title: An integrated proteomics and bioinformatics analyses of hepatitis B virus X interacting proteins and identification of a novel interactor apoA-I.
abstract: HBx is well-known to be a multifunctional protein encoded by HBV and its biological functions are mainly dependent on pleiotropic protein-protein interactions (PPIs); however, the global mapping of HBx-interactome has not been established so far. Thus, in this study, we have identified 127 HBx-interacting proteins by a profound GST pull-down assay coupled with mass spectrometry, and constructed an HBx-interactome network and core apoA-I pathways with a series of bioinformatics approaches. One of the identified HBx-binding partners is apolipoprotein A-I (apoA-I), which has a specific role in lipid and cholesterol metabolism. The HBx-apoA-I protein interaction was confirmed by both GST pull-down and co-immunoprecipitation. The ectopic overexpression of apoA-I can lead to a significant inhibition on HBV secretion concomitant with the reduction of cellular cholesterol level. In addition, HBV can modulate the function of apoA-I through HBx which might interact with the 44-189 residues of apoA-I and result in dysfunction of apoA-I such as decreased self-association ability, increased carbonyl level and impaired lipid-binding ability. Our results demonstrate an integrated physical association of HBx and host proteins, especially a novel interactor apoA-I that may influence the HBV secretion, which would shed new light on exploring the complicated mechanisms of HBV manipulation on host cellular functions.
  
  
  CONCLUSIONS
  HBx is well-known to be a multifunctional protein encoded by HBV and its biological functions are mainly dependent on pleiotropic protein-protein interactions. Although a series of HBx-interacting proteins have been identified, a global characterization of HBx interactome has not been reported. In this study, we have identified a total of 127 HBx-interacting proteins by a profound GST pull-down assay coupled with mass spectrometry, and constructed an HBx-interactome network with a series of bioinformatics approaches. Our results demonstrate an integrated physical association of HBx and host proteins which may help us explore the complicated mechanisms of HBV manipulation on host cellular functions. In addition, we validated one of the identified HBx-binding partners, apolipoprotein A-I (apoA-I), which played a significant inhibitory effect on HBV secretion, indicating a crucial role of the HBx-apoA-I axis in HBV life cycle.
authors.affiliation: The State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, PR China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.forename: Na
authors.initials: N
authors.lastname: Xie
authors.forename: Weifeng
authors.initials: W
authors.lastname: He
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Lei
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.forename: Hong
authors.initials: H
authors.lastname: Tang
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.forename: Canhua
authors.initials: C
authors.lastname: Huang
authors.forename: Yuquan
authors.initials: Y
authors.lastname: Wei
mesh_terms: D000818:Animals; D016632:Apolipoprotein A-I / Q000235:genetics / Q000378:metabolism*; D002784:Cholesterol / Q000235:genetics / Q000378:metabolism; D019295:Computational Biology / Q000379:methods; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D056945:Hep G2 Cells; D006515:Hepatitis B virus / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D040901:Proteomics / Q000379:methods*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins; D017201:Virus Shedding / Q000502:physiology*
chemical_list: D016632:Apolipoprotein A-I; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D002784:Cholesterol