Enhancement of protein tyrosine phosphatase activity in the proliferation of cloned rat hepatoma H4-II-E cells: suppressive role of endogenous regucalcin.
The role of endogenous regucalcin in the regulation of protein tyrosine phosphatase activity in the proliferation of the cloned rat H4-II-E hepatoma cells was investigated. Cells were cultured for 6 to 96 h in a medium containing 1.0 or 10% fetal bovine serum (FBS). Cell numbers were significantly raised by culture with 10% FBS in comparison with that of 1.0% FBS. Protein tyrosine phosphatase activity in the cells was significantly elevated by culture with 10% FBS for 24 to 96 h as compared with that of 1% FBS. Such an increase was not seen in protein phosphatase activity toward phosphoserine or phosphothreonine. The presence of anti-regucalcin monoclonal antibody (50 or 100 ng/ml) in the enzyme reaction mixture caused a remarkable elevation of protein tyrosine phosphatase activity in the cells obtained by culture with 1.0 or 10% FBS. This elevation was completely prevented by the addition of regucalcin (10-6 M). The effect of antibody in elevating protein tyrosine phosphatase activity in the cells was significantly inhibited by the addition of okadaic acid (10-6 M) or vanadate (10(-6) M), an inhibitor of protein phosphatase, in the reaction mixture. The present study suggests that protein tyrosine phosphatase activity in the cloned rat hepatoma cells is increased in serum-stimulated cell proliferation, and that endogenous regucalcin has a suppressive role in the enhancement of the enzyme activity in proliferative cells.
Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka 422-8526, Japan.
S
S
Inagaki
M
M
Yamaguchi
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000502:physiology*; D002265:Carboxylic Ester Hydrolases; D002452:Cell Count; D002455:Cell Division; D002999:Clone Cells; D047908:Intracellular Signaling Peptides and Proteins; D008114:Liver Neoplasms, Experimental / Q000201:enzymology* / Q000235:genetics; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D019319:Okadaic Acid / Q000494:pharmacology; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015238:Sulfotransferases; D014407:Tumor Cells, Cultured; D014638:Vanadates / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D002135:Calcium-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; C513324:Rgn protein, mouse; D019319:Okadaic Acid; D014638:Vanadates; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C513325:Rgn protein, rat; D017027:Protein Tyrosine Phosphatases