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Miotto MC, Weninger G, Dridi H, Yuan Q, Liu Y, Wronska A, Melville Z, Sittenfeld L, Reiken S, Marks AR. Structural analyses of human ryanodine receptor type 2 channels reveal the mechanisms for sudden cardiac death and treatment. SCIENCE ADVANCES 2022; 8:eabo1272. [PMID: 35857850 PMCID: PMC9299551 DOI: 10.1126/sciadv.abo1272] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 06/03/2022] [Indexed: 05/29/2023]
Abstract
Ryanodine receptor type 2 (RyR2) mutations have been linked to an inherited form of exercise-induced sudden cardiac death called catecholaminergic polymorphic ventricular tachycardia (CPVT). CPVT results from stress-induced sarcoplasmic reticular Ca2+ leak via the mutant RyR2 channels during diastole. We present atomic models of human wild-type (WT) RyR2 and the CPVT mutant RyR2-R2474S determined by cryo-electron microscopy with overall resolutions in the range of 2.6 to 3.6 Å, and reaching local resolutions of 2.25 Å, unprecedented for RyR2 channels. Under nonactivating conditions, the RyR2-R2474S channel is in a "primed" state between the closed and open states of WT RyR2, rendering it more sensitive to activation that results in stress-induced Ca2+ leak. The Rycal drug ARM210 binds to RyR2-R2474S, reverting the primed state toward the closed state. Together, these studies provide a mechanism for CPVT and for the therapeutic actions of ARM210.
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Affiliation(s)
- Marco C. Miotto
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY, USA
| | - Gunnar Weninger
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY, USA
| | - Haikel Dridi
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY, USA
| | - Qi Yuan
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY, USA
| | - Yang Liu
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY, USA
| | - Anetta Wronska
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY, USA
| | - Zephan Melville
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY, USA
| | - Leah Sittenfeld
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY, USA
| | - Steven Reiken
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY, USA
| | - Andrew R. Marks
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY, USA
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Yuan Q, Dridi H, Clarke OB, Reiken S, Melville Z, Wronska A, Kushnir A, Zalk R, Sittenfeld L, Marks AR. RyR1-related myopathy mutations in ATP and calcium binding sites impair channel regulation. Acta Neuropathol Commun 2021; 9:186. [PMID: 34809703 PMCID: PMC8609856 DOI: 10.1186/s40478-021-01287-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 10/31/2021] [Indexed: 11/10/2022] Open
Abstract
The type 1 ryanodine receptor (RyR1) is an intracellular calcium (Ca2+) release channel on the sarcoplasmic/endoplasmic reticulum that is required for skeletal muscle contraction. RyR1 channel activity is modulated by ligands, including the activators Ca2+ and ATP. Patients with inherited mutations in RyR1 may exhibit muscle weakness as part of a heterogeneous, complex disorder known as RYR1-related myopathy (RYR1-RM) or more recently termed RYR1-related disorders (RYR1-RD). Guided by high-resolution structures of skeletal muscle RyR1, obtained using cryogenic electron microscopy, we introduced mutations into putative Ca2+ and ATP binding sites and studied the function of the resulting mutant channels. These mutations confirmed the functional significance of the Ca2+ and ATP binding sites identified by structural studies based on the effects on channel regulation. Under normal conditions, Ca2+ activates RyR1 at low concentrations (µM) and inhibits it at high concentrations (mM). Mutations in the Ca2+-binding site impaired both activating and inhibitory regulation of the channel, suggesting a single site for both high and low affinity Ca2+-dependent regulation of RyR1 function. Mutation of residues that interact with the adenine ring of ATP abrogated ATP binding to the channel, whereas mutating residues that interact with the triphosphate tail only affected the degree of activation. In addition, patients with mutations at the Ca2+ or ATP binding sites suffer from muscle weakness, therefore impaired RyR1 channel regulation by either Ca2+ or ATP may contribute to the pathophysiology of RYR1-RM in some patients.
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Muscle Glycogen Metabolism and High-Intensity Exercise Performance: A Narrative Review. Sports Med 2021; 51:1855-1874. [PMID: 33900579 DOI: 10.1007/s40279-021-01475-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/08/2021] [Indexed: 02/06/2023]
Abstract
Muscle glycogen is the main substrate during high-intensity exercise and large reductions can occur after relatively short durations. Moreover, muscle glycogen is stored heterogeneously and similarly displays a heterogeneous and fiber-type specific depletion pattern with utilization in both fast- and slow-twitch fibers during high-intensity exercise, with a higher degradation rate in the former. Thus, depletion of individual fast- and slow-twitch fibers has been demonstrated despite muscle glycogen at the whole-muscle level only being moderately lowered. In addition, muscle glycogen is stored in specific subcellular compartments, which have been demonstrated to be important for muscle function and should be considered as well as global muscle glycogen availability. In the present review, we discuss the importance of glycogen metabolism for single and intermittent bouts of high-intensity exercise and outline possible underlying mechanisms for a relationship between muscle glycogen and fatigue during these types of exercise. Traditionally this relationship has been attributed to a decreased ATP resynthesis rate due to inadequate substrate availability at the whole-muscle level, but emerging evidence points to a direct coupling between muscle glycogen and steps in the excitation-contraction coupling including altered muscle excitability and calcium kinetics.
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Wang W, Yu H, Li T, Li L, Zhang G, Liu Z, Huang T, Zhang Y. Comparative Proteomics Analyses of Pollination Response in Endangered Orchid Species Dendrobium Chrysanthum. Int J Mol Sci 2017; 18:ijms18122496. [PMID: 29168730 PMCID: PMC5751103 DOI: 10.3390/ijms18122496] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 11/15/2017] [Accepted: 11/17/2017] [Indexed: 12/24/2022] Open
Abstract
Pollination is a crucial stage in plant reproductive process. The self-compatibility (SC) and self-incompatibility (SI) mechanisms determined the plant genetic diversity and species survival. D. chrysanthum is a highly valued ornamental and traditional herbal orchid in Asia but has been declared endangered. The sexual reproduction in D. chrysanthum relies on the compatibility of pollination. To provide a better understanding of the mechanism of pollination, the differentially expressed proteins (DEP) between the self-pollination (SP) and cross-pollination (CP) pistil of D. chrysanthum were investigated using proteomic approaches—two-dimensional electrophoresis (2-DE) coupled with tandem mass spectrometry technique. A total of 54 DEP spots were identified in the two-dimensional electrophoresis (2-DE) maps between the SP and CP. Gene ontology analysis revealed an array of proteins belonging to following different functional categories: metabolic process (8.94%), response to stimulus (5.69%), biosynthetic process (4.07%), protein folding (3.25%) and transport (3.25%). Identification of these DEPs at the early response stage of pollination will hopefully provide new insights in the mechanism of pollination response and help for the conservation of the orchid species.
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Affiliation(s)
- Wei Wang
- Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China.
| | - Hongyang Yu
- Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China.
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Tinghai Li
- Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China.
| | - Lexing Li
- Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China.
| | - Guoqiang Zhang
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, the National Orchid Conservation Center of China and the Orchid Conservation & Research Center of Shenzhen, Shenzhen 518114, China.
| | - Zhongjian Liu
- Shenzhen Key Laboratory for Orchid Conservation and Utilization, the National Orchid Conservation Center of China and the Orchid Conservation & Research Center of Shenzhen, Shenzhen 518114, China.
| | - Tengbo Huang
- Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China.
| | - Yongxia Zhang
- Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China.
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Meissner G. The structural basis of ryanodine receptor ion channel function. J Gen Physiol 2017; 149:1065-1089. [PMID: 29122978 PMCID: PMC5715910 DOI: 10.1085/jgp.201711878] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 10/12/2017] [Indexed: 01/25/2023] Open
Abstract
Large-conductance Ca2+ release channels known as ryanodine receptors (RyRs) mediate the release of Ca2+ from an intracellular membrane compartment, the endo/sarcoplasmic reticulum. There are three mammalian RyR isoforms: RyR1 is present in skeletal muscle; RyR2 is in heart muscle; and RyR3 is expressed at low levels in many tissues including brain, smooth muscle, and slow-twitch skeletal muscle. RyRs form large protein complexes comprising four 560-kD RyR subunits, four ∼12-kD FK506-binding proteins, and various accessory proteins including calmodulin, protein kinases, and protein phosphatases. RyRs share ∼70% sequence identity, with the greatest sequence similarity in the C-terminal region that forms the transmembrane, ion-conducting domain comprising ∼500 amino acids. The remaining ∼4,500 amino acids form the large regulatory cytoplasmic "foot" structure. Experimental evidence for Ca2+, ATP, phosphorylation, and redox-sensitive sites in the cytoplasmic structure have been described. Exogenous effectors include the two Ca2+ releasing agents caffeine and ryanodine. Recent work describing the near atomic structures of mammalian skeletal and cardiac muscle RyRs provides a structural basis for the regulation of the RyRs by their multiple effectors.
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Affiliation(s)
- Gerhard Meissner
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, NC
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des Georges A, Clarke OB, Zalk R, Yuan Q, Condon KJ, Grassucci RA, Hendrickson WA, Marks AR, Frank J. Structural Basis for Gating and Activation of RyR1. Cell 2016; 167:145-157.e17. [PMID: 27662087 DOI: 10.1016/j.cell.2016.08.075] [Citation(s) in RCA: 276] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 06/08/2016] [Accepted: 08/30/2016] [Indexed: 10/21/2022]
Abstract
The type-1 ryanodine receptor (RyR1) is an intracellular calcium (Ca(2+)) release channel required for skeletal muscle contraction. Here, we present cryo-EM reconstructions of RyR1 in multiple functional states revealing the structural basis of channel gating and ligand-dependent activation. Binding sites for the channel activators Ca(2+), ATP, and caffeine were identified at interdomain interfaces of the C-terminal domain. Either ATP or Ca(2+) alone induces conformational changes in the cytoplasmic assembly ("priming"), without pore dilation. In contrast, in the presence of all three activating ligands, high-resolution reconstructions of open and closed states of RyR1 were obtained from the same sample, enabling analyses of conformational changes associated with gating. Gating involves global conformational changes in the cytosolic assembly accompanied by local changes in the transmembrane domain, which include bending of the S6 transmembrane segment and consequent pore dilation, displacement, and deformation of the S4-S5 linker and conformational changes in the pseudo-voltage-sensor domain.
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Affiliation(s)
- Amédée des Georges
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Oliver B Clarke
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Ran Zalk
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Qi Yuan
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Kendall J Condon
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Robert A Grassucci
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Wayne A Hendrickson
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA.
| | - Andrew R Marks
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA; Department of Medicine, Columbia University, New York, NY 10032, USA; Wu Center for Molecular Cardiology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
| | - Joachim Frank
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Department of Biological Sciences, Columbia University, New York, NY 10032, USA.
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Witherspoon JW, Meilleur KG. Review of RyR1 pathway and associated pathomechanisms. Acta Neuropathol Commun 2016; 4:121. [PMID: 27855725 PMCID: PMC5114830 DOI: 10.1186/s40478-016-0392-6] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 11/02/2016] [Indexed: 02/04/2023] Open
Abstract
Ryanodine receptor isoform-1 (RyR1) is a major calcium channel in skeletal muscle important for excitation-contraction coupling. Mutations in the RYR1 gene yield RyR1 protein dysfunction that manifests clinically as RYR1-related congenital myopathies (RYR1-RM) and/or malignant hyperthermia susceptibility (MHS). Individuals with RYR1-RM and/or MHS exhibit varying symptoms and severity. The symptoms impair quality of life and put patients at risk for early mortality, yet the cause of varying severity is not well understood. Currently, there is no Food and Drug Administration (FDA) approved treatment for RYR1-RM. Discovery of effective treatments is therefore critical, requiring knowledge of the RyR1 pathway. The purpose of this review is to compile work published to date on the RyR1 pathway and to implicate potential regions as targets for treatment. The RyR1 pathway is comprised of protein-protein interactions, protein-ligand interactions, and post-translational modifications, creating an activation/regulatory macromolecular complex. Given the complexity of this pathway, we divided these interactions and modifications into six regulatory groups. Three of several RyR1 interacting proteins, FK506-binding protein 12 (FKBP12), triadin, and calmodulin, were identified as playing important roles across all groups and may serve as promising target sites for treatment. Also, variability in disease severity may be influenced by prolongation or hyperactivity of post-translational modifications resulting from RyR1 dysfunction.
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Liu SY, Xu JJ, Minobe E, Gao QH, Feng R, Zhao MM, Guo F, Yang L, Hao LY, Kameyama M. Nucleotides maintain the activity of Cav1.2 channels in guinea-pig ventricular myocytes. Biochem Biophys Res Commun 2015; 460:813-8. [PMID: 25824040 DOI: 10.1016/j.bbrc.2015.03.111] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 03/20/2015] [Indexed: 11/15/2022]
Abstract
The activity of Cav1.2 Ca(2+) channels is maintained in the presence of calmodulin and ATP, even in cell-free patches, and thus a channel ATP-binding site has been suggested. In this study, we examined whether other nucleotides, such as GTP, UTP, CTP, ADP and AMP, could be substituted for ATP in guinea-pig ventricular myocytes. We found that all the nucleotides tested could re-prime the Ca(2+) channels in the presence of 1 μM calmodulin in the inside-out mode. The order of efficacy was ATP > GTP > UTP > ADP > CTP ≈ AMP. Thus, the presumed nucleotide-binding site in the channel seemed to favor a purine rather than pyrimidine base and a triphosphate rather than a di- or mono-phosphate group. Furthermore, a high concentration (10 mM) of GTP, UTP, CTP, ADP and AMP had inhibitory effects on the channel activity. These results provide information on the putative nucleotide-binding site(s) in Cav1.2 Ca(2+) channels.
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Affiliation(s)
- Shu-yuan Liu
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan
| | - Jian-jun Xu
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan
| | - Etsuko Minobe
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan
| | - Qing-hua Gao
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China
| | - Rui Feng
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China
| | - Mei-mi Zhao
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China
| | - Feng Guo
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China
| | - Lei Yang
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan
| | - Li-ying Hao
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China.
| | - Masaki Kameyama
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
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Hanson MG, Wilde JJ, Moreno RL, Minic AD, Niswander L. Potassium dependent rescue of a myopathy with core-like structures in mouse. eLife 2015; 4. [PMID: 25564733 PMCID: PMC4309926 DOI: 10.7554/elife.02923] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 01/07/2015] [Indexed: 01/24/2023] Open
Abstract
Myopathies decrease muscle functionality. Mutations in ryanodine receptor 1 (RyR1) are often associated with myopathies with microscopic core-like structures in the muscle fiber. In this study, we identify a mouse RyR1 model in which heterozygous animals display clinical and pathological hallmarks of myopathy with core-like structures. The RyR1 mutation decreases sensitivity to activated calcium release and myoplasmic calcium levels, subsequently affecting mitochondrial calcium and ATP production. Mutant muscle shows a persistent potassium leak and disrupted expression of regulators of potassium homeostasis. Inhibition of KATP channels or increasing interstitial potassium by diet or FDA-approved drugs can reverse the muscle weakness, fatigue-like physiology and pathology. We identify regulators of potassium homeostasis as biomarkers of disease that may reveal therapeutic targets in human patients with myopathy of central core disease (CCD). Altogether, our results suggest that amelioration of potassium leaks through potassium homeostasis mechanisms may minimize muscle damage of myopathies due to certain RyR1 mutations.
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Affiliation(s)
- M Gartz Hanson
- Department of Pediatrics, University of Colorado, Anschutz Medical Campus, Aurora, United States
| | - Jonathan J Wilde
- Department of Pediatrics, University of Colorado, Anschutz Medical Campus, Aurora, United States
| | - Rosa L Moreno
- Department of Physiology, University of Colorado, Anschutz Medical Campus, Aurora, United States
| | - Angela D Minic
- Department of Pediatrics, University of Colorado, Anschutz Medical Campus, Aurora, United States
| | - Lee Niswander
- Department of Pediatrics, University of Colorado, Anschutz Medical Campus, Aurora, United States
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Martin-Cano FE, Camello-Almaraz C, Acuña-Castroviejo D, Pozo MJ, Camello PJ. Age-related changes in mitochondrial function of mouse colonic smooth muscle: beneficial effects of melatonin. J Pineal Res 2014; 56:163-74. [PMID: 24313280 DOI: 10.1111/jpi.12109] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 12/03/2013] [Indexed: 01/13/2023]
Abstract
Aging is a multifactorial process that involves biochemical, structural, and functional changes in mitochondria. The ability of melatonin to palliate the alterations induced by aging is based on its chronobiologic, antioxidant, and mitochondrial effects. There is little information about the effects of melatonin on the in situ mitochondrial network of aging cells and its physiological implications. We have studied the ability of melatonin to prevent the functional alterations of in situ mitochondria of smooth muscle cells and its impact on contractility. Mitochondrial membrane potential was recorded in isolated colonic smooth muscle cells from young mice (3 month old), aged mice (22-24-month old), and aged mice treated with melatonin (starting at 14-month age). Aging induced a partial mitochondrial depolarization in resting conditions and reduced the depolarizing response to cellular stimulation. Use of oligomycin indicated that aging enhanced the resting activity of the mitochondrial ATP synthase, whereas in young cells, the enzyme operated mainly in reverse mode. Melatonin treatment prevented all these changes. Aging reduced both spontaneous and stimulated contraction of colonic strips and shifted the metabolic dependence of contraction from mitochondria to glycolysis, as indicated the use of mitochondrial and glycolysis inhibitors. These functional alterations were also palliated by melatonin treatment. Aging effects were not related to a decrease in Ca2+ store mobilization, because this was enhanced in aged cells and restored by melatonin. In conclusion, melatonin prevents the age induced in situ mitochondrial potential alterations in smooth muscle cells and the associated changes in contractility and metabolism.
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Affiliation(s)
- Francisco E Martin-Cano
- Department of Physiology, Faculty of Nursing and Occupational Therapy, University of Extremadura, Cáceres, Spain
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Blayney L, Beck K, MacDonald E, D'Cruz L, Nomikos M, Griffiths J, Thanassoulas A, Nounesis G, Lai FA. ATP interacts with the CPVT mutation-associated central domain of the cardiac ryanodine receptor. Biochim Biophys Acta Gen Subj 2013; 1830:4426-32. [PMID: 23747301 DOI: 10.1016/j.bbagen.2013.05.038] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 05/20/2013] [Accepted: 05/29/2013] [Indexed: 02/03/2023]
Abstract
BACKGROUND This study was designed to determine whether the cardiac ryanodine receptor (RyR2) central domain, a region associated with catecholamine polymorphic ventricular tachycardia (CPVT) mutations, interacts with the RyR2 regulators, ATP and the FK506-binding protein 12.6 (FKBP12.6). METHODS Wild-type (WT) RyR2 central domain constructs (G(2236)to G(2491)) and those containing the CPVT mutations P2328S and N2386I, were expressed as recombinant proteins. Folding and stability of the proteins were examined by circular dichroism (CD) spectroscopy and guanidine hydrochloride chemical denaturation. RESULTS The far-UV CD spectra showed a soluble stably-folded protein with WT and mutant proteins exhibiting a similar secondary structure. Chemical denaturation analysis also confirmed a stable protein for both WT and mutant constructs with similar two-state unfolding. ATP and caffeine binding was measured by fluorescence spectroscopy. Both ATP and caffeine bound with an EC50 of ~200-400μM, and the affinity was the same for WT and mutant constructs. Sequence alignment with other ATP binding proteins indicated the RyR2 central domain contains the signature of an ATP binding pocket. Interaction of the central domain with FKBP12.6 was tested by glutaraldehyde cross-linking and no association was found. CONCLUSIONS The RyR2 central domain, expressed as a 'correctly' folded recombinant protein, bound ATP in accord with bioinformatics evidence of conserved ATP binding sequence motifs. An interaction with FKBP12.6 was not evident. CPVT mutations did not disrupt the secondary structure nor binding to ATP. GENERAL SIGNIFICANCE Part of the RyR2 central domain CPVT mutation cluster, can be expressed independently with retention of ATP binding.
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Affiliation(s)
- Lynda Blayney
- Institute of Molecular and Experimental Medicine, Cardiff University, Cardiff, UK.
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