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The Journal of Immunology, 1999, 162: 6307-6311.
Copyright © 1999 by The American Association of Immunologists

CUTTING EDGE

Cutting Edge: Contrasting Roles of TNF Receptor-Associated Factor 2 (TRAF2) and TRAF3 in CD40-Activated B Lymphocyte Differentiation1

Bruce S. Hostager* and Gail A. Bishop2,*,{dagger},{ddagger}

Departments of * Microbiology and {dagger} Internal Medicine, University of Iowa, and {ddagger} VA Medical Center, Iowa City, IA 52242


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results and Discussion
 References
 
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.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results and Discussion
 References
 
Engagement of CD40 by its ligand on activated T cells initiates signals in B lymphocytes that contribute to the activation of cell proliferation, differentiation, isotype switching, enhanced Ag presentation, and other events necessary for an efficient humoral immune response (1). The CD40 signal transduction pathway is only partially characterized but appears to involve several members of the TNF receptor-associated factor (TRAF)3 family of proteins. TRAF2, -3, -5, and -6 all potentially interact with CD40 (2, 3, 4, 5), but their roles in CD40 signaling are unclear. TRAF2 (2) and TRAF6 (5) can induce the activation of NF-{kappa}B when transiently overexpressed in the transformed human kidney cell line 293. In B cell lines, however, mutant CD40 molecules that cannot bind TRAF2 remain able to activate NF-{kappa}B (6). In addition, lymphocytes from mice expressing a "dominant-negative" TRAF2 (DNTRAF2) transgene do not display defects in CD40- or TNF receptor-induced NF-{kappa}B activation (7), and fibroblast cell lines isolated from TRAF2-deficient mouse embryos (8) exhibit only slight delays in TNF-induced NF-{kappa}B activation. However, lymphocytes from DNTRAF2-transgenic mice and TRAF2-deficient fibroblasts do display defects in the activation of c-Jun NH2-terminal kinase mediated by TNFR family members.

The contribution of TRAF3 to CD40 signaling is more enigmatic. Mice deficient in TRAF3 die shortly after birth (9). However, B cells from these mice appear to up-regulate CD23 and proliferate normally in response to CD40 engagement. Fetal liver cells from TRAF3-deficient mice have been used to reconstitute the immune systems of irradiated wild-type mice. Immune responses in the reconstituted mice appear grossly normal, although there is a defect in isotype switching in response to T-dependent Ags. Experiments with TRAF3 in epithelial cell lines suggest that TRAF3 can inhibit CD40-mediated NF-{kappa}B activation (2, 10).

Although transiently transfected epithelial cell lines have been useful in the preliminary characterization of the TRAF proteins, functional studies have been limited to examining the effects of TRAF (or DNTRAF) overproduction on proximal signaling events, such as NF-{kappa}B activation. To examine the roles of TRAFs in hemopoietic cells, and specifically their roles in B lymphocyte effector functions, we have used inducible expression vectors to stably transfect mouse B cell lines with wild-type and mutant TRAF molecules. We find that the binding of TRAF2 or TRAF3 is unnecessary for the ability of CD40 to activate Ab secretion. However, both TRAF molecules can strongly modulate this CD40-mediated effector function, and they appear to exert their effects at separate steps in the activation process.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results and Discussion
 References
 
DNA constructs

pEFLacR is a modification of p3'SS (Stratagene, La Jolla, CA) in which we replaced the F9-1 promoter with the EF-1{alpha} promoter from pEF-BOS (11), to achieve higher levels of Lac repressor (LacR) expression. Human TRAF3 cDNA was prepared from the RAJI B cell line and amplified by PCR using primers containing additional sequence coding for a carboxyl-terminal HA peptide tag. A similarly tagged mouse TRAF3 was prepared from M12.4.1 cDNA. The human TRAF3 construct was used to prepare DNTRAF3 (amino acids 298–568), similar to a mutant molecule previously reported (12). cDNA constructs coding for mouse and human TRAF2 were prepared from M12.4.1 and Ramos cells, respectively. Both TRAF2 constructs contained NH2-terminal FLAG epitope tags. FLAG-tagged mouse DNTRAF2 (2) was provided by Dr. Vishva Dixit (University of Michigan, Ann Arbor, MI). All TRAF cDNA constructs used in stable transfections were subcloned into the inducible expression vector pOPRSVI (Stratagene). cDNA constructs used in 293T transient expression assays were subcloned into the pRSV.5(neo) or pRSV.5(hyg) expression vectors (13). Human CD40 constructs were previously reported (14), and for some transfections they were subcloned into an expression vector coding for zeomycin resistance (Invitrogen, Carlsbad, CA).

Cell lines

The mouse B cell line CH12.LX has been described (15). CH12.LacR cell lines were produced by stably transfecting CH12.LX cells with p3'SS or pEFLacR. Spodoptera frugiperda (Sf9) cells expressing mCD40L were prepared as previously described (14). The human kidney cell line 293T (16) was a gift of Dr. Vishva Dixit. Human Ramos B cells were from the American Type Culture Collection (ATCC, Manassas, VA).

Transfections

Stable transfections of mouse B cell lines were conducted using electroporation as described (14). Transient transfection of 293T cells was accomplished using a calcium phosphate-based method (17).

Immunoprecipitations and Western blotting

Transfected 293T cells were removed from plates with 5 mM EDTA in serum-free DMEM. Cells were suspended in buffer (5.4 mM KCl, 137 mM NaCl, 4.2 mM NaHCO3, pH 8.1) and surface-biotinylated with sulfo-NHS-biotin (Pierce Chemical, Rockford, IL). Cells were washed once in complete culture medium and then resuspended in low salt lysis buffer (1% Triton X-100, 20 mM Tris (pH 8.0), 137 mM NaCl, with protease and phosphatase inhibitors) and incubated for 30 min on ice. Cleared supernatants were incubated for 2 h at 4°C (on rotator) with protein G-agarose beads (Sigma Chemical, St. Louis, MO) preconjugated with anti-hCD40 mAb. Beads were washed four times with modified lysis buffer containing 400 mM NaCl and then once with low salt lysis buffer. Immunoprecipitation from B cell lysates was performed essentially as above, except that cell lysates were prepared by resuspending 5 x 106 cells in 500 µl low salt lysis buffer and incubating for 15 min at 37°C. Immunoprecipitated proteins were separated by SDS-PAGE and then electroblotted onto nitrocellulose membranes. A chemiluminescent substrate (Pierce) was used to detect HRP-labeled Abs and streptavidin-HRP (Sigma) on Western blots.

Ab secretion assays

Ab secretion assays were performed as described (18), except that cells were preincubated for 24 h in 96-well flat bottom plates with 100 µM isopropyl ß-D-thiogalactopyranoside (IPTG) to induce production of TRAF proteins (150 µl and 1500 cells/well). Stimuli were then added (in a volume of 50 µl), and the cells were incubated for an additional 48 h. A 0.1% suspension of sheep RBC was used as Ag, anti-mCD40 Ab was used at a final concentration of 1 µg/ml, anti-hCD40 at 5 µg/ml, LPS (Escherichia coli serotype 055:B5, Sigma) at 50 µg/ml, and CD40L cells were used at a ratio of 1 CD40L-expressing Sf9 cell/4 B cells. CH12.LX cells produce IgM specific for phosphatidylcholine, an Ag on the surface of sheep RBC allowing detection of Ab-secreting cells by their ability to form lytic plaques on a lawn of RBC in the presence of complement. Results are presented as the ratio of plaque-forming cells to viable cells recovered from each culture.

Abs

mAb to mouse CD40 (clone 1C10, rat IgG2a) (19) was kindly provided by Dr. Frances Lund, The Trudeau Institute, Saranac Lake, NY. MOPC-21 (mouse IgG1) was from Sigma. Ab to human CD40 (clone G28-5, ATCC) was purified from cell culture supernatants. Polyclonal goat anti-rabbit Ab conjugated to HRP was from Bio-Rad (Hercules, CA). Polyclonal rabbit Abs to TRAF2 and TRAF3 were from Santa Cruz Biotechnology (Santa Cruz, CA). Anti-HA mAb was from Berkeley Antibody (Richmond, CA), and anti-FLAG mAb was from Sigma.


   Results and Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
References
 
CD40-TRAF2/3 binding is not required for the induction of Ab secretion

Stimulation of the mouse B cell line CH12.LX with anti-CD40 Abs or CD40L results in the induction of Ab secretion as measured by the increased frequency of differentiated, Ab-forming cells (20). We previously utilized CH12.LX to characterize regions of the cytoplasmic domain of CD40 important for signaling (14). A mutant CD40 molecule containing a threonine to alanine substitution at position 234 (CD40A234) was fully able to activate differentiation/Ab secretion, although this mutant is reported to have no TRAF3-binding activity (3). This suggests that TRAF3 binding is not required for CD40-mediated Ab secretion. The observation that TRAF2 and TRAF3 appear to bind the same site on CD40 (21, 22) predicts that CD40A234 lacks TRAF2 binding activity as well. To confirm that CD40A234 fails to bind TRAF2 and TRAF3, 293T cells were transiently transfected with TRAF2 or TRAF3 and wild-type hCD40 or hCD40A234. CD40 immunoprecipitates from cell lysates were tested for coprecipitation of the TRAFs. As a negative control, we used a CD40 molecule truncated by 32 amino acids (hCD40{Delta}32), which lacks the PXQXT minimal TRAF-binding motif (21, 22, 23) (Fig. 1GoA). We also tested a CD40 molecule truncated by 22 amino acids (hCD40{Delta}22), the functional activity of which is very similar to that of hCD40A234 (14), suggesting that it may also fail to bind TRAF2 and TRAF3. Like hCD40A234, hCD40{Delta}22 cannot induce up-regulation of B7–1 but can stimulate Ab secretion. Although this molecule retains the minimal TRAF binding motif, it appears that amino acid residues adjacent to this sequence may also effect TRAF binding (23). Fig. 1Go shows that both TRAFs coprecipitated with full-length CD40, and to a very limited extent with hCD40A234 (seen on long exposures, not shown). The TRAFs did not coprecipitate with hCD40{Delta}32 or hCD40{Delta}22. Together, the data in Fig. 1Go and our previous functional experiments (14) indicate that CD40 can activate Ab secretion in CH12.LX cells in the absence of TRAF2 or TRAF3 binding.



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  		FIGURE 1. TRAF2 and TRAF3 do not bind truncated hCD40. A, Cytoplasmic domains of hCD40 molecules. 293T cells were transiently transfected with human TRAF2 (B) or human TRAF3 (C) and hCD40, hCD40{Delta}32, hCD40{Delta}22, or hCD40A234. hCD40 immunoprecipitations were conducted as in Materials and Methods. Western blots of preimmunoprecipitation lysates demonstrate similar TRAF production in each of the transfected cultures. Reprobing the blots with streptavidin-HRP demonstrated that similar amounts of CD40 were in each lane. Similar results were obtained in two other experiments and also using mouse TRAF2 (not shown).

 
Effects of Inducible TRAF2 and TRAF3 on CD40-activated Ab secretion

Although not absolutely required for CD40-induced Ab secretion, TRAF2 and TRAF3 may still regulate this effector function. To test this hypothesis, we examined the effects of inducible TRAF2 and TRAF3 expression on CD40-activated Ab secretion. CH12.LX cells were first stably transfected with a plasmid coding for LacR protein, generating the cell line CH12.Lac. CH12.Lac cells were then transfected with plasmids encoding TRAF constructs behind a promoter containing LacR-binding sites. TRAF expression was therefore inducible with IPTG (a LacR inactivator) (Fig. 2Go). Thus, cells could be transfected with cDNA constructs coding for proteins that might interfere with cell growth, and the effects of high (induced) and low (basal) TRAF expression could be compared in the same transfectant.



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  		FIGURE 2. Inducible expression of TRAF2 and TRAF3 in transfected CH12.Lac cells. Cells were incubated with or without 100 µM IPTG for 48 h. Epitope-tagged TRAF proteins were immunoprecipitated from cell lysates using anti-FLAG mAb (TRAF2) or anti-HA (TRAF3). TRAF molecules (TRAF2 (T2) ~56kDa, DNTRAF2 (DNT2) ~47 kDa, TRAF3 (T3) ~63 kDa, DNTRAF3 (DNT3) ~19 kDa) were detected on Western blots with rabbit polyclonal antisera.

 
In the absence of IPTG, CH12.Lac cells transfected with an inducible human TRAF3 construct (CH12.T3 cells) differentiated into Ab-secreting cells in response to CD40 ligand (Fig. 3GoA). However, IPTG-induced overexpression of TRAF3 in CH12.T3 almost completely abrogated CD40-stimulated differentiation. IPTG did not inhibit CD40-stimulated differentiation of CH12.Lac. Induced overexpression of a mouse TRAF3 construct had the same effect (data not shown). Although B cell Ag receptor (BCR) signaling alone cannot activate Ab secretion by CH12.LX cells, CD40-mediated Ab secretion can be significantly enhanced by BCR costimulation (20). However, even this costimulation could not overcome the inhibitory activity of inducible TRAF3 (Fig. 3GoA). In spite of the dramatic inhibitory effects of TRAF3, its induction had no detectable effects on cell viability. Also, the results of the Ab secretion assays were normalized to the number of viable cells recovered following stimulation. In contrast to the effects of TRAF3, inducible mouse TRAF2 increased the frequency of Ab-secreting cells in CD40-stimulated cultures (Fig. 3GoB).



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  		FIGURE 3. Induced expression of TRAF3 inhibits, and TRAF2 augments, CD40-mediated Ab secretion. A, CH12.Lac and CH12.T3 cells, ± IPTG were stimulated with CD40L and Ag as described in Materials and Methods. The number of plaque-forming cells (PFC) per thousand viable cells recovered is indicated. Results are the mean ± SE of replicate samples. Similar results were obtained in two additional experiments, in one of which different clones were tested. B, CH12.T2 cells were stimulated with CD40L as in Materials and Methods. Similar results were obtained in two additional experiments, and three additional experiments with a second CH12.T2 clone.

 
To test the specificity of the effects of induced TRAF2 and TRAF3, we examined their effects on LPS-stimulated Ab secretion. LPS is a potent activator of Ab secretion in freshly isolated B cells and CH12.LX (15). The effects of TRAF3 overexpression were specific for CD40 signaling, as inducible TRAF3 did not affect LPS-stimulated Ab secretion (Fig. 4GoA). The coengagement of class II MHC and BCR can also activate Ab secretion in CH12.LX cells (15), but this stimulus was also unaffected by TRAF3 overexpression (not shown). Interestingly, overexpression of TRAF2 augmented Ab secretion stimulated by LPS (Fig. 4GoB) and consistently increased the basal frequency of Ab secreting cells by ~2-fold, whereas the induced expression of TRAF3 did not appear to alter basal differentiation.



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  		FIGURE 4. Effects of inducible TRAF and DNTRAF molecules on Ab secretion stimulated by anti-CD40 or LPS. Induction of TRAF3 (A), TRAF2 (B), DNTRAF2 (C), or DNTRAF3 (D), and stimuli were as in Materials and Methods. Similar results were obtained in a second experiment for each molecule.

 
Effects of DNTRAF molecules on CD40-activated Ab secretion

Various DNTRAF molecules appear to interfere with CD40 signaling (2, 12, 24). These molecules lack portions of the NH2-terminal zinc ring or zinc finger domains, yet retain the ability to bind CD40. On the basis of the results of our experiments with wild-type TRAF2 and TRAF3, we predicted that DNTRAF2 would inhibit and DNTRAF3 would augment CD40-activated Ab secretion. Indeed, induced expression of DNTRAF2 significantly inhibited Ab secretion stimulated by either LPS or anti-CD40 mAb (Fig. 4GoC). DNTRAF2 also consistently inhibited basal (unstimulated) Ab secretion by ~50%.

Because inducible TRAF3 inhibited CD40-mediated Ab secretion, it seemed possible that DNTRAF3 would augment Ab secretion by interfering with the activity of endogenous TRAF3. However, the expression of DNTRAF3 was also inhibitory (Fig. 4GoD), suggesting that the physical association of TRAF3 with CD40 mediates its negative regulatory function, possibly by altering the stoichiometry of CD40-associated proteins. The effects of DNTRAF3 were specific for CD40 signaling, given that LPS-stimulated Ab secretion was unaffected.

Effects of inducible TRAFs on hCD40{Delta}22-activated Ab secretion

Because LPS-stimulated Ab secretion can be modified by inducible TRAF2, it is possible that the TRAFs may also exert their effects without binding CD40. To test this, CH12.T2, CH12.DNT2 and CH12.T3 were transfected with wild-type hCD40 or hCD40{Delta}22 (expression confirmed by flow cytometry, not shown) and were tested in Ab secretion assays. Mouse and human CD40 have highly homologous cytoplasmic domains and have indistinguishable function in mouse B cell lines (6, 14). Species-specific mAbs allow stimulation of cells through either the transfected hCD40, or the endogenous mCD40 as a control. Inducible TRAF3 and DNTRAF2 inhibited the activation of Ab secretion mediated by either hCD40 or mCD40 (Fig. 5Go, A and C). However, Ab secretion stimulated by CD40{Delta}22 was not affected by inducible TRAF3 (Fig. 5GoA). Thus, an intact TRAF2/3-binding site on CD40 is required for TRAF3 to regulate Ab secretion. Interestingly, inducible TRAF2 was able to enhance (and DNTRAF2 inhibited) basal Ab secretion as well as secretion mediated by either hCD40 or hCD40{Delta}22 (Fig. 5Go, B and C). These observations indicate that overexpression of TRAF2 may bypass early steps in CD40 signaling or augment signaling through other cell surface receptors that utilize TRAF2, such as the TNF receptors (25), and CD27 (26). We are currently examining potential contributions of these receptors to the activation of Ab secretion in CH12.LX cells.



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  		FIGURE 5. Effects of inducible TRAF2 and TRAF3 on Ab secretion stimulated by truncated CD40. CH12.T3 (A), CH12.T2 (B), and CH12.DNT2 (C) were stably transfected with either full-length hCD40 or hCD40{Delta}22. IPTG and anti-CD40 mAbs were added as in Materials and Methods. Similar results were obtained in two additional CH12.T3 experiments, a second CH12.T2 experiment, and a second CH12.DNT2 experiment.

 
Although TRAF2 and TRAF3 share a binding site on CD40, competition for this site may not explain the ability of TRAF3 to inhibit signaling. Clearly, CD40{Delta}22 remains able to stimulate Ab secretion even though it cannot bind TRAF2. Alternatively, we suggest that TRAF3 may interfere with the binding of other signaling proteins to CD40 or may serve to recruit inhibitory molecules. Potentially, TRAF3 disrupts interactions of CD40 with TRAF6, the binding site of which on CD40 lies between the membrane and the TRAF2/3 site, and the role of which in Ab secretion remains to be tested.

With notable exceptions (7, 9, 24, 27, 28), much of the functional characterization of TRAF2 and TRAF3 has been conducted in transiently transfected epithelial cell lines. We demonstrate that inducible vector systems can be used to stably transfect lymphocyte cell lines with TRAF cDNA constructs, facilitating the examination of the roles of TRAFs in lymphocyte effector functions. Our results demonstrate that the roles played by TRAF molecules in CD40-stimulated Ab secretion are complex, potentially contributing to both positive and negative regulation, and suggest the potential for the cellular regulation of CD40 signaling through modulation of TRAF expression.


   Acknowledgments
 
We thank Luis Ramirez for technical assistance and Dr. John Harty for critical review of the manuscript.


   Footnotes
 
1 This work was supported by an Arthritis Foundation Postdoctoral Fellowship awarded to B.S.H., grants to G.A.B. from the National Institutes of Health (AI28847, CA66570), and the Veterans Administration (Merit Review 383). Core support was provided by National Institutes of Health Grant DK25295 to the University of Iowa Diabetes and Endocrinology Research Center. Back

2 Address correspondence and reprint requests to Dr. Gail A. Bishop, University of Iowa, Department of Microbiology, 3–570 BSB, Iowa City, IA 52242. E-mail address: Back

3 Abbreviations used in this paper: DN, dominant-negative; LacR, lac repressor protein; TRAF, TNF receptor-associated factor; BCR, B cell Ag receptor; IPTG, isopropyl ß-D-thiogalactopyranoside. Back

Received for publication February 26, 1999. Accepted for publication March 29, 1999.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
 References
 

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R. M. Andrade, M. Wessendarp, J.-A. C. Portillo, J.-Q. Yang, F. J. Gomez, J. E. Durbin, G. A. Bishop, and C. S. Subauste
TNF Receptor-Associated Factor 6-Dependent CD40 Signaling Primes Macrophages to Acquire Antimicrobial Activity in Response to TNF-{alpha}
J. Immunol., November 1, 2005; 175(9): 6014 - 6021.
[Abstract] [Full Text] [PDF]

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 J. Biol. Chem.Home page
S. Wu, P. Xie, K. Welsh, C. Li, C.-Z. Ni, X. Zhu, J. C. Reed, A. C. Satterthwait, G. A. Bishop, and K. R. Ely
LMP1 Protein from the Epstein-Barr Virus Is a Structural CD40 Decoy in B Lymphocytes for Binding to TRAF3
J. Biol. Chem., September 30, 2005; 280(39): 33620 - 33626.
[Abstract] [Full Text] [PDF]

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 J. Immunol.Home page
C. R. Moore and G. A. Bishop
Differential Regulation of CD40-Mediated TNF Receptor-Associated Factor Degradation in B Lymphocytes
J. Immunol., September 15, 2005; 175(6): 3780 - 3789.
[Abstract] [Full Text] [PDF]

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 Proc. Natl. Acad. Sci. USAHome page
J. Hauer, S. Puschner, P. Ramakrishnan, U. Simon, M. Bongers, C. Federle, and H. Engelmann
TNF receptor (TNFR)-associated factor (TRAF) 3 serves as an inhibitor of TRAF2/5-mediated activation of the noncanonical NF-{kappa}B pathway by TRAF-binding TNFRs
PNAS, February 22, 2005; 102(8): 2874 - 2879.
[Abstract] [Full Text] [PDF]

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 J. Biol. Chem.Home page
M. E. Munroe and G. A. Bishop
Role of Tumor Necrosis Factor (TNF) Receptor-associated Factor 2 (TRAF2) in Distinct and Overlapping CD40 and TNF Receptor 2/CD120b-mediated B Lymphocyte Activation
J. Biol. Chem., December 17, 2004; 279(51): 53222 - 53231.
[Abstract] [Full Text] [PDF]

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 JEMHome page
P. Xie, B. S. Hostager, and G. A. Bishop
Requirement for TRAF3 in Signaling by LMP1 But Not CD40 in B Lymphocytes
J. Exp. Med., March 1, 2004; 199(5): 661 - 671.
[Abstract] [Full Text] [PDF]

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 J. Biol. Chem.Home page
S. A. Haxhinasto and G. A. Bishop
Synergistic B Cell Activation by CD40 and the B Cell Antigen Receptor: ROLE OF B LYMPHOCYTE ANTIGEN RECEPTOR-MEDIATED KINASE ACTIVATION AND TUMOR NECROSIS FACTOR RECEPTOR-ASSOCIATED FACTOR REGULATION
J. Biol. Chem., January 23, 2004; 279(4): 2575 - 2582.
[Abstract] [Full Text] [PDF]

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A. Clatza, L. C. Bonifaz, D. A. A. Vignali, and J. Moreno
CD40-Induced Aggregation of MHC Class II and CD80 on the Cell Surface Leads to an Early Enhancement in Antigen Presentation
J. Immunol., December 15, 2003; 171(12): 6478 - 6487.
[Abstract] [Full Text] [PDF]

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 J. Biol. Chem.Home page
B. S. Hostager, S. A. Haxhinasto, S. L. Rowland, and G. A. Bishop
Tumor Necrosis Factor Receptor-associated Factor 2 (TRAF2)-deficient B Lymphocytes Reveal Novel Roles for TRAF2 in CD40 Signaling
J. Biol. Chem., November 14, 2003; 278(46): 45382 - 45390.
[Abstract] [Full Text] [PDF]

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 J. Biol. Chem.Home page
L.-F. Lu, W. J. Cook, L.-L. Lin, and R. J. Noelle
CD40 Signaling through a Newly Identified Tumor Necrosis Factor Receptor-associated Factor 2 (TRAF2) Binding Site
J. Biol. Chem., November 14, 2003; 278(46): 45414 - 45418.
[Abstract] [Full Text] [PDF]

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S. A. Haxhinasto and G. A. Bishop
A Novel Interaction between Protein Kinase D and TNF Receptor-Associated Factor Molecules Regulates B Cell Receptor-CD40 Synergy
J. Immunol., November 1, 2003; 171(9): 4655 - 4662.
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Z. SM. Rahman, S. P. Rao, S. L. Kalled, and T. Manser
Normal Induction but Attenuated Progression of Germinal Center Responses in BAFF and BAFF-R Signaling-Deficient Mice
J. Exp. Med., October 20, 2003; 198(8): 1157 - 1169.
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 GutHome page
C M Gelbmann, S N Leeb, D Vogl, M Maendel, H Herfarth, J Scholmerich, W Falk, and G Rogler
Inducible CD40 expression mediates NF{kappa}B activation and cytokine secretion in human colonic fibroblasts
Gut, October 1, 2003; 52(10): 1448 - 1456.
[Abstract] [Full Text] [PDF]

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S. M. Propst, K. Estell, and L. M. Schwiebert
CD40-mediated Activation of NF-kappa B in Airway Epithelial Cells
J. Biol. Chem., September 27, 2002; 277(40): 37054 - 37063.
[Abstract] [Full Text] [PDF]

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 J. Immunol.Home page
S. A. Haxhinasto, B. S. Hostager, and G. A. Bishop
Cutting Edge: Molecular Mechanisms of Synergy Between CD40 and the B Cell Antigen Receptor: Role for TNF Receptor-Associated Factor 2 in Receptor Interaction
J. Immunol., August 1, 2002; 169(3): 1145 - 1149.
[Abstract] [Full Text] [PDF]

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 Proc. Natl. Acad. Sci. USAHome page
Y. Qian, Z. Zhao, Z. Jiang, and X. Li
Role of NFkappa B activator Act1 in CD40-mediated signaling in epithelial cells
PNAS, July 9, 2002; 99(14): 9386 - 9391.
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 J. Leukoc. Biol.Home page
G. A. Bishop, B. S. Hostager, and K. D. Brown
Mechanisms of TNF receptor-associated factor (TRAF) regulation in B lymphocytes
J. Leukoc. Biol., July 1, 2002; 72(1): 19 - 23.
[Abstract] [Full Text] [PDF]

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 J. Biol. Chem.Home page
K. D. Brown, B. S. Hostager, and G. A. Bishop
Regulation of TRAF2 Signaling by Self-induced Degradation
J. Biol. Chem., May 24, 2002; 277(22): 19433 - 19438.
[Abstract] [Full Text] [PDF]

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 J. Immunol.Home page
B. S. Hostager and G. A. Bishop
Role of TNF Receptor-Associated Factor 2 in the Activation of IgM Secretion by CD40 and CD120b
J. Immunol., April 1, 2002; 168(7): 3318 - 3322.
[Abstract] [Full Text] [PDF]

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 J. Immunol.Home page
L. K. Busch and G. A. Bishop
Multiple Carboxyl-Terminal Regions of the EBV Oncoprotein, Latent Membrane Protein 1, Cooperatively Regulate Signaling to B Lymphocytes Via TNF Receptor-Associated Factor (TRAF)-Dependent and TRAF-Independent Mechanisms
J. Immunol., November 15, 2001; 167(10): 5805 - 5813.
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 JEMHome page
K. D. Brown, B. S. Hostager, and G. A. Bishop
Differential Signaling and Tumor Necrosis Factor Receptor-associated Factor (TRAF) Degradation Mediated by CD40 and the Epstein-Barr Virus Oncoprotein Latent Membrane Protein 1 (LMP1)
J. Exp. Med., April 16, 2001; 193(8): 943 - 954.
[Abstract] [Full Text] [PDF]

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 J. Leukoc. Biol.Home page
Z. H. Lee, S. E. Lee, K. Kwack, W. Yeo, T. H. Lee, S. S. Bae, P.-G. Suh, and H.-H. Kim
Caspase-mediated cleavage of TRAF3 in FasL-stimulated Jurkat-T cells
J. Leukoc. Biol., March 1, 2001; 69(3): 490 - 496.
[Abstract] [Full Text]

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 J. Immunol.Home page
G. A. Bishop, Y. Hsing, B. S. Hostager, S. V. Jalukar, L. M. Ramirez, and M. A. Tomai
Molecular Mechanisms of B Lymphocyte Activation by the Immune Response Modifier R-848
J. Immunol., November 15, 2000; 165(10): 5552 - 5557.
[Abstract] [Full Text] [PDF]

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 Proc. Natl. Acad. Sci. USAHome page
C.-Z. Ni, K. Welsh, E. Leo, C.-k. Chiou, H. Wu, J. C. Reed, and K. R. Ely
Molecular basis for CD40 signaling mediated by TRAF3
PNAS, September 12, 2000; 97(19): 10395 - 10399.
[Abstract] [Full Text] [PDF]

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A. Cerutti, A. Schaffer, R. G. Goodwin, S. Shah, H. Zan, S. Ely, and P. Casali
Engagement of CD153 (CD30 Ligand) by CD30+ T Cells Inhibits Class Switch DNA Recombination and Antibody Production in Human IgD+ IgM+ B Cells
J. Immunol., July 15, 2000; 165(2): 786 - 794.
[Abstract] [Full Text] [PDF]

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A. Bhushan, B. Barnhart, S. Shone, C. Song, and L. R. Covey
A Transcriptional Defect Underlies B Lymphocyte Dysfunction in a Patient Diagnosed with Non-X-Linked Hyper-IgM Syndrome
J. Immunol., March 15, 2000; 164(6): 2871 - 2880.
[Abstract] [Full Text] [PDF]

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 J. Immunol.Home page
S. V. Jalukar, B. S. Hostager, and G. A. Bishop
Characterization of the Roles of TNF Receptor-Associated Factor 6 in CD40-Mediated B Lymphocyte Effector Functions
J. Immunol., January 15, 2000; 164(2): 623 - 630.
[Abstract] [Full Text] [PDF]

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