1
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Gradogna A, Lagostena L, Beltrami S, Tosato E, Picco C, Scholz-Starke J, Sparla F, Trost P, Carpaneto A. Tonoplast cytochrome b561 is a transmembrane ascorbate-dependent monodehydroascorbate reductase: functional characterization of electron currents in plant vacuoles. THE NEW PHYTOLOGIST 2023; 238:1957-1971. [PMID: 36806214 DOI: 10.1111/nph.18823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 02/14/2023] [Indexed: 05/04/2023]
Abstract
Ascorbate (Asc) is a major redox buffer of plant cells, whose antioxidant activity depends on the ratio with its one-electron oxidation product monodehydroascorbate (MDHA). The cytoplasm contains millimolar concentrations of Asc and soluble enzymes that can regenerate Asc from MDHA or fully oxidized dehydroascorbate. Also, vacuoles contain Asc, but no soluble Asc-regenerating enzymes. Here, we show that vacuoles isolated from Arabidopsis mesophyll cells contain a tonoplast electron transport system that works as a reversible, Asc-dependent transmembrane MDHA oxidoreductase. Electron currents were measured by patch-clamp on isolated vacuoles and found to depend on the availability of Asc (electron donor) and ferricyanide or MDHA (electron acceptors) on opposite sides of the tonoplast. Electron currents were catalyzed by cytochrome b561 isoform A (CYB561A), a tonoplast redox protein with cytoplasmic and luminal Asc binding sites. The Km for Asc of the luminal (4.5 mM) and cytoplasmic site (51 mM) reflected the physiological Asc concentrations in these compartments. The maximal current amplitude was similar in both directions. Mutant plants with impaired CYB561A expression showed no detectable trans-tonoplast electron currents and strong accumulation of leaf anthocyanins under excessive illumination, suggesting a redox-modulation exerted by CYB561A on the typical anthocyanin response to high-light stress.
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Affiliation(s)
| | - Laura Lagostena
- Institute of Biophysics - CNR, Via De Marini 6, 16149, Genova, Italy
| | - Sara Beltrami
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Via Irnerio 42, 40126, Bologna, Italy
| | - Edoardo Tosato
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Via Irnerio 42, 40126, Bologna, Italy
| | - Cristiana Picco
- Institute of Biophysics - CNR, Via De Marini 6, 16149, Genova, Italy
| | | | - Francesca Sparla
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Via Irnerio 42, 40126, Bologna, Italy
| | - Paolo Trost
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Via Irnerio 42, 40126, Bologna, Italy
| | - Armando Carpaneto
- Institute of Biophysics - CNR, Via De Marini 6, 16149, Genova, Italy
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132, Genova, Italy
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2
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Hodin J, Lind C, Marmagne A, Espagne C, Bianchi MW, De Angeli A, Abou-Choucha F, Bourge M, Chardon F, Thomine S, Filleur S. Proton exchange by the vacuolar nitrate transporter CLCa is required for plant growth and nitrogen use efficiency. THE PLANT CELL 2023; 35:318-335. [PMID: 36409008 PMCID: PMC9806559 DOI: 10.1093/plcell/koac325] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 11/03/2022] [Indexed: 06/16/2023]
Abstract
Nitrate is a major nutrient and osmoticum for plants. To deal with fluctuating nitrate availability in soils, plants store this nutrient in their vacuoles. Chloride channel a (CLCa), a 2NO3-/1H+ exchanger localized to the vacuole in Arabidopsis (Arabidopsis thaliana), ensures this storage process. CLCa belongs to the CLC family, which includes anion/proton exchangers and anion channels. A mutation in a glutamate residue conserved across CLC exchangers is likely responsible for the conversion of exchangers to channels. Here, we show that CLCa with a mutation in glutamate 203 (E203) behaves as an anion channel in its native membrane. We introduced the CLCaE203A point mutation to investigate its physiological importance into the Arabidopsis clca knockout mutant. These CLCaE203A mutants displayed a growth deficit linked to the disruption of water homeostasis. Additionally, CLCaE203A expression failed to complement the defect in nitrate accumulation of clca and favored higher N-assimilation at the vegetative stage. Further analyses at the post-flowering stages indicated that CLCaE203A expression results in an increase in N uptake allocation to seeds, leading to a higher nitrogen use efficiency compared to the wild-type. Altogether, these results point to the critical function of the CLCa exchanger on the vacuole for plant metabolism and development.
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Affiliation(s)
- Julie Hodin
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, 91198 Gif-sur-Yvette, France
- UFR Sciences du Vivant, Université Paris Cité, F-75205 Paris Cedex 13, France
| | - Christof Lind
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, 91198 Gif-sur-Yvette, France
| | - Anne Marmagne
- AgroParisTech, Institut Jean-Pierre Bourgin (IJPB), Université Paris-Saclay, INRAE, 78000 Versailles, France
| | - Christelle Espagne
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, 91198 Gif-sur-Yvette, France
| | - Michele Wolfe Bianchi
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, 91198 Gif-sur-Yvette, France
- Université Paris-Est-Créteil-Val-de-Marne, 94010 Creteil Cedex, France
| | - Alexis De Angeli
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, 91198 Gif-sur-Yvette, France
| | - Fadi Abou-Choucha
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, 91198 Gif-sur-Yvette, France
| | - Mickaël Bourge
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, 91198 Gif-sur-Yvette, France
| | - Fabien Chardon
- AgroParisTech, Institut Jean-Pierre Bourgin (IJPB), Université Paris-Saclay, INRAE, 78000 Versailles, France
| | - Sebastien Thomine
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, 91198 Gif-sur-Yvette, France
| | - Sophie Filleur
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, 91198 Gif-sur-Yvette, France
- UFR Sciences du Vivant, Université Paris Cité, F-75205 Paris Cedex 13, France
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3
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Dietrich P, Gradogna A, Carpaneto A. The Plant Vacuole as Heterologous System to Characterize the Functional Properties of TPC Channels. Handb Exp Pharmacol 2023; 278:235-247. [PMID: 35879579 DOI: 10.1007/164_2022_604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Human TPC channels are an emerging family of intracellular proteins fundamental for cell physiology and involved in various severe pathologies. Their localization in the membranes of endo-lysosomes, intracellular compartments of submicrometric dimensions, makes their study difficult with usual electrophysiological techniques. In this work, we show how the plant vacuole, a versatile organelle that can occupy up to 90% of the volume in mature plant cells, can be used as a heterologous system of expression for functional characterization. For this purpose, the use of vacuoles isolated from mesophyll cells of the Arabidopsis thaliana mutant lacking the endogenous TPC avoids unwanted interferences. The patch-clamp technique can be successfully applied to plant vacuoles in all different configuration modes; of note, the whole-vacuole configuration allows to study channel modulation by cytosolic factors. The combination of patch-clamp with fluorescence techniques, for example, by using fluorescent probes sensitive to specific ions of interest, represents a useful extension to investigate the selectivity properties of the channels. Therefore, the plant vacuole, similar to Xenopus oocytes for ion channels and transporters localized in the plasma membrane, has the capability to become a model system for functional studies on intracellular ion channels and transporters.
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Affiliation(s)
- P Dietrich
- Lehrstuhl für Molekulare Pflanzenphysiologie, Department Biologie Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | | | - A Carpaneto
- Institute of Biophysics, Genoa, Italy.
- Department of Earth, Environment and Life Sciences (DISTAV) - University of Genoa, Genoa, Italy.
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4
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Minicozzi V, Qi T, Gradogna A, Pozzolini M, Milenkovic S, Filippini A, Ceccarelli M, Carpaneto A. A commentary on the inhibition of human TPC2 channel by the natural flavonoid naringenin: Methods, experiments, and ideas. Biomol Concepts 2023; 14:bmc-2022-0036. [PMID: 37677148 DOI: 10.1515/bmc-2022-0036] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 08/14/2023] [Indexed: 09/09/2023] Open
Abstract
Human endo-lysosomes possess a class of proteins called TPC channels on their membrane, which are essential for proper cell functioning. This protein family can be functionally studied by expressing them in plant vacuoles. Inhibition of hTPC activity by naringenin, one of the main flavonoids present in the human diet, has the potential to be beneficial in severe human diseases such as solid tumor development, melanoma, and viral infections. We attempted to identify the molecular basis of the interaction between hTPC2 and naringenin, using ensemble docking on molecular dynamics (MD) trajectories, but the specific binding site remains elusive, posing a challenge that could potentially be addressed in the future by increased computational power in MD and the combined use of microscopy techniques such as cryo-EM.
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Affiliation(s)
- Velia Minicozzi
- INFN and Department of Physics, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy
| | - Tianwen Qi
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132 Genova, Italy
| | - Antonella Gradogna
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genova, Italy
| | - Marina Pozzolini
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132 Genova, Italy
| | - Stefan Milenkovic
- Department of Physics, University of Cagliari, 09042 Monserrato, Italy
| | - Antonio Filippini
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Unit of Histology and Medical Embryology, Sapienza University, 16 Via A. Scarpa, 00161 Rome, Italy
| | - Matteo Ceccarelli
- Department of Physics, University of Cagliari, 09042 Monserrato, Italy
| | - Armando Carpaneto
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132 Genova, Italy
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genova, Italy
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5
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Gradogna A, Carpaneto A. Electrophysiology and fluorescence to investigate cation channels and transporters in isolated plant vacuoles. STRESS BIOLOGY 2022; 2:42. [PMID: 37676514 PMCID: PMC10442027 DOI: 10.1007/s44154-022-00064-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 09/01/2022] [Indexed: 09/08/2023]
Abstract
The plant vacuole plays a fundamental role in cell homeostasis. The successful application of patch-clamp technique on isolated vacuoles allows the determination of the functional characteristics of tonoplast ion channels and transporters. The parallel use of a sensor-based fluorescence approach capable of detecting changes in calcium and proton concentrations opens up new possibilities for investigation. In excised patch, the presence of fura-2 in the vacuolar solution reveals the direct permeation of calcium in plant TPC channels. In whole-vacuole, the activity of non-electrogenic NHX potassium proton antiporters can be measured by using the proton sensitive dye BCECF loaded in the vacuolar lumen by the patch pipette. Both vacuolar NHXs and CLCa (chloride/nitrate antiporter) are inhibited by the phosphoinositide PI(3,5)P2, suggesting a coordinated role of these proteins in salt accumulation. Increased knowledge in the molecular mechanisms of vacuolar ion channels and transporters has the potential to improve our understanding on how plants cope with a rapidly changing environment.
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Affiliation(s)
- Antonella Gradogna
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149, Genoa, Italy
| | - Armando Carpaneto
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149, Genoa, Italy.
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132, Genoa, Italy.
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6
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Gradogna A, Pardo JM, Carpaneto A. The phosphoinositide PI(3,5)P 2 inhibits the activity of plant NHX proton/potassium antiporters: Advantages of a novel electrophysiological approach. Biomol Concepts 2022; 13:119-125. [DOI: 10.1515/bmc-2022-0009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 02/22/2022] [Indexed: 11/15/2022] Open
Abstract
Abstract
In the present work, we discuss the way in which the parallel application of the patch-clamp technique and the 2′,7′-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) fluorescence detection for recording luminal proton changes allows the functional characterization of nonelectrogenic potassium/proton vacuolar antiporters of the NHX (Na+/H+ exchanger) family. Moreover, we review the functional role of the tonoplast-specific phosphoinositide PI(3,5)P2, able to simultaneously inhibit the activity of NHXs and CLC-a transporters, whose coordinated action can play an important role in the water balance of plant cells.
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Affiliation(s)
- Antonella Gradogna
- Institute of Biophysics, National Research Council , Via De Marini 6 , 16149 Genova , Italy
| | - José M. Pardo
- Institute of Plant Biochemistry and Photosynthesis, Consejo Superior de Investigaciones Cientificas and University of Seville , Seville 41092 , Spain
| | - Armando Carpaneto
- Department of Earth, Environment and Life Sciences (DISTAV) – University of Genoa , Viale Benedetto XV 5 , 16132 Genova , Italy
- Institute of Biophysics, National Research Council , Via De Marini 6 , 16149 Genova , Italy
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7
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Current Methods to Unravel the Functional Properties of Lysosomal Ion Channels and Transporters. Cells 2022; 11:cells11060921. [PMID: 35326372 PMCID: PMC8946281 DOI: 10.3390/cells11060921] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 03/04/2022] [Accepted: 03/05/2022] [Indexed: 02/07/2023] Open
Abstract
A distinct set of channels and transporters regulates the ion fluxes across the lysosomal membrane. Malfunctioning of these transport proteins and the resulting ionic imbalance is involved in various human diseases, such as lysosomal storage disorders, cancer, as well as metabolic and neurodegenerative diseases. As a consequence, these proteins have stimulated strong interest for their suitability as possible drug targets. A detailed functional characterization of many lysosomal channels and transporters is lacking, mainly due to technical difficulties in applying the standard patch-clamp technique to these small intracellular compartments. In this review, we focus on current methods used to unravel the functional properties of lysosomal ion channels and transporters, stressing their advantages and disadvantages and evaluating their fields of applicability.
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8
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Boccaccio A, Picco C, Di Zanni E, Scholz-Starke J. Phospholipid scrambling by a TMEM16 homolog of Arabidopsis thaliana. FEBS J 2021; 289:2578-2592. [PMID: 34775680 PMCID: PMC9299152 DOI: 10.1111/febs.16279] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 09/15/2021] [Accepted: 11/12/2021] [Indexed: 12/20/2022]
Abstract
Membrane asymmetry is important for cellular physiology and established by energy‐dependent unidirectional lipid translocases, which have diverse physiological functions in plants. By contrast, the role of phospholipid scrambling (PLS), the passive bidirectional lipid transfer leading to the break‐down of membrane asymmetry, is currently still unexplored. The Arabidopsis thaliana genome contains a single gene (At1g73020) with homology to the eukaryotic TMEM16 family of Ca2+‐activated phospholipid scramblases. Here, we investigated the protein function of this Arabidopsis homolog. Fluorescent AtTMEM16 fusions localized to the ER both in transiently expressing Arabidopsis protoplasts and HEK293 cells. A putative scrambling domain (SCRD) was identified on the basis of sequence conservation and conferred PLS to transfected HEK293 cells, when grafted into the backbone of the non‐scrambling plasma membrane‐localized TMEM16A chloride channel. Finally, AtTMEM16 ‘gain‐of‐function’ variants gave rise to cellular phenotypes typical of aberrant scramblase activity, which were reversed by the additional introduction of a ‘loss‐of‐function’ mutation into the SCRD. In conclusion, our data suggest AtTMEM16 works as an ER‐resident lipid scramblase in Arabidopsis.
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Affiliation(s)
- Anna Boccaccio
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Cristiana Picco
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Eleonora Di Zanni
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
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9
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Milenkovic S, Bodrenko IV, Carpaneto A, Ceccarelli M. The key role of the central cavity in sodium transport through ligand-gated two-pore channels. Phys Chem Chem Phys 2021; 23:18461-18474. [PMID: 34612386 DOI: 10.1039/d1cp02947a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Subcellular and organellar mechanisms have manifested a prominent importance for a broad variety of processes that maintain cellular life at its most basic level. Mammalian two-pore channels (TPCs) appear to be cornerstones of these processes in endo-lysosomes by controlling delicate ion-concentrations in their interiors. With evolutionary remarkable architecture and one-of-a-kind selectivity filter, TPCs are an extremely attractive topic per se. In the light of the current COVID-19 pandemic, hTPC2 emerges to be more than attractive. As a key regulator of the endocytosis pathway, it is potentially essential for diverse viral infections in humans, as demonstrated. Here, by means of multiscale molecular simulations, we propose a model of sodium transport from the lumen to the cytosol where the central cavity works as a reservoir. Since the inhibition of hTPC2 is proven to stop SARS-CoV2 in vitro, shedding light on the hTPC2 function and mechanism is the first step towards the selection of potential inhibiting candidates.
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Affiliation(s)
- Stefan Milenkovic
- Department of Physics, University of Cagliari, 09042 Monserrato, Italy.
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10
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The Discovery of Naringenin as Endolysosomal Two-Pore Channel Inhibitor and Its Emerging Role in SARS-CoV-2 Infection. Cells 2021; 10:cells10051130. [PMID: 34067054 PMCID: PMC8150892 DOI: 10.3390/cells10051130] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/01/2021] [Accepted: 05/04/2021] [Indexed: 12/23/2022] Open
Abstract
The flavonoid naringenin (Nar), present in citrus fruits and tomatoes, has been identified as a blocker of an emerging class of human intracellular channels, namely the two-pore channel (TPC) family, whose role has been established in several diseases. Indeed, Nar was shown to be effective against neoangiogenesis, a process essential for solid tumor progression, by specifically impairing TPC activity. The goal of the present review is to illustrate the rationale that links TPC channels to the mechanism of coronavirus infection, and how their inhibition by Nar could be an efficient pharmacological strategy to fight the current pandemic plague COVID-19.
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11
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Gradogna A, Scholz-Starke J, Pardo JM, Carpaneto A. Beyond the patch-clamp resolution: functional activity of nonelectrogenic vacuolar NHX proton/potassium antiporters and inhibition by phosphoinositides. THE NEW PHYTOLOGIST 2021; 229:3026-3036. [PMID: 33098586 DOI: 10.1111/nph.17021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 10/12/2020] [Indexed: 05/12/2023]
Abstract
We combined the patch-clamp technique with ratiometric fluorescence imaging using the proton-responsive dye BCECF as a luminal probe. Upon application of a steep cytosol-directed potassium ion (K+ ) gradient in Arabidopsis mesophyll vacuoles, a strong and reversible acidification of the vacuolar lumen was detected, whereas no associated electrical currents were observed, in agreement with electroneutral cation/H+ exchange. Our data show that this acidification was generated by NHX antiport activity, because: it did not distinguish between K+ and sodium (Na+ ) ions; it was sensitive to the NHX inhibitor benzamil; and it was completely absent in vacuoles from nhx1 nhx2 double knockout plants. Our data further show that NHX activity could be reversed, was voltage-independent and specifically impaired by the low-abundance signaling lipid PI(3,5)P2 , which may regulate salt accumulation in plants by acting as a common messenger to coordinately shut down secondary active carriers responsible for cation and anion uptake inside the vacuole. Finally, we developed a theory based on thermodynamics, which supports the data obtained by our novel experimental approach. This work, therefore, represents a proof-of-principle that can be applied to the study of proton-dependent exchangers from plants and animals, which are barely detectable using conventional techniques.
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Affiliation(s)
- Antonella Gradogna
- Institute of Biophysics, National Research Council, Via De Marini 6, Genova, 16149, Italy
| | - Joachim Scholz-Starke
- Institute of Biophysics, National Research Council, Via De Marini 6, Genova, 16149, Italy
| | - José M Pardo
- Institute of Plant Biochemistry and Photosynthesis, CSIC-University of Seville, Seville, 41092, Spain
| | - Armando Carpaneto
- Institute of Biophysics, National Research Council, Via De Marini 6, Genova, 16149, Italy
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, Genova, 16132, Italy
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12
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Schrecker M, Korobenko J, Hite RK. Cryo-EM structure of the lysosomal chloride-proton exchanger CLC-7 in complex with OSTM1. eLife 2020; 9:e59555. [PMID: 32749217 PMCID: PMC7440919 DOI: 10.7554/elife.59555] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 07/29/2020] [Indexed: 01/21/2023] Open
Abstract
The chloride-proton exchanger CLC-7 plays critical roles in lysosomal homeostasis and bone regeneration and its mutation can lead to osteopetrosis, lysosomal storage disease and neurological disorders. In lysosomes and the ruffled border of osteoclasts, CLC-7 requires a β-subunit, OSTM1, for stability and activity. Here, we present electron cryomicroscopy structures of CLC-7 in occluded states by itself and in complex with OSTM1, determined at resolutions up to 2.8 Å. In the complex, the luminal surface of CLC-7 is entirely covered by a dimer of the heavily glycosylated and disulfide-bonded OSTM1, which serves to protect CLC-7 from the degradative environment of the lysosomal lumen. OSTM1 binding does not induce large-scale rearrangements of CLC-7, but does have minor effects on the conformation of the ion-conduction pathway, potentially contributing to its regulatory role. These studies provide insights into the role of OSTM1 and serve as a foundation for understanding the mechanisms of CLC-7 regulation.
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Affiliation(s)
- Marina Schrecker
- Structural Biology Program, Memorial Sloan Kettering Cancer CenterNew YorkUnited States
| | - Julia Korobenko
- Structural Biology Program, Memorial Sloan Kettering Cancer CenterNew YorkUnited States
| | - Richard K Hite
- Structural Biology Program, Memorial Sloan Kettering Cancer CenterNew YorkUnited States
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13
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McKiernan KA, Koster AK, Maduke M, Pande VS. Dynamical model of the CLC-2 ion channel reveals conformational changes associated with selectivity-filter gating. PLoS Comput Biol 2020; 16:e1007530. [PMID: 32226009 PMCID: PMC7145265 DOI: 10.1371/journal.pcbi.1007530] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 04/09/2020] [Accepted: 11/05/2019] [Indexed: 12/18/2022] Open
Abstract
This work reports a dynamical Markov state model of CLC-2 "fast" (pore) gating, based on 600 microseconds of molecular dynamics (MD) simulation. In the starting conformation of our CLC-2 model, both outer and inner channel gates are closed. The first conformational change in our dataset involves rotation of the inner-gate backbone along residues S168-G169-I170. This change is strikingly similar to that observed in the cryo-EM structure of the bovine CLC-K channel, though the volume of the intracellular (inner) region of the ion conduction pathway is further expanded in our model. From this state (inner gate open and outer gate closed), two additional states are observed, each involving a unique rotameric flip of the outer-gate residue GLUex. Both additional states involve conformational changes that orient GLUex away from the extracellular (outer) region of the ion conduction pathway. In the first additional state, the rotameric flip of GLUex results in an open, or near-open, channel pore. The equilibrium population of this state is low (∼1%), consistent with the low open probability of CLC-2 observed experimentally in the absence of a membrane potential stimulus (0 mV). In the second additional state, GLUex rotates to occlude the channel pore. This state, which has a low equilibrium population (∼1%), is only accessible when GLUex is protonated. Together, these pathways model the opening of both an inner and outer gate within the CLC-2 selectivity filter, as a function of GLUex protonation. Collectively, our findings are consistent with published experimental analyses of CLC-2 gating and provide a high-resolution structural model to guide future investigations.
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Affiliation(s)
- Keri A. McKiernan
- Department of Chemistry, Stanford University, Stanford, California, United States of America
| | - Anna K. Koster
- Department of Chemistry, Stanford University, Stanford, California, United States of America
- Department of Molecular & Cellular Physiology, Stanford University, Stanford, California, United States of America
| | - Merritt Maduke
- Department of Molecular & Cellular Physiology, Stanford University, Stanford, California, United States of America
| | - Vijay S. Pande
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
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14
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A perspective on the modulation of plant and animal two pore channels (TPCs) by the flavonoid naringenin. Biophys Chem 2019; 254:106246. [PMID: 31426023 DOI: 10.1016/j.bpc.2019.106246] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 08/03/2019] [Accepted: 08/03/2019] [Indexed: 12/17/2022]
Abstract
The inhibitory effect of the flavonoid naringenin on plant and human Two-Pore Channels (TPCs) was assessed by means of electrophysiological measurements. By acting on human TPC2, naringenin, was able to dampen intracellular calcium responses to VEGF in cultured human endothelial cells and to impair angiogenic activity in VEGF-containing matrigel plugs implanted in mice. Molecular docking predicts selective binding sites for naringenin in the TPC structure, thus suggesting a specific interaction between the flavonoid and the channel.
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15
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Scholz-Starke J, Primo C, Yang J, Kandel R, Gaxiola RA, Hirschi KD. The flip side of the Arabidopsis type I proton-pumping pyrophosphatase (AVP1): Using a transmembrane H + gradient to synthesize pyrophosphate. J Biol Chem 2018; 294:1290-1299. [PMID: 30510138 DOI: 10.1074/jbc.ra118.006315] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 11/29/2018] [Indexed: 01/19/2023] Open
Abstract
Energy partitioning and plant growth are mediated in part by a type I H+-pumping pyrophosphatase (H+-PPase). A canonical role for this transporter has been demonstrated at the tonoplast where it serves a job-sharing role with V-ATPase in vacuolar acidification. Here, we investigated whether the plant H+-PPase from Arabidopsis also functions in "reverse mode" to synthesize PPi using the transmembrane H+ gradient. Using patch-clamp recordings on Arabidopsis vacuoles, we observed inward currents upon Pi application on the cytosolic side. These currents were strongly reduced in vacuoles from two independent H+-PPase mutant lines (vhp1-1 and fugu5-1) lacking the classical PPi-induced outward currents related to H+ pumping, whereas they were significantly larger in vacuoles with engineered heightened expression of the H+-PPase. Current amplitudes related to reverse-mode H+ transport depended on the membrane potential, cytosolic Pi concentration, and magnitude of the pH gradient across the tonoplast. Of note, experiments on vacuolar membrane-enriched vesicles isolated from yeast expressing the Arabidopsis H+-PPase (AVP1) demonstrated Pi-dependent PPi synthase activity in the presence of a pH gradient. Our work establishes that a plant H+-PPase can operate as a PPi synthase beyond its canonical role in vacuolar acidification and cytosolic PPi scavenging. We propose that the PPi synthase activity of H+-PPase contributes to a cascade of events that energize plant growth.
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Affiliation(s)
- Joachim Scholz-Starke
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy.
| | - Cecilia Primo
- Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030
| | - Jian Yang
- Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030
| | - Raju Kandel
- School of Life Sciences, Arizona State University, Tempe, Arizona 85287
| | - Roberto A Gaxiola
- School of Life Sciences, Arizona State University, Tempe, Arizona 85287
| | - Kendal D Hirschi
- Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030.
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16
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Kirsch SA, Kugemann A, Carpaneto A, Böckmann RA, Dietrich P. Phosphatidylinositol-3,5-bisphosphate lipid-binding-induced activation of the human two-pore channel 2. Cell Mol Life Sci 2018; 75:3803-3815. [PMID: 29705952 PMCID: PMC11105763 DOI: 10.1007/s00018-018-2829-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 03/29/2018] [Accepted: 04/23/2018] [Indexed: 11/24/2022]
Abstract
Mammalian two-pore channels (TPCs) are activated by the low-abundance membrane lipid phosphatidyl-(3,5)-bisphosphate (PI(3,5)P2) present in the endo-lysosomal system. Malfunction of human TPC1 or TPC2 (hTPC) results in severe organellar storage diseases and membrane trafficking defects. Here, we compared the lipid-binding characteristics of hTPC2 and of the PI(3,5)P2-insensitive TPC1 from the model plant Arabidopsis thaliana. Combination of simulations with functional analysis of channel mutants revealed the presence of an hTPC2-specific lipid-binding pocket mutually formed by two channel regions exposed to the cytosolic side of the membrane. We showed that PI(3,5)P2 is simultaneously stabilized by positively charged amino acids (K203, K204, and K207) in the linker between transmembrane helices S4 and S5 and by S322 in the cytosolic extension of S6. We suggest that PI(3,5)P2 cross links two parts of the channel, enabling their coordinated movement during channel gating.
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Affiliation(s)
- Sonja A Kirsch
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Andreas Kugemann
- Molecular Plant Physiology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Armando Carpaneto
- Institute of Biophysics, National Research Council, Genoa, Italy
- Department of Earth, Environment and Life Sciences-DISTAV, University of Genoa, Genoa, Italy
| | - Rainer A Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
| | - Petra Dietrich
- Molecular Plant Physiology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
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17
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Böhm J, Messerer M, Müller HM, Scholz-Starke J, Gradogna A, Scherzer S, Maierhofer T, Bazihizina N, Zhang H, Stigloher C, Ache P, Al-Rasheid KAS, Mayer KFX, Shabala S, Carpaneto A, Haberer G, Zhu JK, Hedrich R. Understanding the Molecular Basis of Salt Sequestration in Epidermal Bladder Cells of Chenopodium quinoa. Curr Biol 2018; 28:3075-3085.e7. [PMID: 30245105 DOI: 10.1016/j.cub.2018.08.004] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 06/20/2018] [Accepted: 08/01/2018] [Indexed: 02/03/2023]
Abstract
Soil salinity is destroying arable land and is considered to be one of the major threats to global food security in the 21st century. Therefore, the ability of naturally salt-tolerant halophyte plants to sequester large quantities of salt in external structures, such as epidermal bladder cells (EBCs), is of great interest. Using Chenopodium quinoa, a pseudo-cereal halophyte of great economic potential, we have shown previously that, upon removal of salt bladders, quinoa becomes salt sensitive. In this work, we analyzed the molecular mechanism underlying the unique salt dumping capabilities of bladder cells in quinoa. The transporters differentially expressed in the EBC transcriptome and functional electrophysiological testing of key EBC transporters in Xenopus oocytes revealed that loading of Na+ and Cl- into EBCs is mediated by a set of tailored plasma and vacuole membrane-based sodium-selective channel and chloride-permeable transporter.
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Affiliation(s)
- Jennifer Böhm
- Tasmanian Institute for Agriculture, College of Science and Engineering, University of Tasmania, Private Bag 54, Hobart, TAS 7001, Australia
| | - Maxim Messerer
- Plant Genome and Systems Biology, Helmholtz Center Munich, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | - Heike M Müller
- Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs Platz 2, 97082 Wuerzburg, Germany
| | - Joachim Scholz-Starke
- Institute of Biophysics, National Research Council (CNR), Via De Marini 6, 16149 Genova, Italy
| | - Antonella Gradogna
- Institute of Biophysics, National Research Council (CNR), Via De Marini 6, 16149 Genova, Italy
| | - Sönke Scherzer
- Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs Platz 2, 97082 Wuerzburg, Germany
| | - Tobias Maierhofer
- Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs Platz 2, 97082 Wuerzburg, Germany
| | - Nadia Bazihizina
- Tasmanian Institute for Agriculture, College of Science and Engineering, University of Tasmania, Private Bag 54, Hobart, TAS 7001, Australia; Department of Agrifood Production and Environmental Sciences, Università degli Studi di Firenze, Viale delle Idee 30, 50019 Sesto Fiorentino, Florence, Italy
| | - Heng Zhang
- Shanghai Center for Plant Stress Biology, and CAS Center for Excellence in Molecular Plant Sciences, 3888 Chenhua Road, Shanghai 201602, China
| | - Christian Stigloher
- Imaging Core Facility, Biocenter, University of Wuerzburg, Am Hubland, 97074 Wuerzburg, Germany
| | - Peter Ache
- Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs Platz 2, 97082 Wuerzburg, Germany
| | - Khaled A S Al-Rasheid
- Zoology Department, College of Science, King Saud University, PO Box 2455, Riyadh 11451, Saudi Arabia
| | - Klaus F X Mayer
- Plant Genome and Systems Biology, Helmholtz Center Munich, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | - Sergey Shabala
- Tasmanian Institute for Agriculture, College of Science and Engineering, University of Tasmania, Private Bag 54, Hobart, TAS 7001, Australia; Department of Horticulture, Foshan University, Foshan 528000, PRC
| | - Armando Carpaneto
- Institute of Biophysics, National Research Council (CNR), Via De Marini 6, 16149 Genova, Italy; Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132 Genova, Italy
| | - Georg Haberer
- Plant Genome and Systems Biology, Helmholtz Center Munich, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
| | - Jian-Kang Zhu
- Shanghai Center for Plant Stress Biology, and CAS Center for Excellence in Molecular Plant Sciences, 3888 Chenhua Road, Shanghai 201602, China; Department of Horticulture and Landscape Architecture, Purdue University, 625 Agriculture Mall Drive, West Lafayette, IN 47907, USA.
| | - Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs Platz 2, 97082 Wuerzburg, Germany.
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18
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Tadini L, Ferrari R, Lehniger MK, Mizzotti C, Moratti F, Resentini F, Colombo M, Costa A, Masiero S, Pesaresi P. Trans-splicing of plastid rps12 transcripts, mediated by AtPPR4, is essential for embryo patterning in Arabidopsis thaliana. PLANTA 2018; 248:257-265. [PMID: 29687222 DOI: 10.1007/s00425-018-2896-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 04/17/2018] [Indexed: 05/21/2023]
Abstract
AtPPR4-mediated trans-splicing of plastid rps12 transcripts is essential for key embryo morphogenetic events such as development of cotyledons, determination of provascular tissue, and organization of the shoot apical meristem (SAM), but not for the formation of the protodermal layer. Members of the pentatricopeptide repeat (PPR) containing protein family have emerged as key regulators of the organelle post-transcriptional processing and to be essential for proper plant embryo development. In this study, we report the functional characterization of the AtPPR4 (At5g04810) gene encoding a plastid nucleoid PPR protein. In-situ hybridization analysis reveals the presence of AtPPR4 transcripts already at the transition stage of embryo development. As a consequence, embryos lacking the AtPPR4 protein arrest their development at the transition/early-heart stages and show defects in the determination of the provascular tissue and organization of SAM. This complex phenotype is due to the specific role of AtPPR4 in the trans-splicing of the plastid rps12 transcripts, as shown by northern and slot-blot hybridizations, and the consequent defect in 70S ribosome accumulation and plastid protein synthesis, in agreement with the role proposed for the maize orthologue, ZmPPR4.
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Affiliation(s)
- Luca Tadini
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | - Roberto Ferrari
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | - Marie-Kristin Lehniger
- Molecular Genetics, Institute of Biology, Humboldt University of Berlin, Berlin, Germany
| | - Chiara Mizzotti
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | - Fabio Moratti
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
| | - Francesca Resentini
- Instituto de Biologıa Molecular y Celular de Plantas (CSIC-Universidad Politécnica de Valencia), Valencia, Spain
| | - Monica Colombo
- Centro Ricerca e Innovazione, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - Alex Costa
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | - Simona Masiero
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy.
| | - Paolo Pesaresi
- Dipartimento di Scienze Agrarie e Ambientali - Produzione, Territorio, Agroenergia, Università degli studi di Milano, Milan, Italy.
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19
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Carpaneto A, Gradogna A. Modulation of calcium and potassium permeation in plant TPC channels. Biophys Chem 2018; 236:1-7. [PMID: 29486387 DOI: 10.1016/j.bpc.2018.02.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Revised: 02/20/2018] [Accepted: 02/20/2018] [Indexed: 01/01/2023]
Abstract
Plant two-pore channels (TPCs) are non-selective cation channels permeable both to monovalent potassium and divalent calcium. We previously developed a technique that allowed the simultaneous determination of the fluxes of these two ions across the channel by a combined use of patch-clamp and fluorescence. In this paper we studied how potassium and calcium fluxes were influenced by modification of cytosolic concentrations of K+ and Ca2+. A decrease in cytosolic calcium from 2 to 0.5 mM led to a shift of the activation curve of about +60 mV; although at positive potentials currents were very similar, calcium ion permeation was significantly reduced and the ratio between the total and calcium-mediated current increased about two-fold. Upon removal of cytosolic potassium, in the presence of 2 mM cytosolic calcium, the voltage-dependent activation curve was not modified but a dramatic reduction of the currents at positive voltages was apparent. However, calcium permeation did not change significantly in this condition. This work demonstrated that the electrophysiological measurements alone were not capable to predict the extent of the flow of different ions through cation channels. The parallel use of calcium detection by fluorescent dyes proved to be a valuable tool for the correct quantification of the permeation mechanisms in non-selective ion channels.
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Affiliation(s)
- Armando Carpaneto
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132 Genova, Italy; Institute of Biophysics, CNR, Via De Marini 6, 16149 Genova, Italy.
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20
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Electron current recordings in living cells. Biophys Chem 2017; 229:57-61. [DOI: 10.1016/j.bpc.2017.05.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 05/16/2017] [Accepted: 05/16/2017] [Indexed: 11/22/2022]
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21
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Naringenin Impairs Two-Pore Channel 2 Activity And Inhibits VEGF-Induced Angiogenesis. Sci Rep 2017; 7:5121. [PMID: 28698624 PMCID: PMC5505983 DOI: 10.1038/s41598-017-04974-1] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 05/23/2017] [Indexed: 12/11/2022] Open
Abstract
Our research introduces the natural flavonoid naringenin as a novel inhibitor of an emerging class of intracellular channels, Two-Pore Channel 2 (TPC2), as shown by electrophysiological evidence in a heterologous system, i.e. Arabidopsis vacuoles lacking endogenous TPCs. In view of the control exerted by TPC2 on intracellular calcium signaling, we demonstrated that naringenin dampens intracellular calcium responses of human endothelial cells stimulated with VEGF, histamine or NAADP-AM, but not with ATP or Angiopoietin-1 (negative controls). The ability of naringenin to impair TPC2-dependent biological activities was further explored in an established in vivo model, in which VEGF-containing matrigel plugs implanted in mice failed to be vascularized in the presence of naringenin. Overall, the present data suggest that naringenin inhibition of TPC2 activity and the observed inhibition of angiogenic response to VEGF are linked by impaired intracellular calcium signaling. TPC2 inhibition is emerging as a key therapeutic step in a range of important pathological conditions including the progression and metastatic potential of melanoma, Parkinson’s disease, and Ebola virus infection. The identification of naringenin as an inhibitor of TPC2-mediated signaling provides a novel and potentially relevant tool for the advancement of this field of research.
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22
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Carpaneto A, Boccaccio A, Lagostena L, Di Zanni E, Scholz-Starke J. The signaling lipid phosphatidylinositol-3,5-bisphosphate targets plant CLC-a anion/H + exchange activity. EMBO Rep 2017; 18:1100-1107. [PMID: 28536248 DOI: 10.15252/embr.201643814] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 04/20/2017] [Accepted: 04/21/2017] [Indexed: 12/21/2022] Open
Abstract
Phosphatidylinositol-3,5-bisphosphate (PI(3,5)P2) is a low-abundance signaling lipid associated with endo-lysosomal and vacuolar membranes in eukaryotic cells. Recent studies on Arabidopsis indicated a critical role of PI(3,5)P2 in vacuolar acidification and morphology during ABA-induced stomatal closure, but the molecular targets in plant cells remained unknown. By using patch-clamp recordings on Arabidopsis vacuoles, we show here that PI(3,5)P2 does not affect the activity of vacuolar H+-pyrophosphatase or vacuolar H+-ATPase. Instead, PI(3,5)P2 at low nanomolar concentrations inhibited an inwardly rectifying conductance, which appeared upon vacuolar acidification elicited by prolonged H+ pumping activity. We provide evidence that this novel conductance is mediated by chloride channel a (CLC-a), a member of the anion/H+ exchanger family formerly implicated in stomatal movements in Arabidopsis H+-dependent currents were absent in clc-a knock-out vacuoles, and canonical CLC-a-dependent nitrate/H+ antiport was inhibited by low concentrations of PI(3,5)P2 Finally, using the pH indicator probe BCECF, we show that CLC-a inhibition contributes to vacuolar acidification. These data provide a mechanistic explanation for the essential role of PI(3,5)P2 and advance our knowledge about the regulation of vacuolar ion transport.
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Affiliation(s)
- Armando Carpaneto
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Anna Boccaccio
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Laura Lagostena
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Eleonora Di Zanni
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
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23
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Lagostena L, Festa M, Pusch M, Carpaneto A. The human two-pore channel 1 is modulated by cytosolic and luminal calcium. Sci Rep 2017; 7:43900. [PMID: 28252105 PMCID: PMC5333365 DOI: 10.1038/srep43900] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 01/30/2017] [Indexed: 02/03/2023] Open
Abstract
Two-pore channels (TPC) are intracellular endo-lysosomal proteins with only recently emerging roles in organellar signalling and involvement in severe human diseases. Here, we investigated the functional properties of human TPC1 expressed in TPC-free vacuoles from Arabidopsis thaliana cells. Large (20 pA/pF) TPC1 currents were elicited by cytosolic addition of the phosphoinositide phosphatidylinositol-(3,5)-bisphosphate (PI(3,5)P2) with an apparent binding constant of ~15 nM. The channel is voltage-dependent, activating at positive potentials with single exponential kinetics and currents are Na+ selective, with measurable but low permeability to Ca2+. Cytosolic Ca2+ modulated hTPC1 in dual way: low μM cytosolic Ca2+ increased activity by shifting the open probability towards negative voltages and by accelerating the time course of activation. This mechanism was well-described by an allosteric model. Higher levels of cytosolic Ca2+ induced a voltage-dependent decrease of the currents compatible with Ca2+ binding in the permeation pore. Conversely, an increase in luminal Ca2+ decreased hTPC1 activity. Our data point to a process in which Ca2+ permeation in hTPC1 has a positive feedback on channel activity while Na+ acts as a negative regulator. We speculate that the peculiar Ca2+ and Na+ dependence are key for the physiological roles of the channel in organellar homeostasis and signalling.
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Affiliation(s)
- Laura Lagostena
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genova, Italy
| | - Margherita Festa
- Department of Biosciences, University of Milano, Via Celoria, 26, 20133 Milano, Italy
| | - Michael Pusch
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genova, Italy
| | - Armando Carpaneto
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genova, Italy
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24
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Ferrari R, Tadini L, Moratti F, Lehniger MK, Costa A, Rossi F, Colombo M, Masiero S, Schmitz-Linneweber C, Pesaresi P. CRP1 Protein: (dis)similarities between Arabidopsis thaliana and Zea mays. FRONTIERS IN PLANT SCIENCE 2017; 8:163. [PMID: 28261232 PMCID: PMC5309229 DOI: 10.3389/fpls.2017.00163] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 01/26/2017] [Indexed: 05/25/2023]
Abstract
Biogenesis of chloroplasts in higher plants is initiated from proplastids, and involves a series of processes by which a plastid able to perform photosynthesis, to synthesize amino acids, lipids, and phytohormones is formed. All plastid protein complexes are composed of subunits encoded by the nucleus and chloroplast genomes, which require a coordinated gene expression to produce the correct concentrations of organellar proteins and to maintain organelle function. To achieve this, hundreds of nucleus-encoded factors are imported into the chloroplast to control plastid gene expression. Among these factors, members of the Pentatricopeptide Repeat (PPR) containing protein family have emerged as key regulators of the organellar post-transcriptional processing. PPR proteins represent a large family in plants, and the extent to which PPR functions are conserved between dicots and monocots deserves evaluation, in light of differences in photosynthetic metabolism (C3 vs. C4) and localization of chloroplast biogenesis (mesophyll vs. bundle sheath cells). In this work we investigated the role played in the process of chloroplast biogenesis by At5g42310, a member of the Arabidopsis PPR family which we here refer to as AtCRP1 (Chloroplast RNA Processing 1), providing a comparison with the orthologous ZmCRP1 protein from Zea mays. Loss-of-function atcrp1 mutants are characterized by yellow-albinotic cotyledons and leaves owing to defects in the accumulation of subunits of the thylakoid protein complexes. As in the case of ZmCRP1, AtCRP1 associates with the 5' UTRs of both psaC and, albeit very weakly, petA transcripts, indicating that the role of CRP1 as regulator of chloroplast protein synthesis has been conserved between maize and Arabidopsis. AtCRP1 also interacts with the petB-petD intergenic region and is required for the generation of petB and petD monocistronic RNAs. A similar role has been also attributed to ZmCRP1, although the direct interaction of ZmCRP1 with the petB-petD intergenic region has never been reported, which could indicate that AtCRP1 and ZmCRP1 differ, in part, in their plastid RNA targets.
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Affiliation(s)
- Roberto Ferrari
- Dipartimento di Bioscienze, Università degli studi di MilanoMilano, Italy
| | - Luca Tadini
- Dipartimento di Bioscienze, Università degli studi di MilanoMilano, Italy
| | - Fabio Moratti
- Max-Planck-Institut für Molekulare PflanzenphysiologiePotsdam-Golm, Germany
| | | | - Alex Costa
- Dipartimento di Bioscienze, Università degli studi di MilanoMilano, Italy
| | - Fabio Rossi
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli studi di MilanoMilano, Italy
| | - Monica Colombo
- Centro Ricerca e Innovazione, Fondazione Edmund MachSan Michele all’Adige, Italy
| | - Simona Masiero
- Dipartimento di Bioscienze, Università degli studi di MilanoMilano, Italy
| | | | - Paolo Pesaresi
- Dipartimento di Scienze Agrarie e Ambientali - Produzione, Territorio, Agroenergia, Università degli studi di MilanoMilano, Italy
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25
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Barrallo-Gimeno A, Gradogna A, Zanardi I, Pusch M, Estévez R. Regulatory-auxiliary subunits of CLC chloride channel-transport proteins. J Physiol 2016; 593:4111-27. [PMID: 25762128 DOI: 10.1113/jp270057] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 02/15/2015] [Indexed: 02/06/2023] Open
Abstract
The CLC family of chloride channels and transporters is composed by nine members, but only three of them, ClC-Ka/b, ClC-7 and ClC-2, have been found so far associated with auxiliary subunits. These CLC regulatory subunits are small proteins that present few common characteristics among them, both structurally and functionally, and their effects on the corresponding CLC protein are different. Barttin, a protein with two transmembrane domains, is essential for the membrane localization of ClC-K proteins and their activity in the kidney and inner ear. Ostm1 is a protein with a single transmembrane domain and a highly glycosylated N-terminus. Unlike the other two CLC auxiliary subunits, Ostm1 shows a reciprocal relationship with ClC-7 for their stability. The subcellular localization of Ostm1 depends on ClC-7 and not the other way around. ClC-2 is active on its own, but GlialCAM, a transmembrane cell adhesion molecule with two extracellular immunoglobulin (Ig)-like domains, regulates its subcellular localization and activity in glial cells. The common theme for these three proteins is their requirement for a proper homeostasis, since their malfunction leads to distinct diseases. We will review here their properties and their role in normal chloride physiology and the pathological consequences of their improper function.
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Affiliation(s)
- Alejandro Barrallo-Gimeno
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, University of Barcelona, Barcelona, Spain.,U-750, Centro de investigación en red de enfermedades raras (CIBERER), ISCIII, Barcelona, Spain
| | | | - Ilaria Zanardi
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genoa, Italy
| | - Michael Pusch
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genoa, Italy
| | - Raúl Estévez
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, University of Barcelona, Barcelona, Spain.,U-750, Centro de investigación en red de enfermedades raras (CIBERER), ISCIII, Barcelona, Spain
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26
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Picco C, Scholz-Starke J, Festa M, Costa A, Sparla F, Trost P, Carpaneto A. Direct Recording of Trans-Plasma Membrane Electron Currents Mediated by a Member of the Cytochrome b561 Family of Soybean. PLANT PHYSIOLOGY 2015; 169:986-95. [PMID: 26282237 PMCID: PMC4587454 DOI: 10.1104/pp.15.00642] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 08/12/2015] [Indexed: 05/20/2023]
Abstract
Trans-plasma membrane electron transfer is achieved by b-type cytochromes of different families, and plays a fundamental role in diverse cellular processes involving two interacting redox couples that are physically separated by a phospholipid bilayer, such as iron uptake and redox signaling. Despite their importance, no direct recordings of trans-plasma membrane electron currents have been described in plants. In this work, we provide robust electrophysiological evidence of trans-plasma membrane electron flow mediated by a soybean (Glycine max) cytochrome b561 associated with a dopamine β-monooxygenase redox domain (CYBDOM), which localizes to the plasma membrane in transgenic Arabidopsis (Arabidopsis thaliana) plants and CYBDOM complementary RNA-injected Xenopus laevis oocytes. In oocytes, two-electrode voltage clamp experiments showed that CYBDOM-mediated currents were activated by extracellular electron acceptors in a concentration- and type-specific manner. Current amplitudes were voltage dependent, strongly potentiated in oocytes preinjected with ascorbate (the canonical electron donor for cytochrome b561), and abolished by mutating a highly conserved His residue (H292L) predicted to coordinate the cytoplasmic heme b group. We believe that this unique approach opens new perspectives in plant transmembrane electron transport and beyond.
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Affiliation(s)
- Cristiana Picco
- Institute of Biophysics, Consiglio National Research Council, 16149 Genova, Italy (C.P., J.S.-S., M.F., A.Ca.);Department of Biosciences, University of Milan, 20133 Milan, Italy (A.Co.);Institute of Biophysics, Consiglio Nazionale delle Ricerche, 20133 Milan, Italy (A.Co.); andDepartment of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy (F.S., P.T.)
| | - Joachim Scholz-Starke
- Institute of Biophysics, Consiglio National Research Council, 16149 Genova, Italy (C.P., J.S.-S., M.F., A.Ca.);Department of Biosciences, University of Milan, 20133 Milan, Italy (A.Co.);Institute of Biophysics, Consiglio Nazionale delle Ricerche, 20133 Milan, Italy (A.Co.); andDepartment of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy (F.S., P.T.)
| | - Margherita Festa
- Institute of Biophysics, Consiglio National Research Council, 16149 Genova, Italy (C.P., J.S.-S., M.F., A.Ca.);Department of Biosciences, University of Milan, 20133 Milan, Italy (A.Co.);Institute of Biophysics, Consiglio Nazionale delle Ricerche, 20133 Milan, Italy (A.Co.); andDepartment of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy (F.S., P.T.)
| | - Alex Costa
- Institute of Biophysics, Consiglio National Research Council, 16149 Genova, Italy (C.P., J.S.-S., M.F., A.Ca.);Department of Biosciences, University of Milan, 20133 Milan, Italy (A.Co.);Institute of Biophysics, Consiglio Nazionale delle Ricerche, 20133 Milan, Italy (A.Co.); andDepartment of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy (F.S., P.T.)
| | - Francesca Sparla
- Institute of Biophysics, Consiglio National Research Council, 16149 Genova, Italy (C.P., J.S.-S., M.F., A.Ca.);Department of Biosciences, University of Milan, 20133 Milan, Italy (A.Co.);Institute of Biophysics, Consiglio Nazionale delle Ricerche, 20133 Milan, Italy (A.Co.); andDepartment of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy (F.S., P.T.)
| | - Paolo Trost
- Institute of Biophysics, Consiglio National Research Council, 16149 Genova, Italy (C.P., J.S.-S., M.F., A.Ca.);Department of Biosciences, University of Milan, 20133 Milan, Italy (A.Co.);Institute of Biophysics, Consiglio Nazionale delle Ricerche, 20133 Milan, Italy (A.Co.); andDepartment of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy (F.S., P.T.)
| | - Armando Carpaneto
- Institute of Biophysics, Consiglio National Research Council, 16149 Genova, Italy (C.P., J.S.-S., M.F., A.Ca.);Department of Biosciences, University of Milan, 20133 Milan, Italy (A.Co.);Institute of Biophysics, Consiglio Nazionale delle Ricerche, 20133 Milan, Italy (A.Co.); andDepartment of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy (F.S., P.T.)
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Festa M, Lagostena L, Carpaneto A. Using the plant vacuole as a biological system to investigate the functional properties of exogenous channels and transporters. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:607-12. [PMID: 26431786 DOI: 10.1016/j.bbamem.2015.09.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 07/31/2015] [Accepted: 09/25/2015] [Indexed: 01/15/2023]
Abstract
Plant cells possess a large intracellular compartment that animal cells do not, the central vacuole, which has been investigated for a long time. The central vacuole can occupy up to 90% of the cellular volume and, differently from intracellular organelles from animal cells such as lysosomes or endosomes, it is easy to isolate. Because of its large dimension (up to 40 μm diameter) it can be successfully studied using the classical patch-clamp technique. Following the idea that the vacuolar membrane could be used as a convenient model to characterize the functional properties of channel-forming peptides, we verified that the phytotoxic lipodepsipeptide Syringopeptin 25A from Pseudomonas syringae pv syringae was able to form ionic pores in sugar beet vacuoles and we performed a detailed biophysical analysis. Recently, we extended the use of plant vacuoles to the expression and functional characterization of animal intracellular transporters, namely rat CLC-7, and channels, i.e. human TPC2. Since endo-lysosomal transporters and channels are still largely unexplored, principally because their intracellular localization renders them difficult to study, we believe that this novel approach will prove to be a powerful system for the investigation of the molecular mechanisms of exogenous transporters and channels. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.
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Affiliation(s)
- M Festa
- Institute of Biophysics (IBF), CNR, Via De Marini 6, 16149 Genova, Italy
| | - L Lagostena
- Institute of Biophysics (IBF), CNR, Via De Marini 6, 16149 Genova, Italy
| | - A Carpaneto
- Institute of Biophysics (IBF), CNR, Via De Marini 6, 16149 Genova, Italy.
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Boccaccio A, Scholz-Starke J, Hamamoto S, Larisch N, Festa M, Gutla PVK, Costa A, Dietrich P, Uozumi N, Carpaneto A. The phosphoinositide PI(3,5)P₂ mediates activation of mammalian but not plant TPC proteins: functional expression of endolysosomal channels in yeast and plant cells. Cell Mol Life Sci 2014; 71:4275-83. [PMID: 24770793 PMCID: PMC11113638 DOI: 10.1007/s00018-014-1623-2] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 03/18/2014] [Accepted: 03/31/2014] [Indexed: 11/29/2022]
Abstract
Two-pore channel proteins (TPC) encode intracellular ion channels in both animals and plants. In mammalian cells, the two isoforms (TPC1 and TPC2) localize to the endo-lysosomal compartment, whereas the plant TPC1 protein is targeted to the membrane surrounding the large lytic vacuole. Although it is well established that plant TPC1 channels activate in a voltage- and calcium-dependent manner in vitro, there is still debate on their activation under physiological conditions. Likewise, the mode of animal TPC activation is heavily disputed between two camps favoring as activator either nicotinic acid adenine dinucleotide phosphate (NAADP) or the phosphoinositide PI(3,5)P₂. Here, we investigated TPC current responses to either of these second messengers by whole-vacuole patch-clamp experiments on isolated vacuoles of Arabidopsis thaliana. After expression in mesophyll protoplasts from Arabidopsis tpc1 knock-out plants, we detected the Arabidopsis TPC1-EGFP and human TPC2-EGFP fusion proteins at the membrane of the large central vacuole. Bath (cytosolic) application of either NAADP or PI(3,5)P₂ did not affect the voltage- and calcium-dependent characteristics of AtTPC1-EGFP. By contrast, PI(3,5)P₂ elicited large sodium currents in hTPC2-EGFP-containing vacuoles, while NAADP had no such effect. Analogous results were obtained when PI(3,5)P₂ was applied to hTPC2 expressed in baker's yeast giant vacuoles. Our results underscore the fundamental differences in the mode of current activation and ion selectivity between animal and plant TPC proteins and corroborate the PI(3,5)P₂-mediated activation and Na(+) selectivity of mammalian TPC2.
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Affiliation(s)
- Anna Boccaccio
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genoa, Italy
| | - Joachim Scholz-Starke
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genoa, Italy
| | - Shin Hamamoto
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama, Sendai, 980-8579 Japan
| | - Nina Larisch
- Department of Biology, Molecular Plant Physiology and Erlangen Center of Plant Science, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstrasse 5, 91058 Erlangen, Germany
| | - Margherita Festa
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genoa, Italy
| | | | - Alex Costa
- Department of Biology, Università degli Studi di Milano, Via G. Celoria 26, 20133 Milan, Italy
- Milan Division, Institute of Biophysics, National Research Council, Via G. Celoria 26, 20133 Milan, Italy
| | - Petra Dietrich
- Department of Biology, Molecular Plant Physiology and Erlangen Center of Plant Science, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstrasse 5, 91058 Erlangen, Germany
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama, Sendai, 980-8579 Japan
| | - Armando Carpaneto
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genoa, Italy
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Wege S, De Angeli A, Droillard MJ, Kroniewicz L, Merlot S, Cornu D, Gambale F, Martinoia E, Barbier-Brygoo H, Thomine S, Leonhardt N, Filleur S. Phosphorylation of the vacuolar anion exchanger AtCLCa is required for the stomatal response to abscisic acid. Sci Signal 2014; 7:ra65. [PMID: 25005229 DOI: 10.1126/scisignal.2005140] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Eukaryotic anion/proton exchangers of the CLC (chloride channel) family mediate anion fluxes across intracellular membranes. The Arabidopsis thaliana anion/proton exchanger AtCLCa is involved in vacuolar accumulation of nitrate. We investigated the role of AtCLCa in leaf guard cells, a specialized plant epidermal cell that controls gas exchange and water loss through pores called stomata. We showed that AtCLCa not only fulfilled the expected role of accumulating anions in the vacuole during stomatal opening but also mediated anion release during stomatal closure in response to the stress hormone abscisic acid (ABA). We found that this dual role resulted from a phosphorylation-dependent change in the activity of AtCLCa. The protein kinase OST1 (also known as SnRK2.6) is a key signaling player and central regulator in guard cells in response to ABA. Phosphorylation of Thr(38) in the amino-terminal cytoplasmic domain of AtCLCa by OST1 increased the outward anion fluxes across the vacuolar membrane, which are essential for stomatal closure. We provide evidence that bidirectional activities of an intracellular CLC exchanger are physiologically relevant and that phosphorylation regulates the transport mode of this exchanger.
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Affiliation(s)
- Stefanie Wege
- CNRS-UPR 2355, Institut des Sciences du Végétal, Saclay Plant Sciences Labex, Bât. 22, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - Alexis De Angeli
- CNRS-UPR 2355, Institut des Sciences du Végétal, Saclay Plant Sciences Labex, Bât. 22, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France. Istituto di Biofisica, C.N.R., Via De Marini 6, 16149 Genova, Italy. Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland
| | - Marie-Jo Droillard
- CNRS-UPR 2355, Institut des Sciences du Végétal, Saclay Plant Sciences Labex, Bât. 22, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - Laetitia Kroniewicz
- Laboratoire de Biologie du Développement des Plantes, Unité Mixte de Recherche 7265, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille II, Commissariat à l'Energie Atomique Cadarache Bât. 156, 13108 St Paul-lez-Durance, France
| | - Sylvain Merlot
- CNRS-UPR 2355, Institut des Sciences du Végétal, Saclay Plant Sciences Labex, Bât. 22, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - David Cornu
- CNRS-FRC5115, Centre de Recherche de Gif, Imagif, Bât. 21, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - Franco Gambale
- Istituto di Biofisica, C.N.R., Via De Marini 6, 16149 Genova, Italy
| | - Enrico Martinoia
- Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland
| | - Hélène Barbier-Brygoo
- CNRS-UPR 2355, Institut des Sciences du Végétal, Saclay Plant Sciences Labex, Bât. 22, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - Sébastien Thomine
- CNRS-UPR 2355, Institut des Sciences du Végétal, Saclay Plant Sciences Labex, Bât. 22, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
| | - Nathalie Leonhardt
- Laboratoire de Biologie du Développement des Plantes, Unité Mixte de Recherche 7265, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille II, Commissariat à l'Energie Atomique Cadarache Bât. 156, 13108 St Paul-lez-Durance, France
| | - Sophie Filleur
- CNRS-UPR 2355, Institut des Sciences du Végétal, Saclay Plant Sciences Labex, Bât. 22, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France. Université Paris 7 Denis Diderot, U.F.R. Sciences du Vivant, 35 rue Hélène Brion, 75205 Paris Cedex 13, France.
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30
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Ohgi K, Kajiya H, Okamoto F, Nagaoka Y, Onitsuka T, Nagai A, Sakagami R, Okabe K. A novel inhibitory mechanism of nitrogen-containing bisphosphonate on the activity of Cl− extrusion in osteoclasts. Naunyn Schmiedebergs Arch Pharmacol 2013; 386:589-98. [DOI: 10.1007/s00210-013-0857-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 03/18/2013] [Indexed: 11/29/2022]
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31
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Pedrazzini E, Komarova NY, Rentsch D, Vitale A. Traffic Routes and Signals for the Tonoplast. Traffic 2013; 14:622-8. [DOI: 10.1111/tra.12051] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Revised: 01/23/2013] [Accepted: 01/28/2013] [Indexed: 01/17/2023]
Affiliation(s)
- Emanuela Pedrazzini
- Istituto di Biologia e Biotecnologia Agraria; Consiglio Nazionale delle Ricerche; Milano; Italy
| | | | - Doris Rentsch
- Institute of Plant Sciences; University of Bern; Bern; Switzerland
| | - Alessandro Vitale
- Istituto di Biologia e Biotecnologia Agraria; Consiglio Nazionale delle Ricerche; Milano; Italy
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32
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Zanardi I, Zifarelli G, Pusch M. An optical assay of the transport activity of ClC-7. Sci Rep 2013; 3:1231. [PMID: 23390581 PMCID: PMC3565172 DOI: 10.1038/srep01231] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 01/21/2013] [Indexed: 11/09/2022] Open
Abstract
Osteoporosis, characterized by excessive osteoclast mediated bone resorption, affects millions of people worldwide representing a major public health problem. ClC-7 is a chloride-proton exchanger localized in lysosomes and in the resorption lacuna in osteoclasts where it is essential for bone resorption. Thus, drugs targeted at ClC-7 have been proposed for ameliorating osteoporosis. However, functional assays suited for high throughput screening (HTS) of ClC-7 function are lacking. Here we describe two complementary variants of purely optical assays of the transport activity of ClC-7, redirected to the plasma membrane employing a genetically encoded fluorescent Cl−/pH indicator fused to the ClC-7 protein. These simple and robust functional assays of ClC-7 transport are well-suited to be applied in HTS of small-molecule inhibitors and may help to develop drugs suited for the treatment of osteoporosis.
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Affiliation(s)
- Ilaria Zanardi
- Istituto di Biofisica, CNR, Via De Marini 6, 16149 Genoa, Italy
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