title: Accumulation of the SET protein in HEK293T cells and mild oxidative stress: cell survival or death signaling.
abstract: SET protein (I2PP2A) is an inhibitor of PP2A, which regulates the phosphorylated Akt (protein kinase B) levels. We assessed the effects of SET overexpression in HEK293T cells, both in the presence and the absence of mild oxidative stress induced by 50 μM tert-butyl hydroperoxide. Immunoblotting assays demonstrated that SET accumulated in HEK293T cells and increased the levels of phosphorylated Akt and PTEN; in addition, SET decreased glutathione antioxidant defense of cell and increased expression of genes encoding antioxidant defense proteins. Immunofluorescence analysis demonstrated that accumulated SET was equally distributed in cytoplasm and nucleus; however, in cells that had been exposed to oxidative stress, SET was found in large aggregates in the cytoplasm. SET accumulation in HEK293T cells correlated with inhibition of basal apoptosis as evidenced by a decrease in annexin V staining and activity of caspases; under mild oxidative stress, SET accumulation correlated with caspase-independent cell death, as evidenced by increased PI and annexin V/PI double staining. The results suggest that accumulated SET could act via Akt/PTEN either as cell survival signal or as oxidative stress sensor for cell death.
authors.affiliation: Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil. andreiaml@usp.br
authors.forename: Andréia M
authors.initials: AM
authors.lastname: Leopoldino
authors.forename: Cristiane H
authors.initials: CH
authors.lastname: Squarize
authors.forename: Cristiana B
authors.initials: CB
authors.lastname: Garcia
authors.forename: Luciana O
authors.initials: LO
authors.lastname: Almeida
authors.forename: Cezar R
authors.initials: CR
authors.lastname: Pestana
authors.forename: Ana C M
authors.initials: AC
authors.lastname: Polizello
authors.forename: Sérgio A
authors.initials: SA
authors.lastname: Uyemura
authors.forename: Eloiza H
authors.initials: EH
authors.lastname: Tajara
authors.forename: J Silvio
authors.initials: JS
authors.lastname: Gutkind
authors.forename: Carlos
authors.initials: C
authors.lastname: Curti
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D002470:Cell Survival; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism*; D004268:DNA-Binding Proteins; D005455:Fluorescent Antibody Technique; D005978:Glutathione / Q000378:metabolism; D057809:HEK293 Cells; D056488:Histone Chaperones / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D015854:Up-Regulation; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D016877:Oxidants; C513473:SET protein, human; D014157:Transcription Factors; D020122:tert-Butylhydroperoxide; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D020169:Caspases; D005978:Glutathione