title: HBx activates FasL and mediates HepG2 cell apoptosis through MLK3-MKK7-JNKs signal module.
abstract: OBJECTIVE
  To investigate the possible mechanism by which hepatitis B virus X protein (HBx) mediates apoptosis of HepG2 cells.
  
  
  METHODS
  HBx expression vector pcDNA3.1-X was transfected into HepG2 cells to establish an HBx high-expression cellular model as pcDNA3.1-X transfected group. The pcDNA3.1-X and pSilencer3.1-shHBX (HBx antagonist) were cotransfected into HepG2 cells to establish an HBx low-expression model as RNAi group. Untransfected HepG2 cells and HepG2 cells transfected with negative control plasmid were used as controls. Apoptosis rate, the expression of Fas/FasL signaling pathway-related proteins and the phosphorylation levels of MLK3, MKK7 and JNKs, which are upstream molecules of death receptor pathways and belong to the family of mitogen-activated protein kinases (MAPKs), were measured in each group.
  
  
  RESULTS
  Compared with HepG2 cell group and RNAi group, apoptosis rate, the expression of Fas and FasL proteins, and the activation of MLK3, MKK7 and JNKs were increased in the pcDNA3.1-X transfected group. The activation of JNKs and expression of FasL protein were inhibited in the pcDNA3.1-X transfected group when treated with a known JNK inhibitor, SP600125. When authors treated pcDNA3.1-X transfected group with K252a, a known MLK3 inhibitor, the activation of MLK3, MKK7 and JNKs as well as expression of FasL protein was inhibited. Furthermore, cell apoptosis rate was also significantly declined in the presence of K252a in the pcDNA3.1-X transfected group.
  
  
  CONCLUSIONS
  HBx can induce HepG2 cell apoptosis via a novel active MLK3-MKK7-JNKs signaling module to upregulate FasL protein expression.
authors.affiliation: Department of Pathogenic Biology and Lab of Infection and Immunology, Xuzhou Medical College, Xuzhou, Jiangsu Province, China.
authors.forename: Ren-Xian
authors.initials: RX
authors.lastname: Tang
authors.forename: Fan-Yun
authors.initials: FY
authors.lastname: Kong
authors.forename: Bao-Feng
authors.initials: BF
authors.lastname: Fan
authors.forename: Xiao-Mei
authors.initials: XM
authors.lastname: Liu
authors.forename: Hong-Juan
authors.initials: HJ
authors.lastname: You
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.forename: Kui-Yang
authors.initials: KY
authors.lastname: Zheng
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D020169:Caspases / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D053222:Fas Ligand Protein / Q000378:metabolism*; D056945:Hep G2 Cells / Q000502:physiology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D048688:MAP Kinase Kinase 7 / Q000235:genetics / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins; D019014:fas Receptor / Q000378:metabolism; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11
chemical_list: D020169:Caspases; D004791:Enzyme Inhibitors; D053222:Fas Ligand Protein; D048031:JNK Mitogen-Activated Protein Kinases; D048688:MAP Kinase Kinase 7; D020930:MAP Kinase Kinase Kinases; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; D019014:fas Receptor; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11; C057628:hepatitis B virus X protein; C482569:MAP2K7 protein, human