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Minckley TF, Salvagio LA, Fudge DH, Verhey K, Markus SM, Qin Y. Zn2+ decoration of microtubules arrests axonal transport and displaces tau, doublecortin, and MAP2C. J Cell Biol 2023; 222:e202208121. [PMID: 37326602 PMCID: PMC10276529 DOI: 10.1083/jcb.202208121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 03/31/2023] [Accepted: 05/11/2023] [Indexed: 06/17/2023] Open
Abstract
Intracellular Zn2+ concentrations increase via depolarization-mediated influx or intracellular release, but the immediate effects of Zn2+ signals on neuron function are not fully understood. By simultaneous recording of cytosolic Zn2+ and organelle motility, we find that elevated Zn2+ (IC50 ≈ 5-10 nM) reduces both lysosomal and mitochondrial motility in primary rat hippocampal neurons and HeLa cells. Using live-cell confocal microscopy and in vitro single-molecule TIRF imaging, we reveal that Zn2+ inhibits activity of motor proteins (kinesin and dynein) without disrupting their microtubule binding. Instead, Zn2+ directly binds to microtubules and selectively promotes detachment of tau, DCX, and MAP2C, but not MAP1B, MAP4, MAP7, MAP9, or p150glued. Bioinformatic predictions and structural modeling show that the Zn2+ binding sites on microtubules partially overlap with the microtubule binding sites of tau, DCX, dynein, and kinesin. Our results reveal that intraneuronal Zn2+ regulates axonal transport and microtubule-based processes by interacting with microtubules.
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Affiliation(s)
- Taylor F. Minckley
- Department of Biological Sciences, University of Denver, Denver, CO, USA
| | | | - Dylan H. Fudge
- Department of Biological Sciences, University of Denver, Denver, CO, USA
| | - Kristen Verhey
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Steven M. Markus
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| | - Yan Qin
- Department of Biological Sciences, University of Denver, Denver, CO, USA
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2
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Menzikov SA, Zaichenko DM, Moskovtsev AA, Morozov SG, Kubatiev AA. Zinc Inhibits the GABA AR/ATPase during Postnatal Rat Development: The Role of Cysteine Residue. Int J Mol Sci 2023; 24:ijms24032764. [PMID: 36769085 PMCID: PMC9917249 DOI: 10.3390/ijms24032764] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 01/24/2023] [Accepted: 01/26/2023] [Indexed: 02/04/2023] Open
Abstract
Zinc ions (Zn2+) are concentrated in various brain regions and can act as a neuromodulator, targeting a wide spectrum of postsynaptic receptors and enzymes. Zn2+ inhibits the GABAARs, and its potency is profoundly affected by the subunit composition and neuronal developmental stage. Although the extracellular amino acid residues of the receptor's hetero-oligomeric structure are preferred for Zn2+ binding, there are intracellular sites that, in principle, could coordinate its potency. However, their role in modulating the receptor function during postembryonic development remains unclear. The GABAAR possesses an intracellular ATPase that enables the energy-dependent anion transport via a pore. Here, we propose a mechanistic and molecular basis for the inhibition of intracellular GABAAR/ATPase function by Zn2+ in neonatal and adult rats. The enzymes within the scope of GABAAR performance as Cl-ATPase and then as Cl-, HCO3-ATPase form during the first week of postnatal rat development. In addition, we have shown that the Cl-ATPase form belongs to the β1 subunit, whereas the β3 subunit preferably possesses the Cl-, HCO3-ATPase activity. We demonstrated that a Zn2+ with variable efficacy inhibits the GABAAR as well as the ATPase activities of immature or mature neurons. Using fluorescence recording in the cortical synaptoneurosomes (SNs), we showed a competitive association between Zn2+ and NEM in parallel changes both in the ATPase activity and the GABAAR-mediated Cl- and HCO3- fluxes. Finally, by site-directed mutagenesis, we identified in the M3 domain of β subunits the cysteine residue (C313) that is essential for the manifestation of Zn2+ potency.
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Abstract
Zinc is an essential trace element that stabilizes protein structures and allosterically modulates a plethora of enzymes, ion channels and neurotransmitter receptors. Labile zinc (Zn2+) acts as an intracellular and intercellular signalling molecule in response to various stimuli, which is especially important in the central nervous system. Zincergic neurons, characterized by Zn2+ deposits in synaptic vesicles and presynaptic Zn2+ release, are found in the cortex, hippocampus, amygdala, olfactory bulb and spinal cord. To provide an overview of synaptic Zn2+ and intracellular Zn2+ signalling in neurons, the present paper summarizes the fluorescent sensors used to detect Zn2+ signals, the cellular mechanisms regulating the generation and buffering of Zn2+ signals, as well as the current perspectives on their pleiotropic effects on phosphorylation signalling, synapse formation, synaptic plasticity, as well as sensory and cognitive function.
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Affiliation(s)
- Chen Zhang
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
| | - Anna Dischler
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
| | - Kaitlyn Glover
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
| | - Yan Qin
- Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
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4
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Abstract
Zn2+ ions are essential in many physiological processes, including enzyme catalysis, protein structural stabilization, and the regulation of many proteins. The affinities of proteins for Zn2+ ions span several orders of magnitude, with catalytic Zn2+ ions generally held more tightly than structural or regulatory ones. Metal carrier proteins, most of which are not specific for Zn2+, bind these ions with a broad range of affinities that overlap those of catalytic, structural, and regulatory Zn2+ ions and are thought to be responsible for distributing the metal through most cells, tissues, and fluid compartments. While little is known about how many proteins obtain or release these ions, there is now considerable experimental evidence suggesting that metal carrier proteins may be responsible for transferring metals to and from some Zn2+-dependent proteins, thus serving as a major regulatory factor for them. In this review, the biological roles of Zn2+ and structures of Zn2+ binding sites are examined, and experimental evidence demonstrating the direct participation of metal carrier proteins in enzyme regulation is discussed. Mechanisms of metal ion transfer are also offered, and the potential physiological significance of this phenomenon is explored.
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Abstract
The functions, purposes, and roles of metallothioneins have been the subject of speculations since the discovery of the protein over 60 years ago. This article guides through the history of investigations and resolves multiple contentions by providing new interpretations of the structure-stability-function relationship. It challenges the dogma that the biologically relevant structure of the mammalian proteins is only the one determined by X-ray diffraction and NMR spectroscopy. The terms metallothionein and thionein are ambiguous and insufficient to understand biological function. The proteins need to be seen in their biological context, which limits and defines the chemistry possible. They exist in multiple forms with different degrees of metalation and types of metal ions. The homoleptic thiolate coordination of mammalian metallothioneins is important for their molecular mechanism. It endows the proteins with redox activity and a specific pH dependence of their metal affinities. The proteins, therefore, also exist in different redox states of the sulfur donor ligands. Their coordination dynamics allows a vast conformational landscape for interactions with other proteins and ligands. Many fundamental signal transduction pathways regulate the expression of the dozen of human metallothionein genes. Recent advances in understanding the control of cellular zinc and copper homeostasis are the foundation for suggesting that mammalian metallothioneins provide a highly dynamic, regulated, and uniquely biological metal buffer to control the availability, fluctuations, and signaling transients of the most competitive Zn(II) and Cu(I) ions in cellular space and time.
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Affiliation(s)
- Artur Krężel
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Wrocław 50-383, Poland
| | - Wolfgang Maret
- Departments of Biochemistry and Nutritional Sciences, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London SE1 9NH, U.K
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Cuajungco MP, Ramirez MS, Tolmasky ME. Zinc: Multidimensional Effects on Living Organisms. Biomedicines 2021; 9:biomedicines9020208. [PMID: 33671781 PMCID: PMC7926802 DOI: 10.3390/biomedicines9020208] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 02/03/2021] [Accepted: 02/09/2021] [Indexed: 12/28/2022] Open
Abstract
Zinc is a redox-inert trace element that is second only to iron in abundance in biological systems. In cells, zinc is typically buffered and bound to metalloproteins, but it may also exist in a labile or chelatable (free ion) form. Zinc plays a critical role in prokaryotes and eukaryotes, ranging from structural to catalytic to replication to demise. This review discusses the influential properties of zinc on various mechanisms of bacterial proliferation and synergistic action as an antimicrobial element. We also touch upon the significance of zinc among eukaryotic cells and how it may modulate their survival and death through its inhibitory or modulatory effect on certain receptors, enzymes, and signaling proteins. A brief discussion on zinc chelators is also presented, and chelating agents may be used with or against zinc to affect therapeutics against human diseases. Overall, the multidimensional effects of zinc in cells attest to the growing number of scientific research that reveal the consequential prominence of this remarkable transition metal in human health and disease.
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Abstract
Zinc(II) ions are redox-inert in biology. Yet, their interaction with sulfur of cysteine in cellular proteins can confer ligand-centered redox activity on zinc coordination sites, control protein functions, and generate signalling zinc ions as potent effectors of many cellular processes. The specificity and relative high affinity of binding sites for zinc allow regulation in redox biology, free radical biology, and the biology of reactive species. Understanding the role of zinc in these areas of biology requires an understanding of how cellular Zn2+ is homeostatically controlled and can serve as a regulatory ion in addition to Ca2+, albeit at much lower concentrations. A rather complex system of dozens of transporters and metallothioneins buffer the relatively high (hundreds of micromolar) total cellular zinc concentrations in such a way that the available zinc ion concentrations are only picomolar but can fluctuate in signalling. The proteins targeted by Zn2+ transients include enzymes controlling phosphorylation and redox signalling pathways. Networks of regulatory functions of zinc integrate gene expression and metabolic and signalling pathways at several hierarchical levels. They affect enzymatic catalysis, protein structure and protein-protein/biomolecular interactions and add to the already impressive number of catalytic and structural functions of zinc in an estimated three thousand human zinc proteins. The effects of zinc on redox biology have adduced evidence that zinc is an antioxidant. Without further qualifications, this notion is misleading and prevents a true understanding of the roles of zinc in biology. Its antioxidant-like effects are indirect and expressed only in certain conditions because a lack of zinc and too much zinc have pro-oxidant effects. Teasing apart these functions based on quantitative considerations of homeostatic control of cellular zinc is critical because opposite consequences are observed depending on the concentrations of zinc: pro- or anti-apoptotic, pro- or anti-inflammatory and cytoprotective or cytotoxic. The article provides a biochemical basis for the links between redox and zinc biology and discusses why zinc has pleiotropic functions. Perturbation of zinc metabolism is a consequence of conditions of redox stress. Zinc deficiency, either nutritional or conditioned, and cellular zinc overload cause oxidative stress. Thus, there is causation in the relationship between zinc metabolism and the many diseases associated with oxidative stress.
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Affiliation(s)
- Wolfgang Maret
- Metal Metabolism Group, Department of Nutritional Sciences, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK.
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Lawson R, Maret W, Hogstrand C. Prolonged stimulation of insulin release from MIN6 cells causes zinc depletion and loss of β-cell markers. J Trace Elem Med Biol 2018; 49:51-59. [PMID: 29895372 DOI: 10.1016/j.jtemb.2018.04.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 03/19/2018] [Accepted: 04/18/2018] [Indexed: 11/17/2022]
Abstract
Zinc is integral for the normal function of pancreatic β-cells in glycaemic control. Large amounts of zinc are secreted from β-cells following insulin exocytosis and regulated replenishment is required, which is thought to be mediated by the ZIP family of zinc importer proteins. Within Type 2 Diabetic patients, β-cells are stressed through prolonged stimulation by hyperglycaemia and this is thought to be a major factor contributing to loss of β-cell identity and mass. However, the consequences for the β-cell zinc status remain largely unexplored. We used inductively coupled plasma mass spectrometry (ICP-MS) to show that 24 h treatment of MIN6 cells with potassium chloride, mimicking hyperglycaemic stimulation, reduces the total cellular zinc content 2.8-fold, and qPCR to show an increase in mRNA expression for metallothioneins (Mt1 and Mt2) following 4 and 24 h of stimulation, suggestive of an early rise in cytosolic zinc. To determine which ZIP paralogues may be responsible for zinc replenishment, we used immunocytochemistry, Western blot and qPCR to demonstrate initial ZIP1 protein upregulation proceeded by downregulation of mRNA coding for ZIP1, ZIP6, ZIP7 and ZIP14. To assign a biological significance to the decreased total cellular zinc content, we assessed expression of key β-cell markers to show downregulation of mRNA for MafA, Mnx-1, Nkx2.2 and Pax6. Our data suggest hyperglycaemia-induced zinc depletion may contribute to loss of β-cell markers and promote β-cell dedifferentiation through disrupting expression of key transcription factors.
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Affiliation(s)
- Rebecca Lawson
- King's College London, Faculty of Life Sciences and Medicine, School of Life Course Sciences, Metal Metabolism Group, 150 Stamford St., London SE1 9NH, UK.
| | - Wolfgang Maret
- King's College London, Faculty of Life Sciences and Medicine, School of Life Course Sciences, Metal Metabolism Group, 150 Stamford St., London SE1 9NH, UK.
| | - Christer Hogstrand
- King's College London, Faculty of Life Sciences and Medicine, School of Life Course Sciences, Metal Metabolism Group, 150 Stamford St., London SE1 9NH, UK.
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9
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Abstract
In the last decade, we witnessed discoveries that established Zn2+ as a second major signalling metal ion in the transmission of information within cells and in communication between cells. Together with Ca2+ and Mg2+, Zn2+ covers biological regulation with redox-inert metal ions over many orders of magnitude in concentrations. The regulatory functions of zinc ions, together with their functions as a cofactor in about three thousand zinc metalloproteins, impact virtually all aspects of cell biology. This article attempts to define the regulatory functions of zinc ions, and focuses on the nature of zinc signals and zinc signalling in pathways where zinc ions are either extracellular stimuli or intracellular messengers. These pathways interact with Ca2+, redox, and phosphorylation signalling. The regulatory functions of zinc require a complex system of precise homeostatic control for transients, subcellular distribution and traffic, organellar homeostasis, and vesicular storage and exocytosis of zinc ions.
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Affiliation(s)
- Wolfgang Maret
- Metal Metabolism Group, Departments of Biochemistry and Nutritional Sciences, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, Franklin-Wilkins Bldg, 150 Stamford St., London SE1 9NH, UK.
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Bellomo E, Birla Singh K, Massarotti A, Hogstrand C, Maret W. The metal face of protein tyrosine phosphatase 1B. Coord Chem Rev 2016; 327-328:70-83. [PMID: 27890939 PMCID: PMC5115158 DOI: 10.1016/j.ccr.2016.07.002] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 07/01/2016] [Accepted: 07/01/2016] [Indexed: 01/12/2023]
Abstract
A new paradigm in metallobiochemistry describes the activation of inactive metalloenzymes by metal ion removal. Protein tyrosine phosphatases (PTPs) do not seem to require a metal ion for enzymatic activity. However, both metal cations and metal anions modulate their enzymatic activity. One binding site is the phosphate binding site at the catalytic cysteine residue. Oxyanions with structural similarity to phosphate, such as vanadate, inhibit the enzyme with nanomolar to micromolar affinities. In addition, zinc ions (Zn2+) inhibit with picomolar to nanomolar affinities. We mapped the cation binding site close to the anion binding site and established a specific mechanism of inhibition occurring only in the closed conformation of the enzyme when the catalytic cysteine is phosphorylated and the catalytic aspartate moves into the active site. We discuss this dual inhibition by anions and cations here for PTP1B, the most thoroughly investigated protein tyrosine phosphatase. The significance of the inhibition in phosphorylation signaling is becoming apparent only from the functions of PTP1B in the biological context of metal cations as cellular signaling ions. Zinc ion signals complement redox signals but provide a different type of control and longer lasting inhibition on a biological time scale owing to the specificity and affinity of zinc ions for coordination environments. Inhibitor design for PTP1B and other PTPs is a major area of research activity and interest owing to their prominent roles in metabolic regulation in health and disease, in particular cancer and diabetes. Our results explain the apparent dichotomy of both cations (Zn2+) and oxyanions such as vanadate inhibiting PTP1B and having insulin-enhancing ("anti-diabetic") effects and suggest different approaches, namely targeting PTPs in the cell by affecting their physiological modulators and considering a metallodrug approach that builds on the knowledge of the insulin-enhancing effects of both zinc and vanadium compounds.
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Affiliation(s)
- Elisa Bellomo
- Metal Metabolism Group, Division of Diabetes and Nutritional Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, UK
| | - Kshetrimayum Birla Singh
- Metal Metabolism Group, Division of Diabetes and Nutritional Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, UK
| | - Alberto Massarotti
- Dipartimento di Scienze del Farmaco, Università del Piemonte Orientale “A. Avogadro”, Novara, Italy
| | - Christer Hogstrand
- Metal Metabolism Group, Division of Diabetes and Nutritional Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, UK
| | - Wolfgang Maret
- Metal Metabolism Group, Division of Diabetes and Nutritional Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, UK
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11
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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12
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Okamoto A, Yamamuro M, Tatarazako N. Acute toxicity of 50 metals to Daphnia magna. J Appl Toxicol 2014; 35:824-30. [PMID: 25382633 DOI: 10.1002/jat.3078] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 09/07/2014] [Accepted: 09/07/2014] [Indexed: 11/09/2022]
Abstract
Metals are essential for human life and physiological functions but may sometimes cause disorders. Therefore, we conducted acute toxicity testing of 50 metals in Daphnia magna: EC50s of seven elements (Be, Cu, Ag, Cd, Os, Au and Hg) were < 100 µg l(-1) ; EC50s of 13 elements (Al, Sc, Cr, Co, Ni, Zn, Se, Rb, Y, Rh, Pt, Tl and Pb) were between 100 and 1000 µg l(-1) ; EC50s of 14 elements (Li, V, Mn, Fe, Ge, As, In, Sn, Sb, Te, Cs, Ba, W and Ir) were between 1,001 and 100,000 µg l(-1) ; EC50s of six elements (Na, Mg, K, Ca, Sr and Mo) were > 100,000 µg l(-1) ; and. 7 elements (Ti, Zr, Bi, Nb, Hf, Re and Ta) did not show EC50 at the upper limit of respective aqueous solubility, and EC50s were not obtained. Ga, Ru and Pd adhered to the body of D. magna and physically retarded the movement of D. magna. These metals formed hydroxides after adjusting the pH. Therefore, here, we distinguished this physical effect from the physiological toxic effect. The acute toxicity results of 40 elements obtained in this study were not correlated with electronegativity. Similarly, the acute toxicity results of metals including the rare metals were also not correlated with first ionization energy, atomic weight, atomic number, covalent radius, atomic radius or ionic radius.
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Affiliation(s)
- Akira Okamoto
- Graduate School of Frontier Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8561, Japan
| | - Masumi Yamamuro
- Graduate School of Frontier Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8561, Japan
| | - Norihisa Tatarazako
- Graduate School of Frontier Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8561, Japan.,Environmental Quality Measurement Section, Research Center for Environmental Risk, National Institute for Environmental Studies, 16-2 Ogawa, Tsukuba, Ibaraki, 305-8506, Japan
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13
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Cortese-Krott MM, Kulakov L, Opländer C, Kolb-Bachofen V, Kröncke KD, Suschek CV. Zinc regulates iNOS-derived nitric oxide formation in endothelial cells. Redox Biol 2014; 2:945-54. [PMID: 25180171 PMCID: PMC4143817 DOI: 10.1016/j.redox.2014.06.011] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 06/26/2014] [Indexed: 01/07/2023] Open
Abstract
Aberrant production of nitric oxide (NO) by inducible NO synthase (iNOS) has been implicated in the pathogenesis of endothelial dysfunction and vascular disease. Mechanisms responsible for the fine-tuning of iNOS activity in inflammation are still not fully understood. Zinc is an important structural element of NOS enzymes and is known to inhibit its catalytical activity. In this study we aimed to investigate the effects of zinc on iNOS activity and expression in endothelial cells. We found that zinc down-regulated the expression of iNOS (mRNA+protein) and decreased cytokine-mediated activation of the iNOS promoter. Zinc-mediated regulation of iNOS expression was due to inhibition of NF-κB transactivation activity, as determined by a decrease in both NF-κB-driven luciferase reporter activity and expression of NF-κB target genes, including cyclooxygenase 2 and IL-1β. However, zinc did not affect NF-κB translocation into the nucleus, as assessed by Western blot analysis of nuclear and cytoplasmic fractions. Taken together our results demonstrate that zinc limits iNOS-derived high output NO production in endothelial cells by inhibiting NF-κB-dependent iNOS expression, pointing to a role of zinc as a regulator of iNOS activity in inflammation. Zinc inhibits iNOS-dependent nitrite accumulation in endothelial cells. Zinc decreases cytokine-induced iNOS expression in endothelial cells. Zinc inhibits iNOS promoter activity. NF-kB silencing abolishes cytokine-induced iNOS expression. Zinc inhibits the transactivation activity of NF-κB.
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Affiliation(s)
- Miriam M Cortese-Krott
- Cardiovascular Research Laboratory, Department of Cardiology, Pneumology, and Angiology, Medical Faculty, Heinrich-Heine-University of Düsseldorf, Universitätsstr. 1, Düsseldorf D-40225, Germany ; Research Group Immunobiology, Medical Faculty, Heinrich-Heine-University of Düsseldorf, Universitätsstr. 1, Düsseldorf D-40225, Germany
| | - Larissa Kulakov
- Cardiovascular Research Laboratory, Department of Cardiology, Pneumology, and Angiology, Medical Faculty, Heinrich-Heine-University of Düsseldorf, Universitätsstr. 1, Düsseldorf D-40225, Germany ; Department of Trauma and Hand Surgery, Medical Faculty, Heinrich-Heine-University of Düsseldorf, Universitätsstr. 1, Düsseldorf D-40225, Germany
| | - Christian Opländer
- Department of Trauma and Hand Surgery, Medical Faculty, Heinrich-Heine-University of Düsseldorf, Universitätsstr. 1, Düsseldorf D-40225, Germany
| | - Victoria Kolb-Bachofen
- Research Group Immunobiology, Medical Faculty, Heinrich-Heine-University of Düsseldorf, Universitätsstr. 1, Düsseldorf D-40225, Germany
| | - Klaus-D Kröncke
- Institute of Biochemistry and Molecular Biology I, Medical Faculty, Heinrich-Heine-University of Düsseldorf, Universitätsstr. 1, Düsseldorf D-40225, Germany
| | - Christoph V Suschek
- Research Group Immunobiology, Medical Faculty, Heinrich-Heine-University of Düsseldorf, Universitätsstr. 1, Düsseldorf D-40225, Germany ; Department of Trauma and Hand Surgery, Medical Faculty, Heinrich-Heine-University of Düsseldorf, Universitätsstr. 1, Düsseldorf D-40225, Germany
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15
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Abstract
Several pathways increase the concentrations of cellular free zinc(II) ions. Such fluctuations suggest that zinc(II) ions are signalling ions used for the regulation of proteins. One function is the inhibition of enzymes. It is quite common that enzymes bind zinc(II) ions with micro- or nanomolar affinities in their active sites that contain catalytic dyads or triads with a combination of glutamate (aspartate), histidine and cysteine residues, which are all typical zinc-binding ligands. However, for such binding to be physiologically significant, the binding constants must be compatible with the cellular availability of zinc(II) ions. The affinity of inhibitory zinc(II) ions for receptor protein tyrosine phosphatase β is particularly high (Ki = 21 pM, pH 7.4), indicating that some enzymes bind zinc almost as strongly as zinc metalloenzymes. The competitive pattern of zinc inhibition for this phosphatase implicates its active site cysteine and nearby residues in the coordination of zinc. Quantitative biophysical data on both affinities of proteins for zinc and cellular zinc(II) ion concentrations provide the basis for examining the physiological significance of inhibitory zinc-binding sites in proteins and the role of zinc(II) ions in cellular signalling. Regulatory functions of zinc(II) ions add a significant level of complexity to biological control of metabolism and signal transduction and embody a new paradigm for the role of transition metal ions in cell biology.
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Affiliation(s)
- Wolfgang Maret
- King's College London, Metal Metabolism Group, Diabetes and Nutritional Sciences Division, School of Medicine, Franklin-Wilkins Bldg., 150 Stamford St., London, SE1 9NH, UK.
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16
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Abstract
The nutritional essentiality of zinc for the growth of living organisms had been recognized long before zinc biochemistry began with the discovery of zinc in carbonic anhydrase in 1939. Painstaking analytical work then demonstrated the presence of zinc as a catalytic and structural cofactor in a few hundred enzymes. In the 1980s, the field again gained momentum with the new principle of "zinc finger" proteins, in which zinc has structural functions in domains that interact with other biomolecules. Advances in structural biology and a rapid increase in the availability of gene/protein databases now made it possible to predict zinc-binding sites from metal-binding motifs detected in sequences. This procedure resulted in the definition of zinc proteomes and the remarkable estimate that the human genome encodes ∼3000 zinc proteins. More recent developments focus on the regulatory functions of zinc(II) ions in intra- and intercellular information transfer and have tantalizing implications for yet additional functions of zinc in signal transduction and cellular control. At least three dozen proteins homeostatically control the vesicular storage and subcellular distribution of zinc and the concentrations of zinc(II) ions. Novel principles emerge from quantitative investigations on how strongly zinc interacts with proteins and how it is buffered to control the remarkably low cellular and subcellular concentrations of free zinc(II) ions. It is fair to conclude that the impact of zinc for health and disease will be at least as far-reaching as that of iron.
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Affiliation(s)
- Wolfgang Maret
- King's College London, Metal Metabolism Group, Division of Diabetes and Nutritional Sciences, School of Medicine, London, United Kingdom.
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17
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Abstract
Zinc(II) ions are catalytic, structural, and regulatory cofactors in proteins. In contrast to painstakingly collecting the pieces by isolating and characterizing zinc proteins, 'omics' approaches are now allowing us to tease out information about zinc proteins from genomes and to piece together the information to a broader knowledge and appreciation of the role of zinc in biology. Estimates for the number of zinc proteins in the human genome and in genomes of other organisms have been derived from a bioinformatics approach: mining sequence databases for homologies of known zinc-coordination motifs with characteristic ligand signatures for metal binding and combining this information with the knowledge about metal-binding domains of proteins. This approach resulted in an impressive number of almost 3000 human zinc proteins and made major contributions to our understanding of the composition of the zinc proteome and the functions of zinc proteins. However, the impact of zinc on protein science is even greater. Predictions do not include yet undiscovered ligand signatures, coordination environments that employ complex binding patterns with nonsequential binding of ligands and ligand bridges, zinc/protein interactions at protein interfaces, and transient interactions of zinc(II) ions with proteins that are not known to be zinc proteins. All this information and recent discoveries of how cellular zinc is controlled and how zinc(II) ions function as signaling ions add an hitherto unrecognized dimension to the zinc proteome of multicellular eukaryotic organisms. Zinc proteomics employs a combination of approaches from different disciplines, such as bioinformatics, biology, inorganic biochemistry, and significantly, analytical and structural chemistry. It provides crucial large-scale datasets for interpreting the roles of zinc in health and disease at both a molecular and a global, systems biology, level.
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Affiliation(s)
- Wolfgang Maret
- King's College London, School of Medicine, Diabetes and Nutritional Sciences Division, Metal Metabolism Group, London, SE1 9NH, UK,
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18
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Wilson M, Hogstrand C, Maret W. Picomolar concentrations of free zinc(II) ions regulate receptor protein-tyrosine phosphatase β activity. J Biol Chem 2012; 287:9322-6. [PMID: 22275360 DOI: 10.1074/jbc.c111.320796] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
As key enzymes in the regulation of biological phosphorylations, protein-tyrosine phosphatases are central to the control of cellular signaling and metabolism. Zinc(II) ions are known to inhibit these enzymes, but the physiological significance of this inhibition has remained elusive. Employing metal buffering for strict metal control and performing a kinetic analysis, we now demonstrate that zinc(II) ions are reversible inhibitors of the cytoplasmic catalytic domain of the receptor protein-tyrosine phosphatase β (also known as vascular endothelial protein-tyrosine phosphatase). The K(i)((Zn)) value is 21 ± 7 pm, 6 orders of magnitude lower than zinc inhibition reported previously for this enzyme. It exceeds the affinity of the most potent synthetic small molecule inhibitors targeting these enzymes. Inhibition is in the range of cellular zinc(II) ion concentrations, suggesting that zinc regulates this enzyme, which is involved in vascular physiology and angiogenesis. Thus, for some enzymes that are not recognized as zinc metalloenzymes, zinc binding inhibits rather than activates as in classical zinc enzymes. Activation then requires removal of the inhibitory zinc.
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Affiliation(s)
- Matthew Wilson
- Division of Diabetes and Nutritional Sciences, School of Medicine, King's College London, London, United Kingdom
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Bosomworth HJ, Thornton JK, Coneyworth LJ, Ford D, Valentine RA. Efflux function, tissue-specific expression and intracellular trafficking of the Zn transporter ZnT10 indicate roles in adult Zn homeostasis. Metallomics 2012; 4:771-9. [DOI: 10.1039/c2mt20088k] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Toledano M, Yamauti M, Osorio E, Osorio R. Zinc-Inhibited MMP-Mediated Collagen Degradation after Different Dentine Demineralization Procedures. Caries Res 2012; 46:201-7. [DOI: 10.1159/000337315] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Accepted: 02/01/2012] [Indexed: 12/25/2022] Open
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Maret W. Metals on the move: zinc ions in cellular regulation and in the coordination dynamics of zinc proteins. Biometals 2011; 24:411-8. [DOI: 10.1007/s10534-010-9406-1] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Accepted: 12/28/2010] [Indexed: 01/03/2023]
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Zheng D, Kille P, Feeney GP, Cunningham P, Handy RD, Hogstrand C. Dynamic transcriptomic profiles of zebrafish gills in response to zinc supplementation. BMC Genomics 2010; 11:553. [PMID: 20937081 PMCID: PMC3091702 DOI: 10.1186/1471-2164-11-553] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 10/11/2010] [Indexed: 12/22/2022] Open
Abstract
Background Dietary zinc supplementation may help to promote growth, boost the immune system, protect against diabetes, and aid recovery from diarrhoea. We exploited the zebrafish (Danio rerio) gill as a unique vertebrate ion transporting epithelium model to study the time-dependent regulatory networks of gene-expression leading to homeostatic control during zinc supplementation. This organ forms a conduit for zinc uptake whilst exhibiting conservation of zinc trafficking components. Results Fish were maintained with either zinc supplemented water (4.0 μM) and diet (2023 mg zinc kg-1) or water and diet containing Zn2+ at 0.25 μM and 233 mg zinc kg-1, respectively. Gill tissues were harvested at five time points (8 hours to 14 days) and transcriptome changes analysed in quintuplicate using a 16 K microarray with results anchored to gill Zn2+ influx and whole body nutrient composition (protein, carbohydrate, lipid, elements). The number of regulated genes increased up to day 7 but declined as the fish acclimated. In total 525 genes were regulated (having a fold-change more than 1.8 fold change and an adjusted P-value less than 0.1 which is controlling a 10% False discovery rate, FDR) by zinc supplementation, but little overlap was observed between genes regulated at successive time-points. Many genes displayed cyclic expression, typical for homeostatic control mechanisms. Annotation enrichment analysis revealed strong overrepresentation of "transcription factors", with specific association evident with "steroid hormone receptors". A suite of genes linked to "development" were also statistically overrepresented. More specifically, early regulation of genes was linked to a few key transcription factors (e.g. Mtf1, Jun, Stat1, Ppara, Gata3) and was followed by hedgehog and bone morphogenic protein signalling. Conclusions The results suggest that zinc supplementation reactivated developmental pathways in the gill and stimulated stem cell differentiation, a response likely reflecting gill remodelling in response to its altered environment. This provides insight to the role of zinc during cell differentiation and illustrates the critical nature of maintaining zinc status. The study also highlights the importance of temporal transcriptomics analysis in order resolve the discrete elements of biological processes, such as zinc acclimation.
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Affiliation(s)
- Dongling Zheng
- Mineral Metabolism Group, Nutritional Sciences Division, King's College London, London SE1 9NH, UK
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Rudolf E, Červinka M. Zinc pyrithione induces cellular stress signaling and apoptosis in Hep-2 cervical tumor cells: the role of mitochondria and lysosomes. Biometals 2010; 23:339-54. [DOI: 10.1007/s10534-010-9302-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Accepted: 02/02/2010] [Indexed: 10/19/2022]
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Hargitai D, Pataki A, Raffai G, Füzi M, Dankó T, Csernoch L, Várnai P, Szigeti GP, Zsembery A. Calcium entry is regulated by Zn2+ in relation to extracellular ionic environment in human airway epithelial cells. Respir Physiol Neurobiol 2010; 170:67-75. [PMID: 19995619 DOI: 10.1016/j.resp.2009.12.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 11/02/2009] [Accepted: 12/02/2009] [Indexed: 11/27/2022]
Abstract
The extracellular pH, sodium and divalent cation concentrations influence the ATP-induced changes in cytosolic Ca(2+) concentration ([Ca(2+)](i)). This elevation of [Ca(2+)](i) and activation of Ca(2+)-dependent Cl(-) channels represent a possible therapeutic approach in cystic fibrosis (CF). We investigated the changes of [Ca(2+)](i) in different external ionic environment, and P2X purinergic receptors (P2XRs) expression in the control and CF airway epithelial cells. The parallel removal of Na(+) and alkalinization of the extracellular solution increased the amplitude of sustained ATP-induced Ca(2+) signals independent of wild-type or mutant CFTR expression. The ATP-induced Ca(2+) entry was either inhibited or stimulated by Zn(2+) depending on the extracellular Na(+) concentration. In Na(+)-free environment, Zn(2+) and other divalent cations elicited a biphasic Ca(2+) signal. Immunohistochemical data suggest that, multiple subtypes of P2XRs are expressed in these airway epithelial cells. In conclusion, Ca(2+) entry is finely regulated by external ionic environment. Therefore, we speculate that properly compiled aerosols could influence efficacy of zinc-based therapy in CF.
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Hogstrand C, Kille P, Nicholson RI, Taylor KM. Zinc transporters and cancer: a potential role for ZIP7 as a hub for tyrosine kinase activation. Trends Mol Med. 2009;15:101-111. [PMID: 19246244 DOI: 10.1016/j.molmed.2009.01.004] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Revised: 01/09/2009] [Accepted: 01/09/2009] [Indexed: 12/17/2022]
Abstract
Zinc, which is essential for many cellular processes, is controlled by zinc transporters and through buffering by metallothioneins and glutathione. Although zinc is increasingly implicated in disease states, little is known about how zinc regulates cellular biochemical pathways. Recent seminal articles have revealed discrete zinc-trafficking pathways that are linked to signalling cascades, particularly those involving protein phosphatase inhibition and downstream activation of mitogen-activated protein kinases and tyrosine kinases. Here, we discuss the mechanisms of cellular zinc homeostasis, and we propose an important role for the zinc transporter solute carrier family 39, member 7 (SLC39A7; commonly referred to as ZIP7). ZIP7 releases zinc from the endoplasmic reticulum and might be required for tyrosine kinase activation. These observations position ZIP7 at a critical node in zinc-mediated tyrosine kinase signalling and suggest that this protein might form a novel target for diseases such as cancer where prevention of tyrosine kinase activation would be therapeutically advantageous.
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Maret W. Molecular aspects of human cellular zinc homeostasis: redox control of zinc potentials and zinc signals. Biometals 2009; 22:149-57. [DOI: 10.1007/s10534-008-9186-z] [Citation(s) in RCA: 193] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Accepted: 12/07/2008] [Indexed: 11/27/2022]
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Maret W. Metallothionein redox biology in the cytoprotective and cytotoxic functions of zinc. Exp Gerontol 2008; 43:363-9. [DOI: 10.1016/j.exger.2007.11.005] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2007] [Revised: 11/16/2007] [Accepted: 11/19/2007] [Indexed: 10/22/2022]
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Abstract
Sequence databases can be searched for homologies of zinc coordination motifs with characteristic ligand signatures. Ensuing predictions that 3-10 % of the human genes encodes zinc proteins are most remarkable. But they seem conservative when considering that database mining cannot discover new signatures or coordination environments that employ nonsequential binding of ligands and sulfur-ligand bridges. Predictions also fall short for zinc/protein interactions at protein interfaces and for inhibitory zinc sites. Zinc ions transiently target proteins that are not known to be zinc proteins, adding a hitherto unrecognized dimension to the human zinc proteome. Predicted zinc sites need to be verified experimentally. The metal can be absent or sites may bind metal ions other than zinc because protein coordination environments do not have absolute specificity for zinc. The metaphor of the "galvanization of biology" continues to gain prominence in terms of the sheer number of approximately 3000 human zinc proteins and their annotation with new functions. Clearly, description of zinc proteomes cannot be pursued solely in silico and requires zinc proteomics, an integrated scientific approach. Progress hinges on a combination of bioinformatics, biology, and significantly, analytical and structural chemistry.
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Krezel A, Maret W. Thionein/metallothionein control Zn(II) availability and the activity of enzymes. J Biol Inorg Chem 2007; 13:401-9. [PMID: 18074158 DOI: 10.1007/s00775-007-0330-y] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Accepted: 11/19/2007] [Indexed: 10/22/2022]
Abstract
Fundamental issues in zinc biology are how proteins control the concentrations of free Zn(II) ions and how tightly they interact with them. Since, basically, the Zn(II) stability constants of only two cytosolic zinc enzymes, carbonic anhydrase and superoxide dismutase, have been reported, the affinity for Zn(II) of another zinc enzyme, sorbitol dehydrogenase (SDH), was determined. Its log K is 11.2 +/- 0.1, which is similar to the log K values of carbonic anhydrase and superoxide dismutase despite considerable differences in the coordination environments of Zn(II) in these enzymes. Protein tyrosine phosphatase 1B (PTP 1B), on the other hand, is not classified as a zinc enzyme but is strongly inhibited by Zn(II), with log K = 7.8 +/- 0.1. In order to test whether or not metallothionein (MT) can serve as a source for Zn(II) ions, it was used to control free Zn(II) ion concentrations. MT makes Zn(II) available for both PTP 1B and the apoform of SDH. However, whether or not Zn(II) ions are indeed available for interaction with these enzymes depends on the thionein (T) to MT ratio and the redox poise. At ratios [T/(MT + T) = 0.08-0.31] prevailing in tissues and cells, picomolar concentrations of free Zn(II) are available from MT for reconstituting apoenzymes with Zn(II). Under conditions of decreased ratios, nanomolar concentrations of free Zn(II) become available and affect enzymes that are not zinc metalloenzymes. The match between the Zn(II) buffering capacity of MT and the Zn(II) affinity of proteins suggests a function of MT in controlling cellular Zn(II) availability.
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Affiliation(s)
- Artur Krezel
- Department of Preventive Medicine and Community Health, The University of Texas Medical Branch, Galveston, TX 77555, USA
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Krezel A, Hao Q, Maret W. The zinc/thiolate redox biochemistry of metallothionein and the control of zinc ion fluctuations in cell signaling. Arch Biochem Biophys 2007; 463:188-200. [PMID: 17391643 DOI: 10.1016/j.abb.2007.02.017] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2006] [Revised: 02/08/2007] [Accepted: 02/09/2007] [Indexed: 11/29/2022]
Abstract
Free zinc ions are potent effectors of proteins. Their tightly controlled fluctuations ("zinc signals") in the picomolar range of concentrations modulate cellular signaling pathways. Sulfur (cysteine) donors generate redox-active coordination environments in proteins for the redox-inert zinc ion and make it possible for redox signals to induce zinc signals. Amplitudes of zinc signals are determined by the cellular zinc buffering capacity, which itself is redox-sensitive. In part by interfering with zinc and redox buffering, reactive species, drugs, toxins, and metal ions can elicit zinc signals that initiate physiological and pathobiochemical changes or lead to cellular injury when free zinc ions are sustained at higher concentrations. These interactions establish redox-inert zinc as an important factor in redox signaling. At the center of zinc/redox signaling are the zinc/thiolate clusters of metallothionein. They can transduce zinc and redox signals and thereby attenuate or amplify these signals.
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Affiliation(s)
- Artur Krezel
- Department of Preventive Medicine & Community Health, The University of Texas Medical Branch, Division of Human Nutrition, 700 Harborside Drive, Galveston, TX 77555, USA
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Schwiebert EM, Liang L, Cheng NL, Williams CR, Olteanu D, Welty EA, Zsembery A. Extracellular zinc and ATP-gated P2X receptor calcium entry channels: New zinc receptors as physiological sensors and therapeutic targets. Purinergic Signal 2005; 1:299-310. [PMID: 18404515 PMCID: PMC2096558 DOI: 10.1007/s11302-005-0777-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Revised: 07/06/2005] [Accepted: 07/08/2005] [Indexed: 12/15/2022] Open
Abstract
In this review, we focus on two attributes of P2X receptor channel function, one essential and one novel. First, we propose that P2X receptors are extracellular sensors as well as receptors and ion channels. In particular, the large extracellular domain (that comprises 70% of the molecular mass of the receptor channel protein) lends itself to be a cellular sensor. Moreover, its exquisite sensitivity to extracellular pH, ionic strength, and multiple ligands evokes the function of a sensor. Second, we propose that P2X receptors are extracellular zinc receptors as well as receptors for nucleotides. We provide novel data in multiple publications and illustrative data in this invited review to suggest that zinc triggers ATP-independent activation of P2X receptor channel function. In this light, P2X receptors are the cellular site of integration between autocrine and paracrine zinc signaling and autocrine and paracrine purinergic signaling. P2X receptors may sense changes in these ligands as well as in extracellular pH and ionic strength and transduce these sensations via calcium and/or sodium entry and changes in membrane potential.
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Affiliation(s)
- Erik M Schwiebert
- Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, Alabama, USA,
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Abstract
Cadmium (Cd2+) is a known carcinogen that inactivates the DNA mismatch repair (MMR) pathway. In this study, we have tested the effect of Cd2+ exposure on the enzymatic activity of the mismatch binding complex MSH2–MSH6. Our results indicate that Cd2+ is highly inhibitory to the ATP binding and hydrolysis activities of MSH2–MSH6, and less inhibitory to its DNA mismatch binding activity. The inhibition of the ATPase activity appears to be dose and exposure time dependent. However, the inhibition of the ATPase activity by Cd2+ is prevented by cysteine and histidine, suggesting that these residues are essential for the ATPase activity and are targeted by Cd2+. A comparison of the mechanism of inhibition with N-ethyl maleimide, a sulfhydryl group inhibitor, indicates that this inhibition does not occur through direct inactivation of sulfhydryl groups. Zinc (Zn2+) does not overcome the direct inhibitory effect of Cd2+ on the MSH2–MSH6 ATPase activity in vitro. However, the increase in the mutator phenotype of yeast cells exposed to Cd2+ was prevented by excess Zn2+, probably by blocking the entry of Cd2+ into the cell. We conclude that the inhibition of MMR by Cd2+ is through the inactivation of the ATPase activity of the MSH2–MSH6 heterodimer, resulting in a dominant negative effect and causing a mutator phenotype.
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Affiliation(s)
- Sreeparna Banerjee
- Institute of Molecular Medicine and Genetics, Medical College of Georgia1120 15th Street, Augusta GA 30912, USA
| | - Hernan Flores-Rozas
- Institute of Molecular Medicine and Genetics, Medical College of Georgia1120 15th Street, Augusta GA 30912, USA
- Department of Medicine, Medical College of Georgia1120 15th Street, Augusta GA 30912, USA
- To whom correspondence should be addressed at Medical College of Georgia, 1120 15th Street, CB-2803, Augusta, GA 30912, USA. Tel: +1 706 721 1371; Fax: +1 706 721 8752;
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Zsembery A, Fortenberry JA, Liang L, Bebok Z, Tucker TA, Boyce AT, Braunstein GM, Welty E, Bell PD, Sorscher EJ, Clancy JP, Schwiebert EM. Extracellular Zinc and ATP Restore Chloride Secretion across Cystic Fibrosis Airway Epithelia by Triggering Calcium Entry. J Biol Chem 2004; 279:10720-9. [PMID: 14701827 DOI: 10.1074/jbc.m313391200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cystic fibrosis (CF) is caused by defective cyclic AMP-dependent cystic fibrosis transmembrane conductance regulator Cl(-) channels. Thus, CF epithelia fail to transport Cl(-) and water. A postulated therapeutic avenue in CF is activation of alternative Ca(2+)-dependent Cl(-) channels. We hypothesized that stimulation of Ca(2+) entry from the extracellular space could trigger a sustained Ca(2+) signal to activate Ca(2+)-dependent Cl(-) channels. Cytosolic [Ca(2+)](i) was measured in non-polarized human CF (IB3-1) and non-CF (16HBE14o(-)) airway epithelial cells. Primary human CF and non-CF airway epithelial monolayers as well as Calu-3 monolayers were used to assess anion secretion. In vivo nasal potential difference measurements were performed in non-CF and two different CF mouse (DeltaF508 homozygous and bitransgenic gut-corrected but lung-null) models. Zinc and ATP induced a sustained, reversible, and reproducible increase in cytosolic Ca(2+) in CF and non-CF cells with chemistry and pharmacology most consistent with activation of P2X purinergic receptor channels. P2X purinergic receptor channel-mediated Ca(2+) entry stimulated sustained Cl(-) and HCO(3)(-) secretion in CF and non-CF epithelial monolayers. In non-CF mice, zinc and ATP induced a significant Cl(-) secretory response similar to the effects of agonists that increase intracellular cAMP levels. More importantly, in both CF mouse models, Cl(-) permeability of nasal epithelia was restored in a sustained manner by zinc and ATP. These effects were reversible and reacquirable upon removal and readdition of agonists. Our data suggest that activation of P2X calcium entry channels may have profound therapeutic benefit for CF that is independent of cystic fibrosis transmembrane conductance regulator genotype.
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Affiliation(s)
- Akos Zsembery
- Department of Physiology and Biophysics, Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama, Birmingham 35294-0005, USA.
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Abstract
The effects of zinc on the lipid components of carp erythrocytes (Cyprinus carpio L.) were studied on red blood cells exposed to ZnSO4 (0.01-1 mM) for 20 h. The temperatures of the incubation medium were 5 and 20 degrees C for carp collected in winter and summer, respectively. It was observed that increase in the concentration of metal ions in the medium led to significant changes in the content of the main phospholipid classes. Zinc induced the reduction of phosphatidylcholine as well as the increase in the content of phosphatidylserine and phosphatidylinositol. A marked increase in the levels of malondialdehyde and conjugated dienes was also found both in the cells and the incubation medium. Moreover, elevated Zn concentrations caused alterations in the erythrocyte plasma membrane fluidity, estimated by measuring the fluorescence of 1-[4-trimethylaminophenyl]-6-phenyl-1,3,5-hexatriene and 12-[9-anthroyloxy]stearic acid, located on the surface and in the hydrophobic regions of the lipid bilayer. This study in vitro confirmed that higher concentrations of zinc ions induce marked changes in the composition and structure of membrane lipids in carp erythrocytes.
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Affiliation(s)
- Gabryelak Teresa
- Department of General Biophysics, University of Lodz, Banacha 12/16, 90-237, Lodz, Poland.
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