TACI is a TRAF-interacting receptor for TALL-1, a tumor necrosis factor family member involved in B cell regulation - PubMed (original) (raw)

. 2000 Jul 3;192(1):137-43.

doi: 10.1084/jem.192.1.137.

J Treanor, G Senaldi, S D Khare, T Boone, M Kelley, L E Theill, A Colombero, I Solovyev, F Lee, S McCabe, R Elliott, K Miner, N Hawkins, J Guo, M Stolina, G Yu, J Wang, J Delaney, S Y Meng, W J Boyle, H Hsu

Affiliations

TACI is a TRAF-interacting receptor for TALL-1, a tumor necrosis factor family member involved in B cell regulation

X Z Xia et al. J Exp Med. 2000.

Abstract

We and others recently reported tumor necrosis factor (TNF) and apoptosis ligand-related leukocyte-expressed ligand 1 (TALL-1) as a novel member of the TNF ligand family that is functionally involved in B cell proliferation. Transgenic mice overexpressing TALL-1 have severe B cell hyperplasia and lupus-like autoimmune disease. Here, we describe expression cloning of a cell surface receptor for TALL-1 from a human Burkitt's lymphoma RAJI cell library. The cloned receptor is identical to the previously reported TNF receptor (TNFR) homologue transmembrane activator and calcium modulator and cyclophilin ligand (CAML) interactor (TACI). Murine TACI was subsequently isolated from the mouse B lymphoma A20 cells. Human and murine TACI share 54% identity overall. Human TACI exhibits high binding affinities to both human and murine TALL-1. Soluble TACI extracellular domain protein specifically blocks TALL-1-mediated B cell proliferation without affecting CD40- or lipopolysaccharide-mediated B cell proliferation in vitro. In addition, when injected into mice, soluble TACI inhibits antibody production to both T cell-dependent and -independent antigens. By yeast two-hybrid screening of a B cell library with TACI intracellular domain, we identified that, like many other TNFR family members, TACI intracellular domain interacts with TNFR-associated factor (TRAF)2, 5, and 6. Correspondingly, TACI activation in a B cell line results in nuclear factor kappaB and c-Jun NH(2)-terminal kinase activation. The identification and characterization of the receptor for TALL-1 provides useful information for the development of a treatment for B cell-mediated autoimmune diseases such as systemic lupus erythematosus.

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Figures

Figure 1

Figure 1

TACI is the cell surface receptor for TALL-1. (A) Comparison of human and murine TACI. The amino acid sequences of human and murine TACI are aligned. Transmembrane regions are underlined. (B) FACS® analysis of TALL-1 binding to TACI-transfected 293 cells. 293 cells (3 × 105) were transiently transfected with vector, human TACI, or murine TACI expression vector. After 24 h, cells were first exposed to 1 μg/ml Fc-tagged TALL-1 protein, then stained with FITC-conjugated goat F(ab′)2 anti–human IgG.

Figure 1

Figure 1

TACI is the cell surface receptor for TALL-1. (A) Comparison of human and murine TACI. The amino acid sequences of human and murine TACI are aligned. Transmembrane regions are underlined. (B) FACS® analysis of TALL-1 binding to TACI-transfected 293 cells. 293 cells (3 × 105) were transiently transfected with vector, human TACI, or murine TACI expression vector. After 24 h, cells were first exposed to 1 μg/ml Fc-tagged TALL-1 protein, then stained with FITC-conjugated goat F(ab′)2 anti–human IgG.

Figure 2

Figure 2

Expression of TALL-1 receptor on activated CD4- and CD8-positive T cells. PBMCs from healthy donors were activated using anti-CD3 antibody (1 μg/ml) for the indicated period of time, and cell surface receptors for TALL-1 were examined by flow cytometry using Flag-tagged TALL-1, anti-Flag biotin antibody, and streptavidin-PE reagents (red histogram). Anti-Flag biotin antibody and streptavidin-PE reagents were used as control for each set of experiments (black histogram). CD4- or CD8-positive T cells were gated to analyze expression of TALL-1 receptor on specific cell types. FL2-H represents log fluorescence intensity.

Figure 3

Figure 3

Soluble TACI protein specifically inhibited TALL-1–mediated B cell proliferation. Purified B cells (105) from B6 mice were cultured in triplicates in 96-well plates with the indicated amounts of soluble TACI extracellular domain protein in the presence of 10 ng/ml TALL-1 plus 2 μg/ml anti-IgM antibody (top), 1 μg/ml anti-CD40 antibody plus 2 μg/ml anti-IgM antibody (middle), or 0.5 μg/ml LPS (bottom) for a period of 4 d. Proliferation was measured by radioactive [3H]thymidine uptake in the last 18 h of pulse. Data shown represent mean ± SD of triplicate wells.

Figure 6

Figure 6

Northern blot analysis of TACI and BCMA. (A) FACS® analysis of TALL-1 binding to TACI- and BCMA-transfected 293 cells. 293 cells (3 × 105) were transiently transfected with vector, human TACI, or human BCMA expression vector. After 24 h, cells were first exposed to 1 μg/ml Fc-tagged TALL-1 protein, then stained with FITC-conjugated goat F(ab′)2 anti–human IgG. (B) Northern blot analysis of TACI and BCMA. Full-length coding regions of human and mouse TACI (top) or BCMA (bottom) were generated by PCR and used as probe in the Northern blot analysis of poly A+ RNA from A20 cells or multiple-tissue Northern blot (CLONTECH Laboratories, Inc.). The blots were exposed to Biomax film (Eastman Kodak Co.) at −80°C for 2 d.

Figure 6

Figure 6

Northern blot analysis of TACI and BCMA. (A) FACS® analysis of TALL-1 binding to TACI- and BCMA-transfected 293 cells. 293 cells (3 × 105) were transiently transfected with vector, human TACI, or human BCMA expression vector. After 24 h, cells were first exposed to 1 μg/ml Fc-tagged TALL-1 protein, then stained with FITC-conjugated goat F(ab′)2 anti–human IgG. (B) Northern blot analysis of TACI and BCMA. Full-length coding regions of human and mouse TACI (top) or BCMA (bottom) were generated by PCR and used as probe in the Northern blot analysis of poly A+ RNA from A20 cells or multiple-tissue Northern blot (CLONTECH Laboratories, Inc.). The blots were exposed to Biomax film (Eastman Kodak Co.) at −80°C for 2 d.

Figure 4

Figure 4

Soluble TACI-Fc fusion protein inhibits anti-KLH and anti-Pneumovax antibody production. Mice (n = 7) were treated with 5 mg/kg TACI-Fc fusion protein or nonfused Fc protein each day for 7 d. Serum levels of anti-KLH IgG and IgM and anti-Pneumovax were measured on day 7 by ELISA.

Figure 5

Figure 5

TACI interacts with TRAF proteins and induces NF-κB and JNK activation. (A) Mapping of TACI TRAF-binding domains. Expression vectors encoding full-length or deletion mutants of TACI intracellular domain fused to the GAL4 DNA–binding domain were cotransformed into the HF7C yeast strain with vectors expressing the GAL4 activation fused with TRAF2, 5, and 6. Plus signs represent growth after 1 wk on the selection plates. (B) Coimmunoprecipitation of TACI with TRAF and CAML proteins. 293 cells (3 × 105) were cotransfected with expression vectors directing synthesis of NH2-terminal Flag-tagged wild-type (wt) TACI or TACI deletion mutants along with myc-tagged CAML, TRAF2, TRAF5, and TRAF6 expression vectors. After 24 h, cell lysates were immunoprecipitated with monoclonal antibody against myc epitope. Coprecipitated Flag-tagged TACI mutants, as indicated by arrows, were detected by immunoblot analysis with anti-Flag monoclonal antibody. For each transfection sample, TACI wild-type or mutants were not detected when mouse IgG was used for the immunoprecipitation (data not shown). (C) NF-κB activation induced by TALL-1. Approximately 107 A20 cells were left untreated or were treated with 100 ng/ml TALL-1 for 2 h. Nuclear extracts were prepared, incubated with the 32P-labeled NF-κB oligonucleotide probe, and subjected to electrophoretic mobility shift analysis. (D) JNK activation induced by TALL-1. Approximately 106 A20 cells were exposed to 100 ng/ml TALL-1 for the indicated length of time. The cell lysates were immunoprecipitated with monoclonal anti-JNK antibody. Immunoprecipitates were assayed for kinase activity by using GST-JUN as substrate.

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