Cooperation of both TNF receptors in inducing apoptosis: involvement of the TNF receptor-associated factor binding domain of the TNF receptor 75.
TNF-R55 is the main receptor mediating TNF-induced cytotoxicity. However, in some cells TNF-R75 also signals cell death. In PC60 cells, the presence of both receptor types is required to induce apoptosis following either specific TNF-R55 or TNF-R75 triggering, pointing to a mechanism of receptor cooperation. In this study, we extend previous observations and show that TNF-R55 and TNF-R75 cooperation in the case of apoptosis in PC60 cells is bidirectional. We also demonstrate ligand-independent TNF-R55-mediated cooperation in TNF-R75-induced granulocyte/macrophage-CSF secretion, but not vice versa. To determine which part of the intracellular TNF-R75 sequence was responsible for the observed receptor cooperation in apoptosis, we introduced different TNF-R75 mutant constructs in PC60 cells already expressing TNF-R55. Our data indicate that an intact TNF-R-associated factors 1 and 2 (TRAF1/TRAF2)-binding domain is required for receptor cooperation. These findings suggest a role for the TRAF complex in TNF-R cooperation in the induction of cell death in PC60 cells. Nevertheless, introduction of a dominant negative (DN) TRAF2 molecule was not able to affect receptor cooperation. Remarkably, TRAF2-DN overexpression, which was found to inhibit the TNF-dependent recruitment of endogenous wild-type TRAF2 to the TNF-R75 signaling complex, could neither block TNF-R55- or TNF-R75-induced NF-kappaB activation nor granulocyte/macrophage-CSF secretion. Possibly, additional factors different from TRAF2 are involved in TNF-mediated NF-kappaB activation.
Declercq
W
W
Laboratory of Molecular Biology, Flanders Interuniversity Institute for Biotechnology, University of Ghent, Belgium.
Denecker
G
G
Fiers
W
W
Vandenabeele
P
P
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D017209:Apoptosis / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D015870:Gene Expression / Q000276:immunology; D006801:Humans; D006825:Hybridomas; D051379:Mice; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional / Q000276:immunology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D018124:Receptors, Tumor Necrosis Factor / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D017384:Sequence Deletion / Q000276:immunology; D012694:Serine / Q000235:genetics; D047990:TNF Receptor-Associated Factor 1; D047992:TNF Receptor-Associated Factor 2
D015703:Antigens, CD; D016328:NF-kappa B; D011506:Proteins; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D047990:TNF Receptor-Associated Factor 1; D047992:TNF Receptor-Associated Factor 2; D012694:Serine