Investigating the function of TRAF1 in NF-κB activation

Tumour necrosis factor receptor-associated factor (TRAF) proteins play an important role in mediating the activation of NF-κB. Dysregulation of NF-κB may be one of the potential causes of chronic inflammatory diseases. One member of the TRAF family, TRAF1, has been shown to increase the risk of rheumatoid arthritis (RA). However, TRAF1 plays opposing roles in the activation of NF-κB downstream of the tumour necrosis factor receptors (TNFR) and toll-like receptors (TLR) signalling pathways. In the TNFR pathway, TRAF1 recruits c-IAP2 to promote NF-κB activation and cell proliferation. In contrast, in TLR pathways, TRAF1 negatively regulates NF-κB by sequestering the linear ubiquitin assembly complex (LUBAC). Because of the complex role of TRAF1 in NF-κB activation, it is important to isolate and study the role of TRAF1 in each of these pathways. To better understand TRAF1 and its role in NF-κB activation, our laboratory has identified the same interaction site between TRAF1 and c-IAP2 and created a mutant TRAF1V203A that significantly reduces the interaction with c-IAP2. This study creates a working functional assay to test the effect of these mutants on NF-κB activation. We have generated TRAF1V203A knock-in monocyte THP-1 cells and demonstrated how this mutant alters signalling downstream of TLR and TNFR in monocytes. This study also shows that the production of pro-inflammatory cytokines is reduced in TRAF1V203A mutant monocytes. This study helps us to isolate effects on NF-κB activation and provides an excellent model to study the role of TRAF1 in vivo.