title: The extracellular domains of FasL and Fas are sufficient for the formation of supramolecular FasL-Fas clusters of high stability.
abstract: Using fluorescent variants of Fas and FasL, we show that membrane FasL and Fas form supramolecular clusters that are of flexible shape, but nevertheless stable and persistent. Membrane FasL-induced Fas clusters were formed in caspase-8- or FADD-deficient cells or when a cytoplasmic deletion mutant of Fas was used suggesting that cluster formation is independent of the assembly of the cytoplasmic Fas signaling complex and downstream activated signaling pathways. In contrast, cross-linked soluble FasL failed to aggregate the cytoplasmic deletion mutant of Fas, but still induced aggregation of signaling competent full-length Fas. Moreover, membrane FasL-induced Fas cluster formation occurred in the presence of the lipid raft destabilizing component methyl-beta-cyclodextrin, whereas Fas aggregation by soluble FasL was blocked. Together, these data suggest that the extracellular domains of Fas and FasL alone are sufficient to drive membrane FasL-induced formation of supramolecular Fas-FasL complexes, whereas soluble FasL-induced Fas aggregation is dependent on lipid rafts and mechanisms associated with the intracellular domain of Fas.
authors.affiliation: Department of Molecular Internal Medicine, Medical Polyclinic, University of Wuerzburg, 97070 Wuerzburg, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Henkler
authors.forename: Eva
authors.initials: E
authors.lastname: Behrle
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Dennehy
authors.forename: Andreas
authors.initials: A
authors.lastname: Wicovsky
authors.forename: Nathalie
authors.initials: N
authors.lastname: Peters
authors.forename: Clemens
authors.initials: C
authors.lastname: Warnke
authors.forename: Klaus
authors.initials: K
authors.lastname: Pfizenmaier
authors.forename: Harald
authors.initials: H
authors.lastname: Wajant
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D017209:Apoptosis / Q000502:physiology*; D053181:Caspase 8; D020169:Caspases / Q000235:genetics; D003593:Cytoplasm / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism*; D009154:Mutation / Q000502:physiology; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D012995:Solubility / Q000187:drug effects; D047392:beta-Cyclodextrins / Q000494:pharmacology; D019014:fas Receptor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C505533:FADD protein, human; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D047392:beta-Cyclodextrins; D019014:fas Receptor; C108732:methyl-beta-cyclodextrin; C505530:CASP8 protein, human; D053181:Caspase 8; D020169:Caspases