocytes, mast cells and arterial endothelial cells. It is also found in cerebellar Purkinje neurons. The physiological significance of this expression pattern remains unknown.
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Affiliation(s)
- F Wuytack
- Laboratorium voor Fysiologie, KULeuven, Belgium
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18
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Magnier C, Corvazier E, Aumont MC, Le Jemtel TH, Enouf J. Relationship between Rap1 protein phosphorylation and regulation of Ca2+ transport in platelets: a new approach. Biochem J 1995; 310 ( Pt 2):469-75. [PMID: 7654184 PMCID: PMC1135919 DOI: 10.1042/bj3100469] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Although the interrelationship between the two messengers Ca2+ and cyclic AMP in platelet function is well documented, its mechanism of action still remains to be established. We investigated here the question of the regulation of platelet Ca(2+)-ATPases by cyclic AMP through the phosphorylation of the Rap1 protein using a pathological model. We first found experimental conditions where Ca(2+)-transport by platelet membrane vesicles appeared to be dependent on the phosphorylation of the Rap1 protein. Then, we studied platelets of patients with congestive heart failure for their expression of the potential 97 kDa Ca(2+)-ATPase target of regulation through the Rap1 protein as well as the phosphorylation of the Rap1 protein using the catalytic subunit of the cyclic AMP-dependent protein kinase (C. Sub.). In the first patients studied, we found no significant modification in the expression of the 97 kDa Ca(2+)-ATPase by Western blotting using the PL/IM 430 monoclonal antibody which specifically recognized this isoform. In contrast, the Rap1 protein was differentially phosphorylated when using 15 micrograms/ml of the C. Sub. These results allowed us to use these pathological platelets to study the relationship between the expression of Rap1 protein and the regulation of Ca2+ transport by selecting a patient with severe heart failure. We could show a decrease in the expression as well as in the phosphorylation of Rap1 protein and demonstrate a lower effect of C. Sub. on Ca2+ transport. Finally, by studying a further series of patients, we could confirm that the decrease in Rap1 protein expression in heart failure, whatever its extent, was variable, and could strictly correlate the expression of Rap1 protein with the stimulatory effect of C. Sub. on Ca2+ transport. Besides the evidence for regulation of the expression of the Rap1 protein in platelets from patients with heart failure, these findings constitute a new approach in favour of the regulation of platelet Ca2+ transport through the phosphorylation of the Rap1 protein.
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Affiliation(s)
- C Magnier
- U 348 INSERM, Hôpital Lariboisière, Paris, France
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Quarck R, Bryckaert M, Magnier C, Corvazier E, Bredoux R, de Gunzburg J, Fontenay M, Tobelem G, Enouf J. Evidence for Rap1 in vascular smooth muscle cells. Regulation of their expression by platelet-derived growth factor BB. FEBS Lett 1994; 342:159-64. [PMID: 8143870 DOI: 10.1016/0014-5793(94)80492-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The effect of platelet-derived growth factor (PDGF) on Rap1 expression was investigated in rat vascular smooth muscle cells (SMC). First, evidence for Rap1 proteins was shown by their: (i) detection in membranes using a specific anti-Rap1 antibody, (ii) typical shift in electrophoretic mobility as a consequence of reduction, and (iii) cAMP-induced phosphorylation and immunoprecipitation. Then, the mitogenic activity of 10 ng/ml PDGF AA and BB for 48 h, resulting in a 2- and 5-fold increase in [3H]thymidine incorporation, was correlated with that of total Rap1 protein expression which was found to be 99% +/- 36% and 260% +/- 70%, respectively. Further time-course studies established that this up-regulation of Rap1 proteins was only observed after 48 h of PDGF BB treatment. Lastly, comparative RT-PCR of both rap1a and rap1b mRNAs showed that PDGF BB also up-regulated the rap1a mRNA species, which was 1.5-fold increased in contrast with the rap1b mRNA species. It is concluded that the PDGF BB-induced SMC proliferation is associated with an up-regulation of Rap1a protein.
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Affiliation(s)
- R Quarck
- INSERM U. 348, Hôpital Lariboisière, Paris, France
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