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Thyroid stimulating hormone and N6-2'-O-dibutyryladenosine 3'-5'-cyclic monophosphate decrease 110,000-130,000 M(r)
1Department of Laboratory Medicine, Osaka University Medical School, Japan.
Cellular Signalling
|July 1, 1995
Summary
Thyroid stimulating hormone (TSH) and cyclic adenosine monophosphate (cAMP) reduce tyrosine phosphorylation in rat thyroid cells. This suggests TSH and cAMP may inhibit specific tyrosine kinases involved in cell signaling.
Area of Science:
- Cell Biology
- Molecular Endocrinology
- Signal Transduction
Background:
- Thyroid stimulating hormone (TSH) regulates thyroid cell function.
- Tyrosine phosphorylation is a key post-translational modification in cellular signaling pathways.
Purpose of the Study:
- To investigate the effect of TSH on tyrosine phosphorylation in rat thyroid cells (FRTL-5).
- To identify specific protein substrates affected by TSH-induced signaling.
Main Methods:
- Immunoblotting with anti-phosphotyrosine antibodies.
- Treatment of FRTL-5 cells with TSH, Bt2cAMP, IGF-I, PMA, and sodium orthovanadate.
Main Results:
- TSH and Bt2cAMP decreased phosphotyrosine levels of a 110-130 kDa substrate (p120) in FRTL-5 cells.
- Insulin-like growth factor-I (IGF-I) and phorbol 12-myristate 13-acetate (PMA) had attenuated effects compared to TSH.
- Sodium orthovanadate, a tyrosine phosphatase inhibitor, did not block the observed dephosphorylation.
Conclusions:
- TSH and cAMP signaling pathways may inhibit tyrosine kinases acting on the p120 substrate.
- These findings provide insight into the molecular mechanisms of TSH action in thyroid cells.