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Zaki AM, Çınaroğlu SS, Rahman T, Patel S, Biggin PC. Plasticity of the selectivity filter is essential for permeation in lysosomal TPC2 channels. Proc Natl Acad Sci U S A 2024; 121:e2320153121. [PMID: 39074274 DOI: 10.1073/pnas.2320153121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 06/24/2024] [Indexed: 07/31/2024] Open
Abstract
Two-pore channels are pathophysiologically important Na+- and Ca2+-permeable channels expressed in lysosomes and other acidic organelles. Unlike most other ion channels, their permeability is malleable and ligand-tuned such that when gated by the signaling lipid PI(3,5)P2, they are more Na+-selective than when gated by the Ca2+ mobilizing messenger nicotinic acid adenine dinucleotide phosphate. However, the structural basis that underlies such plasticity and single-channel behavior more generally remains poorly understood. A recent Cryo-electron microscopy (cryo-EM) structure of TPC2 bound to PI(3,5)P2 in a proposed open-channel conformation provided an opportunity to address this via molecular dynamics (MD) simulation. To our surprise, simulations designed to compute conductance through this structure revealed almost no Na+ permeation events even at very high transmembrane voltages. However further MD simulations identified a spontaneous transition to a dramatically different conformation of the selectivity filter that involved expansion and a flip in the orientation of two core asparagine residues. This alternative filter conformation was remarkably stable and allowed Na+ to flow through the channel leading to a conductance estimate that was in very good agreement with direct single-channel measurements. Furthermore, this conformation was more permeable for Na+ over Ca2+. Our results have important ramifications not just for understanding the control of ion selectivity in TPC2 channels but also more broadly in terms of how ion channels discriminate ions.
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Affiliation(s)
- Afroditi-Maria Zaki
- Department of Biochemistry, Structural Bioinformatics and Computational Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Süleyman Selim Çınaroğlu
- Department of Biochemistry, Structural Bioinformatics and Computational Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Taufiq Rahman
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
| | - Sandip Patel
- Department of Cell and Developmental Biology, University College London, London WC1E, 6BT, United Kingdom
| | - Philip C Biggin
- Department of Biochemistry, Structural Bioinformatics and Computational Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
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2
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Hu Y, Dai Z, Huang J, Han M, Wang Z, Jiao W, Gao Z, Liu X, Liu L, Ma Z. Genome-wide identification and expression analysis of the glutamate receptor gene family in sweet potato and its two diploid relatives. FRONTIERS IN PLANT SCIENCE 2023; 14:1255805. [PMID: 38179475 PMCID: PMC10764598 DOI: 10.3389/fpls.2023.1255805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Accepted: 11/06/2023] [Indexed: 01/06/2024]
Abstract
Plant glutamate receptor (GLR) homologs are crucial calcium channels that play an important role in plant development, signal transduction, and response to biotic and abiotic stresses. However, the GLR gene family has not yet been thoroughly and systematically studied in sweet potato. In this study, a total of 37 GLR genes were identified in the cultivated hexaploid sweet potato (Ipomoea batatas), and 32 GLR genes were discovered in each of the two diploid relatives (Ipomoea trifida and Ipomoea triloba) for the first time. Based on their evolutionary relationships to those of Arabidopsis, these GLRs were split into five subgroups. We then conducted comprehensive analysis to explore their physiological properties, protein interaction networks, promoter cis-elements, chromosomal placement, gene structure, and expression patterns. The results indicate that the homologous GLRs of the cultivated hexaploid sweet potato and its two relatives are different. These variations are reflected in their functions related to plant growth, hormonal crosstalk, development of tuberous roots, resistance to root rot, and responses to abiotic stress factors, all of which are governed by specific individual GLR genes. This study offers a comprehensive analysis of GLR genes in sweet potato and its two diploid relatives. It also provides a theoretical basis for future research into their regulatory mechanisms, significantly influencing the field of molecular breeding in sweet potatoes.
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Affiliation(s)
- Yaya Hu
- Hebei Key Laboratory of Crop Genetics and Breeding, Institute of Cereal and Oil Crops, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang, Hebei, China
| | - Zhuoru Dai
- Key Laboratory of Sweet Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, College of Agronomy & Biotechnology, China Agricultural University, Beijing, China
| | - Jinan Huang
- Hebei Key Laboratory of Crop Genetics and Breeding, Institute of Cereal and Oil Crops, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang, Hebei, China
| | - Meikun Han
- Hebei Key Laboratory of Crop Genetics and Breeding, Institute of Cereal and Oil Crops, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang, Hebei, China
| | - Zhiwei Wang
- Department of Agriculture Forestry and Biological Engineering, Baoding Vocational and Technical College, Baoding, Hebei, China
| | - Weijing Jiao
- Hebei Key Laboratory of Crop Genetics and Breeding, Institute of Cereal and Oil Crops, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang, Hebei, China
| | - Zhiyuan Gao
- Hebei Key Laboratory of Crop Genetics and Breeding, Institute of Cereal and Oil Crops, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang, Hebei, China
| | - Xinliang Liu
- School of Life Sciences, Jiangsu Normal University, Xuzhou, Jiangsu, China
| | - Lanfu Liu
- Hebei Key Laboratory of Crop Genetics and Breeding, Institute of Cereal and Oil Crops, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang, Hebei, China
| | - Zhimin Ma
- Hebei Key Laboratory of Crop Genetics and Breeding, Institute of Cereal and Oil Crops, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang, Hebei, China
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Lu J, Dreyer I, Dickinson MS, Panzer S, Jaślan D, Navarro-Retamal C, Geiger D, Terpitz U, Becker D, Stroud RM, Marten I, Hedrich R. Vicia faba SV channel VfTPC1 is a hyperexcitable variant of plant vacuole Two Pore Channels. eLife 2023; 12:e86384. [PMID: 37991833 PMCID: PMC10665017 DOI: 10.7554/elife.86384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 10/12/2023] [Indexed: 11/23/2023] Open
Abstract
To fire action-potential-like electrical signals, the vacuole membrane requires the two-pore channel TPC1, formerly called SV channel. The TPC1/SV channel functions as a depolarization-stimulated, non-selective cation channel that is inhibited by luminal Ca2+. In our search for species-dependent functional TPC1 channel variants with different luminal Ca2+ sensitivity, we found in total three acidic residues present in Ca2+ sensor sites 2 and 3 of the Ca2+-sensitive AtTPC1 channel from Arabidopsis thaliana that were neutral in its Vicia faba ortholog and also in those of many other Fabaceae. When expressed in the Arabidopsis AtTPC1-loss-of-function background, wild-type VfTPC1 was hypersensitive to vacuole depolarization and only weakly sensitive to blocking luminal Ca2+. When AtTPC1 was mutated for these VfTPC1-homologous polymorphic residues, two neutral substitutions in Ca2+ sensor site 3 alone were already sufficient for the Arabidopsis At-VfTPC1 channel mutant to gain VfTPC1-like voltage and luminal Ca2+ sensitivity that together rendered vacuoles hyperexcitable. Thus, natural TPC1 channel variants exist in plant families which may fine-tune vacuole excitability and adapt it to environmental settings of the particular ecological niche.
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Affiliation(s)
- Jinping Lu
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
- School of Life Sciences, Zhengzhou UniversityZhengzhouChina
| | - Ingo Dreyer
- Universidad de Talca, Faculty of Engineering, Center of Bioinformatics, Simulation and ModelingTalcaChile
| | - Miles Sasha Dickinson
- University of California San Francisco, Department of Biochemistry and BiophysicsSan FranciscoUnited States
| | - Sabine Panzer
- Julius-Maximilians-Universität (JMU), Biocenter, Theodor-Boveri-Institute, Department of Biotechnology and BiophysicsWürzburgGermany
| | - Dawid Jaślan
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
- Ludwig Maximilians-Universität, Faculty of Medicine, Walther Straub Institute of Pharmacology and ToxicologyMunichGermany
| | - Carlos Navarro-Retamal
- Universidad de Talca, Faculty of Engineering, Center of Bioinformatics, Simulation and ModelingTalcaChile
- Department of Cell Biology and Molecular Genetics, University of MarylandCollege ParkUnited States
| | - Dietmar Geiger
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
| | - Ulrich Terpitz
- Julius-Maximilians-Universität (JMU), Biocenter, Theodor-Boveri-Institute, Department of Biotechnology and BiophysicsWürzburgGermany
| | - Dirk Becker
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
| | - Robert M Stroud
- University of California San Francisco, Department of Biochemistry and BiophysicsSan FranciscoUnited States
| | - Irene Marten
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
| | - Rainer Hedrich
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
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Hedrich R, Müller TD, Marten I, Becker D. TPC1 vacuole SV channel gains further shape - voltage priming of calcium-dependent gating. TRENDS IN PLANT SCIENCE 2023; 28:673-684. [PMID: 36740491 DOI: 10.1016/j.tplants.2023.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 12/20/2022] [Accepted: 01/11/2023] [Indexed: 05/13/2023]
Abstract
Across phyla, voltage-gated ion channels (VGICs) allow excitability. The vacuolar two-pore channel AtTPC1 from the tiny mustard plant Arabidopsis thaliana has emerged as a paradigm for deciphering the role of voltage and calcium signals in membrane excitation. Among the numerous experimentally determined structures of VGICs, AtTPC1 was the first to be revealed in a closed and resting state, fueling speculation about structural rearrangements during channel activation. Two independent reports on the structure of a partially opened AtTPC1 channel protein have led to working models that offer promising insights into the molecular switches associated with the gating process. We review new structure-function models and also discuss the evolutionary impact of two-pore channels (TPCs) on K+ homeostasis and vacuolar excitability.
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Affiliation(s)
- Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany.
| | - Thomas D Müller
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany
| | - Irene Marten
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany
| | - Dirk Becker
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany
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Mérida-Quesada F, Vergara-Valladares F, Rubio-Meléndez ME, Hernández-Rojas N, González-González A, Michard E, Navarro-Retamal C, Dreyer I. TPC1-Type Channels in Physcomitrium patens: Interaction between EF-Hands and Ca 2. PLANTS (BASEL, SWITZERLAND) 2022; 11:plants11243527. [PMID: 36559639 PMCID: PMC9783492 DOI: 10.3390/plants11243527] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 05/26/2023]
Abstract
Two-pore channels (TPCs) are members of the superfamily of ligand-gated and voltage-sensitive ion channels in the membranes of intracellular organelles of eukaryotic cells. The evolution of ordinary plant TPC1 essentially followed a very conservative pattern, with no changes in the characteristic structural footprints of these channels, such as the cytosolic and luminal regions involved in Ca2+ sensing. In contrast, the genomes of mosses and liverworts encode also TPC1-like channels with larger variations at these sites (TPC1b channels). In the genome of the model plant Physcomitrium patens we identified nine non-redundant sequences belonging to the TPC1 channel family, two ordinary TPC1-type, and seven TPC1b-type channels. The latter show variations in critical amino acids in their EF-hands essential for Ca2+ sensing. To investigate the impact of these differences between TPC1 and TPC1b channels, we generated structural models of the EF-hands of PpTPC1 and PpTPC1b channels. These models were used in molecular dynamics simulations to determine the frequency with which calcium ions were present in a coordination site and also to estimate the average distance of the ions from the center of this site. Our analyses indicate that the EF-hand domains of PpTPC1b-type channels have a lower capacity to coordinate calcium ions compared with those of common TPC1-like channels.
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Affiliation(s)
- Franko Mérida-Quesada
- Programa de Doctorado en Ciencias mención Modelado de Sistemas Químicos y Biológicos, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
| | - Fernando Vergara-Valladares
- Programa de Doctorado en Ciencias mención Modelado de Sistemas Químicos y Biológicos, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
| | - María Eugenia Rubio-Meléndez
- Electrical Signaling in Plants (ESP) Laboratory–Centro de Bioinformática y Simulación Molecular (CBSM), Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
| | - Naomí Hernández-Rojas
- Electrical Signaling in Plants (ESP) Laboratory–Centro de Bioinformática y Simulación Molecular (CBSM), Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
| | - Angélica González-González
- Programa de Doctorado en Ciencias mención Biología Vegetal y Biotecnología, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
- Instituto de Ciencias Biológicas, Universidad de Talca, Campus Talca, Avenida Lircay, Talca CL-3460000, Chile
| | - Erwan Michard
- Instituto de Ciencias Biológicas, Universidad de Talca, Campus Talca, Avenida Lircay, Talca CL-3460000, Chile
| | - Carlos Navarro-Retamal
- Instituto de Ciencias Biológicas, Universidad de Talca, Campus Talca, Avenida Lircay, Talca CL-3460000, Chile
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742-5815, USA
| | - Ingo Dreyer
- Electrical Signaling in Plants (ESP) Laboratory–Centro de Bioinformática y Simulación Molecular (CBSM), Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
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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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7
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Dreyer I. Specialty grand challenge in plant biophysics and modeling. FRONTIERS IN PLANT SCIENCE 2022; 13:991526. [PMID: 36119613 PMCID: PMC9478854 DOI: 10.3389/fpls.2022.991526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 08/19/2022] [Indexed: 06/15/2023]
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Pottosin I, Dobrovinskaya O. Major vacuolar TPC1 channel in stress signaling: what matters, K +, Ca 2+ conductance or an ion-flux independent mechanism? STRESS BIOLOGY 2022; 2:31. [PMID: 37676554 PMCID: PMC10441842 DOI: 10.1007/s44154-022-00055-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 07/29/2022] [Indexed: 09/08/2023]
Abstract
Two-pore cation channel, TPC1, is ubiquitous in the vacuolar membrane of terrestrial plants and mediates the long distance signaling upon biotic and abiotic stresses. It possesses a wide pore, which transports small mono- and divalent cations. K+ is transported more than 10-fold faster than Ca2+, which binds with a higher affinity within the pore. Key pore residues, responsible for Ca2+ binding, have been recently identified. There is also a substantial progress in the mechanistic and structural understanding of the plant TPC1 gating by membrane voltage and cytosolic and luminal Ca2+. Collectively, these gating factors at resting conditions strongly reduce the potentially lethal Ca2+ leak from the vacuole. Such tight control is impressive, bearing in mind high unitary conductance of the TPC1 and its abundance, with thousands of active channel copies per vacuole. But it remains a mystery how this high threshold is overcome upon signaling, and what type of signal is emitted by TPC1, whether it is Ca2+ or electrical one, or a transduction via protein conformational change, independent on ion conductance. Here we discuss non-exclusive scenarios for the TPC1 integration into Ca2+, ROS and electrical signaling.
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Affiliation(s)
- Igor Pottosin
- Biomedical Center, University of Colima, 28045, Colima, Mexico.
- International Research Centre for Environmental Membrane Biology, Foshan University, Foshan, 528041, China.
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