DIFFERENTIAL CHEMOTACTIC RESPONSES MEDIATED BY PLATELET-DERIVED GROWTH-FACTOR ALPHA-RECEPTORS AND BETA-RECEPTORS

We have performed a modified Boyden chamber chemotaxis assay using NRK -49F cells under serum-free condition, in order to characterize the ch emotactic activity of recombinant platelet derived growth factor (PDGF )-AA, -AB, and -BB. All three PDGF isoforms showed similar chemotactic activity on NRK cells expressing both PDGF alpha- and beta-receptors. A checkerboard analysis revealed that PDGF-AA was a true chemoattract ant for NRK cells, indicating that alpha-receptors could transduce sig nals for the chemotactic response. We then examined the inhibitory eff ects of PDGF isoforms in the upper chamber on NRK cell migration to PD GF in the lower chamber. When higher concentrations of PDGF-AB or -BB were present in the upper chamber, cell migration to any of the PDGF i soforms was completely blocked, whereas PDGF-AA in the upper chamber c ould not induce complete inhibition of the chemotactic migration to PD GF-AB or -BB. Even when 100 ng/ml of PDGF-AA was present in the upper chamber, NRK cell migration to 5 ng/ml of PDGF-AB in the lower chamber was not completely blocked. These findings suggest that the chemotact ic response induced by ligand binding to PDGF beta-receptor may be dif ferent from that induced by ligand binding to PDGF alpha-receptors. (C ) 1995 Academic Press, Inc.