1
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Spahiu E, Kastrati E, Amrute-Nayak M. PyChelator: a Python-based Colab and web application for metal chelator calculations. BMC Bioinformatics 2024; 25:239. [PMID: 39014298 PMCID: PMC11253343 DOI: 10.1186/s12859-024-05858-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Accepted: 07/09/2024] [Indexed: 07/18/2024] Open
Abstract
BACKGROUND Metal ions play vital roles in regulating various biological systems, making it essential to control the concentration of free metal ions in solutions during experimental procedures. Several software applications exist for estimating the concentration of free metals in the presence of chelators, with MaxChelator being the easily accessible choice in this domain. This work aimed at developing a Python version of the software with arbitrary precision calculations, extensive new features, and a user-friendly interface to calculate the free metal ions. RESULTS We introduce the open-source PyChelator web application and the Python-based Google Colaboratory notebook, PyChelator Colab. Key features aim to improve the user experience of metal chelator calculations including input in smaller units, selection among stability constants, input of user-defined constants, and convenient download of all results in Excel format. These features were implemented in Python language by employing Google Colab, facilitating the incorporation of the calculator into other Python-based pipelines and inviting the contributions from the community of Python-using scientists for further enhancements. Arbitrary-precision arithmetic was employed by using the built-in Decimal module to obtain the most accurate results and to avoid rounding errors. No notable differences were observed compared to the results obtained from the PyChelator web application. However, comparison of different sources of stability constants showed substantial differences among them. CONCLUSIONS PyChelator is a user-friendly metal and chelator calculator that provides a platform for further development. It is provided as an interactive web application, freely available for use at https://amrutelab.github.io/PyChelator , and as a Python-based Google Colaboratory notebook at https://colab. RESEARCH google.com/github/AmruteLab/PyChelator/blob/main/PyChelator_Colab.ipynb .
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Affiliation(s)
- Emrulla Spahiu
- Institute of Molecular and Cell Physiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
| | - Esra Kastrati
- Lassonde School of Engineering, York University, Toronto, M3J 1P3, Canada
| | - Mamta Amrute-Nayak
- Institute of Molecular and Cell Physiology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany.
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2
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Dowrick JM, Taberner AJ, Han JC, Tran K. Methods for assessing cardiac myofilament calcium sensitivity. Front Physiol 2023; 14:1323768. [PMID: 38116581 PMCID: PMC10728676 DOI: 10.3389/fphys.2023.1323768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 11/23/2023] [Indexed: 12/21/2023] Open
Abstract
Myofilament calcium (Ca2+) sensitivity is one of several mechanisms by which force production of cardiac muscle is modulated to meet the ever-changing demands placed on the heart. Compromised Ca2+ sensitivity is associated with pathologies, which makes it a parameter of interest for researchers. Ca2+ Sensitivity is the ratio of the association and dissociation rates between troponin C (TnC) and Ca2+. As it is not currently possible to measure these rates in tissue preparations directly, methods have been developed to infer myofilament sensitivity, typically using some combination of force and Ca2+ measurements. The current gold-standard approach constructs a steady-state force-Ca2+ relation by exposing permeabilised muscle samples to a range of Ca2+ concentrations and uses the half-maximal concentration as a proxy for sensitivity. While a valuable method for steady-state investigations, the permeabilisation process makes the method unsuitable when examining dynamic, i.e., twitch-to-twitch, changes in myofilament sensitivity. The ability of the heart to transiently adapt to changes in load is an important consideration when evaluating the impact of disease states. Alternative methods have been proffered, including force-Ca2+ phase loops, potassium contracture, hybrid experimental-modelling and conformation-based fluorophore approaches. This review provides an overview of the mechanisms underlying myofilament Ca2+ sensitivity, summarises existing methods, and explores, with modelling, whether any of them are suited to investigating dynamic changes in sensitivity. We conclude that a method that equips researchers to investigate the transient change of myofilament Ca2+ sensitivity is still needed. We propose that such a method will involve simultaneous measurements of cytosolic Ca2+ and TnC activation in actively twitching muscle and a biophysical model to interpret these data.
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Affiliation(s)
- Jarrah M. Dowrick
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Andrew J. Taberner
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Department of Engineering Science and Biomedical Engineering, University of Auckland, Auckland, New Zealand
| | - June-Chiew Han
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Kenneth Tran
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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3
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Feng W, Lopez JR, Antrobus S, Zheng J, Uryash A, Dong Y, Beqollari D, Bannister RA, Hopkins PM, Beam KG, Allen PD, Pessah IN. Putative malignant hyperthermia mutation Ca V1.1-R174W is insufficient to trigger a fulminant response to halothane or confer heat stress intolerance. J Biol Chem 2023; 299:104992. [PMID: 37392848 PMCID: PMC10413282 DOI: 10.1016/j.jbc.2023.104992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/16/2023] [Accepted: 06/20/2023] [Indexed: 07/03/2023] Open
Abstract
Malignant hyperthermia susceptibility (MHS) is an autosomal dominant pharmacogenetic disorder that manifests as a hypermetabolic state when carriers are exposed to halogenated volatile anesthetics or depolarizing muscle relaxants. In animals, heat stress intolerance is also observed. MHS is linked to over 40 variants in RYR1 that are classified as pathogenic for diagnostic purposes. More recently, a few rare variants linked to the MHS phenotype have been reported in CACNA1S, which encodes the voltage-activated Ca2+ channel CaV1.1 that conformationally couples to RyR1 in skeletal muscle. Here, we describe a knock-in mouse line that expresses one of these putative variants, CaV1.1-R174W. Heterozygous (HET) and homozygous (HOM) CaV1.1-R174W mice survive to adulthood without overt phenotype but fail to trigger with fulminant malignant hyperthermia when exposed to halothane or moderate heat stress. All three genotypes (WT, HET, and HOM) express similar levels of CaV1.1 by quantitative PCR, Western blot, [3H]PN200-110 receptor binding and immobilization-resistant charge movement densities in flexor digitorum brevis fibers. Although HOM fibers have negligible CaV1.1 current amplitudes, HET fibers have similar amplitudes to WT, suggesting a preferential accumulation of the CaV1.1-WT protein at triad junctions in HET animals. Never-the-less both HET and HOM have slightly elevated resting free Ca2+ and Na+ measured with double barreled microelectrode in vastus lateralis that is disproportional to upregulation of transient receptor potential canonical (TRPC) 3 and TRPC6 in skeletal muscle. CaV1.1-R174W and upregulation of TRPC3/6 alone are insufficient to trigger fulminant malignant hyperthermia response to halothane and/or heat stress in HET and HOM mice.
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Affiliation(s)
- Wei Feng
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA
| | - Jose R Lopez
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA; Department of Research, Mount Sinai Medical Center, Miami Beach, Florida, USA
| | - Shane Antrobus
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA
| | - Jing Zheng
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA
| | - Arkady Uryash
- Department of Research, Mount Sinai Medical Center, Miami Beach, Florida, USA
| | - Yao Dong
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA
| | - Donald Beqollari
- Department of Medicine-Cardiology Division, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Roger A Bannister
- Department of Medicine-Cardiology Division, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Philip M Hopkins
- Institute of Medical Research at St James's, University of Leeds, Leeds, United Kingdom
| | - Kurt G Beam
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Paul D Allen
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA; Institute of Medical Research at St James's, University of Leeds, Leeds, United Kingdom
| | - Isaac N Pessah
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA.
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4
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Merve D, Irfan A, Tugba DKN, Inci SE. Determination of the roles of cADPR and NAADP as intracellular calcium mobilizing messengers in S1P-induced contractions in rat bladders having IC/PBS. Life Sci 2023; 322:121651. [PMID: 37023954 DOI: 10.1016/j.lfs.2023.121651] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 03/28/2023] [Accepted: 03/28/2023] [Indexed: 04/08/2023]
Abstract
AIMS Interstitial cystitis/painful bladder syndrome (IC/PBS) is characterized by lower abdominal pain and increased frequency and urgency of urine. Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid that plays role in calcium homeostasis in smooth muscle. The intracellular calcium mobilizing secondary messengers are also involved in smooth muscle contraction. The role of intracellular calcium storing depots in S1P-induced contraction was investigated in permeabilized detrusor smooth muscle having cystitis. MAIN METHODS IC/PBS was induced by cyclophosphamide injection. The detrusor smooth muscle strips isolated from rats were permeabilized with β-escin. KEY FINDINGS S1P-induced contraction was increased in cystitis. S1P-induced enhanced contraction was inhibited by cyclopiazonic acid, ryanodine and heparin showing involvement of sarcoplasmic reticulum (SR) calcium stores. Inhibition of S1P-induced contraction by bafilomycin and NAADP suggested the participation of lysosome-related organelles. SIGNIFICANCE IC/PBS triggers S1P-induced increase in intracellular calcium from SR and lysosome-related organelles in permeabilized detrusor smooth muscle.
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Affiliation(s)
- Denizalti Merve
- Faculty of Pharmacy, Department of Pharmacology, Hacettepe University, Ankara, Turkey
| | - Anjum Irfan
- Faculty of Pharmacy, Department of Pharmacology, Hacettepe University, Ankara, Turkey
| | | | - Sahin-Erdemli Inci
- Faculty of Pharmacy, Department of Pharmacology, Hacettepe University, Ankara, Turkey
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5
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Merve D, Irfan A, Gul S, Celik OS, Tugba DKN. Trypsin-induced elevated contractile responses in a rat model of interstitial cystitis/bladder pain syndrome: Involvement of PAR2 and intracellular Ca 2+ release pathways. Life Sci 2022; 293:120359. [PMID: 35092732 DOI: 10.1016/j.lfs.2022.120359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 01/16/2022] [Accepted: 01/24/2022] [Indexed: 11/25/2022]
Abstract
AIMS Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic inflammatory disease with unclear etiology. Different receptors play a role in the pathophysiology including protease activated receptors (PARs). The present study aimed to investigate the subtypes and the effects of PARs on contractility using permeabilized detrusor smooth muscle strips in IC/BPS. MAIN METHODS IC/BPS was induced by cyclophosphamide injection. Histopathological analysis, PCR for detecting PAR proteins, western blotting for indicating PAR2 protein expression levels and myograph recording for measuring contractile force were used. KEY FINDINGS The present study reveals that in rat bladder PAR1 and PAR2 but not PAR4 were found to be expressed. The first evidence was revealed where trypsin-induced contractions in rat permeabilized detrusor were potentiated in CYP-induced cystitis. Moreover, the functional inhibition of trypsin-induced contractions by selective PAR2 antagonist (ENMD-1068) and the supporting immunoblotting results emphasized that the main PAR subtype involved in IC/BPS model in rat bladder is PAR2. Our data emphasize the prominent role of IP3 in cystitis pathology besides ryanodine channels. Trypsin-induced Ca2+sensitization contractions were also higher in cystitis. Both Rho kinase and protein kinase C played a role in this increased Ca2+sensitization situation. SIGNIFICANCE The present paper highlights the intracellular pathways that are involved in trypsin-induced contractions mainly via PAR2 in permeabilized bladder detrusor smooth muscle in a rat model of IC/BPS.
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Affiliation(s)
- Denizalti Merve
- Faculty of Pharmacy, Department of Pharmacology, Hacettepe University, Ankara, Turkey
| | - Anjum Irfan
- Faculty of Pharmacy, Department of Pharmacology, Hacettepe University, Ankara, Turkey
| | - Simsek Gul
- Faculty of Medicine, Department of Biophysics, Ankara University, Ankara, Turkey
| | - Onder Sevgen Celik
- Faculty of Medicine, Department of Pathology, Hacettepe University, Ankara, Turkey
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6
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Kampfer AJ, Balog EM. Electrical polarity-dependent gating and a unique subconductance of RyR2 induced by S-adenosyl methionine via the ATP binding site. J Biochem 2021; 170:739-752. [PMID: 34523682 DOI: 10.1093/jb/mvab093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 08/30/2021] [Indexed: 11/14/2022] Open
Abstract
S-Adenosyl-l-methionine (SAM) was used to probe the functional effects exerted via the RyR2 adenine nucleotide binding site. Single channel experiments revealed that SAM applied to the cytoplasmic face of RyR2 had complex voltage dependent effects on channel gating and conductance. At positive transmembrane holding potentials, SAM caused a striking reduction in channel openings and a reduced channel conductance. In contrast, at negative potentials SAM promoted a clearly resolved subconductance state. At membrane potentials between -75 and -25 mV the open probability of the subconductance state was independent of voltage. ATP, but not the non-adenosine based RyR activator 4-chloro-m-cresol interfered with the effects of SAM at both negative and positive potentials. This suggests that ATP and SAM interact with a common binding site. Molecular docking showed SAM bound to the adenine nucleotide-binding site and formed a hydrogen bond to Glu4886 in the C-terminal end of the S6 alpha helix. In this configuration SAM may alter the conformation of the RyR2 ion conduction pathway. This work provides novel insight into potential functional outcomes of ligand binding to the RyR adenine nucleotide binding site.
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Affiliation(s)
- Angela J Kampfer
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Edward M Balog
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332
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7
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Rinaldi DE, Ontiveros MQ, Saffioti NA, Vigil MA, Mangialavori IC, Rossi RC, Rossi JP, Espelt MV, Ferreira-Gomes MS. Epigallocatechin 3-gallate inhibits the plasma membrane Ca 2+-ATPase: effects on calcium homeostasis. Heliyon 2021; 7:e06337. [PMID: 33681501 PMCID: PMC7930289 DOI: 10.1016/j.heliyon.2021.e06337] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 01/16/2021] [Accepted: 02/17/2021] [Indexed: 12/27/2022] Open
Abstract
Flavonoids are natural compounds responsible for the health benefits of green tea. Some of the flavonoids present in green tea are catechins, among which are: epigallocatechin, epicatechin-3-gallate, epicatechin, catechin and epigallocatechin-3-gallate (EGCG). The latter was found to induce apoptosis, reduce reactive oxygen species, in some conditions though in others it acts as an oxidizing agent, induce cell cycle arrest, and inhibit carcinogenesis. EGCG also was found to be involved in calcium (Ca2+) homeostasis in excitable and in non-excitable cells. In this study, we investigate the effect of catechins on plasma membrane Ca2+-ATPase (PMCA), which is one of the main mechanisms that extrude Ca2+ out of the cell. Our studies comprised experiments on the isolated PMCA and on cells overexpressing the pump. Among catechins that inhibited PMCA activity, the most potent inhibitor was EGCG. EGCG inhibited PMCA activity in a reversible way favoring E1P conformation. EGCG inhibition also occurred in the presence of calmodulin, the main pump activator. Finally, the effect of EGCG on PMCA activity was studied in human embryonic kidney cells (HEK293T) that transiently overexpress hPMCA4. Results show that EGCG inhibited PMCA activity in HEK293T cells, suggesting that the effects observed on isolated PMCA occur in living cells.
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Affiliation(s)
| | | | - Nicolas A. Saffioti
- IQUIFIB – Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956, 1113 Buenos Aires, Argentina
| | - Maximiliano A. Vigil
- IQUIFIB – Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956, 1113 Buenos Aires, Argentina
| | - Irene C. Mangialavori
- IQUIFIB – Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956, 1113 Buenos Aires, Argentina
| | - Rolando C. Rossi
- IQUIFIB – Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956, 1113 Buenos Aires, Argentina
| | - Juan P. Rossi
- IQUIFIB – Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956, 1113 Buenos Aires, Argentina
| | - María V. Espelt
- IQUIFIB – Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956, 1113 Buenos Aires, Argentina
| | - Mariela S. Ferreira-Gomes
- IQUIFIB – Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956, 1113 Buenos Aires, Argentina
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8
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Le Guilcher C, Luyten T, Parys JB, Pucheault M, Dellis O. Synthesis and Characterization of Store-Operated Calcium Entry Inhibitors Active in the Submicromolar Range. Int J Mol Sci 2020; 21:ijms21249777. [PMID: 33371518 PMCID: PMC7767506 DOI: 10.3390/ijms21249777] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 12/09/2020] [Accepted: 12/18/2020] [Indexed: 12/13/2022] Open
Abstract
The store-operated calcium entry, better known as SOCE, forms the main Ca2+ influx pathway in non-excitable cells, especially in leukocytes, where it is required for cell activation and the immune response. During the past decades, several inhibitors were developed, but they lack specificity or efficacy. From the non-specific SOCE inhibitor 2-aminoethyl diphenylborinate (2-APB), we synthetized 16 new analogues by replacing/modifying the phenyl groups. Among them, our compound P11 showed the best inhibitory capacity with a Ki ≈ 75 nM. Furthermore, below 1 µM, P11 was devoid of any inhibitory activity on the two other main cellular targets of 2-APB, the IP3 receptors, and the SERCA pumps. Interestingly, Jurkat T cells secrete interleukin-2 under phytohemagglutinin stimulation but undergo cell death and stop IL-2 synthesis when stimulated in the presence of increasing P11 concentrations. Thus, P11 could represent the first member of a new and potent family of immunosuppressors.
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Affiliation(s)
- Camille Le Guilcher
- Physiopathogénèse et Traitements des Maladies du Foie, Université Paris-Saclay, Rue des Adeles, 91405 Orsay, France;
- INSERM U1193, Rue des Adeles, 91405 Orsay, France
| | - Tomas Luyten
- Laboratory for Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine & Leuven Kanker Instituut, B-3000 Leuven, Belgium; (T.L.); (J.B.P.)
| | - Jan B. Parys
- Laboratory for Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine & Leuven Kanker Instituut, B-3000 Leuven, Belgium; (T.L.); (J.B.P.)
| | - Mathieu Pucheault
- Institute of Molecular Science, CNRS, Université de Bordeaux, 33400 Talence, France;
| | - Olivier Dellis
- Physiopathogénèse et Traitements des Maladies du Foie, Université Paris-Saclay, Rue des Adeles, 91405 Orsay, France;
- INSERM U1193, Rue des Adeles, 91405 Orsay, France
- Correspondence: ; Tel.: +33-169-154-959
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9
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Aleman M, Zhang R, Feng W, Qi L, Lopez JR, Crowe C, Dong Y, Cherednichenko G, Pessah IN. Dietary Caffeine Synergizes Adverse Peripheral and Central Responses to Anesthesia in Malignant Hyperthermia Susceptible Mice. Mol Pharmacol 2020; 98:351-363. [PMID: 32764093 DOI: 10.1124/mol.120.119412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 07/31/2020] [Indexed: 11/22/2022] Open
Abstract
Ryanodine receptor (RYR) mutations confer stress-triggered malignant hyperthermia (MH) susceptibility. Dietary caffeine (CAF) is the most commonly consumed psychoactive compound by humans. CAF-triggered Ca2+ release and its influences on skeletal muscle contractility are widely used as experimental tools to study RYR function/dysfunction and diagnose MH susceptibility. We hypothesize that dietary CAF achieving blood levels measured in human plasma exacerbates the penetrance of RYR1 MH susceptibility mutations triggered by gaseous anesthetic, affecting both central and peripheral adverse responses. Heterozygous R163C-RYR1 (HET) MH susceptible mice are used to investigate the influences of dietary CAF on both peripheral and central responses before and after induction of halothane (HAL) maintenance anesthesia under experimental conditions that maintain normal core body temperature. HET mice receiving CAF (plasma CAF 893 ng/ml) have significantly shorter times to respiratory arrest compared with wild type, without altering blood chemistry or displaying hyperthermia or muscle rigor. Intraperitoneal bolus dantrolene before HAL prolongs time to respiratory arrest. A pilot electrographic study using subcutaneous electrodes reveals that dietary CAF does not alter baseline electroencephalogram (EEG) total power, but significantly shortens delay to isoelectric EEG, which precedes respiratory and cardiac arrest. CAF ± HAL are studied on RYR1 single-channel currents and HET myotubes to define molecular mechanisms of gene-by-environment synergism. Strong pharmacological synergism between CAF and HAL is demonstrated in both single-channel and myotube preparations. Central and peripheral nervous systems mediate adverse responses to HAL in a HET model of MH susceptibility exposed to dietary CAF, a modifiable lifestyle factor that may mitigate risks of acute and chronic diseases associated with RYR1 mutations. SIGNIFICANCE STATEMENT: Dietary caffeine at a human-relevant dose synergizes adverse peripheral and central responses to anesthesia in malignant hyperthermia susceptible mice. Synergism of these drugs can be attributed to their actions at ryanodine receptors.
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Affiliation(s)
- Monica Aleman
- Department of Molecular Biosciences, School of Veterinary Medicine (R.Z., W.F., J.R.L., Y.D., G.C., I.N.P.), Department of Medicine and Epidemiology, The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine (M.A., C.C.), and Department of Public Health Sciences, School of Medicine, School of Medicine (L.Q.), University of California, Davis, California
| | - Rui Zhang
- Department of Molecular Biosciences, School of Veterinary Medicine (R.Z., W.F., J.R.L., Y.D., G.C., I.N.P.), Department of Medicine and Epidemiology, The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine (M.A., C.C.), and Department of Public Health Sciences, School of Medicine, School of Medicine (L.Q.), University of California, Davis, California
| | - Wei Feng
- Department of Molecular Biosciences, School of Veterinary Medicine (R.Z., W.F., J.R.L., Y.D., G.C., I.N.P.), Department of Medicine and Epidemiology, The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine (M.A., C.C.), and Department of Public Health Sciences, School of Medicine, School of Medicine (L.Q.), University of California, Davis, California
| | - Lihong Qi
- Department of Molecular Biosciences, School of Veterinary Medicine (R.Z., W.F., J.R.L., Y.D., G.C., I.N.P.), Department of Medicine and Epidemiology, The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine (M.A., C.C.), and Department of Public Health Sciences, School of Medicine, School of Medicine (L.Q.), University of California, Davis, California
| | - Jose R Lopez
- Department of Molecular Biosciences, School of Veterinary Medicine (R.Z., W.F., J.R.L., Y.D., G.C., I.N.P.), Department of Medicine and Epidemiology, The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine (M.A., C.C.), and Department of Public Health Sciences, School of Medicine, School of Medicine (L.Q.), University of California, Davis, California
| | - Chelsea Crowe
- Department of Molecular Biosciences, School of Veterinary Medicine (R.Z., W.F., J.R.L., Y.D., G.C., I.N.P.), Department of Medicine and Epidemiology, The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine (M.A., C.C.), and Department of Public Health Sciences, School of Medicine, School of Medicine (L.Q.), University of California, Davis, California
| | - Yao Dong
- Department of Molecular Biosciences, School of Veterinary Medicine (R.Z., W.F., J.R.L., Y.D., G.C., I.N.P.), Department of Medicine and Epidemiology, The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine (M.A., C.C.), and Department of Public Health Sciences, School of Medicine, School of Medicine (L.Q.), University of California, Davis, California
| | - Genady Cherednichenko
- Department of Molecular Biosciences, School of Veterinary Medicine (R.Z., W.F., J.R.L., Y.D., G.C., I.N.P.), Department of Medicine and Epidemiology, The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine (M.A., C.C.), and Department of Public Health Sciences, School of Medicine, School of Medicine (L.Q.), University of California, Davis, California
| | - Isaac N Pessah
- Department of Molecular Biosciences, School of Veterinary Medicine (R.Z., W.F., J.R.L., Y.D., G.C., I.N.P.), Department of Medicine and Epidemiology, The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine (M.A., C.C.), and Department of Public Health Sciences, School of Medicine, School of Medicine (L.Q.), University of California, Davis, California
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10
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McGuigan JAS, Kay JW, Elder HY. Ionized concentrations in Ca 2+ and Mg 2+ buffers must be measured, not calculated. Exp Physiol 2019; 105:427-437. [PMID: 31758871 DOI: 10.1113/ep088345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 11/22/2019] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the topic of this review? The [Ca2+ ]/[Mg2+ ] in buffers are usually calculated using one of eight programs. These all give different values, thus [Ca2+ ]/[Mg2+ ] must be measured. What advances does it highlight? The ligand optimization method (LOM) using electrodes is an accurate method to do this. The limitations of the method are described. The LOM has been generalized to include calibration of fluorochromes and aequorin. It is the method of choice to measure intracellular equilibrium constants. Owing to the uncertainties for the values of resting [Ca2+ ], ∆[Ca2+ ] and the pK' values for intracellular Ca2+ /Mg2+ binding used in modelling, these values must now be re-examined critically. ABSTRACT Modelling intracellular regulation of Ca2+ /Mg2+ is now an established part of physiology. However, the conclusions drawn from such studies depend on accurate knowledge of intracellular [Ca2+ ], ∆[Ca2+ ] and the pK' values for the intracellular binding of Ca2+ /Mg2+ . Calculation of [Ca2+ ]/[Mg2+ ] in buffers is normal. The eight freely available programs all give different values for the [Ca2+ ]/[Mg2+ ] in the buffer solutions, varying by up to a factor of 4.3. As a result, concentrations must be measured. There are two methods to do this, both based on the ligand optimization method (LOM): (1) calibration solutions from 0.5 to 4 mmol l-1 ; and (2) calibration solutions from 0.1 µmol l-1 to 2 mmol l-1 . Both methods can be used to calibrate Ca2+ /Mg2+ electrodes. Only Method 2 can be used directly to calibrate fluorochromes and aequorin. Software in the statistical program R to calculate the [Ca2+ ]/[Mg2+ ] in buffers is provided for both methods. The LOM has now been generalized for use with electrodes, fluorochromes and aequorin, making it the ideal method to determine the pK' values for intracellular binding of Ca2+ /Mg2+ . The [Ca2+ ]/[Mg2+ ] in buffers must be measured routinely, which is best done by calibrating electrodes with the LOM and software written in R. If [Ca2+ ]/[Mg2+ ] in buffers are calculated, the parameters used in modelling show the same degree of variability as the software programs. Uncritical acceptance of such parameters means that conclusions reached from such studies are relative, not absolute, and must now be re-examined.
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Affiliation(s)
| | - James W Kay
- School of Mathematics and Statistics, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Hugh Y Elder
- School of Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
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11
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Zheng J, Yu Y, Feng W, Li J, Liu J, Zhang C, Dong Y, Pessah IN, Cao Z. Influence of Nanomolar Deltamethrin on the Hallmarks of Primary Cultured Cortical Neuronal Network and the Role of Ryanodine Receptors. ENVIRONMENTAL HEALTH PERSPECTIVES 2019; 127:67003. [PMID: 31166131 PMCID: PMC6792378 DOI: 10.1289/ehp4583] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 05/09/2019] [Accepted: 05/10/2019] [Indexed: 05/19/2023]
Abstract
BACKGROUND The pyrethroid deltamethrin (DM) is broadly used for insect control. Although DM hyperexcites neuronal networks by delaying inactivation of axonal voltage-dependent [Formula: see text] channels, this mechanism is unlikely to mediate neurotoxicity at lower exposure levels during critical perinatal periods in mammals. OBJECTIVES We aimed to identify mechanisms by which acute and subchronic DM altered axonal and dendritic growth, patterns of synchronous [Formula: see text] oscillations (SCOs), and electrical spike activity (ESA) functions critical to neuronal network formation. METHODS Measurements of SCOs using [Formula: see text] imaging, ESA using microelectrode array (MEA) technology, and dendritic complexity using Sholl analysis were performed in primary murine cortical neurons from wild-type (WT) and/or ryanodine receptor 1 ([Formula: see text]) mice between 5 and 14 d in vitro (DIV). [Formula: see text] binding analysis and a single-channel voltage clamp were utilized to measure engagement of RyRs as a direct target of DM. RESULTS Neuronal networks responded to DM ([Formula: see text]) as early as 5 DIV, reducing SCO amplitude and depressing ESA and burst frequencies by 60-70%. DM ([Formula: see text]) enhanced axonal growth in a nonmonotonic manner. [Formula: see text] enhanced dendritic complexity. DM stabilized channel open states of RyR1, RyR2, and cortical preparations expressing all three isoforms. DM ([Formula: see text]) altered gating kinetics of RyR1 channels, increasing mean open time, decreasing mean closed time, and thereby enhancing overall open probability. SCO patterns from cortical networks expressing [Formula: see text] were more responsive to DM than WT. [Formula: see text] neurons showed inherently longer axonal lengths than WT neurons and maintained less length-promoting responses to nanomolar DM. CONCLUSIONS Our findings suggested that RyRs were sensitive molecular targets of DM with functional consequences likely relevant for mediating abnormal neuronal network connectivity in vitro. https://doi.org/10.1289/EHP4583.
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Affiliation(s)
- Jing Zheng
- State Key Laboratory of Natural Medicines, Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Research, Department of TCM Pharmacology, School of Traditional Pharmacy, China Pharmaceutical University, Nanjing, China
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Yiyi Yu
- State Key Laboratory of Natural Medicines, Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Research, Department of TCM Pharmacology, School of Traditional Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Wei Feng
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Jing Li
- State Key Laboratory of Natural Medicines, Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Research, Department of TCM Pharmacology, School of Traditional Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Ju Liu
- State Key Laboratory of Natural Medicines, Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Research, Department of TCM Pharmacology, School of Traditional Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Chunlei Zhang
- State Key Laboratory of Natural Medicines, Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Research, Department of TCM Pharmacology, School of Traditional Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Yao Dong
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Isaac N. Pessah
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Zhengyu Cao
- State Key Laboratory of Natural Medicines, Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Research, Department of TCM Pharmacology, School of Traditional Pharmacy, China Pharmaceutical University, Nanjing, China
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12
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Ontiveros M, Rinaldi D, Marder M, Espelt MV, Mangialavori I, Vigil M, Rossi JP, Ferreira-Gomes M. Natural flavonoids inhibit the plasma membrane Ca 2+-ATPase. Biochem Pharmacol 2019; 166:1-11. [PMID: 31071329 DOI: 10.1016/j.bcp.2019.05.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 05/03/2019] [Indexed: 11/25/2022]
Abstract
Research on flavonoids from plant sources has recently sparked increasing interest because of their beneficial health properties. Different studies have shown that flavonoids change the intracellular Ca2+ homeostasis linked to alterations in the function of mitochondria, Ca2+ channels and Ca2+ pumps. These findings hint at plasma membrane Ca2+-ATPase (PMCA) involvement, as it transports Ca2+ actively to the extracellular medium coupled to ATP hydrolysis, thus maintaining ion cellular homeostasis. The present study aims to investigate the effect of several natural flavonoids on PMCA both in isolated protein systems and in living cells, and to establish the relationship between flavonoid structure and inhibitory activity on PMCA. Our results show that natural flavonoids inhibited purified and membranous PMCA with different effectiveness: quercetin and gossypin were the most potent and their inhibition mechanisms seem to be different, as quercetin does not prevent ATP binding whereas gossypin does. Moreover, PMCA activity was inhibited in human embryonic kidney cells which transiently overexpress PMCA, suggesting that the effects observed on isolated systems could occur in a complex structure like a living cell. In conclusion, this work reveals a novel molecular mechanism through which flavonoids inhibit PMCA, which leads to Ca2+ homeostasis and signaling alterations in the cell.
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Affiliation(s)
- M Ontiveros
- IQUIFIB - Instituto de Química y Fisicoquímica Biológicas, Conicet/UBA, Junín 956 (1113) Buenos Aires, Argentina
| | - D Rinaldi
- IQUIFIB - Instituto de Química y Fisicoquímica Biológicas, Conicet/UBA, Junín 956 (1113) Buenos Aires, Argentina
| | - M Marder
- IQUIFIB - Instituto de Química y Fisicoquímica Biológicas, Conicet/UBA, Junín 956 (1113) Buenos Aires, Argentina
| | - M V Espelt
- IQUIFIB - Instituto de Química y Fisicoquímica Biológicas, Conicet/UBA, Junín 956 (1113) Buenos Aires, Argentina
| | - I Mangialavori
- IQUIFIB - Instituto de Química y Fisicoquímica Biológicas, Conicet/UBA, Junín 956 (1113) Buenos Aires, Argentina
| | - M Vigil
- IQUIFIB - Instituto de Química y Fisicoquímica Biológicas, Conicet/UBA, Junín 956 (1113) Buenos Aires, Argentina
| | - J P Rossi
- IQUIFIB - Instituto de Química y Fisicoquímica Biológicas, Conicet/UBA, Junín 956 (1113) Buenos Aires, Argentina.
| | - M Ferreira-Gomes
- IQUIFIB - Instituto de Química y Fisicoquímica Biológicas, Conicet/UBA, Junín 956 (1113) Buenos Aires, Argentina.
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13
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Sethi S, Morgan RK, Feng W, Lin Y, Li X, Luna C, Koch M, Bansal R, Duffel MW, Puschner B, Zoeller RT, Lehmler HJ, Pessah IN, Lein PJ. Comparative Analyses of the 12 Most Abundant PCB Congeners Detected in Human Maternal Serum for Activity at the Thyroid Hormone Receptor and Ryanodine Receptor. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:3948-3958. [PMID: 30821444 PMCID: PMC6457253 DOI: 10.1021/acs.est.9b00535] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Polychlorinated biphenyls (PCBs) pose significant risk to the developing human brain; however, mechanisms of PCB developmental neurotoxicity (DNT) remain controversial. Two widely posited mechanisms are tested here using PCBs identified in pregnant women in the MARBLES cohort who are at increased risk for having a child with a neurodevelopmental disorder (NDD). As determined by gas chromatography-triple quadruple mass spectrometry, the mean PCB level in maternal serum was 2.22 ng/mL. The 12 most abundant PCBs were tested singly and as a mixture mimicking the congener profile in maternal serum for activity at the thyroid hormone receptor (THR) and ryanodine receptor (RyR). Neither the mixture nor the individual congeners (2 fM to 2 μM) exhibited agonistic or antagonistic activity in a THR reporter cell line. However, as determined by equilibrium binding of [3H]ryanodine to RyR1-enriched microsomes, the mixture and the individual congeners (50 nM to 50 μM) increased RyR activity by 2.4-19.2-fold. 4-Hydroxy (OH) and 4-sulfate metabolites of PCBs 11 and 52 had no TH activity; but 4-OH PCB 52 had higher potency than the parent congener toward RyR. These data support evidence implicating RyRs as targets in environmentally triggered NDDs and suggest that PCB effects on the THR are not a predominant mechanism driving PCB DNT. These findings provide scientific rationale regarding a point of departure for quantitative risk assessment of PCB DNT, and identify in vitro assays for screening other environmental pollutants for DNT potential.
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Affiliation(s)
- Sunjay Sethi
- Department of Molecular Biosciences, University of California-Davis, School of Veterinary Medicine, Davis, CA, 95616, USA
| | - Rhianna K. Morgan
- Department of Molecular Biosciences, University of California-Davis, School of Veterinary Medicine, Davis, CA, 95616, USA
| | - Wei Feng
- Department of Molecular Biosciences, University of California-Davis, School of Veterinary Medicine, Davis, CA, 95616, USA
| | - Yanping Lin
- Department of Molecular Biosciences, University of California-Davis, School of Veterinary Medicine, Davis, CA, 95616, USA
| | - Xueshu Li
- Department of Occupational & Environmental Health, University of Iowa, Iowa City, IA, 52242, USA
| | - Corey Luna
- Department of Molecular Biosciences, University of California-Davis, School of Veterinary Medicine, Davis, CA, 95616, USA
| | - Madison Koch
- Department of Molecular Biosciences, University of California-Davis, School of Veterinary Medicine, Davis, CA, 95616, USA
| | - Ruby Bansal
- Department of Biology, University of Massachusetts-Amherst, Amherst, MA, 01003, USA
| | - Michael W. Duffel
- Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, IA 52242, USA
| | - Birgit Puschner
- Department of Molecular Biosciences, University of California-Davis, School of Veterinary Medicine, Davis, CA, 95616, USA
| | - R. Thomas Zoeller
- Department of Biology, University of Massachusetts-Amherst, Amherst, MA, 01003, USA
| | - Hans-Joachim Lehmler
- Department of Occupational & Environmental Health, University of Iowa, Iowa City, IA, 52242, USA
| | - Isaac N. Pessah
- Department of Molecular Biosciences, University of California-Davis, School of Veterinary Medicine, Davis, CA, 95616, USA
| | - Pamela J. Lein
- Department of Molecular Biosciences, University of California-Davis, School of Veterinary Medicine, Davis, CA, 95616, USA
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14
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Truong KM, Pessah IN. Comparison of Chlorantraniliprole and Flubendiamide Activity Toward Wild-Type and Malignant Hyperthermia-Susceptible Ryanodine Receptors and Heat Stress Intolerance. Toxicol Sci 2019; 167:509-523. [PMID: 30329129 PMCID: PMC6358238 DOI: 10.1093/toxsci/kfy256] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Chlorantraniliprole (CP) and flubendiamide (FD) are widely used in agriculture globally to control lepidopteran pests. Both insecticides target ryanodine receptors (RyRs) and promote Ca2+ leak from sarcoplasmic reticulum (SR) within insect skeletal muscle yet are purportedly devoid of activity toward mammalian RyR1 and muscle. RyRs are ion channels that regulate intracellular Ca2+ release from SR during physiological excitation-contraction coupling. Mutations in RYR1 genes confer malignant hyperthermia susceptibility (MHS), a potentially lethal pharmacogenetic disorder in humans and animals. Compared with vehicle control, CP (10 µM) triggers a 65-fold higher rate of Ca2+ efflux from Ca2+-loaded mammalian WT-RyR1 SR vesicles, whereas FD (10 µM) produces negligible influence on Ca2+ leak. We, therefore, compared whether CP or FD differentially influence patterns of high-affinity [3H]ryanodine ([3H]Ry) binding to RyR1 isolated from muscle SR membranes prepared from adult C57BL/6J mice expressing WT, homozygous C-terminal MHS mutation T4826I, or heterozygous N-terminal MHS mutation R163C. Basal [3H]Ry binding differed among genotypes with rank order T4826I ≫R163C∼WT, regardless of [Ca2+] in the assay medium. Both CP and FD (0.01-100 µM) elicited concentration-dependent increase in [3H]Ry binding, although CP showed greater efficacy regardless of genotype or [Ca2+]. Exposure to CP (500 mg/kg; p.o) failed to shift intolerance to heat stress (38°C) characteristic of R163C and T4826I MHS mice, nor cause lethality in WT mice. Although nM-µM of either diamide is capable of differentially altering WT and MHS RyR1 conformation in vitro, human RyR1 mutations within putative diamide N- and C-terminal interaction domains do not alter heat stress intolerance (HSI) in vivo.
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Affiliation(s)
| | - Isaac N Pessah
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California 95616-5270
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15
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Peshenko IV, Cideciyan AV, Sumaroka A, Olshevskaya EV, Scholten A, Abbas S, Koch KW, Jacobson SG, Dizhoor AM. A G86R mutation in the calcium-sensor protein GCAP1 alters regulation of retinal guanylyl cyclase and causes dominant cone-rod degeneration. J Biol Chem 2019; 294:3476-3488. [PMID: 30622141 DOI: 10.1074/jbc.ra118.006180] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 01/04/2019] [Indexed: 11/06/2022] Open
Abstract
The guanylyl cyclase-activating protein, GCAP1, activates photoreceptor membrane guanylyl cyclase (RetGC) in the light, when free Ca2+ concentrations decline, and decelerates the cyclase in the dark, when Ca2+ concentrations rise. Here, we report a novel mutation, G86R, in the GCAP1 (GUCA1A) gene in a family with a dominant retinopathy. The G86R substitution in a "hinge" region connecting EF-hand domains 2 and 3 in GCAP1 strongly interfered with its Ca2+-dependent activator-to-inhibitor conformational transition. The G86R-GCAP1 variant activated RetGC at low Ca2+ concentrations with higher affinity than did the WT GCAP1, but failed to decelerate the cyclase at the Ca2+ concentrations characteristic of dark-adapted photoreceptors. Ca2+-dependent increase in Trp94 fluorescence, indicative of the GCAP1 transition to its RetGC inhibiting state, was suppressed and shifted to a higher Ca2+ range. Conformational changes in G86R GCAP1 detectable by isothermal titration calorimetry (ITC) also became less sensitive to Ca2+, and the dose dependence of the G86R GCAP1-RetGC1 complex inhibition by retinal degeneration 3 (RD3) protein was shifted toward higher than normal concentrations. Our results indicate that the flexibility of the hinge region between EF-hands 2 and 3 is required for placing GCAP1-regulated Ca2+ sensitivity of the cyclase within the physiological range of intracellular Ca2+ at the expense of reducing GCAP1 affinity for the target enzyme. The disease-linked mutation of the hinge Gly86, leading to abnormally high affinity for the target enzyme and reduced Ca2+ sensitivity of GCAP1, is predicted to abnormally elevate cGMP production and Ca2+ influx in photoreceptors in the dark.
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Affiliation(s)
- Igor V Peshenko
- From the Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania 19027
| | - Artur V Cideciyan
- the Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and
| | - Alexander Sumaroka
- the Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and
| | - Elena V Olshevskaya
- From the Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania 19027
| | - Alexander Scholten
- the Department of Neuroscience, University of Oldenburg, Oldenburg D-26129, Germany
| | - Seher Abbas
- the Department of Neuroscience, University of Oldenburg, Oldenburg D-26129, Germany
| | - Karl-Wilhelm Koch
- the Department of Neuroscience, University of Oldenburg, Oldenburg D-26129, Germany
| | - Samuel G Jacobson
- the Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and
| | - Alexander M Dizhoor
- From the Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania 19027,
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16
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Zheng J, Chen J, Zou X, Zhao F, Guo M, Wang H, Zhang T, Zhang C, Feng W, Pessah IN, Cao Z. Saikosaponin d causes apoptotic death of cultured neocortical neurons by increasing membrane permeability and elevating intracellular Ca 2+ concentration. Neurotoxicology 2019; 70:112-121. [PMID: 30458186 PMCID: PMC6342622 DOI: 10.1016/j.neuro.2018.11.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 11/01/2018] [Accepted: 11/14/2018] [Indexed: 01/28/2023]
Abstract
Saikosaponins (SSs) are a class of naturally occurring oleanane-type triterpenoid saponins found in Radix bupleuri that has been widely used in traditional Chinese medicine. As the main active principals of Radix bupleuri, SSs have been shown to suppress mouse motor activity, impair learning and memory, and decrease hippocampal neurogenesis. In the present study, we investigated the effect of five SSs (SSa, SSb1, SSb2, SSc, and SSd) on neuronal viability and the underlying mechanisms in cultured murine neocortical neurons. We demonstrate that SSa, SSb1 and SSd produce concentration-dependent apoptotic neuronal death and induce robust increase in intracellular Ca2+ concentration ([Ca2+]i) at low micromolar concentrations with a rank order of SSd > SSa > SSb1, whereas SSb2 and SSc have no detectable effect on both neuronal survival and [Ca2+]i. Mechanistically, SSd-induced elevation in [Ca2+]i is the primary result of enhanced extracellular Ca2+ influx, which likely triggers Ca2+-induced Ca2+ release through ryanodine receptor activation, but not SERCA inhibition. SSd-induced Ca2+ entry occurs through a non-selective mechanism since blockers of major neuronal Ca2+ entry pathways, including L-type Ca2+ channel, NMDA receptor, AMPA receptor, Na+-Ca2+ exchanger, and TRPV1, all failed to attenuate the Ca2+ response to SSd. Further studies demonstrate that SSd increases calcein efflux and induces an inward current in neocortical neurons. Together, these data demonstrate that SSd elevates [Ca2+]i due to its ability to increase membrane permeability, likely by forming pores in the surface of membrane, which leads to massive Ca2+ influx and apoptotic neuronal death in neocortical neurons.
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Affiliation(s)
- Jing Zheng
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
| | - Juan Chen
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
| | - Xiaohan Zou
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
| | - Fang Zhao
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
| | - Mengqi Guo
- School of Pharmacy, Key Laboratory of Molecular Pharmacology and Drug Evaluation (Yantai University), Ministry of Education, Yantai University, Yantai, China, 2640050
| | - Hongbo Wang
- School of Pharmacy, Key Laboratory of Molecular Pharmacology and Drug Evaluation (Yantai University), Ministry of Education, Yantai University, Yantai, China, 2640050
| | - Tian Zhang
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China, 100875
| | - Chunlei Zhang
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
| | - Wei Feng
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA, 95616
| | - Isaac N Pessah
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA, 95616
| | - Zhengyu Cao
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, China, 211198
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17
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Lindsay C, Sitsapesan M, Chan WM, Venturi E, Welch W, Musgaard M, Sitsapesan R. Promiscuous attraction of ligands within the ATP binding site of RyR2 promotes diverse gating behaviour. Sci Rep 2018; 8:15011. [PMID: 30301919 PMCID: PMC6177429 DOI: 10.1038/s41598-018-33328-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 09/26/2018] [Indexed: 12/31/2022] Open
Abstract
ATP is an essential constitutive regulator of cardiac ryanodine receptors (RyR2), enabling small changes in cytosolic Ca2+ to trigger large changes in channel activity. With recent landmark determinations of the full structures of RyR1 (skeletal isoform) and RyR2 using cryo-EM, and identification of the RyR1 ATP binding site, we have taken the opportunity to model the binding of fragments of ATP into RyR2 in order to investigate how the structure of the ATP site dictates the functional responses of ligands attracted there. RyR2 channel gating was assessed under voltage-clamp conditions and by [3H]ryanodine binding studies. We show that even the triphosphate (PPPi) moiety alone was capable of activating RyR2 but produced two distinct effects (activation or irreversible inactivation) that we suggest correspond to two preferred binding locations within the ATP site. Combinations of complementary fragments of ATP (Pi + ADP or PPi + AMP) could not reproduce the effects of ATP, however, the presence of adenosine prevented the inactivating PPPi effects, allowing activation similar to that of ATP. RyR2 appears to accommodate diverse types of molecules, including PPPi, deep within the ATP binding site. The most effective ligands, however, have at least three phosphate groups that are guided into place by a nucleoside.
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Affiliation(s)
- Chris Lindsay
- Department of Pharmacology, University of Oxford, Oxford, UK.,Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford, UK
| | - Mano Sitsapesan
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Wei Mun Chan
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Elisa Venturi
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - William Welch
- University of Nevada School of Medicine, Department of Biochemistry, Reno, Nevada, USA
| | - Maria Musgaard
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, Oxford, UK. .,Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada.
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18
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Denizalti M, Durlu-Kandilci NT, Simsek G, Bozkurt TE, Sahin-Erdemli I. Rho Kinase and Protein Kinase C Pathways are Responsible for Enhanced Carbachol Contraction in Permeabilized Detrusor in a Rat Model of Cystitis. Basic Clin Pharmacol Toxicol 2018; 123:567-576. [PMID: 29786956 DOI: 10.1111/bcpt.13045] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 05/08/2018] [Indexed: 12/25/2022]
Abstract
Interstitial cystitis is a syndrome characterized by detrusor overactivity and chronic inflammation of the bladder. The mechanisms responsible for the altered smooth muscle contractility remain poorly understood. The aim of the study was to investigate the role of intracellular signalling pathways in carbachol-induced detrusor contraction in a rat model of interstitial cystitis. Cyclophosphamide (150 mg/kg, dissolved in saline) was injected to rats (Sprague-Dawley, female, 200-250 g) intraperitoneally once a day on days 1, 4 and 7 to induce interstitial cystitis. Control groups were injected with saline (0.9% NaCl). Detrusor smooth muscle strips were mounted in 1-ml organ baths containing HEPES-buffered modified Krebs' solution and permeabilized with 40 μM β-escin for 30 min. Carbachol-induced contractions were significantly increased from 21.2 ± 1.6% (saline-treated) to 44 ± 4.4% in cyclophosphamide-treated group. The Rho kinase inhibitor Y-27632 (8.8 ± 2%) and the protein kinase C inhibitor GF-109203X (11.7 ± 2.8%) inhibited the increased contractile response (44 ± 4.4%) in rats with cystitis. The increased carbachol-induced contraction (44 ± 4.4%) was also significantly inhibited by the sarcoplasmic reticulum ryanodine channel blocker ryanodine (25.8 ± 3.2%) and the sarcoplasmic reticulum IP3 receptor blocker heparin (17.2 ± 2.2%) in cystitis. RhoA protein levels in the bladder of cyclophosphamide-treated rats were significantly increased while pan-protein kinase C (α, β and γ isoforms) protein expression was unaltered between experimental groups. Carbachol-induced calcium sensitization at constant and clamped calcium (pCa 6) was also increased in cystitis (from 15.8 ± 2.2% to 24.7 ± 2.8%). This increased response (24.7 ± 2.8%) was significantly inhibited by both Y-27632 (7.9 ± 0.7%) and GF-109203X (4.4 ± 1.5%). We conclude that interstitial cystitis is characterized by an enhanced carbachol contractile response as well as by calcium sensitization of the detrusor smooth muscle. Activation of Rho kinase and protein kinase C pathways may be the molecular culprits responsible for the augmented muscarinic response observed in cystitis.
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Affiliation(s)
- Merve Denizalti
- Department of Pharmacology, Faculty of Pharmacy, Hacettepe University, Ankara, Turkey
| | | | - Gul Simsek
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey
| | - Turgut Emrah Bozkurt
- Department of Pharmacology, Faculty of Pharmacy, Hacettepe University, Ankara, Turkey
| | - Inci Sahin-Erdemli
- Department of Pharmacology, Faculty of Pharmacy, Hacettepe University, Ankara, Turkey
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Neumaier F, Alpdogan S, Hescheler J, Schneider T. A practical guide to the preparation and use of metal ion-buffered systems for physiological research. Acta Physiol (Oxf) 2018; 222. [PMID: 29063736 DOI: 10.1111/apha.12988] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 10/16/2017] [Accepted: 10/17/2017] [Indexed: 12/11/2022]
Abstract
Recent recognition that mobile pools of Zn2+ and Cu2+ are involved in the regulation of neuronal, endocrine and other cells has stimulated the development of tools to visualize and quantify the level of free trace metal ions. Most of the methods used to measure or control loosely bound metals require reference media that contain exactly defined free concentrations of the target ions. Despite the central importance of proper metal ion buffering, there is still a lack of international standards and beginners in the field may have difficulties finding a coherent description of how to prepare trace metal ion buffers, especially when experiments are to be performed in multimetal systems. To close this gap, we provide a guide for the design, preparation and use of metal ion-buffered systems that facilitate immediate application under physiologically relevant ionic conditions. Thermodynamic and kinetic concepts of chemical speciation as well as general protocols and specific examples are outlined for the accurate preparation of single- and dual-metal ion buffers. In addition, experiments have been performed with FluoZin-3 to illustrate that metal ion-buffered systems are required for reliable preparation of nanomolar Zn2+ solutions and that dual-metal ion buffers can be used to calibrate suitable fluorescent Zn2+ sensors in the presence of millimolar Ca2+ concentrations. Together, the information provided should sensitize readers to the many potential pitfalls and uncertainties that exist when working with physiologically relevant concentrations of trace metal ions and enable them to formulate their own metal ion buffers for most in vitro applications.
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Affiliation(s)
- F. Neumaier
- Institute for Neurophysiology; University of Cologne; Cologne Germany
| | - S. Alpdogan
- Institute for Neurophysiology; University of Cologne; Cologne Germany
| | - J. Hescheler
- Institute for Neurophysiology; University of Cologne; Cologne Germany
| | - T. Schneider
- Institute for Neurophysiology; University of Cologne; Cologne Germany
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Gaboardi AJ, Kressler J, Snow TK, Balog EM. Aging impairs regulation of ryanodine receptors from extensor digitorum longus but not soleus muscles. Muscle Nerve 2018; 57:1022-1025. [PMID: 29315676 DOI: 10.1002/mus.26063] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 01/03/2018] [Accepted: 01/06/2018] [Indexed: 11/08/2022]
Abstract
INTRODUCTION Because impaired excitation-contraction coupling and reduced sarcoplasmic reticulum (SR) Ca2+ release may contribute to the age-associated decline in skeletal muscle strength, we investigated the effect of aging on regulation of the skeletal muscle isoform of the ryanodine receptor (RyR1) by physiological channel ligands. METHODS [3 H]Ryanodine binding to membranes from 8- and 26-month-old Fischer 344 extensor digitorum longus (EDL) and soleus muscles was used to investigate the effects of age on RyR1 modulation by Ca2+ and calmodulin (CaM). RESULTS Aging reduced maximal Ca2+ -stimulated binding to EDL membranes. In 0.3 μM Ca2+ , age reduced binding and CaM increased binding to EDL membranes. In 300 μM Ca2+ , CaM reduced binding, but the age effect was not significant. Aging did not affect Ca2+ or CaM regulation of soleus RyR1. DISCUSSION In aged fast-twitch muscle, impaired RyR1 Ca2+ regulation may contribute to lower SR Ca2+ release and reduced muscle function. Muscle Nerve 57: 1022-1025, 2018.
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Affiliation(s)
- Angela J Gaboardi
- School of Applied Physiology, Georgia Institute of Technology, 281 Ferst Drive, Atlanta, GA, 30332, USA
| | - Jochen Kressler
- Exercise and Nutritional Sciences Department, School of Health and Human Services, San Diego State University, 5500 Campanile Dr., San Diego, CA 92182, USA
| | - Teresa K Snow
- School of Applied Physiology, Georgia Institute of Technology, 281 Ferst Drive, Atlanta, GA, 30332, USA
| | - Edward M Balog
- School of Applied Physiology, Georgia Institute of Technology, 281 Ferst Drive, Atlanta, GA, 30332, USA
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Klipp RC, Li N, Wang Q, Word TA, Sibrian-Vazquez M, Strongin RM, Wehrens XHT, Abramson JJ. EL20, a potent antiarrhythmic compound, selectively inhibits calmodulin-deficient ryanodine receptor type 2. Heart Rhythm 2017; 15:578-586. [PMID: 29248564 DOI: 10.1016/j.hrthm.2017.12.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Indexed: 01/06/2023]
Abstract
BACKGROUND Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an arrhythmogenic disorder caused by mutations in the cardiac ryanodine receptor RyR2 that increase diastolic calcium cation (Ca2+) leak from the sarcoplasmic reticulum (SR). Calmodulin (CaM) dissociation from RyR2 has been associated with diastolic Ca2+ leak in heart failure. OBJECTIVE Determine whether the tetracaine-derivative compound EL20 inhibits abnormal Ca2+ release from RyR2 in a CPVT model and investigate the underlying mechanism of inhibition. METHODS Spontaneous Ca2+ sparks in cardiomyocytes and inducible ventricular tachycardia were assessed in a CPVT mouse model, which is heterozygous for the R176Q mutation in RyR2 (R176Q/+ mice) in the presence of EL20 or vehicle. Single-channel studies using sheep cardiac SR or purified RyR2 reconstituted into proteoliposomes with and without exogenous CaM were used to assess mechanisms of inhibition. RESULTS EL20 potently inhibits abnormal Ca2+ release in R176Q/+ myocytes (half-maximal inhibitory concentration = 35.4 nM) and diminishes arrhythmia in R176Q/+ mice. EL20 inhibition of single-channel activity of purified RyR2 occurs in a similar range as seen in R176Q/+ myocytes (half-maximal inhibitory concentration = 8.2 nM). Inhibition of single-channel activity for cardiac SR or purified RyR2 supplemented with 100-nM or 1-μM CaM shows a 200- to 1000-fold reduction in potency. CONCLUSION This work provides a potential therapeutic mechanism for the development of antiarrhythmic compounds that inhibit leaky RyR2 resulting from CaM dissociation, which is often associated with failing hearts. Our data also suggest that CaM dissociation may contribute to the pathogenesis of arrhythmias with the CPVT-linked R176Q mutation.
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Affiliation(s)
- Robert C Klipp
- Department of Physics, Portland State University, Portland, Oregon
| | - Na Li
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas; Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Qiongling Wang
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas
| | - Tarah A Word
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas
| | | | - Robert M Strongin
- Department of Chemistry, Portland State University, Portland, Oregon
| | - Xander H T Wehrens
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas; Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas; Section of Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas; Department of Pediatrics, Baylor College of Medicine, Houston, Texas; Center for Space Medicine, Baylor College of Medicine, Houston, Texas
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Hanna AD, Lam A, Thekkedam C, Willemse H, Dulhunty AF, Beard NA. The Anthracycline Metabolite Doxorubicinol Abolishes RyR2 Sensitivity to Physiological Changes in Luminal Ca2+ through an Interaction with Calsequestrin. Mol Pharmacol 2017; 92:576-587. [DOI: 10.1124/mol.117.108183] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 09/07/2017] [Indexed: 12/31/2022] Open
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Ferreira-Gomes MS, Mangialavori IC, Ontiveros MQ, Rinaldi DE, Martiarena J, Verstraeten SV, Rossi JPFC. Selectivity of plasma membrane calcium ATPase (PMCA)-mediated extrusion of toxic divalent cations in vitro and in cultured cells. Arch Toxicol 2017; 92:273-288. [DOI: 10.1007/s00204-017-2031-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 07/12/2017] [Indexed: 12/26/2022]
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McGuigan JA, Kay JW, Elder HY. Ionised concentrations in calcium and magnesium buffers: Standards and precise measurement are mandatory. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 126:48-64. [DOI: 10.1016/j.pbiomolbio.2017.03.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 01/20/2016] [Accepted: 03/10/2016] [Indexed: 11/16/2022]
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B Kumar R, Zhu L, Hebert H, Jegerschöld C. Method to Visualize and Analyze Membrane Interacting Proteins by Transmission Electron Microscopy. J Vis Exp 2017. [PMID: 28287545 DOI: 10.3791/55148] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Monotopic proteins exert their function when attached to a membrane surface, and such interactions depend on the specific lipid composition and on the availability of enough area to perform the function. Nanodiscs are used to provide a membrane surface of controlled size and lipid content. In the absence of bound extrinsic proteins, sodium phosphotungstate-stained nanodiscs appear as stacks of coins when viewed from the side by transmission electron microscopy (TEM). This protocol is therefore designed to intentionally promote stacking; consequently, the prevention of stacking can be interpreted as the binding of the membrane-binding protein to the nanodisc. In a further step, the TEM images of the protein-nanodisc complexes can be processed with standard single-particle methods to yield low-resolution structures as a basis for higher resolution cryoEM work. Furthermore, the nanodiscs provide samples suitable for either TEM or non-denaturing gel electrophoresis. To illustrate the method, Ca2+-induced binding of 5-lipoxygenase on nanodiscs is presented.
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Affiliation(s)
| | - Lin Zhu
- School of Technology and Health, KTH Royal Institute of Technology
| | - Hans Hebert
- Department of Biosciences and Nutrition, Karolinska Institutet; School of Technology and Health, KTH Royal Institute of Technology
| | - Caroline Jegerschöld
- Department of Biosciences and Nutrition, Karolinska Institutet; School of Technology and Health, KTH Royal Institute of Technology; ;
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McGuigan JAS, Kay JW, Elder HY. Ionised concentrations in calcium and magnesium buffers: Standards and precise measurement are mandatory. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:195-211. [PMID: 26975789 DOI: 10.1016/j.pbiomolbio.2016.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 01/20/2016] [Accepted: 03/10/2016] [Indexed: 06/05/2023]
Abstract
In Ca(2+) and Mg(2+) buffer solutions the ionised concentrations ([X(2+)]) are either calculated or measured. Calculated values vary by up to a factor of seven due to the following four problems: 1) There is no agreement amongst the tabulated constants in the literature. These constants have usually to be corrected for ionic strength and temperature. 2) The ionic strength correction entails the calculation of the single ion activity coefficient, which involves non-thermodynamic assumptions; the data for temperature correction is not always available. 3) Measured pH is in terms of activity i.e. pHa. pHa measurements are complicated by the change in the liquid junction potentials at the reference electrode making an accurate conversion from H(+) activity to H(+) concentration uncertain. 4) Ligands such as EGTA bind water and are not 100% pure. Ligand purity has to be measured, even when the [X(2+)] are calculated. The calculated [X(2+)] in buffers are so inconsistent that calculation is not an option. Until standards are available, the [X(2+)] in the buffers must be measured. The Ligand Optimisation Method is an accurate and independently verified method of doing this (McGuigan & Stumpff, Anal. Biochem. 436, 29, 2013). Lack of standards means it is not possible to compare the published [Ca(2+)] in the nmolar range, and the apparent constant (K(/)) values for Ca(2+) and Mg(2+) binding to intracellular ligands amongst different laboratories. Standardisation of Ca(2+)/Mg(2+) buffers is now essential. The parameters to achieve this are proposed.
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Affiliation(s)
- John A S McGuigan
- Medical, Veterinary and Life Sciences Faculty, University of Glasgow, G12 8QQ, UK.
| | - James W Kay
- Medical, Veterinary and Life Sciences Faculty, University of Glasgow, G12 8QQ, UK
| | - Hugh Y Elder
- Medical, Veterinary and Life Sciences Faculty, University of Glasgow, G12 8QQ, UK
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Kumar RB, Zhu L, Idborg H, Rådmark O, Jakobsson PJ, Rinaldo-Matthis A, Hebert H, Jegerschöld C. Structural and Functional Analysis of Calcium Ion Mediated Binding of 5-Lipoxygenase to Nanodiscs. PLoS One 2016; 11:e0152116. [PMID: 27010627 PMCID: PMC4806843 DOI: 10.1371/journal.pone.0152116] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 03/09/2016] [Indexed: 12/04/2022] Open
Abstract
An important step in the production of inflammatory mediators of the leukotriene family is the Ca2+ mediated recruitment of 5 Lipoxygenase (5LO) to nuclear membranes. To study this reaction in vitro, the natural membrane mimicking environment of nanodiscs was used. Nanodiscs with 10.5 nm inner diameter were made with the lipid POPC and membrane scaffolding protein MSP1E3D1. Monomeric and dimeric 5LO were investigated. Monomeric 5LO mixed with Ca2+ and nanodiscs are shown to form stable complexes that 1) produce the expected leukotriene products from arachidonic acid and 2) can be, for the first time, visualised by native gel electrophoresis and negative stain transmission electron microscopy and 3) show a highest ratio of two 5LO per nanodisc. We interpret this as one 5LO on each side of the disc. The dimer of 5LO is visualised by negative stain transmission electron microscopy and is shown to not bind to nanodiscs. This study shows the advantages of nanodiscs to obtain basic structural information as well as functional information of a complex between a monotopic membrane protein and the membrane.
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Affiliation(s)
- Ramakrishnan B. Kumar
- Department of Biosciences and Nutrition, Karolinska Institutet, 14183 Huddinge, Sweden
- School of Technology and Health, KTH Royal Institute of Technology, 14183 Huddinge, Sweden
| | - Lin Zhu
- Department of Biosciences and Nutrition, Karolinska Institutet, 14183 Huddinge, Sweden
- School of Technology and Health, KTH Royal Institute of Technology, 14183 Huddinge, Sweden
| | - Helena Idborg
- Rheumatology Unit, Department of Medicine, Karolinska Institutet, 17176 Stockholm, Sweden
| | - Olof Rådmark
- Division of Physiological Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 17165 Stockholm, Sweden
| | - Per-Johan Jakobsson
- Rheumatology Unit, Department of Medicine, Karolinska Institutet, 17176 Stockholm, Sweden
| | - Agnes Rinaldo-Matthis
- Division of Physiological Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 17165 Stockholm, Sweden
| | - Hans Hebert
- Department of Biosciences and Nutrition, Karolinska Institutet, 14183 Huddinge, Sweden
- School of Technology and Health, KTH Royal Institute of Technology, 14183 Huddinge, Sweden
| | - Caroline Jegerschöld
- Department of Biosciences and Nutrition, Karolinska Institutet, 14183 Huddinge, Sweden
- School of Technology and Health, KTH Royal Institute of Technology, 14183 Huddinge, Sweden
- * E-mail:
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Knape MJ, Ahuja LG, Bertinetti D, Burghardt NC, Zimmermann B, Taylor SS, Herberg FW. Divalent Metal Ions Mg²⁺ and Ca²⁺ Have Distinct Effects on Protein Kinase A Activity and Regulation. ACS Chem Biol 2015. [PMID: 26200257 DOI: 10.1021/acschembio.5b00271] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
cAMP-dependent protein kinase (PKA) is regulated primarily in response to physiological signals while nucleotides and metals may provide fine-tuning. PKA can use different metal ions for phosphoryl transfer, yet some, like Ca(2+), do not support steady-state catalysis. Fluorescence Polarization (FP) and Surface Plasmon Resonance (SPR) were used to study inhibitor and substrate interactions with PKA. The data illustrate how metals can act differentially as a result of their inherent coordination properties. We found that Ca(2+), in contrast to Mg(2+), does not induce high-affinity binding of PKA to pseudosubstrate inhibitors. However, Ca(2+) works in a single turnover mode to allow for phosphoryl-transfer. Using a novel SPR approach, we were able to directly monitor the interaction of PKA with a substrate in the presence of Mg(2+)ATP. This allows us to depict the entire kinase reaction including complex formation as well as release of the phosphorylated substrate. In contrast to Mg(2+), Ca(2+) apparently slows down the enzymatic reaction. A focus on individual reaction steps revealed that Ca(2+) is not as efficient as Mg(2+) in stabilizing the enzyme:substrate complex. The opposite holds true for product dissociation where Mg(2+) easily releases the phospho-substrate while Ca(2+) traps both reaction products at the active site. This explains the low steady-state activity in the presence of Ca(2+). Furthermore, Ca(2+) is able to modulate kinase activity as well as inhibitor binding even in the presence of Mg(2+). We therefore hypothesize that the physiological metal ions Mg(2+) and Ca(2+) both play a role in kinase activity and regulation. Since PKA is localized close to calcium channels and may render PKA activity susceptible to Ca(2+), our data provide a possible mechanism for novel crosstalk between cAMP and calcium signaling.
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Affiliation(s)
- Matthias J. Knape
- Department
of Biochemistry, University of Kassel, 34132 Kassel, Germany
| | - Lalima G. Ahuja
- Department
of Pharmacology, University of California at San Diego, La Jolla, California 92093, United States
| | | | | | | | - Susan S. Taylor
- Department
of Pharmacology, University of California at San Diego, La Jolla, California 92093, United States
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Durlu-Kandilci NT, Denizalti M, Sahin-Erdemli I. Aging changes agonist induced contractile responses in permeabilized rat bladder. AGE (DORDRECHT, NETHERLANDS) 2015; 37:9807. [PMID: 26153091 PMCID: PMC4497501 DOI: 10.1007/s11357-015-9807-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 06/21/2015] [Indexed: 06/04/2023]
Abstract
Aging alters bladder functions where a decrease in filling, storage and emptying is observed. These changes cause urinary incontinence, especially in women. The aim of this study is to examine how aging affects the intracellular calcium movements due to agonist-induced contractions in permeabilized female rat bladder. Urinary bladder isolated from young and old female Sprague-Dawley rats were used. Small detrusor strips were permeabilized with β-escin. The contractile responses induced with agonists were compared between young and old groups. Carbachol-induced contractions were decreased in permeabilized detrusor from old rats compared to young group. Heparin and ryanodine decreased carbachol-induced contractions in young rats where only heparin inhibited these contractions in olds. Caffeine-induced contractions but not inositol triphosphate (IP3)-induced contractions were decreased in old group compared to youngs. The cumulative calcium response curves (pCa 8-4) were also decreased in old rats. Carbachol-induced calcium sensitization responses did not alter by age where GTP-β-S and GF-109203X but not Y-27632 inhibited these responses. Carbachol-induced contractions decrease with aging in rat bladder detrusor. It can be postulated as IP3-induced calcium release (IICR) is primarily responsible for the contractions in older rats where the decrease in carbachol contractions in aging may be as a result of a decrease in calcium-induced calcium release (CICR), rather than carbachol-induced calcium sensitization.
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Affiliation(s)
- N Tugba Durlu-Kandilci
- Faculty of Pharmacy, Department of Pharmacology, Hacettepe University, 06100, Sıhhiye, Ankara, Turkey,
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Myosin VI deafness mutation prevents the initiation of processive runs on actin. Proc Natl Acad Sci U S A 2015; 112:E1201-9. [PMID: 25751888 DOI: 10.1073/pnas.1420989112] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mutations in the reverse-direction myosin, myosin VI, are associated with deafness in humans and mice. A myosin VI deafness mutation, D179Y, which is in the transducer of the motor, uncoupled the release of the ATP hydrolysis product, inorganic phosphate (Pi), from dependency on actin binding and destroyed the ability of single dimeric molecules to move processively on actin filaments. We observed that processive movement is rescued if ATP is added to the mutant dimer following binding of both heads to actin in the absence of ATP, demonstrating that the mutation selectively destroys the initiation of processive runs at physiological ATP levels. A drug (omecamtiv) that accelerates the actin-activated activity of cardiac myosin was able to rescue processivity of the D179Y mutant dimers at physiological ATP concentrations by slowing the actin-independent release of Pi. Thus, it may be possible to create myosin VI-specific drugs that rescue the function of deafness-causing mutations.
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Fritsch EB, Stegeman JJ, Goldstone JV, Nacci DE, Champlin D, Jayaraman S, Connon RE, Pessah IN. Expression and function of ryanodine receptor related pathways in PCB tolerant Atlantic killifish (Fundulus heteroclitus) from New Bedford Harbor, MA, USA. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2015; 159:156-66. [PMID: 25546006 PMCID: PMC4300256 DOI: 10.1016/j.aquatox.2014.12.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 12/14/2014] [Accepted: 12/17/2014] [Indexed: 05/12/2023]
Abstract
Atlantic killifish (Fundulus heteroclitus) thrive in New Bedford Harbor (NBH), MA, highly contaminated with polychlorinated biphenyls (PCBs). Resident killifish have evolved tolerance to dioxin-like (DL) PCBs, whose toxic effects through the aryl hydrocarbon receptor (AhR) are well studied. In NBH, non-dioxin like PCBs (NDL PCBs), which lack activity toward the AhR, vastly exceed levels of DL congeners yet how killifish counter NDL toxic effects has not been explored. In mammals and fish, NDL PCBs are potent activators of ryanodine receptors (RyR), Ca(2+) release channels necessary for a vast array of physiological processes. In the current study we compared the expression and function of RyR related pathways in NBH killifish with killifish from the reference site at Scorton Creek (SC, MA). Relative to the SC fish, adults from NBH displayed increased levels of skeletal muscle RyR1 protein, and increased levels of FK506-binding protein 12 kDa (FKBP12) an accessory protein essential for NDL PCB-triggered changes in RyR channel function. In accordance with increased RyR1 levels, NBH killifish displayed increased maximal ligand binding, increased maximal response to Ca(2+) activation and increased maximal response to activation by the NDL PCB congener PCB 95. Compared to SC, NBH embryos and larvae had increased levels of mtor and ryr2 transcripts at multiple stages of development, and generations, while levels of serca2 were decreased at 9 days post-fertilization in the F1 and F2 generations. These findings suggest that there are compensatory and heritable changes in RyR mediated Ca(2+) signaling proteins or potential signaling partners in NBH killifish.
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Affiliation(s)
- Erika B Fritsch
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, CA, USA.
| | - John J Stegeman
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Jared V Goldstone
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Diane E Nacci
- Atlantic Ecology Division, Office of Research and Development, US Environmental Protection Agency, Narragansett, RI, USA
| | - Denise Champlin
- Atlantic Ecology Division, Office of Research and Development, US Environmental Protection Agency, Narragansett, RI, USA
| | - Saro Jayaraman
- Atlantic Ecology Division, Office of Research and Development, US Environmental Protection Agency, Narragansett, RI, USA
| | - Richard E Connon
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, CA, USA
| | - Isaac N Pessah
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, CA, USA; The Medical Investigations of Neurodevelopmental Disorders (MIND) Institute, University of California Davis Medical Center, Sacramento, USA
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Putula J, Pihlajamaa T, Kukkonen JP. Calcium affects OX1 orexin (hypocretin) receptor responses by modifying both orexin binding and the signal transduction machinery. Br J Pharmacol 2014; 171:5816-28. [PMID: 25132134 PMCID: PMC4290719 DOI: 10.1111/bph.12883] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 08/05/2014] [Accepted: 08/12/2014] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND AND PURPOSE One of the major responses upon orexin receptor activation is Ca(2+) influx, and this influx seems to amplify the other responses mediated by orexin receptors. However, the reduction in Ca(2+) , often used to assess the importance of Ca(2+) influx, might affect other properties, like ligand-receptor interactions, as suggested for some GPCR systems. Hence, we investigated the role of the ligand-receptor interaction and Ca(2+) signal cascades in the apparent Ca(2+) requirement of orexin-A signalling. EXPERIMENTAL APPROACH Receptor binding was assessed in CHO cells expressing human OX1 receptors with [(125) I]-orexin-A by conventional ligand binding as well as scintillation proximity assays. PLC activity was determined by chromatography. KEY RESULTS Both orexin receptor binding and PLC activation were strongly dependent on the extracellular Ca(2+) concentration. The relationship between Ca(2+) concentration and receptor binding was the same as that for PLC activation. However, when Ca(2+) entry was reduced by depolarizing the cells or by inhibiting the receptor-operated Ca(2+) channels, orexin-A-stimulated PLC activity was much more strongly inhibited than orexin-A binding. CONCLUSIONS AND IMPLICATIONS Ca(2+) plays a dual role in orexin signalling by being a prerequisite for both ligand-receptor interaction and amplifying orexin signals via Ca(2+) influx. Some previous results obtained utilizing Ca(2+) chelators have to be re-evaluated based on the results of the current study. From a drug discovery perspective, further experiments need to identify the target for Ca(2+) in orexin-A-OX1 receptor interaction and its mechanism of action.
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Affiliation(s)
- Jaana Putula
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of HelsinkiHelsinki, Finland
| | - Tero Pihlajamaa
- Program in Structural Biology and Biophysics, Institute of Biotechnology, University of HelsinkiHelsinki, Finland
| | - Jyrki P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of HelsinkiHelsinki, Finland
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Niknam Y, Feng W, Cherednichenko G, Dong Y, Joshi SN, Vyas SM, Lehmler HJ, Pessah IN. Structure-activity relationship of selected meta- and para-hydroxylated non-dioxin like polychlorinated biphenyls: from single RyR1 channels to muscle dysfunction. Toxicol Sci 2013; 136:500-13. [PMID: 24014653 DOI: 10.1093/toxsci/kft202] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Non-dioxin like polychlorinated biphenyls (NDL-PCBs) are legacy environmental contaminants with contemporary unintentional sources. NDL-PCBs interact with ryanodine receptors (RyRs), Ca(2+) channels of sarcoplasmic/endoplasmic reticulum (SR/ER) that regulate excitation-contraction coupling (ECC) and Ca(2+)-dependent cell signaling in muscle. Activities of 4 chiral congeners PCB91, 95, 132, and 149 and their respective 4- and 5-hydroxy (-OH) derivatives toward rabbit skeletal muscle ryanodine receptor (RyR1) are investigated using [(3)H]ryanodine binding and SR Ca(2+) flux analyses. Although 5-OH metabolites have comparable activity to their respective parent in both assays, 4-OH derivatives are unable to trigger Ca(2+) release from SR microsomes in the presence of Ca(2+)-ATPase activity. PCB95 and derivatives are investigated using single channel voltage-clamp and primary murine embryonic muscle cells (myotubes). Like PCB95, 5-OH-PCB95 quickly and persistently increases channel open probability (p o > .9) by stabilizing the full-open channel state, whereas 4-OH-PCB95 transiently enhances p o. Ca(2+) imaging of myotubes loaded with Fluo-4 show that acute exposure to PCB95 (5 µM) potentiates ECC and caffeine responses and partially depletes SR Ca(2+) stores. Exposure to 5-OH-PCB95 (5 µM) increases cytoplasmic Ca(2+), leading to rapid ECC failure in 50% of myotubes with the remainder retaining negligible responses. 4-OH-PCB95 neither increases baseline Ca(2+) nor causes ECC failure but depresses ECC and caffeine responses by 50%. With longer (3h) exposure to 300 nM PCB95, 5-OH-PCB95, or 4-OH-PCB95 decreases the number of ECC responsive myotubes by 22%, 81%, and 51% compared with control by depleting SR Ca(2+) and/or uncoupling ECC. NDL-PCBs and their 5-OH and 4-OH metabolites differentially influence RyR1 channel activity and ECC in embryonic skeletal muscle.
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Affiliation(s)
- Yassaman Niknam
- * Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California 95616
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Li J, Imtiaz MS, Beard NA, Dulhunty AF, Thorne R, vanHelden DF, Laver DR. ß-Adrenergic stimulation increases RyR2 activity via intracellular Ca2+ and Mg2+ regulation. PLoS One 2013; 8:e58334. [PMID: 23533585 PMCID: PMC3606165 DOI: 10.1371/journal.pone.0058334] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 02/02/2013] [Indexed: 01/19/2023] Open
Abstract
Here we investigate how ß-adrenergic stimulation of the heart alters regulation of ryanodine receptors (RyRs) by intracellular Ca2+ and Mg2+ and the role of these changes in SR Ca2+ release. RyRs were isolated from rat hearts, perfused in a Langendorff apparatus for 5 min and subject to 1 min perfusion with 1 µM isoproterenol or without (control) and snap frozen in liquid N2 to capture their phosphorylation state. Western Blots show that RyR2 phosphorylation was increased by isoproterenol, confirming that RyR2 were subject to normal ß-adrenergic signaling. Under basal conditions, S2808 and S2814 had phosphorylation levels of 69% and 15%, respectively. These levels were increased to 83% and 60%, respectively, after 60 s of ß-adrenergic stimulation consistent with other reports that ß-adrenergic stimulation of the heart can phosphorylate RyRs at specific residues including S2808 and S2814 causing an increase in RyR activity. At cytoplasmic [Ca2+] <1 µM, ß-adrenergic stimulation increased luminal Ca2+ activation of single RyR channels, decreased luminal Mg2+ inhibition and decreased inhibition of RyRs by mM cytoplasmic Mg2+. At cytoplasmic [Ca2+] >1 µM, ß-adrenergic stimulation only decreased cytoplasmic Mg2+ and Ca2+ inhibition of RyRs. The Ka and maximum levels of cytoplasmic Ca2+ activation site were not affected by ß-adrenergic stimulation. Our RyR2 gating model was fitted to the single channel data. It predicted that in diastole, ß-adrenergic stimulation is mediated by 1) increasing the activating potency of Ca2+ binding to the luminal Ca2+ site and decreasing its affinity for luminal Mg2+ and 2) decreasing affinity of the low-affinity Ca2+/Mg2+ cytoplasmic inhibition site. However in systole, ß-adrenergic stimulation is mediated mainly by the latter.
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Affiliation(s)
- Jiao Li
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
| | - Mohammad S. Imtiaz
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
| | - Nicole A. Beard
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Angela F. Dulhunty
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Rick Thorne
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
| | - Dirk F. vanHelden
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
| | - Derek R. Laver
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
- * E-mail:
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Sepúlveda MR, Wuytack F, Mata AM. High levels of Mn²⁺ inhibit secretory pathway Ca²⁺/Mn²⁺-ATPase (SPCA) activity and cause Golgi fragmentation in neurons and glia. J Neurochem 2012; 123:824-36. [PMID: 22845487 DOI: 10.1111/j.1471-4159.2012.07888.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 06/19/2012] [Accepted: 07/18/2012] [Indexed: 11/28/2022]
Abstract
Excess Mn(2+) in humans causes a neurological disorder known as manganism, which shares symptoms with Parkinson's disease. However, the cellular mechanisms underlying Mn(2+) -neurotoxicity and the involvement of Mn(2+) -transporters in cellular homeostasis and repair are poorly understood and require further investigation. In this work, we have analyzed the effect of Mn(2+) on neurons and glia from mice in primary cultures. Mn(2+) overload compromised survival of both cell types, specifically affecting cellular integrity and Golgi organization, where the secretory pathway Ca(2+) /Mn(2+) -ATPase is localized. This ATP-driven Mn(2+) transporter might take part in Mn(2+) accumulation/detoxification at low loads of Mn(2+) , but its ATPase activity is inhibited at high concentration of Mn(2+) . Glial cells appear to be significantly more resistant to this toxicity than neurons and their presence in cocultures provided some protection to neurons against degeneration induced by Mn(2+) . Interestingly, the Mn(2+) toxicity was partially reversed upon Mn(2+) removal by wash out or by the addition of EDTA as a chelating agent, in particular in glial cells. These studies provide data on Mn(2+) neurotoxicity and may contribute to explore new therapeutic approaches for reducing Mn(2+) poisoning.
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Affiliation(s)
- M Rosario Sepúlveda
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
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Peshenko IV, Olshevskaya EV, Lim S, Ames JB, Dizhoor AM. Calcium-myristoyl Tug is a new mechanism for intramolecular tuning of calcium sensitivity and target enzyme interaction for guanylyl cyclase-activating protein 1: dynamic connection between N-fatty acyl group and EF-hand controls calcium sensitivity. J Biol Chem 2012; 287:13972-84. [PMID: 22383530 DOI: 10.1074/jbc.m112.341883] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Guanylyl cyclase-activating protein 1 (GCAP1), a myristoylated Ca(2+) sensor in vision, regulates retinal guanylyl cyclase (RetGC). We show that protein-myristoyl group interactions control Ca(2+) sensitivity, apparent affinity for RetGC, and maximal level of cyclase activation. Mutating residues near the myristoyl moiety affected the affinity of Ca(2+) binding to EF-hand 4. Inserting Phe residues in the cavity around the myristoyl group increased both the affinity of GCAP1 for RetGC and maximal activation of the cyclase. NMR spectra show that the myristoyl group in the L80F/L176F/V180F mutant remained sequestered inside GCAP1 in both Ca(2+)-bound and Mg(2+)-bound states. This mutant displayed much higher affinity for the cyclase but reduced Ca(2+) sensitivity of the cyclase regulation. The L176F substitution improved affinity of myristoylated and non-acylated GCAP1 for the cyclase but simultaneously reduced the affinity of Ca(2+) binding to EF-hand 4 and Ca(2+) sensitivity of the cyclase regulation by acylated GCAP1. The replacement of amino acids near both ends of the myristoyl moiety (Leu(80) and Val(180)) minimally affected regulatory properties of GCAP1. N-Lauryl- and N-myristoyl-GCAP1 activated RetGC in a similar fashion. Thus, protein interactions with the central region of the fatty acyl chain optimize GCAP1 binding to RetGC and maximize activation of the cyclase. We propose a dynamic connection (or "tug") between the fatty acyl group and EF-hand 4 via the C-terminal helix that attenuates the efficiency of RetGC activation in exchange for optimal Ca(2+) sensitivity.
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Affiliation(s)
- Igor V Peshenko
- Department of Basic Sciences and Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania 19027, USA
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Barrientos GC, Feng W, Truong K, Matthaei KI, Yang T, Allen PD, Lopez JR, Pessah IN. Gene dose influences cellular and calcium channel dysregulation in heterozygous and homozygous T4826I-RYR1 malignant hyperthermia-susceptible muscle. J Biol Chem 2011; 287:2863-76. [PMID: 22139840 DOI: 10.1074/jbc.m111.307926] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Malignant hyperthermia susceptibility (MHS) is primarily conferred by mutations within ryanodine receptor type 1 (RYR1). Here we address how the MHS mutation T4826I within the S4-S5 linker influences excitation-contraction coupling and resting myoplasmic Ca(2+) concentration ([Ca(2+)](rest)) in flexor digitorum brevis (FDB) and vastus lateralis prepared from heterozygous (Het) and homozygous (Hom) T4826I-RYR1 knock-in mice (Yuen, B. T., Boncompagni, S., Feng, W., Yang, T., Lopez, J. R., Matthaei, K. I., Goth, S. R., Protasi, F., Franzini-Armstrong, C., Allen, P. D., and Pessah, I. N. (2011) FASEB J. doi:22131268). FDB responses to electrical stimuli and acute halothane (0.1%, v/v) exposure showed a rank order of Hom ≫ Het ≫ WT. Release of Ca(2+) from the sarcoplasmic reticulum and Ca(2+) entry contributed to halothane-triggered increases in [Ca(2+)](rest) in Hom FDBs and elicited pronounced Ca(2+) oscillations in ∼30% of FDBs tested. Genotype contributed significantly elevated [Ca(2+)](rest) (Hom > Het > WT) measured in vivo using ion-selective microelectrodes. Het and Hom oxygen consumption rates measured in intact myotubes using the Seahorse Bioscience (Billerica, MA) flux analyzer and mitochondrial content measured with MitoTracker were lower than WT, whereas total cellular calpain activity was higher than WT. Muscle membranes did not differ in RYR1 expression nor in Ser(2844) phosphorylation among the genotypes. Single channel analysis showed highly divergent gating behavior with Hom and WT favoring open and closed states, respectively, whereas Het exhibited heterogeneous gating behaviors. [(3)H]Ryanodine binding analysis revealed a gene dose influence on binding density and regulation by Ca(2+), Mg(2+), and temperature. Pronounced abnormalities inherent in T4826I-RYR1 channels confer MHS and promote basal disturbances of excitation-contraction coupling, [Ca(2+)](rest), and oxygen consumption rates. Considering that both Het and Hom T4826I-RYR1 mice are viable, the remarkable isolated single channel dysfunction mediated through this mutation in S4-S5 cytoplasmic linker must be highly regulated in vivo.
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Affiliation(s)
- Genaro C Barrientos
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California 95616, USA
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Mice null for calsequestrin 1 exhibit deficits in functional performance and sarcoplasmic reticulum calcium handling. PLoS One 2011; 6:e27036. [PMID: 22164205 PMCID: PMC3229475 DOI: 10.1371/journal.pone.0027036] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 10/09/2011] [Indexed: 01/06/2023] Open
Abstract
In skeletal muscle, the release of calcium (Ca2+) by ryanodine sensitive sarcoplasmic reticulum (SR) Ca2+ release channels (i.e., ryanodine receptors; RyR1s) is the primary determinant of contractile filament activation. Much attention has been focused on calsequestrin (CASQ1) and its role in SR Ca2+ buffering as well as its potential for modulating RyR1, the L-type Ca2+ channel (dihydropyridine receptor, DHPR) and other sarcolemmal channels through sensing luminal [Ca2+]. The genetic ablation of CASQ1 expression results in significant alterations in SR Ca2+ content and SR Ca2+ release especially during prolonged activation. While these findings predict a significant loss-of-function phenotype in vivo, little information on functional status of CASQ1 null mice is available. We examined fast muscle in vivo and in vitro and identified significant deficits in functional performance that indicate an inability to sustain contractile activation. In single CASQ1 null skeletal myofibers we demonstrate a decrease in voltage dependent RyR Ca2+ release with single action potentials and a collapse of the Ca2+ release with repetitive trains. Under voltage clamp, SR Ca2+ release flux and total SR Ca2+ release are significantly reduced in CASQ1 null myofibers. The decrease in peak Ca2+ release flux appears to be solely due to elimination of the slowly decaying component of SR Ca2+ release, whereas the rapidly decaying component of SR Ca2+ release is not altered in either amplitude or time course in CASQ1 null fibers. Finally, intra-SR [Ca2+] during ligand and voltage activation of RyR1 revealed a significant decrease in the SR[Ca2+]free in intact CASQ1 null fibers and a increase in the release and uptake kinetics consistent with a depletion of intra-SR Ca2+ buffering capacity. Taken together we have revealed that the genetic ablation of CASQ1 expression results in significant functional deficits consistent with a decrease in the slowly decaying component of SR Ca2+ release.
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Enyeart JJ, Liu H, Enyeart JA. Calcium-dependent inhibition of adrenal TREK-1 channels by angiotensin II and ionomycin. Am J Physiol Cell Physiol 2011; 301:C619-29. [PMID: 21613605 DOI: 10.1152/ajpcell.00117.2011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Bovine adrenocortical cells express bTREK-1 K(+) (bovine KCNK2) channels that are inhibited by ANG II through a Gq-coupled receptor by separate Ca(2+) and ATP hydrolysis-dependent signaling pathways. Whole cell and single patch clamp recording from adrenal zona fasciculata (AZF) cells were used to characterize Ca(2+)-dependent inhibition of bTREK-1. In whole cell recordings with pipette solutions containing 0.5 mM EGTA and no ATP, the Ca(2+) ionophore ionomycin (1 μM) produced a transient inhibition of bTREK-1 that reversed spontaneously within minutes. At higher concentrations, ionomycin (5-10 μM) produced a sustained inhibition of bTREK-1 that was reversible upon washing, even in the absence of hydrolyzable [ATP](i). BAPTA was much more effective than EGTA at suppressing bTREK-1 inhibition by ANG II. When intracellular Ca(2+) concentration ([Ca(2+)](i)) was buffered to 20 nM with either 11 mM BAPTA or EGTA, ANG II (10 nM) inhibited bTREK-1 by 12.0 ± 4.5% (n=11) and 59.3 ± 8.4% (n=4), respectively. Inclusion of the water-soluble phosphatidylinositol 4,5-bisphosphate (PIP(2)) analog DiC(8)PI(4,5)P(2) in the pipette failed to increase bTREK-1 expression or reduce its inhibition by ANG II. The open probability (P(o)) of unitary bTREK-1 channels recorded from inside-out patches was reduced by Ca(2+) (10-35 μM) in a concentration-dependent manner. These results are consistent with a model in which ANG II inhibits bTREK-1 K(+) channels by a Ca(2+)-dependent mechanism that does not require the depletion of membrane-associated PIP(2). They further indicate that the Ca(2+) source is located in close proximity within a "Ca(2+) nanodomain" of bTREK-1 channels, where [Ca(2+)](i) may reach concentrations of >10 μM. bTREK-1 is the first two-pore K(+) channel shown to be inhibited by Ca(2+) through activation of a G protein-coupled receptor.
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Affiliation(s)
- John J Enyeart
- Department of Neuroscience, The Ohio State University, College of Medicine and Public Health, Columbus, 43210-1239, USA.
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Asuero AG, Michałowski T. Comprehensive Formulation of Titration Curves for Complex Acid-Base Systems and Its Analytical Implications. Crit Rev Anal Chem 2011. [DOI: 10.1080/10408347.2011.559440] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Abstract
Calcium (Ca(2+)) is a critical regulator of an immense array of biological processes, and the intracellular [Ca(2+)] that regulates these processes is ~ 10,000 lower than the extracellular [Ca(2+)]. To study and understand these myriad Ca(2+)-dependent functions requires control and measurement of [Ca(2+)] in the nano- to micromolar range (where contaminating Ca(2+) is a significant problem). As with pH, it is often essential to use Ca(2+) buffers to control free [Ca(2+)] at the desired biologically relevant concentrations. Fortunately, there are numerous available Ca(2+) buffers with different affinities that make this practical. However, there are numerous caveats with respect to making these solutions appropriately with known Ca(2+) buffers. These include pH dependence, selectivity for Ca(2+) (e.g., vs. Mg(2+)), ionic strength and temperature dependence, and complex multiple equilibria that occur in physiologically relevant solutions. Here we discuss some basic principles of Ca(2+) buffering with respect to some of these caveats and provide practical tools (including freely downloadable computer programs) to help in the making and calibration of Ca(2+)-buffered solutions for a wide array of biological applications.
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Denizalti M, Durlu-Kandilci NT, Bozkurt TE, Sahin-Erdemli I. Hydrogen sulphide inhibits carbachol-induced contractile responses in β-escin permeabilized guinea-pig taenia caecum. Eur J Pharmacol 2011; 658:229-35. [PMID: 21371473 DOI: 10.1016/j.ejphar.2011.02.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 02/10/2011] [Accepted: 02/17/2011] [Indexed: 10/18/2022]
Abstract
Hydrogen sulphide (H(2)S) is an endogenous mediator producing a potent relaxation response in vascular and non-vascular smooth muscles. While ATP-sensitive potassium channels are mainly involved in this relaxant effect in vascular smooth muscle, the mechanism in other smooth muscles has not been revealed yet. In the present study, we investigated how H(2)S relaxes non-vascular smooth muscle by using intact and β-escin permeabilized guinea-pig taenia caecum. In intact tissues, concentration-dependent relaxation response to H(2)S donor NaHS in carbachol-precontracted preparations did not change in the presence of a K(ATP) channel blocker glibenclamide, adenylate cyclase inhibitor SQ-22536, guanylate cyclase inhibitor ODQ, protein kinase A inhibitor KT-5720, protein kinase C inhibitor H-7, tetrodotoxin, apamin/charybdotoxin, NOS inhibitor L-NAME and cyclooxygenase inhibitor indomethacin. We then studied how H(2)S affected carbachol- or Ca(2+)-induced contractions in permeabilized tissues. When Ca(2+) was clamped to a constant value (pCa6), a further contraction could be elicited by carbachol that was decreased by NaHS. This decrease in contraction was reversed by catalase but not by superoxide dismutase or N-acetyl cysteine. The sarcoplasmic reticulum Ca(2+)-ATPase pump inhibitor, cyclopiazonic acid, also decreased the carbachol-induced contraction that was further inhibited by NaHS. Mitochondrial proton pump inhibitor carbonyl cyanide p-trifluromethoxyphenylhydrazone also decreased the carbachol-induced contraction but this was not additionally changed by NaHS. The carbachol-induced Ca(2+) sensitization, calcium concentration-response curves, IP(3)- and caffeine-induced contractions were not affected by NaHS. In conclusion, we propose that hydrogen peroxide and mitochondria may have a role in H(2)S-induced relaxation response in taenia caecum.
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Affiliation(s)
- Merve Denizalti
- Hacettepe University, Faculty of Pharmacy, Department of Pharmacology, 06100, Sıhhiye, Ankara, Turkey
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Site-specific modification of calmodulin Ca²(+) affinity tunes the skeletal muscle ryanodine receptor activation profile. Biochem J 2010; 432:89-99. [PMID: 20815817 DOI: 10.1042/bj20100505] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The skeletal muscle isoform of the ryanodine receptor Ca²(+)-release channel (RyR1) is regulated by Ca²(+) and CaM (calmodulin). CaM shifts the biphasic Ca²(+)-dependence of RyR1 activation leftward, effectively increasing channel opening at low Ca²(+) and decreasing channel opening at high Ca²(+). The conversion of CaM from a RyR1 activator into an inhibitor is due to the binding of Ca²(+) to CaM; however, which of CaM's four Ca²(+)-binding sites serves as the switch for this conversion is unclear. We engineered a series of mutant CaMs designed to individually increase the Ca²(+) affinity of each of CaM's EF-hands by increasing the number of acidic residues in Ca²(+)-chelating positions. Domain-specific Ca²(+) affinities of each CaM variant were determined by equilibrium fluorescence titration. Mutations in sites I (T26D) or II (N60D) in CaM's N-terminal domain had little effect on CaM Ca²(+) affinity and regulation of RyR1. However, the site III mutation N97D increased the Ca²(+)-binding affinity of CaM's C-terminal domain and caused CaM to inhibit RyR1 at a lower Ca²(+) concentration than wild-type CaM. Conversely, the site IV mutation Q135D decreased the Ca²(+)-binding affinity of CaM's C-terminal domain and caused CaM to inhibit RyR1 at higher Ca²(+) concentrations. These results support the hypothesis that Ca²(+) binding to CaM's C-terminal acts as the switch converting CaM from a RyR1 activator into a channel inhibitor. These results indicate further that targeting CaM's Ca²(+) affinity may be a valid strategy to tune the activation profile of CaM-regulated ion channels.
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Wieczorek L, Maas JW, Muglia LM, Vogt SK, Muglia LJ. Temporal and regional regulation of gene expression by calcium-stimulated adenylyl cyclase activity during fear memory. PLoS One 2010; 5:e13385. [PMID: 20976279 PMCID: PMC2954788 DOI: 10.1371/journal.pone.0013385] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Accepted: 09/19/2010] [Indexed: 12/02/2022] Open
Abstract
Background The Ca2+-stimulated adenylyl cyclases (ACs), AC1 and AC8, are key components of long-term memory processing. AC1 and AC8 double knockout mice (Adcy1−/−Adcy8−/−; DKO) display impaired fear memory processing; the mechanism of this impairment is largely unknown. Methodology/Principal Findings We hypothesize that the Ca2+-stimulated ACs modulate long-lasting transcriptional changes essential for fear memory consolidation and maintenance. Here, we report a genome-wide study of gene expression changes associated with conditioned fear (CF) memory in wild-type and DKO mice to identify AC-dependent gene regulatory changes that occur in the amygdala and hippocampus at baseline and different time points after CF learning. We observed an overall decrease in transcriptional changes in DKO mice across all time points, but most strikingly, at periods when memory consolidation and retention should be occurring. Further, we identified a shared set of transcription factor binding sites in genes upregulated in wild-type mice that were associated with downregulated genes in DKO mice. To prove the temporal and regional importance of AC activity on different stages of memory processing, the tetracycline-off system was used to produce mice with forebrain-specific inducible expression of AC8 on a DKO background. CF behavioral results reveal that adult restoration of AC8 activity in the forebrain is sufficient for intact learning, while cessation of this expression at any time point across learning causes memory deficits. Conclusions/Significance Overall, these studies demonstrate that the Ca2+-stimulated ACs contribute to the formation and maintenance of fear memory by a network of long-term transcriptional changes.
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Affiliation(s)
- Lindsay Wieczorek
- Departments of Pediatrics and Developmental Biology, Washington University, Saint Louis, Missouri, United States of America
| | - James W. Maas
- Departments of Pediatrics and Developmental Biology, Washington University, Saint Louis, Missouri, United States of America
| | - Lisa M. Muglia
- Departments of Pediatrics and Molecular Physiology and Biophysics, and Vanderbilt Kennedy Center, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Sherri K. Vogt
- Departments of Pediatrics and Developmental Biology, Washington University, Saint Louis, Missouri, United States of America
| | - Louis J. Muglia
- Departments of Pediatrics and Molecular Physiology and Biophysics, and Vanderbilt Kennedy Center, Vanderbilt University, Nashville, Tennessee, United States of America
- * E-mail:
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Eltit JM, Feng W, Lopez JR, Padilla IT, Pessah IN, Molinski TF, Fruen BR, Allen PD, Perez CF. Ablation of skeletal muscle triadin impairs FKBP12/RyR1 channel interactions essential for maintaining resting cytoplasmic Ca2+. J Biol Chem 2010; 285:38453-62. [PMID: 20926377 DOI: 10.1074/jbc.m110.164525] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previously, we have shown that lack of expression of triadins in skeletal muscle cells results in significant increase of myoplasmic resting free Ca(2+) ([Ca(2+)](rest)), suggesting a role for triadins in modulating global intracellular Ca(2+) homeostasis. To understand this mechanism, we study here how triadin alters [Ca(2+)](rest), Ca(2+) release, and Ca(2+) entry pathways using a combination of Ca(2+) microelectrodes, channels reconstituted in bilayer lipid membranes (BLM), Ca(2+), and Mn(2+) imaging analyses of myotubes and RyR1 channels obtained from triadin-null mice. Unlike WT cells, triadin-null myotubes had chronically elevated [Ca(2+)](rest) that was sensitive to inhibition with ryanodine, suggesting that triadin-null cells have increased basal RyR1 activity. Consistently, BLM studies indicate that, unlike WT-RyR1, triadin-null channels more frequently display atypical gating behavior with multiple and stable subconductance states. Accordingly, pulldown analysis and fluorescent FKBP12 binding studies in triadin-null muscles revealed a significant impairment of the FKBP12/RyR1 interaction. Mn(2+) quench rates under resting conditions indicate that triadin-null cells also have higher Ca(2+) entry rates and lower sarcoplasmic reticulum Ca(2+) load than WT cells. Overexpression of FKBP12.6 reverted the null phenotype, reducing resting Ca(2+) entry, recovering sarcoplasmic reticulum Ca(2+) content levels, and restoring near normal [Ca(2+)](rest). Exogenous FKBP12.6 also reduced the RyR1 channel P(o) but did not rescue subconductance behavior. In contrast, FKBP12 neither reduced P(o) nor recovered multiple subconductance gating. These data suggest that elevated [Ca(2+)](rest) in triadin-null myotubes is primarily driven by dysregulated RyR1 channel activity that results in part from impaired FKBP12/RyR1 functional interactions and a secondary increased Ca(2+) entry at rest.
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Affiliation(s)
- Jose M Eltit
- Department of Anesthesiology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
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46
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Kampfer AJ, Balog EM. S-Adenosyl-l-methionine Regulation of the Cardiac Ryanodine Receptor Involves Multiple Mechanisms. Biochemistry 2010; 49:7600-14. [DOI: 10.1021/bi100599b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Angela J. Kampfer
- School of Applied Physiology, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Edward M. Balog
- School of Applied Physiology, Georgia Institute of Technology, Atlanta, Georgia 30332
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Abstract
ATP is released from pancreatic acini in response to cholinergic and hormonal stimulation. The same stimuli cause exocytosis of ZG (zymogen granules) and release of digestive enzymes. The aim of the present study was to determine whether ZG stored ATP and to characterize the uptake mechanism for ATP transport into the ZG. ZG were isolated and the ATP content was measured using luciferin/luciferase assays and was related to protein in the sample. The estimate of ATP concentration in freshly isolated granules was 40-120 microM. The ATP uptake had an apparent Km value of 4.9+/-2.1 mM when granules were incubated without Mg2+ and a Km value of 0.47+/-0.05 mM in the presence of Mg2+, both in pH 6.0 buffers. The uptake of ATP was significantly higher at pH 7.2 compared with pH 6.0 solutions. The anion transport blockers DIDS (4,4'-di-isothiocyanostilbene-2,2'-disulfonate) and Evans Blue inhibited ATP transport. Western blot analysis on the ZG showed the presence of VNUT (vesicular nucleotide transporter). Together, these findings indicate that VNUT may be responsible for the ATP uptake into ZG. Furthermore, the present study shows the presence of ATP together with digestive enzymes in ZG. This indicates that co-released ATP would regulate P2 receptors in pancreatic ducts and, thus, ductal secretion, and this would aid delivery of enzymes to the duodenum.
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48
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Philip F, Kadamur G, Silos RG, Woodson J, Ross EM. Synergistic activation of phospholipase C-beta3 by Galpha(q) and Gbetagamma describes a simple two-state coincidence detector. Curr Biol 2010; 20:1327-35. [PMID: 20579885 DOI: 10.1016/j.cub.2010.06.013] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 05/31/2010] [Accepted: 06/01/2010] [Indexed: 01/12/2023]
Abstract
BACKGROUND Receptors that couple to G(i) and G(q) often interact synergistically in cells to elicit cytosolic Ca(2+) transients that are several-fold higher than the sum of those driven by each receptor alone. Such synergism is commonly assumed to be complex, requiring regulatory interaction between components, multiple pathways, or multiple states of the target protein. RESULTS We show that cellular G(i)-G(q) synergism derives from direct supra-additive stimulation of phospholipase C-beta3 (PLC-beta3) by G protein subunits Gbetagamma and Galpha(q), the relevant components of the G(i) and G(q) signaling pathways. No additional pathway or proteins are required. Synergism is quantitatively explained by the classical and simple two-state (inactive<-->active) allosteric mechanism. We show generally that synergistic activation of a two-state enzyme reflects enhanced conversion to the active state when both ligands are bound, not merely the enhancement of ligand affinity predicted by positive cooperativity. The two-state mechanism also explains why synergism is unique to PLC-beta3 among the four PLC-beta isoforms and, in general, why one enzyme may respond synergistically to two activators while another does not. Expression of synergism demands that an enzyme display low basal activity in the absence of ligand and becomes significant only when basal activity is </= 0.1% of maximal. CONCLUSIONS Synergism can be explained by a simple and general mechanism, and such a mechanism sets parameters for its occurrence. Any two-state enzyme is predicted to respond synergistically to multiple activating ligands if, but only if, its basal activity is strongly suppressed.
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Affiliation(s)
- Finly Philip
- Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-9041, USA
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49
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Tugba Durlu-Kandilci N, Ruas M, Chuang KT, Brading A, Parrington J, Galione A. TPC2 proteins mediate nicotinic acid adenine dinucleotide phosphate (NAADP)- and agonist-evoked contractions of smooth muscle. J Biol Chem 2010; 285:24925-32. [PMID: 20547763 PMCID: PMC2915728 DOI: 10.1074/jbc.m110.129833] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Agonists such as those acting at muscarinic receptors are thought to induce contraction of smooth muscle primarily through inositol 1,4,5-trisphosphate production and release of Ca2+ from sarcoplasmic reticulum. However, the additional Ca2+-mobilizing messengers cyclic adenosine diphosphate ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP) may also be involved in this process, the former acting on the sarcoplasmic reticulum, the latter acting on lysosome-related organelles. In this study, we provide the first systematic analysis of the capacity of inositol 1,4,5-trisphosphate, cADPR, and NAADP to cause contraction in smooth muscle. Using permeabilized guinea pig detrusor and taenia caecum, we show that all three Ca2+-mobilizing messengers cause contractions in both types of smooth muscle. We demonstrate that cADPR and NAADP play differential roles in mediating contraction in response to muscarinic receptor activation, with a sizeable role for NAADP and acidic calcium stores in detrusor muscle but not in taenia caecum, underscoring the heterogeneity of smooth muscle signal transduction systems. Two-pore channel proteins (TPCs) have recently been shown to be key components of the NAADP receptor. We show that contractile responses to NAADP were completely abolished, and agonist-evoked contractions were reduced and now became independent of acidic calcium stores in Tpcn2−/− mouse detrusor smooth muscle. Our findings provide the first evidence that TPC proteins mediate a key NAADP-regulated tissue response brought about by agonist activation of a cell surface receptor.
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50
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Wilson GW, Garthwaite J. Hyperpolarization-activated ion channels as targets for nitric oxide signalling in deep cerebellar nuclei. Eur J Neurosci 2010; 31:1935-45. [PMID: 20529121 PMCID: PMC2955965 DOI: 10.1111/j.1460-9568.2010.07226.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Most biological effects of nitric oxide (NO) in the brain are mediated by guanylyl cyclase-coupled NO receptors, whose activation results in increased intracellular cGMP levels. Apart from protein kinase activation little is known about subsequent cGMP signal transduction. In optic nerve axons, hyperpolarization-activated cyclic nucleotide-modulated cation (HCN) channels, which bind cGMP or cAMP directly, were recently suggested to be a target. The aim here was to test this possibility more directly. Neurones of the rat deep cerebellar nuclei were selected for this purpose, their suitability being attested by immunocytochemistry showing that the principal neurones expressed guanylyl cyclase protein and that NO synthase-containing fibres were abundant in the neuropil. Using whole-cell voltage-clamp recording, HCN channels in the neurones were activated in response to isoprenaline and exogenous cAMP but only occasionally did they respond to NO, although exogenous cGMP was routinely effective. With the less invasive sharp microelectrode recording technique, however, exogenous NO modulated the channels reproducibly, as measured by the size of the HCN channel-mediated voltage sag following hyperpolarization. Moreover, NO also blunted the subsequent rebound depolarizing potentials, consistent with it increasing the hyperpolarization-activated current. Optimizing the whole-cell solution to improve the functioning of NO-activated guanylyl cyclase failed to restore NO sensitivity. Minimizing cellular dialysis by using the perforated-patch technique, however, was successful. The results provide evidence that HCN channels are potential downstream mediators of NO signalling in deep cerebellar nuclei neurones and suggest that the more general importance of this transduction pathway may have been overlooked previously because of unsuitable recording methods.
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Affiliation(s)
- Gary W Wilson
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK.
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