Binding of different dimeric forms of PDGF to human fibroblasts: evidence for two separate receptor types

The binding of the three dimeric forms of platelet-derived growth factor (PDGF), PDGF-AA, PDGF-AB and PDGF-BB, to human fibroblasts was studied. Cross-competition experiments revealed the existence of two different PDGF receptor classes: the type A PDGF receptor bound all three dimeric forms of PDGF, whereas the type B PDGF receptor bound PDGF-BB with high affinity and PDGF-AB with lower affinity, but not PDGF-AA. The sizes of the two receptors were estimated with affinity labeling techniques; the A type receptor appeared as a major component of 125 kd and a minor of 160 kd, and the B type receptor as two components of 160 and 175 kd. A previously established PDGF receptor monoclonal antibody, PDGFR-B2, was shown to react with the B type receptor only. The different abilities of the three dimeric forms of PDGF to stimulate incorporation of [3H]TdR into human fibroblasts indicated that the major mitogenic effect of PDGF is mediated via the B type receptor.