title: Sam68 is required for both NF-κB activation and apoptosis signaling by the TNF receptor.
abstract: The RNA-binding protein Sam68 is implicated in various cellular processes including RNA metabolism, apoptosis, and signal transduction. Here we identify a role of Sam68 in TNF-induced NF-κB activation and apoptosis. We found that Sam68 is recruited to the TNF receptor, and its deficiency dramatically reduces RIP recruitment and ubiquitylation. It also impairs cIAP1 recruitment and maintenance of recruited TRAF2 at the TNF receptor. In its absence, activation of the TAK1-IKK kinase complex is defective, greatly reducing signal transduction. Sam68 is also found as a part of the TNF-induced cytoplasmic caspase-8-FADD complex. RIP is not recruited to this complex in Sam68 knockout cells, and caspase activation is virtually absent. These findings delineate previously unknown functions for Sam68 in the TNF signaling pathway, where it acts as a signaling adaptor both in the membrane-associated complex I and in the cytoplasmic complex II, regulating both NF-κB activation and apoptosis.
authors.affiliation: Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Parameswaran
authors.initials: P
authors.lastname: Ramakrishnan
authors.forename: David
authors.initials: D
authors.lastname: Baltimore
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D053200:Fas-Associated Death Domain Protein / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; D053200:Fas-Associated Death Domain Protein; C489559:KHDRBS1 protein, human; D016328:NF-kappa B; D016601:RNA-Binding Proteins; D018124:Receptors, Tumor Necrosis Factor; D053181:Caspase 8