| Abstract: |
Transforming growth factor-β (TGF-β) induces a marked decrease in adhesion of MG-63 human osteosarcoma cells to laminin-coated surfaces, but does not significantly alter adhesion to fibronectin- or collagen-coated surfaces. We provide evidence that this effect is due to a switch in the repertoire of cell adhesion receptors in response to TGF-β. MG-63 cells express high levels of α3β1-integrin, which is a polyspecific laminin/collagen/fibronectin receptor, and low levels of α2β1- and α5β1-integrins, which are collagen and fibronectin receptors, respectively. No other integrins of the β1-class could be detected in MG-63 cells. Treatment with TGF-β1 induces a marked (~60%) decrease in the level of expression of α3-integrin subunit mRNA and protein and a concomitant 8-fold increase in α2-subunit expression. These responses become maximal 7-12 h after addition of TGF-β1 to the cells. Expression of α5- and β1-integrin subunits also increases in response to TGF-β1, but to a lesser extent than α2-subunit expression. Thus, as a result of TGF-β action, the α2β1-collagen and α5β1-fibronectin receptors replace the α3β1-laminin/collagen/fibronectin receptor as the predominant integrins of the β1-class in MG-63 cells. These results suggest that one of the effects of TGF-β is to modify the adhesive behavior of certain tumor cells by changing the binding specificity of the complement of integrins that they express. |
| Keywords: |
osteosarcoma; human cell; gene expression; transforming growth factor beta; cell line; transcription, genetic; tumor cells, cultured; gene expression regulation; cell culture; rna, messenger; transforming growth factors; collagen; cell adhesion; integrin; laminin; integrins; fibronectins; human; priority journal; article; support, u.s. gov't, p.h.s.; macromolecular systems; genes, structural; cell strain mg 63
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