title: Platelet-derived growth factor-dependent association of the GTPase-activating protein of Ras and Src.
abstract: Here we report that the platelet-derived growth factor beta receptor (betaPDGFR) is not the only tyrosine kinase able to associate with the GTPase-activating protein of Ras (RasGAP). The interaction of non-betaPDGFR kinase(s) with RasGAP was dependent on stimulation with platelet-derived growth factor (PDGF) and seemed to require tyrosine phosphorylation of RasGAP. Because the tyrosine phosphorylation site of RasGAP is in a sequence context that is favoured by the Src homology 2 ('SH2') domain of Src family members, we tested the possibility that Src was the kinase that associated with RasGAP. Indeed, Src interacted with phosphorylated RasGAP fusion proteins; immunodepletion of Src markedly decreased the recovery of the RasGAP-associated kinase activity. Thus PDGF-dependent tyrosine phosphorylation of RasGAP results in the formation of a complex between RasGAP and Src. To begin to address the relevance of these observations, we focused on the consequences of the interaction of Src and RasGAP. We found that a receptor mutant that did not activate Src was unable to efficiently mediate the tyrosine phosphorylation of phospholipase Cgamma (PLCgamma). Taken together, these observations support the following hypothesis. When RasGAP is recruited to the betaPDGFR, it is phosphorylated and associates with Src. Once bound to RasGAP, Src is no longer able to promote the phosphorylation of PLCgamma. This hypothesis offers a mechanistic explanation for our previously published findings that the recruitment of RasGAP to the betaPDGFR attenuates the tyrosine phosphorylation of PLCgamma. Finally, these findings suggest a novel way in which RasGAP negatively regulates signal relay by the betaPDGFR.
authors.affiliation: National Jewish Medical and Research Center, Division of Molecular Signal Transduction, 1400 Jackson Street, Denver, CO 80226, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Schlesinger
authors.forename: K A
authors.initials: KA
authors.lastname: Demali
authors.forename: G L
authors.initials: GL
authors.lastname: Johnson
authors.forename: A
authors.initials: A
authors.lastname: Kazlauskas
mesh_terms: D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000378:metabolism*; D019606:Phosphoamino Acids / Q000032:analysis; D051966:Phospholipase C gamma; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011485:Protein Binding; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine; D020703:ras GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D019606:Phosphoamino Acids; D010982:Platelet-Derived Growth Factor; D011993:Recombinant Fusion Proteins; D020703:ras GTPase-Activating Proteins; D014443:Tyrosine; D020797:Receptor, Platelet-Derived Growth Factor beta; D016392:Proto-Oncogene Proteins pp60(c-src); C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma