title: Sos1 disruption impairs cellular proliferation and viability through an increase in mitochondrial oxidative stress in primary MEFs.
abstract: Using a 4-hydroxytamoxifen (4OHT)-inducible, conditional Sos1-null mutation, we analyzed wild-type (WT), single Sos1-KO, Sos2-KO and double Sos1/2 KO primary mouse embryonic fibroblasts (MEF) with an aim at evaluating the functional specificity or redundancy of the Sos1 and Sos2 alleles at the cellular level. The 4OHT-induced Sos1-KO and Sos1/2-DKO MEFs exhibited distinct flat morphology, enlarged cell perimeter and altered cytoskeletal organization that were not observed in the WT and Sos2-KO counterparts. The Sos1-KO and Sos1/2-DKO MEFs also displayed significant accumulation, in comparison with WT and Sos2-KO MEFs, of cytoplasmic vesicular bodies identified as autophagosomes containing degraded mitochondria by means of electron microscopy and specific markers. Cellular proliferation and migration were impaired in Sos1-KO and Sos1/2-DKO MEFs in comparison with WT and Sos2-KO MEFs, whereas cell adhesion was only impaired upon depletion of both Sos isoforms. RasGTP formation was practically absent in Sos1/2-DKO MEFs as compared with the other genotypes and extracellular signal-regulated kinase phosphorylation showed only significant reduction after combined Sos1/2 depletion. Consistent with a mitophagic phenotype, in vivo labeling with specific fluorophores uncovered increased levels of oxidative stress (elevated intracellular reactive oxygen species and mitochondrial superoxide and loss of mitochondrial membrane potential) in the Sos1-KO and the Sos1/2-DKO cells as compared with Sos2-KO and WT MEFs. Interestingly, treatment of the MEF cultures with antioxidants corrected the altered phenotypes of Sos1-KO and Sos1/2-DKO MEFs by restoring their altered perimeter size and proliferative rate to levels similar to those of WT and Sos2-KO MEFs. Our data uncover a direct mechanistic link between Sos1 and control of intracellular oxidative stress, and demonstrate functional prevalence of Sos1 over Sos2 with regards to cellular proliferation and viability.
authors.affiliation: Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC- Universidad de Salamanca), Salamanca, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Liceras-Boillos
authors.affiliation: Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC- Universidad de Salamanca), Salamanca, Spain.
authors.forename: R
authors.initials: R
authors.lastname: García-Navas
authors.affiliation: Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC- Universidad de Salamanca), Salamanca, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Ginel-Picardo
authors.affiliation: Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC- Universidad de Salamanca), Salamanca, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Anta
authors.affiliation: Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC- Universidad de Salamanca), Salamanca, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Pérez-Andrés
authors.affiliation: INCYL (Universidad de Salamanca), Salamanca, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Lillo
authors.affiliation: Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC- Universidad de Salamanca), Salamanca, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Gómez
authors.affiliation: Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC- Universidad de Salamanca), Salamanca, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Jimeno
authors.affiliation: Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC- Universidad de Salamanca), Salamanca, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Fernández-Medarde
authors.affiliation: Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC- Universidad de Salamanca), Salamanca, Spain.
authors.forename: F C
authors.initials: FC
authors.lastname: Baltanás
authors.affiliation: Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CSIC- Universidad de Salamanca), Salamanca, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Santos
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D004249:DNA Damage; D005347:Fibroblasts / Q000378:metabolism*; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D018384:Oxidative Stress; D020837:SOS1 Protein / Q000502:physiology*; D015398:Signal Transduction; D020664:Son of Sevenless Proteins / Q000502:physiology
chemical_list: D000975:Antioxidants; D020837:SOS1 Protein; D020664:Son of Sevenless Proteins; C116864:Sos2 protein, mouse