Induction of apoptosis and activation of NF-κB by CD95 require different signalling thresholds
TL;DR: It is demonstrated that induction of apoptosis requires two wild‐type alleles of CD95, at the same time allowing induction of survival or proliferative pathways, which could contribute to the increased risk for lymphoma seen in ALPS type Ia patients.
Abstract: Mutations in the death domain of the death receptor CD95 (APO-1/Fas) cause lymphoproliferation and autoimmune disease in both lprcg mice and in patients with autoimmune lymphoproliferative syndrome (ALPS) type Ia. By testing lymphocytes from ALPS type Ia patients, comparing heterozygous with homozygous lprcg mice and coexpressing wild-type and mutant CD95 receptors, we demonstrate that induction of apoptosis requires two wild-type alleles of CD95. By contrast, nuclear factor-κB (NF-κB) can be fully activated in cells expressing both a mutant and a wild-type CD95 allele, suggesting different thresholds to activate the two signalling pathways. This was confirmed by testing lymphocytes from heterozygous lpr mice, which showed reduced sensitivity to CD95-mediated apoptosis but normal activation of NF-κB when compared with wild-type mice. Mutations in CD95 may eliminate the tumour-suppressive function of CD95, at the same time allowing induction of survival or proliferative pathways, which could contribute to the increased risk for lymphoma seen in ALPS type Ia patients.
Citations
More filters
TL;DR: In this paper, a Ca2+-dependent direct interaction between CaM and FLIPL was demonstrated, but not FADD or caspase 8, suggesting a novel role for CaM in Fas signalling.
Abstract: We and others have demonstrated that Fas-mediated apoptosis is a potential therapeutic target for cholangiocarcinoma. Previously, we reported that CaM (calmodulin) antagonists induced apoptosis in cholangiocarcinoma cells through Fas-related mechanisms. Further, we identified a direct interaction between CaM and Fas with recruitment of CaM into the Fas-mediated DISC (death-inducing signalling complex), suggesting a novel role for CaM in Fas signalling. Therefore we characterized the interaction of CaM with proteins recruited into the Fas-mediated DISC, including FADD (Fas-associated death domain)-containing protein, caspase 8 and c-FLIP {cellular FLICE [FADD (Fas-associated death domain)-like interleukin 1β-converting enzyme]-like inhibitory protein}. A Ca2+-dependent direct interaction between CaM and FLIPL, but not FADD or caspase 8, was demonstrated. Furthermore, a 37.3±5.7% increase ( n =6, P =0.001) in CaM–FLIP binding was observed at 30 min after Fas stimulation, which returned to the baseline after 60 min and correlated with a Fas-induced increase in intracellular Ca2+ that reached a peak at 30 min and decreased gradually over 60 min in cholangiocarcinoma cells. A CaM antagonist, TFP (trifluoperazine), inhibited the Fas-induced increase in CaM–FLIP binding concurrent with inhibition of ERK (extracellular-signal-regulated kinase) phosphorylation, a downstream signal of FLIP. Direct binding between CaM and FLIPL was demonstrated using recombinant proteins, and a CaM-binding region was identified in amino acids 197–213 of FLIPL. Compared with overexpression of wild-type FLIPL that resulted in decreased spontaneous as well as Fas-induced apoptosis, mutant FLIPL with deletion of the CaM-binding region resulted in increased spontaneous and Fas-induced apoptosis in cholangiocarcinoma cells. Understanding the biology of CaM–FLIP binding may provide new therapeutic targets for cholangiocarcinoma and possibly other cancers.
Abbreviations: AM, acetoxymethyl ester; CaM, calmodulin; CaMS, CaM–Sepharose; c-FLIP, cellular FLICE-like inhibitory protein; Co-IP, co-immunoprecipitation; CS, control Sepharose; DD, death domain; DED, death effector domain; DISC, death-inducing signalling complex; ERK, extracellular-signal-regulated kinase; FADD, Fas-associated DD; FLICE, FADD-like interleukin 1β-converting enzyme; GST, glutathione transferase; HBSS, Hanks balanced salt solution; HRP, horseradish peroxidase; IPTG, isopropyl β-D-thiogalactoside; TFP, trifluoperazine; TNF, tumour necrosis factor; TNF-R1, TNF receptor 1; TRAIL, TNF-related apoptosis-inducing ligand; TRAIL-R1, TRAIL receptor 1; WT, wild-type
27 citations
TL;DR: It is suggested that factors that inhibit apoptosis confer a growth advantage to the cells beyond the survival advantage of avoiding apoptosis and in effect convert the Fas Ag signaling pathway from a tumor suppressor to a tumor promoter.
Abstract: When cells within the gastric mucosa progress from metaplasia to dysplasia to cancer, they acquire a Fas Ag apoptosis-resistant phenotype. It is unusual to completely abolish the pathway, suggestin...
26 citations
Cites background from "Induction of apoptosis and activati..."
...There is increasing evidence for dual Fas signaling in several different cell systems and the signaling outcome appears to depend on several factors, including the threshold of activation (32) and the interplay of environmental factors....
[...]
...There are several suggested candidates for inducing Fas Agmediated NF- B activation, including the MAPK cascade (32)....
[...]
TL;DR: In this paper, the authors showed that IL-7 up-regulates the splicing regulator polypyrimidine tract binding protein (PTB), leading to inclusion of the transmembrane domain-encoding exon 6 of CD95 mRNA and, subsequently, elevation of CD 95 on memory CD4(+) T cells.
22 citations
TL;DR: An optimal distance between CD95Ligand molecules is identified that enables specific clustering of receptor-ligand pairs, leading to efficient CD95 activation, and sheds light into the regulatory mechanism of CD95activation that can be further explored for anti-cancer therapies.
21 citations
TL;DR: The present results suggest that the etiology of ALP syndromes could be related not only to defects in apoptosis induction, but also in cell cycle regulation.
Abstract: The Fas-FasL pathway plays an important role in the homeostasis of mature lymphocytes, with defects causing autoimmune lymphoproliferative syndromes (ALPS). Human T-cell blasts are not sensitive to FasL or Apo2L/TRAIL-induced apoptosis unless they get reactivated, but either of those ligands inhibits their growth in the absence of cell death induction due to a cell cycle arrest in S-G2/M. In the present work, we have studied the mechanism(s) by which FasL or Apo2L/TRAIL regulate T-cell blast cell cycle in healthy donors and in two types of ALPS patients. Our data indicate that in human CD8+ T-cell blasts, Fas ligation, and especially Apo2L/TRAIL induce the p53-dependent decrease in cyclin-B1 levels. However, the induction of the negative cell cycle regulator p21WAF1 by FasL or Apo2L/TRAIL in either CD4+ or CD8+ T-cell blasts seems to be the main regulatory mechanism. This mechanism is dependent on caspase activation and on H2O2 generation. The increase in p21 levels by FasL or Apo2L/TRAIL is concomitant with p53 increases only in CD8+ T-cell blasts, with p21 levels maintained high for longer times than p53 levels. In CD4+ T-cell blasts p21 levels are controlled through a transient and p53-independent mechanism. The present results suggest that the etiology of ALP syndromes could be related not only to defects in apoptosis induction, but also in cell cycle regulation.
21 citations
Cites background from "Induction of apoptosis and activati..."
...Another possibility would be that in heterozygous ALPS-Ia patients in which apoptotic Fas signaling is abolished, this alternative signal transduction pathway was maintained, such as it has been described for the activation of NF- B [46], while the homozygous mutation in FasL observed in the ALPS-Ic patient would completely abolish all signal transduction due to Fas ligation....
[...]
References
More filters
TL;DR: The occurrence of Fas mutations together with abnormal T cell apoptosis in ALPS patients suggests an involvement of Fas in this recently recognized disorder of lymphocyte homeostasis and peripheral self-tolerance.
1,472 citations
"Induction of apoptosis and activati..." refers background in this paper
...Mutations in the DD have been shown to abrogate induction of apoptosis (Fisher et al, 1995)....
[...]
01 Jan 1995
TL;DR: Fas expression and function were analyzed in three children with a lymphoproliferative syndrome and may provide a molecular basis for some autoimmune diseases in humans.
Abstract: Fas (also known as Apo1 and CD95) is a cell surface receptor involved in apoptotic cell death. Fas expression and function were analyzed in three children (including two siblings) with a lymphoproliferative syndrome, two of whom also had autoimmune disorders. A large deletion in the gene encoding Fas and no detectable cell surface expression characterized the most affected patient. Clinical manifestations in the two related patients were less severe: Fas-mediated apoptosis was impaired and a deletion within the intracytoplasmic domain was detected. These findings illustrate the crucial regulatory role of Fas and may provide a molecular basis for some autoimmune diseases in humans.
1,194 citations
"Induction of apoptosis and activati..." refers background in this paper
...Mutations in the DD of CD95 are naturally found both in mice (lprcg mice; Kimura & Matsuzawa, 1994) and in many patients suffering from autoimmune lymphoproliferative syndrome (ALPS) type Ia (Rieux-Laucat et al, 1995, 1999; Drappa et al, 1996; Martin et al, 1999; Straus et al, 2001)....
[...]
TL;DR: Fas expression and function were analyzed in three children (including two siblings) with a lymphoproliferative syndrome, two of whom also had autoimmune disorders as discussed by the authors, showing that a large deletion in the gene encoding Fas and no detectable cell surface expression characterized the most affected patient.
Abstract: Fas (also known as Apo1 and CD95) is a cell surface receptor involved in apoptotic cell death. Fas expression and function were analyzed in three children (including two siblings) with a lymphoproliferative syndrome, two of whom also had autoimmune disorders. A large deletion in the gene encoding Fas and no detectable cell surface expression characterized the most affected patient. Clinical manifestations in the two related patients were less severe: Fas-mediated apoptosis was impaired and a deletion within the intracytoplasmic domain was detected. These findings illustrate the crucial regulatory role of Fas and may provide a molecular basis for some autoimmune diseases in humans.
1,193 citations
TL;DR: A number of proteins have been reported to regulate formation or activity of the DISC, the complex of proteins that forms upon triggering of CD95 that is essential for induction of apoptosis.
Abstract: CD95 (APO-1/Fas) is a prototype death receptor characterized by the presence of an 80 amino acid death domain in its cytoplasmic tail. This domain is essential for the recruitment of a number of signaling components upon activation by either agonistic anti-CD95 antibodies or cognate CD95 ligand that initiate apoptosis. The complex of proteins that forms upon triggering of CD95 is called the death-inducting signaling complex (DISC). The DISC consists of an adaptor protein and initiator caspases and is essential for induction of apoptosis. A number of proteins have been reported to regulate formation or activity of the DISC. This review discusses recent developments in this area of death receptor research.
1,096 citations
"Induction of apoptosis and activati..." refers background in this paper
...On binding of CD95 ligand (CD95L), CD95 recruits the adaptor protein FADD, the initiator caspases 8 and 10 and the apoptosis regulator c-FLIP, forming the death-inducing signalling complex (DISC; Peter & Krammer, 2003)....
[...]
TL;DR: Results show that formation of preassociated receptor complexes is necessary for Fas signaling and dominant interference in human disease.
Abstract: Heterozygous mutations encoding abnormal forms of the death receptor Fas dominantly interfere with Fas-induced lymphocyte apoptosis in human autoimmune lymphoproliferative syndrome. This effect, rather than depending on ligand-induced receptor oligomerization, was found to stem from ligand- independent interaction of wild-type and mutant Fas receptors through a specific region in the extracellular domain. Preassociated Fas complexes were found in living cells by means of fluorescence resonance energy transfer between variants of green fluorescent protein. These results show that formation of preassociated receptor complexes is necessary for Fas signaling and dominant interference in human disease.
693 citations
"Induction of apoptosis and activati..." refers background in this paper
...&2004 EUROPEAN MOLECULAR BIOLOGY ORGANIZATION EMBO reports VOL 5 | NO 11 | 2004 scientificreport 1085 wild-type receptors (Siegel et al, 2000)....
[...]