title: Bcl-XL disrupts death-inducing signal complex formation in plasma membrane induced by hypoxia/reoxygenation.
abstract: Hypoxia/reoxygenation (H/R) causes cellular injury and death. The cell death pathways induced by H/R remain incompletely understood. H/R can induce Bid and Bax mitochondrial translocation and cytochrome c release. Using mouse lung endothelial cells (MLEC), we examined the role of Bcl-X(L), an anti-apoptotic Bcl-2-related protein, in H/R-induced cell death. The expression of Bcl-X(L) protected MLEC against H/R-induced cell death by blocking Bax and Bid translocation and inhibiting mitochondrial cytochrome c release. Bcl-X(L) expression inhibited caspase-8 cleavage and death-inducing signal complex (DISC) formation in plasma membrane. By isolating mitochondrial, nuclear, and Golgi fractions, we found that H/R induced DISC formation in these organelles. Bcl-X(L) expression inhibited DISC formation in the nuclear and Golgi fractions relative to LacZ-infected controls. In contrast, DISC formation was elevated in the mitochondrial fraction of Bcl-X(L)-infected cells. GRASP65, a Golgi-associated protein, physically associated with Fas and caspase-8; Bcl-X(L) expression decreased these associations. Bcl-X(L) expression also up-regulated FLIP, a caspase-8 inhibitor. In conclusion, Bcl-X(L) may inactivate caspase-8 by decreasing DISC formation in the plasma membrane, nucleus, and Golgi complex while diverting DISC formation to the mitochondria. The inhibitory effects of Bcl-X(L) on DISC formation may play significant roles in protecting endothelial cells from H/R-induced cell death.
authors.affiliation: Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Xue
authors.initials: X
authors.lastname: Wang
authors.forename: Jinglan
authors.initials: J
authors.lastname: Zhang
authors.forename: Hong Pyo
authors.initials: HP
authors.lastname: Kim
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.forename: Augustine M K
authors.initials: AM
authors.lastname: Choi
authors.forename: Stefan W
authors.initials: SW
authors.lastname: Ryter
mesh_terms: D000818:Animals; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D015687:Cell Hypoxia; D002462:Cell Membrane / Q000737:chemistry; D019069:Cell Respiration; D002478:Cells, Cultured; D053418:Death Domain Receptor Signaling Adaptor Proteins; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism / Q000502:physiology*; D018124:Receptors, Tumor Necrosis Factor / Q000032:analysis* / Q000378:metabolism; D015398:Signal Transduction; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor / Q000378:metabolism
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494827:Bax protein, mouse; C494812:Bcl2l1 protein, mouse; C494815:Bid protein, mouse; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins; C506387:Cflar protein, mouse; D053418:Death Domain Receptor Signaling Adaptor Proteins; D047908:Intracellular Signaling Peptides and Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D018124:Receptors, Tumor Necrosis Factor; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor; C505526:Casp8 protein, mouse; D053181:Caspase 8; D020169:Caspases