Increased PTHRP production by a tyrosine kinase oncogene, Tpr-Met: role of the Ras signaling pathway.
We have used the Tpr-Met oncogene as a model to examine signaling pathways of growth factors and tyrosine kinase oncogenes that can increase parathyroid hormone-related peptide (PTHRP) production. PTHRP production in Tpr-Met transfected cells, when assessed by Northern blot analysis and radioimmunoassay, was increased four- to eightfold. Treatment of these cells with the transcriptional inhibitor actinomycin D and nuclear run-off assays showed that the major cause of increased PTHRP mRNA was enhanced gene transcription. To analyze the intracellular signaling molecules involved in PTHRP production, stable cell lines expressing a Tyr489 Phe mutant of the Tpr-Met oncoprotein were examined. The mutant fails to activate phosphatidylinositol (PI)-3 kinase or associate with the Grb-2 adaptor protein and caused a significant reduction in PTHRP production. Treatment of wild-type Tpr-Met transfected cells with wortmannin, a PI-3 kinase inhibitor, had no effect on PTHRP production; however, treatment of these cells with lovastatin, an inhibitor of p21ran isoprenylation, significantly reduced PTHRP expression. These results show that PTHRP is a downsteam target of the Tpr-Met oncogene and indicate that the PTHRP stimulating activity is mediated via the Ras signaling pathway.
Aklilu
F
F
Department of Medicine, McGill University, Montreal, Quebec, Canada.
Park
M
M
Goltzman
D
D
Rabbani
S A
SA
D019870:1-Phosphatidylinositol 4-Kinase; D000730:Androstadienes / Q000494:pharmacology; D002455:Cell Division; D002460:Cell Line / Q000166:cytology; D004355:Drug Stability; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D011905:Genes, ras; D008148:Lovastatin / Q000494:pharmacology; D009154:Mutation; D009857:Oncogenes; D044162:Parathyroid Hormone-Related Protein; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors; D014176:Protein Biosynthesis; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic; D000077191:Wortmannin
D000730:Androstadienes; D004791:Enzyme Inhibitors; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D012333:RNA, Messenger; D008148:Lovastatin; D017853:Phosphotransferases (Alcohol Group Acceptor); D019870:1-Phosphatidylinositol 4-Kinase; D011505:Protein-Tyrosine Kinases; D000077191:Wortmannin