Role of endogenous regucalcin in the regulation of Ca(2+)-ATPase activity in rat liver nuclei.
The role of endogenous regucalcin in the regulation of Ca(2+)-ATPase, a Ca(2+) sequestrating enzyme, in rat liver nuclei was investigated. Nuclear Ca(2+)-ATPase activity was significantly reduced by the addition of regucalcin (0.1-0.5 microM) into the enzyme reaction mixture. The presence of anti-regucalcin monoclonal antibody (25 or 50 ng/ml) caused a significant elevation of Ca(2+)-ATPase activity; this effect was completely abolished by the addition of regucalcin (0.1 microM). The effect of anti-regucalcin antibody (50 ng/ml) in increasing Ca(2+)-ATPase activity was completely prevented by the presence of thapsigargin (10(-6) M), an inhibitor of Ca(2+) sequestrating enzyme, N-ethylmaleimide (1 mM), a modifying reagent of thiol groups, or vanadate (10(-5) M), an inhibitor of phosphorylation of the enzyme by ATP, which revealed an inhibitory effect on nuclear Ca(2+)-ATPase activity. Meanwhile, the effect of anti-regucalcin antibody (50 ng/ml) was significantly enhanced by the addition of calmodulin (5 microg/ml), which could increase nuclear Ca(2+)-ATPase activity. In addition, the effect of antibody (50 ng/ml) was significantly reduced by the presence of trifluoperazine (20 microM), an antagonist of calmodulin. These results suggest that the endogenous regucalcin in liver nuclei has a suppressive effect on nuclear Ca(2+)-ATPase activity, and that regucalcin can inhibit an activating effect of calmodulin on the enzyme.
Tsurusaki
Y
Y
Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka 422-8526, Japan.
Yamaguchi
M
M
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D002122:Calcium Chloride / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000276:immunology / Q000494:pharmacology / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002265:Carboxylic Ester Hydrolases; D002467:Cell Nucleus / Q000201:enzymology / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D015238:Sulfotransferases; D019284:Thapsigargin / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D014268:Trifluoperazine; D014638:Vanadates; D019284:Thapsigargin; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C513325:Rgn protein, rat; D000252:Calcium-Transporting ATPases; D002122:Calcium Chloride; D005033:Ethylmaleimide; D004229:Dithiothreitol