The Transmembrane Domains of TNF-Related Apoptosis-Inducing Ligand (TRAIL) Receptors 1 and 2 Co-Regulate Apoptotic Signaling Capacity

Abstract

TNF-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor (TNF) ligand family that exerts its apoptotic activity in human cells by binding to two transmembrane receptors, TRAILR1 and TRAILR2. In cells co-expressing both receptors the particular contribution of either protein to the overall cellular response is not well defined. Here we have investigated whether differences in the signaling capacities of TRAILR1 and TRAILR2 can be attributed to certain functional molecular subdomains. We generated and characterized various chimeric receptors comprising TRAIL receptor domains fused with parts from other members of the TNF death receptor family. This allowed us to compare the contribution of particular domains of the two TRAIL receptors to the overall apoptotic response and to identify elements that regulate apoptotic signaling. Our results show that the TRAIL receptor death domains are weak apoptosis inducers compared to those of CD95/Fas, because TRAILR-derived constructs containing the CD95/Fas death domain possessed strongly enhanced apoptotic capabilities. Importantly, major differences in the signaling strengths of the two TRAIL receptors were linked to their transmembrane domains in combination with the adjacent extracellular stalk regions. This was evident from receptor chimeras comprising the extracellular part of TNFR1 and the intracellular signaling part of CD95/Fas. Both receptor chimeras showed comparable ligand binding affinities and internalization kinetics. However, the respective TRAILR2-derived molecule more efficiently induced apoptosis. It also activated caspase-8 and caspase-3 more strongly and more quickly, albeit being expressed at lower levels. These results suggest that the transmembrane domains together with their adjacent stalk regions can play a major role in control of death receptor activation thereby contributing to cell type specific differences in TRAILR1 and TRAILR2 signaling.

Membrane Trafficking of Death Receptors: Implications on Signalling

“…The extracellular domain of these receptors contains two complete CRDs, which are important for ligand binding. A recent report suggested a co-regulatory role for the transmembrane domain of TRAIL-R1 and TRAIL-R2 for the apoptotic signalling capacity [67]. The intracellular part of TRAIL-R1 and TRAIL-R2 harbours a full length death domain.…”

MicroRNA‐23a modulates tumor necrosis factor‐alpha‐induced osteoblasts apoptosis by directly targeting fas

“…In contrast, the intrinsic pathway is initiated through the release of signal factors by mitochondria within the cell, which is triggered by many cellular abnormal events [Fulda and Debatin, 2006]. Previous studies showed that TNF-alpha can bind to two different receptors TNFR1 or p55 and TNFR2 or p75 [Kruglov et al, 2008;Neumann et al, 2012]. It has been reported that TNF-alpha binding to TNFR1 is a known activator of pro-apoptotic signals in osteoblasts [Bu et al, 2003].…”

Novel RANKL DE‐loop mutants antagonize RANK‐mediated osteoclastogenesis

“…Furthermore, Neumann et al . showed that the signaling capabilities of the death receptors DR4 and DR5 do not only depend on binding of TRAIL but the transmembrane domains together with their adjacent stalk regions also control the signaling strength. Likewise, the transmembrane domain and adjacent extracellular stalk regions of RANK could play a similar role.…”

“…In a molecular dynamics study on binding between TNF-ligand family member TRAIL and its death receptor DR5, Wassenaar et al [33] proposed that through binding to TRAIL the conformational freedom of extracellular binding domains of DR5 was strongly restricted; this might also influence the stability of the intracellular death complex. Furthermore, Neumann et al [34] showed that the signaling capabilities of the death receptors DR4 and DR5 do not only depend on binding of TRAIL but the transmembrane domains together with their adjacent stalk regions also control the signaling strength. Likewise, the transmembrane domain and adjacent extracellular stalk regions of RANK could play a similar role.…”