title: Platelet-derived growth factor increases the turnover of GTP/GDP on ras in permeabilized fibroblasts.
abstract: The potent mitogen platelet-derived growth factor (PDGF) induced a rapid increase in Ras.GTP in permeabilized human and murine fibroblasts. The effect was initiated by both PDGF-AA acting exclusively through PDGF alpha-receptors, and by PDGF-BB interacting with both alpha- and beta-type receptors. The dose-response curves suggest that both receptor types mediate the response. PDGF-dependent Ras activation, measured as increased formation of Ras.GTP, was rapid and reversible. At 37 degrees C the effect had a duration of around 10 min. The PDGF-dependent increase in Ras.GTP was followed by a simultaneous increase in Ras.GDP. Under no experimental condition could a relative increase in Ras.GTP be detected. 0.5 microM GDP and 0.5 microM GTP were equally potent competing for the formation of Ras.[alpha-32P]GTP upon PDGF stimulation. Furthermore, when the basal nucleotide exchange rate on Ras was elevated by omission of Mg2+ from the medium, PDGF had no further effect on the formation of Ras.GTP. We therefore conclude that PDGF activates Ras through a mechanism leading to an increased nucleotide exchange on Ras.
authors.affiliation: Department of Pathology, University Hospital, Uppsala, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Nånberg
authors.forename: B
authors.initials: B
authors.lastname: Westermark
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D004261:DNA Replication / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D051379:Mice; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D016283:Proto-Oncogene Proteins p21(ras) / Q000302:isolation & purification / Q000378:metabolism*; D012867:Skin / Q000378:metabolism; D013873:Thionucleotides / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors
chemical_list: D010982:Platelet-Derived Growth Factor; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C023427:guanosine 5'-O-(2-thiodiphosphate); D006160:Guanosine Triphosphate; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D008274:Magnesium; D001839:Bombesin; D013936:Thymidine