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Suppressive role of endogenous regucalcin in the enhancement of protein kinase activity with proliferation of cloned rat hepatoma cells (H4‐II‐E)
Author(s) -
Inagaki Shyuichiroh,
Yamaguchi Masayoshi
Publication year - 2001
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.1080
Subject(s) - staurosporine , protein kinase a , microbiology and biotechnology , protein kinase c , cyclin dependent kinase 2 , mitogen activated protein kinase kinase , fetal bovine serum , tyrosine kinase , trifluoperazine , biology , genistein , kinase , endogeny , cgmp dependent protein kinase , chemistry , signal transduction , biochemistry , endocrinology , calmodulin , cell , enzyme
The role of endogenous regucalcin, which is a regulatory protein in calcium signaling, in the regulation of protein kinase activity in the proliferation of the cloned rat hepatoma cells (H4‐II‐E) was investigated. Hepatoma cells were cultured for 6–72 h in the presence of fetal bovine serum (FBS; 1 or 10%). The number of cells and protein kinase activity in the 5500 g supernatant of cell homogenate was significantly increased 24 and 48 h after the culture with FBS (1 or 10%); the culture with 10% FBS was potent effect as compared with that of 1% FBS. FBS (10%)‐increased protein kinase activity preceded a significant elevation of cell number of 6 h after culture. Serum stimulation‐induced increase in protein kinase activity was significantly decreased in the presence of trifluoperazine (50 μM), staurosporine (10 −6 M) or genistein (10 −5 M) in the enzyme reaction mixture. The presence of anti‐regucalcin monoclonal antibody (40 or 80 ng/ml) in the reaction mixture caused a significant increase in protein kinase activity in the cells cultured with FBS (1 or 10%). This increase was completely blocked by addition of regucalcin (10 −6 M), which can reveal an inhibitory effect on protein kinase activity. Moreover, the effect of antibody in increasing protein kinase activity was significantly inhibited in the presence of trifluoperazine, staurosporine, or genistein, indicating that endogenous regucalcin has an inhibitory effect on Ca 2+ /calmodulin‐dependent protein kinase, protein kinase C, and protein tyrosine kinase. The present study suggests that endogenous regucalcin plays a suppressive role in the enhancement of various protein kinase activities associated with a proliferation of the cloned rat hepatoma cells (H4‐II‐E). J. Cell. Biochem. 36: 12‐18, 2001. © 2001 Wiley‐Liss. Inc.