Differential Inhibition of TRAIL-Mediated DR5-DISC Formation by Decoy Receptors 1 and 2

Abstract

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF family that induces cancer cell death by apoptosis with some selectivity. TRAIL-induced apoptosis is mediated by the transmembrane receptors death receptor 4 (DR4) (also known as TRAIL-R1) and DR5 (TRAIL-R2). TRAIL can also bind decoy receptor 1 (DcR1) (TRAIL-R3) and DcR2 (TRAIL-R4) that fail to induce apoptosis since they lack and have a truncated cytoplasmic death domain, respectively. In addition, DcR1 and DcR2 inhibit DR4-and DR5-mediated, TRAIL-induced apoptosis and we demonstrate here that this occurs through distinct mechanisms. While DcR1 prevents the assembly of the death-inducing signaling complex (DISC) by titrating TRAIL within lipid rafts, DcR2 is corecruited with DR5 within the DISC, where it inhibits initiator caspase activation. In addition, DcR2 prevents DR4 recruitment within the DR5 DISC. The specificity of DcR1-and DcR2-mediated TRAIL inhibition reveals an additional level of complexity for the regulation of TRAIL signaling.Apoptosis is one of the death phenotypes that can be triggered in tumor cells by anticancer agents. Resistance of tumor cells to apoptosis can account for treatment failure (18). One of the stimuli that can induce tumor cell death by apoptosis is the member of the tumor necrosis factor superfamily known as TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) (16). TRAIL has gained considerable interest in oncology since it displays specific antitumoral activity against a wide range of tumor cells (14, 41, 47) without significant side effects, at least in mice and monkeys (3,21,22).TRAIL triggers apoptosis upon engagement of one of its two agonistic receptors, named DR4 (death receptor 4) (33) and DR5 (death receptor 5) (7,46). In response to TRAIL, these receptors recruit the adaptor protein FADD (Fas-associated death domain), through death domain homophilic interactions (5), and the initiators procaspase-8 and -10, through death effector domain interactions with FADD, hence forming the macromolecular complex called DISC (death-inducing signaling complex). Within this complex, procaspase-8 and -10 are activated by autoproteolytic cleavage and initiate the caspase cascade leading to apoptosis (42).

An anthraquinone derivative, emodin sensitizes hepatocellular carcinoma cells to TRAIL induced apoptosis through the induction of death receptors and downregulation of cell survival proteins

“…While DcR1 prevents the assembly of the death-inducing signaling complex (DISC) by titrating TRAIL within lipid rafts, DcR2 is co-recruited with DR5 within the DISC, where it inhibits initiator caspase activation [44]. We further observed that emodin reduced the expression of DcR2 which makes the availability of ligand for DR4 and DR5 for induction of apoptosis, without affecting the expression level of DcR1 in HCC cells.…”

Enforced covalent trimerization increases the activity of the TNF ligand family members TRAIL and CD95L

“…18 The TNC trimerization domain was chosen due to its small size of about only 30 aa. 18 Anti-Flag affinity-purified TNC-Flag-mTRAIL(99-291) and Flag-TNC-mCD95L(137-279) migrated both in nonreducing SDS-PAGE analysis as trimers and showed in gel filtration analysis a comparable elution volume than the 20 ml of the various M2 agarose purified proteins were fractionated by gel filtration using a BioSep-SEC-S2000 (300 Â 7.8) column (all CD95L variants, Flag-hTRAIL, Flag-TNC-hTRAIL) or a BioSep-SEC-S2000 (300 Â 7.8) column (Flag-mTRAIL and Flag-TNC-mTRAIL). The columns were calibrated with thyroglobulin (669 kDa), apoferritin (443 kDa), b-amylase (200 kDa), serum albumin (66 kDa), carbonic anhydrase (29 kDa) and cytochrome c (12.4 kDa).…”

“…Furthermore, in the human system TRAILR1 and TRAILR2, which are differentially dependent on ligand cross-linking for activation, are also differentially regulated by TRAILR4. 19,20 Second, the transformation of receptor occupancy by ligand into DISC formation and further to activation of apoptotic caspases could be non-linear and receptor-specific. Taken together, fusion with the TNC domain did not overcome the requirement of hCD95L and hTRAIL for secondary cross-linking to become properly active ( Figure 7c and d).…”

Modulation of tumor necrosis factor related apoptosis-inducing ligand (TRAIL) receptors in a human osteoclast model in vitro

“…In fact, they have also interfered with DISC formation in overexpression systems, going further than simple competitive binding to prevent apoptotic TRAIL signaling. In this study, TRAIL-R4 was co-recruited to TRAIL-R2, inhibiting DISC formation and subsequent caspase-8 activation (Merino et al, 2006). However, these mechanisms have as yet only been observed in the aforementioned over-expression conditions, and remain to be confirmed in a true physiological setting.…”