title: Role of Gas1 down-regulation in mitogenic stimulation of quiescent NIH3T3 cells by v-Src.
abstract: Quiescent mammalian fibroblasts can be induced to reenter the cell cycle by growth factors and oncoproteins. We studied the pathway(s) through which v-Src, the oncogenic tyrosine kinase encoded by the v-src oncogene of Rous sarcoma virus, forces serum-starved NIH3T3 cells to enter S-phase. To this purpose, we isolated and characterized a polyclonal population of NIH3T3 cells transformed by the MR31 retroviral vector, encoding G418 resistance and the v-src temperature-sensitive allele from the mutant ts LA31 PR-A. NIH(MR31) cells displayed a temperature-conditional transformed phenotype and could be made quiescent by serum deprivation at the restrictive temperature. Serum stimulation or thermolabile v-Src reactivation induced entry into S-phase to a comparable extent, although with different kinetics. The data suggest that v-Src mitogenic activity involves early activation of the Erk1/Erk2 MAP kinases with very little tyrosine phosphorylation of the Shc adaptor proteins at least during the early stages of v-Src reactivation and that v-Src-induced S-phase entry was strongly inhibited by drugs affecting MEK or PI 3-kinase. Our results also suggest that down-regulation of gas1 gene expression plays an important role in regulating the efficiency of entry into S-phase triggered by reactivated v-Src and that Gas1 down-regulation does not require PI 3-kinase dependent signals.
authors.affiliation: Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Biologia Cellulare e dello Sviluppo, Università di Roma La Sapienza, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Grossi
authors.forename: S A
authors.initials: SA
authors.lastname: La Rocca
authors.forename: G
authors.initials: G
authors.lastname: Pierluigi
authors.forename: S
authors.initials: S
authors.lastname: Vannucchi
authors.forename: E M
authors.initials: EM
authors.lastname: Ruaro
authors.forename: C
authors.initials: C
authors.lastname: Schneider
authors.forename: F
authors.initials: F
authors.lastname: Tatò
mesh_terms: D016475:3T3 Cells; D000818:Animals; D018797:Cell Cycle Proteins; D002455:Cell Division; D002471:Cell Transformation, Neoplastic; D002867:Chromones / Q000494:pharmacology; D015536:Down-Regulation; D005419:Flavonoids / Q000494:pharmacology; D058851:GPI-Linked Proteins; D015870:Gene Expression; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases; D008934:Mitogens; D009025:Morpholines / Q000494:pharmacology; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics / Q000502:physiology*; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D018797:Cell Cycle Proteins; D002867:Chromones; D005419:Flavonoids; D058851:GPI-Linked Proteins; D008565:Membrane Proteins; D020929:Mitogen-Activated Protein Kinase Kinases; D008934:Mitogens; D009025:Morpholines; D015688:Oncogene Protein pp60(v-src); D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; C096192:GAS1 protein, human; C501180:Gas1 protein, mouse; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one