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Hernández-Camacho JD, Vicente-García C, Parsons DS, Navas-Enamorado I. Zinc at the crossroads of exercise and proteostasis. Redox Biol 2020; 35:101529. [PMID: 32273258 PMCID: PMC7284914 DOI: 10.1016/j.redox.2020.101529] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 03/25/2020] [Accepted: 03/27/2020] [Indexed: 12/11/2022] Open
Abstract
Zinc is an essential element for all forms of life, and one in every ten human proteins is a zinc protein. Zinc has catalytic, structural and signalling functions and its correct homeostasis affects many cellular processes. Zinc deficiency leads to detrimental consequences, especially in tissues with high demand such as skeletal muscle. Zinc cellular homeostasis is tightly regulated by different transport and buffer protein systems. Specifically, in skeletal muscle, zinc has been found to affect myogenesis and muscle regeneration due to its effects on muscle cell activation, proliferation and differentiation. In relation to skeletal muscle, exercise has been shown to modulate zinc serum and urinary levels and could directly affect cellular zinc transport. The oxidative stress induced by exercise may provide the basis for the mild zinc deficiency observed in athletes and could have severe consequences on health and sport performance. Proteostasis is induced during exercise and zinc plays an essential role in several of the associated pathways. Zinc deficiency could be a crucial issue in sport performance for athletes. Exercise could modulate zinc serum and cellular homeostasis. Zinc is part of proteostatic systems critical during exercise.
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Affiliation(s)
- Juan Diego Hernández-Camacho
- Centro Andaluz de Biología del Desarrollo, CSIC-UPO-JA, Universidad Pablo de Olavide, Sevilla, 41013, Spain; CIBERER, Instituto de Salud Carlos III, Madrid, 28000, Spain
| | - Cristina Vicente-García
- Centro Andaluz de Biología del Desarrollo, CSIC-UPO-JA, Universidad Pablo de Olavide, Sevilla, 41013, Spain
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2
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Grassi F, Fucile S. Calcium influx through muscle nAChR-channels: One route, multiple roles. Neuroscience 2019; 439:117-124. [PMID: 30999028 DOI: 10.1016/j.neuroscience.2019.04.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/01/2019] [Accepted: 04/04/2019] [Indexed: 01/31/2023]
Abstract
Although Ca2+ influx through muscle nAChR-channels has been described over the past 40 years, its functions remain still poorly understood. In this review we suggest possible roles of Ca2+ entry at all stages of muscle development, summarizing the evidence present in literature. nAChRs are expressed in myoblasts prior to fusion, and can be activated in the absence of an ACh-releasing nerve terminal, with Ca2+ influx likely contributing to regulate cell fusion. Upon establishment of nerve-muscle contact, Ca2+ influx contributes to orchestrate the signaling required for the correct formation of the neuromuscular junction. Finally, in the mature synapse, Ca2+ entry through postsynaptic nAChR-channels - highly Ca2+ permeable, in particular in humans - acts on K+ and Na+ channels to shape endplate excitability. However, when genetic defects cause excessive channel activation, Ca2+ influx becomes toxic and causes endplate myopathy. Throughout the review, we highlight how Ricardo Miledi has contributed to construct this whole body of knowledge, from the initial description of Ca2+ permeability of endplate nAChR channels, to the rationale for the treatment of endplate excitotoxic damage under pathological conditions. This article is part of a Special Issue entitled: SI: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.
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Affiliation(s)
- Francesca Grassi
- Department of Physiology and Pharmacology, Sapienza University, piazzale Aldo Moro 5, 00185, Rome, Italy.
| | - Sergio Fucile
- Department of Physiology and Pharmacology, Sapienza University, piazzale Aldo Moro 5, 00185, Rome, Italy; IRCCS Neuromed, Viale dell'Elettronica, 86077, Pozzilli, Italy
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3
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Degirmenci S, Olgar Y, Durak A, Tuncay E, Turan B. Cytosolic increased labile Zn 2+ contributes to arrhythmogenic action potentials in left ventricular cardiomyocytes through protein thiol oxidation and cellular ATP depletion. J Trace Elem Med Biol 2018; 48:202-212. [PMID: 29773183 DOI: 10.1016/j.jtemb.2018.04.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 04/12/2018] [Accepted: 04/12/2018] [Indexed: 02/06/2023]
Abstract
Intracellular labile (free) Zn2+-level ([Zn2+]i) is low and increases markedly under pathophysiological conditions in cardiomyocytes. High [Zn2+]i is associated with alterations in excitability and ionic-conductances while exact mechanisms are not clarified yet. Therefore, we examined the elevated-[Zn2+]i on some sarcolemmal ionic-mechanisms, which can mediate cardiomyocyte dysfunction. High-[Zn2+]i induced significant changes in action potential (AP) parameters, including depolarization in resting membrane-potential and prolongations in AP-repolarizing phases. We detected also the time-dependent effects such as induction of spontaneous APs at the time of ≥ 3 min following [Zn2+]i increases, a manner of cellular ATP dependent and reversible with disulfide-reducing agent dithiothreitol, DTT. High-[Zn2+]i induced inhibitions in voltage-dependent K+-channel currents, such as transient outward K+-currents, Ito, steady-state currents, Iss and inward-rectifier K+-currents, IK1, reversible with DTT seemed to be responsible from the prolongations in APs. We, for the first time, demonstrated that lowering cellular ATP level induced significant decreaeses in both Iss and IK1, while no effect on Ito. However, the increased-[Zn2+]i could induce marked activation in ATP-sensitive K+-channel currents, IKATP, depending on low cellular ATP and thiol-oxidation levels of these channels. The mRNA levels of Kv4.3, Kv1.4 and Kv2.1 were depressed markedly with increased-[Zn2+]i with no change in mRNA level of Kv4.2, while the mRNA level of IKATP subunit, SUR2A was increased significantly with increased-[Zn2+]i, being reversible with DTT. Overall we demonstrated that high-[Zn2+]i, even if nanomolar levels, alters cardiac function via prolonged APs of cardiomyocytes, at most, due to inhibitions in voltage-dependent K+-currents, although activation of IKATP is playing cardioprotective role, through some biochemical changes in cellular ATP- and thiol-oxidation levels. It seems, a well-controlled [Zn2+]i can be novel therapeutic target for cardiac complications under pathological conditions including oxidative stress.
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Affiliation(s)
- Sinan Degirmenci
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey
| | - Yusuf Olgar
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey
| | - Aysegul Durak
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey
| | - Erkan Tuncay
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey
| | - Belma Turan
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey.
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4
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Taylor KA, Pugh N. The contribution of zinc to platelet behaviour during haemostasis and thrombosis. Metallomics 2016; 8:144-55. [PMID: 26727074 DOI: 10.1039/c5mt00251f] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Platelets are the primary cellular determinants of haemostasis and pathological thrombus formation leading to myocardial infarction and stroke. Following vascular injury or atherosclerotic plaque rupture, platelets are recruited to sites of damage and undergo activation induced by a variety of soluble and/or insoluble agonists. Platelet activation is a multi-step process culminating in the formation of thrombi, which contribute to the haemostatic process. Zinc (Zn(2+)) is acknowledged as an important signalling molecule in a diverse range of cellular systems, however there is limited understanding of the influence of Zn(2+) on platelet behaviour during thrombus formation. This review evaluates the contributions of exogenous and intracellular Zn(2+) to platelet function and assesses the potential pathophysiological implications of Zn(2+) signalling. We also provide a speculative assessment of the mechanisms by which platelets could respond to changes in extracellular and intracellular Zn(2+) concentration.
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Affiliation(s)
- K A Taylor
- Department of Biomedical and Forensic Sciences, Faculty of Science and Technology, Anglia Ruskin University, Cambridge, CB1 1PT, UK.
| | - N Pugh
- Department of Biomedical and Forensic Sciences, Faculty of Science and Technology, Anglia Ruskin University, Cambridge, CB1 1PT, UK.
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5
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Liang X, Dempski RE, Burdette SC. Zn(2+) at a cellular crossroads. Curr Opin Chem Biol 2016; 31:120-5. [PMID: 27010344 PMCID: PMC4870122 DOI: 10.1016/j.cbpa.2016.02.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/18/2016] [Indexed: 11/27/2022]
Abstract
Zinc is an essential micronutrient for cellular homeostasis. Initially proposed to only contribute to cellular viability through structural roles and non-redox catalysis, advances in quantifying changes in nM and pM quantities of Zn(2+) have elucidated increasing functions as an important signaling molecule. This includes Zn(2+)-mediated regulation of transcription factors and subsequent protein expression, storage and release of intracellular compartments of zinc quanta into the extracellular space which modulates plasma membrane protein function, as well as intracellular signaling pathways which contribute to the immune response. This review highlights some recent advances in our understanding of zinc signaling.
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Affiliation(s)
- Xiaomeng Liang
- Worcester Polytechnic Institute, Department of Chemistry and Biochemistry, Worcester, MA 01609-2280, United States
| | - Robert E Dempski
- Worcester Polytechnic Institute, Department of Chemistry and Biochemistry, Worcester, MA 01609-2280, United States
| | - Shawn C Burdette
- Worcester Polytechnic Institute, Department of Chemistry and Biochemistry, Worcester, MA 01609-2280, United States.
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Inoue K, O'Bryant Z, Xiong ZG. Zinc-permeable ion channels: effects on intracellular zinc dynamics and potential physiological/pathophysiological significance. Curr Med Chem 2015; 22:1248-57. [PMID: 25666796 PMCID: PMC4363167 DOI: 10.2174/0929867322666150209153750] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 10/14/2014] [Accepted: 02/02/2015] [Indexed: 02/08/2023]
Abstract
Zinc (Zn(2+)) is one of the most important trace metals in the body. It is necessary for the normal function of a large number of protein s including enzymes and transcription factors. While extracellular fluid may contain up to micromolar Zn(2+), intracellular Zn(2+) concentration is generally maintained at a subnanomolar level; this steep gradient across the cell membrane is primarily attributable to Zn(2+) extrusion by Zn(2+) transporting systems. Interestingly, systematic investigation has revealed that activities, previously believed to be dependent on calcium (Ca(2+)), may be partially mediated by Zn(2+). This is also supported by new findings that some Ca(2+)-permeable channels such as voltage-dependent calcium channels (VDCCs), N-methyl-D-aspartate receptors (NMDA), and amino-3- hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPA-Rs) are also permeable to Zn(2+). Thus, the importance of Zn(2+) in physiological and pathophysiological processes is now more widely appreciated. In this review, we describe Zn(2+)- permeable membrane molecules, especially Zn(2+)-permeable ion channels, in intracellular Zn(2+)dynamics and Zn(2+) mediated physiology/pathophysiology.
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Affiliation(s)
- Koichi Inoue
- Neuroscience Institute, Morehouse School of Medicine, Atlanta, USA.
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Bouron A, Oberwinkler J. Contribution of calcium-conducting channels to the transport of zinc ions. Pflugers Arch 2013; 466:381-7. [PMID: 23719866 DOI: 10.1007/s00424-013-1295-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 05/10/2013] [Accepted: 05/10/2013] [Indexed: 10/26/2022]
Abstract
Zinc (Zn) is a vital nutrient participating in a myriad of biological processes. The mechanisms controlling its transport through the plasma membrane are far from being completely understood. Two families of eukaryotic zinc transporters are known to date: the Zip (SLC39) and ZnT (SLC30) proteins. In addition, some types of plasmalemmal calcium (Ca)-conducting channels are implied in the cellular uptake of zinc. These ion channels are currently described as systems dedicated to the transport of Ca (and, to some extent, sodium (Na) ions). However, a growing body of evidence supports the view that some of them can also function as pathways for Zn transport. For instance, voltage-gated Ca channels and some types of glutamate-gated receptors have long been known to allow the entry of Zn. More recently, members of the TRP superfamily, another type of Ca-conducting channels, have been shown to permit the uptake of Zn into eukaryotic cells. The aim of this review article is to present the current knowledge supporting the notion that Ca-conducting channels take part in the plasmalemmal transport of Zn.
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Yang W, Manna PT, Zou J, Luo J, Beech DJ, Sivaprasadarao A, Jiang LH. Zinc inactivates melastatin transient receptor potential 2 channels via the outer pore. J Biol Chem 2011; 286:23789-98. [PMID: 21602277 PMCID: PMC3129160 DOI: 10.1074/jbc.m111.247478] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 05/19/2011] [Indexed: 10/18/2022] Open
Abstract
Zinc ion (Zn(2+)) is an endogenous allosteric modulator that regulates the activity of a wide variety of ion channels in a reversible and concentration-dependent fashion. Here we used patch clamp recording to study the effects of Zn(2+) on the melastatin transient receptor potential 2 (TRPM2) channel. Zn(2+) inhibited the human (h) TRPM2 channel currents, and the steady-state inhibition was largely not reversed upon washout and concentration-independent in the range of 30-1000 μM, suggesting that Zn(2+) induces channel inactivation. Zn(2+) inactivated the channels fully when they conducted inward currents, but only by half when they passed outward currents, indicating profound influence of the permeant ion on Zn(2+) inactivation. Alanine substitution scanning mutagenesis of 20 Zn(2+)-interacting candidate residues in the outer pore region of the hTRPM2 channel showed that mutation of Lys(952) in the extracellular end of the fifth transmembrane segment and Asp(1002) in the large turret strongly attenuated or abolished Zn(2+) inactivation, and mutation of several other residues dramatically changed the inactivation kinetics. The mouse (m) TRPM2 channels were also inactivated by Zn(2+), but the kinetics were remarkably slower. Reciprocal mutation of His(995) in the hTRPM2 channel and the equivalent Gln(992) in the mTRPM2 channel completely swapped the kinetics, but no such opposing effects resulted from exchanging another pair of species-specific residues, Arg(961)/Ser(958). We conclude from these results that Zn(2+) inactivates the TRPM2 channels and that residues in the outer pore are critical determinants of the inactivation.
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Affiliation(s)
- Wei Yang
- From the Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom and
- the Department of Neurobiology, Zhejiang University School of Medicine, Zhejiang 310058, China
| | - Paul T. Manna
- From the Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Jie Zou
- From the Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Jianhong Luo
- the Department of Neurobiology, Zhejiang University School of Medicine, Zhejiang 310058, China
| | - David J. Beech
- From the Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Asipu Sivaprasadarao
- From the Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Lin-Hua Jiang
- From the Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom and
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Kovacs G, Danko T, Bergeron MJ, Balazs B, Suzuki Y, Zsembery A, Hediger MA. Heavy metal cations permeate the TRPV6 epithelial cation channel. Cell Calcium 2010; 49:43-55. [PMID: 21146870 DOI: 10.1016/j.ceca.2010.11.007] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 11/10/2010] [Accepted: 11/15/2010] [Indexed: 11/30/2022]
Abstract
TRPV6 belongs to the vanilloid family of the transient receptor potential channel (TRP) superfamily. This calcium-selective channel is highly expressed in the duodenum and the placenta, being responsible for calcium absorption in the body and fetus. Previous observations have suggested that TRPV6 is not only permeable to calcium but also to other divalent cations in epithelial tissues. In this study, we tested whether TRPV6 is indeed also permeable to cations such as zinc and cadmium. We found that the basal intracellular calcium concentration was higher in HEK293 cells transfected with hTRPV6 than in non-transfected cells, and that this difference almost disappeared in nominally calcium-free solution. Live cell imaging experiments with Fura-2 and NewPort Green DCF showed that overexpression of human TRPV6 increased the permeability for Ca(2+), Ba(2+), Sr(2+), Mn(2+), Zn(2+), Cd(2+), and interestingly also for La(3+) and Gd(3+). These results were confirmed using the patch clamp technique. (45)Ca uptake experiments showed that cadmium, lanthanum and gadolinium were also highly efficient inhibitors of TRPV6-mediated calcium influx at higher micromolar concentrations. Our results suggest that TRPV6 is not only involved in calcium transport but also in the transport of other divalent cations, including heavy metal ions, which may have toxicological implications.
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Affiliation(s)
- Gergely Kovacs
- Institute of Biochemistry and Molecular Medicine, University of Bern, Switzerland.
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Bacher I, Zidar A, Kratzel M, Hohenegger M. Channelling of substrate promiscuity of the skeletal-muscle ADP-ribosyl cyclase isoform. Biochem J 2004; 381:147-54. [PMID: 15084143 PMCID: PMC1133772 DOI: 10.1042/bj20031977] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2003] [Revised: 03/30/2004] [Accepted: 04/15/2004] [Indexed: 12/19/2022]
Abstract
The novel Ca2+-mobilizing second messengers cADPr (cyclic ADP-ribose) and NAADP (nicotinic acid-adenine dinucleotide phosphate) are both synthesized by ADP-ribosyl cyclases. Using HSR (heavy sarcoplasmic reticulum) fractions from rabbit skeletal muscle, NAADP-induced Ca2+ release was observed. In the present paper, we show in HSR membranes the formation of authentic cADPr, cGDPr (cyclic GDP-ribose) and NAADP. The cyclization reaction to form cADPr and cGDPr as well as the base-exchange reaction to form NAADP were strictly dependent on pH. Although the formation of cGDPr is optimized at pH 6, the synthesis of NAADP was most pronounced at a pH below 5. A novel regulation mechanism is provided for nicotinic acid, the co-substrate for NAADP synthesis. Nicotinic acid had virtually no influence on the cyclization reaction, but increased the affinity of NADP at an acidic pH and had the opposite effect at alkaline pH. Nicotinamide, the side product of cADPr synthesis, is an inhibitor of the cyclization reaction (IC50, 0.7+/-0.1 mM) and was 30-fold more potent at suppressing the base-exchange reaction. Although the synthesis of NAADP was highly sensitive to nicotinamide inhibition, this was not via a competition with the nicotinic-acid-binding site. In contrast with the ecto-ADP-ribosyl cyclase (CD38), the cyclization and base-exchange reaction of the skeletal muscle isoform was inhibited by Cu2+ and Zn2+, while other bivalent cations such as Ca2+, Mg2+ and Mn2+ had virtually no effect. These findings allow for the prediction of a novel ADP-ribosyl cyclase isoform in skeletal muscle HSR, other than CD38. Hence the enzymic prerequisite for cADPr- and NAADP-mediated Ca2+ signalling is present.
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Affiliation(s)
- Ingrid Bacher
- *Institute of Pharmacology, Waehringerstrasse 13A, University of Vienna, A-1090 Vienna, Austria
| | - Andreas Zidar
- *Institute of Pharmacology, Waehringerstrasse 13A, University of Vienna, A-1090 Vienna, Austria
| | - Martin Kratzel
- †Institute of Pharmaceutical Chemistry, Althanstrasse 14, University of Vienna, A-1090 Vienna, Austria
| | - Martin Hohenegger
- *Institute of Pharmacology, Waehringerstrasse 13A, University of Vienna, A-1090 Vienna, Austria
- To whom correspondence should be addressed (e-mail )
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Grassi F, Pagani F, Spinelli G, De Angelis L, Cossu G, Eusebi F. Fusion-independent expression of functional ACh receptors in mouse mesoangioblast stem cells contacting muscle cells. J Physiol 2004; 560:479-89. [PMID: 15319417 PMCID: PMC1665253 DOI: 10.1113/jphysiol.2004.070607] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mesoangioblasts are vessel-associated fetal stem cells that can be induced to differentiate into skeletal muscle, both in vitro and in vivo. Whether this is due to fusion or to transdifferentiation into bona fide satellite cells is still an open question, for mesoangioblasts as well as for other types of stem cells. The early steps of satellite cell myogenic differentiation involve MyoD activation, membrane hyperpolarization and the appearance of ACh sensitivity and gap junctional communication. If mesoangioblasts differentiate into satellite cells, these characteristics should be observed in stem cells prior to fusion into multinucleated myotubes. We have investigated the functional properties acquired by mononucleated green fluorescent protein (GFP)-positive mesoangioblasts co-cultured with differentiating C2C12 myogenic cells, using the patch-clamp technique. Mesoangioblasts whose membrane contacted myogenic cells developed a hyperpolarized membrane resting potential and ACh-evoked current responses. Dye and electrical coupling was observed among mesoangioblasts but not between mesoangioblasts and myotubes. Mouse MyoD was detected by RT-PCR both in single, mononucleated mesoangioblasts co-cultured with C2C12 myotubes and in the total mRNA from mouse mesoangioblasts co-cultured with human myotubes, but not in human myotubes or stem cells cultured in isolation. In conclusion, when co-cultured with muscle cells, mesoangioblasts acquire many of the functional characteristics of differentiating satellite cells in the absence of cell fusion, strongly indicating that these stem cells undergo transdifferentiation into satellite cells, when exposed to a myogenic environment.
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Affiliation(s)
- Francesca Grassi
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Fisiologia Umana e Farmacologia and Centro di Eccellenza BEMM, Università La Sapienza Piazzale Aldo Moro 5, I-00185 Roma, Italy.
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12
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Prost AL, Bloc A, Hussy N, Derand R, Vivaudou M. Zinc is both an intracellular and extracellular regulator of KATP channel function. J Physiol 2004; 559:157-67. [PMID: 15218066 PMCID: PMC1665068 DOI: 10.1113/jphysiol.2004.065094] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Extracellular Zn(2+) has been identified as an activator of pancreatic K(ATP) channels. We further examined the action of Zn(2+) on recombinant K(ATP) channels formed with the inward rectifier K(+) channel subunit Kir6.2 associated with either the pancreatic/neuronal sulphonylurea receptor 1 (SUR1) subunit or the cardiac SUR2A subunit. Zn(2+), applied at either the extracellular or intracellular side of the membrane appeared as a potent, reversible activator of K(ATP) channels. External Zn(2+), at micromolar concentrations, activated SUR1/Kir6.2 but induced a small inhibition of SUR2A/Kir6.2 channels. Cytosolic Zn(2+) dose-dependently stimulated both SUR1/Kir6.2 and SUR2A/Kir6.2 channels, with half-maximal effects at 1.8 and 60 microm, respectively, but it did not affect the Kir6.2 subunit expressed alone. These observations point to an action of both external and internal Zn(2+) on the SUR subunit. Effects of internal Zn(2+) were not due to Zn(2+) leaking out, since they were unaffected by the presence of a Zn(2+) chelator on the external side. Similarly, internal chelators did not affect activation by external Zn(2+). Therefore, Zn(2+) is an endogenous K(ATP) channel opener being active on both sides of the membrane, with potentially distinct sites of action located on the SUR subunit. These findings uncover a novel regulatory pathway targeting K(ATP) channels, and suggest a new role for Zn(2+) as an intracellular signalling molecule.
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Affiliation(s)
- Anne-Lise Prost
- Biophysique Moléculaire & Cellulaire, CNRS UMR5090, CEA/DRDC, 17 rue des Martyrs, 38054 Grenoble, France
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Jiang P, Guo Z. Fluorescent detection of zinc in biological systems: recent development on the design of chemosensors and biosensors. Coord Chem Rev 2004. [DOI: 10.1016/j.cct.2003.10.013] [Citation(s) in RCA: 739] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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14
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Wagner S, Dorchies OM, Stoeckel H, Warter JM, Poindron P, Takeda K. Functional maturation of nicotinic acetylcholine receptors as an indicator of murine muscular differentiation in a new nerve-muscle co-culture system. Pflugers Arch 2003; 447:14-22. [PMID: 14976589 DOI: 10.1007/s00424-003-1135-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2003] [Accepted: 06/17/2003] [Indexed: 10/26/2022]
Abstract
Under normal conditions in situ, muscle fibers and motoneurons, the main partners of motor units, are strongly dependent on each other. This interdependence hinders ex vivo studies of neuromuscular disorders where nervous or muscular components are considered separately. To allow in vitro access to complex nerve-muscle relationships, we developed a novel nerve-muscle co-culture system where mouse muscle innervation is assured by rat spinal cord explants. The degree of muscular maturation during co-culture was evaluated using the distribution of nicotinic acetylcholine receptors (AChRs) and their electrophysiological characteristics before and after innervation. In myotubes from non-innervated cultures, AChRs were diffusely distributed over the entire myotube surface. Their single-channel conductance (33.5+/-0.6 pS) and mean open time (8.1+/-0.7 ms) are characteristic of AChRs described in embryonic or denervated skeletal muscles. In innervated muscle fibers from co-cultures, AChRs appear as discrete aggregates and co-localize with synaptotagmin. In addition to the embryonic type currents, in innervated fibers AChR currents having high conductance (53.3+/-5.9 pS) and short mean open time (2.6+/-0.1 ms), characteristic of AChRs at mature neuromuscular junctions, were observed. Our data support the use of this new nerve-muscle co-culture system as a reliable model for the study of murine muscular differentiation and function.
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Affiliation(s)
- Stéphanie Wagner
- Laboratoire de Pathologie des Communications entre Cellules Nerveuses et Musculaires, EA2308, Faculté de Pharmacie, Université Louis Pasteur de Strasbourg, 74 route du Rhin, BP 24, 67401 Illkirch, France
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MacDiarmid CW, Milanick MA, Eide DJ. Induction of the ZRC1 metal tolerance gene in zinc-limited yeast confers resistance to zinc shock. J Biol Chem 2003; 278:15065-72. [PMID: 12556516 DOI: 10.1074/jbc.m300568200] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Zinc is an essential nutrient but toxic to cells with overaccumulation. For this reason, intracellular zinc levels are tightly controlled. In the yeast Saccharomyces cerevisiae, the Zrc1 and Cot1 proteins have been implicated in the storage and detoxification of excess zinc in the vacuole. Surprisingly, transcription of ZRC1 is induced in zinc-limited cells by the zinc-responsive transcription factor Zap1. We show here that this increase in ZRC1 expression is a novel mechanism of zinc homeostasis and stress tolerance. Zinc-limited cells also express high levels of the plasma membrane zinc uptake transporters. As a consequence, when zinc-limited cells are resupplied with small amounts of zinc, large quantities quickly accumulate in the cell, a condition we refer to as "zinc shock." We show here that ZRC1 and its induction in zinc-limited cells are required for resistance to this zinc shock. Experiments using the zinc-responsive fluorophore FuraZin-1 as an indicator of vacuolar zinc levels indicated that Zrc1 is required for the rapid transport of zinc into the vacuole during zinc shock. We also present evidence that cytosolic zinc rises to higher levels in cells unable to sequester this excess zinc. Thus, the increase in ZRC1 expression occurs prior to the zinc shock stress for which this induction is important. We propose that this "proactive" strategy of homeostatic regulation, such as we document here for ZRC1, may represent a common but largely unrecognized phenomenon.
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Affiliation(s)
- Colin W MacDiarmid
- Departments of Nutritional Sciences and Physiology, University of Missouri, Columbia, Missouri 65211, USA
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Jia Y, Jeng JM, Sensi SL, Weiss JH. Zn2+ currents are mediated by calcium-permeable AMPA/kainate channels in cultured murine hippocampal neurones. J Physiol 2002; 543:35-48. [PMID: 12181280 PMCID: PMC2290471 DOI: 10.1113/jphysiol.2002.020172] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Permeation of the endogenous cation Zn2+ through calcium-permeable AMPA/kainate receptor-gated (Ca-A/K) channels might subserve pathological and/or physiological signalling roles. Voltage-clamp recording was used to directly assess Zn2+ flux through these channels on cultured murine hippocampal neurones. Ca-A/K channels were present in large numbers only on a minority of neurones (Ca-A/K+ neurones), many of which were GABAergic. The presence of these channels was assessed in whole-cell or outside-out patch recording as the degree of inward rectification of kainate-activated currents, quantified via a rectification index (RI = G+40/G-60), which ranged from <0.4 (strongly inwardly rectifying) to >2 (outwardly rectifying). The specificity of a low RI as an indication of robust Ca-A/K channel expression was verified by two other techniques, kainate-stimulated cobalt-uptake labelling, and fluorescence imaging of kainate-induced increases in intracellular Ca2+. In addition, the degree of inward rectification of kainate-activated currents correlated strongly with the positive shift of the reversal potential (V(rev)) upon switching to a sodium-free, 10 mM Ca2+ buffer. With Zn2+ (3 mM) as the only permeant extracellular cation, kainate-induced inward currents were only observed in neurones that had previously been identified as Ca-A/K+. A comparison between the V(rev) observed with 3 mM Zn2+ and that observed with Ca2+ as the permeant cation revealed a P(Ca)/P(Zn) of approximately 1.8. Inward currents recorded in 3 mM Ca2+ were unaffected by the addition of 0.3 mM Zn2+, while microfluorimetrically detected increases in the intracellular concentration of Zn2+ in Ca-A/K+ neurones upon kainate exposure in the presence of 0.3 mM Zn2+ were only mildly attenuated by the addition of 1.8 mM Ca2+. These results provide direct evidence that Zn2+ can carry currents through Ca-A/K channels, and that there is little interference between Ca2+ and Zn2+ in permeating these channels.
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Affiliation(s)
- Yousheng Jia
- Department of Neurology, University of California at Irvine, CA 92697-4292, USA
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