Upregulation of the Fas receptor death-inducing signaling complex after traumatic brain injury in mice and humans.
Recent studies have implicated Fas in the pathogenesis of inflammatory, ischemic, and traumatic brain injury (TBI); however, a direct link between Fas activation and caspase-mediated cell death has not been established in injured brain. We detected Fas-Fas ligand binding and assembly of death-inducing signaling complexes (DISCs) [Fas, Fas-associated protein with death domain, and procaspase-8 or procaspase-10; receptor interacting protein (RIP)-RIP-associated interleukin-1beta converting enzyme and CED-3 homolog-1/Ced 3 homologous protein with a death domain-procaspase-2] by immunoprecipitation and immunoblotting within mouse parietal cortex after controlled cortical impact. At the time of DISC assembly, procaspase-8 was cleaved and the cleavage product appeared at 48 hr in terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling-positive neurons. Cleavage of caspase-8 was accompanied by caspase-3 processing detected at 48 hr by immunohistochemistry, and by caspase-specific cleavage of poly(ADP-ribose) polymerase at 12 hr. Fas pathways were also stimulated by TBI in human brain, because Fas expression plus Fas-procaspase-8 interaction were robust in contused cortical tissue samples surgically removed between 2 and 30 hr after injury. To address whether Fas functions as a death receptor in brain cells, cultured embryonic day 17 cortical neurons were transfected with an adenoviral vector containing the gene encoding Fas ligand. After 48 hr in culture, Fas ligand expression and Fas-procaspase-8 DISC assembly increased, and by 72 hr, cell death was pronounced. Cell death was decreased by approximately 50% after pan-caspase inhibition (Z-Val-ALa-Asp(Ome)-fluoromethylketone). These data suggest that Fas-associated DISCs assemble in neurons overexpressing Fas ligand as well as within mouse and human contused brain after TBI. Therefore, Fas may function as a death receptor after brain injury.
Qiu
Jianhua
J
Neuroscience Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA.
Whalen
Michael J
MJ
Lowenstein
Pedro
P
Fiskum
Gary
G
Fahy
Brenda
B
Darwish
Ribal
R
Aarabi
Bizhan
B
Yuan
Junying
J
Moskowitz
Michael A
MA
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001930:Brain Injuries / Q000378:metabolism* / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D018450:Disease Progression; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000378:metabolism; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D005822:Genetic Vectors / Q000235:genetics / Q000494:pharmacology; D006801:Humans; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D011233:Precipitin Tests; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; D015398:Signal Transduction; D014162:Transfection; D015854:Up-Regulation; D019014:fas Receptor / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; C505533:FADD protein, human; C505661:FASLG protein, human; C505534:Fadd protein, mouse; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; C505658:Fasl protein, mouse; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D011506:Proteins; D019014:fas Receptor; C506249:RIPK1 protein, human; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C506251:Ripk1 protein, mouse; D020169:Caspases