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  • Title: Expression of transforming growth factor-beta1, activin A, and their receptors in thyroid follicle cells: negative regulation of thyrocyte growth and function.
    Author: Franzén A, Piek E, Westermark B, ten Dijke P, Heldin NE.
    Journal: Endocrinology; 1999 Sep; 140(9):4300-10. PubMed ID: 10465304.
    Abstract:
    Thyroid growth and function are intricately regulated by both positive and negative factors. In the present study, we have investigated the expression of transforming growth factor-beta (TGF-beta) super-family members and their receptors in normal porcine thyroid follicle cells. In tissue sections of porcine thyroids, we observed an expression of TGF-beta1, activin A, and bone morphogenetic protein (BMP)-7 proteins. The staining was localized to the follicular epithelium. In affinity cross-linking experiments, TGF-beta1 was found to bind to heteromeric complexes of TGF-beta type I and type II receptors, and activin A bound most efficiently to heteromeric complexes of activin type IB and type II receptors. We were unable to detect any BMP receptors (BMPRs) in attempts to perform affinity cross-linking with BMP-7. However, expression of BMPR-IA and BMPR-II messenger RNA (mRNA) was detected by Northern blot analysis. Both TGF-beta1 and activin A, but not BMP-7, increased the phosphorylation of Smad2, induced nuclear translocation of Smad2, Smad3, and Smad4, and inhibited thyrocyte cell growth as well as TSH-stimulated cAMP response. TGF-beta1 was more potent, compared with activin A, to induce these cellular responses. Taken together, our findings indicate a role for several members of the TGF-beta family in regulation of thyroid growth and function.
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