title: Hepatitis B Virus X Protein Reduces Podocyte Adhesion via Downregulation of α3β1 Integrin.
abstract: OBJECTIVE
  Hepatitis B virus (HBV)-associated glomerulonephritis (HBV-GN) is characterized by a reduced number of podocytes due to apoptosis and shedding from the basement membrane. However, the pathological mechanism of HBV-GN is unclear. We previously showed that hepatitis B virus X protein (HBx) promotes apoptosis in tubular epithelial cells. In this study, we transfected podocytes with HBx and examined the effects on adhesion and apoptosis of these cells.
  
  
  METHODS
  Podocytes were transfected with pc-DNA3.1 (+)-HBx. One control group was not transfected and another control group was transfected with empty plasmids. Podocyte adhesion was assessed by a fluorescence assay, apoptosis was measured by flow cytometry and fluorescence microscopy, and expression of α3β1 integrin was determined by western blotting and the reverse transcription polymerase chain reaction (RT-PCR). Activity of caspase-8 was measured by a spectrophotometric assay.
  
  
  RESULTS
  Relative to controls, podocytes with pc-DNA3.1(+)-HBx had reduced cell adhesion, increased apoptosis, reduced expression of α3β1 integrin, and increased caspase-8 activity. β1 integrin blockage reduced podocyte adhesion, but increased apoptosis and caspase-8 activity. Treatment of transfected podocytes with a caspase-8 inhibitor (Z-IETD-FMK) had no effect on the HBx-mediated integrin downregulation and reduced podocyte adhesion, suggesting that α3β1 integrin downregulaton is sufficient to alter cell adhesion.
  
  
  CONCLUSIONS
  Our in vitro results indicate that HBx reduced podocyte adhesion and expression of α3β1 integrin, and increased apoptosis. Moreover, HBx-mediated downregulation of α3β1 integrin expression is sufficient to reduce podocyte adhesion. HBx-induced apoptosis of podocytes may contribute to HBV-GN.
authors.forename: Ping
authors.initials: P
authors.lastname: He
authors.forename: Dajun
authors.initials: D
authors.lastname: Liu
authors.forename: Beiru
authors.initials: B
authors.lastname: Zhang
authors.forename: Guangyu
authors.initials: G
authors.lastname: Zhou
authors.forename: Xuesong
authors.initials: X
authors.lastname: Su
authors.forename: Yanqiu
authors.initials: Y
authors.lastname: Wang
authors.forename: Detian
authors.initials: D
authors.lastname: Li
authors.forename: Xu
authors.initials: X
authors.lastname: Yang
mesh_terms: D000072283:A549 Cells; D000818:Animals; D000906:Antibodies / Q000276:immunology; D017209:Apoptosis; D053181:Caspase 8 / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D061945:Caspase Inhibitors / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D015536:Down-Regulation; D006801:Humans; D039201:Integrin alpha3beta1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051379:Mice; D009842:Oligopeptides / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D013053:Spectrophotometry; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D000906:Antibodies; D061945:Caspase Inhibitors; D039201:Integrin alpha3beta1; D009842:Oligopeptides; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C403753:benzyloxycarbonyl-isoleucyl-glutamyl-threonyl-aspartic acid fluoromethyl ketone; C057628:hepatitis B virus X protein; D053181:Caspase 8
keywords: Apoptosis; Cell adhesion; HBx; Podocyte; α3β1 integrin