title: Suppressive role of endogenous regucalcin in the regulation of protein phosphatase activity in rat renal cortex cytosol.
abstract: The role of endogenous regucalcin, which is a regulatory protein of calcium signaling, in the regulation of protein phosphatase activity in the cytosol of rat renal cortex was investigated. Protein phosphatase activity toward phosphotyrosine, phosphoserine, and phosphothreonine was found in the cytosol of kidney cortex. The addition of regucalcin (50-250 nM) in the enzyme reaction mixture caused a significant decrease in protein phosphatase activity toward three phosphoamino acids. The effect of calcium (25 microM) and calmodulin (2.5 microg/ml) in increasing protein phosphatase activity toward three phosphoamino acids was significantly decreased by the addition of regucalcin (100 nM). Protein phosphatase activity toward three phosphoamino acids was significantly increased in the presence of anti-regucalcin monoclonal antibody (10-50 ng/ml) in the enzyme reaction mixture. The effect of antibody (25 ng/ml) in increasing the enzyme activity was significantly inhibited by cyclosporin A (10(-5) M) or vanadate (10(-5) M). Regucalcin in the kidney cortex cytosol was clearly decreased by the administration of saline (0.9% NaCl) for seven days in rats. Protein phosphatase activity toward three phosphoamino acids was significantly decreased by saline administration. The effect of anti-regucalcin antibody (25 ng/ml) in increasing protein phosphatase activity toward three phosphoamino acids was not seen in the renal cortex cytocol of saline-administered rats. The present study demonstrates that endogenous regucalcin plays a suppressive role in the regulation of protein phosphatase activity in the cytoplasm of rat kidney cortex.
authors.affiliation: Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka 422-8526, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Morooka
authors.forename: M
authors.initials: M
authors.lastname: Yamaguchi
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000502:physiology*; D002147:Calmodulin / Q000378:metabolism; D002265:Carboxylic Ester Hydrolases; D016572:Cyclosporine / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology* / Q000648:ultrastructure; D047908:Intracellular Signaling Peptides and Proteins; D007672:Kidney Cortex / Q000201:enzymology*; D008297:Male; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012965:Sodium Chloride / Q000378:metabolism / Q000494:pharmacology; D015238:Sulfotransferases
chemical_list: D000911:Antibodies, Monoclonal; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D047908:Intracellular Signaling Peptides and Proteins; D012965:Sodium Chloride; D016572:Cyclosporine; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C513325:Rgn protein, rat; D010749:Phosphoprotein Phosphatases