The effect of S-adenosyl methionine on the TSH receptor function in human thyroid tissue: increase in binding of TSH...

Area of Science:

• Endocrinology
• Molecular Biology
• Biochemistry

Background:

• Thyroid-stimulating hormone (TSH) receptor plays a crucial role in thyroid hormone regulation.
• Adenylate cyclase coupling is a key signaling pathway downstream of the TSH receptor.
• S-Adenosyl methionine (AdoMet) is a universal methyl donor involved in various cellular processes.

Purpose of the Study:

• To investigate the impact of S-Adenosyl methionine (AdoMet) on TSH receptor binding.
• To examine the effect of AdoMet on adenylate cyclase coupling in response to TSH receptor activation.
• To elucidate the potential mechanism of AdoMet's action on the TSH receptor.

Main Methods:

• Human thyroidal crude membrane fractions were utilized.
• Membranes were pretreated with S-Adenosyl methionine (AdoMet) and S-Adenosyl homocysteine (AdoHcy).
• 125I-TSH binding assays and adenylate cyclase activity measurements were performed.

Main Results:

• AdoMet significantly increased TSH binding affinity to the TSH receptor.
• AdoMet markedly decreased adenylate cyclase coupling efficiency.
• The effects of AdoMet were partially reversed by AdoHcy pretreatment.

Conclusions:

• AdoMet modulates TSH receptor function by increasing ligand binding affinity.
• AdoMet impairs TSH-induced adenylate cyclase activation, suggesting a downstream signaling disruption.
• The findings imply that AdoMet-induced methylation alters the TSH receptor's tertiary structure, affecting its functional coupling.