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βig-h3 is a transforming growth factor-β (TGF-β)-induced cell-adhesive molecule and has an RGD sequence at its C-terminus. A previous report suggested that βig-h3 normally undergoes carboxy-terminal processing that results in the loss of the RGD sequence. RGD peptides appear to play various roles in cell function. Here we show that the RGD peptides released from βig-h3 may facilitate TGF-β-induced apoptosis. We found that carboxy-terminal cleavage of βig-h3 occurred after its secretion, and that overexpression of the wild-type βig-h3 induced apoptosis, unlike the C-terminal deleted but RGD-containing mutant βig-h3, which is resistant to C-terminal processing. The βig-h3-induced apoptosis was abolished by either deletion of the RGD sequence or mutation of RGD to RAE. Synthetic peptides of ERGDEL and GRGDSP derived from βig-h3 and fibronectin, respectively, also induced apoptosis, unlike …