title: Requirement of phosphatidylinositol 3-kinase-dependent pathway and Src for Gas6-Axl mitogenic and survival activities in NIH 3T3 fibroblasts.
abstract: Gas6 is a secreted protein previously identified as the ligand of the Axl receptor tyrosine kinase. We have shown that Gas6 is able to induce cell cycle reentry of serum-starved NIH 3T3 cells and to efficiently prevent apoptosis after complete growth factor removal, a survival effect uncoupled from Gas6-induced mitogenesis. Here we report that the mitogenic effect of Gas6 requires phosphatidylinositol 3-kinase (PI3K) activity since it is abrogated both by the specific inhibitor wortmannin and by overexpression of the dominant negative P13K p85 subunit. Consistently, Gas6 activates the P13K downstream targets S6K and Akt, whose activation is abrogated by addition of wortmannin. Moreover, rapamycin treatment blocks Gas6-induced entry into the S phase of serum-starved NIH 3T3 cells. We also demonstrate the requirement of Src tyrosine kinase for Gas6 signalling since stable or transient expression of a catalytically inactive form of Src significantly inhibited Gas6-stimulated entry into the S phase. Accordingly, Gas6 addition to serum-starved NIH 3T3 cells causes activation of the intrinsic Src kinase activity. When specifically analyzed in a survival assay, these elements were found to be required for the survival effect of Gas6. Taken together, the evidence presented here identifies elements involved in the Gas6 transduction pathway that are responsible for its antiapoptotic effect and suggests that Src is involved in the events regulating cell survival.
authors.affiliation: Laboratorio Nazionale Consorzio Interuniversitario Biotecnologie, Padriciano, Trieste, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Goruppi
authors.forename: E
authors.initials: E
authors.lastname: Ruaro
authors.forename: B
authors.initials: B
authors.lastname: Varnum
authors.forename: C
authors.initials: C
authors.lastname: Schneider
mesh_terms: D016475:3T3 Cells / Q000166:cytology* / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002470:Cell Survival; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D008934:Mitogens / Q000494:pharmacology; D015513:Oncogene Proteins / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000502:physiology*; D011090:Polyenes / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011506:Proteins / Q000494:pharmacology*; D011518:Proto-Oncogene Proteins; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases; D015398:Signal Transduction / Q000502:physiology*; D020123:Sirolimus; D000077191:Wortmannin; D000094963:Axl Receptor Tyrosine Kinase; D000099255:Growth Arrest-Specific Protein 6
chemical_list: D000730:Androstadienes; D004791:Enzyme Inhibitors; D036341:Intercellular Signaling Peptides and Proteins; D008934:Mitogens; D015513:Oncogene Proteins; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011090:Polyenes; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D011518:Proto-Oncogene Proteins; D016392:Proto-Oncogene Proteins pp60(c-src); D020794:Receptor Protein-Tyrosine Kinases; D011956:Receptors, Cell Surface; D019893:Ribosomal Protein S6 Kinases; D020123:Sirolimus; D000077191:Wortmannin; D000094963:Axl Receptor Tyrosine Kinase; D000099255:Growth Arrest-Specific Protein 6; C000722290:AXL receptor tyrosine kinase, mouse