Enhances BCL10-induced activation of NF-kappa-B. Involved in nuclear export of BCL10. Binds to TRAF6, inducing TRAF6 oligomerization and activation of its ligase activity. Has ubiquitin ligase activity. MALT1-dependent BCL10 cleavage plays an important role in T-cell antigen receptor-induced integrin adhesion.
At least two distinct recurrent chromosomal translocations have been implicated in the pathogenesis of MALT lymphoma. The first, t(1;14), results in the transfer of the entire Bcl10 gene to chromosome 14 wherein Bcl10 expression is inappropriately stimulated by the neighboring Ig enhancer. The second, t(11;18), results in the synthesis of a novel fusion protein, API2-MALT1. Until now, no common mechanism of action has been proposed to explain how the products of these seemingly unrelated translocations may contribute to the same malignant process. We show here that Bcl10 and MALT1 form a strong and specific complex within the cell, and that these proteins synergize in the activation of NF-kappaB. The data support a mechanism of action whereby Bcl10 mediates the oligomerization and activation of the MALT1 caspase-like domain. This subsequently activates the IKK complex through an unknown mechanism, setting in motion a cascade of events leading to NF-kappaB induction. Furthermore, the API2-MALT1 fusion protein also strongly activates NF-kappaB and shows dependence upon the same downstream signaling factors. We propose a model whereby both the Bcl10.MALT1 complex and the API2-MALT1 fusion protein activate a common downstream signaling pathway that originates with the oligomerization-dependent activation of the MALT1 caspase-like domain.
The NF-kappaB family of transcription factors is activated in response to many stimuli, including pro-inflammatory cytokines, environmental stresses and, in the case of B and T lymphocytes, by antigenic stimulation. Bcl10 is essential for NF-kappaB activation by T- and B-cell receptors. T and B lymphocytes from Bcl10-deficient mice fail to activate NF-kappaB in response to antigen-receptor stimulation and, as a consequence, are unable to proliferate. Bcl10 overexpression is sufficient to activate NF-kappaB, a process that requires the NF-kappaB essential modulator NEMO (also known as IKK-gamma), which is the regulatory subunit of the IkappaB kinase complex. However, the cellular mechanism by which Bcl10 activates the NF-kappaB pathway remains unclear. Here we show that Bcl10 targets NEMO for lysine-63-linked ubiquitination. Notably, a mutant form of NEMO that cannot be ubiquitinated inhibited Bcl10-induced NF-kappaB activation. Paracaspase and a ubiquitin-conjugating enzyme (UBC13) were both required for Bcl10-induced NEMO ubiquitination and subsequent NF-kappaB activation. Furthermore, short interfering RNAs that reduced the expression of paracaspase and UBC13 abrogated the effects of Bcl10. Thus, the adaptor protein Bcl10 promotes activation of NF-kappaB transcription factors through paracaspase- and UBC13-dependent ubiquitination of NEMO.
The paracaspase MALT1 is pivotal in antigen receptor-mediated lymphocyte activation and lymphomagenesis. MALT1 contains a caspase-like domain, but it is unknown whether this domain is proteolytically active. Here we report that MALT1 had arginine-directed proteolytic activity that was activated after T cell stimulation, and we identify the signaling protein Bcl-10 as a MALT1 substrate. Processing of Bcl-10 after Arg228 was required for T cell receptor-induced cell adhesion to fibronectin. In contrast, MALT1 activity but not Bcl-10 cleavage was essential for optimal activation of transcription factor NF-kappaB and production of interleukin 2. Thus, the proteolytic activity of MALT1 is central to T cell activation, which suggests a possible target for the development of immunomodulatory or anticancer drugs.
Catalysis of the hydrolysis of internal, alpha-peptide bonds in a polypeptide chain by a mechanism in which the sulfhydryl group of a cysteine residue at the active center acts as a nucleophile.
Caspases are cysteine proteases essential to apoptosis. We have identified two families of caspase-like proteins, Paracaspases (found in metazoans and Dictyostelium) and metacaspases (found in plants, fungi, and protozoa). Metazoan paracaspase prodomains contain a death domain and immunoglobulin domains. Several plant metacaspase prodomains contain zinc finger motifs resembling those in the plant hypersensitive response/cell death protein Isd-1. The human paracaspase prodomain binds Bcl10, a protein involved in the t(1;14)(p22;q32) translocation of mucosa-associated lymphoid tissue (MALT) lymphoma. Another MALT lymphoma translocation, t(11;18)(q21;q21), fuses the IAP-2 gene to the MLT1/MALT1 locus, which encodes the human paracaspase. We find that this fusion activates NF-kappaB and that the caspase domain is required for this function, since mutation of the conserved catalytic cysteine attenuates NF-kappaB activation.
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
Catalysis of the hydrolysis of a peptide bond. A peptide bond is a covalent bond formed when the carbon atom from the carboxyl group of one amino acid shares electrons with the nitrogen atom from the amino group of a second amino acid.
The paracaspase MALT1 mediates T cell antigen receptor-induced signaling to the transcription factor NF-kappaB and is indispensable for T cell activation and proliferation. Enhanced expression of MALT1 or aberrant expression of a fusion protein of the apoptosis inhibitor API2 and MALT1 has been linked to mucosa-associated lymphoid tissue lymphoma. Despite the presence of a caspase-like domain, MALT1 proteolytic activity has not yet been demonstrated. Here we show that T cell antigen receptor stimulation induced recruitment of the NF-kappaB inhibitor A20 into a complex of MALT1 and the adaptor protein Bcl-10, leading to MALT1-mediated processing of A20. API2-MALT1 expression likewise resulted in cleavage of A20. MALT1 cleaved human A20 after arginine 439 and impaired its NF-kappaB-inhibitory function. Our studies identify A20 as a substrate of MALT1 and emphasize the importance of MALT1 proteolytic activity in the 'fine tuning' of T cell antigen receptor signaling.
Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
Evidence
1:
Inferred from Physical InteractionUniProtKB
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
Evidence
2:
Inferred from Physical InteractionBHF-UCL
The paracaspase MALT1 mediates T cell antigen receptor-induced signaling to the transcription factor NF-kappaB and is indispensable for T cell activation and proliferation. Enhanced expression of MALT1 or aberrant expression of a fusion protein of the apoptosis inhibitor API2 and MALT1 has been linked to mucosa-associated lymphoid tissue lymphoma. Despite the presence of a caspase-like domain, MALT1 proteolytic activity has not yet been demonstrated. Here we show that T cell antigen receptor stimulation induced recruitment of the NF-kappaB inhibitor A20 into a complex of MALT1 and the adaptor protein Bcl-10, leading to MALT1-mediated processing of A20. API2-MALT1 expression likewise resulted in cleavage of A20. MALT1 cleaved human A20 after arginine 439 and impaired its NF-kappaB-inhibitory function. Our studies identify A20 as a substrate of MALT1 and emphasize the importance of MALT1 proteolytic activity in the 'fine tuning' of T cell antigen receptor signaling.
Evidence
3:
Inferred from Physical InteractionUniProtKB
The NF-kappaB family of transcription factors is activated in response to many stimuli, including pro-inflammatory cytokines, environmental stresses and, in the case of B and T lymphocytes, by antigenic stimulation. Bcl10 is essential for NF-kappaB activation by T- and B-cell receptors. T and B lymphocytes from Bcl10-deficient mice fail to activate NF-kappaB in response to antigen-receptor stimulation and, as a consequence, are unable to proliferate. Bcl10 overexpression is sufficient to activate NF-kappaB, a process that requires the NF-kappaB essential modulator NEMO (also known as IKK-gamma), which is the regulatory subunit of the IkappaB kinase complex. However, the cellular mechanism by which Bcl10 activates the NF-kappaB pathway remains unclear. Here we show that Bcl10 targets NEMO for lysine-63-linked ubiquitination. Notably, a mutant form of NEMO that cannot be ubiquitinated inhibited Bcl10-induced NF-kappaB activation. Paracaspase and a ubiquitin-conjugating enzyme (UBC13) were both required for Bcl10-induced NEMO ubiquitination and subsequent NF-kappaB activation. Furthermore, short interfering RNAs that reduced the expression of paracaspase and UBC13 abrogated the effects of Bcl10. Thus, the adaptor protein Bcl10 promotes activation of NF-kappaB transcription factors through paracaspase- and UBC13-dependent ubiquitination of NEMO.
Evidence
4:
Inferred from Physical InteractionIntAct
Production of the proinflammatory cytokine interleukin 1β (IL-1β) by dendritic cells is crucial in host defense. Here we identify a previously unknown role for dectin-1 in the activation of a noncanonical caspase-8 inflammasome in response to fungi and mycobacteria. Dectin-1 induced both the production and maturation of IL-1β through signaling routes mediated by the kinase Syk. Whereas the CARD9-Bcl-10-MALT1 scaffold directed IL1B transcription, the recruitment of MALT1-caspase-8 and ASC into this scaffold was crucial for processing of pro-IL-1β by caspase-8. In contrast to activation of the canonical caspase-1 inflammasome, which requires additional activation of cytosolic receptors, activation of the noncanonical caspase-8 inflammasome was independent of pathogen internalization. Thus, dectin-1 acted as an extracellular sensor for pathogens that induced both IL-1β production and maturation through a noncanonical caspase-8-dependent inflammasome for protective immunity.
Evidence
5:
Inferred from Physical InteractionUniProtKB
MALT1, BCL10 (B-cell lymphoma 10), and API2 (apoptosis inhibitor 2)-MALT1 are key molecules in mucosa-associated lymphoid tissue (MALT) lymphomagenesis. We previously reported that MALT1 and API2-MALT1 were localized only in cytoplasm, where we suggested that both molecules were likely to be active. In the study presented here, we further examined the localization-determining region by generating various mutants and were able to demonstrate that there were nuclear export signal (NES)-containing domains in the MALT1 C-terminal region. The use of leptomycin B, an NES-specific inhibitor, demonstrated that both MALT1 and API2-MALT1 were predominantly retained in the nuclei, indicating that these molecules were shuttling between nucleus and cytoplasm in an NES-dependent manner. It was also found that MALT1 was involved in the nuclear export of BCL10, which is originally localized in both nucleus and cytoplasm. These results correlate well with the nuclear BCL10 expression pattern in both t(1;14) and t(11;18) MALT lymphomas. The nucleocytoplasmic shuttling of MALT1 and BCL10 complex may indicate that these molecules are involved not only in the nuclear factor kappaB (NF-kappaB) pathway but also in other biologic functions in lymphocytes.
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
Conveys a signal across a cell to trigger a change in cell function or state. A signal is a physical entity or change in state that is used to transfer information in order to trigger a response.
Evidence
1:
Inferred from Mutant PhenotypeUniProtKB
We have carried out a large-scale identification and characterization of human genes that activate the NF-kappaB and MARK signaling pathways. We constructed full-length cDNA libraries using the oligo-capping method and prepared an arrayed cDNA pool consisting of 150 000 cDNAs randomly isolated from the libraries. For analysis of the NF-kappaB signaling pathway, we introduced each of the cDNAs into human embryonic kidney 293 cells and examined whether it activated the transcription of a luciferase reporter gene driven by a promoter containing the consensus NF-kappaB binding sites. In total, we identified 299 cDNAs that activate the NF-kappaB pathway, and we classified them into 83 genes, including 30 characterized activator genes of the NF-kappaB pathway, 28 genes whose involvement in the NF-kappaB pathways have not been characterized and 25 novel genes. We then carried out a similar analysis for the identification of genes that activate the MARK pathway, utilizing the same cDNA resource. We assayed 145 000 cDNAs and identified 57 genes that activate the MARK pathway. Interestingly, 27 genes were overlapping between the NF-kappaB and the MAPK pathways, which may indicate that these genes play cross-talking roles between these two pathways.
The NF-kappaB family of transcription factors is activated in response to many stimuli, including pro-inflammatory cytokines, environmental stresses and, in the case of B and T lymphocytes, by antigenic stimulation. Bcl10 is essential for NF-kappaB activation by T- and B-cell receptors. T and B lymphocytes from Bcl10-deficient mice fail to activate NF-kappaB in response to antigen-receptor stimulation and, as a consequence, are unable to proliferate. Bcl10 overexpression is sufficient to activate NF-kappaB, a process that requires the NF-kappaB essential modulator NEMO (also known as IKK-gamma), which is the regulatory subunit of the IkappaB kinase complex. However, the cellular mechanism by which Bcl10 activates the NF-kappaB pathway remains unclear. Here we show that Bcl10 targets NEMO for lysine-63-linked ubiquitination. Notably, a mutant form of NEMO that cannot be ubiquitinated inhibited Bcl10-induced NF-kappaB activation. Paracaspase and a ubiquitin-conjugating enzyme (UBC13) were both required for Bcl10-induced NEMO ubiquitination and subsequent NF-kappaB activation. Furthermore, short interfering RNAs that reduced the expression of paracaspase and UBC13 abrogated the effects of Bcl10. Thus, the adaptor protein Bcl10 promotes activation of NF-kappaB transcription factors through paracaspase- and UBC13-dependent ubiquitination of NEMO.
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
The process in which a hemopoietic stem cell acquires the specialized features of a B-1 B cell. B-1 B cells are a distinct subset of B cells characterized as being CD5 positive, found predominantly in the peritoneum, pleural cavities, and spleen, and enriched for self-reactivity.
Reactions, triggered in response to the presence of a foreign body or the occurrence of an injury, which result in restriction of damage to the organism attacked or prevention/recovery from the infection caused by the attack.
The t(11;18) (q21;q21) translocation is a characteristic chromosomal aberration in low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type. We previously identified a YAC clone y789F3, which includes the breakpoint at 18q21 in a MALT lymphoma patient. BAC and PAC contigs were constructed on the YAC, and BAC 193f9 was found to encompass the breakpoint region. In the present study, we further narrowed down the breakpoint region at 18q21 in five MALT lymphoma patients by means of FISH and Southern blot analyses using the plasmid contig constructed from BAC 193f9. The breakpoints at 18q21 in three of the five MALT lymphoma patients were found to be clustered approximately within the 20 kb region. By using exon amplification and cDNA library screening, we identified a novel cDNA spanning the breakpoint region that exhibited aberrant mRNA signals in four of the five MALT lymphoma patients. The nucleotide sequence predicted an 813 amino acid protein that shows significant sequence similarity to the CD22beta and laminin 5 alpha3b subunit. We refer to the gene encoding this transcript as MALT1 (Mucosa-Associated Lymphoid Tissue lymphoma translocation gene 1). The alteration of MALT1 by translocation strongly suggests that this gene plays an important role in the pathogenesis of MALT lymphoma.
Low-grade B cell lymphomas of mucosa-associated lymphoid tissue (MALT) represent a distinct clinicopathological entity that arises in a wide variety of extranodal sites. Genetically, MALT lymphomas are characterized by the t(11;18)(q21;q21). The genes involved in this translocation have been identified to be API2 on chromosome 11, which encodes an apoptotic inhibitor, and MALT1, a novel gene on chromosome 18. We identified the t(11;18)(q21;q21) by Southern blot analysis and reverse transcriptase PCR in 42% of a panel of extranodal MALT lymphomas. We also identified the breakpoints within the API2 and MALT1 genes in 7 patients, which revealed a consistent breakpoint after the third baculoviral inhibitor of apoptosis repeat domain within API2, and variable breakpoints in MALT1. We determined the API2/MALT1 fusion transcript in 2 cases by Northern blot analysis and also showed that MALT1 mRNA is constitutively expressed in a variety of human tissues. To understand the functional consequence of the translocation, we determined the pattern of expression of API2 and MALT1 through B lineage differentiation. API2 was expressed only in cell lines which correspond to mature B cells, whereas MALT1 mRNA was detectable in pre-B cells, mature B cells and plasma cells. These results suggest that fusion of MALT1 to API2 mediated by the t(11;18)(q21;q21) may result in an increased inhibition of germinal center B cell apoptosis and subsequent development of MALT lymphomas.
Caspases are cysteine proteases essential to apoptosis. We have identified two families of caspase-like proteins, Paracaspases (found in metazoans and Dictyostelium) and metacaspases (found in plants, fungi, and protozoa). Metazoan paracaspase prodomains contain a death domain and immunoglobulin domains. Several plant metacaspase prodomains contain zinc finger motifs resembling those in the plant hypersensitive response/cell death protein Isd-1. The human paracaspase prodomain binds Bcl10, a protein involved in the t(1;14)(p22;q32) translocation of mucosa-associated lymphoid tissue (MALT) lymphoma. Another MALT lymphoma translocation, t(11;18)(q21;q21), fuses the IAP-2 gene to the MLT1/MALT1 locus, which encodes the human paracaspase. We find that this fusion activates NF-kappaB and that the caspase domain is required for this function, since mutation of the conserved catalytic cysteine attenuates NF-kappaB activation.
MALT1, BCL10 (B-cell lymphoma 10), and API2 (apoptosis inhibitor 2)-MALT1 are key molecules in mucosa-associated lymphoid tissue (MALT) lymphomagenesis. We previously reported that MALT1 and API2-MALT1 were localized only in cytoplasm, where we suggested that both molecules were likely to be active. In the study presented here, we further examined the localization-determining region by generating various mutants and were able to demonstrate that there were nuclear export signal (NES)-containing domains in the MALT1 C-terminal region. The use of leptomycin B, an NES-specific inhibitor, demonstrated that both MALT1 and API2-MALT1 were predominantly retained in the nuclei, indicating that these molecules were shuttling between nucleus and cytoplasm in an NES-dependent manner. It was also found that MALT1 was involved in the nuclear export of BCL10, which is originally localized in both nucleus and cytoplasm. These results correlate well with the nuclear BCL10 expression pattern in both t(1;14) and t(11;18) MALT lymphomas. The nucleocytoplasmic shuttling of MALT1 and BCL10 complex may indicate that these molecules are involved not only in the nuclear factor kappaB (NF-kappaB) pathway but also in other biologic functions in lymphocytes.
We have carried out a large-scale identification and characterization of human genes that activate the NF-kappaB and MARK signaling pathways. We constructed full-length cDNA libraries using the oligo-capping method and prepared an arrayed cDNA pool consisting of 150 000 cDNAs randomly isolated from the libraries. For analysis of the NF-kappaB signaling pathway, we introduced each of the cDNAs into human embryonic kidney 293 cells and examined whether it activated the transcription of a luciferase reporter gene driven by a promoter containing the consensus NF-kappaB binding sites. In total, we identified 299 cDNAs that activate the NF-kappaB pathway, and we classified them into 83 genes, including 30 characterized activator genes of the NF-kappaB pathway, 28 genes whose involvement in the NF-kappaB pathways have not been characterized and 25 novel genes. We then carried out a similar analysis for the identification of genes that activate the MARK pathway, utilizing the same cDNA resource. We assayed 145 000 cDNAs and identified 57 genes that activate the MARK pathway. Interestingly, 27 genes were overlapping between the NF-kappaB and the MAPK pathways, which may indicate that these genes play cross-talking roles between these two pathways.
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
The paracaspase MALT1 mediates T cell antigen receptor-induced signaling to the transcription factor NF-kappaB and is indispensable for T cell activation and proliferation. Enhanced expression of MALT1 or aberrant expression of a fusion protein of the apoptosis inhibitor API2 and MALT1 has been linked to mucosa-associated lymphoid tissue lymphoma. Despite the presence of a caspase-like domain, MALT1 proteolytic activity has not yet been demonstrated. Here we show that T cell antigen receptor stimulation induced recruitment of the NF-kappaB inhibitor A20 into a complex of MALT1 and the adaptor protein Bcl-10, leading to MALT1-mediated processing of A20. API2-MALT1 expression likewise resulted in cleavage of A20. MALT1 cleaved human A20 after arginine 439 and impaired its NF-kappaB-inhibitory function. Our studies identify A20 as a substrate of MALT1 and emphasize the importance of MALT1 proteolytic activity in the 'fine tuning' of T cell antigen receptor signaling.
The paracaspase MALT1 mediates T cell antigen receptor-induced signaling to the transcription factor NF-kappaB and is indispensable for T cell activation and proliferation. Enhanced expression of MALT1 or aberrant expression of a fusion protein of the apoptosis inhibitor API2 and MALT1 has been linked to mucosa-associated lymphoid tissue lymphoma. Despite the presence of a caspase-like domain, MALT1 proteolytic activity has not yet been demonstrated. Here we show that T cell antigen receptor stimulation induced recruitment of the NF-kappaB inhibitor A20 into a complex of MALT1 and the adaptor protein Bcl-10, leading to MALT1-mediated processing of A20. API2-MALT1 expression likewise resulted in cleavage of A20. MALT1 cleaved human A20 after arginine 439 and impaired its NF-kappaB-inhibitory function. Our studies identify A20 as a substrate of MALT1 and emphasize the importance of MALT1 proteolytic activity in the 'fine tuning' of T cell antigen receptor signaling.
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
The process of creating protein oligomers, compounds composed of a small number, usually between three and ten, of component monomers; protein oligomers may be composed of different or identical monomers. Oligomers may be formed by the polymerization of a number of monomers or the depolymerization of a large protein polymer.
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
The NF-kappaB family of transcription factors is activated in response to many stimuli, including pro-inflammatory cytokines, environmental stresses and, in the case of B and T lymphocytes, by antigenic stimulation. Bcl10 is essential for NF-kappaB activation by T- and B-cell receptors. T and B lymphocytes from Bcl10-deficient mice fail to activate NF-kappaB in response to antigen-receptor stimulation and, as a consequence, are unable to proliferate. Bcl10 overexpression is sufficient to activate NF-kappaB, a process that requires the NF-kappaB essential modulator NEMO (also known as IKK-gamma), which is the regulatory subunit of the IkappaB kinase complex. However, the cellular mechanism by which Bcl10 activates the NF-kappaB pathway remains unclear. Here we show that Bcl10 targets NEMO for lysine-63-linked ubiquitination. Notably, a mutant form of NEMO that cannot be ubiquitinated inhibited Bcl10-induced NF-kappaB activation. Paracaspase and a ubiquitin-conjugating enzyme (UBC13) were both required for Bcl10-induced NEMO ubiquitination and subsequent NF-kappaB activation. Furthermore, short interfering RNAs that reduced the expression of paracaspase and UBC13 abrogated the effects of Bcl10. Thus, the adaptor protein Bcl10 promotes activation of NF-kappaB transcription factors through paracaspase- and UBC13-dependent ubiquitination of NEMO.
The paracaspase MALT1 mediates T cell antigen receptor-induced signaling to the transcription factor NF-kappaB and is indispensable for T cell activation and proliferation. Enhanced expression of MALT1 or aberrant expression of a fusion protein of the apoptosis inhibitor API2 and MALT1 has been linked to mucosa-associated lymphoid tissue lymphoma. Despite the presence of a caspase-like domain, MALT1 proteolytic activity has not yet been demonstrated. Here we show that T cell antigen receptor stimulation induced recruitment of the NF-kappaB inhibitor A20 into a complex of MALT1 and the adaptor protein Bcl-10, leading to MALT1-mediated processing of A20. API2-MALT1 expression likewise resulted in cleavage of A20. MALT1 cleaved human A20 after arginine 439 and impaired its NF-kappaB-inhibitory function. Our studies identify A20 as a substrate of MALT1 and emphasize the importance of MALT1 proteolytic activity in the 'fine tuning' of T cell antigen receptor signaling.
Apoptosis (programmed cell death) plays important roles in many facets of normal mammalian physiology. Host-pathogen interactions have provided evolutionary pressure for apoptosis as a defense mechanism against viruses and microbes, sometimes linking apoptosis mechanisms with inflammatory responses through NFkappaB induction. Proteins involved in apoptosis and NFkappaB induction commonly contain evolutionarily conserved domains that can serve as signatures for identification by bioinformatics methods. Using a combination of public (NCBI) and private (RIKEN) databases, we compared the repertoire of apoptosis and NFkappaB-inducing genes in humans and mice from cDNA/EST/genomic data, focusing on the following domain families: (1) Caspase proteases; (2) Caspase recruitment domains (CARD); (3) Death Domains (DD); (4) Death Effector Domains (DED); (5) BIR domains of Inhibitor of Apoptosis Proteins (IAPs); (6) Bcl-2 homology (BH) domains of Bcl-2 family proteins; (7) Tumor Necrosis Factor (TNF)-family ligands; (8) TNF receptors (TNFR); (9) TIR domains; (10) PAAD (PYRIN; PYD, DAPIN); (11) nucleotide-binding NACHT domains; (12) TRAFs; (13) Hsp70-binding BAG domains; (14) endonuclease-associated CIDE domains; and (15) miscellaneous additional proteins. After excluding redundancy due to alternative splice forms, sequencing errors, and other considerations, we identified cDNAs derived from a total of 227 human genes among these domain families. Orthologous murine genes were found for 219 (96%); in addition, several unique murine genes were found, which appear not to have human orthologs. This mismatch may be due to the still fragmentary information about the mouse genome or genuine differences between mouse and human repertoires of apoptotic genes. With this caveat, we discuss similarities and differences in human and murine genes from these domain families.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a stimulus from a fungus.
Any process that results in a change in state or activity of an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a stimulus by molecules of bacterial origin such as peptides derived from bacterial flagellin.
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
Protein involved in ubiquitin-like modifier processing, activation, conjugation or deconjugation such as Ubl-activating enzymes (E1s), Ubl-conjugating enzymes (E2s), Ubl-protein ligases (E3s), some thiol proteases (Ubiquitin carboxyl-terminal hydrolases (UCH), Ubiquitin- specific processing proteases (UBP) and ubiquitin-like proteases) and the ubiquitin-like modifier proteins. Besides signaling proteolysis, ubiquitination for example can be a signal for trafficking, kinase activation and other nonproteolytic fates.
Enzyme which catalyzes hydrolysis reaction, i.e. the addition of the hydrogen and hydroxyl ions of water to a molecule with its consequent splitting into two or more simpler molecules.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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