title: Ectopic expression of the serine protease inhibitor PI9 modulates death receptor-mediated apoptosis.
abstract: Apoptosis is a highly controlled process, whose triggering is associated with the activation of caspases. Apoptosis can be induced via a subgroup of the tumor necrosis factor (TNF) receptor superfamily, which recruit and activate pro-caspase-8 and -10. Regulation of apoptosis is achieved by several inhibitors, including c-FLICE-inhibitory protein, which prevents apoptosis by inhibiting the pro-apoptotic activation of upstream caspases. Here we show that the human intracellular serine protease inhibitor (serpin), protease inhibitor 9 (PI9), inhibits TNF-, TNF-related apoptosis-inducing ligand- and Fas ligand-mediated apoptosis in certain TNF-sensitive cell lines. The reactive center P1 residue of PI9 was required for this inhibition since PI9 harboring a Glu --> Ala mutation in its reactive center failed to impair death receptor-induced cell death. This suggests a classical serpin-protease interaction. Indeed, PI9 inhibited apoptotic death by directly interacting with the intermediate active forms of caspase-8 and -10. This indicates that PI9 can regulate pro-apoptotic apical caspases.
authors.affiliation: Department of Biochemistry, University of Lausanne, BIL Biomedical Research Center, Chemin des Boveresses 155, CH-1066 Epalinges, Switzerland. j.a.kummer@umcutrecht.nl
authors.forename: J A
authors.initials: JA
authors.lastname: Kummer
authors.forename: O
authors.initials: O
authors.lastname: Micheau
authors.forename: P
authors.initials: P
authors.lastname: Schneider
authors.forename: N
authors.initials: N
authors.lastname: Bovenschen
authors.forename: R
authors.initials: R
authors.lastname: Broekhuizen
authors.forename: R
authors.initials: R
authors.lastname: Quadir
authors.forename: M C M
authors.initials: MC
authors.lastname: Strik
authors.forename: C E
authors.initials: CE
authors.lastname: Hack
authors.forename: J
authors.initials: J
authors.lastname: Tschopp
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053455:Caspase 10 / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D053222:Fas Ligand Protein / Q000502:physiology; D006801:Humans; D008024:Ligands; D051379:Mice; D008954:Models, Biological; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D053218:Receptors, Death Domain / Q000502:physiology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000235:genetics* / Q000502:physiology*; D015843:Serpins / Q000235:genetics* / Q000502:physiology*; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology; D014161:Transduction, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology
chemical_list: C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008024:Ligands; D053218:Receptors, Death Domain; D011994:Recombinant Proteins; C102316:SERPINB9 protein, human; D015842:Serine Proteinase Inhibitors; D015843:Serpins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; D053455:Caspase 10; D053148:Caspase 3; D053181:Caspase 8; C506438:CASP10 protein, human