Abstract
TNF receptor-1 (TNF-R1) signal transduction is mediated through the assembly of scaffolding proteins, adaptors, and kinases. TNF receptor ubiquitous scaffolding and signaling protein (TRUSS), a 90.1 kDa TNF-R1-associated scaffolding protein, also interacts with TRAF2 and IKK and contributes to TNF-alpha-induced nuclear factor-kappaB (NF-kappaB) and c-Jun-NH(2)-terminal kinase (JNK) activation. Little is known about the mechanism of interaction among TRUSS, TNF-R1, and TRAF2. To address this issue, we used deletional and site-directed mutagenesis approaches to systematically investigate (i) the regions of TRUSS that interact with TNF-R1 and TRAF2 and (ii) the ability of TRUSS to self-associate to form higher-order complexes. Here we show that sequences located in the N-terminal (residues 1-248) and central (residues 249-440) regions of TRUSS are required to form a docking interface that supports binding to both TNF-R1 and TRAF2. While the C-terminal region (residues 441-797) did not directly interact with TNF-R1 or TRAF2, sequences located in this region were capable of self-association. Collectively, these data suggest that (i) the interaction between TNF-R1 and TRAF2 requires sequences located in the entire N-terminal half (residues 1-440) of TRUSS, (ii) the binding interface for TNF-R1 is closely linked with the TRAF2 binding interface, and (iii) the assembly of homomeric TRUSS complexes may contribute to its role in TNF-R1 signaling.