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Malaiyandi LM, Sharthiya H, Barakat AN, Edwards JR, Dineley KE. Using FluoZin-3 and fura-2 to monitor acute accumulation of free intracellular Cd 2+ in a pancreatic beta cell line. Biometals 2019; 32:951-964. [PMID: 31754889 PMCID: PMC7446769 DOI: 10.1007/s10534-019-00226-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 11/08/2019] [Indexed: 11/28/2022]
Abstract
The understanding of cellular Cd2+ accumulation and toxicity is hampered by a lack of fluorescent indicators selective for intracellular free Cd2+ ([Cd2+]i). In this study, we used depolarized MIN6 mouse pancreatic beta cells as a model for evaluating [Cd2+]i detection with commercially available fluorescent probes, most of which have been traditionally used to visualize [Ca2+]i and [Zn2+]i. We trialed a panel of 12 probes including fura-2, FluoZin-3, Leadmium Green, Rhod-5N, indo-1, Fluo-5N, and others. We found that the [Zn2+]i probe FluoZin-3 and the traditional [Ca2+]i probe fura-2 responded most consistently and robustly to [Cd2+]i accumulation mediated by voltage-gated calcium channels. While selective detection of [Cd2+]i by fura-2 required the omission of Ca2+ from extracellular buffers, FluoZin-3 responded to [Cd2+]i similarly in the presence or absence of extracellular Ca2+. Furthermore, we showed that FluoZin-3 and fura-2 can be used together for simultaneous monitoring of [Ca2+]i and [Cd2+]i in the same cells. None of the other fluorophores tested were effective [Cd2+]i detectors in this model.
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Affiliation(s)
- Latha M Malaiyandi
- Departments of Anatomy, College of Graduate Studies, Midwestern University, Downers Grove, IL, 60515, USA
| | - Harsh Sharthiya
- Departments of Anatomy, College of Graduate Studies, Midwestern University, Downers Grove, IL, 60515, USA
- AbbVie Inc., Headquarters 1 N. Waukegan Road, North Chicago, IL, 60064, USA
| | - Ameir N Barakat
- Departments of Anatomy, College of Graduate Studies, Midwestern University, Downers Grove, IL, 60515, USA
| | - Joshua R Edwards
- Departments of Pharmacology, College of Graduate Studies, Midwestern University, 555 31st Street, Downers Grove, IL, 60515, USA
| | - Kirk E Dineley
- Departments of Pharmacology, College of Graduate Studies, Midwestern University, 555 31st Street, Downers Grove, IL, 60515, USA.
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2
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Marszałek I, Goch W, Bal W. Ternary Zn(II) Complexes of Fluorescent Zinc Probes Zinpyr-1 and Zinbo-5 with the Low Molecular Weight Component of Exchangeable Cellular Zinc Pool. Inorg Chem 2019; 58:14741-14751. [PMID: 31646867 DOI: 10.1021/acs.inorgchem.9b02419] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The intracellular exchangeable Zn(II) is usually measured with synthetic fluorescent zinc sensors. 4',5'-Bis[bis(2-pyridylmethyl)aminomethyl]-2',7'-dichlorofluorescein (Zinpyr-1) is a sensor containing the fluorescein platform and a duplicated chelating unit. Its advantages include brightness and a relatively high affinity for Zn(II), Kd = 0.7 nM. 2-(4,5-Dimethoxy-2-hydroxyphenyl)-4-(2-pyridylmethyl)aminomethylbenzoxazole (Zinbo-5) is a member of a growing family of ratiometric synthetic Zn(II) probes, offering a possibility to determine Zn(II) concentration independently of the sensor concentration. Cells, however, contain high, millimolar or nearly millimolar concentrations of low molecular weight ligands (LMWLs) capable of binding Zn(II) ions. Previously, we demonstrated that such LMWLs can perturb the performance of some fluorescent zinc sensors by competition and formation of ternary Zn(sensor) (LMWL) complexes. Here we tested Zinpyr-1 and Zinbo-5 in this respect. Despite structural differences, both sensors formed such ternary complexes. We determined their stability constants CKtern and performed numerical simulations of Zn(II) distributions at physiological concentrations of selected LMWLs. Glutamic acid was found to provide the strongest ternary complexes with either of the studied sensors. Zn(Zinpyr-1)(Glu) was an absolutely dominant Zn(II)/Zinpyr-1 species (more than 96% of the exchangeable Zn(II)), and Zn(Zinbo-5)(Glu) was the most abundant one (more than 40%) in these simulations. Our results indicate that under cellular conditions these sensors are able to report Zn(II) complexed to LMWLs rather than free Zn2+ ions. On the other hand, the specific affinity of Zn(Zinpyr-1) and Zn(Zinbo-5) for Glu creates interesting opportunities for determining glutamic acid in biological samples.
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Affiliation(s)
- Ilona Marszałek
- Institute of Biochemistry and Biophysics , Polish Academy of Sciences , Pawińskiego 5a , 02-106 Warsaw , Poland
| | - Wojciech Goch
- Institute of Biochemistry and Biophysics , Polish Academy of Sciences , Pawińskiego 5a , 02-106 Warsaw , Poland.,Faculty of Pharmacy , Medical University of Warsaw , Banacha 1 , 02-091 Warsaw , Poland
| | - Wojciech Bal
- Institute of Biochemistry and Biophysics , Polish Academy of Sciences , Pawińskiego 5a , 02-106 Warsaw , Poland
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Marszałek I, Goch W, Bal W. Ternary Zn(II) Complexes of FluoZin-3 and the Low Molecular Weight Component of the Exchangeable Cellular Zinc Pool. Inorg Chem 2018; 57:9826-9838. [PMID: 30088924 DOI: 10.1021/acs.inorgchem.8b00489] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Knowledge of the nature of exchangeable (labile) intracellular Zn(II) is increasingly important for biomedical research. The detection and quantitative determination of Zn(II) ions is usually performed by using Zn(II)-specific fluorescent sensors, among which 2-[2-[2-[2-[bis(carboxylatomethyl)amino]-5-methoxyphenoxy]ethoxy]-4-(2,7-difluoro-3-oxido-6-oxo-4a,9a-dihydroxanthen-9-yl)anilino]acetate (FluoZin-3) has been used most widely. Selectivity of this sensor for Zn(II) over other divalent cations was demonstrated, but possible interference in its performance by other compounds has not been investigated. Many potential low molecular weight ligands for Zn(II) ions (LMWLs) are abundant in the cell. In this study we demonstrate that FluoZin-3 is susceptible to competition for Zn(II) from LMWLs and also forms strong ternary complexes with some of them. We determined the set of conditional stability constants C Ktern for ternary Zn(FluoZin-3)(LMWL) complexes using fluorescence titrations and applied it to model the response of exchangeable zinc to FluoZin-3. We found that competition and formation of ternary complexes with LMWLs together strongly affect (net reduce) the Zn(FluoZin-3) fluorescence. This effect may cause a significant underestimation of exchangeable Zn(II). We also demonstrated a strong pH dependence of this effect. Reduced glutathione (GSH) emerged as the most important Zn(II) partner among the LMWLs, characterized with Ktern = 2.8 ± 0.2 × 106 M-1. Our experiments and calculations suggest that Zn(LMWL) complexes contribute to the exchangeable cellular zinc pool.
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Affiliation(s)
- Ilona Marszałek
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences , Pawińskiego 5a , 02-106 Warsaw , Poland
| | - Wojciech Goch
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences , Pawińskiego 5a , 02-106 Warsaw , Poland.,Faculty of Pharmacy , Medical University of Warsaw , Banacha 1 , 02-091 Warsaw , Poland
| | - Wojciech Bal
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences , Pawińskiego 5a , 02-106 Warsaw , Poland
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Marszałek I, Krężel A, Goch W, Zhukov I, Paczkowska I, Bal W. Revised stability constant, spectroscopic properties and binding mode of Zn(II) to FluoZin-3, the most common zinc probe in life sciences. J Inorg Biochem 2016; 161:107-14. [PMID: 27216451 DOI: 10.1016/j.jinorgbio.2016.05.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 05/04/2016] [Accepted: 05/13/2016] [Indexed: 01/01/2023]
Abstract
2-[2-[2-[2-[bis(carboxylatomethyl)amino]-5-methoxyphenoxy]ethoxy]-4-(2,7-difluoro-3-oxido-6-oxo-4a,9a-dihydroxanthen-9-yl)anilino]acetate (FluoZin-3) is used very broadly in life sciences as intra- and extracellular Zn(II) sensor selective for Zn(II) over Co(II), Ca(II) and Mg(II) ions at their physiological concentrations. It has been used for determination of relative and absolute levels of exchangeable Zn(II) in cells and extracellular fluids. Despite its popularity, the knowledge of its acid/base and Zn(II) coordination abilities and of its spectroscopic properties remained very limited. Also the published conditional dissociation constant ((C)Kd) values at pH7.4 are slightly discrepant, (15nM or 8.9nM). In this work we determined the (C)Kd for Zn(II) complexation by FluoZin-3 at pH7.4 with nitrilotriacetic acid (NTA) as competitor using two independent methods: fluorimetry and UV-Vis spectroscopy. For the first time, we investigated FluoZin-3 alone and complexed with Zn(II) in the wide range of pH, determining the total of eight pKa values from fluorescence spectra and from various regions of UV-Vis spectra. The validated values of (C)Kd (9.1±0.4nM; -log (C)Kd=8.04) and of the absolute (pH-independent) stability constant log βZnL (8.16±0.05) were provided by fluorescence spectroscopy experiments performed at 1μM concentrations. Our experiments demonstrated that both of aminocarboxylate moieties of FluoZin-3 bind the Zn(II) ion synergistically.
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Affiliation(s)
- I Marszałek
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - A Krężel
- Laboratory of Chemical Biology, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - W Goch
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - I Zhukov
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland; NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
| | - I Paczkowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - W Bal
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland.
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Kochańczyk T, Drozd A, Krężel A. Relationship between the architecture of zinc coordination and zinc binding affinity in proteins – insights into zinc regulation. Metallomics 2015; 7:244-57. [DOI: 10.1039/c4mt00094c] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Relationship between the architecture and stability of zinc proteins.
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Affiliation(s)
- Tomasz Kochańczyk
- Laboratory of Chemical Biology
- Faculty of Biotechnology
- University of Wrocław
- 50-383 Wrocław, Poland
| | - Agnieszka Drozd
- Laboratory of Chemical Biology
- Faculty of Biotechnology
- University of Wrocław
- 50-383 Wrocław, Poland
| | - Artur Krężel
- Laboratory of Chemical Biology
- Faculty of Biotechnology
- University of Wrocław
- 50-383 Wrocław, Poland
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Radford RJ, Chyan W, Lippard SJ. Peptide Targeting of Fluorescein-Based Sensors to Discrete Intracellular Locales. Chem Sci 2014; 5:4512-4516. [PMID: 25512838 PMCID: PMC4264632 DOI: 10.1039/c4sc01280a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Fluorescein-based sensors are the most widely applied class of zinc probes but display adventitious localization in live cells. We present here a peptide-based localization strategy that affords precision in targeting of fluorescein-based zinc sensors. By appending the zinc-selective, reaction-based probe Zinpyr-1 diacetate (DA-ZP1) to the N-terminus of two different targeting peptides we achieve programmable localization and avoid unwanted sequestration within acidic vesicles. Furthermore, this approach can be generalized to other fluorescein-based sensors. When appended to a mitochondrial targeting peptide, the esterase-activated profluorophore 2',7'-dichlorofluorescein diacetate can be used effectively at concentrations four-times lower than previously reported for analogous, non-acetylated derivatives. These results demonstrate on-resin or in-solution esterification of fluorescein to be an effective strategy to facilitate peptide-based targeting in live cells.
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Nydegger I, Rumschik SM, Zhao J, Kay AR. Evidence for an extracellular zinc-veneer in rodent brains from experiments with Zn-ionophores and ZnT3 knockouts. ACS Chem Neurosci 2012; 3:761-6. [PMID: 23077720 DOI: 10.1021/cn300061z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 07/02/2012] [Indexed: 01/03/2023] Open
Abstract
Ionic zinc is found at a high concentration in some glutamatergic vesicles of the mammalian brain. Ionic zinc is also found chelated to macromolecules in the extracellular space, constituting what has been called the "zinc veneer". In this communication we show that the zinc ionophore, pyrithione, can be used to demonstrate the presence of the veneer. Application of pyrithione without added ionic zinc to rodent hippocampal slices mobilizes extracellular zinc, which can be detected intracellularly by the zinc probe FluoZin-3. In addition, we show that ZnT3 null mice, which lack the transporter responsible for stocking synaptic vesicles, nevertheless do have a zinc veneer, albeit diminished compared to wild type animals. The presence of the zinc veneer in ZnT3 null mice may account for the absence of any marked deficit in these animals.
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Affiliation(s)
- Irma Nydegger
- Departments
of Biology and ‡Chemistry, 336 BB, University of Iowa, Iowa City, Iowa 52242, United States
| | - Sean M. Rumschik
- Departments
of Biology and ‡Chemistry, 336 BB, University of Iowa, Iowa City, Iowa 52242, United States
| | - Jinfu Zhao
- Departments
of Biology and ‡Chemistry, 336 BB, University of Iowa, Iowa City, Iowa 52242, United States
| | - Alan R. Kay
- Departments
of Biology and ‡Chemistry, 336 BB, University of Iowa, Iowa City, Iowa 52242, United States
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Hyman LM, Franz KJ. Probing oxidative stress: Small molecule fluorescent sensors of metal ions, reactive oxygen species, and thiols. Coord Chem Rev 2012; 256:2333-2356. [PMID: 23440254 PMCID: PMC3579673 DOI: 10.1016/j.ccr.2012.03.009] [Citation(s) in RCA: 231] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Oxidative stress is a common feature shared by many diseases, including neurodegenerative diseases. Factors that contribute to cellular oxidative stress include elevated levels of reactive oxygen species, diminished availability of detoxifying thiols, and the misregulation of metal ions (both redox-active iron and copper as well as non-redox active calcium and zinc). Deciphering how each of these components interacts to contribute to oxidative stress presents an interesting challenge. Fluorescent sensors can be powerful tools for detecting specific analytes within a complicated cellular environment. Reviewed here are several classes of small molecule fluorescent sensors designed to detect several molecular participants of oxidative stress. We focus our review on describing the design, function and application of probes to detect metal cations, reactive oxygen species, and intracellular thiol-containing compounds. In addition, we highlight the intricacies and complications that are often faced in sensor design and implementation.
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Affiliation(s)
- Lynne M. Hyman
- Department of Chemistry, Duke University, Durham, NC 27708, USA
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