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.
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TL;DR: This analysis has uncovered that the stochasticity in apoptosis and NF-kB pathways leads not only to survival or death of a cell, but also causes a third type of response to CD95 stimulation that is termed ambivalent response.
Abstract: CD95/Fas/APO-1 is a member of the death receptor family that triggers apoptotic and anti-apoptotic responses in particular, NF-κB. These responses are characterized by a strong heterogeneity within a population of cells. To determine how the cell decides between life and death we developed a computational model supported by imaging flow cytometry analysis of CD95 signaling. Here we show that CD95 stimulation leads to the induction of caspase and NF-κB pathways simultaneously in one cell. The related life/death decision strictly depends on cell-to-cell variability in the formation of the death-inducing complex (DISC) on one side (extrinsic noise) vs. stochastic gene expression of the NF-κB pathway on the other side (intrinsic noise). Moreover, our analysis has uncovered that the stochasticity in apoptosis and NF-kB pathways leads not only to survival or death of a cell, but also causes a third type of response to CD95 stimulation that we termed ambivalent response. Cells in the ambivalent state can undergo cell death or survive which was subsequently validated by experiments. Taken together, we have uncovered how these two competing pathways control the fate of a cell, which in turn plays an important role for development of anti-cancer therapies.
20 citations
TL;DR: Comparison of changes in the transcriptome of pleiotropically competent, early passage L3055 Burkitt’s lymphoma cells confronted with low (picomolar) and high (nanomolars) concentrations of CD154 is compared to gain insight into how a single receptor sets these distinct phenotypes.
Abstract: Activated B cells reacting to small amounts of CD40L (CD154) maintain homeostasis by suppressing default apoptosis. Additional outcomes, particularly differentiation, demand higher CD40 occupancy. Here, focusing on survival, we compared changes in the transcriptome of pleiotropically competent, early passage L3055 Burkitt’s lymphoma cells confronted with low (picomolar) and high (nanomolar) concentrations of CD154 to gain insight into how a single receptor sets these distinct phenotypes. Of 267 genes altering transcriptional activity in response to strong CD154 tone, only 25 changed coordinately on low receptor occupancy. Seven of the top nine common up-regulated genes were targets of NF-κB. Direct measurement and functional inhibition of the NF-κB pathway revealed it to be central to a CD40-dependent survival signature. Although the canonical NF-κB axis was engaged by both signaling strengths equally, robust alternative pathway activation was a feature selective to a strong CD40 signal. Discriminatory exploitation of the two separate arms of NF-κB activation may indicate a principle whereby a cell senses and reacts differentially to shifting ligand availability. Identifying components selectively coupling CD40 to each axis could indicate targets for disruption in B cell pathologies underpinned by ectopic and/or hyper-CD154 activity such as neoplasia and some autoimmunities.
18 citations
Cites background from "Induction of apoptosis and activati..."
...The level of CD95 available for engagement can similarly set subsequent signaling and functional consequences: a reduced complement of receptor, as occurs in a subset of patients with autoimmune lymphoproliferative syndrome, resulting in efficient (canonical) NF- B activation but not apoptosis whereas normal levels signal both (34)....
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TL;DR: It is concluded that locking CD95 in apoptosis-mode may be a more promising anti-cancer strategy than simply inhibiting or stimulating CD95.
17 citations
Cites background from "Induction of apoptosis and activati..."
...For instance, survival signaling by CD95 requires far lower thresholds of receptor stimulation than those required to induce apoptosis [69,72]....
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Journal Article•
TL;DR: This Review focuses on the regulation of CD95 signaling and provides brief analysis of molecular switches of its pro- and antiapoptotic functions.
Abstract: CD95, also called Fas or APO-1, was the first death receptor (DR) identified and characterized. Studies on CD95 receptor signaling revealed the versatile principles of cell fate regulation via DR. DRs could exert both pro- and anti-apoptotic effects depending on clustering, internalization or signaling thresholds and other extracellular signals. It became clear that molecular network regulating cell death and survival is under the multilevel control. In this Review we focus on the regulation of CD95 signaling and provide brief analysis of molecular switches of its pro- and antiapoptotic functions. At least five levels of life-death cell regulation via CD95 could be tracked: extracellular, membrane, DISC, mitochondrial, and miRNA. The cellular outcome of signaling via DRs depends on other extracellular signals and availability of different intracellular components of signal transduction pathways. This article is part of a Special Issue entitled "Apoptosis: Four Decades Later".
17 citations
TL;DR: Results suggest a model in which functional polymorphisms at the three genes collaborate on the global ability of the Fas/FasL system to induce apoptosis, and report new polymorphisms in the coding sequence of Fadd.
Abstract: In previous reports, we described germ line functional polymorphisms that differentiate Fas and FasL genes in two mouse strains (SEG/Pas and C57BL/6J) exhibiting extreme differences in susceptibility to γ radiation-induced T-cell lymphomas. Here, we provide new data reinforcing the importance of the extrinsic pathway of apoptosis mediated by Fas in T-cell lymphoma development and about the functional significance of polymorphisms located at intracellular and extracellular domains of Fas and FasL. Using DNA recombinant technology, we generate chimerical Fas and FasL proteins by combination of protein regions derived from the two strains and demonstrate that any Fas-FasL interaction involving chimerical proteins drive cell apoptosis to a significant lower extent than the wild-type SEG/Pas and C57BL/6J Fas-FasL systems. In addition, we report new polymorphisms in the coding sequence of Fadd and demonstrate that the interaction between Fas and Fadd is significantly stronger if Fas and Fadd are of SEG/Pas origin compared with the C57BL/6J system. Altogether, these results suggest a model in which functional polymorphisms at the three genes collaborate on the global ability of the Fas/FasL system to induce apoptosis. A complete analysis of these three genes in the pathway appears to be a sine qua non condition to accurately predict the effectiveness of the Fas system and to estimate susceptibility to T-cell lymphoma.
16 citations
References
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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)....
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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)....
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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)....
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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)....
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