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Liang X, Samways DSK, Wolf K, Bowles EA, Richards JP, Bruno J, Dutertre S, DiPaolo RJ, Egan TM. Quantifying Ca2+ current and permeability in ATP-gated P2X7 receptors. J Biol Chem 2015; 290:7930-42. [PMID: 25645917 DOI: 10.1074/jbc.m114.627810] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ATP-gated P2X7 receptors are prominently expressed in inflammatory cells and play a key role in the immune response. A major consequence of receptor activation is the regulated influx of Ca(2+) through the self-contained cation non-selective channel. Although the physiological importance of the resulting rise in intracellular Ca(2+) is universally acknowledged, the biophysics of the Ca(2+) flux responsible for the effects are poorly understood, largely because traditional methods of measuring Ca(2+) permeability are difficult to apply to P2X7 receptors. Here we use an alternative approach, called dye-overload patch-clamp photometry, to quantify the agonist-gated Ca(2+) flux of recombinant P2X7 receptors of dog, guinea pig, human, monkey, mouse, rat, and zebrafish. We find that the magnitude of the Ca(2+) component of the ATP-gated current depends on the species of origin, the splice variant, and the concentration of the purinergic agonist. We also measured a significant contribution of Ca(2+) to the agonist-gated current of the native P2X7Rs of mouse and human immune cells. Our results provide cross-species quantitative measures of the Ca(2+) current of the P2X7 receptor for the first time, and suggest that the cytoplasmic N terminus plays a meaningful role in regulating the flow of Ca(2+) through the channel.
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Affiliation(s)
- Xin Liang
- From the Department of Pharmacological and Physiological Science and Center for Neuroscience, and
| | - Damien S K Samways
- the Department of Biology, Clarkson University, Potsdam, New York 13699, and
| | - Kyle Wolf
- the Departments of Molecular Microbiology and Immunology and
| | - Elizabeth A Bowles
- From the Department of Pharmacological and Physiological Science and Center for Neuroscience, and
| | - Jennifer P Richards
- From the Department of Pharmacological and Physiological Science and Center for Neuroscience, and
| | - Jonathan Bruno
- Internal Medicine, Saint Louis University School of Medicine, St. Louis, Missouri 63104
| | - Sébastien Dutertre
- the Institut des Biomolécules Max Mousseron, UMR 5247, Université Montpellier 2, CNRS, Montpellier, France
| | | | - Terrance M Egan
- From the Department of Pharmacological and Physiological Science and Center for Neuroscience, and
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2
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Ousingsawat J, Wanitchakool P, Schreiber R, Wuelling M, Vortkamp A, Kunzelmann K. Anoctamin-6 controls bone mineralization by activating the calcium transporter NCX1. J Biol Chem 2015; 290:6270-80. [PMID: 25589784 DOI: 10.1074/jbc.m114.602979] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Anoctamin-6 (Ano6, TMEM16F) belongs to a family of putative Ca(2+)-activated Cl(-) channels and operates as membrane phospholipid scramblase. Deletion of Ano6 leads to reduced skeleton size, skeletal deformities, and mineralization defects in mice. However, it remains entirely unclear how a lack of Ano6 leads to a delay in bone mineralization by osteoblasts. The Na(+)/Ca(2+) exchanger NCX1 was found to interact with Ano6 in a two-hybrid split-ubiquitin screen. Using human osteoblasts and osteoblasts from Ano6(-/-) and WT mice, we demonstrate that NCX1 requires Ano6 to efficiently translocate Ca(2+) out of osteoblasts into the calcifying bone matrix. Ca(2+)-activated anion currents are missing in primary osteoblasts isolated from Ano6 null mice. Our findings demonstrate the importance of NCX1 for bone mineralization and explain why deletion of an ion channel leads to the observed mineralization defect: Ano6 Cl(-) currents are probably required to operate as a Cl(-) bypass channel, thereby compensating net Na(+) charge movement by NCX1.
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Affiliation(s)
- Jiraporn Ousingsawat
- From the Institut für Physiologie, Universität Regensburg, D-93053 Regensburg and
| | | | - Rainer Schreiber
- From the Institut für Physiologie, Universität Regensburg, D-93053 Regensburg and
| | - Manuela Wuelling
- the Department Entwicklungsbiologie, Fakultät für Biologie, Universität Duisburg-Essen, 45141 Essen, Germany
| | - Andrea Vortkamp
- the Department Entwicklungsbiologie, Fakultät für Biologie, Universität Duisburg-Essen, 45141 Essen, Germany
| | - Karl Kunzelmann
- From the Institut für Physiologie, Universität Regensburg, D-93053 Regensburg and
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3
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von Stockum S, Giorgio V, Trevisan E, Lippe G, Glick GD, Forte MA, Da-Rè C, Checchetto V, Mazzotta G, Costa R, Szabò I, Bernardi P. F-ATPase of Drosophila melanogaster forms 53-picosiemen (53-pS) channels responsible for mitochondrial Ca2+-induced Ca2+ release. J Biol Chem 2014; 290:4537-4544. [PMID: 25550160 DOI: 10.1074/jbc.c114.629766] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondria of Drosophila melanogaster undergo Ca(2+)-induced Ca(2+) release through a putative channel (mCrC) that has several regulatory features of the permeability transition pore (PTP). The PTP is an inner membrane channel that forms from F-ATPase, possessing a conductance of 500 picosiemens (pS) in mammals and of 300 pS in yeast. In contrast to the PTP, the mCrC of Drosophila is not permeable to sucrose and appears to be selective for Ca(2+) and H(+). We show (i) that like the PTP, the mCrC is affected by the sense of rotation of F-ATPase, by Bz-423, and by Mg(2+)/ADP; (ii) that expression of human cyclophilin D in mitochondria of Drosophila S2R(+) cells sensitizes the mCrC to Ca(2+) but does not increase its apparent size; and (iii) that purified dimers of D. melanogaster F-ATPase reconstituted into lipid bilayers form 53-pS channels activated by Ca(2+) and thiol oxidants and inhibited by Mg(2+)/γ-imino ATP. These findings indicate that the mCrC is the PTP of D. melanogaster and that the signature conductance of F-ATPase channels depends on unique structural features that may underscore specific roles in different species.
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Affiliation(s)
| | | | | | - Giovanna Lippe
- the Department of Food Science, University of Udine, I-33100 Udine, Italy
| | - Gary D Glick
- the Department of Chemistry, Graduate Program in Immunology, University of Michigan, Ann Arbor, Michigan 48109, and
| | - Michael A Forte
- the Vollum Institute, Oregon Health and Sciences University, Portland, Oregon 97239
| | - Caterina Da-Rè
- Biology, University of Padova and Consiglio Nazionale delle Ricerche Neuroscience Institute, I-35131 Padova, Italy
| | - Vanessa Checchetto
- Biology, University of Padova and Consiglio Nazionale delle Ricerche Neuroscience Institute, I-35131 Padova, Italy
| | - Gabriella Mazzotta
- Biology, University of Padova and Consiglio Nazionale delle Ricerche Neuroscience Institute, I-35131 Padova, Italy
| | - Rodolfo Costa
- Biology, University of Padova and Consiglio Nazionale delle Ricerche Neuroscience Institute, I-35131 Padova, Italy
| | - Ildikò Szabò
- Biology, University of Padova and Consiglio Nazionale delle Ricerche Neuroscience Institute, I-35131 Padova, Italy
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4
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Zhang W, Zhang X, González-Cobos JC, Stolwijk JA, Matrougui K, Trebak M. Leukotriene-C4 synthase, a critical enzyme in the activation of store-independent Orai1/Orai3 channels, is required for neointimal hyperplasia. J Biol Chem 2014; 290:5015-5027. [PMID: 25540197 DOI: 10.1074/jbc.m114.625822] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Leukotriene-C4 synthase (LTC4S) generates LTC4 from arachidonic acid metabolism. LTC4 is a proinflammatory factor that acts on plasma membrane cysteinyl leukotriene receptors. Recently, however, we showed that LTC4 was also a cytosolic second messenger that activated store-independent LTC4-regulated Ca(2+) (LRC) channels encoded by Orai1/Orai3 heteromultimers in vascular smooth muscle cells (VSMCs). We showed that Orai3 and LRC currents were up-regulated in medial and neointimal VSMCs after vascular injury and that Orai3 knockdown inhibited LRC currents and neointimal hyperplasia. However, the role of LTC4S in neointima formation remains unknown. Here we show that LTC4S knockdown inhibited LRC currents in VSMCs. We performed in vivo experiments where rat left carotid arteries were injured using balloon angioplasty to cause neointimal hyperplasia. Neointima formation was associated with up-regulation of LTC4S protein expression in VSMCs. Inhibition of LTC4S expression in injured carotids by lentiviral particles encoding shRNA inhibited neointima formation and inward and outward vessel remodeling. LRC current activation did not cause nuclear factor for activated T cells (NFAT) nuclear translocation in VSMCs. Surprisingly, knockdown of either LTC4S or Orai3 yielded more robust and sustained Akt1 and Akt2 phosphorylation on Ser-473/Ser-474 upon serum stimulation. LTC4S and Orai3 knockdown inhibited VSMC migration in vitro with no effect on proliferation. Akt activity was suppressed in neointimal and medial VSMCs from injured vessels at 2 weeks postinjury but was restored when the up-regulation of either LTC4S or Orai3 was prevented by shRNA. We conclude that LTC4S and Orai3 altered Akt signaling to promote VSMC migration and neointima formation.
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Affiliation(s)
- Wei Zhang
- From the The State University of New York College of Nanoscale Science and Engineering, Albany, New York 12203,; Center for Cardiovascular Sciences, Albany Medical College, Albany, New York 12208, and
| | - Xuexin Zhang
- From the The State University of New York College of Nanoscale Science and Engineering, Albany, New York 12203
| | - José C González-Cobos
- From the The State University of New York College of Nanoscale Science and Engineering, Albany, New York 12203,; Center for Cardiovascular Sciences, Albany Medical College, Albany, New York 12208, and
| | - Judith A Stolwijk
- From the The State University of New York College of Nanoscale Science and Engineering, Albany, New York 12203
| | - Khalid Matrougui
- Department of Physiological Sciences, East Virginia Medical School, Norfolk, Virginia 23507
| | - Mohamed Trebak
- From the The State University of New York College of Nanoscale Science and Engineering, Albany, New York 12203,; Center for Cardiovascular Sciences, Albany Medical College, Albany, New York 12208, and.
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5
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Secondo A, Esposito A, Sirabella R, Boscia F, Pannaccione A, Molinaro P, Cantile M, Ciccone R, Sisalli MJ, Scorziello A, Di Renzo G, Annunziato L. Involvement of the Na+/Ca2+ exchanger isoform 1 (NCX1) in neuronal growth factor (NGF)-induced neuronal differentiation through Ca2+-dependent Akt phosphorylation. J Biol Chem 2014; 290:1319-31. [PMID: 25416782 DOI: 10.1074/jbc.m114.555516] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
NGF induces neuronal differentiation by modulating [Ca(2+)]i. However, the role of the three isoforms of the main Ca(2+)-extruding system, the Na(+)/Ca(2+) exchanger (NCX), in NGF-induced differentiation remains unexplored. We investigated whether NCX1, NCX2, and NCX3 isoforms could play a relevant role in neuronal differentiation through the modulation of [Ca(2+)]i and the Akt pathway. NGF caused progressive neurite elongation; a significant increase of the well known marker of growth cones, GAP-43; and an enhancement of endoplasmic reticulum (ER) Ca(2+) content and of Akt phosphorylation through an early activation of ERK1/2. Interestingly, during NGF-induced differentiation, the NCX1 protein level increased, NCX3 decreased, and NCX2 remained unaffected. At the same time, NCX total activity increased. Moreover, NCX1 colocalized and coimmunoprecipitated with GAP-43, and NCX1 silencing prevented NGF-induced effects on GAP-43 expression, Akt phosphorylation, and neurite outgrowth. On the other hand, the overexpression of its neuronal splicing isoform, NCX1.4, even in the absence of NGF, induced an increase in Akt phosphorylation and GAP-43 protein expression. Interestingly, tetrodotoxin-sensitive Na(+) currents and 1,3-benzenedicarboxylic acid, 4,4'-[1,4,10-trioxa-7,13-diazacyclopentadecane-7,13-diylbis(5-methoxy-6,12-benzofurandiyl)]bis-, tetrakis[(acetyloxy)methyl] ester-detected [Na(+)]i significantly increased in cells overexpressing NCX1.4 as well as ER Ca(2+) content. This latter effect was prevented by tetrodotoxin. Furthermore, either the [Ca(2+)]i chelator(1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid) (BAPTA-AM) or the PI3K inhibitor LY 294002 prevented Akt phosphorylation and GAP-43 protein expression rise in NCX1.4 overexpressing cells. Moreover, in primary cortical neurons, NCX1 silencing prevented Akt phosphorylation, GAP-43 and MAP2 overexpression, and neurite elongation. Collectively, these data show that NCX1 participates in neuronal differentiation through the modulation of ER Ca(2+) content and PI3K signaling.
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Affiliation(s)
- Agnese Secondo
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and
| | - Alba Esposito
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and
| | - Rossana Sirabella
- the Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) SDN, Naples 80143, Italy
| | - Francesca Boscia
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and
| | - Anna Pannaccione
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and
| | - Pasquale Molinaro
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and
| | - Maria Cantile
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and
| | - Roselia Ciccone
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and
| | - Maria Josè Sisalli
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and
| | - Antonella Scorziello
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and
| | - Gianfranco Di Renzo
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and
| | - Lucio Annunziato
- From the Department of Neuroscience and Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Via Sergio Pansini 5, Naples 80131, Italy and the Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) SDN, Naples 80143, Italy
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6
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Abstract
K(+)-dependent Na(+)/Ca(2+)-exchangers are broadly expressed in various tissues, and particularly enriched in neurons of the brain. The distinct physiological roles for the different members of this Ca(2+) transporter family are, however, not well described. Here we show that gene-targeted mice lacking the K(+)-dependent Na(+)/Ca(2+)-exchanger, NCKX4 (gene slc24a4 or Nckx4), display a remarkable anorexia with severe hypophagia and weight loss. Feeding and satiety are coordinated centrally by melanocortin-4 receptors (MC4R) in neurons of the hypothalamic paraventricular nucleus (PVN). The hypophagic response of Nckx4 knock-out mice is accompanied by hyperactivation of neurons in the PVN, evidenced by high levels of c-Fos expression. The activation of PVN neurons in both fasted Nckx4 knock-out and glucose-injected wild-type animals is blocked by Ca(2+) removal and MC4R antagonists. In cultured hypothalamic neurons, melanocyte stimulating hormone induces an MC4R-dependent and sustained Ca(2+) signal, which requires phospholipase C activity and plasma membrane Ca(2+) entry. The Ca(2+) signal is enhanced in hypothalamic neurons from Nckx4 knock-out animals, and is depressed in cells in which NCKX4 is overexpressed. Finally, MC4R-dependent oxytocin expression in the PVN, a key essential step in satiety, is prevented by blocking phospholipase C activation or Ca(2+) entry. These findings highlight an essential, and to our knowledge previously unknown, role for Ca(2+) signaling in the MC4R pathway that leads to satiety, and a novel non-redundant role for NCKX4-mediated Ca(2+) extrusion in controlling MC4R signaling and feeding behavior. Together, these findings highlight a novel pathway that potentially could be exploited to develop much needed new therapeutics to tackle eating disorders and obesity.
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Affiliation(s)
- Xiao-Fang Li
- From the Department of Biochemistry and Molecular Biology, Hotchkiss Brain Institute and Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4Z6, Canada
| | - Jonathan Lytton
- From the Department of Biochemistry and Molecular Biology, Hotchkiss Brain Institute and Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4Z6, Canada
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7
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Yang YM, Lee J, Jo H, Park S, Chang I, Muallem S, Shin DM. Homer2 protein regulates plasma membrane Ca²⁺-ATPase-mediated Ca²⁺ signaling in mouse parotid gland acinar cells. J Biol Chem 2014; 289:24971-9. [PMID: 25049230 DOI: 10.1074/jbc.m114.577221] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Homer proteins are scaffold molecules with a domain structure consisting of an N-terminal Ena/VASP homology 1 protein-binding domain and a C-terminal leucine zipper/coiled-coil domain. The Ena/VASP homology 1 domain recognizes proline-rich motifs and binds multiple Ca(2+)-signaling proteins, including G protein-coupled receptors, inositol 1,4,5-triphosphate receptors, ryanodine receptors, and transient receptor potential channels. However, their role in Ca(2+) signaling in nonexcitable cells is not well understood. In this study, we investigated the role of Homer2 on Ca(2+) signaling in parotid gland acinar cells using Homer2-deficient (Homer2(-/-)) mice. Homer2 is localized at the apical pole in acinar cells. Deletion of Homer2 did not affect inositol 1,4,5-triphosphate receptor localization or channel activity and did not affect the expression and activity of sarco/endoplasmic reticulum Ca(2+)-ATPase pumps. In contrast, Homer2 deletion markedly increased expression of plasma membrane Ca(2+)-ATPase (PMCA) pumps, in particular PMCA4, at the apical pole. Accordingly, Homer2 deficiency increased Ca(2+) extrusion by acinar cells. These findings were supported by co-immunoprecipitation of Homer2 and PMCA in wild-type parotid cells and transfected human embryonic kidney 293 (HEK293) cells. We identified a Homer-binding PPXXF-like motif in the N terminus of PMCA that is required for interaction with Homer2. Mutation of the PPXXF-like motif did not affect the interaction of PMCA with Homer1 but inhibited its interaction with Homer2 and increased Ca(2+) clearance by PMCA. These findings reveal an important regulation of PMCA by Homer2 that has a central role on PMCA-mediated Ca(2+) signaling in parotid acinar cells.
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Affiliation(s)
- Yu-Mi Yang
- From the Department of Oral Biology, BK21 PLUS Project, Yonsei University College of Dentistry, Seoul 120-752, Korea
| | - Jiae Lee
- From the Department of Oral Biology, BK21 PLUS Project, Yonsei University College of Dentistry, Seoul 120-752, Korea
| | - Hae Jo
- the College of Life Sciences and Graduate School of Biotechnology, Kyunghee University, Global Campus, Gyeonggi 446-701, Korea, and
| | - Soonhong Park
- From the Department of Oral Biology, BK21 PLUS Project, Yonsei University College of Dentistry, Seoul 120-752, Korea
| | - Inik Chang
- From the Department of Oral Biology, BK21 PLUS Project, Yonsei University College of Dentistry, Seoul 120-752, Korea
| | - Shmuel Muallem
- the Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - Dong Min Shin
- From the Department of Oral Biology, BK21 PLUS Project, Yonsei University College of Dentistry, Seoul 120-752, Korea,
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Samad A, James A, Wong J, Mankad P, Whitehouse J, Patel W, Alves-Simoes M, Siriwardena AK, Bruce JIE. Insulin protects pancreatic acinar cells from palmitoleic acid-induced cellular injury. J Biol Chem 2014; 289:23582-95. [PMID: 24993827 PMCID: PMC4156068 DOI: 10.1074/jbc.m114.589440] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Acute pancreatitis is a serious and sometimes fatal inflammatory disease where the pancreas digests itself. The non-oxidative ethanol metabolites palmitoleic acid (POA) and POA-ethylester (POAEE) are reported to induce pancreatitis caused by impaired mitochondrial metabolism, cytosolic Ca2+ ([Ca2+]i) overload and necrosis of pancreatic acinar cells. Metabolism and [Ca2+]i are linked critically by the ATP-driven plasma membrane Ca2+-ATPase (PMCA) important for maintaining low resting [Ca2+]i. The aim of the current study was to test the protective effects of insulin on cellular injury induced by the pancreatitis-inducing agents, ethanol, POA, and POAEE. Rat pancreatic acinar cells were isolated by collagenase digestion and [Ca2+]i was measured by fura-2 imaging. An in situ [Ca2+]i clearance assay was used to assess PMCA activity. Magnesium green (MgGreen) and a luciferase-based ATP kit were used to assess cellular ATP depletion. Ethanol (100 mm) and POAEE (100 μm) induced a small but irreversible Ca2+ overload response but had no significant effect on PMCA activity. POA (50–100 μm) induced a robust Ca2+ overload, ATP depletion, inhibited PMCA activity, and consequently induced necrosis. Insulin pretreatment (100 nm for 30 min) prevented the POA-induced Ca2+ overload, ATP depletion, inhibition of the PMCA, and necrosis. Moreover, the insulin-mediated protection of the POA-induced Ca2+ overload was partially prevented by the phosphoinositide-3-kinase (PI3K) inhibitor, LY294002. These data provide the first evidence that insulin directly protects pancreatic acinar cell injury induced by bona fide pancreatitis-inducing agents, such as POA. This may have important therapeutic implications for the treatment of pancreatitis.
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Affiliation(s)
- Aysha Samad
- From the Faculty of Life Sciences, The University of Manchester, M13 9NT Manchester and
| | - Andrew James
- From the Faculty of Life Sciences, The University of Manchester, M13 9NT Manchester and
| | - James Wong
- From the Faculty of Life Sciences, The University of Manchester, M13 9NT Manchester and
| | - Parini Mankad
- From the Faculty of Life Sciences, The University of Manchester, M13 9NT Manchester and
| | - John Whitehouse
- From the Faculty of Life Sciences, The University of Manchester, M13 9NT Manchester and
| | - Waseema Patel
- From the Faculty of Life Sciences, The University of Manchester, M13 9NT Manchester and
| | - Marta Alves-Simoes
- From the Faculty of Life Sciences, The University of Manchester, M13 9NT Manchester and
| | - Ajith K Siriwardena
- the Hepatobiliary Surgery Unit, Manchester Royal Infirmary, M13 9WL Manchester, United Kingdom
| | - Jason I E Bruce
- From the Faculty of Life Sciences, The University of Manchester, M13 9NT Manchester and
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9
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Michel LYM, Verkaart S, Koopman WJH, Willems PHGM, Hoenderop JGJ, Bindels RJM. Function and regulation of the Na+-Ca2+ exchanger NCX3 splice variants in brain and skeletal muscle. J Biol Chem 2014; 289:11293-11303. [PMID: 24616101 DOI: 10.1074/jbc.m113.529388] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Isoform 3 of the Na(+)-Ca(2+) exchanger (NCX3) is crucial for maintaining intracellular calcium ([Ca(2+)]i) homeostasis in excitable tissues. In this sense NCX3 plays a key role in neuronal excitotoxicity and Ca(2+) extrusion during skeletal muscle relaxation. Alternative splicing generates two variants (NCX3-AC and NCX3-B). Here, we demonstrated that NCX3 variants display a tissue-specific distribution in mice, with NCX3-B as mostly expressed in brain and NCX-AC as predominant in skeletal muscle. Using Fura-2-based Ca(2+) imaging, we measured the capacity and regulation of the two variants during Ca(2+) extrusion and uptake in different conditions. Functional studies revealed that, although both variants are activated by intracellular sodium ([Na(+)]i), NCX3-AC has a higher [Na(+)]i sensitivity, as Ca(2+) influx is observed in the presence of extracellular Na(+). This effect could be partially mimicked for NCX3-B by mutating several glutamate residues in its cytoplasmic loop. In addition, NCX3-AC displayed a higher capacity of both Ca(2+) extrusion and uptake compared with NCX3-B, together with an increased sensitivity to intracellular Ca(2+). Strikingly, substitution of Glu(580) in NCX3-B with its NCX3-AC equivalent Lys(580) recapitulated the functional properties of NCX3-AC regarding Ca(2+) sensitivity, Lys(580) presumably acting through a structure stabilization of the Ca(2+) binding site. The higher Ca(2+) uptake capacity of NCX3-AC compared with NCX3-B is in line with the necessity to restore Ca(2+) levels in the sarcoplasmic reticulum during prolonged exercise. The latter result, consistent with the high expression in the slow-twitch muscle, suggests that this variant may contribute to the Ca(2+) handling beyond that of extruding Ca(2+).
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Affiliation(s)
- Lauriane Y M Michel
- From the Departments of Physiology and Radboud University Medical Centre, 6500HB Nijmegen, The Netherlands; Centre for System Biology and Bioenergetics, Radboud University Medical Centre, 6500HB Nijmegen, The Netherlands
| | - Sjoerd Verkaart
- From the Departments of Physiology and Radboud University Medical Centre, 6500HB Nijmegen, The Netherlands
| | - Werner J H Koopman
- Centre for System Biology and Bioenergetics, Radboud University Medical Centre, 6500HB Nijmegen, The Netherlands; Departments of Biochemistry, Radboud University Medical Centre, 6500HB Nijmegen, The Netherlands
| | - Peter H G M Willems
- Centre for System Biology and Bioenergetics, Radboud University Medical Centre, 6500HB Nijmegen, The Netherlands; Departments of Biochemistry, Radboud University Medical Centre, 6500HB Nijmegen, The Netherlands
| | - Joost G J Hoenderop
- From the Departments of Physiology and Radboud University Medical Centre, 6500HB Nijmegen, The Netherlands
| | - René J M Bindels
- From the Departments of Physiology and Radboud University Medical Centre, 6500HB Nijmegen, The Netherlands; Centre for System Biology and Bioenergetics, Radboud University Medical Centre, 6500HB Nijmegen, The Netherlands.
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10
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Abstract
The transport of calcium to the extracellular space carried out by plasma membrane Ca(2+) pumps (PMCAs) is essential for maintaining low Ca(2+) concentrations in the cytosol of eukaryotic cells. The activity of PMCAs is controlled by autoinhibition. Autoinhibition is relieved by the binding of Ca(2+)-calmodulin to the calmodulin-binding autoinhibitory sequence, which in the human PMCA is located in the C-terminal segment and results in a PMCA of high maximal velocity of transport and high affinity for Ca(2+). Autoinhibition involves the intramolecular interaction between the autoinhibitory domain and a not well defined region of the molecule near the catalytic site. Here we show that the fusion of GFP to the C terminus of the h4xb PMCA causes partial loss of autoinhibition by specifically increasing the Vmax. Mutation of residue Glu(99) to Lys in the cytosolic portion of the M1 transmembrane helix at the other end of the molecule brought the Vmax of the h4xb PMCA to near that of the calmodulin-activated enzyme without increasing the apparent affinity for Ca(2+). Altogether, the results suggest that the autoinhibitory interaction of the extreme C-terminal segment of the h4 PMCA is disturbed by changes of negatively charged residues of the N-terminal region. This would be consistent with a recently proposed model of an autoinhibited form of the plant ACA8 pump, although some differences are noted.
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Affiliation(s)
- Luciana R Mazzitelli
- Instituto de Química y Fisicoquímica Biológicas-Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, 1113 Buenos Aires, Argentina
| | - Hugo P Adamo
- Instituto de Química y Fisicoquímica Biológicas-Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, 1113 Buenos Aires, Argentina.
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11
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Abstract
The three-dimensional structure of the PMCA pump has not been solved, but its basic mechanistic properties are known to repeat those of the other Ca(2+) pumps. However, the pump also has unique properties. They concern essentially its numerous regulatory mechanisms, the most important of which is the autoinhibition by its C-terminal tail. Other regulatory mechanisms involve protein kinases and the phospholipids of the membrane in which the pump is embedded. Permanent activation of the pump, e.g. by calmodulin, is physiologically as harmful to cells as its absence. The concept is now emerging that the global control of cell Ca(2+) may not be the main function of the pump; in some cell types, it could even be irrelevant. The main pump role would be the regulation of Ca(2+) in cell microdomains in which the pump co-segregates with partners that modulate the Ca(2+) message and transduce it to important cell functions.
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Affiliation(s)
| | - Marta Giacomello
- Venetian Institute of Molecular Medicine, University of Padova, 35129 Padova, Italy
| | - Ernesto Carafoli
- Venetian Institute of Molecular Medicine, University of Padova, 35129 Padova, Italy.
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12
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Mangialavori IC, Ferreira-Gomes MS, Saffioti NA, González-Lebrero RM, Rossi RC, Rossi JPFC. Conformational changes produced by ATP binding to the plasma membrane calcium pump. J Biol Chem 2013; 288:31030-41. [PMID: 24025327 DOI: 10.1074/jbc.m113.494633] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The aim of this work was to study the plasma membrane calcium pump (PMCA) reaction cycle by characterizing conformational changes associated with calcium, ATP, and vanadate binding to purified PMCA. This was accomplished by studying the exposure of PMCA to surrounding phospholipids by measuring the incorporation of the photoactivatable phosphatidylcholine analog 1-O-hexadecanoyl-2-O-[9-[[[2-[(125)I]iodo-4-(trifluoromethyl-3H-diazirin-3-yl)benzyl]oxy]carbonyl]nonanoyl]-sn-glycero-3-phosphocholine to the protein. ATP could bind to the different vanadate-bound states of the enzyme either in the presence or in the absence of Ca(2+) with high apparent affinity. Conformational movements of the ATP binding domain were determined using the fluorescent analog 2'(3')-O-(2,4,6-trinitrophenyl)adenosine 5'-triphosphate. To assess the conformational behavior of the Ca(2+) binding domain, we also studied the occlusion of Ca(2+), both in the presence and in the absence of ATP and with or without vanadate. Results show the existence of occluded species in the presence of vanadate and/or ATP. This allowed the development of a model that describes the transport of Ca(2+) and its relation with ATP hydrolysis. This is the first approach that uses a conformational study to describe the PMCA P-type ATPase reaction cycle, adding important features to the classical E1-E2 model devised using kinetics methodology only.
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Affiliation(s)
- Irene C Mangialavori
- From the Instituto de Química y Fisicoquímica Biologicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Junín 956 (1113) Buenos Aires, Argentina
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13
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Akin BL, Hurley TD, Chen Z, Jones LR. The structural basis for phospholamban inhibition of the calcium pump in sarcoplasmic reticulum. J Biol Chem 2013; 288:30181-30191. [PMID: 23996003 DOI: 10.1074/jbc.m113.501585] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
P-type ATPases are a large family of enzymes that actively transport ions across biological membranes by interconverting between high (E1) and low (E2) ion-affinity states; these transmembrane transporters carry out critical processes in nearly all forms of life. In striated muscle, the archetype P-type ATPase, SERCA (sarco(endo)plasmic reticulum Ca(2+)-ATPase), pumps contractile-dependent Ca(2+) ions into the lumen of sarcoplasmic reticulum, which initiates myocyte relaxation and refills the sarcoplasmic reticulum in preparation for the next contraction. In cardiac muscle, SERCA is regulated by phospholamban (PLB), a small inhibitory phosphoprotein that decreases the Ca(2+) affinity of SERCA and attenuates contractile strength. cAMP-dependent phosphorylation of PLB reverses Ca(2+)-ATPase inhibition with powerful contractile effects. Here we present the long sought crystal structure of the PLB-SERCA complex at 2.8-Å resolution. The structure was solved in the absence of Ca(2+) in a novel detergent system employing alkyl mannosides. The structure shows PLB bound to a previously undescribed conformation of SERCA in which the Ca(2+) binding sites are collapsed and devoid of divalent cations (E2-PLB). This new structure represents one of the key unsolved conformational states of SERCA and provides a structural explanation for how dephosphorylated PLB decreases Ca(2+) affinity and depresses cardiac contractility.
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Affiliation(s)
- Brandy L Akin
- From the Krannert Institute of Cardiology and the Departments of Medicine and.
| | - Thomas D Hurley
- Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Zhenhui Chen
- From the Krannert Institute of Cardiology and the Departments of Medicine and
| | - Larry R Jones
- From the Krannert Institute of Cardiology and the Departments of Medicine and.
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14
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Leunissen EHP, Nair AV, Büll C, Lefeber DJ, van Delft FL, Bindels RJM, Hoenderop JGJ. The epithelial calcium channel TRPV5 is regulated differentially by klotho and sialidase. J Biol Chem 2013; 288:29238-46. [PMID: 23970553 DOI: 10.1074/jbc.m113.473520] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The transient receptor potential vanilloid type 5 (TRPV5) Ca(2+) channel facilitates transcellular Ca(2+) transport in the distal convoluted tubule (DCT) of the kidney. The channel is glycosylated with a complex type N-glycan and it has been postulated that hydrolysis of the terminal sialic acid(s) stimulate TRPV5 activity. The present study delineates the role of the N-glycan in TRPV5 activity using biochemical assays in Human Embryonic Kidney 293 cells expressing TRPV5, isoelectric focusing and total internal reflection fluorescent microscopy. The anti-aging hormone klotho and other glycosidases stimulate TRPV5-dependent Ca(2+) uptake. Klotho was found to increase the plasma membrane stability of TRPV5, via the TRPV5 N-glycan. Sialidase mimicked this stimulatory action. However, this effect was independent of the N-glycosylation state of TRPV5, since the N-glycosylation mutant (TRPV5(N358Q)) was activated to the same extent. We showed that the increased TRPV5 activity after sialidase treatment is caused by inhibition of lipid raft-mediated internalization. In addition, sialidase modified the N-glycan of transferrin, a model glycoprotein, differently from klotho. Previous studies showed that after klotho treatment, galectin-1 binds the TRPV5 N-glycan and thereby increases TRPV5 activity. However, galectin-3, but not galectin-1, was expressed in the DCT. Furthermore, an increase in TRPV5-mediated Ca(2+) uptake was detected after galectin-3 treatment. In conclusion, two distinct TRPV5 stimulatory mechanisms were demonstrated; a klotho-mediated effect that is dependent on the N-glycan of TRPV5 and a sialidase-mediated stimulation that is lipid raft-dependent and independent of the N-glycan of TRPV5.
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15
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Sasser TL, Lawrence G, Karunakaran S, Brown C, Fratti RA. The yeast ATP-binding cassette (ABC) transporter Ycf1p enhances the recruitment of the soluble SNARE Vam7p to vacuoles for efficient membrane fusion. J Biol Chem 2013; 288:18300-10. [PMID: 23658021 DOI: 10.1074/jbc.m112.441089] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The Saccharomyces cerevisiae vacuole contains five ATP-binding cassette class C (ABCC) transporters, including Ycf1p, a family member that was originally characterized as a Cd(2+) transporter. Ycf1p has also been found to physically interact with a wide array of proteins, including factors that regulate vacuole homeostasis. In this study, we examined the role of Ycf1p and other ABCC transporters in the regulation of vacuole homotypic fusion. We found that deletion of YCF1 attenuated in vitro vacuole fusion by up to 40% relative to wild-type vacuoles. Plasmid-expressed wild-type Ycf1p rescued the deletion phenotype; however, Ycf1p containing a mutation of the conserved Lys-669 to Met in the Walker A box of the first nucleotide-binding domain (Ycf1p(K669M)) was unable to complement the fusion defect of ycf1Δ vacuoles. This indicates that the ATPase activity of Ycf1p is required for its function in regulating fusion. In addition, we found that deleting YCF1 caused a striking decrease in vacuolar levels of the soluble SNARE Vam7p, whereas total cellular levels were not altered. The attenuated fusion of ycf1Δ vacuoles was rescued by the addition of recombinant Vam7p to in vitro experiments. Thus, Ycf1p contributes in the recruitment of Vam7p to the vacuole for efficient membrane fusion.
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Affiliation(s)
- Terry L Sasser
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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16
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Waldeck-Weiermair M, Deak AT, Groschner LN, Alam MR, Jean-Quartier C, Malli R, Graier WF. Molecularly distinct routes of mitochondrial Ca2+ uptake are activated depending on the activity of the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA). J Biol Chem 2013; 288:15367-79. [PMID: 23592775 PMCID: PMC3663555 DOI: 10.1074/jbc.m113.462259] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The transfer of Ca2+ across the inner mitochondrial membrane is an important physiological process linked to the regulation of metabolism, signal transduction, and cell death. While the definite molecular composition of mitochondrial Ca2+ uptake sites remains unknown, several proteins of the inner mitochondrial membrane, that are likely to accomplish mitochondrial Ca2+ fluxes, have been described: the novel uncoupling proteins 2 and 3, the leucine zipper-EF-hand containing transmembrane protein 1 and the mitochondrial calcium uniporter. It is unclear whether these proteins contribute to one unique mitochondrial Ca2+ uptake pathway or establish distinct routes for mitochondrial Ca2+ sequestration. In this study, we show that a modulation of Ca2+ release from the endoplasmic reticulum by inhibition of the sarco/endoplasmatic reticulum ATPase modifies cytosolic Ca2+ signals and consequently switches mitochondrial Ca2+ uptake from an uncoupling protein 3- and mitochondrial calcium uniporter-dependent, but leucine zipper-EF-hand containing transmembrane protein 1-independent to a leucine zipper-EF-hand containing transmembrane protein 1- and mitochondrial calcium uniporter-mediated, but uncoupling protein 3-independent pathway. Thus, the activity of sarco/endoplasmatic reticulum ATPase is significant for the mode of mitochondrial Ca2+ sequestration and determines which mitochondrial proteins might actually accomplish the transfer of Ca2+ across the inner mitochondrial membrane. Moreover, our findings herein support the existence of distinct mitochondrial Ca2+ uptake routes that might be essential to ensure an efficient ion transfer into mitochondria despite heterogeneous cytosolic Ca2+ rises.
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Affiliation(s)
- Markus Waldeck-Weiermair
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, 8010 Graz, Austria
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Alvares K, Stern PH, Veis A. Dentin phosphoprotein binds annexin 2 and is involved in calcium transport in rat kidney ureteric bud cells. J Biol Chem 2013; 288:13036-45. [PMID: 23525114 DOI: 10.1074/jbc.m112.389627] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dentin phosphoprotein (DPP) is the most abundant noncollagenous protein in the dentin, where it plays a major role in the mineralization of dentin. However, we and others have shown that in addition to being present in the dentin, DPP is also present in nonmineralizing tissues like the kidney, lung, and salivary glands, where it conceivably has other functions such as in calcium transport. Because annexins have been implicated as calcium transporters, we examined the relationships between DPP and annexins. In this report, we show that DPP binds to annexin 2 and 6 present in a rat ureteric bud cell line (RUB1). Immunofluorescence studies show that annexin 2 and DPP colocalize in these cells. In addition, DPP and annexin 2 colocalize in the ureteric bud branches of embryonic metanephric kidney. In the RUB1 cells and ureteric bud branches of embryonic kidney, colocalization was restricted to the cell membrane. Studies on calcium influx into RUB cells show that in the presence of anti-DPP, there was a 40% reduction of calcium influx into these cells. We postulate that DPP has different functions in the kidney as compared with the odontoblasts. In the odontoblasts, its primary function is in the extracellular mineralization of dentin, whereas in the kidney it may participate in calcium transport.
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Affiliation(s)
- Keith Alvares
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
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