Sex hormone-binding globulin: Anatomy and physiology of a new regulatory system
| Autor: | Daniel J. Hryb, William Rosner, Atif M. Nakhla, Nicholas A. Romas, M. Saeed Khan |
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| Rok vydání: | 1991 |
| Předmět: |
Male
medicine.medical_specialty Endocrinology Diabetes and Metabolism medicine.medical_treatment Molecular Sequence Data Clinical Biochemistry Receptors Cell Surface In Vitro Techniques Biology Ligands Biochemistry Steroid Endocrinology Sex hormone-binding globulin Sex Hormone-Binding Globulin Internal medicine Cyclic AMP Tumor Cells Cultured medicine Humans Amino Acid Sequence Receptor Molecular Biology Testosterone Cell Membrane Prostate Cell Biology Sex hormone receptor Steroid hormone Dihydrotestosterone biology.protein Molecular Medicine Steroids hormones hormone substitutes and hormone antagonists Signal Transduction medicine.drug Hormone |
| Zdroj: | The Journal of Steroid Biochemistry and Molecular Biology. 40:813-820 |
| ISSN: | 0960-0760 |
| DOI: | 10.1016/0960-0760(91)90307-q |
| Popis: | Sex hormone-binding globulin (SHBG) is a plasma glycoprotein that binds a number of circulating steroid hormones (testosterone, dihydrotestosterone and estradiol) with high affinity, thus regulating their free concentration in plasma. In addition to binding steroids, SHBG itself binds to receptor sites on plasma membranes with somewhat unusual kinetics. Both the off and on rates are quite slow. The steroid-binding and membrane-binding functions are intertwined in what is clearly an allosteric relationship. Occupation of SHBG's steroid-binding site by a steroid inhibits its ability to bind to its membrane receptor-binding site. This inhibition is not related to a steroid's biological activity. Metabolites of steroids without biological activity, e.g. 2-methoxyestradiol, actively inhibit SHBG's interaction with its membrane receptor. However, if unliganded SHBG is allowed to bind to its receptor on intact cells, and an appropriate steroid hormone then is introduced, adenylate cyclase is activated and intracellular cAMP increases. This function is specific for steroids with biological activity, 2-methoxyestradiol has no activity in this arena. These observations demonstrate a potentially important role for SHBG as a regulator of cell function. They also demonstrate an additional mode of action of steroid hormones, one that does not require that the steroid interact with a steroid receptor. |
| Databáze: | OpenAIRE |
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