title: c-Src signaling induced by the adapters Sin and Cas is mediated by Rap1 GTPase.
abstract: Oncogenic Src proteins have been extensively studied to gain insight into the signaling mechanisms of Src. To better understand signaling through wild-type Src, we used an approach that involves activation of Src signaling through the binding of physiologic ligands to the Src SH3 domain. To this end, we used full-length and truncated versions of the multiadapter molecules Cas and Sin to activate c-Src, and we examined the intracellular pathways that mediate Src signaling under these conditions. We show that although all proteins bind to and are phosphorylated by c-Src, quantitative differences exist in the ability of the different ligands to activate c-Src signaling. In addition, we show that Sin- and Cas-induced Src signaling, as assayed by transcriptional activation, is exclusively mediated through a pathway that involves the adapter Crk and the GTP-binding protein Rap1. These data are in contrast to previous observations showing Ras to mediate signaling downstream of transforming Src alleles. In our system, we found that signaling through the oncogenic SrcY527 mutant is indeed mediated by Ras. In addition, we found that Rap1 also mediates oncogenic Src signaling. Our results show for the first time that Rap1 mediates c-Src kinase signaling and reveal mechanistic differences in the signaling properties of wild-type and transforming Src proteins.
authors.affiliation: Department of Pharmacology, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA.
authors.forename: L
authors.initials: L
authors.lastname: Xing
authors.forename: C
authors.initials: C
authors.lastname: Ge
authors.forename: R
authors.initials: R
authors.lastname: Zeltser
authors.forename: G
authors.initials: G
authors.lastname: Maskevitch
authors.forename: B J
authors.initials: BJ
authors.lastname: Mayer
authors.forename: K
authors.initials: K
authors.lastname: Alexandropoulos
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000483:Alleles; D019943:Amino Acid Substitution; D050719:Crk-Associated Substrate Protein; D029721:Drosophila Proteins; D006801:Humans; D019476:Insect Proteins / Q000502:physiology*; D008024:Ligands; D020935:MAP Kinase Signaling System / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009363:Neoplasm Proteins / Q000502:physiology; D009857:Oncogenes; D010446:Peptide Fragments / Q000378:metabolism; D010750:Phosphoproteins / Q000502:physiology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011506:Proteins; D011518:Proto-Oncogene Proteins / Q000502:physiology; D050737:Proto-Oncogene Proteins c-crk; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D050717:Retinoblastoma-Like Protein p130; D017384:Sequence Deletion; D015533:Transcriptional Activation / Q000502:physiology; D014407:Tumor Cells, Cultured; D020827:rap1 GTP-Binding Proteins / Q000502:physiology*; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C493841:BCAR1 protein, human; D050719:Crk-Associated Substrate Protein; D029721:Drosophila Proteins; D019476:Insect Proteins; D008024:Ligands; C099942:NEDD9 protein, human; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; D011993:Recombinant Fusion Proteins; D050717:Retinoblastoma-Like Protein p130; C122121:Sin protein, Drosophila; D016392:Proto-Oncogene Proteins pp60(c-src); D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020827:rap1 GTP-Binding Proteins