title: [The role of lipid raft in TNFR1-mediated signal transduction in osteoblasts].
abstract: OBJECTIVE
  To investigate the role of membrane cholesterol in TNFR1-mediated signal transduction in osteoblastic MC3T3 cells.
  
  
  METHODS
  MCD binds cholesterol specifically and was commonly used to deplete cholesterol from cell plasma membrane. MC3T3 cells were serum-starved for 22 h, treated with MCD (10 g/L) for 60 min followed by TNF-α (10 μg/L) for 0, 5, 10, 15 or 30 min, or TNF-α plus CHX (10 mg/L) for 4 h to induce apoptosis, then TNFR1-mediated IκBα degradation, phosphorylation of AKT, ERK or p38, and processing of caspase-3 were analyzed by using SDS-PAGE/Western blotting method.
  
  
  RESULTS
  MC3T3 cell membrane cholesterol level was reduced to 35% within 60 min by MCD (10 g/L). Reduction of MC3T3 cell surface cholesterol dramatically inhibited TNFR1-mediated AKT phosphorylation, while did not affect the degradation of IκBα, activation of ERK or p38, and processing of caspase-3 induced by TNF-α.
  
  
  CONCLUSIONS
  Cholesterol depletion can destruct lipid rafts; therefore our results suggest that lipid raft is essential for TNFR1-mediated AKT phosphorylation, but is dispensable for TNFR1-mediated degradation of IκBα, activation of ERK or p38 and processing of caspase-3.
authors.affiliation: Key Laboratory for Space Bioscience and Biotechnology, Faculty of Life Sciences, Northwestern Polytechnical University, Xi'an 710072, China. wang.haifang@gmail.com
authors.forename: Hai-Fang
authors.initials: HF
authors.lastname: Wang
authors.forename: M Pavalko
authors.initials: MP
authors.lastname: Fredrick
authors.forename: Qi-Bing
authors.initials: QB
authors.lastname: Mei
mesh_terms: D000818:Animals; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D010006:Osteoblasts / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D016328:NF-kappa B; D047888:Receptors, Tumor Necrosis Factor, Type I; D002784:Cholesterol; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D053148:Caspase 3