17β-Hydroxysteroid Dehydrogenases in Human Bone Cells
| Autor: | Joanna Debear, William Lathrop, Donald R. Bertolini, Paul P. Tamburini, Qing Qing Qiu, Yu Dong |
|---|---|
| Rok vydání: | 2009 |
| Předmět: |
endocrine system
17-Hydroxysteroid Dehydrogenases Bone disease medicine.drug_class Endocrinology Diabetes and Metabolism Bone Neoplasms Estrone Spodoptera Biology Polymerase Chain Reaction Bone and Bones Catalysis chemistry.chemical_compound Multienzyme Complexes Bone cell Tumor Cells Cultured medicine Animals Humans Orthopedics and Sports Medicine Peroxisomal Multifunctional Protein-2 Enoyl-CoA Hydratase Cells Cultured Hydro-Lyases chemistry.chemical_classification Osteosarcoma Osteoblast Hydroxysteroid Dehydrogenases medicine.disease Recombinant Proteins Isoenzymes Kinetics medicine.anatomical_structure Enzyme chemistry Biochemistry Estrogen Cell culture Oxidation-Reduction |
| Zdroj: | Journal of Bone and Mineral Research. 13:1539-1546 |
| ISSN: | 0884-0431 |
| DOI: | 10.1359/jbmr.1998.13.10.1539 |
| Popis: | Interconversion of estrogens by osteoblasts may play a role in regulating bone mass. As a first step toward exploring this possibility, we investigated the expression and activity of 17beta-hydroxysteroid dehydrogenases (17beta-HSDs) in cultured human osteoblasts (HOB) and osteoblast-like osteosarcoma cells (MG63, TE85, and SaOS-2). Significant 17beta-HSD activity was detected in cell-free extracts of all bone cells with oxidation of estradiol to estrone predominating over reduction. Reverse transcription-polymerase chain reaction (RT-PCR) experiments showed that the mRNA for 17beta-HSD I was detectable only in MG63 cells, albeit at low levels, while 17beta-HSD II was present in MG63, TE85, and HOB, but not SaOS-2, and 17beta-HSD III was absent from each bone cell type. 17Beta-HSD IV was the only isoform present in all bone cells analyzed. Further analysis of the expression of 17beta-HSD IV in these bone cells by immunoblotting revealed both the full-length 83 kDa protein and the proteolytic 38 kDa form. The kinetic parameters for estradiol oxidation by purified recombinant 17beta-HSD IV (Km = 49.7 microM, Vmax = 79.4 nmol/minute/mg of protein) and its HSD-domain (Km = 79.4 microM, Vmax = 476 nmol/minute/mg of protein) were significantly higher than previously reported, but consistent with the values obtained with crude cell-free extracts of SaOS-2 cells (Km = 98.8 microM, Vmax = 0.07 nmol/minute/mg of protein) which contain only 17beta-HSD IV based on RT-PCR. These studies show that bone cells have the capacity to interconvert circulating estrogens and suggest that bone cell 17beta-HSDs serve primarily to attenuate the continuing actions of estradiol through conversion to its less potent form, estrone, under certain conditions. |
| Databáze: | OpenAIRE |
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