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Chen Y, Wang X, Zhai H, Zhang Y, Huang J. Identification of Potential Human Ryanodine Receptor 1 Agonists and Molecular Mechanisms of Natural Small-Molecule Phenols as Anxiolytics. ACS OMEGA 2021; 6:29940-29954. [PMID: 34778666 PMCID: PMC8582060 DOI: 10.1021/acsomega.1c04468] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 10/18/2021] [Indexed: 06/13/2023]
Abstract
Natural small-molecule phenols (NSMPs) possess certain ubiquitous bioactivities including the anxiolytic effect. Ryanodine receptor 1 (RyR1) may be one of the potentially critical pharmacological targets for studying the anxiolytic activity of NSMPs. However, detailed molecular mechanisms of NSMPs have not been fully clarified. This research was intended to identify potent hRyR1 agonists from NSMPs and investigate whether RyR1 plays a role in their anxiolytic effect. Homology modeling and molecular docking analysis were performed using Accelrys Discovery Studio 2.5. The most appropriate concentrations of NSMPs to activate RyR1 were measured using the MTT assay. Fluorescence analyses of the intracellular calcium levels and western blotting analysis were carried out to validate whether NSMPs could regulate the calcium flux to some extent by activating RyR1. The results demonstrated that xanthotoxol and 5-hydroxy-1,4-naphthalenedione can be screened as hit compounds for potential agonists of hRyR1 to exert the anxiolytic effect. In conclusion, NSMPs might be a kind of pharmacological signal carrier, acting on RyR1 as an agonist and resulting in calcium ion mobilization from intracellular calcium ion store.
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Affiliation(s)
- Yahong Chen
- School
of Chinese Materia Medica, Beijing University
of Chinese Medicine, Yangguang South Road, Fangshan District, Beijing 102488, China
| | - Xiaohong Wang
- School
of Chinese Materia Medica, Beijing University
of Chinese Medicine, Yangguang South Road, Fangshan District, Beijing 102488, China
| | - Haifeng Zhai
- National
Institute on Drug Dependence, Peking University, 38#, Xueyuan Road, Haidian District, Beijing 100191, China
| | - Yanling Zhang
- School
of Chinese Materia Medica, Beijing University
of Chinese Medicine, Yangguang South Road, Fangshan District, Beijing 102488, China
| | - Jianmei Huang
- School
of Chinese Materia Medica, Beijing University
of Chinese Medicine, Yangguang South Road, Fangshan District, Beijing 102488, China
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2
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Szabó I, Varga C. Finding possible pharmacological effects of identified organic compounds in medicinal waters (BTEX and phenolic compounds). INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2020; 64:989-995. [PMID: 31673767 PMCID: PMC7266787 DOI: 10.1007/s00484-019-01808-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 08/15/2019] [Accepted: 08/17/2019] [Indexed: 05/09/2023]
Abstract
Medicinal thermal waters consist of a mixture of different organic and inorganic compounds. Traditionally, these waters are only characterized and classified by their inorganic composition; however, the bioavailability of the majority of these inorganic compounds is limited. Many authors investigate the organic fractions of thermal waters. These authors propose that these compounds have a potential effect on health. To elucidate the underlying mechanisms, it is crucial to know the composition of the organic fractions. The absorption of these compounds on intact skin or mucosa is notable. Some of them have local anaesthetic effect or affect receptors in the central nervous system. In the knowledge of the chemical composition, we are able to estimate the possible pharmacological effect or might be able to assess possible toxicity risks. In the present article, we aim to review possible health effects of two of the identified organic fractions: benzene and alkylbenzenes and phenolic compounds that might correlate with the therapeutic effect on rheumatological or other diseases.
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Affiliation(s)
- István Szabó
- Department of Environmental Health, Institute of Public Health Medicie, Medical School, University of Pécs, 12. Szigeti St., Pécs, H7624, Hungary.
| | - Csaba Varga
- Department of Environmental Health, Institute of Public Health Medicie, Medical School, University of Pécs, 12. Szigeti St., Pécs, H7624, Hungary
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3
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Roca FJ, Whitworth LJ, Redmond S, Jones AA, Ramakrishnan L. TNF Induces Pathogenic Programmed Macrophage Necrosis in Tuberculosis through a Mitochondrial-Lysosomal-Endoplasmic Reticulum Circuit. Cell 2019; 178:1344-1361.e11. [PMID: 31474371 PMCID: PMC6736209 DOI: 10.1016/j.cell.2019.08.004] [Citation(s) in RCA: 127] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 05/15/2019] [Accepted: 08/02/2019] [Indexed: 01/07/2023]
Abstract
Necrosis of infected macrophages constitutes a critical pathogenetic event in tuberculosis by releasing mycobacteria into the growth-permissive extracellular environment. In zebrafish infected with Mycobacterium marinum or Mycobacterium tuberculosis, excess tumor necrosis factor triggers programmed necrosis of infected macrophages through the production of mitochondrial reactive oxygen species (ROS) and the participation of cyclophilin D, a component of the mitochondrial permeability transition pore. Here, we show that this necrosis pathway is not mitochondrion-intrinsic but results from an inter-organellar circuit initiating and culminating in the mitochondrion. Mitochondrial ROS induce production of lysosomal ceramide that ultimately activates the cytosolic protein BAX. BAX promotes calcium flow from the endoplasmic reticulum into the mitochondrion through ryanodine receptors, and the resultant mitochondrial calcium overload triggers cyclophilin-D-mediated necrosis. We identify ryanodine receptors and plasma membrane L-type calcium channels as druggable targets to intercept mitochondrial calcium overload and necrosis of mycobacterium-infected zebrafish and human macrophages. TNF induces mitochondrial ROS to cause necrosis of mycobacterium-infected macrophages Mitochondrial ROS activate lysosomal enzymes that lead to BAX activation BAX activates ER ryanodine receptors to cause Ca2+ flow into the mitochondrion Drugs preventing mitochondrial Ca2+ overload prevent pathogenic macrophage necrosis in TB
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Affiliation(s)
- Francisco J Roca
- Molecular Immunity Unit, Department of Medicine, University of Cambridge, MRC Laboratory of Molecular Biology, Cambridge CB2 OQH, UK.
| | - Laura J Whitworth
- Molecular Immunity Unit, Department of Medicine, University of Cambridge, MRC Laboratory of Molecular Biology, Cambridge CB2 OQH, UK
| | - Sarah Redmond
- Molecular Immunity Unit, Department of Medicine, University of Cambridge, MRC Laboratory of Molecular Biology, Cambridge CB2 OQH, UK; Department of Microbiology, University of Washington, Seattle, WA 98195, USA
| | - Ana A Jones
- Molecular Immunity Unit, Department of Medicine, University of Cambridge, MRC Laboratory of Molecular Biology, Cambridge CB2 OQH, UK
| | - Lalita Ramakrishnan
- Molecular Immunity Unit, Department of Medicine, University of Cambridge, MRC Laboratory of Molecular Biology, Cambridge CB2 OQH, UK; Department of Microbiology, University of Washington, Seattle, WA 98195, USA.
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4
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Lu H, Chen I, Shimoda LA, Park Y, Zhang C, Tran L, Zhang H, Semenza GL. Chemotherapy-Induced Ca 2+ Release Stimulates Breast Cancer Stem Cell Enrichment. Cell Rep 2017; 18:1946-1957. [PMID: 28228260 DOI: 10.1016/j.celrep.2017.02.001] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 12/29/2016] [Accepted: 01/30/2017] [Indexed: 12/16/2022] Open
Abstract
Breast cancer stem cells (BCSCs) play a critical role in tumor recurrence and metastasis. Exposure of breast cancer cells to chemotherapy leads to an enrichment of BCSCs. Here, we find that chemotherapy induces the expression of glutathione S-transferase omega 1 (GSTO1), which is dependent on hypoxia-inducible factor 1 (HIF-1) and HIF-2. Knockdown of GSTO1 expression abrogates carboplatin-induced BCSC enrichment, decreases tumor initiation and metastatic capacity, and delays tumor recurrence after chemotherapy. GSTO1 interacts with the ryanodine receptor RYR1 and promotes calcium release from the endoplasmic reticulum. Increased cytosolic calcium levels activate PYK2 → SRC → STAT3 signaling, leading to increased expression of pluripotency factors and BCSC enrichment. HIF inhibition blocks chemotherapy-induced GSTO1 expression and BCSC enrichment. Combining HIF inhibitors with chemotherapy may improve clinical outcome in breast cancer.
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Affiliation(s)
- Haiquan Lu
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ivan Chen
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Youngrok Park
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Chuanzhao Zhang
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Linh Tran
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Huimin Zhang
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Gregg L Semenza
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Departments of Pediatrics, Medicine, Oncology, Radiation Oncology, and Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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5
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Horio F, Sakurai H, Ohsawa Y, Nakano S, Matsukura M, Fujii I. Functional validation and expression analysis of myotubes converted from skin fibroblasts using a simple direct reprogramming strategy. eNeurologicalSci 2016; 6:9-15. [PMID: 29260008 PMCID: PMC5721582 DOI: 10.1016/j.ensci.2016.11.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Accepted: 11/01/2016] [Indexed: 12/07/2022] Open
Abstract
Previously, we reported that MyoD, a master gene for myogenic cells, could efficiently convert primary skin fibroblasts into myoblasts and myotubes, thereby effecting direct reprogramming. In this study, we further demonstrated that MyoD-expressing primary fibroblasts displayed rapid movement in culture, with a movement velocity that was significantly faster, almost four times, than mouse primary myoblasts. MyoD-transduced cells obtained the characteristics of Ca2 + release and electrically-stimulated contraction, which was comparable to C2C12 myotubes, suggesting that the essential features of muscle were observed in the transduced cells. Furthermore, the ability to fuse to the host myoblasts means that gene transfer from MyoD-transduced cells to host muscle cells could be obtained by cell fusion. In comparison with the iPS method (indirect reprogramming), our transduction method has a low risk for tumorigenesis and carcinogenesis because the starting cells are fibroblasts and the transduced cells are myoblasts, both normal and mortal cells. Accordingly, MyoD transduction of human skin fibroblasts using the adenoviral vector is a simple, inexpensive and promising candidate as a new cell transplantation therapy for patients with muscular disorders. Adenoviral MyoD vector transduced fibroblasts directly to myoblasts. Myoblast cells were well differentiated into functional muscle cells. Direct reprogramming is cost-effective and safe compared to iPS method. Cell fusion and high motility were observed in MyoD-transduced cells. Transduced cells are candidates for cell transplantation in muscle disorders.
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Affiliation(s)
- Fukuko Horio
- Laboratory of Clinical Pharmacology and Therapeutics, Division of Clinical Pharmacy, Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences, Sojo University, 4-22-1 Ikeda, Nishi-ku, Kumamoto 860-0082, Japan
| | - Hidetoshi Sakurai
- Center for iPS Cell Research and Application (CiRA), Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
| | - Yutaka Ohsawa
- Department of Neurology, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama 701-0192, Japan
| | - Shiho Nakano
- Laboratory of Clinical Pharmacology and Therapeutics, Division of Clinical Pharmacy, Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences, Sojo University, 4-22-1 Ikeda, Nishi-ku, Kumamoto 860-0082, Japan
| | - Makoto Matsukura
- Laboratory of Clinical Pharmacology and Therapeutics, Division of Clinical Pharmacy, Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences, Sojo University, 4-22-1 Ikeda, Nishi-ku, Kumamoto 860-0082, Japan
| | - Isao Fujii
- Laboratory of Clinical Pharmacology and Therapeutics, Division of Clinical Pharmacy, Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences, Sojo University, 4-22-1 Ikeda, Nishi-ku, Kumamoto 860-0082, Japan
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6
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Wagner LE, Groom LA, Dirksen RT, Yule DI. Characterization of ryanodine receptor type 1 single channel activity using "on-nucleus" patch clamp. Cell Calcium 2014; 56:96-107. [PMID: 24972488 DOI: 10.1016/j.ceca.2014.05.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 05/27/2014] [Accepted: 05/28/2014] [Indexed: 12/13/2022]
Abstract
In this study, we provide the first description of the biophysical and pharmacological properties of ryanodine receptor type 1 (RyR1) expressed in a native membrane using the on-nucleus configuration of the patch clamp technique. A stable cell line expressing rabbit RyR1 was established (HEK-RyR1) using the FLP-in 293 cell system. In contrast to untransfected cells, RyR1 expression was readily demonstrated by immunoblotting and immunocytochemistry in HEK-RyR1 cells. In addition, the RyR1 agonists 4-CMC and caffeine activated Ca(2+) release that was inhibited by high concentrations of ryanodine. On nucleus patch clamp was performed in nuclei prepared from HEK-RyR1 cells. Raising the [Ca(2+)] in the patch pipette resulted in the appearance of a large conductance cation channel with well resolved kinetics and the absence of prominent subconductance states. Current versus voltage relationships were ohmic and revealed a chord conductance of ∼750pS or 450pS in symmetrical 250mM KCl or CsCl, respectively. The channel activity was markedly enhanced by caffeine and exposure to ryanodine resulted in the appearance of a subconductance state with a conductance ∼40% of the full channel opening with a Po near unity. In total, these properties are entirely consistent with RyR1 channel activity. Exposure of RyR1 channels to cyclic ADP ribose (cADPr), nicotinic acid adenine dinucleotide phosphate (NAADP) or dantrolene did not alter the single channel activity stimulated by Ca(2+), and thus, it is unlikely these molecules directly modulate RyR1 channel activity. In summary, we describe an experimental platform to monitor the single channel properties of RyR channels. We envision that this system will be influential in characterizing disease-associated RyR mutations and the molecular determinants of RyR channel modulation.
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Affiliation(s)
- Larry E Wagner
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Ave, Rochester, NY 14642, United States
| | - Linda A Groom
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Ave, Rochester, NY 14642, United States
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Ave, Rochester, NY 14642, United States
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Ave, Rochester, NY 14642, United States.
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7
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Zeng B, Chen GL, Daskoulidou N, Xu SZ. The ryanodine receptor agonist 4-chloro-3-ethylphenol blocks ORAI store-operated channels. Br J Pharmacol 2014; 171:1250-9. [PMID: 24670147 PMCID: PMC3952802 DOI: 10.1111/bph.12528] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 10/21/2013] [Accepted: 11/06/2013] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Depletion of the Ca(2+) store by ryanodine receptor (RyR) agonists induces store-operated Ca(2+) entry (SOCE). 4-Chloro-3-ethylphenol (4-CEP) and 4-chloro-m-cresol (4-CmC) are RyR agonists commonly used as research tools and diagnostic reagents for malignant hyperthermia. Here, we investigated the effects of 4-CEP and its analogues on SOCE. EXPERIMENTAL APPROACH SOCE and ORAI1-3 currents were recorded by Ca(2+) imaging and whole-cell patch recordings in rat L6 myoblasts and in HEK293 cells overexpressing STIM1/ORAI1-3. KEY RESULTS 4-CEP induced a significant release of Ca(2+) in rat L6 myoblasts, but inhibited SOCE. The inhibitory effect was concentration-dependent and more potent than its analogues 4-CmC and 4-chlorophenol (4-ClP). In the HEK293 T-REx cells overexpressing STIM1/ORAI1-3, 4-CEP inhibited the ORAI1, ORAI2 and ORAI3 currents evoked by thapsigargin. The 2-APB-induced ORAI3 current was also blocked by 4-CEP. This inhibitory effect was reversible and independent of the Ca(2+) release. The two analogues, 4-CmC and 4-ClP, also inhibited the ORAI1-3 channels. Excised patch and intracellular application of 4-CEP demonstrated that the action site was located extracellularly. Moreover, 4-CEP evoked STIM1 translocation and subplasmalemmal clustering through its Ca(2+) store-depleting effect via the activation of RyR, but no effect on STIM1 redistribution was observed in cells co-expressing STIM1/ORAI1-3. CONCLUSION AND IMPLICATIONS 4-CEP not only acts as a RyR agonist to deplete the Ca(2+) store and trigger STIM1 subplasmalemmal translocation and clustering, but also directly inhibits ORAI1-3 channels. These findings demonstrate a novel pharmacological property for the chlorophenol derivatives that act as RyR agonists.
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Affiliation(s)
- Bo Zeng
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of HullHull, UK
| | - Gui-Lan Chen
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of HullHull, UK
- Key Laboratory for Medical Electrophysiology, Ministry of Education of China, and the Institute of Cardiovascular Research, Luzhou Medical CollegeLuzhou, China
| | - Nikoleta Daskoulidou
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of HullHull, UK
| | - Shang-Zhong Xu
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of HullHull, UK
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8
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Ye Y, Yaeger D, Owen LJ, Escobedo JO, Wang J, Singer JD, Strongin RM, Abramson JJ. Designing calcium release channel inhibitors with enhanced electron donor properties: stabilizing the closed state of ryanodine receptor type 1. Mol Pharmacol 2011; 81:53-62. [PMID: 21989257 DOI: 10.1124/mol.111.074740] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
New drugs with enhanced electron donor properties that target the ryanodine receptor from skeletal muscle sarcoplasmic reticulum (RyR1) are shown to be potent inhibitors of single-channel activity. In this article, we synthesize derivatives of the channel activator 4-chloro-3-methyl phenol (4-CmC) and the 1,4-benzothiazepine channel inhibitor 4-[-3{1-(4-benzyl) piperidinyl}propionyl]-7-methoxy-2,3,4,5-tetrahydro-1,4-benzothiazepine (K201, JTV519) with enhanced electron donor properties. Instead of activating channel activity (~100 μM), the 4-methoxy analog of 4-CmC [4-methoxy-3-methyl phenol (4-MmC)] inhibits channel activity at submicromolar concentrations (IC(50) = 0.34 ± 0.08 μM). Increasing the electron donor characteristics of K201 by synthesizing its dioxole congener results in an approximately 16 times more potent RyR1 inhibitor (IC(50) = 0.24 ± 0.05 μM) compared with K201 (IC(50) = 3.98 ± 0.79 μM). Inhibition is not caused by an increased closed time of the channel but seems to be caused by an open state block of RyR1. These alterations to chemical structure do not influence the ability of these drugs to affect Ca(2+)-dependent ATPase activity of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase type 1. Moreover, the FKBP12 protein, which stabilizes RyR1 in a closed configuration, is shown to be a strong electron donor. It seems as if FKBP12, K201, its dioxole derivative, and 4-MmC inhibit RyR1 channel activity by virtue of their electron donor characteristics. These results embody strong evidence that designing new drugs to target RyR1 with enhanced electron donor characteristics results in more potent channel inhibitors. This is a novel approach to the design of new, more potent drugs with the aim of functionally modifying RyR1 single-channel activity.
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Affiliation(s)
- Yanping Ye
- Department of Physics, Portland State University, Portland, Oregon 97207, USA
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9
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Feng W, Cherednichenko G, Ward CW, Padilla IT, Cabrales E, Lopez JR, Eltit JM, Allen PD, Pessah IN. Green tea catechins are potent sensitizers of ryanodine receptor type 1 (RyR1). Biochem Pharmacol 2010; 80:512-21. [PMID: 20471964 PMCID: PMC2907350 DOI: 10.1016/j.bcp.2010.05.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 05/04/2010] [Accepted: 05/07/2010] [Indexed: 01/26/2023]
Abstract
Catechins, polyphenols extracted from green tea leaves, have a broad range of biological activities although the specific molecular mechanisms responsible are not known. At the high experimental concentrations typically used polyphenols bind to membrane phospholipid and also are easily auto-oxidized to generate superoxide anion and semiquinones, and can adduct to protein thiols. We report that the type 1 ryanodine receptor (RyR1) is a molecular target that responds to nanomolar (-)-epigallocatechin-3-gallate (EGCG) and (-)-epicatechin-3-gallate (ECG). Single channel analyses demonstrate EGCG (5-10nM) increases channel open probability (Po) twofold, by lengthening open dwell time. The degree of channel activation is concentration-dependent and is rapidly and fully reversible. Four related catechins, EGCG, ECG, EGC ((-)-epigallocatechin) and EC ((-)-epicatechin) showed a rank order of activity toward RyR1 (EGCG>ECG>>EGC>>>EC). EGCG and ECG enhance the sensitivity of RyR1 to activation by < or =100microM cytoplasmic Ca(2+) without altering inhibitory potency by >100microM Ca(2+). EGCG as high as 10microM in the extracellular medium potentiated Ca(2+) transient amplitudes evoked by electrical stimuli applied to intact myotubes and adult FDB fibers, without eliciting spontaneous Ca(2+) release or slowing Ca(2+) transient recovery. The results identify RyR1 as a sensitive target for the major tea catechins EGCG and ECG, and this interaction is likely to contribute to their observed biological activities.
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Affiliation(s)
- Wei Feng
- Department of Molecular Biosciences, University of California, Davis, 95616, United States of America.
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10
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Suzuki D, Hori T, Saitoh N, Takahashi T. 4-Chloro-m-cresol, an activator of ryanodine receptors, inhibits voltage-gated K(+) channels at the rat calyx of Held. Eur J Neurosci 2007; 26:1530-6. [PMID: 17714495 DOI: 10.1111/j.1460-9568.2007.05762.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
4-Chloro-m-cresol (4-CmC) is thought to be a specific activator of ryanodine receptors (RyRs). Using this compound, we examined whether the RyR-mediated Ca(2+) release is involved in transmitter release at the rat calyx of Held synapse in brainstem slices. Bath application of 4-CmC caused a dramatic increase in the amplitude of excitatory postsynaptic currents (TIFCs) with the half-maximal effective concentration of 0.12 mm. By making direct patch-clamp whole-cell recordings from presynaptic terminals, we investigated the mechanism by which 4-CmC facilitates transmitter release. 4-CmC markedly prolonged the duration of action potentials, with little effect on their rise time kinetics. In voltage-clamp recordings, 4-CmC inhibited voltage-gated presynaptic K(+) currents (I(pK)) by 53% (at +20 mV) but had no effect on voltage-gated presynaptic Ca(2+) currents (I(pCa)). In simultaneous pre- and postsynaptic recordings, 4-CmC had no effect on the TIFC evoked by I(pCa). Although immunocytochemical study of the calyceal terminals showed immunoreactivity to type 3 RyRs, ryanodine (0.02 mm) had no effect on the 4-CmC-induced TIFC potentiation. We conclude that the facilitatory effect of 4-CmC on nerve-evoked transmitter release is mediated by its inhibitory effect on I(pK).
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Affiliation(s)
- Daisuke Suzuki
- Department of Neurophysiology, University of Tokyo Graduate School of Medicine, Tokyo, Japan
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