title: Regucalcin increases Ca2+-ATPase activity in the heart mitochondria of normal and regucalcin transgenic rats.
abstract: The role of regucalcin, a regulatory protein in intracellular signaling system, in the regulation of Ca2+-ATPase activity in rat heart mitochondria was investigated. Mitochondrial Ca2+-ATPase activity was significantly increased by increasing concentrations of CaCl2 (2.5-50 microM). An increase in the enzyme activity was saturated at 50 microM CaCl2. The addition of regucalcin (10(-11)-10(-8) M) in the enzyme reaction mixture caused a significant increase in Ca2+-ATPase activity in heart mitochondria in the presence of 50 microM CaCl2. Regucalcin did not have a significant effect on mitochondrial Mg2+-ATPase activity. Regucalcin (10(-9) M) did not have a significant effect on Ca2+-ATPase activity in the presence of digitonin (10(-3) or 10(-2) %), which is a solubilization effect on membranous lipids. The effect of regucalcin in increasing mitochondrial Ca2+-ATPase activity was not observed in the presence of ruthenium red (10(-7) M) or lanthanum chloride (10(-7) M), which is an inhibitor of Ca2+ uniporter. The effect of regucalcin (10(-9) M) in increasing mitochondrial Ca2+-ATPase activity was not significantly enhanced in the presence of calmodulin (5 microg/ml) or dibutyryl cyclic AMP (10(-4) M), which is an intracellular signaling factor that can cause a significant increase in the enzyme activity. Mitochondrial regucalcin localization was significantly increased in the heart of regucalcin transgenic rats as compared with that of normal rats using Western blot analysis. Ca2+-ATPase activity was significantly increased in the heart mitochondria of regucalcin transgenic rats. This study demonstrates that regucalcin has an activating effect on Ca2+-ATPase in rat heart mitochondria, suggesting its role in the regulation of heart mitochondrial function.
authors.affiliation: Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka 422-8526, Japan.
authors.forename: Tania
authors.initials: T
authors.lastname: Akhter
authors.forename: Natsumi
authors.initials: N
authors.lastname: Sawada
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Yamaguchi
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D015153:Blotting, Western; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002122:Calcium Chloride / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D002147:Calmodulin / Q000494:pharmacology; D002265:Carboxylic Ester Hydrolases; D004072:Digitonin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D047908:Intracellular Signaling Peptides and Proteins; D007811:Lanthanum / Q000494:pharmacology; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D012430:Ruthenium Red / Q000494:pharmacology; D015238:Sulfotransferases
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin; D047908:Intracellular Signaling Peptides and Proteins; C028521:lanthanum chloride; D012430:Ruthenium Red; D003994:Bucladesine; D007811:Lanthanum; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C513325:Rgn protein, rat; D000252:Calcium-Transporting ATPases; D004072:Digitonin; D002122:Calcium Chloride; D002118:Calcium