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1.
cIAP1 and cIAP2 facilitate cancer cell survival by functioning as E3 ligases that promote RIP1 ubiquitination 总被引:1,自引:0,他引:1
Bertrand MJ Milutinovic S Dickson KM Ho WC Boudreault A Durkin J Gillard JW Jaquith JB Morris SJ Barker PA 《Molecular cell》2008,30(6):689-700
The inhibitor of apoptosis (IAP) family of proteins enhances cell survival through mechanisms that remain uncertain. In this report, we show that cIAP1 and cIAP2 promote cancer cell survival by functioning as E3 ubiquitin ligases that maintain constitutive ubiquitination of the RIP1 adaptor protein. We demonstrate that AEG40730, a compound modeled on BIR-binding tetrapeptides, binds to cIAP1 and cIAP2, facilitates their autoubiquitination and proteosomal degradation, and causes a dramatic reduction in RIP1 ubiquitination. We show that cIAP1 and cIAP2 directly ubiquitinate RIP1 and induce constitutive RIP1 ubiquitination in cancer cells and demonstrate that constitutively ubiquitinated RIP1 associates with the prosurvival kinase TAK1. When deubiquitinated by AEG40730 treatment, RIP1 binds caspase-8 and induces apoptosis. These findings provide insights into the function of the IAPs and provide new therapeutic opportunities in the treatment of cancer. 相似文献
2.
Chang YF Cheng CM Chang LK Jong YJ Yuo CY 《Biochemical and biophysical research communications》2006,342(4):1022-1026
Human cIAP1 protein is a member of the inhibitor of apoptosis proteins (IAPs) that are involved in apoptosis regulation and an increasing number of other functions, including cell cycle and intracellular signal transduction. In order to identify novel proteins involved in cIAP1 regulation, we performed a yeast two-hybrid screen and identified an F-box protein Fbxo7 as a cIAP1 interacting protein. Co-immunoprecipitation assay showed that cIAP1 can interact with Fbxo7 in human cells. When co-expressed in cells, cIAP1 and Fbxo7 co-localized remarkably both in the cytoplasm and nucleus, and considerable amounts of these often co-localized at one or few distinct Golgi-like structures close to the nucleus. Furthermore, we showed that overexpression of Fbxo7 promotes the ubiquitination of cIAP1. Since F-box proteins are specificity determining subunits of SCF ubiquitin protein ligases, our results suggest that Fbxo7 can mediate the ubiquitination of cIAP1 by SCF ubiquitin protein ligase and thus have important implication in the regulation of cIAP1 function. 相似文献
3.
Signaling complexes formed on tumor necrosis factor receptor 2 (TNF-R2) contain adaptor proteins TNF-R-associated factors (TRAFs) 1 and 2, and cellular inhibitors of apoptosis (cIAPs) 1 and 2 which function as regulators of programmed cell death. TRAF2, cIAP1 and cIAP2 all have RING finger domains known to possess E3 ubiquitin ligase activity, implying that ubiquitination may play an important role in the TNF signaling pathway. In this report, we have shown that cIAP2 specifically mediated ubiquitination and proteasome-dependent degradation of TRAF1. To identify the sites for cIAP2-mediated ubiquitination of TRAF1, we used high pressure liquid chromatography coupled with tandem mass spectrometry. Lys185 and Lys193 of TRAF1 were found to be modified with ubiquitin chains. Mutation of Lys185 and Lys193 to Arg almost completely blocked cIAP2-mediated ubiquitination of TRAF1, indicating that they are the major, if not the only, sites of TRAF1 ubiquitination. Our data suggest that cIAP2 may regulate the turnover of TRAF1 by adding polyubiquitin chains on Lys185 or Lys193 following its recruitment to TNF-R signaling complexes. 相似文献
4.
TNF-alpha induces two distinct caspase-8 activation pathways 总被引:2,自引:0,他引:2
The inflammatory response of mammalian cells to TNF-alpha can be switched to apoptosis either by cotreatment with a protein synthesis inhibitor, cycloheximide, or Smac mimetic, a small molecule mimic of Smac/Diablo protein. Cycloheximide promotes caspase-8 activation by eliminating endogenous caspase-8 inhibitor, c-FLIP, while Smac mimetic does so by triggering autodegradation of cIAP1 and cIAP2 (cIAP1/2), leading to the release of receptor interacting protein kinase (RIPK1) from the activated TNF receptor complex to form a caspase-8-activating complex consisting of RIPK1, FADD, and caspase-8. This process also requires the action of CYLD, a RIPK1 K63 deubiquitinating enzyme. RIPK1 is critical for caspase-8 activation-induced by Smac mimetic but dispensable for that triggered by cycloheximide. Moreover, Smac mimetic-induced caspase-8 activation is not blocked by endogenous c-FLIP. These findings revealed that TNF-alpha is able to induce apoptosis via two distinct caspase-8 activation pathways that are differentially regulated by cIAP1/2 and c-FLIP. 相似文献
5.
IAPs block apoptotic events induced by caspase-8 and cytochrome c by direct inhibition of distinct caspases. 总被引:33,自引:0,他引:33
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Q L Deveraux N Roy H R Stennicke T Van Arsdale Q Zhou S M Srinivasula E S Alnemri G S Salvesen J C Reed 《The EMBO journal》1998,17(8):2215-2223
Inhibitor of apoptosis (IAP) gene products play an evolutionarily conserved role in regulating programmed cell death in diverse species ranging from insects to humans. Human XIAP, cIAP1 and cIAP2 are direct inhibitors of at least two members of the caspase family of cell death proteases: caspase-3 and caspase-7. Here we compared the mechanism by which IAPs interfere with activation of caspase-3 and other effector caspases in cytosolic extracts where caspase activation was initiated by caspase-8, a proximal protease activated by ligation of TNF-family receptors, or by cytochrome c, which is released from mitochondria into the cytosol during apoptosis. These studies demonstrate that XIAP, cIAP1 and cIAP2 can prevent the proteolytic processing of pro-caspases -3, -6 and -7 by blocking the cytochrome c-induced activation of pro-caspase-9. In contrast, these IAP family proteins did not prevent caspase-8-induced proteolytic activation of pro-caspase-3; however, they subsequently inhibited active caspase-3 directly, thus blocking downstream apoptotic events such as further activation of caspases. These findings demonstrate that IAPs can suppress different apoptotic pathways by inhibiting distinct caspases and identify pro-caspase-9 as a new target for IAP-mediated inhibition of apoptosis. 相似文献
6.
Federica Cossu Mario Milani Eloise Mastrangelo Patrice Vachette Daniele Lecis Domenico Delia Vincenzo Rizzo Pierfausto Seneci Carlo Scolastico Martino Bolognesi 《Journal of molecular biology》2009,392(3):630-596
XIAP is an apoptotic regulator protein that binds to the effector caspases -3 and -7 through its BIR2 domain, and to initiator caspase-9 through its BIR3 domain. Molecular docking studies suggested that Smac-DIABLO may antagonize XIAP by concurrently targeting both BIR2 and BIR3 domains; on this basis bivalent Smac-mimetic compounds have been proposed and characterized. Here, we report the X-ray crystal structure of XIAP-BIR3 domain in complex with a two-headed compound (compound 3) with improved efficacy relative to its monomeric form. A small-angle X-ray scattering study of XIAP-BIR2BIR3, together with fluorescence polarization binding assays and compound 3 cytotoxicity tests on HL60 leukemia cell line are also reported. The crystal structure analysis reveals a network of interactions supporting XIAP-BIR3/compound 3 recognition; moreover, analytical gel-filtration chromatography shows that compound 3 forms a 1:1 stoichiometric complex with a XIAP protein construct containing both BIR2 and BIR3 domains. On the basis of the crystal structure and small-angle X-ray scattering, a model of the same BIR2-BIR3 construct bound to compound 3 is proposed, shedding light on the ability of compound 3 to relieve XIAP inhibitory effects on caspase-9 as well as caspases -3 and -7. A molecular modeling/docking analysis of compound 3 bound to cIAP1-BIR3 domain is presented, considering that Smac-mimetics have been shown to kill tumor cells by inducing cIAP1 and cIAP2 ubiquitination and degradation. Taken together, the results reported here provide a rationale for further development of compound 3 as a lead in the design of dimeric Smac mimetics for cancer treatment. 相似文献
7.
X-linked inhibitor of apoptosis functions as ubiquitin ligase toward mature caspase-9 and cytosolic Smac/DIABLO 总被引:12,自引:0,他引:12
Members of the IAP (inhibitor of apoptosis) family function as anti-apoptotic proteins by binding directly to caspase-3, -7, and -9 to inhibit their activities. During apoptosis, the activities of IAPs are relieved by a second mitochondria-derived caspase activator, named Smac/DIABLO. Some IAPs have a C-terminal RING finger domain that has been identified as the essential motif for the activity of ubiquitin ligase (E3). Here we show that X-linked IAP (XIAP) mediates the polyubiquitination of caspase-9 and Smac. The large subunit of mature caspase-9 was polyubiquitinated by XIAP in vitro, while procaspase-9 was not. Furthermore, the polyubiquitinated form of caspase-9 accumulated in an XIAP-dependent manner in intact cells. The ubiquitination of caspase-9 was significantly inhibited in the presence of mature Smac, whereas XIAP was also found to promote the polyubiquitination of cytosolic Smac both in vitro and in intact cells. These ubiquitination reactions require the RING finger domain of XIAP. These findings suggest that XIAP functions as ubiquitin ligase toward mature caspase-9 and Smac to inhibit apoptosis. 相似文献
8.
Stephen P. Burke Lucinda Smith Jeffrey B. Smith 《The Journal of biological chemistry》2010,285(39):30061-30068
Although early studies of inhibitor of apoptosis proteins (IAPs) suggested that cIAP1 directly binds and inhibits caspases similarly to X-linked IAP (XIAP), a recent one found that micromolar concentrations of cIAP1 only weakly inhibit caspase-3, -7, or -9. Here, we show that cIAP1 specifically and cooperatively blocks the cytochrome c-dependent apoptosome in vitro. Hence, cIAP1 prevented the activation of procaspase-3 but had no effect on the processing of procaspase-9 or the activity of prior activated caspase-3. Like cIAP1, XIAP had no effect on procaspase-9 processing and was a more potent inhibitor of procaspase-3 activation than of already activated caspase-3 activity. Inhibition of procaspase-3 activation depended on BIR2 and BIR3 of cIAP1 and was independent of BIR1, RING, CARD, and UBA domains. Smac prevented cIAP1 from inhibiting procaspase-3 activation and reversed the inhibition by prior addition of cIAP1. A procaspase-9 mutant (D315A) that cannot produce the p12 subunit was resistant to inhibition by cIAP1. Therefore, the N-terminal Ala-Thr-Pro-Phe motif of the p12 subunit of the caspase-9 apoptosome facilitates apoptosome blockade. Consequently, cIAP1 cooperatively interacts with oligomerized processed caspase-9 in the apoptosome and blocks procaspase-3 activation. 相似文献
9.
Hosokawa H Kimura MY Shinnakasu R Suzuki A Miki T Koseki H van Lohuizen M Yamashita M Nakayama T 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(11):7656-7664
The Polycomb group (PcG) gene products regulate the maintenance of the homeobox gene expression in Drosophila and vertebrates and also the cell cycle progression in thymocytes and Th2 cell differentiation in mature T cells. We herein studied the role of PcG gene bmi-1 product in Th1/Th2 cell differentiation and found that Bmi-1 facilitates Th2 cell differentiation in a Ring finger-dependent manner. Biochemical studies indicate that Bmi-1 interacts with GATA3 in T cells, which is dependent on the Ring finger of Bmi-1. The overexpression of Bmi-1 resulted in a decreased ubiquitination and an increased protein stability of GATA3. In bmi-1-deficient Th cells, the levels of Th2 cell differentiation decreased as the degradation and ubiquitination on GATA3 increased. Therefore, Bmi-1 plays a crucial role in the control of Th2 cell differentiation in a Ring finger-dependent manner by regulating GATA3 protein stability. 相似文献
10.
11.
Gentle IE Wong WW Evans JM Bankovacki A Cook WD Khan NR Nachbur U Rickard J Anderton H Moulin M Lluis JM Moujalled DM Silke J Vaux DL 《The Journal of biological chemistry》2011,286(15):13282-13291
RIPK1 is involved in signaling from TNF and TLR family receptors. After receptor ligation, RIPK1 not only modulates activation of both canonical and NIK-dependent NF-κB, but also regulates caspase-8 activation and cell death. Although overexpression of RIPK1 can cause caspase-8-dependent cell death, when RIPK1(-/-) cells are exposed to TNF and low doses of cycloheximide, they die more readily than wild-type cells, indicating RIPK1 has pro-survival as well as pro-apoptotic activities. To determine how RIPK1 promotes cell survival, we compared wild-type and RIPK1(-/-) cells treated with TNF. Although TRAF2 levels remained constant in TNF-treated wild-type cells, TNF stimulation of RIPK1(-/-) cells caused TRAF2 and cIAP1 to be rapidly degraded by the proteasome, which led to an increase in NIK levels. This resulted in processing of p100 NF-κB2 to p52, a decrease in levels of cFLIP(L), and activation of caspase-8, culminating in cell death. Therefore, the pro-survival effect of RIPK1 is mediated by stabilization of TRAF2 and cIAP1. 相似文献
12.
The polycomb protein Ring1B generates self atypical mixed ubiquitin chains required for its in vitro histone H2A ligase activity 总被引:1,自引:0,他引:1
Polycomb complexes mediate gene silencing, in part by modifying histones. Ring1B and Bmi1 are RING finger proteins that are members of the Polycomb repressive complex 1 (PRC1). Ring1B is an E3 that mediates its own polyubiquitination and monoubiquitination of histone H2A. In contrast, Bmi1 has no self-ubiquitinating activity. We show that unlike other RING finger proteins that are believed to mediate their own ubiquitination and degradation, Ring1B and Bmi1 are degraded by an exogenous E3, independent of their RING domain. The RING domains of both proteins mediate their association and subsequent stabilization. Consistent with the nonproteolytic self-ligase activity of Ring1B, it generates atypical mixed K6-, K27-, and K48-based polyubiquitin chains, which require the presence of all these lysine residues on the same ubiquitin molecule. The modification is required for Ring1B ability to monoubiquitinate H2A in vitro, unraveling an as yet undescribed mechanism for ligase activation via noncanonical self-ubiquitination. 相似文献
13.
Nguyen LK Muñoz-García J Maccario H Ciechanover A Kolch W Kholodenko BN 《PLoS computational biology》2011,7(12):e1002317
In an active, self-ubiquitinated state, the Ring1B ligase monoubiquitinates histone H2A playing a critical role in Polycomb-mediated gene silencing. Following ubiquitination by external ligases, Ring1B is targeted for proteosomal degradation. Using biochemical data and computational modeling, we show that the Ring1B ligase can exhibit abrupt switches, overshoot transitions and self-perpetuating oscillations between its distinct ubiquitination and activity states. These different Ring1B states display canonical or multiply branched, atypical polyubiquitin chains and involve association with the Polycomb-group protein Bmi1. Bistable switches and oscillations may lead to all-or-none histone H2A monoubiquitination rates and result in discrete periods of gene (in)activity. Switches, overshoots and oscillations in Ring1B catalytic activity and proteosomal degradation are controlled by the abundances of Bmi1 and Ring1B, and the activities and abundances of external ligases and deubiquitinases, such as E6-AP and USP7. 相似文献
14.
Inhibitors of Apoptosis Proteins (IAPs) are evolutionarily well conserved and have been recognized as the key negative regulators of apoptosis. Recently, the role of IAPs as E3 ligases through the Ring domain was revealed. Using proteomic analysis to explore potential target proteins of DIAP1, we identified Drosophila Endonuclease G (dEndoG), which is known as an effector of caspase-independent cell death. In this study, we demonstrate that human EndoG interacts with IAPs, including human cellular Inhibitor of Apoptosis Protein 1 (cIAP1). EndoG was ubiquitinated by IAPs in vitro and in human cell lines. Interestingly, cIAP1 was capable of ubiquitinating EndoG in the presence of wild-type and mutant Ubiquitin, in which all lysines except K63 were mutated to arginine. cIAP1 expression did not change the half-life of EndoG and cIAP1 depletion did not alter its levels. Expression of dEndoG 54310, in which the mitochondrial localization sequence was deleted, led to cell death that could not be suppressed by DIAP1 in S2 cells. Moreover, EndoG-mediated cell death induced by oxidative stress in HeLa cells was not affected by cIAP1. Therefore, these results indicate that IAPs interact and ubiquitinate EndoG via K63-mediated isopeptide linkages without affecting EndoG levels and EndoG-mediated cell death, suggesting that EndoG ubiquitination by IAPs may serve as a regulatory signal independent of proteasomal degradation. 相似文献
15.
Young Eun Choi Michael Butterworth Srinivas Malladi Colin S. Duckett Gerald M. Cohen Shawn B. Bratton 《The Journal of biological chemistry》2009,284(19):12772-12782
Inhibitor of apoptosis (IAP) proteins are widely expressed throughout
nature and suppress cell death under a variety of circumstances. X-linked IAP,
the prototypical IAP in mammals, inhibits apoptosis largely through direct
inhibition of the initiator caspase-9 and the effector caspase-3 and -7. Two
additional IAP family members, cellular IAP1 (cIAP1) and cIAP2, were once
thought to also inhibit caspases, but more recent studies have suggested
otherwise. Here we demonstrate that cIAP1 does not significantly inhibit the
proteolytic activities of effector caspases on fluorogenic or endogenous
substrates. However, cIAP1 does bind to caspase-3 and -7 and does so,
remarkably, at distinct steps prior to or following the removal of their
prodomains, respectively. Indeed, cIAP1 bound to an exposed IAP-binding motif,
AKPD, on the N terminus of the large subunit of fully mature caspase-7,
whereas cIAP1 bound to partially processed caspase-3 in a manner that required
its prodomain and cleavage between its large and small subunits but did not
involve a classical IAP-binding motif. As a ubiquitin-protein isopeptide
ligase, cIAP1 ubiquitinated caspase-3 and -7, concomitant with binding, in a
reaction catalyzed by members of the UbcH5 subfamily (ubiquitin carrier
protein/ubiquitin-conjugating enzymes), and in the case of caspase-3,
differentially by UbcH8. Moreover, wild-type caspase-7 and a chimeric
caspase-3 (bearing the AKPD motif) were degraded in vivo in a
proteasome-dependent manner. Thus, cIAPs likely suppress apoptosis, at least
in part, by facilitating the ubiquitination and turnover of active effector
caspases in cells.Apoptosis is a programmed form of cell death that is generally executed
through the activation of
caspases,2 cysteine
proteases that exhibit an almost absolute preference for cleavage after
aspartate residues. Caspases are synthesized as single-chain zymogens,
containing a prodomain, as well as large and small subunits that include
residues required for substrate recognition and cleavage
(1). During death receptor or
mitochondria-dependent apoptosis, the long prodomain-containing initiator
caspase-8/10 and -9 are recruited via their adapter proteins, Fas-associated
death domain and apoptotic protease-activating factor-1 (Apaf-1), to
multimeric caspase-activating complexes known as the death-inducing signaling
complex and the apoptosome, respectively
(1,
2). In the latter case,
mitochondrial outer membrane permeabilization (MOMP) is required to mediate
the release of cytochrome c from the intermembrane space into the
cytosol, where it stimulates dATP/ATP-dependent oligomerization of Apaf-1 into
the apoptosome (2). Once
recruited, all initiator caspases are concentrated within their respective
complexes and are thought to be activated as a result of dimerization, with
concomitant autocatalytic cleavage of the activation loops that separate their
large and small subunits (1).
However, unlike caspase-8 and -10, caspase-9 must remain bound to the
apoptosome to exhibit significant catalytic activity, so that in addition to
promoting dimerization, the apoptosome may also induce conformational changes
in caspase-9 that are necessary for its activation
(3–6).In contrast to initiator caspases, effector caspases, such as caspase-3 and
-7, contain short prodomains and exist normally as latent dimers, wherein
their activation loops sterically hinder substrate access and hold the
substrate binding pocket in an inactive conformation
(1). Effector caspases are
directly activated by caspase-8, -9, and -10, and following cleavage of
caspase-3 between its large and small subunits, the two-chain p20/p12 form
becomes a catalytically active heterotetramer and undergoes subsequent
autocatalytic processing between its prodomain and large subunits to generate
the fully mature p17/p12 form of the enzyme
(7). Similarly, procaspase-7 is
also activated following cleavage of its activation loop to generate its
two-chain p22/p12 form; however, it remains unclear whether removal of its
prodomain in cells (to generate its p19/p12 form) is accomplished primarily
via autocatalysis, active caspase-3, or perhaps by serine proteases at a
non-aspartate residue (8,
9). Caspase-3 and -7 exhibit
significant sequence and structural homology, differing primarily in their
short prodomains. Despite this fact, caspase-3 processes a wider array of
protein substrates during apoptosis and is largely responsible for dismantling
the cell (10). Thus,
interesting questions remain regarding the physiological roles of caspase-7,
whether caspase-7 activity is differentially regulated compared with
caspase-3, and what structural features determine (and in some cases limit)
its substrate specificity.Given the devastating consequences of unfettered caspase activation, cells
have evolved mechanisms to regulate caspase activity. For example, IAPs,
originally identified in baculoviruses, possess one or more baculovirus IAP
repeat (BIR) domains, and at least one of the eight family members, XIAP,
selectively inhibits the activities of caspase-9, -3, and -7
(1,
11). Mechanistically, the BIR3
domain in XIAP binds to an exposed IBM on the N terminus of the small subunit
of processed caspase-9, situated directly above the active site, and limits
the access of substrates (12,
13). By contrast, the linker
region (located between the BIR1 and BIR2 domains in XIAP) lies across the
active sites of caspase-3 and -7 and binds in a reverse orientation to
substrates, thereby preventing cleavage of the linker while simultaneously
preventing the access of substrates
(14,
15). The BIR2 domain then
stabilizes the linker-caspase-3 (and linker-caspase-7) interactions further by
binding to an exposed IBM on the N terminus of the small subunit in the
adjacent caspase dimer (14,
16). Importantly, IAP
antagonists, such as Smac/DIABLO and Omi/HtrA2, are normally sequestered to
the intermembrane space of mitochondria and are released (along with
cytochrome c) into the cytoplasm during apoptosis. As IAP antagonists
also possess IBMs, they bind to BIR domains and prevent or relieve the
inhibition of caspases by IAPs
(1).Previously, two additional IAP family members, cIAP1 and cIAP2, were also
thought to inhibit caspases, but more recent studies suggest that these IAPs
bind but do not inhibit caspases
(17–19).
Nevertheless, various studies have shown that cIAPs can protect cells from
apoptosis, are overexpressed or mutated in some cancers, and can promote
tumorigenesis
(20–25),
raising questions as to how these IAPs inhibit cell death or whether they have
additional functions (26).
XIAP, cIAP1, and cIAP2 possess C-terminal RING zinc finger domains with E3
ubiquitin (Ub) ligase activities capable of catalyzing the ubiquitination and
subsequent proteasomal degradation of cellular targets, including themselves
(27,
28). Moreover, cIAPs have been
shown to ubiquitinate several factors, including TNF receptor-associated
factor 2, the serine/threonine kinase NIK, receptor-interacting protein 1, and
the IAP antagonist Smac
(29–34).
However, although there is some evidence to support a direct role for
ubiquitination in the regulation of effector caspases by XIAP
(35,
36), the role of cIAPs in this
process remains unclear, particularly in vivo. We demonstrate herein
that cIAP1 binds to caspase-3 and -7 at unique steps in their processing,
prior to or following the removal of their prodomains, respectively. Moreover,
rather than directly inhibiting these effector caspases, cIAP1 ubiquitinates
them and targets them for proteasome-dependent degradation, thereby
suppressing apoptosis. 相似文献
16.
MCF-7 cells lack caspase-3 but undergo mitochondrial-dependent apoptosis via caspase-7 activation. It is assumed that the Apaf-1-caspase-9 apoptosome processes caspase-7 in an analogous manner to that described for caspase-3. However, this has not been validated experimentally, and we have now characterized the caspase-7 activating apoptosome complex in MCF-7 cell lysates activated with dATP/cytochrome c. Apaf-1 oligomerizes to produce approximately 1.4-MDa and approximately 700-kDa apoptosome complexes, and the latter complex directly cleaves/activates procaspase-7. This approximately 700-kDa apoptosome complex, which is also formed in apoptotic MCF-7 cells, is assembled by rapid oligomerization of Apaf-1 and followed by a slower process of procaspase-9 recruitment and cleavage to form the p35/34 forms. However, procaspase-9 recruitment and processing are accelerated in lysates supplemented with caspase-3. In lysates containing very low levels of Smac and Omi/HtrA2, XIAP (X-linked inhibitor of apoptosis) binds tightly to caspase-9 in the apoptosome complex, and as a result caspase-7 processing is abrogated. In contrast, in MCF-7 lysates containing Smac and Omi/HtrA2, active caspase-7 is released from the apoptosome and forms a stable approximately 200-kDa XIAP-caspase-7 complex, which apparently does not contain cIAP1 or cIAP2. Thus, in comparison to caspase-3-containing cells, XIAP appears to have a more significant antiapoptotic role in MCF-7 cells because it directly inhibits caspase-7 activation by the apoptosome and also forms a stable approximately 200-kDa complex with active caspase-7. 相似文献
17.
Arrigoni R Alam SL Wamstad JA Bardwell VJ Sundquist WI Schreiber-Agus N 《FEBS letters》2006,580(26):6233-6241
18.
cIAP1/2 are direct E3 ligases conjugating diverse types of ubiquitin chains to receptor interacting proteins kinases 1 to 4 (RIP1-4) 总被引:1,自引:0,他引:1
Bertrand MJ Lippens S Staes A Gilbert B Roelandt R De Medts J Gevaert K Declercq W Vandenabeele P 《PloS one》2011,6(9):e22356
The RIP kinases have emerged as essential mediators of cellular stress that integrate both extracellular stimuli emanating from various cell-surface receptors and signals coming from intracellular pattern recognition receptors. The molecular mechanisms regulating the ability of the RIP proteins to transduce the stress signals remain poorly understood, but seem to rely only partially on their kinase activities. Recent studies on RIP1 and RIP2 have highlighted the importance of ubiquitination as a key process regulating their capacity to activate downstream signaling pathways. In this study, we found that XIAP, cIAP1 and cIAP2 not only directly bind to RIP1 and RIP2 but also to RIP3 and RIP4. We show that cIAP1 and cIAP2 are direct E3 ubiquitin ligases for all four RIP proteins and that cIAP1 is capable of conjugating the RIPs with diverse types of ubiquitin chains, including linear chains. Consistently, we show that repressing cIAP1/2 levels affects the activation of NF-κB that is dependent on RIP1, -2, -3 and -4. Finally, we identified Lys51 and Lys145 of RIP4 as two critical residues for cIAP1-mediated ubiquitination and NF-κB activation. 相似文献
19.
Jang JH 《FEBS letters》2004,578(1-2):21-25
We have previously shown that fibroblast growth factor receptor 2 (FGFR2) plays an important role in gastric carcinogenesis. In this study, we have used a differential display approach to identify basic fibroblast growth factor (bFGF)-inducible genes in gastric cancer cells. Here, we report that one of these genes is predicted to encode a RING finger protein, designated FIGC. The FIGC gene was found to encode a polypeptide of 381 amino acids with a novel RING finger module at the NH2-terminus and the COOH-terminal proline-rich region. Using an in vitro ubiquitination assay with recombinant protein, we demonstrate that FIGC has intrinsic E3 ubiquitin ligase activity and promotes ubiquitination. Our data indicate that FIGC upregulation in response to bFGF in gastric cancer might be implicated in carcinogenesis through dysregulation of growth modulator. 相似文献
20.
The Ripoptosome, a signaling platform that assembles in response to genotoxic stress and loss of IAPs 总被引:2,自引:0,他引:2
Tenev T Bianchi K Darding M Broemer M Langlais C Wallberg F Zachariou A Lopez J MacFarlane M Cain K Meier P 《Molecular cell》2011,43(3):432-448
A better understanding of the mechanisms through which anticancer drugs exert their effects is essential to improve combination therapies. While studying how genotoxic stress kills cancer cells, we discovered a large ~2MDa cell death-inducing platform, referred to as "Ripoptosome." It contains the core components RIP1, FADD, and caspase-8, and assembles in response to genotoxic stress-induced depletion of XIAP, cIAP1 and cIAP2. Importantly, it forms independently of TNF, CD95L/FASL, TRAIL, death-receptors, and mitochondrial pathways. It also forms upon Smac-mimetic (SM) treatment without involvement of autocrine TNF. Ripoptosome assembly requires RIP1's kinase activity and can stimulate caspase-8-mediated apoptosis as well as caspase-independent necrosis. It is negatively regulated by FLIP, cIAP1, cIAP2, and XIAP. Mechanistically, IAPs target components of this complex for ubiquitylation and inactivation. Moreover, we find that etoposide-stimulated Ripoptosome formation converts proinflammatory cytokines into prodeath signals. Together, our observations shed new light on fundamental mechanisms by which chemotherapeutics may kill cancer cells. 相似文献