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One or more keywords matched the following properties of Yamaguchi, Naohiro
overview Calcium ions play critical roles in intracellular signaling of a variety of cells. In cardiac and skeletal muscle, transiently elevated Ca2+ concentrations during muscle action potentials initiate muscle contraction. In my laboratory we are studying how these Ca2+ transients are well regulated and how aberrant intracellular calcium homeostasis causes diseases in the cardiac and skeletal muscle. (1) Heart failure is one of the leading causes of death in humans. In cardiac pathological studies, dysfunction of calcium transporting proteins is found to be implicated in cardiac hypertrophy and arrhythmia often resulting in heart failure. During an cardiac action potential Ca2+ influx through voltage-dependent L-type Ca2+ channels (Cav1.2) activates Ca2+ release channels (ryanodine receptors type2: RyR2s), which release Ca2+ from the sarcoplasmic reticulum (SR) by Ca2+-induced Ca2+ release (CICR). I am currently interested in regulation mechanism of RyR2 and Cav1.2 by calmodulin, a ubiquitous cytoplasmic Ca2+ binding protein. During cardiac muscle contraction, elevated cytoplasmic Ca2+ and Ca2+-bound calmodulin regulate a number of proteins including these ion channels by a feedback mechanism. To address functional significance of calmodulin regulation of RyR2 and Cav1.2, I am characterizing wild type and mutant channels in vitro (heterologous cell expression) and in vivo (mutant mouse model). I have recently generated a genetically modified mouse impaired in calmodulin regulation of RyR2. Prolonged SR Ca2+ release was measured in cardiomyocytes isolated from mutant mouse hearts. In addition, cardiac hypertrophy and early death of the mutant mice were observed. This mutant mouse is a powerful model to analyze how abnormal Ca2+ homeostasis activates signaling pathways underlying cardiac hypertrophy. (2) Intracellular Ca2+ transients in skeletal muscle are mediated by type1 ryanodine receptors calcium release channels (RyR1s). Missense mutations in RyR1 are associated with human skeletal myopathies including central core disease (CCD). A well-known molecular mechanism is that RyR1 mutations increase affinities for channel agonist, therefore causing intracellular Ca2+ overload. We hypothesize that an alternative mechanism underlying the skeletal myopathies is impairment of inhibitory regulation of RyR1. We recently have identified RyR domains involved in this Ca2+-dependent inactivation. We are characterizing biochemical and biophysical properties of the RyR1 harboring disease-associated point mutations in the identified domains. These studies are expected to provide a novel insight in dysfunctional Ca2+ homeostasis in skeletal pathology.
One or more keywords matched the following items that are connected to Yamaguchi, Naohiro
Item TypeName
Concept Muscle, Skeletal
Academic Article Different regions in skeletal and cardiac muscle ryanodine receptors are involved in transducing the functional effects of calmodulin.
Academic Article Regulation of the cardiac muscle ryanodine receptor by O(2) tension and S-nitrosoglutathione.
Academic Article Modulation of sarcoplasmic reticulum Ca2+ release in skeletal muscle expressing ryanodine receptor impaired in regulation by calmodulin and S100A1.
Academic Article Clinical and functional effects of a deletion in a COOH-terminal lumenal loop of the skeletal muscle ryanodine receptor.
Academic Article Characterization of recombinant skeletal muscle (Ser-2843) and cardiac muscle (Ser-2809) ryanodine receptor phosphorylation mutants.
Academic Article Characterization of recessive RYR1 mutations in core myopathies.
Academic Article Single channel properties of heterotetrameric mutant RyR1 ion channels linked to core myopathies.
Academic Article Thermodynamics of calmodulin binding to cardiac and skeletal muscle ryanodine receptor ion channels.
Academic Article Mass spectrometric analysis and mutagenesis predict involvement of multiple cysteines in redox regulation of the skeletal muscle ryanodine receptor ion channel complex.
Academic Article Malignant hyperthermia-associated mutations in the S2-S3 cytoplasmic loop of type 1 ryanodine receptor calcium channel impair calcium-dependent inactivation.
Academic Article Ca2+-mediated activation of the skeletal-muscle ryanodine receptor ion channel.
Academic Article A central core disease mutation in the Ca2+-binding site of skeletal muscle ryanodine receptor impairs single-channel regulation.
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  • Muscle Skeletal