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Muccioli S, Brillo V, Varanita T, Rossin F, Zaltron E, Velle A, Alessio G, Angi B, Severin F, Tosi A, D'Eletto M, Occhigrossi L, Falasca L, Checchetto V, Ciaccio R, Fascì A, Chieregato L, Rebelo AP, Giacomello M, Rosato A, Szabò I, Romualdi C, Piacentini M, Leanza L. Transglutaminase Type 2-MITF axis regulates phenotype switching in skin cutaneous melanoma. Cell Death Dis 2023; 14:704. [PMID: 37898636 PMCID: PMC10613311 DOI: 10.1038/s41419-023-06223-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 10/11/2023] [Accepted: 10/16/2023] [Indexed: 10/30/2023]
Abstract
Skin cutaneous melanoma (SKCM) is the deadliest form of skin cancer due to its high heterogeneity that drives tumor aggressiveness. Melanoma plasticity consists of two distinct phenotypic states that co-exist in the tumor niche, the proliferative and the invasive, respectively associated with a high and low expression of MITF, the master regulator of melanocyte lineage. However, despite efforts, melanoma research is still far from exhaustively dissecting this phenomenon. Here, we discovered a key function of Transglutaminase Type-2 (TG2) in regulating melanogenesis by modulating MITF transcription factor expression and its transcriptional activity. Importantly, we demonstrated that TG2 expression affects melanoma invasiveness, highlighting its positive value in SKCM. These results suggest that TG2 may have implications in the regulation of the phenotype switching by promoting melanoma differentiation and impairing its metastatic potential. Our findings offer potential perspectives to unravel melanoma vulnerabilities via tuning intra-tumor heterogeneity.
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Affiliation(s)
- Silvia Muccioli
- Department of Biology, University of Padua, Padua, Italy
- Laboratory of Translational Research, Azienda USL - IRCCS di Reggio Emilia, Reggio Emilia, Italy
| | | | | | - Federica Rossin
- Department of Biology, University of Rome 'Tor Vergata', Rome, Italy
| | | | - Angelo Velle
- Department of Biology, University of Padua, Padua, Italy
| | | | - Beatrice Angi
- Department of Biology, University of Padua, Padua, Italy
| | | | - Anna Tosi
- Immunology and Molecular Oncology Diagnostics, Veneto Institute of Oncology IOV-IRCCS, Padua, Italy
| | - Manuela D'Eletto
- Department of Biology, University of Rome 'Tor Vergata', Rome, Italy
| | - Luca Occhigrossi
- Department of Biology, University of Rome 'Tor Vergata', Rome, Italy
| | - Laura Falasca
- National Institute for Infectious Diseases IRCCS "Lazzaro Spallanzani", Rome, Italy
| | | | | | - Amelia Fascì
- Department of Biology, University of Padua, Padua, Italy
| | | | | | | | - Antonio Rosato
- Immunology and Molecular Oncology Diagnostics, Veneto Institute of Oncology IOV-IRCCS, Padua, Italy
- Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padua, Padua, Italy
| | - Ildikò Szabò
- Department of Biology, University of Padua, Padua, Italy
| | | | - Mauro Piacentini
- Department of Biology, University of Rome 'Tor Vergata', Rome, Italy
- National Institute for Infectious Diseases IRCCS "Lazzaro Spallanzani", Rome, Italy
| | - Luigi Leanza
- Department of Biology, University of Padua, Padua, Italy.
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2
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Corrà S, Checchetto V, Brischigliaro M, Rampazzo C, Bottani E, Gagliani C, Cortese K, De Pittà C, Roverso M, De Stefani D, Bogialli S, Zeviani M, Viscomi C, Szabò I, Costa R. Drosophila Mpv17 forms an ion channel and regulates energy metabolism. iScience 2023; 26:107955. [PMID: 37810222 PMCID: PMC10558772 DOI: 10.1016/j.isci.2023.107955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 07/15/2023] [Accepted: 09/14/2023] [Indexed: 10/10/2023] Open
Abstract
Mutations in MPV17 are a major contributor to mitochondrial DNA (mtDNA) depletion syndromes, a group of inherited genetic conditions due to mtDNA instability. To investigate the role of MPV17 in mtDNA maintenance, we generated and characterized a Drosophila melanogaster Mpv17 (dMpv17) KO model showing that the absence of dMpv17 caused profound mtDNA depletion in the fat body but not in other tissues, increased glycolytic flux and reduced lifespan in starvation. Accordingly, the expression of key genes of glycogenolysis and glycolysis was upregulated in dMpv17 KO flies. In addition, we demonstrated that dMpv17 formed a channel in planar lipid bilayers at physiological ionic conditions, and its electrophysiological hallmarks were affected by pathological mutations. Importantly, the reconstituted channel translocated uridine but not orotate across the membrane. Our results indicate that dMpv17 forms a channel involved in translocation of key metabolites and highlight the importance of dMpv17 in energy homeostasis and mitochondrial function.
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Affiliation(s)
- Samantha Corrà
- Veneto Institute of Molecular Medicine (VIMM), Padova, Italy
| | | | | | | | - Emanuela Bottani
- Department of Diagnostic and Public Health, University of Verona, Verona, Italy
| | - Cristina Gagliani
- Department of Experimental Medicine, University of Genova, Genova, Italy
| | - Katia Cortese
- Department of Experimental Medicine, University of Genova, Genova, Italy
| | | | - Marco Roverso
- Department of Chemical Sciences, University of Padova, Padova, Italy
| | - Diego De Stefani
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Sara Bogialli
- Department of Chemical Sciences, University of Padova, Padova, Italy
| | - Massimo Zeviani
- Department of Neurosciences, University of Padova, Padova, Italy
- IRCCS Materno Infantile Burlo Garofolo, Trieste, Italy
| | - Carlo Viscomi
- Veneto Institute of Molecular Medicine (VIMM), Padova, Italy
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Ildiko Szabò
- Department of Biology, University of Padova, Padova, Italy
| | - Rodolfo Costa
- Department of Biology, University of Padova, Padova, Italy
- Institute of Neuroscience, National Research Council of Italy (CNR), Padova, Italy
- Chronobiology Section, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
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3
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Reina S, Checchetto V. Voltage-Dependent Anion Selective Channel 3: Unraveling Structural and Functional Features of the Least Known Porin Isoform. Front Physiol 2022; 12:784867. [PMID: 35082690 PMCID: PMC8784847 DOI: 10.3389/fphys.2021.784867] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 11/10/2021] [Indexed: 01/31/2023] Open
Abstract
Voltage-dependent anion-selective channels (VDAC) are pore-forming proteins located in the outer mitochondrial membrane. Three isoforms are encoded by separate genes in mammals (VDAC1-3). These proteins play a crucial role in the cell, forming the primary interface between mitochondrial and cellular metabolisms. Research on the role of VDACs in the cell is a rapidly growing field, but the function of VDAC3 remains elusive. The high-sequence similarity between isoforms suggests a similar pore-forming structure. Electrophysiological analyzes revealed that VDAC3 works as a channel; however, its gating and regulation remain debated. A comparison between VDAC3 and VDAC1-2 underlines the presence of a higher number of cysteines in both isoforms 2 and 3. Recent mass spectrometry data demonstrated that the redox state of VDAC3 cysteines is evolutionarily conserved. Accordingly, these residues were always detected as totally reduced or partially oxidized, thus susceptible to disulfide exchange. The deletion of selected cysteines significantly influences the function of the channel. Some cysteine mutants of VDAC3 exhibited distinct kinetic behavior, conductance values and voltage dependence, suggesting that channel activity can be modulated by cysteine reduction/oxidation. These properties point to VDAC3 as a possible marker of redox signaling in the mitochondrial intermembrane space. Here, we summarize our current knowledge about VDAC3 predicted structure, physiological role and regulation, and possible future directions in this research field.
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Affiliation(s)
- Simona Reina
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
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4
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Kravenska Y, Checchetto V, Szabo I. Routes for Potassium Ions across Mitochondrial Membranes: A Biophysical Point of View with Special Focus on the ATP-Sensitive K + Channel. Biomolecules 2021; 11:1172. [PMID: 34439838 PMCID: PMC8393992 DOI: 10.3390/biom11081172] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 07/29/2021] [Accepted: 08/02/2021] [Indexed: 12/18/2022] Open
Abstract
Potassium ions can cross both the outer and inner mitochondrial membranes by means of multiple routes. A few potassium-permeable ion channels exist in the outer membrane, while in the inner membrane, a multitude of different potassium-selective and potassium-permeable channels mediate K+ uptake into energized mitochondria. In contrast, potassium is exported from the matrix thanks to an H+/K+ exchanger whose molecular identity is still debated. Among the K+ channels of the inner mitochondrial membrane, the most widely studied is the ATP-dependent potassium channel, whose pharmacological activation protects cells against ischemic damage and neuronal injury. In this review, we briefly summarize and compare the different hypotheses regarding the molecular identity of this patho-physiologically relevant channel, taking into account the electrophysiological characteristics of the proposed components. In addition, we discuss the characteristics of the other channels sharing localization to both the plasma membrane and mitochondria.
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Affiliation(s)
| | | | - Ildiko Szabo
- Department of Biology, University of Padova, 35131 Padova, Italy; (Y.K.); (V.C.)
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5
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Checchetto V, Leanza L, De Stefani D, Rizzuto R, Gulbins E, Szabo I. Mitochondrial K + channels and their implications for disease mechanisms. Pharmacol Ther 2021; 227:107874. [PMID: 33930454 DOI: 10.1016/j.pharmthera.2021.107874] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 04/12/2021] [Indexed: 02/06/2023]
Abstract
The field of mitochondrial ion channels underwent a rapid development during the last decade, thanks to the molecular identification of some of the nuclear-encoded organelle channels and to advances in strategies allowing specific pharmacological targeting of these proteins. Thereby, genetic tools and specific drugs aided definition of the relevance of several mitochondrial channels both in physiological as well as pathological conditions. Unfortunately, in the case of mitochondrial K+ channels, efforts of genetic manipulation provided only limited results, due to their dual localization to mitochondria and to plasma membrane in most cases. Although the impact of mitochondrial K+ channels on human diseases is still far from being genuinely understood, pre-clinical data strongly argue for their substantial role in the context of several pathologies, including cardiovascular and neurodegenerative diseases as well as cancer. Importantly, these channels are druggable targets, and their in-depth investigation could thus pave the way to the development of innovative small molecules with huge therapeutic potential. In the present review we summarize the available experimental evidence that mechanistically link mitochondrial potassium channels to the above pathologies and underline the possibility of exploiting them for therapy.
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Affiliation(s)
| | - Luigi Leanza
- Department of Biology, University of Padova, Italy
| | | | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padova, Italy
| | - Erich Gulbins
- Department of Molecular Biology, University of Duisburg-Essen, Germany
| | - Ildiko Szabo
- Department of Biology, University of Padova, Italy; CNR Institute of Neurosciences, Italy.
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6
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Parrasia S, Rossa A, Varanita T, Checchetto V, De Lorenzi R, Zoratti M, Paradisi C, Ruzza P, Mattarei A, Szabò I, Biasutto L. An Angiopep2-PAPTP Construct Overcomes the Blood-Brain Barrier. New Perspectives against Brain Tumors. Pharmaceuticals (Basel) 2021; 14:ph14020129. [PMID: 33562146 PMCID: PMC7914648 DOI: 10.3390/ph14020129] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/30/2021] [Accepted: 02/03/2021] [Indexed: 12/23/2022] Open
Abstract
A developing family of chemotherapeutics—derived from 5-(4-phenoxybutoxy)psoralen (PAP-1)—target mitochondrial potassium channel mtKv1.3 to selectively induce oxidative stress and death of diseased cells. The key to their effectiveness is the presence of a positively charged triphenylphosphonium group which drives their accumulation in the organelles. These compounds have proven their preclinical worth in murine models of cancers such as melanoma and pancreatic adenocarcinoma. In in vitro experiments they also efficiently killed glioblastoma cells, but in vivo they were powerless against orthotopic glioma because they were completely unable to overcome the blood-brain barrier. In an effort to improve brain delivery we have now coupled one of these promising compounds, PAPTP, to well-known cell-penetrating and brain-targeting peptides TAT48–61 and Angiopep-2. Coupling has been obtained by linking one of the phenyl groups of the triphenylphosphonium to the first amino acid of the peptide via a reversible carbamate ester bond. Both TAT48–61 and Angiopep-2 allowed the delivery of 0.3–0.4 nmoles of construct per gram of brain tissue upon intravenous (i.v.) injection of 5 µmoles/kg bw to mice. This is the first evidence of PAPTP delivery to the brain; the chemical strategy described here opens the possibility to conjugate PAPTP to small peptides in order to fine-tune tissue distribution of this interesting compound.
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Affiliation(s)
- Sofia Parrasia
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy; (S.P.); (M.Z.)
| | - Andrea Rossa
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (A.R.); (R.D.L.); (C.P.); (P.R.)
| | - Tatiana Varanita
- Department of Biology, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy; (T.V.); (V.C.); (I.S.)
| | - Vanessa Checchetto
- Department of Biology, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy; (T.V.); (V.C.); (I.S.)
| | - Riccardo De Lorenzi
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (A.R.); (R.D.L.); (C.P.); (P.R.)
- CNR Institute of Biomolecular Chemistry, Via F. Marzolo 1, 35131 Padova, Italy
| | - Mario Zoratti
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy; (S.P.); (M.Z.)
- CNR Neuroscience Institute, Viale G. Colombo 3, 35131 Padova, Italy
| | - Cristina Paradisi
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (A.R.); (R.D.L.); (C.P.); (P.R.)
| | - Paolo Ruzza
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (A.R.); (R.D.L.); (C.P.); (P.R.)
- CNR Institute of Biomolecular Chemistry, Via F. Marzolo 1, 35131 Padova, Italy
| | - Andrea Mattarei
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131 Padova, Italy;
| | - Ildikò Szabò
- Department of Biology, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy; (T.V.); (V.C.); (I.S.)
| | - Lucia Biasutto
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy; (S.P.); (M.Z.)
- CNR Neuroscience Institute, Viale G. Colombo 3, 35131 Padova, Italy
- Correspondence:
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7
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Urbani A, Prosdocimi E, Carrer A, Checchetto V, Szabò I. Mitochondrial Ion Channels of the Inner Membrane and Their Regulation in Cell Death Signaling. Front Cell Dev Biol 2021; 8:620081. [PMID: 33585458 PMCID: PMC7874202 DOI: 10.3389/fcell.2020.620081] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 12/07/2020] [Indexed: 12/11/2022] Open
Abstract
Mitochondria are bioenergetic organelles with a plethora of fundamental functions ranging from metabolism and ATP production to modulation of signaling events leading to cell survival or cell death. Ion channels located in the outer and inner mitochondrial membranes critically control mitochondrial function and, as a consequence, also cell fate. Opening or closure of mitochondrial ion channels allow the fine-tuning of mitochondrial membrane potential, ROS production, and function of the respiratory chain complexes. In this review, we critically discuss the intracellular regulatory factors that affect channel activity in the inner membrane of mitochondria and, indirectly, contribute to cell death. These factors include various ligands, kinases, second messengers, and lipids. Comprehension of mitochondrial ion channels regulation in cell death pathways might reveal new therapeutic targets in mitochondria-linked pathologies like cancer, ischemia, reperfusion injury, and neurological disorders.
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Affiliation(s)
- Andrea Urbani
- Department of Biomedical Sciences, University of Padova, Padua, Italy
- Department of Biology, University of Padova, Padua, Italy
| | | | - Andrea Carrer
- Department of Biomedical Sciences, University of Padova, Padua, Italy
- Department of Biology, University of Padova, Padua, Italy
| | | | - Ildikò Szabò
- Department of Biology, University of Padova, Padua, Italy
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8
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Abstract
Kv1.3 is a voltage gated potassium channel located in the plasma membrane, as well as at intracellular levels, such as mitochondria (mitoKv1.3), nucleus and Golgi apparatus. The plasma membrane channel has been shown to be important for cell proliferation, while the mitochondrial counterpart has been related to modulation of cell death. Moreover, altered expression of Kv1.3 was observed in various tumors and Kv1.3 seems to be involved in development and progression of various cancerous forms. Recent experimental evidences have proved that pharmacological inhibition of the mitoKv1.3 succeeded in reducing up to 90% of tumor volume in vivo in orthotopic mouse model. Furthermore, mitoKv1.3 modulation could impact on cell proliferation as well as on regulation of intracellular signaling pathways. Indeed, the treatment with sub-lethal doses of mitoKv1.3 inhibitors can downregulate Wnt-β catenin signaling by reducing mitochondrial ATP production and triggering ER-stress. In this review, we describe the role of the mitoKv1.3 in cell death, cancer and intracellular signaling. We will discuss how pharmacological modulation of mitochondrial potassium fluxes impact on mitochondrial membrane potential, reactive oxygen species production and ATP synthesis. All these changes in mitochondrial fitness are related to cell proliferation as well as to cell death and finally on cancer development and progression, so Kv1.3 (and mitoKv1.3) could be now considered a new oncological target.
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Affiliation(s)
| | | | - Luigi Leanza
- Department of Biology, University of Padova, Padova, Italy,
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9
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Paggio A, Checchetto V, Campo A, Menabò R, Di Marco G, Di Lisa F, Szabo I, Rizzuto R, De Stefani D. Identification of an ATP-sensitive potassium channel in mitochondria. Nature 2019; 572:609-613. [PMID: 31435016 PMCID: PMC6726485 DOI: 10.1038/s41586-019-1498-3] [Citation(s) in RCA: 159] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 07/25/2019] [Indexed: 11/09/2022]
Abstract
Mitochondria provide chemical energy for endoergonic reactions in the form of ATP, and their activity must meet cellular energy requirements, but the mechanisms that link organelle performance to ATP levels are poorly understood. Here we confirm the existence of a protein complex localized in mitochondria that mediates ATP-dependent potassium currents (that is, mitoKATP). We show that-similar to their plasma membrane counterparts-mitoKATP channels are composed of pore-forming and ATP-binding subunits, which we term MITOK and MITOSUR, respectively. In vitro reconstitution of MITOK together with MITOSUR recapitulates the main properties of mitoKATP. Overexpression of MITOK triggers marked organelle swelling, whereas the genetic ablation of this subunit causes instability in the mitochondrial membrane potential, widening of the intracristal space and decreased oxidative phosphorylation. In a mouse model, the loss of MITOK suppresses the cardioprotection that is elicited by pharmacological preconditioning induced by diazoxide. Our results indicate that mitoKATP channels respond to the cellular energetic status by regulating organelle volume and function, and thereby have a key role in mitochondrial physiology and potential effects on several pathological processes.
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Affiliation(s)
- Angela Paggio
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | | | - Antonio Campo
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | | | - Giulia Di Marco
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Fabio Di Lisa
- Department of Biomedical Sciences, University of Padova, Padova, Italy.,CNR Institute of Neuroscience, Padova, Italy
| | - Ildiko Szabo
- Department of Biology, University of Padova, Padova, Italy.,CNR Institute of Neuroscience, Padova, Italy
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padova, Padova, Italy.
| | - Diego De Stefani
- Department of Biomedical Sciences, University of Padova, Padova, Italy.
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10
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Prosdocimi E, Checchetto V, Leanza L. Targeting the Mitochondrial Potassium Channel Kv1.3 to Kill Cancer Cells: Drugs, Strategies, and New Perspectives. SLAS Discov 2019; 24:882-892. [PMID: 31373829 DOI: 10.1177/2472555219864894] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cancer is the consequence of aberrations in cell growth or cell death. In this scenario, mitochondria and ion channels play a critical role in regard to cell proliferation, malignant angiogenesis, migration, and metastasis. In this review, we focus on Kv1.3 and specifically on mitoKv1.3, which showed an aberrant expression in cancer cells compared with healthy tissues and which is involved in the apoptotic pathway. In recent years, mitoKv1.3 has become an oncological target since its pharmacological modulation has been demonstrated to reduce tumor growth and progression both in vitro and in vivo using preclinical mouse models of different types of tumors.
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Affiliation(s)
| | | | - Luigi Leanza
- Department of Biology, University of Padova, Padova, Italy
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11
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Carraro M, Checchetto V, Szabó I, Bernardi P. F‐ATPsynthase and the permeability transition pore: fewer doubts, more certainties. FEBS Lett 2019; 593:1542-1553. [DOI: 10.1002/1873-3468.13485] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 06/09/2019] [Accepted: 06/10/2019] [Indexed: 12/27/2022]
Affiliation(s)
- Michela Carraro
- Department of Biomedical Sciences University of Padova Italy
| | | | - Ildikó Szabó
- Department of Biology University of Padova Italy
| | - Paolo Bernardi
- Department of Biomedical Sciences University of Padova Italy
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12
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Leanza L, Checchetto V, Biasutto L, Rossa A, Costa R, Bachmann M, Zoratti M, Szabo I. Pharmacological modulation of mitochondrial ion channels. Br J Pharmacol 2019; 176:4258-4283. [PMID: 30440086 DOI: 10.1111/bph.14544] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 10/15/2018] [Accepted: 10/22/2018] [Indexed: 12/17/2022] Open
Abstract
The field of mitochondrial ion channels has undergone a rapid development during the last three decades, due to the molecular identification of some of the channels residing in the outer and inner membranes. Relevant information about the function of these channels in physiological and pathological settings was gained thanks to genetic models for a few, mitochondria-specific channels. However, many ion channels have multiple localizations within the cell, hampering a clear-cut determination of their function by pharmacological means. The present review summarizes our current knowledge about the ins and outs of mitochondrial ion channels, with special focus on the channels that have received much attention in recent years, namely, the voltage-dependent anion channels, the permeability transition pore (also called mitochondrial megachannel), the mitochondrial calcium uniporter and some of the inner membrane-located potassium channels. In addition, possible strategies to overcome the difficulties of specifically targeting mitochondrial channels versus their counterparts active in other membranes are discussed, as well as the possibilities of modulating channel function by small peptides that compete for binding with protein interacting partners. Altogether, these promising tools along with large-scale chemical screenings set up to identify new, specific channel modulators will hopefully allow us to pinpoint the actual function of most mitochondrial ion channels in the near future and to pharmacologically affect important pathologies in which they are involved, such as neurodegeneration, ischaemic damage and cancer. LINKED ARTICLES: This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.
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Affiliation(s)
- Luigi Leanza
- Department of Biology, University of Padova, Padova, Italy
| | | | - Lucia Biasutto
- CNR Institute of Neurosciences, Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Andrea Rossa
- Department of Chemical Sciences, University of Padova, Padova, Italy
| | - Roberto Costa
- Department of Biology, University of Padova, Padova, Italy
| | | | - Mario Zoratti
- CNR Institute of Neurosciences, Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Ildiko Szabo
- Department of Biology, University of Padova, Padova, Italy.,CNR Institute of Neurosciences, Department of Biomedical Sciences, University of Padova, Padova, Italy
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13
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Checchetto V, Szabò I. Electrophysiological Characterization of Calcium-Permeable Channels Using Planar Lipid Bilayer. Methods Mol Biol 2019; 1925:65-73. [PMID: 30674017 DOI: 10.1007/978-1-4939-9018-4_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Numerous researchers tried to identify the key players of calcium signaling in mitochondria using molecular and cell biology techniques for more than five decades. However, only an integrated approach involving also electrophysiological techniques has finally allowed to define the components of the protein complex responsible for the uptake of this ion into mitochondria.Here we describe the protocol used for the electrophysiological characterization of the mitochondrial calcium uniporter (MCU) complex: the following outline indicates step-by-step the setup of planar lipid bilayer experiments.
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Affiliation(s)
| | - Ildikò Szabò
- Department of Biology, University of Padua, Padua, Italy
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14
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De Col V, Petrussa E, Casolo V, Braidot E, Lippe G, Filippi A, Peresson C, Patui S, Bertolini A, Giorgio V, Checchetto V, Vianello A, Bernardi P, Zancani M. Properties of the Permeability Transition of Pea Stem Mitochondria. Front Physiol 2018; 9:1626. [PMID: 30524297 PMCID: PMC6262314 DOI: 10.3389/fphys.2018.01626] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 10/29/2018] [Indexed: 12/17/2022] Open
Abstract
In striking analogy with Saccharomyces cerevisiae, etiolated pea stem mitochondria did not show appreciable Ca2+ uptake. Only treatment with the ionophore ETH129 (which allows electrophoretic Ca2+ equilibration) caused Ca2+ uptake followed by increased inner membrane permeability, membrane depolarization and Ca2+ release. Like the permeability transition (PT) of mammals, yeast and Drosophila, the PT of pea stem mitochondria was stimulated by diamide and phenylarsine oxide and inhibited by Mg-ADP and Mg-ATP, suggesting a common underlying mechanism; yet, the plant PT also displayed distinctive features: (i) as in mammals it was desensitized by cyclosporin A, which does not affect the PT of yeast and Drosophila; (ii) similarly to S. cerevisiae and Drosophila it was inhibited by Pi, which stimulates the PT of mammals; (iii) like in mammals and Drosophila it was sensitized by benzodiazepine 423, which is ineffective in S. cerevisiae; (iv) like what observed in Drosophila it did not mediate swelling and cytochrome c release, which is instead seen in mammals and S. cerevisiae. We find that cyclophilin D, the mitochondrial receptor for cyclosporin A, is present in pea stem mitochondria. These results indicate that the plant PT has unique features and suggest that, as in Drosophila, it may provide pea stem mitochondria with a Ca2+ release channel.
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Affiliation(s)
- Valentina De Col
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
| | - Elisa Petrussa
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
| | - Valentino Casolo
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
| | - Enrico Braidot
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
| | - Giovanna Lippe
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
| | - Antonio Filippi
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
| | - Carlo Peresson
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
| | - Sonia Patui
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
| | - Alberto Bertolini
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
| | - Valentina Giorgio
- Department of Biomedical Sciences, University of Padova and CNR Neuroscience Institute, Padova, Italy
| | | | - Angelo Vianello
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
| | - Paolo Bernardi
- Department of Biomedical Sciences, University of Padova and CNR Neuroscience Institute, Padova, Italy
| | - Marco Zancani
- Department of Agricultural, Food, Environmental and Animal Sciences (Di4A), University of Udine, Udine, Italy
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15
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Carraro M, Checchetto V, Sartori G, Kucharczyk R, di Rago JP, Minervini G, Franchin C, Arrigoni G, Giorgio V, Petronilli V, Tosatto S, Lippe G, Szabó I, Bernardi P. High-Conductance Channel Formation in Yeast Mitochondria is Mediated by F-ATP Synthase e and g Subunits. Cell Physiol Biochem 2018; 50:1840-1855. [DOI: 10.1159/000494864] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 10/26/2018] [Indexed: 11/19/2022] Open
Abstract
Background/Aims: The permeability transition pore (PTP) is an unselective, Ca2+-dependent high conductance channel of the inner mitochondrial membrane whose molecular identity has long remained a mystery. The most recent hypothesis is that pore formation involves the F-ATP synthase, which consistently generates Ca2+-activated channels. Available structures do not display obvious features that can accommodate a channel; thus, how the pore can form and whether its activity can be entirely assigned to F-ATP synthase is the matter of debate. In this study, we investigated the role of F-ATP synthase subunits e, g and b in PTP formation. Methods: Yeast null mutants for e, g and the first transmembrane (TM) α-helix of subunit b were generated and evaluated for mitochondrial morphology (electron microscopy), membrane potential (Rhodamine123 fluorescence) and respiration (Clark electrode). Homoplasmic C23S mutant of subunit a was generated by in vitro mutagenesis followed by biolistic transformation. F-ATP synthase assembly was evaluated by BN-PAGE analysis. Cu2+ treatment was used to induce the formation of F-ATP synthase dimers in the absence of e and g subunits. The electrophysiological properties of F-ATP synthase were assessed in planar lipid bilayers. Results: Null mutants for the subunits e and g display dimer formation upon Cu2+ treatment and show PTP-dependent mitochondrial Ca2+ release but not swelling. Cu2+ treatment causes formation of disulfide bridges between Cys23 of subunits a that stabilize dimers in absence of e and g subunits and favors the open state of wild-type F-ATP synthase channels. Absence of e and g subunits decreases conductance of the F-ATP synthase channel about tenfold. Ablation of the first TM of subunit b, which creates a distinct lateral domain with e and g, further affected channel activity. Conclusion: F-ATP synthase e, g and b subunits create a domain within the membrane that is critical for the generation of the high-conductance channel, thus is a prime candidate for PTP formation. Subunits e and g are only present in eukaryotes and may have evolved to confer this novel function to F-ATP synthase.
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16
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Bachmann M, Costa R, Peruzzo R, Prosdocimi E, Checchetto V, Leanza L. Targeting Mitochondrial Ion Channels to Fight Cancer. Int J Mol Sci 2018; 19:ijms19072060. [PMID: 30011966 PMCID: PMC6073807 DOI: 10.3390/ijms19072060] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 07/12/2018] [Accepted: 07/13/2018] [Indexed: 12/14/2022] Open
Abstract
In recent years, several experimental evidences have underlined a new role of ion channels in cancer development and progression. In particular, mitochondrial ion channels are arising as new oncological targets, since it has been proved that most of them show an altered expression during tumor development and the pharmacological targeting of some of them have been demonstrated to be able to modulate cancer growth and progression, both in vitro as well as in vivo in pre-clinical mouse models. In this scenario, pharmacology of mitochondrial ion channels would be in the near future a new frontier for the treatment of tumors. In this review, we discuss the new advances in the field, by focusing our attention on the improvements in new drug developments to target mitochondrial ion channels.
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Affiliation(s)
| | - Roberto Costa
- Department of Biology, University of Padova, 35131 Padova, Italy.
| | - Roberta Peruzzo
- Department of Biology, University of Padova, 35131 Padova, Italy.
| | - Elena Prosdocimi
- Department of Biology, University of Padova, 35131 Padova, Italy.
| | | | - Luigi Leanza
- Department of Biology, University of Padova, 35131 Padova, Italy.
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17
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Checchetto V, Szabo I. Novel Channels of the Outer Membrane of Mitochondria: Recent Discoveries Change Our View. Bioessays 2018; 40:e1700232. [PMID: 29682771 DOI: 10.1002/bies.201700232] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 03/09/2018] [Indexed: 01/12/2023]
Abstract
Ion channels mediate ion flux across biological membranes and regulate important organellar and cellular tasks. A recent study revealed the presence of four new proteins, the MIM complex (composed by Mim1 and Mim2), Ayr1, OMC7, and OMC8, that are able to form ion-conducting channels in the outer mitochondria membrane (OMM). These findings strongly indicate that the OMM is endowed with many solute-specific channels, in addition to porins and known channels mediating protein import into mitochondria. These solute-specific channels provide essential pathways for the controlled transport of ions and metabolites and may thus add a further layer of specificity to the regulation of mitochondrial function at the organelle-cytosol and/or inter-organellar interface. Future studies will be required to fully understand the way(s) of regulation of these new channels and to integrate them into signaling pathways within the cells.
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Affiliation(s)
| | - Ildiko Szabo
- Department of Biology, University of Padova, Padua 35121, Italy
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18
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Reina S, Checchetto V, Saletti R, Gupta A, Chaturvedi D, Guardiani C, Guarino F, Scorciapino MA, Magrì A, Foti S, Ceccarelli M, Messina AA, Mahalakshmi R, Szabo I, De Pinto V. VDAC3 as a sensor of oxidative state of the intermembrane space of mitochondria: the putative role of cysteine residue modifications. Oncotarget 2016; 7:2249-68. [PMID: 26760765 PMCID: PMC4823033 DOI: 10.18632/oncotarget.6850] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 12/23/2015] [Indexed: 12/22/2022] Open
Abstract
Voltage-Dependent Anion selective Channels (VDAC) are pore-forming mitochondrial outer membrane proteins. In mammals VDAC3, the least characterized isoform, presents a set of cysteines predicted to be exposed toward the intermembrane space. We find that cysteines in VDAC3 can stay in different oxidation states. This was preliminary observed when, in our experimental conditions, completely lacking any reducing agent, VDAC3 presented a pattern of slightly different electrophoretic mobilities. This observation holds true both for rat liver mitochondrial VDAC3 and for recombinant and refolded human VDAC3. Mass spectroscopy revealed that cysteines 2 and 8 can form a disulfide bridge in native VDAC3. Single or combined site-directed mutagenesis of cysteines 2, 8 and 122 showed that the protein mobility in SDS-PAGE is influenced by the presence of cysteine and by the redox status. In addition, cysteines 2, 8 and 122 are involved in the stability control of the pore as shown by electrophysiology, complementation assays and chemico-physical characterization. Furthermore, a positive correlation between the pore conductance of the mutants and their ability to complement the growth of porin-less yeast mutant cells was found. Our work provides evidence for a complex oxidation pattern of a mitochondrial protein not directly involved in electron transport. The most likely biological meaning of this behavior is to buffer the ROS load and keep track of the redox level in the inter-membrane space, eventually signaling it through conformational changes.
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Affiliation(s)
- Simona Reina
- Department of Biomedicine and Biotechnology BIOMETEC, Section of Biology and Genetics, University of Catania, Catania, Italy.,National Institute for Biomembranes and Biosystems, Section of Catania, Catania, Italy
| | - Vanessa Checchetto
- Department of Biology, University of Padova, Padova, Italy.,CNR Institute of Neurosciences, Padova, Italy
| | - Rosaria Saletti
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Ankit Gupta
- Department of Chemical Sciences, Mass Spectrometry Unit, University of Catania, Catania, Italy
| | - Deepti Chaturvedi
- Department of Chemical Sciences, Mass Spectrometry Unit, University of Catania, Catania, Italy
| | - Carlo Guardiani
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, India
| | - Francesca Guarino
- Department of Biomedicine and Biotechnology BIOMETEC, Section of Biology and Genetics, University of Catania, Catania, Italy
| | - Mariano Andrea Scorciapino
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, India
| | - Andrea Magrì
- Department of Biomedicine and Biotechnology BIOMETEC, Section of Biology and Genetics, University of Catania, Catania, Italy
| | | | - Matteo Ceccarelli
- Department of Chemical Sciences, Mass Spectrometry Unit, University of Catania, Catania, Italy.,Department of Physics, University of Cagliari, Cagliari, Italy
| | - Angela Anna Messina
- Department of Biomedical Sciences, Biochemistry Unit, University of Cagliari, Cagliari, Italy
| | | | - Ildiko Szabo
- National Institute for Biomembranes and Biosystems, Section of Catania, Catania, Italy
| | - Vito De Pinto
- Department of Biomedicine and Biotechnology BIOMETEC, Section of Biology and Genetics, University of Catania, Catania, Italy
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19
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Carraro M, Guo L, Giorgio V, Checchetto V, Šileikytė J, Sartori G, Forte M, Lippe G, Zoratti M, Szabò I, Bernardi P. Shedding light on the permeability transition through S. cerevisiae F-ATP synthase mutagenesis. Biochimica et Biophysica Acta (BBA) - Bioenergetics 2016. [DOI: 10.1016/j.bbabio.2016.04.156] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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20
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Checchetto V, Segalla A, Sato Y, Bergantino E, Szabo I, Uozumi N. Involvement of Potassium Transport Systems in the Response of Synechocystis PCC 6803 Cyanobacteria to External pH Change, High-Intensity Light Stress and Heavy Metal Stress. Plant Cell Physiol 2016; 57:862-877. [PMID: 26880819 DOI: 10.1093/pcp/pcw032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 02/04/2016] [Indexed: 06/05/2023]
Abstract
The unicellular photosynthetic cyanobacterium, able to survive in varying environments, is the only prokaryote that directly converts solar energy and CO2 into organic material and is thus relevant for primary production in many ecosystems. To maintain the intracellular and intrathylakoid ion homeostasis upon different environmental challenges, the concentration of potassium as a major intracellular cation has to be optimized by various K(+)uptake-mediated transport systems. We reveal here the specific and concerted physiological function of three K(+)transporters of the plasma and thylakoid membranes, namely of SynK (K(+)channel), KtrB (Ktr/Trk/HKT) and KdpA (Kdp) in Synechocystis sp. strain PCC 6803, under specific stress conditions. The behavior of the wild type, single, double and triple mutants was compared, revealing that only Synk contributes to heavy metal-induced stress, while only Ktr/Kdp is involved in osmotic and salt stress adaptation. With regards to pH shifts in the external medium, the Kdp/Ktr uptake systems play an important role in the adaptation to acidic pH. Ktr, by affecting the CO2 concentration mechanism via its action on the bicarbonate transporter SbtA, might also be responsible for the observed effects concerning high-light stress and calcification. In the case of illumination with high-intensity light, a synergistic action of Kdr/Ktp and SynK is required in order to avoid oxidative stress and ensure cell viability. In summary, this study dissects, using growth tests, measurement of photosynthetic activity and analysis of ultrastructure, the physiological role of three K(+)transporters in adaptation of the cyanobacteria to various environmental changes.
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Affiliation(s)
- Vanessa Checchetto
- Department of Biology, University of Padova, Padova 35121, Italy Department of Biomedical Sciences, University of Padova, Padova 35121, Italy
| | - Anna Segalla
- Department of Biology, University of Padova, Padova 35121, Italy
| | - Yuki Sato
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579 Japan
| | | | - Ildiko Szabo
- Department of Biology, University of Padova, Padova 35121, Italy
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579 Japan
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21
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Carraretto L, Checchetto V, De Bortoli S, Formentin E, Costa A, Szabó I, Teardo E. Calcium Flux across Plant Mitochondrial Membranes: Possible Molecular Players. Front Plant Sci 2016; 7:354. [PMID: 27065186 PMCID: PMC4814809 DOI: 10.3389/fpls.2016.00354] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2015] [Accepted: 03/07/2016] [Indexed: 05/24/2023]
Abstract
Plants, being sessile organisms, have evolved the ability to integrate external stimuli into metabolic and developmental signals. A wide variety of signals, including abiotic, biotic, and developmental stimuli, were observed to evoke specific spatio-temporal Ca(2+) transients which are further transduced by Ca(2+) sensor proteins into a transcriptional and metabolic response. Most of the research on Ca(2+) signaling in plants has been focused on the transport mechanisms for Ca(2+) across the plasma- and the vacuolar membranes as well as on the components involved in decoding of cytoplasmic Ca(2+) signals, but how intracellular organelles such as mitochondria are involved in the process of Ca(2+) signaling is just emerging. The combination of the molecular players and the elicitors of Ca(2+) signaling in mitochondria together with newly generated detection systems for measuring organellar Ca(2+) concentrations in plants has started to provide fruitful grounds for further discoveries. In the present review we give an updated overview of the currently identified/hypothesized pathways, such as voltage-dependent anion channels, homologs of the mammalian mitochondrial uniporter (MCU), LETM1, a plant glutamate receptor family member, adenine nucleotide/phosphate carriers and the permeability transition pore (PTP), that may contribute to the transport of Ca(2+) across the outer and inner mitochondrial membranes in plants. We briefly discuss the relevance of the mitochondrial Ca(2+) homeostasis for ensuring optimal bioenergetic performance of this organelle.
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Affiliation(s)
| | - Vanessa Checchetto
- Department of Biology, University of PadovaPadova, Italy
- Department of Biomedical Sciences, University of PadovaPadova, Italy
| | | | - Elide Formentin
- Department of Biology, University of PadovaPadova, Italy
- Department of Life Science and Biotechnology, University of FerraraFerrara, Italy
| | - Alex Costa
- Department of Biosciences, University of MilanMilan, Italy
- CNR, Institute of Biophysics, Consiglio Nazionale delle RicercheMilan, Italy
| | - Ildikó Szabó
- Department of Biology, University of PadovaPadova, Italy
- CNR, Institute of NeurosciencesPadova, Italy
| | - Enrico Teardo
- Department of Biology, University of PadovaPadova, Italy
- CNR, Institute of NeurosciencesPadova, Italy
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22
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Checchetto V, Teardo E, Carraretto L, Leanza L, Szabo I. Physiology of intracellular potassium channels: A unifying role as mediators of counterion fluxes? Biochim Biophys Acta 2016; 1857:1258-1266. [PMID: 26970213 DOI: 10.1016/j.bbabio.2016.03.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Revised: 03/06/2016] [Accepted: 03/07/2016] [Indexed: 12/28/2022]
Abstract
Plasma membrane potassium channels importantly contribute to maintain ion homeostasis across the cell membrane. The view is emerging that also those residing in intracellular membranes play pivotal roles for the coordination of correct cell function. In this review we critically discuss our current understanding of the nature and physiological tasks of potassium channels in organelle membranes in both animal and plant cells, with a special emphasis on their function in the regulation of photosynthesis and mitochondrial respiration. In addition, the emerging role of potassium channels in the nuclear membranes in regulating transcription will be discussed. The possible functions of endoplasmic reticulum-, lysosome- and plant vacuolar membrane-located channels are also referred to. Altogether, experimental evidence obtained with distinct channels in different membrane systems points to a possible unifying function of most intracellular potassium channels in counterbalancing the movement of other ions including protons and calcium and modulating membrane potential, thereby fine-tuning crucial cellular processes. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-7, 2016', edited by Prof. Paolo Bernardi.
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Affiliation(s)
- Vanessa Checchetto
- Department of Biology, University of Padova, Viale G. Colombo 3, Padova 35131, Italy; Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, Padova 35131 Italy
| | - Enrico Teardo
- Department of Biology, University of Padova, Viale G. Colombo 3, Padova 35131, Italy
| | - Luca Carraretto
- Department of Biology, University of Padova, Viale G. Colombo 3, Padova 35131, Italy
| | - Luigi Leanza
- Department of Biology, University of Padova, Viale G. Colombo 3, Padova 35131, Italy
| | - Ildiko Szabo
- Department of Biology, University of Padova, Viale G. Colombo 3, Padova 35131, Italy; CNR Institute of Neuroscience, University of Padova, Viale G. Colombo 3, Padova 35131, Italy.
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23
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Carraretto L, Teardo E, Checchetto V, Finazzi G, Uozumi N, Szabo I. Ion Channels in Plant Bioenergetic Organelles, Chloroplasts and Mitochondria: From Molecular Identification to Function. Mol Plant 2016; 9:371-395. [PMID: 26751960 DOI: 10.1016/j.molp.2015.12.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 11/22/2015] [Accepted: 12/01/2015] [Indexed: 06/05/2023]
Abstract
Recent technical advances in electrophysiological measurements, organelle-targeted fluorescence imaging, and organelle proteomics have pushed the research of ion transport a step forward in the case of the plant bioenergetic organelles, chloroplasts and mitochondria, leading to the molecular identification and functional characterization of several ion transport systems in recent years. Here we focus on channels that mediate relatively high-rate ion and water flux and summarize the current knowledge in this field, focusing on targeting mechanisms, proteomics, electrophysiology, and physiological function. In addition, since chloroplasts evolved from a cyanobacterial ancestor, we give an overview of the information available about cyanobacterial ion channels and discuss the evolutionary origin of chloroplast channels. The recent molecular identification of some of these ion channels allowed their physiological functions to be studied using genetically modified Arabidopsis plants and cyanobacteria. The view is emerging that alteration of chloroplast and mitochondrial ion homeostasis leads to organelle dysfunction, which in turn significantly affects the energy metabolism of the whole organism. Clear-cut identification of genes encoding for channels in these organelles, however, remains a major challenge in this rapidly developing field. Multiple strategies including bioinformatics, cell biology, electrophysiology, use of organelle-targeted ion-sensitive probes, genetics, and identification of signals eliciting specific ion fluxes across organelle membranes should provide a better understanding of the physiological role of organellar channels and their contribution to signaling pathways in plants in the future.
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Affiliation(s)
- Luca Carraretto
- Department of Biology, University of Padova, Padova 35121, Italy
| | - Enrico Teardo
- Department of Biology, University of Padova, Padova 35121, Italy; CNR Institute of Neuroscience, University of Padova, Padova 35121, Italy
| | | | - Giovanni Finazzi
- UMR 5168 Laboratoire de Physiologie Cellulaire Végétale (LPCV) CNRS/ UJF / INRA / CEA, Institut de Recherches en Technologies et Sciences pour le Vivant (iRTSV), CEA Grenoble, 38054 Grenoble, France.
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai 980-8579, Japan.
| | - Ildiko Szabo
- Department of Biology, University of Padova, Padova 35121, Italy; CNR Institute of Neuroscience, University of Padova, Padova 35121, Italy.
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24
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Reina S, Checchetto V, Saletti R, Gupta A, Chaturvedi D, Guardiani C, Guarino F, Andrea Scorciapino M, Magrì A, Foti S, Ceccarelli M, Messina AA, Mahalakshmi R, Szabo I, De Pinto V. Unexpected Modifications of Cysteines in VDAC3: Indication that VDAC3 may Signal the Mitochondrial Intermembrane Redox State. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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25
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Paggio A, Checchetto V, Szabò I, Rizzuto R, De Stefani D. Novel Players in the Control of Mitochondrial Ion Homeostasis. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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26
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Reina S, Checchetto V, Guarino F, Guardiani C, Belfiore R, Ceccarelli M, Szabo I, De Pinto V. Preliminary Characterization of VDAC3, an Elusive Member of the Outer Mitochondrial Membrane Pore Family. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.1691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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27
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von Stockum S, Giorgio V, Trevisan E, Lippe G, Glick GD, Forte MA, Da-Rè C, Checchetto V, Mazzotta G, Costa R, Szabò I, Bernardi P. F-ATPase of Drosophila melanogaster forms 53-picosiemen (53-pS) channels responsible for mitochondrial Ca2+-induced Ca2+ release. J Biol Chem 2014; 290:4537-4544. [PMID: 25550160 DOI: 10.1074/jbc.c114.629766] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondria of Drosophila melanogaster undergo Ca(2+)-induced Ca(2+) release through a putative channel (mCrC) that has several regulatory features of the permeability transition pore (PTP). The PTP is an inner membrane channel that forms from F-ATPase, possessing a conductance of 500 picosiemens (pS) in mammals and of 300 pS in yeast. In contrast to the PTP, the mCrC of Drosophila is not permeable to sucrose and appears to be selective for Ca(2+) and H(+). We show (i) that like the PTP, the mCrC is affected by the sense of rotation of F-ATPase, by Bz-423, and by Mg(2+)/ADP; (ii) that expression of human cyclophilin D in mitochondria of Drosophila S2R(+) cells sensitizes the mCrC to Ca(2+) but does not increase its apparent size; and (iii) that purified dimers of D. melanogaster F-ATPase reconstituted into lipid bilayers form 53-pS channels activated by Ca(2+) and thiol oxidants and inhibited by Mg(2+)/γ-imino ATP. These findings indicate that the mCrC is the PTP of D. melanogaster and that the signature conductance of F-ATPase channels depends on unique structural features that may underscore specific roles in different species.
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Affiliation(s)
| | | | | | - Giovanna Lippe
- the Department of Food Science, University of Udine, I-33100 Udine, Italy
| | - Gary D Glick
- the Department of Chemistry, Graduate Program in Immunology, University of Michigan, Ann Arbor, Michigan 48109, and
| | - Michael A Forte
- the Vollum Institute, Oregon Health and Sciences University, Portland, Oregon 97239
| | - Caterina Da-Rè
- Biology, University of Padova and Consiglio Nazionale delle Ricerche Neuroscience Institute, I-35131 Padova, Italy
| | - Vanessa Checchetto
- Biology, University of Padova and Consiglio Nazionale delle Ricerche Neuroscience Institute, I-35131 Padova, Italy
| | - Gabriella Mazzotta
- Biology, University of Padova and Consiglio Nazionale delle Ricerche Neuroscience Institute, I-35131 Padova, Italy
| | - Rodolfo Costa
- Biology, University of Padova and Consiglio Nazionale delle Ricerche Neuroscience Institute, I-35131 Padova, Italy
| | - Ildikò Szabò
- Biology, University of Padova and Consiglio Nazionale delle Ricerche Neuroscience Institute, I-35131 Padova, Italy
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Checchetto V, Reina S, Magrì A, Szabo I, De Pinto V. Recombinant human voltage dependent anion selective channel isoform 3 (hVDAC3) forms pores with a very small conductance. Cell Physiol Biochem 2014; 34:842-53. [PMID: 25171321 DOI: 10.1159/000363047] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/03/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Voltage-dependent anion channels (VDAC), also known as eukaryotic porins, are located in the outer mitochondrial membrane and allow the flux of ions and small metabolites. While the pore-forming ability of recombinant VDAC1 and VDAC2 has been extensively studied during the last decades, a clear-cut ion conducting channel activity has not been assigned to the VDAC3 isoform. Methods : Electrophysiological characterization of the recombinant protein purified and refolded was obtained after incorporation into planar lipid bilayers. RESULTS Here we report for the first time that recombinant hVDAC3, upon expression in E.coli and purification-refolding, shows a channel activity with a very small conductance (90 pS in 1 M KCl) with respect to the conductance of hVDAC1 (>3500 pS in 1 M KCl). Purified hVDAC3 allowed the passage of both chloride and gluconate anions and did not distinguish between potassium, sodium and calcium used as cations. In contrast to VDAC1, the channel was active also at transmembrane voltages higher than +/-40 mV and displayed a relatively high open probability even at +/-80 mV. hVDAC3 was only slightly voltage-dependent, displaying a tendency to adopt lower-conductance states at positive voltages applied to the cis chamber. In accordance with the small conductance of the pore, expression of hVDAC3 in a porin-less yeast strain allowed only partial recovery of the growth under non-permissive conditions. CONCLUSION The observed electrophysiological properties of hVDAC3 are surprisingly different from the other isoforms and are discussed in relation to the proposed physiological role of the protein in mammalian cells.
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Patron M, Checchetto V, Raffaello A, Teardo E, Vecellio Reane D, Mantoan M, Granatiero V, Szabò I, De Stefani D, Rizzuto R. MICU1 and MICU2 finely tune the mitochondrial Ca2+ uniporter by exerting opposite effects on MCU activity. Mol Cell 2014; 53:726-37. [PMID: 24560927 PMCID: PMC3988891 DOI: 10.1016/j.molcel.2014.01.013] [Citation(s) in RCA: 386] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 12/18/2013] [Accepted: 01/16/2014] [Indexed: 02/06/2023]
Abstract
Mitochondrial calcium accumulation was recently shown to depend on a complex composed of an inner-membrane channel (MCU and MCUb) and regulatory subunits (MICU1, MCUR1, and EMRE). A fundamental property of MCU is low activity at resting cytosolic Ca(2+) concentrations, preventing deleterious Ca(2+) cycling and organelle overload. Here we demonstrate that these properties are ensured by a regulatory heterodimer composed of two proteins with opposite effects, MICU1 and MICU2, which, both in purified lipid bilayers and in intact cells, stimulate and inhibit MCU activity, respectively. Both MICU1 and MICU2 are regulated by calcium through their EF-hand domains, thus accounting for the sigmoidal response of MCU to [Ca(2+)] in situ and allowing tight physiological control. At low [Ca(2+)], the dominant effect of MICU2 largely shuts down MCU activity; at higher [Ca(2+)], the stimulatory effect of MICU1 allows the prompt response of mitochondria to Ca(2+) signals generated in the cytoplasm.
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Affiliation(s)
- Maria Patron
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58, 35131 Padova, Italy; CNR Neuroscience Institute, Via Ugo Bassi 58, 35131 Padova, Italy
| | - Vanessa Checchetto
- Department of Biology, University of Padova, Via Ugo Bassi 58, 35131 Padova, Italy
| | - Anna Raffaello
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58, 35131 Padova, Italy; CNR Neuroscience Institute, Via Ugo Bassi 58, 35131 Padova, Italy
| | - Enrico Teardo
- Department of Biology, University of Padova, Via Ugo Bassi 58, 35131 Padova, Italy
| | - Denis Vecellio Reane
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58, 35131 Padova, Italy; CNR Neuroscience Institute, Via Ugo Bassi 58, 35131 Padova, Italy
| | - Maura Mantoan
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58, 35131 Padova, Italy; CNR Neuroscience Institute, Via Ugo Bassi 58, 35131 Padova, Italy
| | - Veronica Granatiero
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58, 35131 Padova, Italy; CNR Neuroscience Institute, Via Ugo Bassi 58, 35131 Padova, Italy
| | - Ildikò Szabò
- Department of Biology, University of Padova, Via Ugo Bassi 58, 35131 Padova, Italy
| | - Diego De Stefani
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58, 35131 Padova, Italy; CNR Neuroscience Institute, Via Ugo Bassi 58, 35131 Padova, Italy.
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58, 35131 Padova, Italy; CNR Neuroscience Institute, Via Ugo Bassi 58, 35131 Padova, Italy.
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Checchetto V, Teardo E, De Stefani D, Patron M, Raffaello A, Szabò I, Rizzuto R. Electrophysiological Characterization of the Activity and Regulation of the Mitochondrial Calcium Uniporter. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.4184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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Carraretto L, Formentin E, Teardo E, Checchetto V, Tomizioli M, Morosinotto T, Giacometti GM, Finazzi G, Szabó I. A Thylakoid-Located Two-Pore K+ Channel Controls Photosynthetic Light Utilization in Plants. Science 2013; 342:114-8. [DOI: 10.1126/science.1242113] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The size of the light-induced proton motive force (pmf) across the thylakoid membrane of chloroplasts is regulated in response to environmental stimuli. Here, we describe a component of the thylakoid membrane, the two-pore potassium (K+) channel TPK3, which modulates the composition of the pmf through ion counterbalancing. Recombinant TPK3 exhibited potassium-selective channel activity sensitive to Ca2+ and H+. In Arabidopsis plants, the channel is found in the thylakoid stromal lamellae. Arabidopsis plants silenced for the TPK3 gene display reduced growth and altered thylakoid membrane organization. This phenotype reflects an impaired capacity to generate a normal pmf, which results in reduced CO2 assimilation and deficient nonphotochemical dissipation of excess absorbed light. Thus, the TPK3 channel manages the pmf necessary to convert photochemical energy into physiological functions.
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Raffaello A, De Stefani D, Sabbadin D, Teardo E, Merli G, Picard A, Checchetto V, Moro S, Szabò I, Rizzuto R. The mitochondrial calcium uniporter is a multimer that can include a dominant-negative pore-forming subunit. EMBO J 2013; 32:2362-76. [PMID: 23900286 DOI: 10.1038/emboj.2013.157] [Citation(s) in RCA: 372] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 06/09/2013] [Indexed: 12/12/2022] Open
Abstract
Mitochondrial calcium uniporter (MCU) channel is responsible for Ruthenium Red-sensitive mitochondrial calcium uptake. Here, we demonstrate MCU oligomerization by immunoprecipitation and Förster resonance energy transfer (FRET) and characterize a novel protein (MCUb) with two predicted transmembrane domains, 50% sequence similarity and a different expression profile from MCU. Based on computational modelling, MCUb includes critical amino-acid substitutions in the pore region and indeed MCUb does not form a calcium-permeable channel in planar lipid bilayers. In HeLa cells, MCUb is inserted into the oligomer and exerts a dominant-negative effect, reducing the [Ca(2+)]mt increases evoked by agonist stimulation. Accordingly, in vitro co-expression of MCUb with MCU drastically reduces the probability of observing channel activity in planar lipid bilayer experiments. These data unveil the structural complexity of MCU and demonstrate a novel regulatory mechanism, based on the inclusion of dominant-negative subunits in a multimeric channel, that underlies the fine control of the physiologically and pathologically relevant process of mitochondrial calcium homeostasis.
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Affiliation(s)
- Anna Raffaello
- Department of Biomedical Sciences, University of Padua and CNR Neuroscience Institute, Padua, Italy
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Checchetto V, Teardo E, Carraretto L, Formentin E, Bergantino E, Giacometti GM, Szabo I. Regulation of photosynthesis by ion channels in cyanobacteria and higher plants. Biophys Chem 2013; 182:51-7. [PMID: 23891570 DOI: 10.1016/j.bpc.2013.06.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/10/2013] [Accepted: 06/10/2013] [Indexed: 11/25/2022]
Abstract
Photosynthesis converts light energy into chemical energy, and supplies ATP and NADPH for CO2 fixation into carbohydrates and for the synthesis of several compounds which are essential for autotrophic growth. Oxygenic photosynthesis takes place in thylakoid membranes of chloroplasts and photosynthetic prokaryote cyanobacteria. An ancestral photoautotrophic prokaryote related to cyanobacteria has been proposed to give rise to chloroplasts of plants and algae through an endosymbiotic event. Indeed, photosynthetic complexes involved in the electron transport coupled to H(+) translocation and ATP synthesis are similar in higher plants and cyanobacteria. Furthermore, some of the protein and solute/ion conducting machineries also share common structure and function. Electrophysiological and biochemical evidence support the existence of ion channels in the thylakoid membrane in both types of organisms. By allowing specific ion fluxes across thylakoid membranes, ion channels have been hypothesized to either directly or indirectly regulate photosynthesis, by modulating the proton motive force. Recent molecular identification of some of the thylakoid-located channels allowed to obtain genetic proof in favor of such hypothesis. Furthermore, some ion channels of the envelope membrane in chloroplasts have also been shown to impact on this light-driven process. Here we give an overview of thylakoid/chloroplast located ion channels of higher plants and of cyanobacterium Synechocystis sp. PCC 6803. We focus on channels shown to be implicated in the regulation of photosynthesis and discuss the possible mechanisms of action.
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Affiliation(s)
- Vanessa Checchetto
- Department of Biology, University of Padova, viale G. Colombo 3, 35121 Padova, Italy
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Checchetto V, Formentin E, Carraretto L, Segalla A, Giacometti GM, Szabo I, Bergantino E. Functional characterization and determination of the physiological role of a calcium-dependent potassium channel from cyanobacteria. Plant Physiol 2013; 162:953-964. [PMID: 23640756 PMCID: PMC3668083 DOI: 10.1104/pp.113.215129] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 04/30/2013] [Indexed: 05/28/2023]
Abstract
Despite the important achievement of the high-resolution structures of several prokaryotic channels, current understanding of their physiological roles in bacteria themselves is still far from complete. We have identified a putative two transmembrane domain-containing channel, SynCaK, in the genome of the freshwater cyanobacterium Synechocystis sp. PCC 6803, a model photosynthetic organism. SynCaK displays significant sequence homology to MthK, a calcium-dependent potassium channel isolated from Methanobacterium thermoautotrophicum. Expression of SynCaK in fusion with enhanced GFP in mammalian Chinese hamster ovary cells' plasma membrane gave rise to a calcium-activated, potassium-selective activity in patch clamp experiments. In cyanobacteria, Western blotting of isolated membrane fractions located SynCaK mainly to the plasma membrane. To understand its physiological function, a SynCaK-deficient mutant of Synechocystis sp. PCC 6803, ΔSynCaK, has been obtained. Although the potassium content in the mutant organisms was comparable to that observed in the wild type, ΔSynCaK was characterized by a depolarized resting membrane potential, as determined by a potential-sensitive fluorescent probe. Growth of the mutant under various conditions revealed that lack of SynCaK does not impair growth under osmotic or salt stress and that SynCaK is not involved in the regulation of photosynthesis. Instead, its lack conferred an increased resistance to the heavy metal zinc, an environmental pollutant. A similar result was obtained using barium, a general potassium channel inhibitor that also caused depolarization. Our findings thus indicate that SynCaK is a functional channel and identify the physiological consequences of its deletion in cyanobacteria.
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Akai M, Onai K, Kusano M, Sato M, Redestig H, Toyooka K, Morishita M, Miyake H, Hazama A, Checchetto V, Szabò I, Matsuoka K, Saito K, Yasui M, Ishiura M, Uozumi N. Plasma membrane aquaporin AqpZ protein is essential for glucose metabolism during photomixotrophic growth of Synechocystis sp. PCC 6803. J Biol Chem 2011; 286:25224-35. [PMID: 21558269 DOI: 10.1074/jbc.m111.236380] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The genome of Synechocystis PCC 6803 contains a single gene encoding an aquaporin, aqpZ. The AqpZ protein functioned as a water-permeable channel in the plasma membrane. However, the physiological importance of AqpZ in Synechocystis remains unclear. We found that growth in glucose-containing medium inhibited proper division of ΔaqpZ cells and led to cell death. Deletion of a gene encoding a glucose transporter in the ΔaqpZ background alleviated the glucose-mediated growth inhibition of the ΔaqpZ cells. The ΔaqpZ cells swelled more than the wild type after the addition of glucose, suggesting an increase in cytosolic osmolarity. This was accompanied by a down-regulation of the pentose phosphate pathway and concurrent glycogen accumulation. Metabolite profiling by GC/TOF-MS of wild-type and ΔaqpZ cells revealed a relative decrease of intermediates of the tricarboxylic acid cycle and certain amino acids in the mutant. The changed levels of metabolites may have been the cause for the observed decrease in growth rate of the ΔaqpZ cells along with decreased PSII activity at pH values ranging from 7.5 to 8.5. A mutant in sll1961, encoding a putative transcription factor, and a Δhik31 mutant, lacking a putative glucose-sensing kinase, both exhibited higher glucose sensitivity than the ΔaqpZ cells. Examination of protein expression indicated that sll1961 functioned as a positive regulator of aqpZ gene expression but not as the only regulator. Overall, the ΔaqpZ cells showed defects in macronutrient metabolism, pH homeostasis, and cell division under photomixotrophic conditions, consistent with an essential role of AqpZ in glucose metabolism.
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Affiliation(s)
- Masaro Akai
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University Aobayama 6-6-07, Sendai 980-8579, Japan
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De Marchi U, Checchetto V, Zanetti M, Teardo E, Soccio M, Formentin E, Giacometti GM, Pastore D, Zoratti M, Szabò I. ATP-sensitive cation-channel in wheat (Triticum durum Desf.): identification and characterization of a plant mitochondrial channel by patch-clamp. Cell Physiol Biochem 2011; 26:975-82. [PMID: 21220928 DOI: 10.1159/000324010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2010] [Indexed: 11/19/2022] Open
Abstract
Indirect evidence points to the presence of K(+) channels in plant mitochondria. In the present study, we report the results of the first patch clamp experiments on plant mitochondria. Single-channel recordings in 150 mM potassium gluconate have allowed the biophysical characterization of a channel with a conductance of 150 pS in the inner mitochondrial membrane of mitoplasts obtained from wheat (Triticum durum Desf.). The channel displayed sharp voltage sensitivity, permeability to potassium and cation selectivity. ATP in the mM concentration range completely abolished the activity. We discuss the possible molecular identity of the channel and its possible role in the defence mechanisms against oxidative stress in plants.
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Affiliation(s)
- Umberto De Marchi
- Department of Experimental Biomedical Sciences, CNR Institute of Neuroscience, University of Padova, Padova, Italy.
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Zanetti M, Teardo E, La Rocca N, Zulkifli L, Checchetto V, Shijuku T, Sato Y, Giacometti GM, Uozumi N, Bergantino E, Szabò I. A novel potassium channel in photosynthetic cyanobacteria. PLoS One 2010; 5:e10118. [PMID: 20404935 PMCID: PMC2853561 DOI: 10.1371/journal.pone.0010118] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Accepted: 03/12/2010] [Indexed: 12/20/2022] Open
Abstract
Elucidation of the structure-function relationship of a small number of prokaryotic ion channels characterized so far greatly contributed to our knowledge on basic mechanisms of ion conduction. We identified a new potassium channel (SynK) in the genome of the cyanobacterium Synechocystis sp. PCC6803, a photosynthetic model organism. SynK, when expressed in a K+-uptake-system deficient E.coli strain, was able to recover growth of these organisms. The protein functions as a potassium selective ion channel when expressed in Chinese Hamster Ovary cells. The location of SynK in cyanobacteria in both thylakoid and plasmamembranes was revealed by immunogold electron microscopy and Western blotting of isolated membrane fractions. SynK seems to be conserved during evolution, giving rise to a TPK (two-pore K+ channel) family member which is shown here to be located in the thylakoid membrane of Arabidopsis. Our work characterizes a novel cyanobacterial potassium channel and indicates the molecular nature of the first higher plant thylakoid cation channel, opening the way to functional studies.
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Affiliation(s)
| | - Enrico Teardo
- Department of Biology, University of Padova, Padova, Italy
| | | | - Lalu Zulkifli
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
| | | | - Toshiaki Shijuku
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
| | - Yuki Sato
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
| | | | - Noboyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
| | | | - Ildikò Szabò
- Department of Biology, University of Padova, Padova, Italy
- * E-mail: (EB); (IS)
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