Tumour necrosis factor (TNF)-receptor-associated factors (TRAFs) form a family of cytoplasmic adapter proteins that mediate signal transduction from many members of the TNF-receptor superfamily and the interleukin-1 receptor. They are important in the regulation of cell survival and cell death. The carboxy-terminal region of TRAFs (the TRAF domain) is required for self-association and interaction with receptors. The domain contains a predicted coiled-coil region that is followed by a highly conserved TRAF-C domain. Here we report the crystal structure of the TRAF domain of human TRAF2, both alone and in complex with a peptide from TNF receptor-2 (TNF-R2). The structures reveal a trimeric self-association of the TRAF domain, which we confirm by studies in solution. The TRAF-C domain forms a new, eight-stranded antiparallel beta-sandwich structure. The TNF-R2 peptide binds to a conserved shallow surface depression on one TRAF-C domain and does not contact the other protomers of the trimer. The nature of the interaction indicates that an SXXE motif may be a TRAF2-binding consensus sequence. The trimeric structure of the TRAF domain provides an avidity-based explanation for the dependence of TRAF recruitment on the oligomerization of the receptors by their trimeric extracellular ligands.

Many members of the tumor necrosis factor receptor (TNFR) superfamily initiate intracellular signaling by recruiting TNFR-associated factors (TRAFs) through their cytoplasmic tails. TRAFs apparently recognize highly diverse receptor sequences. Crystal structures of the TRAF domain of human TRAF2 in complex with peptides from the TNFR family members CD40, CD30, Ox40, 4-1BB, and the EBV oncoprotein LMP1 revealed a conserved binding mode. A major TRAF2-binding consensus sequence, (P/S/A/T)x(Q/E)E, and a minor consensus motif, PxQxxD, can be defined from the structural analysis, which encompass all known TRAF2-binding sequences. The structural information provides a template for the further dissection of receptor binding specificity of TRAF2 and for the understanding of the complexity of TRAF-mediated signal transduction.

Curcumin has been shown to exhibit anti-inflammatory, antimutagenic, and anticarcinogenic activities. However, the effect of curcumin on the maturation and immunostimulatory function of dendritic cells (DC) largely remains unknown. In this study, we examined whether curcumin can influence surface molecule expression, cytokine production, and their underlying signaling pathways in murine bone marrow-derived DC. DC were derived from murine bone marrow cells and used as immature or LPS-stimulated mature cells. The DC were tested for surface molecule expression, cytokine production, dextran uptake, the capacity to induce T cell differentiation, and their underlying signaling pathways. Curcumin significantly suppressed CD80, CD86, and MHC class II expression, but not MHC class I expression, in the DC. The DC also exhibited impaired IL-12 expression and proinflammatory cytokine production (IL-1β, IL-6, and TNF-α). The curcumin-treated DC were highly efficient at Ag capture, via mannose receptor-mediated endocytosis. Curcumin inhibited LPS-induced MAPK activation and the translocation of NF-κB p65. In addition, the curcumin-treated DC showed an impaired induction of Th1 responses and a normal cell-mediated immune response. These novel findings provide new insight into the immunopharmacological role of curcumin in impacting on the DC. These novel findings open perspectives for the understanding of the immunopharmacological role of curcumin and therapeutic adjuvants for DC-related acute and chronic diseases.

The chemistry and structure of ion channels within the polymer electrolytes are of prime importance for studying the transport properties of electrolytes as well as for developing high-performance electrochemical devices. Despite intensive efforts on the synthesis of polymer electrolytes, few studies have demonstrated enhanced target ion conduction while suppressing unfavorable ion or mass transport because the undesirable transport occurs through an identical pathway. Herein, we report an innovative, chemical strategy for the synthesis of polymer electrolytes whose ion-conducting channels are physically and chemically modulated by the ionic (not electronic) conductive, functionalized graphenes and for a fundamental understanding of ion and mass transport occurring in nanoscale ionic clusters. The functionalized graphenes controlled the state of water by means of nanoscale manipulation of the physical geometry and chemical functionality of ionic channels. Furthermore, the confinement of bound water within the reorganized nanochannels of composite membranes was confirmed by the enhanced proton conductivity at high temperature and the low activation energy for ionic conduction through a Grotthus-type mechanism. The selectively facilitated transport behavior of composite membranes such as high proton conductivity and low methanol crossover was attributed to the confined bound water, resulting in high-performance fuel cells.

TRAF proteins are major mediators for the cell activation, cell survival, and antiapoptotic functions of the TNF receptor superfamily. They can be recruited to activated TNF receptors either by direct interactions with the receptors or indirectly via the adaptor protein TRADD. We now report the structure of the TRADD-TRAF2 complex, which is highly distinct from receptor-TRAF2 interactions. This interaction is significantly stronger and we show by an in vivo signaling assay that TRAF2 signaling is more readily initiated by TRADD than by direct receptor-TRAF2 interactions. TRADD is specific for TRAF1 and TRAF2, which ensures the recruitment of clAPs for the direct inhibition of caspase activation in the signaling complex. The stronger affinity and unique specificity of the TRADD-TRAF2 interaction are crucial for the suppression of apoptosis and provide a mechanistic basis for the perturbation of TRAF recruitment in sensitizing cell death induction.