title: Involvement of a phosphotyrosine protein phosphatase in the suppression of platelet-derived growth factor receptor autophosphorylation in ras-transformed cells.
abstract: The nature of the suppression of platelet-derived growth factor (PDGF) receptor autophosphorylation in ras-transformed NIH 3T3 fibroblasts was investigated. The PDGF receptor from ras-transformed cells that had been purified by wheatgerm-lectin affinity chromatography displayed normal PDGF-induced autophosphorylation, indicating that the receptor is not irreversibly modified. Various phosphotyrosine-protein-phosphatase inhibitors did not reverse the inhibition of PDGF-receptor kinase in crude membrane preparations from ras-transformed cells. However, treatment of intact ras-transformed cells both with 2 mM sodium orthovanadate and with 20 microM phenylarsine oxide restored PDGF-receptor tyrosine-kinase activity to a level similar to that observed in normal cells. Direct measurement of the phosphatase activities in crude cellular fractions revealed a 2.5-fold higher membrane-associated phosphotyrosine-protein-phosphatase activity in ras-transformed cells, whereas phosphoserine-protein-phosphatase activity remained unchanged between the cell lines. These data suggest that the suppression of the PDGF-receptor tyrosine-kinase activity in ras-transformed cells is mediated via an inhibitory component, distinct from the receptor, that may be positively regulated by the dephosphorylation of tyrosine residue(s).
authors.affiliation: Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, NY 14853.
authors.forename: L
authors.initials: L
authors.lastname: Tomáska
authors.forename: R J
authors.initials: RJ
authors.lastname: Resnick
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002461:Cell Line, Transformed; D002846:Chromatography, Affinity; D015536:Down-Regulation; D011905:Genes, ras; D015151:Immunoblotting; D051379:Mice; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism*
chemical_list: D011505:Protein-Tyrosine Kinases; D017479:Receptors, Platelet-Derived Growth Factor; D017027:Protein Tyrosine Phosphatases