Effect of calcium-binding protein regucalcin on Ca2+ transport system in rat liver nuclei: stimulation of Ca2+ release.
The effect of regucalcin, a calcium-binding protein isolated from rat liver cytosol, on Ca2+ transport in rat liver nuclei was investigated. Ca2+ uptake and release were determined with a Ca2+ electrode. Ca2+ uptake increased dependent on adenosine triphosphate (ATP; 0.5-2.0 mM), while the uptake was negligible in the presence of 2 mM ADP or AMP. Regucalcin (0.5-2.0 microM) had no effect on Ca2+ uptake following addition of 2.0 mM ATP. Meanwhile, Ca2+, which accumulated in the nuclei during 10 min after ATP addition, was significantly released by the addition of regucalcin. This release was dose-dependent (0.1-2.0 microM). Vanadate (100 microM) and guanosine triphosphate (100 microM) did not cause a significant release of Ca2+ from the nuclei. Trifluoroperazine (TFP; 50 microM), an antagonist of calmodulin, significantly increased Ca2+ release from the nuclei. The presence of regucalcin (0.5 microM) further enhanced the TFP effect. These results indicate that regucalcin stimulates Ca2+ release from liver nuclei, and that the effect is not influenced by calmodulin antagonist. The finding suggests that regucalcin can regulate the Ca2+ transport system in rat liver nuclei.
Yamaguchi
M
M
Laboratory of Metabolism and Endocrinology, Graduate School of Nutritional Sciences, University of Shizuoka, Japan.
D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000502:physiology*; D002265:Carboxylic Ester Hydrolases; D002467:Cell Nucleus / Q000378:metabolism*; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D015238:Sulfotransferases
D002135:Calcium-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C513325:Rgn protein, rat; D002118:Calcium