Functional roles of the bone morphogenetic protein system in thyrotropin signaling in porcine thyroid cells

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20 Citations (Scopus)

Abstract

We uncovered a new regulation of thyrocyte function by bone morphogenetic protein (BMP) under the influence of thyrotropin (TSH) using primary culture of porcine thyrocytes. The BMP type I receptors, ALK-2 (ActRIA), -3 (BMPRIA), and -6 (BMPRIB), were expressed in porcine thyrocytes, while ALK-6 was not detected in human thyroid. Treatment with BMP-2, -4, -6, -7, and TGF-β1 exhibited a dose-dependent suppression of DNA synthesis by porcine thyrocytes. BMP-2, -4, -6, -7, and TGF-β1 suppressed TSH receptor mRNA expression on thyrocytes, which was consistent with their suppressive effect on TSH-induced cAMP synthesis and TSH-induced insulin-like growth factor-1 expression. Activin exhibited minimal suppression of thyrocyte DNA synthesis and did not exhibit suppressive effects on TSH receptor mRNA expression. Phosphorylated Smad1/5/8 was detected in the lysates of porcine thyrocytes treated with BMP-2, -4, -6, and -7. However, in the presence of TSH, BMP-6 and -7 failed to activate Smad1/5/8 phosphorylation and 3TP-reporter activity, whereas BMP-2 and -4 maintained clear activation of the BMP signaling regardless of the presence of TSH. This diverged regulation of thyroid BMP system by TSH is most likely due to the reduction of ALK-6 expression caused by TSH. Thus, the thyroid BMP system is functionally linked to TSH actions through modulating TSH receptor expression and TSH, in turn, selectively inhibits BMP signaling. Given that BMP system is present in human thyroid and the expression pattern of ALK-2 and BMPRII is different between follicular adenomas and normal thyroid tissues, the endogenous BMP system may be involved in regulating thyrocyte growth and TSH sensitivity of human thyroid adenomas.

Original languageEnglish
Pages (from-to)1124-1130
Number of pages7
JournalBiochemical and Biophysical Research Communications
Volume327
Issue number4
DOIs
Publication statusPublished - Feb 25 2005

Keywords

  • Activin receptor-like kinase
  • Bone morphogenetic protein
  • Thyroid follicular adenoma
  • Thyroid papillary carcinoma
  • Thyrotropin
  • Transforming growth factor-β

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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