title: Modulation of tissue factor-factor VIIa signaling by lipid rafts and caveolae.
abstract: OBJECTIVE
  Coagulation factor VIIa (VIIa) binding to its cellular receptor, tissue factor (TF), not only initiates the coagulation cascade but also induces cell signaling by activating G-protein coupled protease-activated receptors. The objective of the present study is to investigate the role of lipid rafts and caveolae in modulating TF-VIIa signaling and coagulant functions.
  
  
  RESULTS
  TF-VIIa coagulant function was measured in factor X activation assay and the signaling function was evaluated in phosphoinositide hydrolysis and IL-8 gene induction. Buoyant density gradient centrifugation and immunofluorescence confocal microscopy were used to determine cellular localization of TF and protease-activated receptor 2. The data show that a substantial fraction of TF and protease-activated receptor 2 resides in lipid rafts/caveolae, and disruption of lipid rafts by cholesterol depletion or modification reduced TF-VIIa-induced cell signaling. Disruption of caveolae with caveolin-1 silencing had no effect on the TF-VIIa coagulant activity but inhibited the TF-VIIa-induced cell signaling.
  
  
  CONCLUSIONS
  Overall our data show that lipid raft/caveolae play a selective role in modulating the TF-VIIa signaling function without affecting the TF-VIIa coagulant activity.
authors.affiliation: Biomedical Research Division, The University of Texas Health Center at Tyler, 11937 US Highway 271, Tyler, TX 75708, USA.
authors.forename: Vineet
authors.initials: V
authors.lastname: Awasthi
authors.forename: Samir K
authors.initials: SK
authors.lastname: Mandal
authors.forename: Veena
authors.initials: V
authors.lastname: Papanna
authors.forename: L Vijaya Mohan
authors.initials: LV
authors.lastname: Rao
authors.forename: Usha R
authors.initials: UR
authors.lastname: Pendurthi
mesh_terms: D000818:Animals; D001777:Blood Coagulation; D019556:COS Cells; D021941:Caveolae / Q000378:metabolism; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D002784:Cholesterol / Q000172:deficiency / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015942:Factor VIIa / Q000378:metabolism*; D015951:Factor Xa / Q000378:metabolism; D005372:Filipin / Q000494:pharmacology; D006801:Humans; D006868:Hydrolysis; D016209:Interleukin-8 / Q000096:biosynthesis / Q000235:genetics; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D044464:Receptor, PAR-2 / Q000378:metabolism*; D015398:Signal Transduction; D013925:Thromboplastin / Q000378:metabolism*; D015854:Up-Regulation; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D051242:Caveolin 1; D016209:Interleukin-8; D010716:Phosphatidylinositols; D012333:RNA, Messenger; D044464:Receptor, PAR-2; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D005372:Filipin; D013925:Thromboplastin; D002784:Cholesterol; D015942:Factor VIIa; D015951:Factor Xa