title: P-glycoprotein inhibits caspase-8 activation but not formation of the death inducing signal complex (disc) following Fas ligation.
abstract: Previous studies by our laboratory have shown that the drug transporter protein P-glycoprotein, P-gp, can specifically inhibit Fas-induced caspase-3 activation and apoptosis. Importantly, inhibition of both caspase-3 activation and cell death could be reversed by pharmacological and antibody inhibitors of P-gp function. However, the molecular mechanisms underpinning P-gp-mediated resistance to Fas-induced cell death and caspase activation remained unknown. We therefore sought to identify the point(s) within the death receptor pathway at which P-gp exerted its inhibitory effect and to determine whether the ATPase activity of P-gp was required. Structure-function analysis determined that ATP hydrolysis was necessary for P-gp to confer resistance to Fas-induced caspase activation and cell death. Importantly, although both FADD and caspase-8 were recruited to the Death Inducing Signal Complex (DISC) in wild-type P-gp expressing cells following Fas ligation, subsequent activation of caspase-8 at the DISC was inhibited. The ability of P-gp to inhibit caspase-8 activation was also ATP dependent. These studies demonstrate that P-gp inhibits Fas-induced caspase-8 activation but not formation of the DISC and that this activity of P-gp is dependent on ATP hydrolysis.
authors.affiliation: Peter MacCallum Cancer Institute, St Andrew's Place, East Melbourne, Victoria, Australia.
authors.forename: A A
authors.initials: AA
authors.lastname: Ruefli
authors.forename: K M
authors.initials: KM
authors.lastname: Tainton
authors.forename: P K
authors.initials: PK
authors.lastname: Darcy
authors.forename: M J
authors.initials: MJ
authors.lastname: Smyth
authors.forename: R W
authors.initials: RW
authors.lastname: Johnstone
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D053418:Death Domain Receptor Signaling Adaptor Proteins; D053200:Fas-Associated Death Domain Protein; D005822:Genetic Vectors; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D012190:Retroviridae; D014161:Transduction, Genetic; D019014:fas Receptor / Q000378:metabolism*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D048868:Adaptor Proteins, Signal Transducing; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; D053418:Death Domain Receptor Signaling Adaptor Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D047908:Intracellular Signaling Peptides and Proteins; D018124:Receptors, Tumor Necrosis Factor; D019014:fas Receptor; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases