Transduction of mitogenic activity of platelet-derived growth factor (PDGF) AB by PDGF-beta receptor without participation of PDGF-alpha receptor in vascular smooth muscle cells.

In cultured rat vascular smooth muscle cells, platelet-derived growth factor (PDGF) beta receptor was expressed at a high level, whereas PDGF-alpha receptor was not detected. PDGF-BB showed a high binding activity at 4 degrees C in the cells and was not displaced by PDGF-AA or -AB. This result indicates that PDGF-AB as well as PDGF-AA does not bind to the cells lacking PDGF-alpha receptor at 4 degrees C. However, at 37 degrees C, PDGF-AB bound to the cells and induced the internalization of PDGF-beta receptor. DNA synthesis was also stimulated potentially by PDGF-AB as well as PDGF-BB in the cells, although PDGF-AA was completely inactive. At 37 degrees C, PDGF-AB caused tyrosine phosphorylation of a group of proteins including PDGF-beta receptor and phospholipase C-gamma 1, but at a slower rate than PDGF-BB. At 4 degrees C, PDGF-AB did not stimulate protein tyrosine phosphorylation, whereas PDGF-BB did. A chemical cross-linking experiment showed that PDGF-beta receptor was dimerized by PDGF-AB as well as PDGF-BB. These results indicate that PDGF-beta receptor binds PDGF-AB without participation of PDGF-alpha receptor at 37 degrees C (but not at 4 degrees C), and PDGF-AB as well as PDGF-BB acts as a potent mitogen in the vascular smooth muscle cells.