REDUCTION IN PLATELET-DERIVED GROWTH FACTOR RECEPTOR MRNA IN V-SRC-TRANSFORMED FIBROBLASTS

Abstract The status of the platelet-derived growth factor (PDGF) receptor in normal rat kidney (NRK) fibroblasts and in NRK fibroblasts transformed by the v- src oncogene or the polyoma middle T (pmt) antigen has been compared. v- src -NRK cells have 7-fold fewer surface binding sites for PDGF than NRK cells, but the affinity of the residual receptors for PDGF is reduced only 2-fold. Levels of the PDGF receptor measured by Western blotting or in an autophosphorylation assay in vitro are 8- and 4-fold lower respectively in v- src -NRK cells than in NRK cells. No PDGF-induced phosphorylation of the PDGF receptor is apparent after 32 P-labelling of intact v- src -NRK cells, implying that the reduction in PDGF receptor levels is not a consequence of production of autocrine PDGF. A 10-fold reduction in the amount of mRNA for the PDGF receptor is also observed in v- src -NRK cells. No decrease in PDGF receptor protein or mRNA levels is observed in pmt-NRK cells. We conclude that levels of the PDGF receptor in v- src -transformed NRK fibroblasts are modulated by reduction in the level of PDGF receptor mRNA.