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KMID : 0191120080230020262
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Journal of Korean Medical Science
2008 Volume.23 No. 2 p.262 ~ p.269
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Regulation of Inhibitors of Differentiation Family Proteins by Thyroid-Stimulating Hormone in FRTL-5 Thyroid Cells
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Jo Young-Suk
Lee Ihn-Suk
Kim Yun-Jeung
Rha So-Young
Shong Min-Ho
Kim Seul-Young
Choi Yun-Sun
Bai Youn-Sun
Ro Heung-Kyu
Hong Jun-Hwa
Hwang Eun-Suk
Lee Ju-Hee
Lee Yun-Hyeong
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Abstract
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Members of the inhibitors of differentiation (Id) family of helix-loop-helix (HLH) proteins are known to play important roles in the proliferation and differentiation of many cell types. Thyroid-stimulating hormone (TSH) regulates proliferation and differentiation by activating TSH receptor (TSHR) in thyrocytes. In this study, we found that Id2, one of the Id family proteins, is a major target for regulation by TSH in FRTL-5 thyroid cells. TSH rapidly increases the Id2 mRNA level in FRTL-5 thyroid cells but the Id2 protein showed biphasic regulatory patterns, being transiently reduced and subsequently induced by TSH treatment. Transient reduction of Id2 protein was noted within 2 hr of TSH treatment and was mediated by proteasomal degradation. Moreover, reduced Id2 expression correlated with the activity of the phosphatidylinositol 3 kinase pathway, which is activated by TSH. Although TSH increases the activity of the Id2 promoter, TSH-induced activation of this promoter was independent of c-Myc. Id2 did not alter TTF-1- and Pax-8-mediated effects on the regulation of the Tg promoter. Thus, in summary, we found that TSH regulates Id2 expression, but that Id2 does not alter the expression of thyroid-specific genes, such as Tg, in FRTL-5 thyroid cells.
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KEYWORD
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Thyroid Gland, Thyrotropin, Id2 protein
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