Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8477330 | Molecular and Cellular Endocrinology | 2013 | 9 Pages |
Abstract
Signaling pathways initiated by transforming growth factor-β (TGF-β) and insulin-like growth factors (IGFs) are important in osteosarcoma cell growth. We have investigated a role for endogenous IGF binding protein-3 (IGFBP-3) in mediating cross-talk between TGF-β receptor and type I IGF receptor (IGF1R) signaling pathways in MG-63 osteosarcoma cells. TGF-β1 indirectly activated the Ras/Raf/MAPK pathway and induced the expression of IGFBP-3, an important regulator of IGF1R activity. IGFBP-3 attenuated TGF-β1 activation of ERK1/2 and Akt in MG-63 cells, and inhibited TGF-β1-induced cell cycle progression and proliferation. This effect of IGFBP-3 was blocked by inhibiting IGF1R signaling. TGF-β1 phosphorylated Smad2 on the non-receptor substrate sites (Ser245/250/255). Blocking the TGF-β1-induced expression of IGFBP-3 enhanced pSmad2(Ser245/250/255) and increased its nuclear accumulation. These results suggest an important role for TGF-β1 in osteosarcoma cell growth, with the induction of IGFBP-3 by TGF-β1 serving in a negative-feedback loop to control cell growth by preventing activation of the IGF1R.
Keywords
HGFtype I IGF receptorTGF-β type I receptorTGF-βReceptor-activated SmadsR-SmadsTβRIIGF binding protein-3TβRIITβRIGFBP-3PI3-KEGFIGFIGF1Rc-Jun N-terminal kinaseMAPKRNA interferenceRNAiSAPK/JNKOsteosarcomatransforming growth factor-βSignalingepidermal growth factorHepatocyte growth factorInsulin-like growth factorphosphoinositide 3-kinaseInsulin-like growth factor binding protein-3mitogen activated protein kinaseTGF-β receptorTGF-β type II receptor
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Authors
Lynette J. Schedlich, Vanessa M. Yenson, Robert C. Baxter,