TGF-beta 1 inhibits the cell proliferation stimulated by IGF-I by blocking the tyrosine phosphorylation of 175kDa substrate.
TGF-beta strongly inhibits the mitogenic effect of growth factors such as insulin-like growth-I (IGF-I) on thyroid follicular cells. To study the mechanism of this inhibiting action, the effect of TGF-beta 1 on tyrosine phosphorylation of 175kDa substrate induced by IGF-I was investigated in FRTL-5 thyroid epithelial cells. After treatment with TGF-beta 1, tyrosine phosphorylation of 175kDa protein induced by IGF-I was inhibited in parallel with the degree of the inhibition of cell proliferation. However, TGF-beta 1 had no effect on tyrosine phosphorylation of 120kDa substrate. These results suggest that TGF-beta 1 blocks the mitogenic signal of IGF-I by inhibiting the tyrosine phosphorylation of 175kDa substrate in FRTL-5 cells.
Liu
G
G
Department of Laboratory Medicine, Osaka University Medicine School, Japan.
Takano
T
T
Amino
N
N
D000818:Animals; D002455:Cell Division / Q000187:drug effects*; D002460:Cell Line; D048429:Cell Size / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000032:analysis; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D051381:Rats; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D016212:Transforming Growth Factor beta; D019000:Phosphotyrosine; D007334:Insulin-Like Growth Factor I; D004247:DNA; D011505:Protein-Tyrosine Kinases