title: GTK, a Src-related tyrosine kinase, induces nerve growth factor-independent neurite outgrowth in PC12 cells through activation of the Rap1 pathway. Relationship to Shb tyrosine phosphorylation and elevated levels of focal adhesion kinase.
abstract: The rat pheochromocytoma cell line PC12 is extensively used as a model for studies of neuronal cell differentiation. These cells develop a sympathetic neuron-like phenotype when cultured in the presence of nerve growth factor. The present study was performed in order to assess the role of mouse GTK (previously named BSK/IYK), a cytoplasmic tyrosine kinase belonging to the Src family, for neurite outgrowth in PC12 cells. We report that PC12 cells stably overexpressing GTK exhibit a larger fraction of cells with neurites as compared with control cells, and this response is not accompanied by an increased ERK activity. Treatment of the cells with the MEK inhibitor PD98059 did not reduce the GTK-dependent increased in neurite outgrowth. GTK expression induces a nerve growth factor-independent Rap1 activation, probably through altered CrkII signaling. We observe increased CrkII complex formation with p130(Cas), focal adhesion kinase (FAK), and Shb in PC12-GTK cells. The expression of GTK also correlates with a markedly increased content of FAK, phosphorylation of the adaptor protein Shb, and an association between these two proteins. Transient transfection of GTK-overexpressing cells with RalGDS-RBD or Rap1GAP, inhibitors of the Rap1 pathway, reduces the GTK-dependent neurite outgrowth. These data suggest that GTK participates in a signaling pathway, perhaps involving Shb, FAK and Rap1, that induces neurite outgrowth in PC12 cells.
authors.affiliation: Department of Medical Cell Biology, Uppsala University, Uppsala 751 23, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Annerén
authors.forename: K A
authors.initials: KA
authors.lastname: Reedquist
authors.forename: J L
authors.initials: JL
authors.lastname: Bos
authors.forename: M
authors.initials: M
authors.lastname: Welsh
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D008565:Membrane Proteins / Q000378:metabolism; D009363:Neoplasm Proteins; D020932:Nerve Growth Factor / Q000494:pharmacology*; D016501:Neurites / Q000502:physiology*; D016716:PC12 Cells; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D050737:Proto-Oncogene Proteins c-crk; D051381:Rats; D020917:Receptor, trkA; D014443:Tyrosine / Q000378:metabolism*; D020827:rap1 GTP-Binding Proteins / Q000502:physiology*; D018909:src Homology Domains; D019061:src-Family Kinases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C493872:Crk protein, rat; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; C490081:SHB protein, human; C490082:Shb protein, rat; D014443:Tyrosine; D020932:Nerve Growth Factor; D011494:Protein Kinases; C490511:Frk protein, rat; D011505:Protein-Tyrosine Kinases; D020917:Receptor, trkA; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C490512:Frk protein, mouse; C496052:Ptk2 protein, rat; D019061:src-Family Kinases; D020827:rap1 GTP-Binding Proteins