Evaluation of the somatogenic activity of bovine placental lactogen with cell lines transfected with the bovine somatotropin receptor
| Autor: | K. Paik, N.R. Staten, John C. Byatt, M. Huynh, G. Pegg, W. C. Warren |
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| Rok vydání: | 1999 |
| Předmět: |
Gene Expression
Biology Kidney Transfection General Biochemistry Genetics and Molecular Biology Cell Line Mice In vivo Cricetinae Proto-Oncogene Proteins Animals Bovine somatotropin Phosphorylation General Pharmacology Toxicology and Pharmaceutics Placental lactogen Phosphotyrosine Receptor Biological activity Receptors Somatotropin General Medicine Janus Kinase 2 Protein-Tyrosine Kinases Placental Lactogen Molecular biology Cell culture Growth Hormone Cattle Signal transduction Dimerization Cell Division Signal Transduction |
| Zdroj: | Life Sciences. 65:2755-2767 |
| ISSN: | 0024-3205 |
| DOI: | 10.1016/s0024-3205(99)00544-5 |
| Popis: | Studies have shown that bovine placental lactogen (bPL) has partial somatogenic activity in vivo even though binding results clearly indicate bPL does not cause homodimerization of the bovine somatotropin receptor (bST-R). To help understand the receptor binding versus biological activity of bovine somatotropin (bST) and bPL we have developed a homologous model system. Full length bST-R was stably transfected into a murine lymphoid cell line, Ba F3 and a hamster kidney cell line, BHK. From both transfected cell lines, clones were isolated ( Ba F3-C1 and BHK-24) which demonstrated specific binding of bST and, or bPL. Bovine ST stimulated proliferation of the Ba F3-C1 clonal line over a dose range of 10 to 3000 pM with an EC50 of 100 pM. A bST variant (des 1–4 bST) and porcine ST (pST) which both have approximately 10% of the binding affinity for bST-R as native bST were 1 and 10 % as potent as bST in this bioassay, respectively. This suggests that affinity and biological activity are correlated for this system. Proliferation was initiated through the bST-R because addition of a monoclonal antibody which recognizes the extracellular domain of bST-R and inhibits binding of bST to its receptor, inhibited bST-stimulated mitosis. However, even though the affinity of bPL for the bST-R is similar to that of bST, bPL antagonized the proliferative action of bST with an IC50 of 1 nM. Components of the somatogenic signal transduction pathway were also evaluated in both cell lines. Addition of bST to the cell cultures increased phosphorylation of JAK2 in Ba F3-C1 and BHK-24 cells in a dose-responsive manner but bPL failed to increase phosphorylation of JAK2 in either cell line. In summary, these data support the hypothesis that ST-R homodimerization is necessary for bioactivity in this model system but fail to explain apparent somatogenic activity of bPL in vivo. |
| Databáze: | OpenAIRE |
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