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Is receptor cleavage into two subunits necessary for thyrotropin action?
G D Chazenbalk1, S M McLachlan, Y Nagayama
1Thyroid Molecular Biology Unit, Veterans' Administration Medical Center, San Francisco, California 94121, USA.
Biochemical and Biophysical Research Communications
|August 14, 1996
Summary
The chimeric TSH-LH/CG receptor TSH-LHR-14 does not require cleavage into subunits to bind thyrotropin (TSH) and signal. This finding suggests receptor cleavage is not essential for TSH action.
Area of Science:
- Endocrinology
- Molecular Biology
- Cell Biology
Background:
- The thyrotropin (TSH) receptor mediates TSH action through a signaling cascade.
- Receptor processing, including subunit cleavage, is crucial for the function of many cell surface receptors.
Purpose of the Study:
- To investigate the processing and function of a novel chimeric TSH receptor, TSH-LHR-14.
- To determine if cleavage into subunits is necessary for TSH receptor activity.
Main Methods:
- Utilizing [125I]TSH cross-linking on intact cells to study receptor processing.
- Employing immunoblotting with reducing conditions to analyze receptor chains.
- Assessing receptor carbohydrate content using endoglycosidase H digestion.
Main Results:
- The chimeric TSH-LHR-14 receptor did not cleave into subunits upon TSH binding, unlike the wild-type receptor.
- Immunoblotting confirmed a single-chain TSH-LHR-14 receptor under reducing conditions.
- TSH-LHR-14 exhibited resistance to endoglycosidase H, indicating complex glycosylation and cell surface expression.
Conclusions:
- Receptor cleavage into subunits is not a prerequisite for TSH binding and signal transduction.
- The chimeric TSH-LHR-14 receptor demonstrates functional TSH action despite lacking cleavage.
- These findings offer new insights into the molecular mechanisms of TSH receptor activation.