FLICE-like inhibitory protein (FLIP) protects against apoptosis and suppresses NF-kappaB activation induced by bacterial lipopolysaccharide.
Bacterial lipopolysaccharide (LPS) via its activation of Toll-like receptor-4 contributes to much of the vascular injury/dysfunction associated with gram-negative sepsis. Inhibition of de novo gene expression has been shown to sensitize endothelial cells (EC) to LPS-induced apoptosis, the onset of which correlates with decreased expression of FLICE-like inhibitory protein (FLIP). We now have data that conclusively establish a role for FLIP in protecting EC against LPS-induced apoptosis. Overexpression of FLIP protected against LPS-induced apoptosis, whereas down-regulation of FLIP using antisense oligonucleotides sensitized EC to direct LPS killing. Interestingly, FLIP overexpression suppressed NF-kappaB activation induced by LPS, but not by phorbol ester, suggesting a specific role for FLIP in mediating LPS activation. Conversely, mouse embryo fibroblasts (MEF) obtained from FLIP -/- mice showed enhanced LPS-induced NF-kappaB activation relative to those obtained from wild-type mice. Reconstitution of FLIP-/- MEF with full-length FLIP reversed the enhanced NF-kappaB activity elicited by LPS in the FLIP -/- cells. Changes in the expression of FLIP had no demonstrable effect on other known LPS/Tlr-4-activated signaling pathways including the p38, Akt, and Jnk pathways. Together, these data support a dual role for FLIP in mediating LPS-induced apoptosis and NF-kappaB activation.
Bovine Functional Genomics Laboratory, USDA Agricultural Research Service/Animal and Natural Resources Institute, Beltsville Agricultural Research Center-East, Bldg. 1040, Room 2, Beltsville, MD 20705-2350, USA. dbanner@anri.barc.usda.gov.
Douglas D
DD
Bannerman
Kristine T
KT
Eiting
Robert K
RK
Winn
John M
JM
Harlan
D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism*; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D004789:Enzyme Activation / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides / Q000494:pharmacology*; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D014162:Transfection
D000942:Antigens, Bacterial; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; C506387:Cflar protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D011500:Protein Synthesis Inhibitors; D003513:Cycloheximide; D020169:Caspases