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Takayoshi Kato, Takeshi Yamamoto, Yoshihide Nakamura, Takuma Nanno, Go Fukui, Yoko Sufu, Yoriomi Hamada, Takako Maeda, Shigehiko Nishimura, Hironori Ishiguchi, Wakako Murakami, Masakazu Fukuda, Xiaojuan Xu, Akihiro Hino, Makoto Ono, Tetsuro Oda, Shinichi Okuda, Shigeki Kobayashi, Noritaka Koseki, Hiroyuki Kyushiki, Masafumi Yano
BACKGROUND: Calmodulin (CaM) is a key modulator of the channel gating function of the ryanodine receptor (RyR). OBJECTIVE: Here, we investigated the pathogenic role of RyR-bound CaM in diastolic Ca(2+) leakage from the sarcoplasmic reticulum and arrhythmogenesis in pressure-overloaded heart failure. METHODS: Pressure overload was induced in 12-week-old mice by transverse aortic constriction (TAC) using a 27-gauge needle. RESULTS: TAC operation for 8 weeks produced a significant increase in the left ventricular end-diastolic diameter, and frequent occurrence of lethal arrhythmias after infusion of epinephrine and caffeine in TAC mice...
October 19, 2016: Heart Rhythm: the Official Journal of the Heart Rhythm Society
Kenichi Sasaki, Takeru Makiyama, Yoshinori Yoshida, Yimin Wuriyanghai, Tsukasa Kamakura, Suguru Nishiuchi, Mamoru Hayano, Takeshi Harita, Yuta Yamamoto, Hirohiko Kohjitani, Sayako Hirose, Jiarong Chen, Mihoko Kawamura, Seiko Ohno, Hideki Itoh, Ayako Takeuchi, Satoshi Matsuoka, Masaru Miura, Naokata Sumitomo, Minoru Horie, Shinya Yamanaka, Takeshi Kimura
INTRODUCTION: Human induced pluripotent stem cells (hiPSCs) offer a unique opportunity for disease modeling. However, it is not invariably successful to recapitulate the disease phenotype because of the immaturity of hiPSC-derived cardiomyocytes (hiPSC-CMs). The purpose of this study was to establish and analyze iPSC-based model of catecholaminergic polymorphic ventricular tachycardia (CPVT), which is characterized by adrenergically mediated lethal arrhythmias, more precisely using electrical pacing that could promote the development of new pharmacotherapies...
2016: PloS One
Robyn T Rebbeck, Maram M Essawy, Florentin R Nitu, Benjamin D Grant, Gregory D Gillispie, David D Thomas, Donald M Bers, Razvan L Cornea
Using time-resolved fluorescence resonance energy transfer (FRET), we have developed and validated the first high-throughput screening (HTS) method to discover compounds that modulate an intracellular Ca(2+) channel, the ryanodine receptor (RyR), for therapeutic applications. Intracellular Ca(2+) regulation is critical for striated muscle function, and RyR is a central player. At resting [Ca(2+)], an increased propensity of channel opening due to RyR dysregulation is associated with severe cardiac and skeletal myopathies, diabetes, and neurological disorders...
October 19, 2016: Journal of Biomolecular Screening
Julia O Reynolds, Ann P Quick, Qiongling Wang, David L Beavers, Leonne E Philippen, Jordan Showell, Giselle Barreto-Torres, Donna J Thuerauf, Shirin Doroudgar, Christopher C Glembotski, Xander H T Wehrens
BACKGROUND: Junctophilin-2 (JPH2) is the primary structural protein for the coupling of transverse (T)-tubule associated cardiac L-type Ca channels and type-2 ryanodine receptors on the sarcoplasmic reticulum within junctional membrane complexes (JMCs) in cardiomyocytes. Effective signaling between these channels ensures adequate Ca-induced Ca release required for normal cardiac contractility. Disruption of JMC subcellular domains, a common feature of failing hearts, has been attributed to JPH2 downregulation...
October 8, 2016: International Journal of Cardiology
Yusuke Fujii, Hideki Itoh, Seiko Ohno, Takashi Murayama, Nagomi Kurebayashi, Hisaaki Aoki, Malorie Blancard, Yoshihisa Nakagawa, Satoshi Yamamoto, Yumie Matsui, Mari Ichikawa, Keiko Sonoda, Tomoya Ozawa, Kimie Ohkubo, Ichiro Watanabe, Pascale Guicheney, Minoru Horie
BACKGROUND: Ventricular fibrillation (VF) may be caused by premature ventricular contractions (PVCs) whose coupling intervals are under 300ms, a characteristic of scTdP. OBJECTIVE: The purpose of this study is to analyze the underlying RyR2 variants in patients with the short-coupled variant of torsade de pointes (scTdP). METHODS: Seven patients with scTdP (34±12 years old, 3 females) were enrolled in this study. The RyR2 gene was screened by targeted gene sequencing methods, and variant minor allele frequency (MAF) was confirmed in three databases, and the pathogenicity was investigated in multiple in silico tools...
October 15, 2016: Heart Rhythm: the Official Journal of the Heart Rhythm Society
Yong Xie, Zhen-Jie Gu, Mao-Xiong Wu, Tu-Cheng Huang, Jing-Song Ou, Huiping-Son Ni, Mao-Huan Lin, Wo-Liang Yuan, Jing-Feng Wang, Yang-Xin Chen
AIMS: Adverse cardiovascular effects induced by peroxisome proliferator activator receptor-γ (PPAR-γ) activation were observed in clinical setting. But the underlying mechanism is unclear. Now, transgenic mice with cardiac specific peroxisome proliferator activator receptor-γ overexpression (TG-PPAR-γ) were used to explore the possible mechanisms. MATERIALS AND METHODS: Cardiac tissues from TG-PPAR-γ mice, a PPAR-γ over-expressing human cardiomyocyte line AC16 cell, and PPAR-γ agonist-treated primary cardiomyocytes were used to evaluate the expression of cardiac calcium regulatory proteins as sarcoplasmic reticulum Ca(2+) ATPase, Na(+)/Ca(2+)exchanger 1, ryanodine receptor 2 and phospholamban...
October 13, 2016: Life Sciences
Yohannes Shiferaw
Spontaneous calcium (Ca) waves in cardiac myocytes are known to underlie a wide range of cardiac arrhythmias. However, it is not understood which physiological parameters determine the onset of waves. In this study, we explore the relationship between Ca signaling between ion channels and the nucleation of Ca waves. In particular, we apply a master equation approach to analyze the stochastic interaction between neighboring clusters of ryanodine receptor (RyR) channels. Using this analysis, we show that signaling between clusters can be described as a barrier hopping process with exponential sensitivity to system parameters...
September 2016: Physical Review. E
Fábio V G Campanha, Denise Perone, Dijon H S de Campos, Renata de A M Luvizotto, Maria T De Síbio, Miriane de Oliveira, Regiane M C Olimpio, Fernanda C F Moretto, Carlos R Padovani, Gláucia M F S Mazeto, Antonio C Cicogna, Célia R Nogueira
Objective: The current study was aimed at analyzing sarcoplasmic reticulum Ca2+ ATPase (Serca2) and ryanodine receptor type 2 (Ryr2) gene expression in rats subjected to surgery that induced HF and were subsequently treated with T4 using physiological doses. Materials and methods: HF was induced in 18 male Wistar rats by clipping the ascending thoracic aorta to generate aortic stenosis (HFS group), while the control group (9-sham) underwent thoracotomy. After 21 weeks, the HFS group was subdivided into two subgroups...
October 10, 2016: Archives of Endocrinology and Metabolism
Zhichao Xiao, Wenting Guo, Bo Sun, Donald J Hunt, Jinhong Wei, Yingjie Liu, Yundi Wang, Ruiwu Wang, Peter P Jones, Thomas G Back, S R Wayne Chen
Recent three-dimensional structural studies reveal that the Central domain of ryanodine receptor (RyR) serves as a transducer that converts long-range conformational changes into the gating of the channel pore. Interestingly, the Central domain encompasses one of the mutation hotspots (corresponding to amino acid residues 3778-4201) that contains a number of cardiac RyR (RyR2) mutations associated with catecholaminergic polymorphic ventricular tachycardia (CPVT) and atrial fibrillation (AF). However, the functional consequences of these Central domain RyR2 mutations are not well understood...
October 12, 2016: Journal of Biological Chemistry
Kaivan Khavandi, Rachael L Baylie, Sarah A Sugden, Majid Ahmed, Viktoria Csato, Philip Eaton, David C Hill-Eubanks, Adrian D Bonev, Mark T Nelson, Adam S Greenstein
Activation of Ca(2+)-sensitive, large-conductance potassium (BK) channels in vascular smooth muscle cells (VSMCs) by local, ryanodine receptor-mediated Ca(2+) signals (Ca(2+) sparks) acts as a brake on pressure-induced (myogenic) vasoconstriction-a fundamental mechanism that regulates blood flow in small resistance arteries. We report that physiological intraluminal pressure within resistance arteries activated cGMP-dependent protein kinase (PKG) in VSMCs through oxidant-induced formation of an intermolecular disulfide bond between cysteine residues...
October 11, 2016: Science Signaling
Ann P Quick, Qiongling Wang, Leonne E Philippen, Giselle Barreto-Torres, David Y Chiang, David L Beavers, Guoliang Wang, Maha Khalid, Julia O Reynolds, Hannah M Campbell, Jordan Showell, Mark D McCauley, Arjen Scholten, Xander H Wehrens
RATIONALE: Junctional membrane complexes (JMC) in myocytes are critical microdomains, in which excitation-contraction coupling occurs. Structural and functional disruption of JMCs underlies contractile dysfunction in failing hearts. However, the role of newly identified JMC protein striated muscle preferentially expressed gene (SPEG) remains unclear. OBJECTIVE: To determine the role of SPEG in healthy and failing adult hearts. MMethods and Results: Proteomic analysis of immunoprecipatated JMC-proteins ryanodine receptor type-2 (RyR2) and junctophilin-2 (JPH2) followed by mass spectrometry identified the serine-threonine kinase SPEG as the only novel binding partner for both proteins...
October 11, 2016: Circulation Research
Donald M Bers
No abstract text is available yet for this article.
October 7, 2016: Heart Rhythm: the Official Journal of the Heart Rhythm Society
Ryan L O'Hare Doig, Carole A Bartlett, Nicole M Smith, Stuart I Hodgetts, Sarah A Dunlop, Livia Hool, Melinda Fitzgerald
Combinations of Ca(2+) channel inhibitors have been proposed as an effective means to prevent excess Ca(2+) flux and death of neurons and glia following neurotrauma in vivo. However, it is not yet known if beneficial outcomes such as improved viability have been due to direct effects on intracellular Ca(2+) concentrations. Here, the effects of combinations of Lomerizine (Lom), YM872, memantine and/or oxATP to block voltage gated Ca(2+) channels, Ca(2+) permeable AMPA receptors, NMDA receptors and purinergic P2X7 receptors (P2X7R) respectively, on Ca(2+) concentration and viability of primary mixed cortical cultures exposed to hydrogen peroxide (H2O2) insult, were assessed...
October 7, 2016: Neuroscience
Zhangjiang He, Linli Luo, Nemat O Keyhani, Xiaodong Yu, Shenghua Ying, Yongjun Zhang
Protein O-mannosyltransferases (Pmts) belong to a highly conserved protein family responsible for the initiation of O-glycosylation of many proteins. Pmts contain one dolichyl-phosphate-mannose-protein mannosyltransferases (PMT) domain and three MIR motifs (mannosyltransferase, inositol triphosphate, and ryanodine receptor) that are essential for activity in yeast. We report that in the insect fungal pathogen, Beauveria bassiana, deletion of the C-terminal Pmt1 MIR-containing region (Pmt1∆ (311-902)) does not alter O-mannosyltransferase activity, but does increase total cell wall protein O-mannosylation levels and results in phenotypic changes in fungal development and cell wall stability...
October 8, 2016: Applied Microbiology and Biotechnology
Elzbieta Zieminska, Jacek Lenart, Dominik Diamandakis, Jerzy W Lazarewicz
Using primary cultures of rat cerebellar granule cells (CGC) we examined the role of calcium transients induced by tetrabromobisphenol A (TBBPA) in triggering oxidative stress and cytotoxicity. CGC were exposed for 30 min to 10 or 25 µM TBBPA. Changes in intracellular calcium concentration ([Ca(2+)]i), in the production of reactive oxygen species (ROS), and in the potential of mitochondria (∆Ψm) were measured fluorometrically during the exposure. The intracellular glutathione (GSH) and catalase activity were determined after the incubation; cell viability was evaluated 24 h later...
October 7, 2016: Neurochemical Research
R M Downs, M A Hughes, S T Kinsey, M C Johnson, B L Baumgarner
Caffeine is a widely consumed stimulant that has previously been shown to promote cytotoxic stress and even cell death in numerous mammalian cell lines. Thus far there is little information available regarding the toxicity of caffeine in skeletal muscle cells. Our preliminary data revealed that treating C2C12 myotubes with 5 mM caffeine for 6 h increased nuclear fragmentation and reduced basal and maximal oxygen consumption rate (OCR) in skeletal myotubes. The purpose of this study was to further elucidate the pathways by which caffeine increased cell death and reduced mitochondrial respiration...
October 4, 2016: Biochemical and Biophysical Research Communications
Seigo Sugimachi, Yukihisa Matsumoto, Makoto Mizunami, Jiro Okada
Caffeine is a plant-derived alkaloid that is generally known as a central nervous system (CNS) stimulant. In order to examine the effects of caffeine on higher CNS functions in insects, we used an appetitive olfactory learning paradigm for the cricket Gryllus bimaculatus. Crickets can form significant long-term memories (LTMs) after repetitive training sessions, during which they associate a conditioned stimulus (CS: odor) with an unconditioned stimulus (US: reward). Administration of hemolymphal injections of caffeine established LTM after only single-trial conditioning over a wide range of caffeine dosages (1...
October 2016: Zoological Science
John E Casida, Kathleen A Durkin
Pesticide researchers are students of nature, and each new compound and mechanism turns a page in the ever-expanding encyclopedia of life. Pesticides are both probes to learn about life processes and tools for pest management to facilitate food production and enhance health. In contrast to some household and industrial chemicals, pesticides are assumed to be hazardous to health and the environment until proven otherwise. About a thousand current pesticides working by more than 100 different mechanisms have helped understand many processes and coupled events...
October 7, 2016: Chemical Research in Toxicology
Wei Peng, Huaizong Shen, Jianping Wu, Wenting Guo, Xiaojing Pan, Ruiwu Wang, S R Wayne Chen, Nieng Yan
RyR2 is a high-conductance intracellular Ca(2+) channel that controls the release of Ca(2+) from the sarco(endo)plasmic reticulum of a variety of cells. Here, we report the structures of RyR2 from porcine heart in both the open and closed states at near atomic resolutions determined using single-particle electron cryomicroscopy. Structural comparison reveals breathing motion of the overall cytoplasmic region resulted from the interdomain movements of amino-terminal domains (NTDs), Helical domains, and Handle domains, whereas little intradomain shifts are observed in these armadillo repeats-containing domains...
September 22, 2016: Science
Saptarshi Mukherjee, N Lowri Thomas, Alan J Williams
The flow of ions through membrane channels is precisely regulated by gates. The architecture and function of these elements have been studied extensively, shedding light on the mechanisms underlying gating. Recent investigations have focused on ion occupancy of the channel's selectivity filter and its ability to alter gating, with most studies involving prokaryotic K(+) channels. Some studies used large quaternary ammonium blocker molecules to examine the effects of altered ionic flux on gating. However, the absence of blocking events that are visibly distinct from closing events in K(+) channels makes unambiguous interpretation of data from single channel recordings difficult...
October 5, 2016: Scientific Reports
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