Tumor Necrosis Factor (TNF) Receptor Superfamily Member TACI Is a High Affinity Receptor for TNF Family Members APRIL and BLyS

Abstract

We also demonstrate that TACI interacts with nanomolar affinity with the BLyS-related tumor necrosis factor homologue APRIL for which no clear in vivo role has been described. BLyS and APRIL are capable of signaling through TACI to mediate NF-B responses in HEK293 cells. We conclude that TACI is a receptor for BLyS and APRIL and discuss the implications for B-cell biology.Members of the tumor necrosis factor superfamily of cytokines play diverse roles in the regulation of cell proliferation, differentiation, and survival. Notably, several members of this family play key roles in the regulation of the immune system (1). We and others have previously identified a novel TNF 1 -related ligand, BLyS (also known as BAFF, TALL-1, THANK, TNFSF20, and zTNF4) which is expressed on monocytes and induces B-cell proliferation and immunoglobulin secretion in vitro and in vivo (2-6). Like many members of the TNF family, BLyS has activity in vitro as a 152-amino acid soluble molecule and as a 258-amino acid transmembrane form (3). However, the biological significance of these two forms and their relative contributions in vivo remain to be resolved. More recently, transgenic mice that ectopically overexpress BLyS were shown to develop autoimmune-like phenotypes reminiscent of those observed in systemic lupus erythematosus (7-9). These findings suggest that BLyS plays an important role in the regulation of B-cell growth and humoral immunity.In order to understand the precise mechanism by which BLyS activates B-cells, the range of cell types BLyS may affect, and the potential role of BLyS as a therapeutic agent or target, we have used expression cloning to identify the receptor for BLyS. We have identified the orphan receptor TACI (10), previously characterized as being present on B-cells and a subset of T-cells, as the receptor for BLyS and show that this receptor is capable of mediating NF-B signaling in response to ligand binding. We also show that TACI interacts with another TNF family member, APRIL, which is closely related to BLyS. Parallel work by others has recently shown that TACI and a second TNFR family member, BCMA, are BLyS receptors (9, 11-14). EXPERIMENTAL PROCEDURESCell Culture and Media-HEK293T cells were cultured in Dulbecco's modified Eagle's medium (DMEM) containing 10% fetal bovine serum and transfected using LipofectAMINE Plus (Life Technologies, Gaithersburg, MD) according to the manufacturer's protocol. For expression cloning screens, cells were attached to plates with poly-D-lysine.Flow Cytometry-Cells were stained with monoclonal antibodies raised against BLyS at the indicated protein concentrations, with biotinylated BLyS as described previously (2), with recombinant TACI-Fc fusion protein or with recombinant Flag-tagged proteins which were subsequently detected by the M2 anti-Flag monoclonal antibody (Sigma). Flow cytometry was performed using a FACScan instrument and associated CellQuest software (Becton Dickinson, San Jose, CA).Library Preparation, Screening, and Other DNA Manipulations-All common DNA...

The Design and Characterization of Receptor-selective APRIL Variants

“…4 and Tables 1 and 2). WT APRIL bound TACI-and BCMA-Fc, both human and mouse, with affinities comparable with previously published values (Tables 1 and 2) (9,11,12,34). The BCMA-specific mutant R206E bound both human and mouse BCMA with affinities comparable with WT APRIL, whereas its binding to TACI was obviously reduced.…”

APRIL, a new member of the tumor necrosis factor family, modulates death ligand-induced apoptosis

“…There, XIAP expression was regulated by NF-kB. 31 In that regard, the recent observations 24,25 of enhanced NF-kB activity mediated by APRIL when binding to its receptors TACI or BCMA supports the idea that APRIL-mediated NF-kB activation leads to enhanced levels of XIAP in glioma cells. Of note, protection from death ligand-induced apoptosis in LN-18 glioma cells was insignificant ( Figure 3C), and XIAP expression in LN-18 cells ectopically producing APRIL was not enhanced ( Figure 5B).…”

“…24 demonstrated that APRIL binds specifically to TACI and BCMA and thereby activates nuclear factor-kB (NF-kB). Similarly, Wu et al 25 characterized TACI as a receptor for APRIL and reported that TACI mRNA was found predominantly in B cells. In peripheral blood B cells, the interaction of APRIL with its receptors results in enhanced immunglobulin M production.…”

Abnormal production of the TNF-homologue APRIL increases the proliferation of human malignant glioblastoma cell lines via a specific receptor

“…The recently described TNF-homologue, APRIL (a proliferation-inducing ligand) (Hahne et al, 1998), which is also known as TNF-related death ligand (TRDL1-a) (Kelly et al, 2000) and TNFSF13a, binds B-cell maturation (BCMA) (Laˆabi et al, 1992(Laˆabi et al, , 1994Madry et al, 1998), transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) (Shu et al, 1999;Gross et al, 2000;Xia et al, 2000) and a hypothetical but as yet uncharacterized third receptor (APRIL-R) (Rennert et al, 2000). B-cell activating factor belonging to the TNF family (BAFF) (Schneider et al, 1999), another TNF-homologue, also binds BCMA , TACI (Marsters et al, 2000;Wu et al, 2000;Yu et al, 2000), in addition to its own specific receptor, BAFF-R (Thompson et al, 2001). APRIL is produced in small amounts in peripheral blood lymphocytes (PBLs) and normal tissue but is produced in much larger quantities in malignant tumours, in which it stimulates the growth of malignant cells (Hahne et al, 1998).…”