title: The distinct role of guanine nucleotide exchange factor Vav1 in Bcl-2 transcription and apoptosis inhibition in Jurkat leukemia T cells.
abstract: OBJECTIVE
  To investigate a novel function of proto-oncogene Vav1 in the apoptosis of human leukemia Jurkat cells.
  
  
  METHODS
  Jurkat cells, Jurkat-derived vav1-null cells (J.Vav1) and Vav1-reconstituted J.WT cells were treated with a Fas agonist antibody, IgM clone CH11. Apoptosis was determined using propidium iodide (PI) staining, Annexin-V staining, DNA fragmentation, cleavage of caspase 3/caspase 8, and poly (ADP-ribose) polymerase (PARP). Mitochondria transmembrane potential (ΔΨ(m)) was measured using DiOC(6)(3) staining. Transcription and expression of the Bcl-2 family of proteins were evaluated using semi-quantitative RT-PCR and Western blot, respectively. Bcl-2 promoter activity was analyzed using luciferase reporter assays.
  
  
  RESULTS
  Cells lacking Vav1 were more sensitive to Fas-mediated apoptosis than Jurkat and J.WT cells. J.Vav1 cells lost mitochondria transmembrane potential (ΔΨ(m)) more rapidly upon Fas induction. These phenotypes could be rescued by re-expression of Vav1 in J.Vav1 cells. The expression of Vav1 increased the transcription of pro-survival Bcl-2. The guanine nucleotide exchange activity of Vav1 was required for enhancing Bcl-2 promoter activity, and the Vav1 downstream substrate, small GTPase Rac2, was likely involved in the control of Bcl-2 expression.
  
  
  CONCLUSIONS
  Vav1 protects Jurkat cells from Fas-mediated apoptosis by promoting Bcl-2 transcription through its GEF activity.
authors.affiliation: Tianjin Key Laboratory of Protein Sciences, Department of Biochemistry and Molecular Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Yin
authors.forename: Ya-juan
authors.initials: YJ
authors.lastname: Wan
authors.forename: Shi-yang
authors.initials: SY
authors.lastname: Li
authors.forename: Ming-juan
authors.initials: MJ
authors.lastname: Du
authors.forename: Cui-zhu
authors.initials: CZ
authors.lastname: Zhang
authors.forename: Xing-long
authors.initials: XL
authors.lastname: Zhou
authors.forename: You-jia
authors.initials: YJ
authors.lastname: Cao
mesh_terms: D017209:Apoptosis; D015973:Gene Expression Regulation, Leukemic; D006801:Humans; D019169:Jurkat Cells; D007938:Leukemia / Q000235:genetics* / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics* / Q000378:metabolism; D051567:Proto-Oncogene Proteins c-vav / Q000235:genetics* / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D000097766:RAC2 GTP-Binding Protein
chemical_list: D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2; D051567:Proto-Oncogene Proteins c-vav; D020744:rac GTP-Binding Proteins; D000097766:RAC2 GTP-Binding Protein; C000715470:MAS1 protein, human; C496618:VAV1 protein, human