Cells transformed by ODC, c-Ha-ras and v-src exhibit MAP kinase/Erk-independent constitutive phosphorylation of Sos, Raf and c-Jun activation domain, and reduced PDGF receptor expression.
While it is known that the constitutive activity of a variety of signal transduction molecules leads to cell transformation, a key unresolved question is whether these wirings converge to a common intermediate(s) that dictates transformation. In this study, we investigated whether NIH3T3 and Rat-1 cells transformed by human ornithine decarboxylase (ODC), c-Ha-rasVal12 and temperature-sensitive v-src oncogene display common alteration(s) in the components that relay PDGF-mediated signals in normal fibroblasts. The ras- and ODC-transformed cells did not show constitutively elevated tyrosine phosphorylation of the phospholipase Cgamma-1 (PLCgamma-1), RasGTPase-activating protein (GAP), phosphotyrosine phosphatase Syp, Shc proteins, and phosphatidylinositol 3-kinase (PI3-K) or activation of the MAP kinase (Erk1 and Erk2), p70 S6 kinase or the Janus protein tyrosine kinase (JAK) and signal transducer and activator of transcription (STAT) protein-1 pathways. Instead, the Ras nucleotide exchange factor Sos-1 and Raf-1 kinase exhibited constitutive phosphorylations, as deduced from their electrophoretic mobility shifts in polyacrylamide gels. Hence a kinase distinct from Erk1 and Erk2, previously known to feedback phosphorylate Sos-1 and Raf-1, is responsible for the phosphorylation of these molecules in the transformants. We also demonstrate that the ras- and ODC-transformed cells exhibit loss of both the PDGF alpha- and beta-receptors, while the v-Src-transformants show a predominant reduction in the beta-receptors. Moreover, all the transformed cell lines were found to display a constitutive increase in phosphorylation of c-Jun on serines 63 and 73, which appears to be governed by an as yet unknown kinase.
Paasinen-Sohns
A
A
Haartman Institute, University of Helsinki, Department of Pathology, Finland.
Hölttä
E
E
D016475:3T3 Cells; D000818:Animals; D000077214:Becaplermin; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002461:Cell Line, Transformed; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism*; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D051966:Phospholipase C gamma; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D017479:Receptors, Platelet-Derived Growth Factor / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D007527:Isoenzymes; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D014157:Transcription Factors; D000077214:Becaplermin; D014443:Tyrosine; D017479:Receptors, Platelet-Derived Growth Factor; D015688:Oncogene Protein pp60(v-src); D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D015689:Oncogene Protein p21(ras); D009955:Ornithine Decarboxylase