Identification of TRAF6, a Novel Tumor Necrosis Factor Receptor-associated Factor Protein That Mediates Signaling from an Amino-terminal Domain of the CD40 Cytoplasmic Region

Abstract

CD40 signalings play crucial roles in B-cell function.To identify molecules which transduce CD40 signalings, we have utilized the yeast two-hybrid system to clone cDNAs encoding proteins that bind the cytoplasmic tail of CD40. A cDNA encoding a putative signal transducer, designated TRAF6, has been molecularly cloned. TRAF6 has a tumor necrosis factor receptor (TNFR)-associated factor (TRAF) domain in its carboxyl terminus and has a RING finger domain, a cluster of zinc fingers and a coiled-coil domain, which are also present in other TRAF family proteins. TRAF6 does not associate with the cytoplasmic tails of TNFR2, CD30, lymphotoxin-␤ receptor, and LMP1 of Epstein-Barr virus. Deletion analysis showed that residues 246 -269 of CD40 which are required for its association with TRAF2, TRAF3, and TRAF5 are dispensable for its interaction with TRAF6, whereas residues 230 -245 were required. Overexpression of TRAF6 activates transcription factor NFB, and its TRAF-C domain suppresses NFB activation triggered by CD40 lacking residues 246 -277. These results suggest that TRAF6 could mediate the CD40 signal that is transduced by the amino-terminal domain (230 -245) of the CD40 cytoplasmic region and appears to be independent of other known TRAF family proteins.

Expression of the Tumor Necrosis Factor Receptor-Associated Factors (TRAFs) 1 and 2 is a Characteristic Feature of Hodgkin and Reed-Sternberg Cells

“…Similarly, stimulation of both CD40 and TNF-R2 also result in NF-B activation mediated by TRAF2 (5,6,13). Interestingly, TRAF6 protein, as found in all three of our HD cell lines, can also amplify NF-B signaling via interaction with CD40 (1,18). In contrast, TRAF3 overexpression has been shown to suppress both CD40-and TNF-R2-induced NF-B activation (5,37).…”

“…(CD40bp/LAP1/CRAF1; 1, 9, 16, 17), TRAF5 (1,7,14), or TRAF6 (1,18). Alternatively, the function of other TNFR superfamily members, including TNF-R1 and Fas (CD95/APO-1), is not primarily mediated by TRAF protein binding.…”

Expression of Tumor Necrosis Factor Receptor-associated Factor 6 in Lung Cancer Tissues

“…Tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) has a tumor necrosis factor receptor (TNFR)-associated factor (TRAF) domain in its carboxyl terminus and has a RING finger domain, a cluster of zinc fingers and a coiled-coil domain, which are also present in other TRAF family proteins (Ishida et al, 1996). TRAF6 was firstly identified by Ishida's (Ishida et al, 1996) and it binds to the amino-terminal region of the CD40 cytoplasmic tail, which is distinct from the binding domain for TRAF2, TRAF3, and TRAF5.…”

“…TRAF6 was firstly identified by Ishida's (Ishida et al, 1996) and it binds to the amino-terminal region of the CD40 cytoplasmic tail, which is distinct from the binding domain for TRAF2, TRAF3, and TRAF5. Meanwhile, TRAF6 plays a critical role in immune (Kobayashi et al, 2003) and inflammation.…”

CD40 translocation to lipid rafts: Signaling requirements and downstream biological events

“…Notably, the CD40/CD154 interaction is critical for the affinity maturation of immunoglobulins (Ig), the development of long-lived plasma B cells and the clonal expansion of memory B cells [1,4,5]. In the absence of intrinsic tyrosine kinase activity, CD40 transmits its intracellular signal via recruitment of several adaptor proteins, such as JAK3 [6] and TNFR-associated factor (TRAF) proteins [5], to specific domains in the CD40 cytoplasmic tail [4,[7][8][9]. This results in the activation of members of the Src kinase family (such as Lyn and Fyn), and other protein tyrosine kinases (such as Syk and Btk) [10,11]; the activation of PI-3 kinase and phospholipase Cg2 [11] and the activation of the MAP kinases p38, JNK and ERK [12][13][14].…”