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Tak W Mak - One of the best experts on this subject based on the ideXlab platform.

  • Activation of noncanonical NF-κB requires coordinated assembly of a regulatory complex of the adaptors cIAP1, cIAP2, TRAF2, TRAF3 and the kinase NIK
    2016
    Co-Authors: Brian J. Zarnegar, Wen Chen Yeh, Paul W Dempsey, Yaya Wang, Douglas J. Mahoney, Herman H, Travis Shiba, Xiaolu Yang, Tak W Mak
    Abstract:

    Recent studies suggest that nuclear factor κB-inducing kinase (NIK) is suppressed through constitutive proteasome-mediated degradation regulated by TRAF2, TRAF3 and cIAP1 or cIAP2. Here, we demonstrated that the degradation of NIK occurred upon assembly of a regulatory complex through TRAF3 recruitment of NIK and TRAF2 recruitment of cIAP1 and cIAP2. In contrast to TRAF2 and TRAF3, cIAP1 and cIAP2 seem to play redundant roles in the degradation of NIK, as inhibition of both cIAPs was required for noncanonical NF-κB activation and increased survival and proliferation of primary B lymphocytes. Furthermore, the lethality of TRAF3-deficient mice could be rescued by a single NIK gene, highlighting the importance of tightly regulated NIK. The Rel-NF-κB family of transcription factors has a tremendous impact on numerous biological processes, including bone homeostasis, cellular proliferation and apoptosis, the initiation and propagation of innate and adaptive immune responses, and the development of secondary lymphoid tissue architecture1–3. Research in recent years has defined two distinct NF-κB activation pathways, termed the canonical and noncanonical NF-κB pathways4

  • opposing roles for TRAF1 in the alternative versus classical nf κb pathway in t cells
    Journal of Biological Chemistry, 2012
    Co-Authors: Ann J Mcpherson, Tak W Mak, Laura Snell, Tania H Watts
    Abstract:

    T cells lacking TRAF1 hyperproliferate in response to T cell receptor signaling but have impaired signaling downstream of specific TNFR family members such as 4-1BB. Here we resolve this paradox by showing that while TRAF1 is required for maximal activation of the classical NF-κB pathway downstream of 4-1BB in primary T cells, TRAF1 also restricts the constitutive activation of NIK in anti-CD3-activated T cells. Activation of the alternative NF-κB pathway is restricted in unstimulated cells by a cIAP1/2:TRAF2:TRAF3:NIK complex. Using knockdown of NIK by siRNA we show that in activated CD8 T cells TRAF1 is also involved in this process and that constitutive activation of the alternative NF-κB pathway is responsible for costimulation independent hyperproliferation and excess cytokine production in TRAF1-deficient CD8 T cells compared with WT CD8 T cells. The T cell costimulatory molecule 4-1BB critically regulates the survival of activated and memory CD8 T cells. We demonstrate that stimulation through 4-1BB induces cIAP1-dependent TRAF3 degradation and activation of the alternative NF-κB pathway. We also show that while both TRAF1 and cIAP1 have non-redundant roles in suppressing the alternative NF-κB pathway in T cells activated in the absence of costimulation, activation of the classical NF-κB pathway downstream of 4-1BB requires TRAF1, whereas cIAP1 plays a redundant role with cIAP2. Collectively these results demonstrate that TRAF1 plays a critical role in regulating T cell activation both through restricting the costimulation independent activation of NIK in activated T cells and by promoting the 4-1BB-induced classical NF-κB pathway.

  • epstein barr virus latent membrane protein 1 activation of nf κb through irak1 and traf6
    Proceedings of the National Academy of Sciences of the United States of America, 2003
    Co-Authors: Micah A Luftig, Hiroyasu Nakano, E E Prinarakis, Teruhito Yasui, Theodore Tsichritzis, Ellen Cahirmcfarland, Junichiro Inoue, Tak W Mak, Wen Chen Yeh, Shizuo Akira
    Abstract:

    Epstein–Barr virus latent membrane protein 1 (LMP1) activation of NF-κB is critical for Epstein–Barr virus-infected B lymphocyte survival. LMP1 activates the IκB kinase complex and NF-κB through two cytoplasmic signaling domains that engage tumor necrosis factor receptor-associated factor (TRAF)1/2/3/5 or TRADD and RIP. We now use cells lacking expression of TRAF2, TRAF5, TRAF6, IKKα, IKKβ, IKKγ, TAB2, IL-1 receptor-associated kinase (IRAK)1, or IRAK4 to assess their roles in LMP1-mediated NF-κB activation. LMP1-induced RelA nuclear translocation was similar in IKKα knockout (KO) and WT murine embryo fibroblasts (MEFs) but substantially deficient in IKKβ KO MEFs. NF-κB-dependent promoter responses were also substantially deficient in IKKβ KO MEFs but were hyperactive in IKKα KO MEFs. More surprisingly, NF-κB responses were near normal in TRAF2 and TRAF5 double-KO MEFs, IKKγ KO MEFs, TAB2 KO MEFs, and IRAK4 KO MEFs but were highly deficient in TRAF6 KO MEFs and IRAK1 KO HEK293 cells. Consistent with the importance of TRAF6, LMP1-induced NF-κB activation in HEK293 cells was inhibited by expression of dominant-negative TAB2 and Ubc13 alleles. These data extend a role for IKKα in IKKβ regulation, identify an unusual IKKβ-dependent and IKKγ-independent NF-κB activation, and indicate that IRAK1 and TRAF6 are essential for LMP1-induced NF-κB activation.

  • traf6 is a critical mediator of signal transduction by the viral oncogene latent membrane protein 1
    The EMBO Journal, 2001
    Co-Authors: Ute Schultheiss, Tak W Mak, Wolfgang Hammerschmidt, Stephanie Puschner, Hartmut Engelmann, Elisabeth Kremmer, Arnd Kieser
    Abstract:

    The oncogenic latent membrane protein 1 (LMP1) of the Epstein–Barr virus recruits tumor necrosis factor‐receptor (TNFR)‐associated factors (TRAFs), the TNFR‐associated death domain protein (TRADD) and JAK3 to induce intracellular signaling pathways. LMP1 serves as the prototype of a TRADD‐binding receptor that transforms cells but does not induce apoptosis. Here we show that TRAF6 critically mediates LMP1 signaling to p38 mitogen‐activated protein kinase (MAPK) via a MAPK kinase 6‐dependent pathway. In addition, NF‐κB but not c‐Jun N‐terminal kinase 1 (JNK1) induction by LMP1 involves TRAF6. The PxQxT motif of the LMP1 C‐terminal activator region 1 (CTAR1) and tyrosine 384 of CTAR2 together are essential for full p38 MAPK activation and for TRAF6 recruitment to the LMP1 signaling complex. Dominant‐negative TRADD blocks p38 MAPK activation by LMP1. The data suggest that entry of TRAF6 into the LMP1 complex is mediated by TRADD and TRAF2. In TRAF6‐knockout fibroblasts, significant induction of p38 MAPK by LMP1 is dependent on the ectopic expression of TRAF6. We describe a novel role of TRAF6 as an essential signaling mediator of a transforming oncogene, downstream of TRADD and TRAF2.

  • critical roles of traf2 and traf5 in tumor necrosis factor induced nf κb activation and protection from cell death
    Journal of Biological Chemistry, 2001
    Co-Authors: Kurisu Tada, Tak W Mak, Tatsuma Okazaki, Sachiko Sakon, Tomonari Kobarai, Kyoko Kurosawa, Shoji Yamaoka, Hiroshi Hashimoto, Hideo Yagita
    Abstract:

    Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) were identified as signal transducers for the TNF receptor superfamily. However, the exact roles of TRAF2 and TRAF5 in TNF-induced NF-κB activation still remain controversial. To address this issue, we generated TRAF2 and TRAF5 double knockout (DKO) mice. TNF- but not interleukin-1-induced nuclear translocation of NF-κB was severely impaired in murine embryonic fibroblasts (MEFs) derived from DKO mice. Moreover, DKO MEFs were more susceptible to TNF-induced cytotoxicity than TRAF2 knockout MEFs. Collectively, these results indicate that both TRAF2 and TRAF5 are involved in TNF-induced NF-κB activation and protection from cell death.

Hiroyasu Nakano - One of the best experts on this subject based on the ideXlab platform.

  • recruitment of tumor necrosis factor receptor associated factor family proteins to apoptosis signal regulating kinase 1 signalosome is essential for oxidative stress induced cell death
    Journal of Biological Chemistry, 2005
    Co-Authors: Takuya Noguchi, Hiroyasu Nakano, Junichiro Inoue, Kohsuke Takeda, Jin Gohda, Atsushi Matsuzawa, Kaoru Saegusa, Hidenori Ichijo
    Abstract:

    Apoptosis signal-regulating kinase 1 (ASK1) plays a pivotal role in oxidative stress-induced cell death. Reactive oxygen species disrupt the interaction of ASK1 with its cellular inhibitor thioredoxin and thereby activates ASK1. However, the precise mechanism by which ASK1 freed from thioredoxin undergoes oligomerization-dependent activation has not been fully elucidated. Here we show that endogenous ASK1 constitutively forms a high molecular mass complex including Trx ( approximately 1,500-2,000 kDa), which we designate ASK1 signalosome. Upon H(2)O(2) treatment, the ASK1 signalosome forms a higher molecular mass complex at least in part because of the recruitment of tumor necrosis factor receptor-associated factor 2 (TRAF2) and TRAF6. Consistent with our previous findings that TRAF2 and TRAF6 activate ASK1, H(2)O(2)-induced ASK1 activation and cell death were strongly reduced in the cells derived from Traf2-/- and Traf6-/- mice. A novel signaling complex including TRAF2, TRAF6, and ASK1 may thus be the key component in oxidative stress-induced cell death.

  • epstein barr virus latent membrane protein 1 activation of nf κb through irak1 and traf6
    Proceedings of the National Academy of Sciences of the United States of America, 2003
    Co-Authors: Micah A Luftig, Hiroyasu Nakano, E E Prinarakis, Teruhito Yasui, Theodore Tsichritzis, Ellen Cahirmcfarland, Junichiro Inoue, Tak W Mak, Wen Chen Yeh, Shizuo Akira
    Abstract:

    Epstein–Barr virus latent membrane protein 1 (LMP1) activation of NF-κB is critical for Epstein–Barr virus-infected B lymphocyte survival. LMP1 activates the IκB kinase complex and NF-κB through two cytoplasmic signaling domains that engage tumor necrosis factor receptor-associated factor (TRAF)1/2/3/5 or TRADD and RIP. We now use cells lacking expression of TRAF2, TRAF5, TRAF6, IKKα, IKKβ, IKKγ, TAB2, IL-1 receptor-associated kinase (IRAK)1, or IRAK4 to assess their roles in LMP1-mediated NF-κB activation. LMP1-induced RelA nuclear translocation was similar in IKKα knockout (KO) and WT murine embryo fibroblasts (MEFs) but substantially deficient in IKKβ KO MEFs. NF-κB-dependent promoter responses were also substantially deficient in IKKβ KO MEFs but were hyperactive in IKKα KO MEFs. More surprisingly, NF-κB responses were near normal in TRAF2 and TRAF5 double-KO MEFs, IKKγ KO MEFs, TAB2 KO MEFs, and IRAK4 KO MEFs but were highly deficient in TRAF6 KO MEFs and IRAK1 KO HEK293 cells. Consistent with the importance of TRAF6, LMP1-induced NF-κB activation in HEK293 cells was inhibited by expression of dominant-negative TAB2 and Ubc13 alleles. These data extend a role for IKKα in IKKβ regulation, identify an unusual IKKβ-dependent and IKKγ-independent NF-κB activation, and indicate that IRAK1 and TRAF6 are essential for LMP1-induced NF-κB activation.

  • the atypical pkc interacting protein p62 channels nf κb activation by the il 1 traf6 pathway
    The EMBO Journal, 2000
    Co-Authors: Laura Sanz, Hiroyasu Nakano, Maria T Diazmeco, Jorge Moscat
    Abstract:

    The atypical protein kinase C (aPKC)-interacting protein, p62, has previously been shown to interact with RIP, linking these kinases to NF–κB activation by tumor necrosis factor α (TNFα). The aPKCs have been implicated in the activation of IKKβ in TNFα-stimulated cells and have been shown to be activated in response to interleukin–1 (IL–1). Here we demon– strate that the inhibition of the aPKCs or the down-regulation of p62 severely abrogates NF–κB activation by IL–1 and TRAF6, suggesting that both proteins are critical intermediaries in this pathway. Consistent with this we show that p62 selectively interacts with the TRAF domain of TRAF6 but not that of TRAF5 or TRAF2 in co-transfection experiments. The binding of endogenous p62 to TRAF6 is stimulus dependent, reinforcing the notion that this is a physiologically relevant interaction. Furthermore, we demonstrate that the N–terminal domain of TRAF6, which is required for signaling, interacts with ζPKC in a dimerization-dependent manner. Together, these results indicate that p62 is an important intermediary not only in TNFα but also in IL–1 signaling to NF–κB through the specific adapters RIP and TRAF6.

  • ask1 is essential for jnk sapk activation by traf2
    Molecular Cell, 1998
    Co-Authors: Hideki Nishitoh, Mike Rothe, Hiroyasu Nakano, Masao Saitoh, Yoshiyuki Mochida, Kohsuke Takeda, Kohei Miyazono
    Abstract:

    Tumor necrosis factor (TNF)-induced activation of the c-jun N-terminal kinase (JNK, also known as SAPK; stress-activated protein kinase) requires TNF receptor-associated factor 2 (TRAF2). The apoptosis signal-regulating kinase 1 (ASK1) is activated by TNF and stimulates JNK activation. Here we show that ASK1 interacts with members of the TRAF family and is activated by TRAF2, TRAF5, and TRAF6 overexpression. A truncated derivative of TRAF2, which inhibits JNK activation by TNF, blocks TNF-induced ASK1 activation. A catalytically inactive mutant of ASK1 is a dominant-negative inhibitor of TNF- and TRAF2-induced JNK activation. In untransfected mammalian cells, ASK1 rapidly associates with TRAF2 in a TNF-dependent manner. Thus, ASK1 is a mediator of TRAF2-induced JNK activation.

  • cd27 a member of the tumor necrosis factor receptor superfamily activates nf kappab and stress activated protein kinase c jun n terminal kinase via traf2 traf5 and nf kappab inducing kinase
    Journal of Biological Chemistry, 1998
    Co-Authors: Hisaya Akiba, Shigeyuki Nishinaka, Nikolai Malinin, Masahisa Shindo, Machiko Atsuta, Carl F. Ware, Tetsuji Kobata, Chikao Morimoto, Hiroyasu Nakano, David Wallach
    Abstract:

    Abstract CD27 is a member of the tumor necrosis factor (TNF) receptor superfamily and is expressed on T, B, and NK cells. The signal via CD27 plays pivotal roles in T-T and T-B cell interactions. Here we demonstrate that overexpression of CD27 activates NF-κB and stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK). Deletion analysis of the cytoplasmic domain of CD27 revealed that the C-terminal PIQEDYR motif was indispensable for both NF-κB and SAPK/JNK activation and was also required for the interaction with TNF receptor-associated factor (TRAF) 2 and TRAF5, both of which have been implicated in NF-κB activation by members of the TNF-R superfamily. Co-transfection of a dominant negative TRAF2 or TRAF5 blocked NF-κB and SAPK/JNK activation induced by CD27. Recently, a TRAF2-interacting kinase has been identified, termed NF-κB-inducing kinase (NIK). A kinase-inactive mutant NIK blocked CD27-, TRAF2-, and TRAF5-mediated NF-κB and SAPK/JNK activation. These results indicate that TRAF2 and TRAF5 are involved in NF-κB and SAPK/JNK activation by CD27, and NIK is a common downstream kinase of TRAF2 and TRAF5 for NF-κB and SAPK/JNK activation.

Elliott Kieff - One of the best experts on this subject based on the ideXlab platform.

  • the residues between the two transformation effector sites of epstein barr virus latent membrane protein 1 are not critical for b lymphocyte growth transformation
    Journal of Virology, 1999
    Co-Authors: Kenneth M Izumi, Ellen Cahir Mcfarland, Elisabeth A Riley, Danielle Rizzo, Yuzhi Chen, Elliott Kieff
    Abstract:

    Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) is essential for EBV-mediated transformation of primary B lymphocytes. LMP1 spontaneously aggregates in the plasma membrane and enables two transformation effector sites (TES1 and TES2) within the 200-amino-acid cytoplasmic carboxyl terminus to constitutively engage the tumor necrosis factor receptor (TNFR)-associated factors TRAF1, TRAF2, TRAF3, and TRAF5 and the TNFR-associated death domain proteins TRADD and RIP, thereby activating NF-κB and c-Jun N-terminal kinase (JNK). To investigate the importance of the 60% of the LMP1 carboxyl terminus that lies between the TES1-TRAF and TES2-TRADD and -RIP binding sites, an EBV recombinant was made that contains a specific deletion of LMP1 codons 232 to 351. Surprisingly, the deletion mutant was similar to wild-type (wt) LMP1 EBV recombinants in its efficiency in transforming primary B lymphocytes into lymphoblastoid cell lines (LCLs). Mutant and wt EBV-transformed LCLs were similarly efficient in long-term outgrowth and in regrowth after endpoint dilution. Mutant and wt LMP1 proteins were also similar in their constitutive association with TRAF1, TRAF2, TRAF3, TRADD, and RIP. Mutant and wt EBV-transformed LCLs were similar in steady-state levels of Bcl2, JNK, and activated JNK proteins. The wt phenotype of recombinants with LMP1 codons 232 to 351 deleted further demarcates TES1 and TES2, underscores their central importance in B-lymphocyte growth transformation, and provides a new perspective on LMP1 sequence variation between TES1 and TES2.

  • the structural basis for the recognition of diverse receptor sequences by traf2
    Molecular Cell, 1999
    Co-Authors: Young Chul Park, Mara Kreishman, Elliott Kieff
    Abstract:

    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.

  • association of TRAF1 traf2 and traf3 with an epstein barr virus lmp1 domain important for b lymphocyte transformation role in nf kappab activation
    Molecular and Cellular Biology, 1996
    Co-Authors: Odile Devergne, E Hatzivassiliou, Kenneth M Izumi, Kenneth M Kaye, M F Kleijnen, Elliott Kieff, George Mosialos
    Abstract:

    The Epstein-Barr virus (EBV) transforming protein LMP1 appears to be a constitutively activated tumor necrosis factor receptor (TNFR) on the basis of an intrinsic ability to aggregate in the plasma membrane and an association of its cytoplasmic carboxyl terminus (CT) with TNFR-associated factors (TRAFs). We now show that in EBV-transformed B lymphocytes most of TRAF1 or TRAF3 and 5% of TRAF2 are associated with LMP1 and that most of LMP1 is associated with TRAF1 or TRAF3. TRAF1, TRAF2, and TRAF3 bind to a single site in the LMP1 CT corresponding to amino acids (aa) 199 to 214, within a domain which is important for B-lymphocyte growth transformation (aa 187 to 231). Further deletional and alanine mutagenesis analyses and comparison with TRAF binding sequences in CD40, in CD30, and in the LMP1 of other lymphycryptoviruses provide the first evidence that PXQXT/S is a core TRAF binding motif. The negative effects of point mutations in the LMP1(1-231) core TRAF binding motif on TRAF binding and NF-kappaB activation genetically link the TRAFs to LMP1(1-231)-mediated NF-kappaB activation. NF-kappaB activation by LMP1(1-231) is likely to be mediated by TRAF1/TRAF2 heteroaggregates since TRAF1 is unique among the TRAFs in coactivating NF-kappaB with LMP1(1-231), a TRAF2 dominant-negative mutant can block LMP1(1-231)-mediated NF-kappaB activation as well as TRAF1 coactivation, and 30% of TRAF2 is associated with TRAF1 in EBV-transformed B cells. TRAF3 is a negative modulator of LMP1(1-231)-mediated NF-kappaB activation. Surprisingly, TRAF1, -2, or -3 does not interact with the terminal LMP1 CT aa 333 to 386 which can independently mediate NF-kappaB activation. The constitutive association of TRAFs with LMP1 through the aa 187 to 231 domain which is important in NF-kappaB activation and primary B-lymphocyte growth transformation implicates TRAF aggregation in LMP1 signaling.

  • 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
    Journal of Biological Chemistry, 1996
    Co-Authors: Takaomi Ishida, George Mosialos, Seiichi Mizushima, Sakura Azuma, Norihiko Kobayashi, Tadashi Tojo, Kimie Suzuki, Shigemi Aizawa, Toshiki Watanabe, Elliott Kieff
    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-beta 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 NFkappaB, and its TRAF-C domain suppresses NFkappaB 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.

Gail A. Bishop - One of the best experts on this subject based on the ideXlab platform.

  • roles of tumor necrosis factor receptor associated factor 3 traf3 and traf5 in immune cell functions
    Immunological Reviews, 2011
    Co-Authors: Joanne M Hildebrand, Claire M. Buchta, Jayakumar S Poovassery, Laura L Stunz, Gail A. Bishop
    Abstract:

    A large and diverse group of receptors utilizes the family of cytoplasmic signaling proteins known as tumor necrosis factor receptor (TNFR)-associated factors (TRAFs). In recent years, there has been a resurgence of interest and exploration of the roles played by TRAF3 and TRAF5 in cellular regulation, particularly in cells of the immune system, the cell types of focus in this review. This work has revealed that TRAF3 and TRAF5 can play diverse roles for different receptors even in the same cell type, as well as distinct roles in different cell types. Evidence indicates that TRAF3 and TRAF5 play important roles beyond the TNFR-superfamily (SF) and viral mimics of its members, mediating certain innate immune receptor and cytokine receptor signals, and most recently, signals delivered by the T-cell receptor (TCR) signaling complex. Additionally, much research has demonstrated the importance of TRAF3-mediated cellular regulation via its cytoplasmic interactions with additional signaling proteins. In particular, we discuss below evidence for the participation by TRAF3 in a number of the regulatory post-translational modifications involving ubiquitin that are important in various signaling pathways.

  • tumor necrosis factor receptor associated factor 2 traf2 deficient b lymphocytes reveal novel roles for traf2 in cd40 signaling
    Journal of Biological Chemistry, 2003
    Co-Authors: Bruce S Hostager, Sokol Haxhinasto, Gail A. Bishop, Sarah L Rowland
    Abstract:

    CD40 function is initiated by tumor necrosis factor (TNF) receptor-associated factor (TRAF) adapter proteins, which play important roles in signaling by numerous receptors. Characterizing roles of individual TRAFs has been hampered by limitations of available experimental models and the poor viability of most TRAF-deficient mice. Here, B cell lines made deficient in TRAF2 using a novel homologous recombination system reveal new roles for TRAF2. We demonstrate that TRAF2 participates in synergy between CD40 and B cell antigen receptor signals, and in CD40-mediated, TNF-dependent IgM production. We also find that TRAF2 participates in the degradation of TRAF3 associated with CD40 signaling, a role that may limit inhibitory actions of TRAF3. Finally, we show that TRAF2 and TRAF6 have overlapping functions in CD40-mediated NF-κB activation and CD80 up-regulation. These findings demonstrate previously unappreciated roles for TRAF2 in signaling by TNF receptor family members, using an approach that facilitates the analysis of genes critical to the viability of whole organisms.

  • regulation of traf2 signaling by self induced degradation
    Journal of Biological Chemistry, 2002
    Co-Authors: Kevin D Brown, Bruce S Hostager, Gail A. Bishop
    Abstract:

    Receptors belonging to the tumor necrosis factor receptor (TNF-R) family utilize cytoplasmic adapter proteins called TNF-R-associated factors (TRAFs) as key elements in their signaling pathways. However, it is not yet clear how individual TRAFs regulate signaling by this large and growing receptor family. Signaling via the TNF-R family member CD40 has recently been shown to result in recruitment of TRAF2 to plasma membrane detergent-resistant microdomains (lipid rafts) as well as to subsequently initiate TRAF2 degradation. As TRAF2 associates with most members of the TNF-R family, we wished to determine how this degradation occurs. We show here that CD40-mediated TRAF2 degradation requires the zinc-binding RING domain of TRAF2 and is preceded by TRAF2 ubiquitination, suggesting that the TRAF2 RING may promote ubiquitination although the RING itself is not a target of ubiquitination. Several approaches show that ubiquitination and proteasomal activity are integral to TRAF2 degradation, and inhibition of this process potentiates CD40 signaling.

  • characterization of the roles of tnf receptor associated factor 6 in cd40 mediated b lymphocyte effector functions
    Journal of Immunology, 2000
    Co-Authors: Sangita V Jalukar, Bruce S Hostager, Gail A. Bishop
    Abstract:

    Signaling through CD40 in B cells leads to B cell proliferation, Ig and IL-6 secretion, isotype switching, and up-regulation of surface molecules. TNF receptor-associated factor (TRAF) proteins associate with the cytoplasmic tail of CD40 and act as adapter molecules. Of the six TRAFs identified to date, TRAFs 2, 3, 5, and 6 are reported to associate directly with the cytoplasmic tail of CD40, but previous studies have principally examined transient overexpression of TRAF6 in cells that do not normally express CD40. Thus, we examined the role of TRAF6 in CD40-mediated B lymphocyte effector functions using two approaches. We produced and stably expressed in mouse B cell lines a human CD40 molecule with two cytoplasmic domain point mutations (hCD40EEAA); this mutant fails to bind TRAF6, while showing normal association with TRAFs 2 and 3. We also inducibly expressed in B cells a transfected “dominant-negative” TRAF6 molecule which contains only the C-terminal TRAF-binding domain of TRAF6. Using both molecules, we found that TRAF6 association with CD40 is important for CD40-induced IL-6 and Ig secretion, and that TRAF6 mediates its effects on CD40-stimulated Ig secretion principally through its effects on IL-6 production by the B cell. TRAF6 association with CD40 was also found to be important for B7-1 up-regulation, but not for up-regulation of other surface molecules. Interestingly, however, although we could show TRAF6-dependent CD40-mediated activation of NF-κB in 293 kidney epithelial cells, no such effect was seen in B cells, suggesting that TRAF6 has cell-type-specific functions.

  • cutting edge contrasting roles of tnf receptor associated factor 2 traf2 and traf3 in cd40 activated b lymphocyte differentiation
    Journal of Immunology, 1999
    Co-Authors: Bruce S Hostager, Gail A. Bishop
    Abstract:

    In B lymphocytes, CD40 signals contribute to the activation of Ab secretion, isotype switching, T cell costimulation, and immunological memory. TRAF proteins appear to be important components of the CD40 signal transduction complex, but their roles in the activation of B cell effector functions are poorly understood. We examined the contributions of TNF receptor-associated factor 2 (TRAF2) and TRAF3 to CD40-activated differentiation in mouse B cells transfected with inducible TRAF and dominant-negative TRAF cDNAs. We find that binding of TRAF2 and TRAF3 to CD40 is not required for the induction of Ab secretion, but that both TRAF molecules can regulate the activation process. We demonstrate a negative regulatory role for TRAF3 and that this activity is dependent on the availability of an intact TRAF3-binding site in the cytoplasmic domain of CD40. In contrast, TRAF2 appears to play a positive role in B cell differentiation, and this activity is apparent even when its binding site on CD40 is disrupted.

Genhong Cheng - One of the best experts on this subject based on the ideXlab platform.

  • crystal structures of the traf2 ciap2 and the TRAF1 traf2 ciap2 complexes affinity specificity and regulation
    Molecular Cell, 2010
    Co-Authors: Chao Zheng, Venkataraman Kabaleeswaran, Yaya Wang, Genhong Cheng
    Abstract:

    Summary TRAF1/2 and cIAP1/2 are members of the TNF receptor-associated factor (TRAF) and the inhibitor of apoptosis (IAP) families, respectively. They are critical for canonical and noncanonical NF-κB signaling pathways. Here, we report the crystal structures of the TRAF2: cIAP2 and the TRAF1: TRAF2: cIAP2 complexes. A TRAF2 trimer interacts with one cIAP2 both in the crystal and in solution. Two chains of the TRAF2 trimer directly contact cIAP2, and key residues at the interface are confirmed by mutagenesis. TRAF1 and TRAF2 preferentially form the TRAF1: (TRAF2) 2 heterotrimer, which interacts with cIAP2 more strongly than TRAF2 alone. In contrast, TRAF1 alone interacts very weakly with cIAP2. Surprisingly, TRAF1 and one chain of TRAF2 in the TRAF1: (TRAF2) 2 : cIAP2 ternary complex mediate interaction with cIAP2. Because TRAF1 is upregulated by many stimuli, it may modulate the interaction of TRAF2 with cIAP1/2, which explains regulatory roles of TRAF1 in TNF signaling.

  • control of canonical nf κb activation through the nik ikk complex pathway
    Proceedings of the National Academy of Sciences of the United States of America, 2008
    Co-Authors: Brian Zarnegar, Soh Yamazaki, Genhong Cheng
    Abstract:

    Articles in recent years have described two separate and distinct NF-κB activation pathways that result in the differential activation of p50- or p52-containing NF-κB complexes. Studies examining tumor-necrosis factor receptor-associated factors (TRAFs) have identified positive roles for TRAF2, TRAF5, and TRAF6, but not TRAF3, in canonical (p50-dependent) NF-κB activation. Conversely, it recently was reported that TRAF3 functions as an essential negative regulator of the noncanonical (p52-dependent) NF-κB pathway. In this article, we provide evidence that TRAF3 potently suppresses canonical NF-κB activation and gene expression in vitro and in vivo. We also demonstrate that deregulation of the canonical NF-κB pathway in TRAF3-deficient cells results from accumulation of NF-κB-inducing kinase (NIK), the essential kinase mediating noncanonical NF-κB activation. Thus, our data demonstrate that inhibition of TRAF3 results in coordinated activation of both NF-κB activation pathways.

  • specificities of cd40 signaling involvement of traf2 in cd40 induced nf κb activation and intercellular adhesion molecule 1 up regulation
    Proceedings of the National Academy of Sciences of the United States of America, 1999
    Co-Authors: Ho H Lee, David Baltimore, Paul W Dempsey, Thomas P Parks, Xiaoqing Zhu, Genhong Cheng
    Abstract:

    Several tumor necrosis factor receptor-associated factor (TRAF) family proteins including TRAF2, TRAF3, TRAF5, and TRAF6, as well as Jak3, have been implicated as potential mediators of CD40 signaling. An extensive in vitro binding study indicated that TRAF2 and TRAF3 bind to the CD40 cytoplasmic tail (CD40ct) with much higher affinity than TRAF5 and TRAF6 and that TRAF2 and TRAF3 bind to different residues of the CD40ct. Using CD40 mutants incapable of binding TRAF2, TRAF3, or Jak3, we found that the TRAF2-binding site of the CD40ct is critical for NF-kappa B and stress-activated protein kinase activation, as well as the up-regulation of the intercellular adhesion molecule-1 (ICAM-1) gene, whereas binding of TRAF3 and Jak3 is dispensable for all of these functions. Overexpression of a dominantly active I kappa B alpha strongly inhibited CD40-induced NF-kappa B activation, ICAM-1 promoter activity, and cell-surface ICAM-1 up regulation. These studies suggest a potential signal transduction pathway from the CD40 receptor to the transcriptional activation of the ICAM-1 gene.

  • localization of the major nf κb activating site and the sole traf3 binding site of lmp 1 defines two distinct signaling motifs
    Journal of Biological Chemistry, 1997
    Co-Authors: Scott R Brodeur, Genhong Cheng, David Baltimore, David A Thorleylawson
    Abstract:

    The TRAF3 molecule interacts with the cytoplasmic carboxyl terminus (COOH terminus) of the Epstein-Barr virus-encoded oncogene LMP-1. NF-κB activation is a downstream signaling event of tumor necrosis factor receptor-associated factor (TRAF) molecules in other signaling systems (CD40 for example) and is an event caused by LMP-1 expression. One region capable of TRAF3 interaction in LMP-1 is the membrane-proximal 45 amino acids (188–242) of the COOH terminus. We show that this region contains the only site for binding of TRAF3 in the 200-amino acid COOH terminus of LMP-1. The site also binds TRAF2 and TRAF5, but not TRAF6. TRAF3 binds to critical residues localized between amino acids 196 and 212 (HHDDSLPHPQQATDDSG), including the PXQX(T/S) motif, that share limited identity to the CD40 receptor TRAF binding site (TAAPVQETL). Mutation of critical residues in the TRAF3 binding site of LMP-1 that prevents binding of TRAF2, TRAF3, and TRAF5 does not affect NF-κB-activating potential. Deletion mapping localized the major NF-κB activating region of LMP-1 to critical residues in the distal 4 amino acids of the COOH terminus (383–386). Therefore, TRAF3 binding and NF-κB activation occur through two separate motifs at opposite ends of the LMP-1 COOH-terminal sequence.

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