Role of TRAF3 and -6 in the Activation of the NF-κB and JNK Pathways by X-linked Ectodermal Dysplasia Receptor*

Abstract

X-linked ectodermal dysplasia receptor (XEDAR) is a recently isolated member of the tumor necrosis factor receptor family that has been shown to be highly expressed in ectodermal derivatives during embryonic development and binds to ectodysplasin-A2 (EDA-A2). By using a subclone of 293F cells with stable expression of XEDAR, we report that XEDAR activates the NF-κB and JNK pathways in an EDA-A2-dependent fashion. Treatment with EDA-A2 leads to the recruitment of TRAF3 and -6 to the aggregated XEDAR complex, suggesting a central role of these adaptors in the proximal aspect of XEDAR signaling. Whereas TRAF3 and -6, IKK1/IKKα, IKK2/IKKβ, and NEMO/IKKγ are involved in XEDAR-induced NF-κB activation, XEDAR-induced JNK activation seems to be mediated via a pathway dependent on TRAF3, TRAF6, and ASK1. Deletion and point mutagenesis studies delineate two distinct regions in the cytoplasmic domain of XEDAR, which are involved in binding to TRAF3 and -6, respectively, and play a major role in the activation of the NF-κB and JNK pathways. Taken together, our results establish a major role of TRAF3 and -6 in XEDAR signaling and in the process of ectodermal differentiation.