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Interaction of sodium molybdate with the thyroid hormone receptor
1Unité de Recherche en Ontogénèse et Génétique Moléculaire, Le Centre Hospitalier de l'Université Laval, Ste-Foy, Québec, Canada.
Summary
Molybdate stabilizes 3,5,3'-triiodothyronine (T3) binding to rat liver nuclear proteins, protecting against degradation and enhancing recovery after dephosphorylation. This interaction is thiol-dependent and reversible, similar to other nuclear receptor models.
Area of Science:
- Endocrinology
- Molecular Biology
- Biochemistry
Background:
- Nuclear receptors play crucial roles in gene regulation.
- Thyroid hormones, like thyroxine (T4) and 3,5,3 '-triiodothyronine (T3), bind to nuclear receptors.
- Understanding the regulation of hormone-receptor interactions is vital for comprehending thyroid hormone action.
Purpose of the Study:
- To investigate the effect of molybdate on the binding activity of solubilized nuclear proteins from rat liver for T3 and T4.
- To elucidate the nature of the interaction between molybdate and thyroid hormone receptors.
- To examine the influence of molybdate on the stability and recovery of T3-receptor complexes.
Main Methods:
- Solubilization of nuclear proteins from rat liver.
- Measurement of T3 and T4 binding activity in the presence and absence of molybdate and thiol reagents.
- Incubation of T3-receptor complexes at 37°C to assess degradation rates.
- Ion-exchange chromatography to analyze receptor-molybdate interactions.
- Assessment of the effect of beta-mercaptoethanol on T3 binding recovery after dephosphorylation.
Main Results:
- Molybdate (10 mM) decreased T3 binding affinity by 40% in the absence of thiols.
- Molybdate protected T3-receptor complexes from degradation during prolonged incubation at 37°C.
- T4 binding activity was unaffected by molybdate or heating.
- Ion-exchange chromatography revealed a molybdate-receptor interaction affecting T3-receptor complex elution.
- Molybdate enhanced the reversal of dephosphorylation-induced T3 binding loss by beta-mercaptoethanol.
Conclusions:
- Molybdate interacts with thyroid hormone receptors, stabilizing T3 binding.
- This molybdate-receptor interaction is thiol-dependent and influences hormone binding and complex stability.
- The findings suggest a protective role for molybdate in maintaining thyroid hormone receptor function, with implications for understanding receptor regulation.