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Szewczyk A. Understanding mitochondrial potassium channels: 33 years after discovery. Acta Biochim Pol 2024; 71:13126. [PMID: 38863652 PMCID: PMC11165062 DOI: 10.3389/abp.2024.13126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2024] [Accepted: 05/20/2024] [Indexed: 06/13/2024]
Abstract
Mitochondrial investigations have extended beyond their traditional functions, covering areas such as ATP synthesis and metabolism. Mitochondria are now implicated in new functional areas such as cytoprotection, cellular senescence, tumor function and inflammation. The basis of these new areas still relies on fundamental biochemical/biophysical mitochondrial functions such as synthesis of reactive oxygen species, mitochondrial membrane potential, and the integrity of the inner mitochondrial membrane i.e., the passage of various molecules through the mitochondrial membranes. In this view transport of potassium cations, known as the potassium cycle, plays an important role. It is believed that K+ influx is mediated by various potassium channels present in the inner mitochondrial membrane. In this article, we present an overview of the key findings and characteristics of mitochondrial potassium channels derived from research of many groups conducted over the past 33 years. We propose a list of six fundamental observations and most important ideas dealing with mitochondrial potassium channels. We also discuss the contemporary challenges and future prospects associated with research on mitochondrial potassium channels.
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Affiliation(s)
- Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
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2
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External Hemin as an Inhibitor of Mitochondrial Large-Conductance Calcium-Activated Potassium Channel Activity. Int J Mol Sci 2022; 23:ijms232113391. [DOI: 10.3390/ijms232113391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 10/26/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial large-conductance calcium-activated potassium channel (mitoBKCa) is located in the inner mitochondrial membrane and seems to play a crucial role in cytoprotection. The mitoBKCa channel is regulated by many modulators, including activators, such as calcium ions and inhibitors, such as heme and its oxidized form hemin. Heme/hemin binds to the heme-binding motif (CXXCH) located between two RCK domains present in the mitochondrial matrix. In the present study, we used the patch-clamp technique in the outside-out configuration to record the activity of mitoBKCa channels. This allowed for the application of channel modulators to the intermembrane-space side of the mitoBKCa. We found that hemin applied in this configuration inhibits the activity of mitoBKCa. In addition, we proved that the observed hemin effect is specific and it is not due to its interaction with the inner mitochondrial membrane. Our data suggest the existence of a new potential heme/hemin binding site in the structure of the mitoBKCa channel located on the mitochondrial intermembrane space side, which could constitute a new way for the regulation of mitoBKCa channel activity.
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3
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Kulawiak B, Szewczyk A. Current Challenges of Mitochondrial Potassium Channel Research. Front Physiol 2022; 13:907015. [PMID: 35711307 PMCID: PMC9193220 DOI: 10.3389/fphys.2022.907015] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 05/16/2022] [Indexed: 11/13/2022] Open
Abstract
In this paper, the current challenges of mitochondrial potassium channels research were critically reviewed. Even though recent progress in understanding K+ traffic in mitochondria has been substantial, some basic issues of this process remain unresolved. Here, we focused on the critical discussion of the molecular identity of various mitochondrial potassium channels. This point helps to clarify why there are different potassium channels in specific mitochondria. We also described interactions of mitochondrial potassium channel subunits with other mitochondrial proteins. Posttranslational modifications of mitochondrial potassium channels and their import are essential but unexplored research areas. Additionally, problems with the pharmacological targeting of mitochondrial potassium channel were illustrated. Finally, the limitation of the techniques used to measure mitochondrial potassium channels was explained. We believe that recognizing these problems may be interesting for readers but will also help to progress the field of mitochondrial potassium channels.
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Affiliation(s)
- Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
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4
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Szajko K, Sołtys-Kalina D, Heidorn-Czarna M, Smyda-Dajmund P, Wasilewicz-Flis I, Jańska H, Marczewski W. Transcriptomic and proteomic data provide new insights into cold-treated potato tubers with T- and D-type cytoplasm. PLANTA 2022; 255:97. [PMID: 35380306 PMCID: PMC8983635 DOI: 10.1007/s00425-022-03879-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 03/17/2022] [Indexed: 06/14/2023]
Abstract
Tuber-omics in potato with the T- and D-types of cytoplasm showed different sets of differentially expressed genes and proteins in response to cold storage. For the first time, we report differences in gene and protein expression in potato (Solanum tuberosum L.) tubers possessing the T- or D-type cytoplasm. Two F1 diploid reciprocal populations, referred to as T and D, were used. The pooling strategy was applied for detection of differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) in tubers consisting of extreme chip colour after cold storage. RNA and protein bulks were constructed from contrasting phenotypes. We recognized 48 and 15 DEGs for the T and D progenies, respectively. DEPs were identified in the amyloplast and mitochondrial fractions. In the T-type cytoplasm, only 2 amyloplast-associated and 5 mitochondria-associated DEPs were detected. Of 37 mitochondria-associated DEPs in the D-type cytoplasm, there were 36 downregulated DEPs in the dark chip colour bulks. These findings suggest that T- and D-type of cytoplasm might influence sugar accumulation in cold-stored potato tubers in different ways. We showed that the mt/nucDNA ratio was higher in D-possessing tubers after cold storage than in T progeny. For the D-type cytoplasm, the pt/nucDNA ratio was higher for tubers characterized by dark chip colour than for those with light chip colour. Our findings suggest that T- and D-type cytoplasm might influence sugar accumulation in cold-stored potato tubers in different ways.
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Affiliation(s)
- Katarzyna Szajko
- Plant Breeding and Acclimatization Institute-National Research Institute, Platanowa 19, 05-831, Młochów, Poland.
| | - Dorota Sołtys-Kalina
- Plant Breeding and Acclimatization Institute-National Research Institute, Platanowa 19, 05-831, Młochów, Poland
| | | | - Paulina Smyda-Dajmund
- Plant Breeding and Acclimatization Institute-National Research Institute, Platanowa 19, 05-831, Młochów, Poland
| | - Iwona Wasilewicz-Flis
- Plant Breeding and Acclimatization Institute-National Research Institute, Platanowa 19, 05-831, Młochów, Poland
| | - Hanna Jańska
- Faculty of Biotechnology, University of Wroclaw, 50-383, Wrocław, Poland
| | - Waldemar Marczewski
- Plant Breeding and Acclimatization Institute-National Research Institute, Platanowa 19, 05-831, Młochów, Poland.
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Paweł Kampa R, Gliździńska A, Szewczyk A, Bednarczyk P, Filipek S. Flavonoid quercetin abolish paxilline inhibition of the mitochondrial bk channel. Mitochondrion 2022; 65:23-32. [DOI: 10.1016/j.mito.2022.04.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 03/30/2022] [Accepted: 04/27/2022] [Indexed: 12/17/2022]
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6
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Methods of Measuring Mitochondrial Potassium Channels: A Critical Assessment. Int J Mol Sci 2022; 23:ijms23031210. [PMID: 35163132 PMCID: PMC8835872 DOI: 10.3390/ijms23031210] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 12/22/2022] Open
Abstract
In this paper, the techniques used to study the function of mitochondrial potassium channels are critically reviewed. The majority of these techniques have been known for many years as a result of research on plasma membrane ion channels. Hence, in this review, we focus on the critical evaluation of techniques used in the studies of mitochondrial potassium channels, describing their advantages and limitations. Functional analysis of mitochondrial potassium channels in comparison to that of plasmalemmal channels presents additional experimental challenges. The reliability of functional studies of mitochondrial potassium channels is often affected by the need to isolate mitochondria and by functional properties of mitochondria such as respiration, metabolic activity, swelling capacity, or high electrical potential. Three types of techniques are critically evaluated: electrophysiological techniques, potassium flux measurements, and biochemical techniques related to potassium flux measurements. Finally, new possible approaches to the study of the function of mitochondrial potassium channels are presented. We hope that this review will assist researchers in selecting reliable methods for studying, e.g., the effects of drugs on mitochondrial potassium channel function. Additionally, this review should aid in the critical evaluation of the results reported in various articles on mitochondrial potassium channels.
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7
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González-Cota AL, Santana-Calvo C, Servín-Vences R, Orta G, Balderas E. Regulatory mechanisms of mitochondrial BK Ca channels. Channels (Austin) 2021; 15:424-437. [PMID: 33955332 PMCID: PMC8117780 DOI: 10.1080/19336950.2021.1919463] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 04/05/2021] [Accepted: 04/05/2021] [Indexed: 02/06/2023] Open
Abstract
The mitochondrial BKCa channel (mitoBKCa) is a splice variant of plasma membrane BKCa (Maxi-K, BKCa, Slo1, KCa1.1). While a high-resolution structure of mitoBKCa is not available yet, functional and structural studies of the plasma membrane BKCa have provided important clues on the gating of the channel by voltage and Ca2+, as well as the interaction with auxiliary subunits. To date, we know that the control of expression of mitoBKCa, targeting and voltage-sensitivity strongly depends on its association with its regulatory β1-subunit, which overall participate in the control of mitochondrial Ca2+-overload in cardiac myocytes. Moreover, novel regulatory mechanisms of mitoBKCa such as β-subunits and amyloid-β have recently been proposed. However, major basic questions including how the regulatory BKCa-β1-subunit reaches mitochondria and the mechanism through which amyloid-β impairs mitoBKCa channel function remain to be addressed.
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Affiliation(s)
- Ana L. González-Cota
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, UNAM. Av. Universidad 2001, Cuernavaca, Morelos, México
| | - Carmen Santana-Calvo
- Instituto Gulbenkian de Ciência. Rua da Quinta Grande 6, Oeiras, Portugal
- Instituto de Tecnologia Química e Biológica, Universida de Nova de Lisboa. Av. da República, Oeiras, Portugal
| | - Rocío Servín-Vences
- Department of Neuroscience, The Scripps Research Institute. 10550 North Torrey Pines Road, La Jolla, CA, USA
| | - Gerardo Orta
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, UNAM. Av. Universidad 2001, Cuernavaca, Morelos, México
| | - Enrique Balderas
- Nora Eccles Harrison Cardiovascular Research & Training Institute, University of Utah, Salt Lake City, UT, USA
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González-Sanabria N, Echeverría F, Segura I, Alvarado-Sánchez R, Latorre R. BK in Double-Membrane Organelles: A Biophysical, Pharmacological, and Functional Survey. Front Physiol 2021; 12:761474. [PMID: 34764886 PMCID: PMC8577798 DOI: 10.3389/fphys.2021.761474] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 09/29/2021] [Indexed: 12/04/2022] Open
Abstract
In the 1970s, calcium-activated potassium currents were recorded for the first time. In 10years, this Ca2+-activated potassium channel was identified in rat skeletal muscle, chromaffin cells and characterized in skeletal muscle membranes reconstituted in lipid bilayers. This calcium- and voltage-activated potassium channel, dubbed BK for “Big K” due to its large ionic conductance between 130 and 300 pS in symmetric K+. The BK channel is a tetramer where the pore-forming α subunit contains seven transmembrane segments. It has a modular architecture containing a pore domain with a highly potassium-selective filter, a voltage-sensor domain and two intracellular Ca2+ binding sites in the C-terminus. BK is found in the plasma membrane of different cell types, the inner mitochondrial membrane (mitoBK) and the nuclear envelope’s outer membrane (nBK). Like BK channels in the plasma membrane (pmBK), the open probability of mitoBK and nBK channels are regulated by Ca2+ and voltage and modulated by auxiliary subunits. BK channels share common pharmacology to toxins such as iberiotoxin, charybdotoxin, paxilline, and agonists of the benzimidazole family. However, the precise role of mitoBK and nBK remains largely unknown. To date, mitoBK has been reported to play a role in protecting the heart from ischemic injury. At the same time, pharmacology suggests that nBK has a role in regulating nuclear Ca2+, membrane potential and expression of eNOS. Here, we will discuss at the biophysical level the properties and differences of mitoBK and nBK compared to those of pmBK and their pharmacology and function.
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Affiliation(s)
- Naileth González-Sanabria
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Felipe Echeverría
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Ignacio Segura
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Rosangelina Alvarado-Sánchez
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Ramon Latorre
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
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Wrzosek A, Augustynek B, Żochowska M, Szewczyk A. Mitochondrial Potassium Channels as Druggable Targets. Biomolecules 2020; 10:E1200. [PMID: 32824877 PMCID: PMC7466137 DOI: 10.3390/biom10081200] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 08/03/2020] [Accepted: 08/13/2020] [Indexed: 12/16/2022] Open
Abstract
Mitochondrial potassium channels have been described as important factors in cell pro-life and death phenomena. The activation of mitochondrial potassium channels, such as ATP-regulated or calcium-activated large conductance potassium channels, may have cytoprotective effects in cardiac or neuronal tissue. It has also been shown that inhibition of the mitochondrial Kv1.3 channel may lead to cancer cell death. Hence, in this paper, we examine the concept of the druggability of mitochondrial potassium channels. To what extent are mitochondrial potassium channels an important, novel, and promising drug target in various organs and tissues? The druggability of mitochondrial potassium channels will be discussed within the context of channel molecular identity, the specificity of potassium channel openers and inhibitors, and the unique regulatory properties of mitochondrial potassium channels. Future prospects of the druggability concept of mitochondrial potassium channels will be evaluated in this paper.
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Affiliation(s)
| | | | | | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (A.W.); (B.A.); (M.Ż.)
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10
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Signaling pathways targeting mitochondrial potassium channels. Int J Biochem Cell Biol 2020; 125:105792. [PMID: 32574707 DOI: 10.1016/j.biocel.2020.105792] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/08/2020] [Accepted: 06/11/2020] [Indexed: 12/11/2022]
Abstract
In this review, we describe key signaling pathways regulating potassium channels present in the inner mitochondrial membrane. The signaling cascades covered here include phosphorylation, redox reactions, modulation by calcium ions and nucleotides. The following types of potassium channels have been identified in the inner mitochondrial membrane of various tissues: ATP-sensitive, Ca2+-activated, voltage-gated and two-pore domain potassium channels. The direct roles of these channels involve regulation of mitochondrial respiration, membrane potential and synthesis of reactive oxygen species (ROS). Changes in channel activity lead to diverse pro-life and pro-death responses in different cell types. Hence, characterizing the signaling pathways regulating mitochondrial potassium channels will facilitate understanding the physiological role of these proteins. Additionally, we describe in this paper certain regulatory mechanisms, which are unique to mitochondrial potassium channels.
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11
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Channels and transporters for inorganic ions in plant mitochondria: Prediction and facts. Mitochondrion 2020; 53:224-233. [PMID: 32540403 DOI: 10.1016/j.mito.2020.05.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 05/01/2020] [Accepted: 05/22/2020] [Indexed: 02/07/2023]
Abstract
Mitochondria are crucial bioenergetic organelles for providing different metabolites, including ATP, to sustain cell growth both in animals and in plants. These organelles, delimited by two membranes (outer and inner mitochondrial membrane), maintain their function by an intensive communication with other organelles as well as with the cytosol. Transport of metabolites across the two membranes, but also that of inorganic ions, takes place through specific ion channels and transporters and plays a crucial role in ensuring an adequate ionic milieu within the mitochondria. In the present review we briefly summarize the current knowledge about plant mitochondrial ion channels and transporters in comparison to those of animal mitochondria and examine the possible molecular identity of the so far unidentified transport systems taking into account subcellular targeting predictions and data from literature.
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Walewska A, Kulawiak B, Szewczyk A, Koprowski P. Mechanosensitivity of mitochondrial large-conductance calcium-activated potassium channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:797-805. [PMID: 29775559 DOI: 10.1016/j.bbabio.2018.05.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 04/29/2018] [Accepted: 05/10/2018] [Indexed: 12/01/2022]
Abstract
Potassium channels have been discovered in the inner mitochondrial membrane of various cells. These channels can regulate the mitochondrial membrane potential, the matrix volume, respiration and reactive species generation. Therefore, it is believed that their activation is cytoprotective in various tissues. In our study, the single-channel activity of a large-conductance calcium-activated potassium channel (mitoBKCa) was measured by the patch-clamp technique on mitoplasts derived from mitochondria isolated from human glioma U-87 MG cells. Here, we show for the first time that mechanical stimulation of mitoBKCa channels results in an increased probability of channel opening. However, the mechanosensitivity of mitoBKCa channels was variable with some channels exhibiting no mechanosensitivity. We detected the expression of mechanosensitive BKCa-STREX exon in U-87 MG cells and hypotesize, based on previous studies demonstrating the presence of multiple BKCa splice variants that variable mechanosensitivity of mitoBKCa could be the result of the presence of diverse BKCa isoforms in mitochondria of U-87 MG cells. Our findings indicate the possible involvement of the mitoBKCa channel in mitochondria activities in which changes in membrane tension and shape play a crucial role, such as fusion/fission and cristae remodeling.
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Affiliation(s)
- Agnieszka Walewska
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Piotr Koprowski
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland.
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Augustynek B, Kunz WS, Szewczyk A. Guide to the Pharmacology of Mitochondrial Potassium Channels. Handb Exp Pharmacol 2017; 240:103-127. [PMID: 27838853 DOI: 10.1007/164_2016_79] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This chapter provides a critical overview of the available literature on the pharmacology of mitochondrial potassium channels. In the first part, the reader is introduced to the topic, and eight known protein contributors to the potassium permeability of the inner mitochondrial membrane are presented. The main part of this chapter describes the basic characteristics of each channel type mentioned in the introduction. However, the most important and valuable information included in this chapter concerns the pharmacology of mitochondrial potassium channels. Several available channel modulators are critically evaluated and rated by suitability for research use. The last figure of this chapter shows the results of this evaluation at a glance. Thus, this chapter can be very useful for beginners in this field. It is intended to be a time- and resource-saving guide for those searching for proper modulators of mitochondrial potassium channels.
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Affiliation(s)
- Bartłomiej Augustynek
- Laboratory of Intracellular Ion Channels, Department of Biochemistry, Nencki Institute of Experimental Biology, 3 Pasteur Street, 02-093, Warsaw, Poland
| | - Wolfram S Kunz
- Department of Epileptology, University of Bonn, Sigmund-Freud-Str. 25, 53105, Bonn, Germany
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Department of Biochemistry, Nencki Institute of Experimental Biology, 3 Pasteur Street, 02-093, Warsaw, Poland.
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A large-conductance calcium-regulated K+ channel in human dermal fibroblast mitochondria. Biochem J 2016; 473:4457-4471. [PMID: 27729542 DOI: 10.1042/bcj20160732] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 09/23/2016] [Accepted: 10/10/2016] [Indexed: 02/06/2023]
Abstract
Potassium channels have been found in the inner mitochondrial membrane of various cells. These channels regulate the mitochondrial membrane potential, respiration and production of reactive oxygen species. In the present study, we identified the activity of a mitochondrial large-conductance Ca2+-regulated potassium channel (mitoBKCa channel) in mitoplasts isolated from a primary human dermal fibroblast cell line. A potassium selective current was recorded with a mean conductance of 280 ± 2 pS in a symmetrical 150 mM KCl solution. The mitoBKCa channel was activated by the Ca2+ and by potassium channel opener NS1619. The channel activity was irreversibly inhibited by paxilline, a selective inhibitor of the BKCa channels. In isolated fibroblast mitochondria NS1619 depolarized the mitochondrial membrane potential, stimulated nonphosphorylating respiration and decreased superoxide formation. Additionally, the α- and β-subunits (predominantly the β3-form) of the BKCa channels were identified in fibroblast mitochondria. Our findings indicate, for the first time, the presence of a large-conductance Ca2+-regulated potassium channel in the inner mitochondrial membrane of human dermal fibroblasts.
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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. FRONTIERS IN PLANT SCIENCE 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] [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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Checchetto V, Teardo E, Carraretto L, Leanza L, Szabo I. Physiology of intracellular potassium channels: A unifying role as mediators of counterion fluxes? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 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] [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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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. MOLECULAR 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] [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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18
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Laskowski M, Augustynek B, Kulawiak B, Koprowski P, Bednarczyk P, Jarmuszkiewicz W, Szewczyk A. What do we not know about mitochondrial potassium channels? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1247-1257. [PMID: 26951942 DOI: 10.1016/j.bbabio.2016.03.007] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 03/02/2016] [Accepted: 03/03/2016] [Indexed: 01/14/2023]
Abstract
In this review, we summarize our knowledge about mitochondrial potassium channels, with a special focus on unanswered questions in this field. The following potassium channels have been well described in the inner mitochondrial membrane: ATP-regulated potassium channel, Ca(2+)-activated potassium channel, the voltage-gated Kv1.3 potassium channel, and the two-pore domain TASK-3 potassium channel. The primary functional roles of these channels include regulation of mitochondrial respiration and the alteration of membrane potential. Additionally, they modulate the mitochondrial matrix volume and the synthesis of reactive oxygen species by mitochondria. Mitochondrial potassium channels are believed to contribute to cytoprotection and cell death. In this paper, we discuss fundamental issues concerning mitochondrial potassium channels: their molecular identity, channel pharmacology and functional properties. Attention will be given to the current problems present in our understanding of the nature of mitochondrial potassium channels. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.
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Affiliation(s)
- Michał Laskowski
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Bartłomiej Augustynek
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Piotr Koprowski
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Piotr Bednarczyk
- Department of Biophysics, Warsaw University of Life Sciences - SGGW, 159 Nowoursynowska St., 02-776 Warsaw, Poland
| | - Wieslawa Jarmuszkiewicz
- Laboratory of Bioenergetics, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland.
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Trono D, Laus MN, Soccio M, Alfarano M, Pastore D. Modulation of Potassium Channel Activity in the Balance of ROS and ATP Production by Durum Wheat Mitochondria-An Amazing Defense Tool Against Hyperosmotic Stress. FRONTIERS IN PLANT SCIENCE 2015; 6:1072. [PMID: 26648958 PMCID: PMC4664611 DOI: 10.3389/fpls.2015.01072] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 11/16/2015] [Indexed: 05/03/2023]
Abstract
In plants, the existence of a mitochondrial potassium channel was firstly demonstrated about 15 years ago in durum wheat as an ATP-dependent potassium channel (PmitoKATP). Since then, both properties of the original PmitoKATP and occurrence of different mitochondrial potassium channels in a number of plant species (monocotyledonous and dicotyledonous) and tissues/organs (etiolated and green) have been shown. Here, an overview of the current knowledge is reported; in particular, the issue of PmitoKATP physiological modulation is addressed. Similarities and differences with other potassium channels, as well as possible cross-regulation with other mitochondrial proteins (Plant Uncoupling Protein, Alternative Oxidase, Plant Inner Membrane Anion Channel) are also described. PmitoKATP is inhibited by ATP and activated by superoxide anion, as well as by free fatty acids (FFAs) and acyl-CoAs. Interestingly, channel activation increases electrophoretic potassium uptake across the inner membrane toward the matrix, so collapsing membrane potential (ΔΨ), the main component of the protonmotive force (Δp) in plant mitochondria; moreover, cooperation between PmitoKATP and the K(+)/H(+) antiporter allows a potassium cycle able to dissipate also ΔpH. Interestingly, ΔΨ collapse matches with an active control of mitochondrial reactive oxygen species (ROS) production. Fully open channel is able to lower superoxide anion up to 35-fold compared to a condition of ATP-inhibited channel. On the other hand, ΔΨ collapse by PmitoKATP was unexpectedly found to not affect ATP synthesis via oxidative phosphorylation. This may probably occur by means of a controlled collapse due to ATP inhibition of PmitoKATP; this brake to the channel activity may allow a loss of the bulk phase Δp, but may preserve a non-classically detectable localized driving force for ATP synthesis. This ability may become crucial under environmental/oxidative stress. In particular, under moderate hyperosmotic stress (mannitol or NaCl), PmitoKATP was found to be activated by ROS, so inhibiting further large-scale ROS production according to a feedback mechanism; moreover, a stress-activated phospholipase A2 may generate FFAs, further activating the channel. In conclusion, a main property of PmitoKATP is the ability to keep in balance the control of harmful ROS with the mitochondrial/cellular bioenergetics, thus preserving ATP for energetic needs of cell defense under stress.
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Affiliation(s)
- Daniela Trono
- Consiglio per la Ricerca in Agricoltura e l’Analisi dell’Economia Agraria, Centro di Ricerca per la Cerealicoltura, Foggia, Italy
| | - Maura N. Laus
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
| | - Mario Soccio
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
| | - Michela Alfarano
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
| | - Donato Pastore
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
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20
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Laskowski M, Kicinska A, Szewczyk A, Jarmuszkiewicz W. Mitochondrial large-conductance potassium channel from Dictyostelium discoideum. Int J Biochem Cell Biol 2015; 60:167-75. [DOI: 10.1016/j.biocel.2015.01.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 12/02/2014] [Accepted: 01/07/2015] [Indexed: 12/23/2022]
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21
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Yu Q, Zhang B, Yang B, Chen J, Wang H, Jia C, Ding X, Xu N, Dong Y, Zhang B, Xing L, Li M. Interaction among the vacuole, the mitochondria, and the oxidative stress response is governed by the transient receptor potential channel in Candida albicans. Free Radic Biol Med 2014; 77:152-67. [PMID: 25308698 DOI: 10.1016/j.freeradbiomed.2014.09.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 09/01/2014] [Accepted: 09/04/2014] [Indexed: 12/22/2022]
Abstract
Candida albicans is one of the most important opportunistic pathogens, causing both mucosal candidiasis and life-threatening systemic infections. To survive in the host immune defense system, this pathogen uses an elaborate signaling network to recognize and respond to oxidative stress, which is essential for its pathogenicity. However, the exact mechanisms that this fungus employs to integrate the oxidative stress response (OSR) with functions of various organelles remain uncharacterized. Our previous work implicated a connection between the calcium signaling system and the OSR. In this study, we find that the vacuolar transient receptor potential (TRP) channel Yvc1, one of the calcium signaling members, plays a critical role in cell tolerance to oxidative stress. We further provide evidence that this channel is required not only for activation of Cap1-related transcription of OSR genes but also for maintaining the stability of both the mitochondria and the vacuole in a potassium- and calcium-dependent manner. Element assays reveal that this TRP channel affects calcium influx and potassium transport from the vacuole to the mitochondria. Therefore, the TRP channel governs the novel interaction among the OSR, the vacuole, and the mitochondria by mediating ion transport in this pathogen under oxidative stress.
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Affiliation(s)
- Qilin Yu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China
| | - Bing Zhang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China
| | - Baopeng Yang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China
| | - Jiatong Chen
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China
| | - Hui Wang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China; Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China
| | - Chang Jia
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China
| | - Xiaohui Ding
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China
| | - Ning Xu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China
| | - Yijie Dong
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China
| | - Biao Zhang
- Tianjin Traditional Chinese Medicine University, Tianjin 300193, People's Republic of China
| | - Laijun Xing
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China
| | - Mingchun Li
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Science, Nankai University, Tianjin 300071, People's Republic of China.
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22
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Trono D, Laus MN, Soccio M, Pastore D. Transport pathways--proton motive force interrelationship in durum wheat mitochondria. Int J Mol Sci 2014; 15:8186-215. [PMID: 24821541 PMCID: PMC4057727 DOI: 10.3390/ijms15058186] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 04/18/2014] [Accepted: 04/24/2014] [Indexed: 12/25/2022] Open
Abstract
In durum wheat mitochondria (DWM) the ATP-inhibited plant mitochondrial potassium channel (PmitoK(ATP)) and the plant uncoupling protein (PUCP) are able to strongly reduce the proton motive force (pmf) to control mitochondrial production of reactive oxygen species; under these conditions, mitochondrial carriers lack the driving force for transport and should be inactive. However, unexpectedly, DWM uncoupling by PmitoK(ATP) neither impairs the exchange of ADP for ATP nor blocks the inward transport of Pi and succinate. This uptake may occur via the plant inner membrane anion channel (PIMAC), which is physiologically inhibited by membrane potential, but unlocks its activity in de-energized mitochondria. Probably, cooperation between PIMAC and carriers may accomplish metabolite movement across the inner membrane under both energized and de-energized conditions. PIMAC may also cooperate with PmitoK(ATP) to transport ammonium salts in DWM. Interestingly, this finding may trouble classical interpretation of in vitro mitochondrial swelling; instead of free passage of ammonia through the inner membrane and proton symport with Pi, that trigger metabolite movements via carriers, transport of ammonium via PmitoK(ATP) and that of the counteranion via PIMAC may occur. Here, we review properties, modulation and function of the above reported DWM channels and carriers to shed new light on the control that they exert on pmf and vice-versa.
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Affiliation(s)
- Daniela Trono
- Consiglio per la Ricerca e la sperimentazione in Agricoltura, Centro di Ricerca per la Cerealicoltura, S.S. 673 Km 25, 71122 Foggia, Italy.
| | - Maura N Laus
- Dipartimento di Scienze Agrarie, degli Alimenti e dell'Ambiente, Università di Foggia, Via Napoli 25, 71122 Foggia, Italy.
| | - Mario Soccio
- Dipartimento di Scienze Agrarie, degli Alimenti e dell'Ambiente, Università di Foggia, Via Napoli 25, 71122 Foggia, Italy.
| | - Donato Pastore
- Dipartimento di Scienze Agrarie, degli Alimenti e dell'Ambiente, Università di Foggia, Via Napoli 25, 71122 Foggia, Italy.
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23
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Potassium channel in the mitochondria of human keratinocytes. J Invest Dermatol 2013; 134:764-772. [PMID: 24126847 DOI: 10.1038/jid.2013.422] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 08/21/2013] [Accepted: 09/04/2013] [Indexed: 11/08/2022]
Abstract
The activation of mitochondrial potassium channels induces cytoprotection in various cell types. Hence, the identification of ion channels present in the inner mitochondrial membrane of keratinocytes is important in distinguishing possible protective mechanisms in these cells. In this paper, inner membrane mitochondrial ion channels of the human keratinocyte HaCaT cell line were investigated using a patch-clamp technique. We observed potassium-selective channel activity with a conductance of 83 pS at positive voltages. The I-V curve indicates that the observed channel has rectifying properties. Moreover, the channel activity was inhibited by acidic pH and 1 mM lidocaine. Using reverse transcriptase-PCR, we found an mRNA transcript for the TASK-3 (tandem pore domain acid-sensitive K channels) channel. We observed co-localization of the TASK-3 protein and a mitochondrial marker in the mitochondria of HaCaT cells. Additionally, we showed that TASK-3 knockdown HaCaT cells markedly decreased viability after UVB radiation exposure compared with control cells. In summary, the single-channel activity and properties of a mitochondrial potassium channel in a keratinocyte HaCaT cell line have been described.
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Pastore D, Soccio M, Laus MN, Trono D. The uniqueness of the plant mitochondrial potassium channel. BMB Rep 2013; 46:391-7. [PMID: 23977986 PMCID: PMC4133908 DOI: 10.5483/bmbrep.2013.46.8.075] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 04/11/2013] [Accepted: 04/11/2013] [Indexed: 01/27/2023] Open
Abstract
The ATP-inhibited Plant Mitochondrial K(+) Channel (PmitoKATP) was discovered about fifteen years ago in Durum Wheat Mitochondria (DWM). PmitoKATP catalyses the electrophoretic K(+) uniport through the inner mitochondrial membrane; moreover, the co-operation between PmitoKATP and K(+)/H(+) antiporter allows such a great operation of a K(+) cycle to collapse mitochondrial membrane potential (ΔΨ) and ΔpH, thus impairing protonmotive force (Δp). A possible physiological role of such ΔΨ control is the restriction of harmful reactive oxygen species (ROS) production under environmental/oxidative stress conditions. Interestingly, DWM lacking Δp were found to be nevertheless fully coupled and able to regularly accomplish ATP synthesis; this unexpected behaviour makes necessary to recast in some way the classical chemiosmotic model. In the whole, PmitoKATP may oppose to large scale ROS production by lowering ΔΨ under environmental/oxidative stress, but, when stress is moderate, this occurs without impairing ATP synthesis in a crucial moment for cell and mitochondrial bioenergetics.
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Affiliation(s)
- Donato Pastore
- Dipartimento di Scienze Agrarie, degli Alimenti e dell'Ambiente, Università di Foggia, Via Napoli 25-71122 Foggia, Italy.
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25
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Putative Structural and Functional Coupling of the Mitochondrial BKCa Channel to the Respiratory Chain. PLoS One 2013; 8:e68125. [PMID: 23826369 PMCID: PMC3694950 DOI: 10.1371/journal.pone.0068125] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 05/30/2013] [Indexed: 01/10/2023] Open
Abstract
Potassium channels have been found in the inner mitochondrial membranes of various cells. These channels regulate the mitochondrial membrane potential, the matrix volume and respiration. The activation of these channels is cytoprotective. In our study, the single-channel activity of a large-conductance Ca(2+)-regulated potassium channel (mitoBKCa channel) was measured by patch-clamping mitoplasts isolated from the human astrocytoma (glioblastoma) U-87 MG cell line. A potassium-selective current was recorded with a mean conductance of 290 pS in symmetrical 150 mM KCl solution. The channel was activated by Ca(2+) at micromolar concentrations and by the potassium channel opener NS1619. The channel was inhibited by paxilline and iberiotoxin, known inhibitors of BKCa channels. Western blot analysis, immuno-gold electron microscopy, high-resolution immunofluorescence assays and polymerase chain reaction demonstrated the presence of the BKCa channel β4 subunit in the inner mitochondrial membrane of the human astrocytoma cells. We showed that substrates of the respiratory chain, such as NADH, succinate, and glutamate/malate, decrease the activity of the channel at positive voltages. This effect was abolished by rotenone, antimycin and cyanide, inhibitors of the respiratory chain. The putative interaction of the β4 subunit of mitoBKCa with cytochrome c oxidase was demonstrated using blue native electrophoresis. Our findings indicate possible structural and functional coupling of the mitoBKCa channel with the mitochondrial respiratory chain in human astrocytoma U-87 MG cells.
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26
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A new simple fluorimetric method to assay cytosolic ATP content: application to durum wheat seedlings to assess modulation of mitochondrial potassium channel and uncoupling protein activity under hyperosmotic stress. Biologia (Bratisl) 2013. [DOI: 10.2478/s11756-013-0176-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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27
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Bednarczyk P, Koziel A, Jarmuszkiewicz W, Szewczyk A. Large-conductance Ca²⁺-activated potassium channel in mitochondria of endothelial EA.hy926 cells. Am J Physiol Heart Circ Physiol 2013; 304:H1415-27. [PMID: 23542921 DOI: 10.1152/ajpheart.00976.2012] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In the present study, we describe the existence of a large-conductance Ca²⁺-activated potassium (BKCa) channel in the mitochondria of the human endothelial cell line EA.hy926. A single-channel current was recorded from endothelial mitoplasts (i.e., inner mitochondrial membrane) using the patch-clamp technique in the mitoplast-attached mode. A potassium-selective current was recorded with a mean conductance equal to 270 ± 10 pS in a symmetrical 150/150 mM KCl isotonic solution. The channel activity, which was determined as the open probability, increased with the addition of calcium ions and the potassium channel opener NS1619. Conversely, the activity of the channel was irreversibly blocked by paxilline and iberiotoxin, BKCa channel inhibitors. The open-state probability was found to be voltage dependent. The substances known to modulate BKCa channel activity influenced the bioenergetics of mitochondria isolated from human endothelial EA.hy926 cells. In isolated mitochondria, 100 μM Ca²⁺, 10 μM NS1619, and 0.5 μM NS11021 depolarized the mitochondrial membrane potential and stimulated nonphosphorylating respiration. These effects were blocked by iberiotoxin and paxilline in a potassium-dependent manner. Under phosphorylating conditions, NS1619-induced, iberiotoxin-sensitive uncoupling diverted energy from ATP synthesis during the phosphorylating respiration of the endothelial mitochondria. Immunological analysis with antibodies raised against proteins of the plasma membrane BKCa channel identified a pore-forming α-subunit and an auxiliary β₂-subunit of the channel in the endothelial mitochondrial inner membrane. In conclusion, we show for the first time that the inner mitochondrial membrane in human endothelial EA.hy926 cells contains a large-conductance calcium-dependent potassium channel with properties similar to those of the surface membrane BKCa channel.
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Affiliation(s)
- Piotr Bednarczyk
- Department of Biophysics, Warsaw University of Life Sciences, Warsaw, Poland
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28
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The mitochondrial permeability transition pore (PTP) — An example of multiple molecular exaptation? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:2072-86. [DOI: 10.1016/j.bbabio.2012.06.620] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 06/19/2012] [Accepted: 06/21/2012] [Indexed: 11/21/2022]
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29
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Trono D, Soccio M, Laus MN, Pastore D. Potassium channel-oxidative phosphorylation relationship in durum wheat mitochondria from control and hyperosmotic-stressed seedlings. PLANT, CELL & ENVIRONMENT 2011; 34:2093-108. [PMID: 21819416 DOI: 10.1111/j.1365-3040.2011.02407.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Durum wheat mitochondria (DWM) possess an ATP-inhibited K(+) channel, the plant mitoK(ATP) (PmitoK(ATP) ), which is activated under environmental stress to control mitochondrial ROS production. To do this, PmitoK(ATP) collapses membrane potential (ΔΨ), thus suggesting mitochondrial uncoupling. We tested this point by studying oxidative phosphorylation (OXPHOS) in DWM purified from control seedlings and from seedlings subjected both to severe mannitol and NaCl stress. In severely-stressed DWM, the ATP synthesis via OXPHOS, continuously monitored by a spectrophotometric assay, was about 90% inhibited when the PmitoK(ATP) was activated by KCl. Contrarily, in control DWM, although PmitoK(ATP) collapsed ΔΨ, ATP synthesis, as well as coupling [respiratory control (RC) ratio and ratio between phosphorylated ADP and reduced oxygen (ADP/O)] checked by oxygen uptake experiments, were unaffected. We suggest that PmitoK(ATP) may play an important defensive role at the onset of the environmental/oxidative stress by preserving energy in a crucial moment for cell and mitochondrial bioenergetics. Consistently, under moderate mannitol stress, miming an early stress condition, the channel may efficiently control reactive oxygen species (ROS) generation (about 35-fold from fully open to closed state) without impairing ATP synthesis. Anyway, if the stress significantly proceeds, the PmitoK(ATP) becomes fully activated by decrease of ATP concentration (25-40%) and increase of activators [free fatty acids (FFAs) and superoxide anion], thus impairing ATP synthesis.
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Affiliation(s)
- Daniela Trono
- CRA - Centro di Ricerca per la Cerealicoltura, S.S. 16 Km 675, Dipartimento di Scienze Agroambientali, Chimica e Difesa Vegetale, Università di Foggia, Via Napoli 25, Italy
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30
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Szabò I, Leanza L, Gulbins E, Zoratti M. Physiology of potassium channels in the inner membrane of mitochondria. Pflugers Arch 2011; 463:231-46. [PMID: 22089812 DOI: 10.1007/s00424-011-1058-7] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Accepted: 10/30/2011] [Indexed: 02/06/2023]
Abstract
The inner membrane of the ATP-producing organelles of endosymbiotic origin, mitochondria, has long been considered to be poorly permeable to cations and anions, since the strict control of inner mitochondrial membrane permeability is crucial for efficient ATP synthesis. Over the past 30 years, however, it has become clear that various ion channels--along with antiporters and uniporters--are present in the mitochondrial inner membrane, although at rather low abundance. These channels are important for energy supply, and some are a decisive factor in determining whether a cell lives or dies. Their electrophysiological and pharmacological characterisations have contributed importantly to the ongoing elucidation of their pathophysiological roles. This review gives an overview of recent advances in our understanding of the functions of the mitochondrial potassium channels identified so far. Open issues concerning the possible molecular entities giving rise to the observed activities and channel protein targeting to mitochondria are also discussed.
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Affiliation(s)
- Ildikò Szabò
- Department of Biology, University of Padova, Padova, Italy.
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31
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Wieloch W, Boguś MI, Ligęza M, Koszela-Piotrowska I, Szewczyk A. Coronatin-1 isolated from entomopathogenic fungus Conidiobolus coronatus kills Galleria mellonella hemocytes in vitro and forms potassium channels in planar lipid membrane. Toxicon 2011; 58:369-79. [PMID: 21798278 DOI: 10.1016/j.toxicon.2011.07.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Revised: 07/05/2011] [Accepted: 07/12/2011] [Indexed: 10/17/2022]
Abstract
Entomopathogenic fungi are important natural regulatory factors of insect populations and have potential as biological control agents of insect pests. The cosmopolitan soil fungus Conidiobolus coronatus (Entomopthorales) easily attacks Galleria mellonella (Lepidoptera) larvae. Prompt death of invaded insects is attributed to the action of toxic metabolites released by the invader. Effect of fungal metabolites on hemocytes, insect blood cells involved in innate defense response, remains underexplored to date. C. coronatus isolate 3491 inducing 100% mortality of G. mellonella last instar larvae exposed to sporulating colonies, was cultivated at 20 °C in minimal medium. Post-incubation filtrates were used as a source of fungal metabolites. A two-step HPLC (1 step: Shodex KW-803 column eluted with 50 mM KH(2)PO(4) supplemented with 0.1 M KCl, pH 6.5; 2 step: ProteinPak™ CM 8HR column equilibrated with 5 mM KH(2)PO(4), pH 6.5, proteins eluted with a linear gradient of 0.5 M KCl) allowed the isolation of coronatin-1, an insecticidal 36 kDa protein showing both elastolytic and chitinolytic activities. Addition of coronatin-1 into primary in vitro cultures of G. mellonella hemocytes resulted in rapid disintegration of spherulocytes freely floating in culture medium and shrinkage of plasmatocytes adhering to the bottom of culture well. Coronatin-1 stimulated pseudopodia atrophy and, in consequence, disintegration of nets formed by cultured hemocytes. After incorporation of coronatin-1 into planar lipid membrane (PLM) ion channels selective for K(+) ions in 50/450 mM KCl solutions were observed. Potassium current flows were recorded in nearly 70% of experiments with conductance from 300 pS up to 1 nS. All observed channels were active at both positive and negative membrane potentials. Under experimental conditions incorporated coronatin-1 exhibited a zero current potential (E(rev)) of 47.7 mV, which indicates K(+)-selectivity of this protein. The success of the purification of coronatin-1 will allow further characterization of the mode of action of this molecule, including ability of coronatin-1 to form potassium channels in immunocompetent hemocytes.
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Affiliation(s)
- Wioletta Wieloch
- Institute of Parasitology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa, Poland
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Matkovic K, Koszela-Piotrowska I, Jarmuszkiewicz W, Szewczyk A. Ion conductance pathways in potato tuber (Solanum tuberosum) inner mitochondrial membrane. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:275-85. [DOI: 10.1016/j.bbabio.2010.12.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 11/24/2010] [Accepted: 12/04/2010] [Indexed: 11/28/2022]
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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] [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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De Santis A, Frascaroli E, Baraldi E, Carnevali F, Landi P. The activity of the plant mitochondrial inner membrane anion channel (PIMAC) of maize populations divergently selected for cold tolerance level is differentially dependent on the growth temperature of seedlings. PLANT & CELL PHYSIOLOGY 2011; 52:193-204. [PMID: 21148151 DOI: 10.1093/pcp/pcq189] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The activity of the plant inner membrane mitochondrial anion channel (PIMAC) is involved in metabolite shuttles and mitochondrial volume changes and could have a role in plant temperature tolerance. Our objectives were to investigate (i) the occurrence and (ii) the temperature dependence of anion fluxes through PIMAC in mitochondria isolated from seedlings of three maize populations differing in terms of cold tolerance; and (iii) the relationships between the PIMAC activity kinetics and the level of cold tolerance. Populations were the source population (C0) and two populations divergently selected for high (C4H) and low (C4L) cold tolerance. Such divergently selected populations are expected to share most of their genes, with the main exception of those genes controlling cold tolerance. Arrhenius plots of PIMAC chloride fluxes showed a linear temperature dependence when seedlings were grown at 25 or 14°C, whereas a non-linear temperature dependence was found when seedlings were grown at 5°C, with or without acclimation at 14°C. The activation energy and other thermodynamic parameters of PIMAC activity varied depending on temperature treatments during seedling growth. When seedlings were grown at 14 and 5°C with acclimation, PIMAC activity of the C4H population increased, while that of C4L declined, as compared with the activities of seedlings grown at 25°C. These symmetric responses indicate that PIMAC activity changes are associated with genetically determined differences in the cold tolerance level of the investigated populations. We conclude that anion fluxes by PIMAC depend upon changes on growth temperature and are differentially related to the tolerance level of the tested populations.
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Affiliation(s)
- Aurelio De Santis
- Dipartimento di Scienze del Mare, Università Politecnica delle Marche, Ancona, Italy.
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Laus MN, Soccio M, Trono D, Liberatore MT, Pastore D. Activation of the plant mitochondrial potassium channel by free fatty acids and acyl-CoA esters: a possible defence mechanism in the response to hyperosmotic stress. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:141-54. [PMID: 20801915 DOI: 10.1093/jxb/erq256] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The effect of free fatty acids (FFAs) and acyl-CoA esters on K(+) uptake was studied in mitochondria isolated from durum wheat (Triticum durum Desf.), a species that has adapted well to the semi-arid Mediterranean area and possessing a highly active mitochondrial ATP-sensitive K(+) channel (PmitoK(ATP)), that may confer resistance to environmental stresses. This was made by swelling experiments in KCl solution under experimental conditions in which PmitoK(ATP) activity was monitored. Linoleate and other FFAs (laurate, palmitate, stearate, palmitoleate, oleate, arachidonate, and the non-physiological 1-undecanesulphonate and 5-phenylvalerate), used at a concentration (10 μM) unable to damage membranes of isolated mitochondria, stimulated K(+) uptake by about 2-4-fold. Acyl-CoAs also promoted K(+) transport to a much larger extent with respect to FFAs (about 5-12-fold). In a different experimental system based on safranin O fluorescence measurements, the dissipation of electrical membrane potential induced by K(+) uptake via PmitoK(ATP) was found to increase in the presence of 5-phenylvalerate and palmitoyl-CoA, both unable to elicit the activity of the Plant Uncoupling Protein. This result suggests a direct activation of PmitoK(ATP). Stimulation of K(+) transport by FFAs/acyl-CoAs resulted in a widespread phenomenon in plant mitochondria from different mono/dicotyledonous species (bread wheat, barley, triticale, maize, lentil, pea, and topinambur) and from different organs (root, tuber, leaf, and shoot). Finally, an increase in mitochondrial FFAs up to a content of 50 nmol mg(-1) protein, which was able to activate PmitoK(ATP) strongly, was observed under hyperosmotic stress conditions. Since PmitoK(ATP) may act against environmental/oxidative stress, its activation by FFAs/acyl-CoAs is proposed to represent a physiological defence mechanism.
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Affiliation(s)
- Maura N Laus
- Dipartimento di Scienze Agro-ambientali, Chimica e Difesa Vegetale, Facoltà di Agraria, Università degli Studi di Foggia, Via Napoli, 25-71122 Foggia, Italy
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Szewczyk A, Kajma A, Malinska D, Wrzosek A, Bednarczyk P, Zabłocka B, Dołowy K. Pharmacology of mitochondrial potassium channels: dark side of the field. FEBS Lett 2010; 584:2063-9. [PMID: 20178786 DOI: 10.1016/j.febslet.2010.02.048] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 01/25/2010] [Accepted: 02/15/2010] [Indexed: 11/25/2022]
Abstract
Mitochondrial potassium channels play an important role in cytoprotection. Potassium channels in the inner mitochondrial membrane are modulated by inhibitors and activators (potassium channel openers) previously described for plasma membrane potassium channels. The majority of mitochondrial potassium channel modulators exhibit a broad spectrum of off-target effects. These include uncoupling properties, inhibition of the respiratory chain and effects on cellular calcium homeostasis. Therefore, the rational application of channel inhibitors or activators is crucial to understanding the cellular consequences of mitochondrial channel inhibition or activation. Moreover, understanding their side-effects should facilitate the design of a specific mitochondrial channel opener with cytoprotective properties. In this review, we discuss the complex interactions of potassium channel inhibitors and activators with cellular structures.
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Affiliation(s)
- Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland.
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Jarmuszkiewicz W, Matkovic K, Koszela-Piotrowska I. Potassium channels in the mitochondria of unicellular eukaryotes and plants. FEBS Lett 2010; 584:2057-62. [PMID: 20083113 DOI: 10.1016/j.febslet.2010.01.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 01/05/2010] [Accepted: 01/12/2010] [Indexed: 10/20/2022]
Abstract
The functional characterisation of potassium channels found in the mitochondria of plants and unicellular eukaryotes is critically discussed herein, with a focus on the ATP-sensitive potassium channel and the large-conductance Ca(2+)-activated potassium channel (mitoBK(Ca) channel). The physiological functions of these channels are not completely understood. We discuss the functional connections and roles of potassium channels, uncoupling protein and alternative oxidase, three energy-dissipating systems that exist in the mitochondrial respiratory chain of plants and some unicellular eukaryotes, which include preventing the production of reactive oxygen species.
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Affiliation(s)
- Wieslawa Jarmuszkiewicz
- Laboratory of Bioenergetics, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland.
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An investigation of the occurrence and properties of the mitochondrial intermediate-conductance Ca2+-activated K+ channel mtKCa3.1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1797:1260-7. [PMID: 20036632 DOI: 10.1016/j.bbabio.2009.12.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Revised: 12/15/2009] [Accepted: 12/19/2009] [Indexed: 12/24/2022]
Abstract
The mitochondrial intermediate-conductance Ca2+-activated K+ channel mtKCa3.1 has recently been discovered in the HCT116 colon tumor-derived cell line, which expresses relatively high levels of this protein also in the plasma membrane. Electrophysiological recordings revealed that the channel can exhibit different conductance states and kinetic modes, which we tentatively ascribe to post-translational modifications. To verify whether the localization of this channel in mitochondria might be a peculiarity of these cells or a more widespread feature we have checked for the presence of mtKCa3.1 in a few other cell lines using biochemical and electrophysiological approaches. It turned out to be present at least in some of the cells investigated. Functional assays explored the possibility that mtKCa3.1 might be involved in cell proliferation or play a role similar to that of the Shaker-type KV1.3 channel in lymphocytes, which interacts with outer mitochondrial membrane-inserted Bax thereby promoting apoptosis (Szabò, I. et al., Proc. Natl. Acad Sci. USA 105 (2008) 14861-14866). A specific KCa3.1 inhibitor however did not have any detectable effect on cell proliferation or death.
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