The effects of N-ras oncogene expression on PDGF-BB stimulated responses in cultured mouse myoblasts.
The role of the ras oncogene in the signalling pathway triggered by platelet-derived growth factor BB (PDGF-BB) has been investigated in a cell line which normally differentiates into myotubes. Following the activation of the N-ras oncogene, however, the cells proliferate and form foci. PDGF-BB stimulated the phosphorylation of tyrosine in several cellular proteins of molecular weight 185, 160, 94, 54, 44, 42 kDa and furthermore Ca2+ was released from internal stores. Activation of the N-ras gene by treatment of cells with dexamethasone (DEX) inhibited these responses to PDGF-BB. On the other hand, both ras-induced and -non induced cells responded to bradykinin (BK), foetal calf serum (FCS) and ionomycin (ION) by releasing Ca2+ from intracellular stores. The inhibition of the response to PDGF-BB in ras-activated cells has been further investigated. The binding of [125I]-PDGF-BB to its receptors was low and western blotting showed a low level of PDGF-BB receptor protein. This was in marked contrast to the receptor number seen in cells grown in growth medium or fusion promoting medium. These results indicate that cells transformed with the N-ras oncogene fail to respond to platelet-derived growth factor and exhibit a very low level of PDGF receptors. This suggests a role for the ras oncogene in the earliest steps of the signalling pathway.
Zeytinoğlu
H
H
University of Anadolu, Faculty of Science, Biology Department, Eskisehir, Turkey.
Griffiths
S L
SL
Dawson
A P
AP
Gibson
I
I
D000818:Animals; D000077214:Becaplermin; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000187:drug effects; D011905:Genes, ras; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D008970:Molecular Weight; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine; D010982:Platelet-Derived Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis; D016283:Proto-Oncogene Proteins p21(ras) / Q000096:biosynthesis*; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
D010750:Phosphoproteins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins; D000077214:Becaplermin; D019000:Phosphotyrosine; D014443:Tyrosine; D015759:Ionomycin; D003907:Dexamethasone; D017479:Receptors, Platelet-Derived Growth Factor; D016283:Proto-Oncogene Proteins p21(ras); D001920:Bradykinin; D002118:Calcium