Inhibitory effect of calcium-binding protein regucalcin on protein kinase activity in the nuclei of regenerating rat liver

✍ Scribed by Toru Katsumata; Masayoshi Yamaguchi

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 108 KB
• Volume: 71
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/(sici)1097-4644(19981215)71:4<569::aid-jcb11>3.0.co;2-z

✦ Synopsis

The effect of Ca 2ϩ -binding protein regucalcin on protein kinase activity in the nuclei of normal and regenerating rat livers was investigated. Protein kinase activity in the nuclei isolated from normal rat liver was significantly increased by addition of Ca 2ϩ (500 µM) and calmodulin (10 µg/ml) in the enzyme reaction mixture. Nuclear protein kinase activity was significantly decreased in the presence of EGTA (1.0 mM), trifluoperazine (TFP; 20 µM), dibucaine (10 Ϫ4 M), or staurosporine (10 Ϫ7 M), indicating that Ca 2ϩ -dependent protein kinases are present in the nuclei. Protein kinase activity was significantly elevated in the liver nuclei obtained at 6 to 48 h after a partial hepatectomy. Hepatectomy-increased nuclear protein kinase activity was significantly decreased in the presence of EGTA (1.0 mM), TFP (20 µM), or staurosporine (10 Ϫ7 M) in the enzyme reaction mixture. The presence of regucalcin (0.1-0.5 µM) caused a significant decrease in protein kinase activity in the nuclei obtained from normal and regenerating rat livers. Meanwhile, the nuclear protein kinase activity from normal and regenerating livers was significantly elevated in the presence of anti-regucalcin monoclonal antibody (50-200 ng/ml). The present study suggests that regucalcin plays a role in the regulation of protein kinase activity in the nuclei of proliferative liver cells.