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Capasso L, Ganot P, Planas-Bielsa V, Tambutté S, Zoccola D. Intracellular pH regulation: characterization and functional investigation of H + transporters in Stylophora pistillata. BMC Mol Cell Biol 2021; 22:18. [PMID: 33685406 PMCID: PMC7941709 DOI: 10.1186/s12860-021-00353-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 02/22/2021] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Reef-building corals regularly experience changes in intra- and extracellular H+ concentrations ([H+]) due to physiological and environmental processes. Stringent control of [H+] is required to maintain the homeostatic acid-base balance in coral cells and is achieved through the regulation of intracellular pH (pHi). This task is especially challenging for reef-building corals that share an endosymbiotic relationship with photosynthetic dinoflagellates (family Symbiodinaceae), which significantly affect the pHi of coral cells. Despite their importance, the pH regulatory proteins involved in the homeostatic acid-base balance have been scarcely investigated in corals. Here, we report in the coral Stylophora pistillata a full characterization of the genomic structure, domain topology and phylogeny of three major H+ transporter families that are known to play a role in the intracellular pH regulation of animal cells; we investigated their tissue-specific expression patterns and assessed the effect of seawater acidification on their expression levels. RESULTS We identified members of the Na+/H+ exchanger (SLC9), vacuolar-type electrogenic H+-ATP hydrolase (V-ATPase) and voltage-gated proton channel (HvCN) families in the genome and transcriptome of S. pistillata. In addition, we identified a novel member of the HvCN gene family in the cnidarian subclass Hexacorallia that has not been previously described in any species. We also identified key residues that contribute to H+ transporter substrate specificity, protein function and regulation. Last, we demonstrated that some of these proteins have different tissue expression patterns, and most are unaffected by exposure to seawater acidification. CONCLUSIONS In this study, we provide the first characterization of H+ transporters that might contribute to the homeostatic acid-base balance in coral cells. This work will enrich the knowledge of the basic aspects of coral biology and has important implications for our understanding of how corals regulate their intracellular environment.
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Affiliation(s)
- Laura Capasso
- Centre Scientifique de Monaco, 8 quai Antoine 1er, 98000, Monaco, Monaco.,Sorbonne Université, Collège Doctoral, F-75005, Paris, France
| | - Philippe Ganot
- Centre Scientifique de Monaco, 8 quai Antoine 1er, 98000, Monaco, Monaco
| | | | - Sylvie Tambutté
- Centre Scientifique de Monaco, 8 quai Antoine 1er, 98000, Monaco, Monaco
| | - Didier Zoccola
- Centre Scientifique de Monaco, 8 quai Antoine 1er, 98000, Monaco, Monaco.
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2
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Calisto F, Sousa FM, Sena FV, Refojo PN, Pereira MM. Mechanisms of Energy Transduction by Charge Translocating Membrane Proteins. Chem Rev 2021; 121:1804-1844. [PMID: 33398986 DOI: 10.1021/acs.chemrev.0c00830] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Life relies on the constant exchange of different forms of energy, i.e., on energy transduction. Therefore, organisms have evolved in a way to be able to harvest the energy made available by external sources (such as light or chemical compounds) and convert these into biological useable energy forms, such as the transmembrane difference of electrochemical potential (Δμ̃). Membrane proteins contribute to the establishment of Δμ̃ by coupling exergonic catalytic reactions to the translocation of charges (electrons/ions) across the membrane. Irrespectively of the energy source and consequent type of reaction, all charge-translocating proteins follow two molecular coupling mechanisms: direct- or indirect-coupling, depending on whether the translocated charge is involved in the driving reaction. In this review, we explore these two coupling mechanisms by thoroughly examining the different types of charge-translocating membrane proteins. For each protein, we analyze the respective reaction thermodynamics, electron transfer/catalytic processes, charge-translocating pathways, and ion/substrate stoichiometries.
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Affiliation(s)
- Filipa Calisto
- Instituto de Tecnologia Química e Biológica-António Xavier, Universidade Nova de Lisboa, Av. da República EAN, 2780-157, Oeiras, Portugal.,BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Faculty of Sciences, Campo Grande, 1749-016 Lisboa, Portugal
| | - Filipe M Sousa
- Instituto de Tecnologia Química e Biológica-António Xavier, Universidade Nova de Lisboa, Av. da República EAN, 2780-157, Oeiras, Portugal.,BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Faculty of Sciences, Campo Grande, 1749-016 Lisboa, Portugal
| | - Filipa V Sena
- Instituto de Tecnologia Química e Biológica-António Xavier, Universidade Nova de Lisboa, Av. da República EAN, 2780-157, Oeiras, Portugal.,BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Faculty of Sciences, Campo Grande, 1749-016 Lisboa, Portugal
| | - Patricia N Refojo
- Instituto de Tecnologia Química e Biológica-António Xavier, Universidade Nova de Lisboa, Av. da República EAN, 2780-157, Oeiras, Portugal
| | - Manuela M Pereira
- Instituto de Tecnologia Química e Biológica-António Xavier, Universidade Nova de Lisboa, Av. da República EAN, 2780-157, Oeiras, Portugal.,BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Faculty of Sciences, Campo Grande, 1749-016 Lisboa, Portugal
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3
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Chen J, Sitsel A, Benoy V, Sepúlveda MR, Vangheluwe P. Primary Active Ca 2+ Transport Systems in Health and Disease. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a035113. [PMID: 31501194 DOI: 10.1101/cshperspect.a035113] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Calcium ions (Ca2+) are prominent cell signaling effectors that regulate a wide variety of cellular processes. Among the different players in Ca2+ homeostasis, primary active Ca2+ transporters are responsible for keeping low basal Ca2+ levels in the cytosol while establishing steep Ca2+ gradients across intracellular membranes or the plasma membrane. This review summarizes our current knowledge on the three types of primary active Ca2+-ATPases: the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) pumps, the secretory pathway Ca2+- ATPase (SPCA) isoforms, and the plasma membrane Ca2+-ATPase (PMCA) Ca2+-transporters. We first discuss the Ca2+ transport mechanism of SERCA1a, which serves as a reference to describe the Ca2+ transport of other Ca2+ pumps. We further highlight the common and unique features of each isoform and review their structure-function relationship, expression pattern, regulatory mechanisms, and specific physiological roles. Finally, we discuss the increasing genetic and in vivo evidence that links the dysfunction of specific Ca2+-ATPase isoforms to a broad range of human pathologies, and highlight emerging therapeutic strategies that target Ca2+ pumps.
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Affiliation(s)
- Jialin Chen
- Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium
| | - Aljona Sitsel
- Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium
| | - Veronick Benoy
- Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium
| | - M Rosario Sepúlveda
- Department of Cell Biology, Faculty of Sciences, University of Granada, 18071 Granada, Spain
| | - Peter Vangheluwe
- Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium
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4
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Britzolaki A, Saurine J, Klocke B, Pitychoutis PM. A Role for SERCA Pumps in the Neurobiology of Neuropsychiatric and Neurodegenerative Disorders. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:131-161. [PMID: 31646509 DOI: 10.1007/978-3-030-12457-1_6] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Calcium (Ca2+) is a fundamental regulator of cell fate and intracellular Ca2+ homeostasis is crucial for proper function of the nerve cells. Given the complexity of neurons, a constellation of mechanisms finely tunes the intracellular Ca2+ signaling. We are focusing on the sarco/endoplasmic reticulum (SR/ER) calcium (Ca2+)-ATPase (SERCA) pump, an integral ER protein. SERCA's well established role is to preserve low cytosolic Ca2+ levels ([Ca2+]cyt), by pumping free Ca2+ ions into the ER lumen, utilizing ATP hydrolysis. The SERCA pumps are encoded by three distinct genes, SERCA1-3, resulting in 12 known protein isoforms, with tissue-dependent expression patterns. Despite the well-established structure and function of the SERCA pumps, their role in the central nervous system is not clear yet. Interestingly, SERCA-mediated Ca2+ dyshomeostasis has been associated with neuropathological conditions, such as bipolar disorder, schizophrenia, Parkinson's disease and Alzheimer's disease. We summarize here current evidence suggesting a role for SERCA in the neurobiology of neuropsychiatric and neurodegenerative disorders, thus highlighting the importance of this pump in brain physiology and pathophysiology.
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Affiliation(s)
- Aikaterini Britzolaki
- Department of Biology & Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, Dayton, OH, USA
| | - Joseph Saurine
- Department of Biology & Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, Dayton, OH, USA
| | - Benjamin Klocke
- Department of Biology & Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, Dayton, OH, USA
| | - Pothitos M Pitychoutis
- Department of Biology & Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, Dayton, OH, USA.
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5
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Drake JL, Mass T, Stolarski J, Von Euw S, van de Schootbrugge B, Falkowski PG. How corals made rocks through the ages. GLOBAL CHANGE BIOLOGY 2020; 26:31-53. [PMID: 31696576 PMCID: PMC6942544 DOI: 10.1111/gcb.14912] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 10/28/2019] [Accepted: 10/30/2019] [Indexed: 05/03/2023]
Abstract
Hard, or stony, corals make rocks that can, on geological time scales, lead to the formation of massive reefs in shallow tropical and subtropical seas. In both historical and contemporary oceans, reef-building corals retain information about the marine environment in their skeletons, which is an organic-inorganic composite material. The elemental and isotopic composition of their skeletons is frequently used to reconstruct the environmental history of Earth's oceans over time, including temperature, pH, and salinity. Interpretation of this information requires knowledge of how the organisms formed their skeletons. The basic mechanism of formation of calcium carbonate skeleton in stony corals has been studied for decades. While some researchers consider coral skeletons as mainly passive recorders of ocean conditions, it has become increasingly clear that biological processes play key roles in the biomineralization mechanism. Understanding the role of the animal in living stony coral biomineralization and how it evolved has profound implications for interpreting environmental signatures in fossil corals to understand past ocean conditions. Here we review historical hypotheses and discuss the present understanding of how corals evolved and how their skeletons changed over geological time. We specifically explain how biological processes, particularly those occurring at the subcellular level, critically control the formation of calcium carbonate structures. We examine the different models that address the current debate including the tissue-skeleton interface, skeletal organic matrix, and biomineralization pathways. Finally, we consider how understanding the biological control of coral biomineralization is critical to informing future models of coral vulnerability to inevitable global change, particularly increasing ocean acidification.
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Affiliation(s)
- Jeana L Drake
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA
| | - Tali Mass
- Department of Marine Biology, The Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel
| | | | - Stanislas Von Euw
- Trinity Centre for Bioengineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | | | - Paul G Falkowski
- Department of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ, USA
- Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ, USA
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6
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Carbone E, Borges R, Eiden LE, García AG, Hernández‐Cruz A. Chromaffin Cells of the Adrenal Medulla: Physiology, Pharmacology, and Disease. Compr Physiol 2019; 9:1443-1502. [DOI: 10.1002/cphy.c190003] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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7
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Britzolaki A, Saurine J, Flaherty E, Thelen C, Pitychoutis PM. The SERCA2: A Gatekeeper of Neuronal Calcium Homeostasis in the Brain. Cell Mol Neurobiol 2018; 38:981-994. [PMID: 29663107 DOI: 10.1007/s10571-018-0583-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 04/03/2018] [Indexed: 12/16/2022]
Abstract
Calcium (Ca2+) ions are prominent cell signaling regulators that carry information for a variety of cellular processes and are critical for neuronal survival and function. Furthermore, Ca2+ acts as a prominent second messenger that modulates divergent intracellular cascades in the nerve cells. Therefore, nerve cells have developed intricate Ca2+ signaling pathways to couple the Ca2+ signal to their biochemical machinery. Notably, intracellular Ca2+ homeostasis greatly relies on the rapid redistribution of Ca2+ ions into the diverse subcellular organelles which serve as Ca2+ stores, including the endoplasmic reticulum (ER). It is well established that Ca2+ released into the neuronal cytoplasm is pumped back into the ER by the sarco-/ER Ca2+ ATPase 2 (SERCA2), a P-type ion-motive ATPase that resides on the ER membrane. Even though the SERCA2 is constitutively expressed in nerve cells, its precise role in brain physiology and pathophysiology is not well-characterized. Intriguingly, SERCA2-dependent Ca2+ dysregulation has been implicated in several disorders that affect cognitive function, including Darier's disease, schizophrenia, Alzheimer's disease, and cerebral ischemia. The current review summarizes knowledge on the expression pattern of the different SERCA2 isoforms in the nervous system, and further discusses evidence of SERCA2 dysregulation in various neuropsychiatric disorders. To the best of our knowledge, this is the first literature review that specifically highlights the critical role of the SERCA2 in the brain. Advancing knowledge on the role of SERCA2 in maintaining neuronal Ca2+ homeostasis may ultimately lead to the development of safer and more effective pharmacotherapies to combat debilitating neuropsychiatric disorders.
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Affiliation(s)
- Aikaterini Britzolaki
- Department of Biology & Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, 300 College Park, Dayton, OH, 45469-2320, USA
| | - Joseph Saurine
- Department of Biology & Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, 300 College Park, Dayton, OH, 45469-2320, USA
| | - Emily Flaherty
- Department of Biology & Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, 300 College Park, Dayton, OH, 45469-2320, USA
| | - Connor Thelen
- Department of Biology & Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, 300 College Park, Dayton, OH, 45469-2320, USA
| | - Pothitos M Pitychoutis
- Department of Biology & Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, 300 College Park, Dayton, OH, 45469-2320, USA.
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8
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Hiong KC, Cao-Pham AH, Choo CYL, Boo MV, Wong WP, Chew SF, Ip YK. Light-dependent expression of a Na +/H + exchanger 3-like transporter in the ctenidium of the giant clam, Tridacna squamosa, can be related to increased H + excretion during light-enhanced calcification. Physiol Rep 2018; 5:5/8/e13209. [PMID: 28438983 PMCID: PMC5408280 DOI: 10.14814/phy2.13209] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Accepted: 02/22/2017] [Indexed: 12/03/2022] Open
Abstract
Na+/H+ exchangers (NHEs) regulate intracellular pH and ionic balance by mediating H+ efflux in exchange for Na+ uptake in a 1:1 stoichiometry. This study aimed to obtain from the ctenidium of the giant clam Tridacna squamosa (TS) the complete cDNA sequence of a NHE3‐like transporter (TSNHE3), and to determine the effect of light exposure on its mRNA expression level and protein abundance therein. The coding sequence of TSNHE3 comprised 2886 bp, encoding 961 amino acids with an estimated molecular mass of 105.7 kDa. Immunofluorescence microscopy revealed that TSNHE3 was localized to the apical membrane of epithelial cells of the ctenidial filaments and the tertiary water channels. Particularly, the apical immunofluorescence of the ctenidial filaments was consistently stronger in the ctenidium of clams exposed to 12 h of light than those of the control kept in darkness. Indeed, light induced significant increases in the transcript level and protein abundance of TSNHE3/TSNHE3 in the ctenidium, indicating that the transcription and translation of TSNHE3/TSNHE3 were light‐dependent. As light‐enhanced calcification generates H+, the increased expression of TSNHE3/TSNHE3 in the ctenidium could be a response to augment H+ excretion in pursuance of whole‐body acid‐base balance during light exposure. These results signify that shell formation in giant clams requires the collaboration between the ctenidium, which is a respiratory and iono‐regulatory organ, and the inner mantle, which is directly involved in the calcification process, and provide new insights into the mechanisms of light‐enhanced calcification in giant clams.
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Affiliation(s)
- Kum C Hiong
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore
| | - Anh H Cao-Pham
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore
| | - Celine Y L Choo
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore
| | - Mel V Boo
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore
| | - Wai P Wong
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore
| | - Shit F Chew
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Nanyang Walk, Singapore
| | - Yuen K Ip
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore .,The Tropical Marine Science Institute, National University of Singapore, Kent Ridge, Singapore
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9
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Ip YK, Hiong KC, Goh EJK, Boo MV, Choo CYL, Ching B, Wong WP, Chew SF. The Whitish Inner Mantle of the Giant Clam, Tridacna squamosa, Expresses an Apical Plasma Membrane Ca 2+-ATPase (PMCA) Which Displays Light-Dependent Gene and Protein Expressions. Front Physiol 2017; 8:781. [PMID: 29066980 PMCID: PMC5641333 DOI: 10.3389/fphys.2017.00781] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 09/25/2017] [Indexed: 12/16/2022] Open
Abstract
Giant clams live in symbiosis with extracellular zooxanthellae and display high rates of growth and shell formation (calcification) in light. Light-enhanced calcification requires an increase in the supply of Ca2+ to, and simultaneously an augmented removal of H+ from, the extrapallial fluid where shell formation occurs. We have obtained the complete coding cDNA sequence of Plasma Membrane Ca2+-ATPase (PMCA) from the thin and whitish inner mantle, which is in touch with the extrapallial fluid, of the giant clam Tridacna squamosa. The deduced PMCA sequence consisted of an apical targeting element. Immunofluorescence microscopy confirmed that PMCA had an apical localization in the shell-facing epithelium of the inner mantle, whereby it can actively secrete Ca2+ in exchange for H+. More importantly, the apical PMCA-immunofluorescence of the shell-facing epithelium of the inner mantle increased significantly after 12 h of exposure to light. The transcript and protein levels of PMCA/PMCA also increased significantly in the inner mantle after 6 or 12 h of light exposure. These results offer insights into a light-dependable mechanism of shell formation in T. squamosa and a novel explanation of light-enhanced calcification in general. As the inner mantle normally lacks light sensitive pigments, our results support a previous proposition that symbiotic zooxanthellae, particularly those in the colorful and extensible outer mantle, may act as light-sensing elements for the host clam.
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Affiliation(s)
- Yuen K Ip
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore.,The Tropical Marine Science Institute, National University of Singapore, Singapore, Singapore
| | - Kum C Hiong
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Enan J K Goh
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Mel V Boo
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Celine Y L Choo
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Biyun Ching
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Wai P Wong
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Shit F Chew
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore, Singapore
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10
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Berrocal M, Corbacho I, Sepulveda MR, Gutierrez-Merino C, Mata AM. Phospholipids and calmodulin modulate the inhibition of PMCA activity by tau. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1864:1028-1035. [PMID: 27818274 DOI: 10.1016/j.bbamcr.2016.10.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 10/26/2016] [Accepted: 10/27/2016] [Indexed: 12/18/2022]
Abstract
The disruption of Ca2+ signaling in neurons, together with a failure to keep optimal intracellular Ca2+ concentrations, have been proposed as significant factors for neuronal dysfunction in the Ca2+ hypothesis of Alzheimer's disease (AD). Tau is a protein that plays an essential role in axonal transport and can form abnormal structures such as neurofibrillary tangles that constitute one of the hallmarks of AD. We have recently shown that plasma membrane Ca2+-ATPase (PMCA), a key enzyme in the maintenance of optimal cytosolic Ca2+ levels in cells, is inhibited by tau in membrane vesicles. In the present study we show that tau inhibits synaptosomal PMCA purified from pig cerebrum, and reconstituted in phosphatidylserine-containing lipid bilayers, with a Ki value of 1.5±0.2nM tau. Noteworthy, the inhibitory effect of tau is dependent on the charge of the phospholipid used for PMCA reconstitution. In addition, nanomolar concentrations of calmodulin, the major endogenous activator of PMCA, protects against inhibition of the Ca2+-ATPase activity by tau. Our results in a cellular model such as SH-SY5Y human neuroblastoma cells yielded an inhibition of PMCA by nanomolar tau concentrations and protection by calmodulin against this inhibition similar to those obtained with purified synaptosomal PMCA. Functional studies were also performed with native and truncated versions of human cerebral PMCA4b, an isoform that has been showed to be functionally regulated by amyloid peptides, whose aggregates constitutes another hallmark of AD. Kinetic assays point out that tau binds to the C-terminal tail of PMCA, at a site distinct but close to the calmodulin binding domain. In conclusion, PMCA can be seen as a molecular target for tau-induced cytosolic calcium dysregulation in synaptic terminals. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.
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Affiliation(s)
- María Berrocal
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain
| | - Isaac Corbacho
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain
| | - M Rosario Sepulveda
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain
| | - Carlos Gutierrez-Merino
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain
| | - Ana M Mata
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06006 Badajoz, Spain.
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11
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Sitsel O, Grønberg C, Autzen HE, Wang K, Meloni G, Nissen P, Gourdon P. Structure and Function of Cu(I)- and Zn(II)-ATPases. Biochemistry 2015; 54:5673-83. [PMID: 26132333 DOI: 10.1021/acs.biochem.5b00512] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Copper and zinc are micronutrients essential for the function of many enzymes while also being toxic at elevated concentrations. Cu(I)- and Zn(II)-transporting P-type ATPases of subclass 1B are of key importance for the homeostasis of these transition metals, allowing ion transport across cellular membranes at the expense of ATP. Recent biochemical studies and crystal structures have significantly improved our understanding of the transport mechanisms of these proteins, but many details about their structure and function remain elusive. Here we compare the Cu(I)- and Zn(II)-ATPases, scrutinizing the molecular differences that allow transport of these two distinct metal types, and discuss possible future directions of research in the field.
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Affiliation(s)
- Oleg Sitsel
- Centre for Membrane Pumps in Cells and Disease (PUMPkin), Danish National Research Foundation, Department of Molecular Biology and Genetics, Aarhus University , Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark
| | - Christina Grønberg
- Department of Biomedical Sciences, University of Copenhagen , Blegdamsvej 3B, DK-2200 Copenhagen, Denmark
| | - Henriette Elisabeth Autzen
- Department of Biomedical Sciences, University of Copenhagen , Blegdamsvej 3B, DK-2200 Copenhagen, Denmark
| | - Kaituo Wang
- Department of Biomedical Sciences, University of Copenhagen , Blegdamsvej 3B, DK-2200 Copenhagen, Denmark
| | - Gabriele Meloni
- Division of Chemistry and Chemical Engineering and Howard Hughes Medical Institute, California Institute of Technology , Pasadena, California 91125, United States
| | - Poul Nissen
- Centre for Membrane Pumps in Cells and Disease (PUMPkin), Danish National Research Foundation, Department of Molecular Biology and Genetics, Aarhus University , Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark
| | - Pontus Gourdon
- Department of Biomedical Sciences, University of Copenhagen , Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.,Department of Experimental Medical Science, Lund University , Sölvegatan 19, SE-221 84 Lund, Sweden
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12
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Surin AM, Gorbacheva LR, Savinkova IG, Sharipov RR, Khodorov BI, Pinelis VG. Study on ATP concentration changes in cytosol of individual cultured neurons during glutamate-induced deregulation of calcium homeostasis. BIOCHEMISTRY (MOSCOW) 2015; 79:146-57. [PMID: 24794730 DOI: 10.1134/s0006297914020084] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
For the first time, simultaneous monitoring of changes in the concentration of cytosolic ATP ([ATP]c), pH (pHc), and intracellular free Ca2+ concentration ([Ca2+]i) of the individual neurons challenged with toxic glutamate (Glu) concentrations was performed. To this end, the ATP-sensor AT1.03, which binds to ATP and therefore enhances the efficiency of resonance energy transfer between blue fluorescent protein (energy donor) and yellow-green fluorescent protein (energy acceptor), was expressed in cultured hippocampal neurons isolated from 1-2-day-old rat pups. Excitation of fluorescence in the acceptor protein allowed monitoring changes in pHc. Cells were loaded with fluorescent low-affinity Ca2+ indicators Fura-FF or X-rhod-FF to register [Ca2+]i. It was shown that Glu (20 µM, glycine 10 µM, Mg2+-free) produced a rapid acidification of the cytosol and decrease in [ATP]c. An approximately linear relationship (r(2) = 0.56) between the rate of [ATP]c decline and latency of glutamate-induced delayed calcium deregulation (DCD) was observed: higher rate of [ATP]c decrease corresponded to shorter DCD latency period. DCD began with a decrease in [ATP]c of as much as 15.9%. In the phase of high [Ca2+]i, the plateau of [ATP]c dropped to 10.4% compared to [ATP]c in resting neurons (100%). In the presence of the Na+/K+-ATPase inhibitor ouabain (0.5 mM), glutamate-induced reduction in [ATP]c in the phase of the high [Ca2+]i plateau was only 36.6%. Changes in [ATP]c, [Ca2+]i, mitochondrial potential, and pHc in calcium-free or sodium-free buffers, as well as in the presence of the inhibitor of Na+/K+-ATPase ouabain (0.5 mM), led us to suggest that in addition to increase in proton conductivity and decline in [ATP]c, one of the triggering factors of DCD might be a reversion of the neuronal plasma membrane Na+/Ca2+ exchange.
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Affiliation(s)
- A M Surin
- Institute of General Pathology and Pathophysiology, Russian Academy of Medical Sciences, Moscow, 125315, Russia.
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Peralta-Arias RD, Vívenes CY, Camejo MI, Piñero S, Proverbio T, Martínez E, Marín R, Proverbio F. ATPases, ion exchangers and human sperm motility. Reproduction 2015; 149:475-84. [DOI: 10.1530/rep-14-0471] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Human sperm has several mechanisms to control its ionic milieu, such as the Na,K-ATPase (NKA), the Ca-ATPase of the plasma membrane (PMCA), the Na+/Ca2+-exchanger (NCX) and the Na+/H+-exchanger (NHE). On the other hand, the dynein-ATPase is the intracellular motor for sperm motility. In this work, we evaluated NKA, PMCA, NHE, NCX and dynein-ATPase activities in human sperm and investigated their correlation with sperm motility. Sperm motility was measured by Computer Assisted Semen Analysis. It was found that the NKA activity is inhibited by ouabain with twoKi(7.9×10−9and 9.8×10−5 M), which is consistent with the presence of two isoforms of α subunit of the NKA in the sperm plasma membranes (α1 and α4), being α4 more sensitive to ouabain. The decrease in NKA activity is associated with a reduction in sperm motility. In addition, sperm motility was evaluated in the presence of known inhibitors of NHE, PMCA and NCX, such as amiloride, eosin, and KB-R7943, respectively, as well as in the presence of nigericin after incubation with ouabain. Amiloride, eosin and KB-R7943 significantly reduced sperm motility. Nigericin reversed the effect of ouabain and amiloride on sperm motility. Dynein-ATPase activity was inhibited by acidic pH and micromolar concentrations of Ca2+. We explain our results in terms of inhibition of the dynein-ATPase in the presence of higher cytosolic H+and Ca2+, and therefore inhibition of sperm motility.
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Cytosolic calcium regulation in rat afferent vagal neurons during anoxia. Cell Calcium 2013; 54:416-27. [PMID: 24189167 DOI: 10.1016/j.ceca.2013.10.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2013] [Revised: 09/30/2013] [Accepted: 10/06/2013] [Indexed: 12/12/2022]
Abstract
Sensory neurons are able to detect tissue ischaemia and both transmit information to the brainstem as well as release local vasoactive mediators. Their ability to sense tissue ischaemia is assumed to be primarily mediated through proton sensing ion channels, lack of oxygen however may also affect sensory neuron function. In this study we investigated the effects of anoxia on isolated capsaicin sensitive neurons from rat nodose ganglion. Acute anoxia triggered a reversible increase in [Ca2+]i that was mainly due to Ca2+-efflux from FCCP sensitive stores and from caffeine and CPA sensitive ER stores. Prolonged anoxia resulted in complete depletion of ER Ca2+-stores. Mitochondria were partially depolarised by acute anoxia but mitochondrial Ca2+-uptake/buffering during voltage-gated Ca2+-influx was unaffected. The process of Ca2+-release from mitochondria and cytosolic Ca2+-clearance following Ca2+ influx was however significantly slowed. Anoxia was also found to inhibit SERCA activity and, to a lesser extent, PMCA activity. Hence, anoxia has multiple influences on [Ca2+]i homeostasis in vagal afferent neurons, including depression of ATP-driven Ca2+-pumps, modulation of the kinetics of mitochondrial Ca2+ buffering/release and Ca2+-release from, and depletion of, internal Ca2+-stores. These effects are likely to influence sensory neuronal function during ischaemia.
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15
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Hong S, Cong X, Jing H, Xia Z, Huang X, Hu X, Jiang X. Characterization of Ca(2+)/H(+) exchange in the plasma membrane of Saccharomyces cerevisiae. Arch Biochem Biophys 2013; 537:125-32. [PMID: 23871844 DOI: 10.1016/j.abb.2013.07.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Revised: 06/26/2013] [Accepted: 07/09/2013] [Indexed: 11/17/2022]
Abstract
The characteristics of the Ca(2+)/H(+) exchange were directly investigated in functionally inverted (inside-out) plasma membrane vesicles isolated from yeast using an aqueous two-phase partitioning method. Results showed that following the generation of an inside-acid pH gradient (fluorescence quenching), addition of Ca(2+) caused movement of H(+) out of the vesicles (fluorescence recovery). The Ca(2+)/H(+) exchange displayed saturation kinetics with respect to extravesicular Ca(2+) and ATP concentrations in the plasma membrane, and showed specificity for Ca(2+). The protonophore FCCP (carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone), abolished the fluorescence quenching and consequently inhibited Ca(2+)/H(+) exchange in plasma membrane vesicles. Vanadate, which is known to inhibit the plasma membrane H(+)-ATPase, significantly decreased the Ca(2+)-dependent transport of H(+) out of vesicles. When the electrical potential across the plasma membrane was dissipated with valinomycin and potassium, the rate of Ca(2+)/H(+) exchange increased compared to that of the control without valinomycin, indicating that the stoichiometric ratio for this exchange is greater than 2H(+):Ca(2+). These data suggest that Ca(2+) is transported out of yeast cells through a Ca(2+)/H(+) exchange system that is driven by the proton-motive force generated by the plasma membrane H(+)-ATPase.
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Affiliation(s)
- Sha Hong
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources/College of Agriculture, Hainan University, Haikou, China
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16
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Thøgersen L, Nissen P. Flexible P-type ATPases interacting with the membrane. Curr Opin Struct Biol 2012; 22:491-9. [PMID: 22749193 DOI: 10.1016/j.sbi.2012.05.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 05/30/2012] [Accepted: 05/30/2012] [Indexed: 01/13/2023]
Abstract
Cation pumps and lipid flippases of the P-type ATPase family maintain electrochemical gradients and asymmetric lipid distributions across membranes, and offer significant insight of protein:membrane interactions. The sarcoplasmic reticulum Ca(2+)-ATPase features flexible and adaptive interactions with the surrounding membrane, while the Na(+),K(+)-ATPase complex is modulated by membrane components and a role for the γ-subunit as a stabilizer of a specific lipid interaction with the α-subunit has been proposed. The first crystal structure of a heavy-metal transporting ATPase shows a markedly amphipathic helix at the cytoplasmic membrane surface, highlighting this structure as a general motif of all P-type ATPases although with specialization to different membranes. Residues of central importance for the lipid flippase activity of the P4-type ATPase subfamily have been pinpointed by mutational studies, but the transport pathway and mechanism remain unknown.
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Affiliation(s)
- Lea Thøgersen
- Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Danish National Research Foundation, DK-8000 Aarhus C, Denmark
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17
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Cytosolic organelles shape calcium signals and exo–endocytotic responses of chromaffin cells. Cell Calcium 2012; 51:309-20. [DOI: 10.1016/j.ceca.2011.12.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 12/02/2011] [Accepted: 12/05/2011] [Indexed: 01/09/2023]
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18
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Jacoby J, Kreitzer MA, Alford S, Qian H, Tchernookova BK, Naylor ER, Malchow RP. Extracellular pH dynamics of retinal horizontal cells examined using electrochemical and fluorometric methods. J Neurophysiol 2011; 107:868-79. [PMID: 22090459 DOI: 10.1152/jn.00878.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Extracellular H(+) has been hypothesized to mediate feedback inhibition from horizontal cells onto vertebrate photoreceptors. According to this hypothesis, depolarization of horizontal cells should induce extracellular acidification adjacent to the cell membrane. Experiments testing this hypothesis have produced conflicting results. Studies examining carp and goldfish horizontal cells loaded with the pH-sensitive dye 5-hexadecanoylaminofluorescein (HAF) reported an extracellular acidification on depolarization by glutamate or potassium. However, investigations using H(+)-selective microelectrodes report an extracellular alkalinization on depolarization of skate and catfish horizontal cells. These studies differed in the species and extracellular pH buffer used and the presence or absence of cobalt. We used both techniques to examine H(+) changes from isolated catfish horizontal cells under identical experimental conditions (1 mM HEPES, no cobalt). HAF fluorescence indicated an acidification response to high extracellular potassium or glutamate. However, a clear extracellular alkalinization was found using H(+)-selective microelectrodes under the same conditions. Confocal microscopy revealed that HAF was not localized exclusively to the extracellular surface, but rather was detected throughout the intracellular compartment. A high degree of colocalization between HAF and the mitochondrion-specific dye MitoTracker was observed. When HAF fluorescence was monitored from optical sections from the center of a cell, glutamate produced an intracellular acidification. These results are consistent with a model in which depolarization allows calcium influx, followed by activation of a Ca(2+)/H(+) plasma membrane ATPase. Our results suggest that HAF is reporting intracellular pH changes and that depolarization of horizontal cells induces an extracellular alkalinization, which may relieve H(+)-mediated inhibition of photoreceptor synaptic transmission.
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Affiliation(s)
- Jason Jacoby
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
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Tulyakova E, Delbaere S, Fedorov Y, Jonusauskas G, Moiseeva A, Fedorova O. Multimodal Metal Cation Sensing with Bis(macrocyclic) Dye. Chemistry 2011; 17:10752-62. [DOI: 10.1002/chem.201100998] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Elena Tulyakova
- CNRS UMR 8516, Université Lille Nord de France, 3 rue du Professeur Laguesse BP83, 59006 Lille (France)
| | - Stephanie Delbaere
- CNRS UMR 8516, Université Lille Nord de France, 3 rue du Professeur Laguesse BP83, 59006 Lille (France)
| | - Yuri Fedorov
- A. N. Nesmeyanov Institute of Organoelement Compounds, 28 Vavilova street, 119991 Moscow (Russian Federation)
| | - Gedaminas Jonusauskas
- Laboratoire Ondes et Matière d'Aquitaine, Bordeaux University I, UMR CNRS 5798, 351 Cours de la Libiration, 33405 Talence (France)
| | - Anna Moiseeva
- Chemistry Department, M. V. Lomonosov Moscow State University, Lenin Hills 1/3, 119991 Moscow (Russian Federation)
| | - Olga Fedorova
- A. N. Nesmeyanov Institute of Organoelement Compounds, 28 Vavilova street, 119991 Moscow (Russian Federation)
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20
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Drion G, Massotte L, Sepulchre R, Seutin V. How modeling can reconcile apparently discrepant experimental results: the case of pacemaking in dopaminergic neurons. PLoS Comput Biol 2011; 7:e1002050. [PMID: 21637742 PMCID: PMC3102759 DOI: 10.1371/journal.pcbi.1002050] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 03/28/2011] [Indexed: 11/23/2022] Open
Abstract
Midbrain dopaminergic neurons are endowed with endogenous slow pacemaking properties. In recent years, many different groups have studied the basis for this phenomenon, often with conflicting conclusions. In particular, the role of a slowly-inactivating L-type calcium channel in the depolarizing phase between spikes is controversial, and the analysis of slow oscillatory potential (SOP) recordings during the blockade of sodium channels has led to conflicting conclusions. Based on a minimal model of a dopaminergic neuron, our analysis suggests that the same experimental protocol may lead to drastically different observations in almost identical neurons. For example, complete L-type calcium channel blockade eliminates spontaneous firing or has almost no effect in two neurons differing by less than 1% in their maximal sodium conductance. The same prediction can be reproduced in a state of the art detailed model of a dopaminergic neuron. Some of these predictions are confirmed experimentally using single-cell recordings in brain slices. Our minimal model exhibits SOPs when sodium channels are blocked, these SOPs being uncorrelated with the spiking activity, as has been shown experimentally. We also show that block of a specific conductance (in this case, the SK conductance) can have a different effect on these two oscillatory behaviors (pacemaking and SOPs), despite the fact that they have the same initiating mechanism. These results highlight the fact that computational approaches, besides their well known confirmatory and predictive interests in neurophysiology, may also be useful to resolve apparent discrepancies between experimental results. Dopamine is a neurotransmitter which plays important roles in the control of voluntary movement, motivation and reward, attention, and learning. Dysfunction of midbrain dopaminergic systems is involved in various diseases such as Parkinson's disease, schizophrenia and drug abuse. This underlines the importance of a tight regulation of dopamine levels in the brain. At the cellular level, the release of dopamine is directly correlated to the type of electrical activity (the firing pattern) of nerve cells that produce it, the so-called “dopaminergic neurons”. Therefore, an in depth understanding of the mechanisms underlying the electrical behavior of dopaminergic neurons is of critical importance to find new strategies for the treatment of diseases that result from dysfunction of this system.
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Affiliation(s)
- Guillaume Drion
- Laboratory of Pharmacology and GIGA Neurosciences, University of Liège, Liège, Belgium
- Department of Electrical Engineering and Computer Science, University of Liège, Liège, Belgium
| | - Laurent Massotte
- Laboratory of Pharmacology and GIGA Neurosciences, University of Liège, Liège, Belgium
| | - Rodolphe Sepulchre
- Department of Electrical Engineering and Computer Science, University of Liège, Liège, Belgium
| | - Vincent Seutin
- Laboratory of Pharmacology and GIGA Neurosciences, University of Liège, Liège, Belgium
- * E-mail:
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Thomas RC. The Ca(2+): H(+) coupling ratio of the plasma membrane calcium ATPase in neurones is little sensitive to changes in external or internal pH. Cell Calcium 2011; 49:357-64. [PMID: 21466891 PMCID: PMC3121948 DOI: 10.1016/j.ceca.2011.03.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 03/10/2011] [Indexed: 11/25/2022]
Abstract
To explore the effects of both external and internal pH (pHo and pHi) on the coupling between Ca2+ extrusion and H+ uptake by the PMCA activity in snail neurones H+ uptake was assessed by measuring surface pH changes (ΔpHs) with pH-sensitive microelectrodes while Ba2+ or Ca2+ loads were extruded. Ru360 or ruthenium red injection showed that injected Ca2+ was partly taken up by mitochondria, but Ca2+ entering through channels was not. External pH was changed using a mixture of three buffers to minimise changes in buffering power. With depolarisation-induced Ca2+ or Ba2+ loads the ΔpHs were not changed significantly over the pH range 6.5–8.5. With Ca2+ injections into cells with mitochondrial uptake blocked the ΔpHs were significantly smaller at pH 8.5 than at 7.5, but this could be explained in part by the slower rate of activity of the PMCA. Low intracellular pH also changed the ΔpHs responses to Ca2+ injection, but not significantly. Again this may have been due to reduced pump activity at low pHi. I conclude that in snail neurones the PMCA coupling ratio is either insensitive or much less sensitive to pH than in red blood cells or barnacle muscle.
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Affiliation(s)
- Roger C Thomas
- Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Site, Cambridge CB2 3EG, UK.
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22
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Faxén K, Andersen JL, Gourdon P, Fedosova N, Morth JP, Nissen P, Møller JV. Characterization of a Listeria monocytogenes Ca(2+) pump: a SERCA-type ATPase with only one Ca(2+)-binding site. J Biol Chem 2011; 286:1609-17. [PMID: 21047776 PMCID: PMC3020769 DOI: 10.1074/jbc.m110.176784] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 10/21/2010] [Indexed: 11/06/2022] Open
Abstract
We have characterized a putative Ca(2+)-ATPase from the pathogenic bacterium Listeria monocytogenes with the locus tag lmo0841. The purified and detergent-solubilized protein, which we have named Listeria monocytogenes Ca(2+)-ATPase 1 (LMCA1), performs a Ca(2+)-dependent ATP hydrolysis and actively transports Ca(2+) after reconstitution in dioleoylphosphatidyl-choline vesicles. Despite a high sequence similarity to the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA1a) and plasma membrane Ca(2+)-ATPase (PMCA), LMCA1 exhibits important biochemical differences such as a low Ca(2+) affinity (K(0.5) ∼80 μm) and a high pH optimum (pH ∼9). Mutational studies indicate that the unusually high pH optimum can be partially ascribed to the presence of an arginine residue (Arg-795), corresponding in sequence alignments to the Glu-908 position at Ca(2+) binding site I of rabbit SERCA1a, but probably with an exposed position in LMCA1. The arginine is characteristic of a large group of putative bacterial Ca(2+)-ATPases. Moreover, we demonstrate that H(+) is countertransported with a transport stoichiometry of 1 Ca(2+) out and 1 H(+) in per ATP hydrolyzed. The ATPase may serve an important function by removing Ca(2+) from the microorganism in environmental conditions when e.g. stressed by high Ca(2+) and alkaline pH.
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Affiliation(s)
- Kristina Faxén
- From the Departments of Molecular Biology, Gustav Wieds Vej 10C, and
| | | | - Pontus Gourdon
- From the Departments of Molecular Biology, Gustav Wieds Vej 10C, and
| | - Natalya Fedosova
- Physiology and Biophysics, Ole Worms Allé 6, Centre for Membrane Pumps in Cells and Disease, PUMPKIN, Danish National Research Foundation, Aarhus University, DK-8000, Aarhus, Denmark
| | - Jens Preben Morth
- From the Departments of Molecular Biology, Gustav Wieds Vej 10C, and
| | - Poul Nissen
- From the Departments of Molecular Biology, Gustav Wieds Vej 10C, and
| | - Jesper Vuust Møller
- Physiology and Biophysics, Ole Worms Allé 6, Centre for Membrane Pumps in Cells and Disease, PUMPKIN, Danish National Research Foundation, Aarhus University, DK-8000, Aarhus, Denmark
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Mata AM, Sepulveda MR. Plasma membrane Ca 2+-ATPases in the nervous system during development and ageing. World J Biol Chem 2010; 1:229-34. [PMID: 21537478 PMCID: PMC3083968 DOI: 10.4331/wjbc.v1.i7.229] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Revised: 07/01/2010] [Accepted: 07/08/2010] [Indexed: 02/05/2023] Open
Abstract
Calcium signaling is used by neurons to control a variety of functions, including cellular differentiation, synaptic maturation, neurotransmitter release, intracellular signaling and cell death. This review focuses on one of the most important Ca2+ regulators in the cell, the plasma membrane Ca2+-ATPase (PMCA), which has a high affinity for Ca2+ and is widely expressed in brain. The ontogeny of PMCA isoforms, linked to specific requirements of Ca2+ during development of different brain areas, is addressed, as well as their function in the adult tissue. This is based on the high diversity of variants in the PMCA family in brain, which show particular kinetic differences possibly related to specific localizations and functions of the cell. Conversely, alterations in the activity of PMCAs could lead to changes in Ca2+ homeostasis and, consequently, to neural dysfunction. The involvement of PMCA isoforms in certain neuropathologies and in brain ageing is also discussed.
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Affiliation(s)
- Ana M Mata
- Ana M Mata, M Rosario Sepulveda, Department of Biochemistry and Molecular Biology and Genetics, Faculty of Sciences, University of Extremadura, 06006 Badajoz, Spain
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Zhang XQ, Chi ZG, Xu BJ, Li HY, Zhou W, Li XF, Zhang Y, Liu SW, Xu JR. Comparison of Responsive Behaviors of Two Cinnamic Acid Derivatives Containing Carbazolyl Triphenylethylene. J Fluoresc 2010; 21:133-40. [DOI: 10.1007/s10895-010-0697-y] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Accepted: 06/22/2010] [Indexed: 11/27/2022]
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Meneghelli S, Fusca T, Luoni L, De Michelis MI. Dual mechanism of activation of plant plasma membrane Ca2+-ATPase by acidic phospholipids: evidence for a phospholipid binding site which overlaps the calmodulin-binding site. Mol Membr Biol 2009; 25:539-46. [PMID: 18988067 DOI: 10.1080/09687680802508747] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The effect of phospholipids on the activity of isoform ACA8 of Arabidopsis thaliana plasma membrane (PM) Ca2+-ATPase was evaluated in membranes isolated from Saccharomyces cerevisiae strain K616 expressing wild type or mutated ACA8 cDNA. Acidic phospholipids stimulated the basal Ca2+-ATPase activity in the following order of efficiency: phosphatidylinositol 4-monophosphate > phosphatidylserine > phosphatidylcholine approximately = phosphatidylethanolamine approximately = 0. Acidic phospholipids increased V(max-Ca2+) and lowered the value of K(0.5-Ca2+) below the value measured in the presence of calmodulin (CaM). In the presence of CaM acidic phospholipids activated ACA8 by further decreasing its K(0.5-Ca2+) value. Phosphatidylinositol 4-monophosphate and, with lower efficiency, phosphatidylserine bound peptides reproducing ACA8 N-terminus (aa 1-116). Single point mutation of three residues (A56, R59 and Y62) within the sequence A56-T63 lowered the apparent affinity of ACA8 for phosphatidylinositol 4-monophosphate by two to three fold, indicating that this region contains a binding site for acidic phospholipids. However, the N-deleted mutant Delta74-ACA8 was also activated by acidic phospholipids, indicating that acidic phospholipids activate ACA8 through a complex mechanism, involving interaction with different sites. The striking similarity between the response to acidic phospholipids of ACA8 and animal plasma membrane Ca2+-ATPase provides new evidence that type 2B Ca2+-ATPases share common regulatory properties independently of structural differences such as the localization of the terminal regulatory region at the N- or C-terminal end of the protein.
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Affiliation(s)
- Silvia Meneghelli
- Dipartimento di Biologia, Universita di Milano, Istituto di Biofisica del CNR, Sezione di Milano, Milano, Italy
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Thomas RC. The plasma membrane calcium ATPase (PMCA) of neurones is electroneutral and exchanges 2 H+ for each Ca2+ or Ba2+ ion extruded. J Physiol 2008; 587:315-27. [PMID: 19064619 PMCID: PMC2670047 DOI: 10.1113/jphysiol.2008.162453] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The coupling between Ca2+ extrusion and H+ uptake by the ubiquitous plasma membrane calcium ATPase (PMCA) has not been measured in any neurone. I have investigated this with Ca2+- and pH-sensitive microelectrodes in large voltage-clamped snail neurones, which have no Na+-Ca2+ exchangers. The recovery of [Ca2+]i and surface pH after a brief depolarization or Ca2+ injection was not slowed by hyperpolarization to -90 mV from a holding potential of -50 mV, consistent with a 1 Ca2+ : 2 H+ coupling ratio. Since Ca2+ injections proved difficult to quantify, and Ca2+ currents through channels were obscured by K+ currents, Ba2+ was used as a substitute. When the cell was bathed in Ca2+-free Ba2+ Ringer solution, the K+ currents were blocked and large inward currents were revealed on depolarization. The Ca2+-sensitive microelectrodes were sensitive to intracellular Ba2+ as well as Ca2+. With equal depolarizations Ba2+ entry appeared larger than Ca2+ entry and generated similar but slower pH changes. Ba2+ extrusion was insensitive to hyperpolarization, blocked by eosin or high pH, and about 5 times slower than Ca2+ extrusion. The ratio of the pH change caused by the extrusion of unit charge of Ba2+ influx to that caused by unit charge of H+ injection was 0.85 +/- 0.08 (s.e.m., n = 8), corresponding to a Ba2+ : H+ ratio of 1 : 1.7. Both this ratio and the electroneutrality of the PMCA suggest that the Ca2+ : H+ ratio is 1 : 2, ensuring that after a Ca2+ influx [Ca2+]i recovery is not influenced by the membrane potential and maximizes the conversion of Ca2+ influxes into possible pH signals.
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Affiliation(s)
- Roger C Thomas
- Physiological Laboratory, University of Cambridge, Downing Site, Cambridge, UK.
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27
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Liu Y, Han M, Zhang HY, Yang LX, Jiang W. A proton-triggered ON-OFF-ON fluorescent chemosensor for Mg(II) via twisted intramolecular charge transfer. Org Lett 2008; 10:2873-6. [PMID: 18540629 DOI: 10.1021/ol801048t] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A novel fluorescent chemosensor has been synthesized and shows interesting fluorescent ON-OFF-ON processes through mediating its twisted intramolecular charge transfer (TICT) state. An exclusively fluorescent enhancement is observed for Mg (2+).
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Affiliation(s)
- Yu Liu
- Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, PRC.
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Niggli V, Sigel E. Anticipating antiport in P-type ATPases. Trends Biochem Sci 2008; 33:156-60. [PMID: 18343670 DOI: 10.1016/j.tibs.2007.12.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Revised: 12/03/2007] [Accepted: 12/07/2007] [Indexed: 11/20/2022]
Abstract
Cation-transporting P-type ATPases show a high degree of structural and functional homology. Nevertheless, for many members of this large family, the molecular mechanism of transport is unclear; namely, whether transport is electrogenic or not and if countertransport is involved remains to be established. In a few well-studied cases such as the Na(+)-K(+)-ATPase, plasma membrane Ca(2+) ATPase (PMCA) and sarcoplasmic reticulum Ca(2+) ATPase (SERCA) countertransport has been clearly demonstrated. New data based on the crystal structure of SERCA now strongly indicate that countertransport could be mandatory for all P-type ATPases. This concept should be verified for other known and for all newly characterized P-type ATPases.
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Affiliation(s)
- Verena Niggli
- Institute of Pathology, University of Bern, Murtenstrasse 31, Bern, Switzerland.
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29
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Kreitzer MA, Collis LP, Molina AJA, Smith PJS, Malchow RP. Modulation of extracellular proton fluxes from retinal horizontal cells of the catfish by depolarization and glutamate. ACTA ACUST UNITED AC 2007; 130:169-82. [PMID: 17664345 PMCID: PMC2151636 DOI: 10.1085/jgp.200709737] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Self-referencing H(+)-selective microelectrodes were used to measure extracellular proton fluxes from cone-driven horizontal cells isolated from the retina of the catfish (Ictalurus punctatus). The neurotransmitter glutamate induced an alkalinization of the area adjacent to the external face of the cell membrane. The effect of glutamate occurred regardless of whether the external solution was buffered with 1 mM HEPES, 3 mM phosphate, or 24 mM bicarbonate. The AMPA/kainate receptor agonist kainate and the NMDA receptor agonist N-methyl-D-aspartate both mimicked the effect of glutamate. The effect of kainate on proton flux was inhibited by the AMPA/kainate receptor blocker CNQX, and the effect of NMDA was abolished by the NMDA receptor antagonist DAP-5. Metabotropic glutamate receptor agonists produced no alteration in proton fluxes from horizontal cells. Depolarization of cells either by increasing extracellular potassium or directly by voltage clamp also produced an alkalinization adjacent to the cell membrane. The effects of depolarization on proton flux were blocked by 10 microM nifedipine, an inhibitor of L-type calcium channels. The plasmalemma Ca(2+/)H(+) ATPase (PMCA) blocker 5(6)-carboxyeosin also significantly reduced proton flux modulation by glutamate. Our results are consistent with the hypothesis that glutamate-induced extracellular alkalinizations arise from activation of the PMCA pump following increased intracellular calcium entry into cells. This process might help to relieve suppression of photoreceptor neurotransmitter release that results from exocytosed protons from photoreceptor synaptic terminals. Our findings argue strongly against the hypothesis that protons released by horizontal cells act as the inhibitory feedback neurotransmitter that creates the surround portion of the receptive fields of retinal neurons.
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Affiliation(s)
- Matthew A Kreitzer
- Department of Biology, Indiana Wesleyan University, Marion, IN 46953, USA.
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30
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Szewczyk MM, Pande J, Grover AK. Caloxins: a novel class of selective plasma membrane Ca2+ pump inhibitors obtained using biotechnology. Pflugers Arch 2007; 456:255-66. [PMID: 17909851 DOI: 10.1007/s00424-007-0348-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Accepted: 09/06/2007] [Indexed: 12/22/2022]
Abstract
Plasma membrane Ca2+ pumps (PMCA) extrude cellular Ca2+ with a high affinity and hence play a major role in Ca2+ homeostasis and signaling. Caloxins (selective extracellular PMCA inhibitors) would aid in elucidating the physiology of PMCA. PMCA proteins have five extracellular domains (exdoms). Our hypotheses are: 1) peptides that bind selectively to each exdom can be invented by screening a random peptide library, and 2) a peptide can modulate PMCA activity by binding to one of the exdoms. The first caloxin 2a1, selected for binding exdom 2 was selective for PMCA (Ki=529 microM). It has been used to examine the physiological role of PMCA. PMCA isoforms are encoded by four genes. PMCA isoform expression differs in various cell types, with PMCA1 and 4 being the most widely distributed. There are differences between PMCA1-4 exdom 1 sequences, which may be exploited for inventing isoform selective caloxins. Using exdom 1 of PMCA4 as a target, modified screening procedures and mutagenesis led to the high-affinity caloxin 1c2 (Ki=2.3 microM for PMCA4). It is selective for PMCA4 over PMCA1, 2, or 3. We hope that caloxins can be used to discern the roles of individual PMCA isoforms in Ca2+ homeostasis and signaling. Caloxins may also become clinically useful in cardiovascular diseases, neurological disorders, retinopathy, cancer, and contraception.
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Affiliation(s)
- Magdalena M Szewczyk
- Department of Biology, McMaster University, HSC 4N41, 1200 Main Street W, Hamilton, ON L8N3Z5, Canada
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31
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Canavier CC, Oprisan SA, Callaway JC, Ji H, Shepard PD. Computational model predicts a role for ERG current in repolarizing plateau potentials in dopamine neurons: implications for modulation of neuronal activity. J Neurophysiol 2007; 98:3006-22. [PMID: 17699694 DOI: 10.1152/jn.00422.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Blocking the small-conductance (SK) calcium-activated potassium channel promotes burst firing in dopamine neurons both in vivo and in vitro. In vitro, the bursting is unusual in that spiking persists during the hyperpolarized trough and frequently terminates by depolarization block during the plateau. We focus on the underlying plateau potential oscillation generated in the presence of both apamin and TTX, so that action potentials are not considered. We find that although the plateau potentials are mediated by a voltage-gated Ca(2+) current, they do not depend on the accumulation of cytosolic Ca(2+), then use a computational model to test the hypothesis that the slowly voltage-activated ether-a-go-go-related gene (ERG) potassium current repolarizes the plateaus. The model, which includes a material balance on calcium, is able to reproduce the time course of both membrane potential and somatic calcium concentration, and can also mimic the induction of plateau potentials by the calcium chelator BAPTA. The principle of separation of timescales was used to gain insight into the mechanisms of oscillation and its modulation using nullclines in the phase space. The model predicts that the plateau will be elongated and ultimately result in a persistent depolarization as the ERG current is reduced. This study suggests that the ERG current may play a role in burst termination and the relief of depolarization block in vivo.
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Affiliation(s)
- Carmen C Canavier
- Neuroscience Center, Louisiana State University Health Sciences Center, New Orleans 70112, USA.
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32
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Gatto C, Helms JB, Prasse MC, Huang SY, Zou X, Arnett KL, Milanick MA. Similarities and differences between organic cation inhibition of the Na,K-ATPase and PMCA. Biochemistry 2006; 45:13331-45. [PMID: 17073454 DOI: 10.1021/bi060667j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of three classes of organic cations on the inhibition of the plasma membrane Ca pump (PMCA) were determined and compared to inhibition of the Na pump. Quaternary amines (tetramethylammonium, tetraethylammonium, and tetrapropylammonium, TMA, TEA, and TPA, respectively) did not inhibit PMCA. This is not to imply that PMCA is inherently selective against monovalent cations because guanidine and tetramethylguanidine inhibited PMCA by competing with Ca(2+). The divalent organic cation, ethyl diamine, inhibited PMCA but was not competitive with Ca(2+). In contrast, propyl diamine did compete with Ca(2+) and was about 10-fold more potent than butyl diamine in inhibiting PMCA. For the Na pump, both TEA and TPA inhibited, but TMA did not. TEA, guanidine, and tetramethylguanidine inhibition was competitive with Na(+) for ATPase activation and with K(+) for pNPPase activation, both of which are cytoplasmic substrate cation effects. Thus, these findings are consistent with TEA, guanidine, and tetramethylguanidine inhibiting from the cytoplasmic side of the Na pump; in contrast, we have previously shown that TPA did not inhibit from the cytoplasmic side. The divalent alkane diamines ethyl, propyl, and butyl diamine all inhibited the Na pump and all competed at the intracellular surface. The order of potency was ED > PD > BD consistent with an optimal size for binding; similarly, for the quaternary amines TMA is apparently too small to make appropriate contacts, and TPA is too large. Homology models based upon the high-resolution SERCA structure are included to contextualize the kinetic observations.
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Affiliation(s)
- Craig Gatto
- Division of Biomedical Sciences, Department of Biological Sciences, Illinois State University, Normal, Illinois 61790-4120, USA
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33
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Hill JK, Brett CL, Chyou A, Kallay LM, Sakaguchi M, Rao R, Gillespie PG. Vestibular hair bundles control pH with (Na+, K+)/H+ exchangers NHE6 and NHE9. J Neurosci 2006; 26:9944-55. [PMID: 17005858 PMCID: PMC6674470 DOI: 10.1523/jneurosci.2990-06.2006] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
In hair cells of the inner ear, robust Ca2+/H+ exchange mediated by plasma-membrane Ca2+-ATPase would rapidly acidify mechanically sensitive hair bundles without efficient removal of H+. We found that, whereas the basolateral membrane of vestibular hair cells from the frog saccule extrudes H+ via an Na+-dependent mechanism, bundles rapidly remove H+ in the absence of Na+ and HCO3(-), even when the soma is acidified. K+ was fully effective and sufficient for H+ removal; in contrast, Rb+ failed to support pH recovery. Na+/H+-exchanger isoform 1 (NHE1) was present on hair-cell soma membranes and was likely responsible for Na+-dependent H+ extrusion. NHE6 and NHE9 are organellar isoforms that can appear transiently on plasma membranes and have been proposed to mediate K+/H+ exchange. We identified NHE6 in a subset of hair bundles; NHE9 was present in all bundles. Heterologous expression of these isoforms in yeast strains lacking endogenous exchangers conferred pH-dependent tolerance to high levels of KCl and NaCl. NHE9 preferred cations in the order K+, Na+ >> Rb+, consistent with the relative efficacies of these ions in promoting pH recovery in hair bundles. Electroneutral K+/H+ exchange, which we propose is performed by NHE9 in hair bundles, exploits the high-K+ endolymph, responds only to pH imbalance across the bundle membrane, is unaffected by the +80 mV endocochlear potential, and uses mechanisms already present in the ear for K+ recycling. This mechanism allows the hair cell to remove H+ generated by Ca2+ pumping without ATP hydrolysis in the cell.
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Affiliation(s)
- Jennifer K. Hill
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
| | - Christopher L. Brett
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland 21205, and
| | - Anthony Chyou
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland 21205, and
| | - Laura M. Kallay
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland 21205, and
| | - Masao Sakaguchi
- Graduate School of Life Science, University of Hyogo, Ako, Hyogo 678-1297, Japan
| | - Rajini Rao
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland 21205, and
| | - Peter G. Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
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34
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Gunaratne HJ, Neill AT, Vacquier VD. Plasma membrane calcium ATPase is concentrated in the head of sea urchin spermatozoa. J Cell Physiol 2006; 207:413-9. [PMID: 16358326 DOI: 10.1002/jcp.20575] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Plasma membrane Ca2+ATPases (PMCAs) export Ca2+ from cells in a highly regulated manner, providing fine-tuning to the maintenance of intracellular Ca2+ concentrations. There are few studies of PMCAs in spermatozoa, which is surprising considering the importance of this enzyme in all cell types. Here we describe the primary structure and localization of the PMCA of sea urchin spermatozoa (suPMCA). The suPMCA is 1,154 amino acids and has 56% identity and 76% similarity to all 4 human PMCA isoforms. The suPMCA shares the features of a typical PMCA, including domains for calmodulin binding, ATP binding, ATPase phosphorylation, and 10 putative transmembrane segments with two large cytoplasmic loops. Southern blots show that suPMCA is a single copy gene. Treatment of live sea urchin sperm with the PMCA inhibitor, 5-(-6)-carboxyeosin, results in elevations of intracellular Ca2+ and loss of flagellar motility. Immunoblotting and immunoflorescence show that suPMCA is concentrated in the sperm head plasma membrane. In previous work, we showed that a plasma membrane K+ dependent Na+/Ca2+ exchanger (suNCKX), which also keeps Ca2+ low in these cells, is concentrated in the sperm flagellum. Thus, the sperm head and flagellum localize different gene products, both functioning to keep intracellular Ca2+ low, while the sperm swims in seawater containing 10 mM Ca2+.
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Affiliation(s)
- Herath Jayantha Gunaratne
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0202, USA.
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35
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Sipido KR, Varro A, Eisner D. Sodium calcium exchange as a target for antiarrhythmic therapy. Handb Exp Pharmacol 2006:159-99. [PMID: 16610344 DOI: 10.1007/3-540-29715-4_6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
In search of better antiarrhythmic therapy, targeting the Na/Ca exchanger is an option to be explored. The rationale is that increased activity of the Na/Ca exchanger has been implicated in arrhythmogenesis in a number of conditions. The evidence is strong for triggered arrhythmias related to Ca2+ overload, due to increased Na+ load or during adrenergic stimulation; the Na/Ca exchanger may be important in triggered arrhythmias in heart failure and in atrial fibrillation. There is also evidence for a less direct role of the Na/Ca exchanger in contributing to remodelling processes. In this chapter, we review this evidence and discuss the consequences of inhibition of Na/Ca exchange in the perspective of its physiological role in Ca2+ homeostasis. We summarize the current data on the use of available blockers of Na/Ca exchange and propose a framework for further study and development of such drugs. Very selective agents have great potential as tools for further study of the role the Na/Ca exchanger plays in arrhythmogenesis. For therapy, they may have their specific indications, but they carry the risk of increasing Ca2+ load of the cell. Agents with a broader action that includes Ca2+ channel block may have advantages in other conditions, e.g. with Ca2+ overload. Additional actions such as block of K+ channels, which may be unwanted in e.g. heart failure, may be used to advantage as well.
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Affiliation(s)
- K R Sipido
- 'Lab. of Experimental Cardiology, KUL, Campus Gasthuisberg O/N 7th floor, Herestraat 49, B-3000 Leuven, Belgium.
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36
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Mata AM, Sepúlveda MR. Calcium pumps in the central nervous system. ACTA ACUST UNITED AC 2005; 49:398-405. [PMID: 16111566 DOI: 10.1016/j.brainresrev.2004.11.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Revised: 11/05/2004] [Accepted: 11/13/2004] [Indexed: 11/20/2022]
Abstract
Two families of Ca2+ transport ATPases are involved in the maintenance of Ca2+ homeostasis in the nervous system, the plasma membrane Ca2+-ATPase that pumps Ca2+ to the extracellular medium and the intracellular sarco/endoplasmic reticulum Ca2+-ATPase that transports Ca2+ from the cytosol to the endoplasmic reticulum. Both types of calcium pumps show precise regulatory properties and they are localized in specific subcellular regions. In this review, we describe the functional and regulatory properties of both families of calcium pumps, their distribution in nerve cells, and their involvement in neurological disorders. The functional characterization of neuronal calcium pumps is very important in order to understand the biochemical processes involved in the maintenance of intracellular calcium in synaptic terminals.
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Affiliation(s)
- Ana M Mata
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, Avda de Elvas 06071 Badajoz, Spain.
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37
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Sepúlveda MR, Hidalgo-Sánchez M, Mata AM. A developmental profile of the levels of calcium pumps in chick cerebellum. J Neurochem 2005; 95:673-83. [PMID: 16104848 DOI: 10.1111/j.1471-4159.2005.03401.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The functional expression and distribution of intracellular ATPase (sarco(endo)plasmic reticulum Ca(2+)-ATPase: SERCA) and plasma membrane Ca(2+)-ATPase (PMCA) was analyzed in the developing chick cerebellum. The activity and Ca(2+) uptake increase with development for both ATPases. However, the protein content increases with the stage of development only for SERCA, remaining constant for PMCA. Immunohistochemical assays showed that the ontogenesis of these ATPases goes along with definite stages of cerebellum histogenesis, and is complete at hatching. The SERCA is mainly distributed in Purkinje neurons, whereas the PMCA seems to be expressed initially in climbing fibers, shifting to soma and spiny branchlets of Purkinje cells at late embryonic stages. Granule cells express both ATPases according to their degree of maturity, whereas only PMCA is present in cerebellar glomeruli. These pumps are present in deep nuclei and the choroid plexus, although in this latter tissue their expression declines with development. The spatio-temporal distribution of SERCA and PMCA must be closely related to their association with the development of specific cells and processes of the chick cerebellum.
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Affiliation(s)
- M Rosario Sepúlveda
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
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38
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Suzuki Y, Ueno S, Ohnuma R, Koyama N. Cloning, sequencing and functional expression in Escherichia coli of the gene for a P-type Na(+)-ATPase of a facultatively anaerobic alkaliphile, Exiguobacterium aurantiacum. ACTA ACUST UNITED AC 2005; 1727:162-8. [PMID: 15715958 DOI: 10.1016/j.bbaexp.2004.12.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2004] [Revised: 12/21/2004] [Accepted: 12/22/2004] [Indexed: 11/21/2022]
Abstract
Cloning and sequencing of the gene encoding a P-type Na(+)-ATPase of a facultatively anaerobic alkaliphile, Exiguobacterium aurantiacum, were conducted. The structural gene was composed of 2628 nucleotides. The deduced amino acid sequence (876 amino acid residues; Mr, 96,664) suggested that the enzyme possesses 10 membrane-spanning regions. When the amino acid sequences of the four putative membrane regions, M4, M5, M6 and M8, of BL77/1 ATPase were aligned with those of fungal Na(+)-ATPase, Na(+)/K(+)-ATPase, H(+)-ATPases and sarcoplasmic reticulum Ca(2+)-ATPase, it exhibited the highest homology with Ca(2+)-ATPase except M5 region. By the transformation of Escherichia coli with the expression vector (pQE30) containing the ATPase gene, the enzyme was functionally expressed in E. coli membranes.
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Affiliation(s)
- Yuusuke Suzuki
- Department of Chemistry, Faculty of Science, Chiba University, Yayoi, Inage-ku, Chiba 263-8522, Japan
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39
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Fioretti B, Franciolini F, Catacuzzeno L. A model of intracellular Ca2+ oscillations based on the activity of the intermediate-conductance Ca2+-activated K+ channels. Biophys Chem 2005; 113:17-23. [PMID: 15617807 DOI: 10.1016/j.bpc.2004.07.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2004] [Revised: 07/15/2004] [Accepted: 07/21/2004] [Indexed: 11/25/2022]
Abstract
Intracellular Ca2+ oscillations are observed in a large number of non-excitable cells. While most appear to reflect an intermittent Ca2+ release from intracellular stores, in some instances intracellular Ca2+ oscillations strongly depend on Ca2+ influx, and are coupled to oscillations of the membrane potential, suggesting that a plasma membrane-based mechanism may be involved. We have developed a theoretical model for the latter type of intracellular Ca2+ oscillations based on the Ca2+-dependent modulation of the intermediate-conductance, Ca2+-activated K+ (IKCa) channel. The functioning of this model relies on the Ca2+-dependent activation, and the much slower Ca2+-dependent rundown of this channel. We have shown that Ca2+-dependent activation of the IKCa channels, the consequent membrane hyperpolarization and the resulting increase in Ca2+ influx may confer the positive feedback mechanism required for the ascending phase of the oscillation. The much slower Ca2+-dependent rundown process will conversely halt this positive loop, and establish the descending phase of the intracellular Ca2+ oscillation. We found that this simple model gives rise to intracellular Ca2+ oscillations when using physiologically reasonable parameters, suggesting that IKCa channels could participate in the generation of intracellular Ca2+ oscillations.
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Affiliation(s)
- Bernard Fioretti
- Dipartimento di Biologia Cellulare e Molecolare Universita' di Perugia via Pascoli 1, I-06123 Perugia, Italy
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40
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Sepúlveda MR, Mata AM. The interaction of ethanol with reconstituted synaptosomal plasma membrane Ca2+ -ATPase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2004; 1665:75-80. [PMID: 15471573 DOI: 10.1016/j.bbamem.2004.06.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2004] [Revised: 06/25/2004] [Accepted: 06/28/2004] [Indexed: 11/28/2022]
Abstract
The primary effect of ethanol is on the central nervous system. However, the molecular mechanisms responsible for the physiological symptoms of ethanol intoxication are still unknown. Low concentrations of ethanol were observed to stimulate the activity of the calcium pump from reconstituted synaptosomal plasma membrane Ca2+ -ATPase (PMCA), and ethanol inhibited Ca2+ -ATPase activity at concentrations above 5%. The greatest stimulating effect was obtained with 5% (v/v) ethanol and was lipid-dependent, being 74% when the protein had been reconstituted in phosphatidylcholine (PC) and less when the reconstituted protein had previously been activated by calmodulin or after removal of a 9-kDa autoinhibitory site by controlled trypsinization. Stimulation of the pump by ethanol was lower for the native or trypsin-digested protein in the presence of phosphatidylserine than in PC. These results suggest a direct ethanol-protein interaction, because the activating effect depended on the state of Ca2+ -ATPase (native or truncated, or in presence of calmodulin). The activating mechanism of ethanol may involve opening an autoinhibitory domain located close to the calmodulin binding domain.
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Affiliation(s)
- M Rosario Sepúlveda
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain
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41
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Molina AJA, Verzi MP, Birnbaum AD, Yamoah EN, Hammar K, Smith PJS, Malchow RP. Neurotransmitter modulation of extracellular H+ fluxes from isolated retinal horizontal cells of the skate. J Physiol 2004; 560:639-57. [PMID: 15272044 PMCID: PMC1665295 DOI: 10.1113/jphysiol.2004.065425] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2004] [Accepted: 07/16/2004] [Indexed: 11/08/2022] Open
Abstract
Self-referencing H(+)-selective microelectrodes were used to measure extracellular H(+) fluxes from horizontal cells isolated from the skate retina. A standing H(+) flux was detected from quiescent cells, indicating a higher concentration of free hydrogen ions near the extracellular surface of the cell as compared to the surrounding solution. The standing H(+) flux was reduced by removal of extracellular sodium or application of 5-(N-ethyl-N-isopropyl) amiloride (EIPA), suggesting activity of a Na(+)-H(+) exchanger. Glutamate decreased H(+) flux, lowering the concentration of free hydrogen ions around the cell. AMPA/kainate receptor agonists mimicked the response, and the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) eliminated the effects of glutamate and kainate. Metabotropic glutamate agonists were without effect. Glutamate-induced alterations in H(+) flux required extracellular calcium, and were abolished when cells were bathed in an alkaline Ringer solution. Increasing intracellular calcium by photolysis of the caged calcium compound NP-EGTA also altered extracellular H(+) flux. Immunocytochemical localization of the plasmalemma Ca(2+)-H(+)-ATPase (PMCA pump) revealed intense labelling within the outer plexiform layer and on isolated horizontal cells. Our results suggest that glutamate modulation of H(+) flux arises from calcium entry into cells with subsequent activation of the plasmalemma Ca(2+)-H(+)-ATPase. These neurotransmitter-induced changes in extracellular pH have the potential to play a modulatory role in synaptic processing in the outer retina. However, our findings argue against the hypothesis that hydrogen ions released by horizontal cells normally act as the inhibitory feedback neurotransmitter onto photoreceptor synaptic terminals to create the surround portion of the centre-surround receptive fields of retinal neurones.
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Affiliation(s)
- Anthony J A Molina
- Department of Biological Sciences, University of Illinois at Chicago, IL 60607, USA
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42
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Prasad V, Okunade GW, Miller ML, Shull GE. Phenotypes of SERCA and PMCA knockout mice. Biochem Biophys Res Commun 2004; 322:1192-203. [PMID: 15336967 DOI: 10.1016/j.bbrc.2004.07.156] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2004] [Indexed: 10/26/2022]
Abstract
P-type Ca2+-ATPases of the sarco(endo)plasmic reticulum (SERCAs) and plasma membrane (PMCAs) are responsible for maintaining the Ca2+ gradients across cellular membranes that are required for regulation of Ca2+-mediated signaling and other biological processes. Gene-targeting studies of SERCA isoforms 1, 2, and 3 and PMCA isoforms 1, 2, and 4 have confirmed some of the general functions proposed for these pumps, such as a major role in excitation-contraction coupling for SERCA1 and SERCA2 and housekeeping functions for PMCA1 and SERCA2, but have also revealed some unexpected phenotypes. These include squamous cell cancer and plasticity in the regulation of Ca2+-mediated exocytosis in SERCA2 heterozygous mutant mice, modulation of Ca2+ signaling in SERCA3-deficient mice, deafness and balance disorders in PMCA2 null mice, and male infertility in PMCA4 null mice. These unique phenotypes provide new information about the cellular functions of these pumps, the requirement of their activities for higher order physiological processes, and the pathophysiological consequences of pump dysfunction.
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Affiliation(s)
- Vikram Prasad
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0524, USA
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43
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Zoccola D, Tambutté E, Kulhanek E, Puverel S, Scimeca JC, Allemand D, Tambutté S. Molecular cloning and localization of a PMCA P-type calcium ATPase from the coral Stylophora pistillata. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2004; 1663:117-26. [PMID: 15157614 DOI: 10.1016/j.bbamem.2004.02.010] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2003] [Revised: 02/20/2004] [Accepted: 02/27/2004] [Indexed: 11/16/2022]
Abstract
Plasma-membrane calcium pumps (PMCAs) are responsible for the expulsion of Ca(2+) from the cytosol of all eukaryotic cells and are one of the major transport systems involved in long-term regulation of resting intracellular Ca(2+) concentration. An important feature of stony corals, one of the major groups of calcifying animals, is the continuous export of large quantities of Ca(2+) for skeletogenesis. Here, we report the cloning and functional expression of the stpPMCA gene from the coral Stylophora pistillata, and whose features resemble those of the plasma-membrane Ca(2+)-ATPase family of mammalian cells. This is the first known example of a Ca(2+)-ATPase from the phylum Cnidaria, and thus, the most phylogenetically distant PMCA sequence in the animal kingdom described to date. We demonstrate that the localization of stpPMCA within calicoblastic cells is fully coherent with its role in calcification. We also show that the coral Ca(2+) pump is more closely related to vertebrate PMCAs than to Caenorhabditis elegans PMCAs. The cloning of evolutionarily conserved genes from cnidarian species repeatedly shows that these genes encode similar functional domains. Moreover, this high level of gene conservation further validates the use of cnidarian model systems for studying processes shared by Eumetazoans.
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Affiliation(s)
- Didier Zoccola
- Centre Scientifique de Monaco, Avenue Saint Martin, MC-98000, Monaco.
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44
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Palacios J, Sepúlveda MR, Lee AG, Mata AM. Ca2+ Transport by the Synaptosomal Plasma Membrane Ca2+-ATPase and the Effect of Thioridazine. Biochemistry 2004; 43:2353-8. [PMID: 14979732 DOI: 10.1021/bi0359473] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thioridazine inhibits the activity of the synaptic plasma membrane Ca(2+)-ATPase from pig brain and slightly decreases the rate of Ca(2+) accumulation by synaptic plasma membrane vesicles in the absence of phosphate. However, in the presence of phosphate, thioridazine increases the rate of Ca(2+) accumulation into synaptic plasma membrane vesicles. Phosphate anions diffuse through the membrane and form calcium phosphate crystals, reducing the free Ca(2+) concentration inside the vesicles and the rate of Ca(2+) leak. The higher levels of Ca(2+) accumulation obtained in the presence of thioridazine could be explained by a reduction of the rate of slippage on the plasma membrane ATPase.
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Affiliation(s)
- Javier Palacios
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain
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45
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Palacios J, Sepúlveda MR, Salvador JM, Mata AM. Effect of spermine on the activity of synaptosomal plasma membrane Ca(2+)-ATPase reconstituted in neutral or acidic phospholipids. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1611:197-203. [PMID: 12659961 DOI: 10.1016/s0005-2736(03)00057-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The activity of purified plasma membrane Ca(2+)-ATPase (PMCA) from pig brain was inhibited by spermine (a naturally occurring and highly abundant polycation in brain). The level of inhibition was dependent on the phospholipid used for reconstitution as well as on the intact or truncated state of the enzyme. An IC(50) value of 12.5 mM spermine was obtained for both, the intact protein plus calmodulin and the trypsin-digested protein, reconstituted in phosphatidylcholine (PC). In the absence of calmodulin the intact Ca(2+)-ATPase gave an IC(50) of 27 mM. This form was more sensitive to spermine inhibition when it was reconstituted with phosphatidylserine (PS), showing an IC(50) value of 2.5 mM spermine. However, the truncated form was less responsive to spermine inhibition, having an IC(50) value of 12.5 mM. Spermine has no effect on the affinity of the PMCA for Ca(2+) or ATP, but its effect on the protein is pH-dependent. It is suggested that spermine could bind to negatively charged residues on the ATPase with different accessibility, depending on the structural rearrangement of the protein. Further, when the protein is reconstituted in PS, spermine also binds to the lipid.
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Affiliation(s)
- Javier Palacios
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain
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46
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Rigaud JL. Membrane proteins: functional and structural studies using reconstituted proteoliposomes and 2-D crystals. Braz J Med Biol Res 2002; 35:753-66. [PMID: 12131914 DOI: 10.1590/s0100-879x2002000700001] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Reconstitution of membrane proteins into lipid bilayers is a powerful tool to analyze functional as well as structural areas of membrane protein research. First, the proper incorporation of a purified membrane protein into closed lipid vesicles, to produce proteoliposomes, allows the investigation of transport and/or catalytic properties of any membrane protein without interference by other membrane components. Second, the incorporation of a large amount of membrane proteins into lipid bilayers to grow crystals confined to two dimensions has recently opened a new way to solve their structure at high resolution using electron crystallography. However, reconstitution of membrane proteins into functional proteoliposomes or 2-D crystallization has been an empirical domain, which has been viewed for a long time more like "black magic" than science. Nevertheless, in the last ten years, important progress has been made in acquiring knowledge of lipid-protein-detergent interactions and has permitted to build upon a set of basic principles that has limited the empirical approach of reconstitution experiments. Reconstitution strategies have been improved and new strategies have been developed, facilitating the success rate of proteoliposome formation and 2-D crystallization. This review deals with the various strategies available to obtain proteoliposomes and 2-D crystals from detergent-solubilized proteins. It gives an overview of the methods that have been applied, which may be of help for reconstituting more proteins into lipid bilayers in a form suitable for functional studies at the molecular level and for high-resolution structural analysis.
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Affiliation(s)
- J-L Rigaud
- Institut Curie, UMR-CNRS 168 and LRC-CEA 8, Paris, France.
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47
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Ollivon M, Lesieur S, Grabielle-Madelmont C, Paternostre M. Vesicle reconstitution from lipid-detergent mixed micelles. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1508:34-50. [PMID: 11090817 DOI: 10.1016/s0304-4157(00)00006-x] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The process of formation of lipid vesicles using the technique of detergent removal from mixed-micelles is examined. Recent studies on the solubilization and reconstitution of liposomes participated to our knowledge of the structure and properties of mixed lipid-detergent systems. The mechanisms involved in both the lipid self assembly and the micelle-vesicle transition are first reviewed. The simplistic three step minimum scheme is described and criticized in relation with isothermal as well as a function of the [det]/[lip] ratio, phase diagram explorations. The techniques of detergent elimination are reviewed and criticized for advantages and disadvantages. New methods inducing micelle-vesicle transition using enzymatic reaction and T-jump are also described and compared to more classical ones. Future developments of these techniques and improvements resulting of their combinations are also considered. Proper reconstitution of membrane constituents such as proteins and drugs into liposomes are examined in the light of our actual understanding of the micelle-vesicle transition.
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Affiliation(s)
- M Ollivon
- Equipe Physico-Chimie des Systèmes Polyphasés, CNRS UMR 8612, Université Paris-Sud, 5 rue Jean-Baptiste Clement, 92296, Ch atenay-Malabry, France.
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48
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Luoni L, Bonza MC, De Michelis MI. H(+)/Ca(2+) exchange driven by the plasma membrane Ca(2+)-ATPase of Arabidopsis thaliana reconstituted in proteoliposomes after calmodulin-affinity purification. FEBS Lett 2000; 482:225-30. [PMID: 11024465 DOI: 10.1016/s0014-5793(00)02065-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The plasma membrane Ca(2+)-ATPase was purified from Arabidopsis thaliana cultured cells by calmodulin (CaM)-affinity chromatography and reconstituted in proteoliposomes by the freeze-thaw sonication procedure. The reconstituted enzyme catalyzed CaM-stimulated 45Ca(2+) accumulation and H(+) ejection, monitored by the increase of fluorescence of the pH probe pyranine entrapped in the liposomal lumen during reconstitution. Proton ejection was immediately reversed by the protonophore FCCP, indicating that it is not electrically coupled to Ca(2+) uptake, but it is a primary event linked to Ca(2+) uptake in the form of countertransport.
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Affiliation(s)
- L Luoni
- Dipartimento di Biologia 'L. Gorini', Università di Milano, Centro di Studio del CNR per la Biologia Cellulare e Molecolare delle Piante, via G. Celoria 26, 20133, Milan, Italy
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49
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Abstract
The acidocalcisome is an acidic calcium store in trypanosomatids with a vacuolar-type proton-pumping pyrophosphatase (V-H(+)-PPase) located in its membrane. In this paper, we describe a new method using iodixanol density gradients for purification of the acidocalcisome from Trypanosoma cruzi epimastigotes. Pyrophosphatase assays indicated that the isolated organelle was at least 60-fold purified compared with the large organelle (10,000 x g) fraction. Assays for other organelles generally indicated no enrichment in the acidocalcisome fraction; glycosomes were concentrated 5-fold. Vanadate-sensitive ATP-driven Ca(2+) uptake (Ca(2+)-ATPase) activity was detectable in the isolated acidocalcisome, but ionophore experiments indicated that it was not acidic. However, when pyrophosphate was added, the organelle acidified, and the rate of Ca(2+) uptake increased. Use of the indicator Oxonol VI showed that V-H(+)-PPase activity generated a membrane potential. Use of sulfate or nitrate in place of chloride in the assay buffer did not affect V-H(+)-PPase activity, but there was less activity with gluconate. Organelle acidification was countered by the chloride/proton symport cycloprogidiosin. No vacuolar H(+)-ATPase activity was detectable in isolated acidocalcisomes. However, immunoblots showed the presence of at least a membrane-bound V-H(+)-ATPase subunit, while experiments employing permeabilized epimastigotes suggested that vacuolar H(+)-ATPase and V-H(+)-PPase activities are present in the same Ca(2+)-containing compartment.
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Affiliation(s)
- D A Scott
- Laboratory of Molecular Parasitology, Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61802, USA.
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50
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Xu W, Wilson BJ, Huang L, Parkinson EL, Hill BJ, Milanick MA. Probing the extracellular release site of the plasma membrane calcium pump. Am J Physiol Cell Physiol 2000; 278:C965-72. [PMID: 10794670 DOI: 10.1152/ajpcell.2000.278.5.c965] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The plasma membrane Ca(2+) pump is known to mediate Ca(2+)/H(+) exchange. Extracellular protons activated (45)Ca(2+) efflux from human red blood cells with a half-maximal inhibition constant of 2 nM when the intracellular pH was fixed. An increase in pH from 7.2 to 8.2 decreased the IC(50) for extracellular Ca(2+) from approximately 33 to approximately 6 mM. Changing the membrane potential by >54 mV had no effect on the IC(50) for extracellular Ca(2+). This argues against Ca(2+) release through a high-field access channel. Extracellular Ni(2+) inhibited Ca(2+) efflux with an IC(50) of 11 mM. Extracellular Cd(2+) inhibited with an IC(50) of 1. 5 mM, >10 times better than Ca(2+). The Cd(2+) IC(50) also decreased when the pH was raised from 7.1 to 8.2, consistent with Ca(2+), Cd(2+), and H(+) competing for the same site. The higher affinity for inhibition by Ni(2+) and Cd(2+) is consistent with a histidine or cysteine as part of the release site. The cysteine reagent 2-(trimethylammonium)ethyl methanethiosulfonate did not inhibit Ca(2+) efflux. Our results are consistent with the notion that the release site contains a histidine.
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Affiliation(s)
- W Xu
- Department of Physiology and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri 65212, USA
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