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Robinson MJ, Beinke S, Kouroumalis A, Tsichlis PN, Ley SC. Phosphorylation of TPL-2 on serine 400 is essential for lipopolysaccharide activation of extracellular signal-regulated kinase in macrophages. Mol Cell Biol 2007; 27:7355-64. [PMID: 17709378 PMCID: PMC2169048 DOI: 10.1128/mcb.00301-07] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Tumor progression locus 2 (TPL-2) kinase is essential for Toll-like receptor 4 activation of the mitogen-activated protein kinase extracellular signal-regulated kinase (ERK) and for upregulation of the inflammatory cytokine tumor necrosis factor (TNF) in lipopolysaccharide (LPS)-stimulated macrophages. LPS activation of ERK requires TPL-2 release from associated NF-kappaB1 p105, which blocks TPL-2 access to its substrate, the ERK kinase MEK. Here we demonstrate that TPL-2 activity is also regulated independently of p105, since LPS stimulation was still needed for TPL-2-dependent activation of ERK in Nfkb1(-/-) macrophages. In wild-type macrophages, LPS induced the rapid phosphorylation of serine (S) 400 in the TPL-2 C-terminal tail. Mutation of this conserved residue to alanine (A) blocked the ability of retrovirally expressed TPL-2 to induce the activation of ERK in LPS-stimulated Nfkb1(-/-) macrophages. TPL-2(S400A) expression also failed to reconstitute LPS activation of ERK and induction of TNF in Map3k8(-/-) macrophages, which lack endogenous TPL-2. Consistently, the S400A mutation was found to block LPS stimulation of TPL-2 MEK kinase activity. Thus, induction of TPL-2 MEK kinase activity by LPS stimulation of macrophages requires TPL-2 phosphorylation on S400, in addition to its release from NF-kappaB1 p105. Oncogenic C-terminal truncations of TPL-2 that remove S400 could promote its transforming potential by eliminating this critical control step.
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Affiliation(s)
- M J Robinson
- Division of Immune Cell Biology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
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Beinke S, Robinson MJ, Hugunin M, Ley SC. Lipopolysaccharide activation of the TPL-2/MEK/extracellular signal-regulated kinase mitogen-activated protein kinase cascade is regulated by IkappaB kinase-induced proteolysis of NF-kappaB1 p105. Mol Cell Biol 2004; 24:9658-67. [PMID: 15485931 PMCID: PMC522219 DOI: 10.1128/mcb.24.21.9658-9667.2004] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The MEK kinase TPL-2 (also known as Cot) is required for lipopolysaccharide (LPS) activation of the extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase cascade in macrophages and consequent upregulation of genes involved in innate immune responses. In resting cells, TPL-2 forms a stoichiometric complex with NF-kappaB1 p105, which negatively regulates its MEK kinase activity. Here, it is shown that lipopolysaccharide (LPS) stimulation of primary macrophages causes the release of both long and short forms of TPL-2 from p105 and that TPL-2 MEK kinase activity is restricted to this p105-free pool. Activation of TPL-2, MEK, and ERK by LPS is also demonstrated to require proteasome-mediated proteolysis. p105 is known to be proteolysed by the proteasome following stimulus-induced phosphorylation of two serines in its PEST region by the IkappaB kinase (IKK) complex. Expression of a p105 point mutant, which is not susceptible to signal-induced proteolysis, in RAW264.7 macrophages impairs LPS-induced release of TPL-2 from p105 and its subsequent activation of MEK. Furthermore, expression of wild-type but not mutant p105 reconstitutes LPS stimulation of MEK and ERK phosphorylation in primary NF-kappaB1-deficient macrophages. Consistently, pharmacological blockade of IKK inhibits LPS-induced release of TPL-2 from p105 and TPL-2 activation. These data show that IKK-induced p105 proteolysis is essential for LPS activation of TPL-2, thus revealing a novel function of IKK in the regulation of the ERK MAP kinase cascade.
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Affiliation(s)
- S Beinke
- National Institute for Medical Research, Division of Immune Cell Biology, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
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Abstract
Two members of the NF-kappaB (nuclear factor kappaB)/Rel transcription factor family, NF-kappaB1 and NF-kappaB2, are produced as precursor proteins, NF-kappaB1 p105 and NF-kappaB2 p100 respectively. These are proteolytically processed by the proteasome to produce the mature transcription factors NF-kappaB1 p50 and NF-kappaB2 p52. p105 and p100 are known to function additionally as IkappaBs (inhibitors of NF-kappaB), which retain associated NF-kappaB subunits in the cytoplasm of unstimulated cells. The present review focuses on the latest advances in research on the function of NF-kappaB1 and NF-kappaB2 in immune cells. NF-kappaB2 p100 processing has recently been shown to be stimulated by a subset of NF-kappaB inducers, including lymphotoxin-beta, B-cell activating factor and CD40 ligand, via a novel signalling pathway. This promotes the nuclear translocation of p52-containing NF-kappaB dimers, which regulate peripheral lymphoid organogenesis and B-lymphocyte differentiation. Increased p100 processing also contributes to the malignant phenotype of certain T- and B-cell lymphomas. NF-kappaB1 has a distinct function from NF-kappaB2, and is important in controlling lymphocyte and macrophage function in immune and inflammatory responses. In contrast with p100, p105 is constitutively processed to p50. However, after stimulation with agonists, such as tumour necrosis factor-alpha and lipopolysaccharide, p105 is completely degraded by the proteasome. This releases associated p50, which translocates into the nucleus to modulate target gene expression. p105 degradation also liberates the p105-associated MAP kinase (mitogen-activated protein kinase) kinase kinase TPL-2 (tumour progression locus-2), which can then activate the ERK (extracellular-signal-regulated kinase)/MAP kinase cascade. Thus, in addition to its role in NF-kappaB activation, p105 functions as a regulator of MAP kinase signalling.
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Key Words
- iκb kinase (ikk)
- nuclear factor κb (nf-κb)
- p100
- p105
- toll-like receptor (tlr)
- tumour progression locus-2 (tpl-2)
- abin, a20-binding inhibitor of nuclear factor κb
- baff, b-cell activating factor
- bmdm, bone-marrow-derived macrophage
- βtrcp, β-transducin repeat-containing protein
- cox-2, cyclo-oxygenase-2
- dc, dendritic cell
- dd, death domain
- dif, dorsal-related immunity factor
- ebna1, ebv nuclear antigen 1
- ebv, epstein–barr virus
- erk, extracellular-signal-regulated kinase
- fn14, fibroblast-growth-factor-inducible 14
- gc, germinal centre
- gm-csf, granulocyte–macrophage colony-stimulating factor
- grr, glycine-rich region
- gsk, glycogen synthase kinase
- htlv-1, human t-cell leukaemia virus type 1
- ifnβ, interferon-β
- iκb, inhibitor of nuclear factor κb
- ikk, iκb kinase
- il, interleukin
- imd, immune deficiency
- jnk, c-jun n-terminal kinase
- lmp1, latent membrane protein 1
- lps, lipopolysaccharide
- ltβr, lymphotoxin-β receptor
- map kinase, mitogen-activated protein kinase
- map 3-kinase, map kinase kinase kinase
- mef, mouse embryo fibroblast
- mek, map kinase/erk kinase
- mip, macrophage inflammatory protein
- nemo, nuclear factor κb essential modulator
- nf-κb, nuclear factor κb
- nik, nf-κb-inducing kinase
- pest region, polypeptide sequence enriched in proline (p), glutamic acid (e), serine (s) and threonine (t)
- pgrp-lc, peptidoglycan recognition protein lc
- rankl, receptor activator of nf-κb ligand
- rhd, rel homology domain
- scf, skp1/cul1/f-box
- th1, t-helper 1
- th2, t-helper 2
- tlr, toll-like receptor
- tnf, tumour necrosis factor
- tpl-2, tumour progression locus-2
- traf, tnf-receptor-associated factor
- tweak, tnf-like weak inducer of apoptosis
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Affiliation(s)
- Sören Beinke
- Division of Immune Cell Biology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, U.K
| | - Steven C. Ley
- Division of Immune Cell Biology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, U.K
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Lang V, Symons A, Watton SJ, Janzen J, Soneji Y, Beinke S, Howell S, Ley SC. ABIN-2 forms a ternary complex with TPL-2 and NF-kappa B1 p105 and is essential for TPL-2 protein stability. Mol Cell Biol 2004; 24:5235-48. [PMID: 15169888 PMCID: PMC419892 DOI: 10.1128/mcb.24.12.5235-5248.2004] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
NF-kappa B1 p105 forms a high-affinity, stoichiometric interaction with TPL-2, a MEK kinase essential for TLR4 activation of the ERK mitogen-activated protein kinase cascade in lipopolysaccharide (LPS)-stimulated macrophages. Interaction with p105 is required to maintain TPL-2 metabolic stability and also negatively regulates TPL-2 MEK kinase activity. Here, affinity purification identified A20-binding inhibitor of NF-kappa B 2 (ABIN-2) as a novel p105-associated protein. Cotransfection experiments demonstrated that ABIN-2 could interact with TPL-2 in addition to p105 but preferentially formed a ternary complex with both proteins. Consistently, in unstimulated bone marrow-derived macrophages (BMDMs), a substantial fraction of endogenous ABIN-2 was associated with both p105 and TPL-2. Although the majority of TPL-2 in these cells was complexed with ABIN-2, the pool of TPL-2 which could activate MEK after LPS stimulation was not, and LPS activation of TPL-2 was found to correlate with its release from ABIN-2. Depletion of ABIN-2 by RNA interference dramatically reduced steady-state levels of TPL-2 protein without affecting levels of TPL-2 mRNA or p105 protein. In addition, ABIN-2 increased the half-life of cotransfected TPL-2. Thus, optimal TPL-2 stability in vivo requires interaction with ABIN-2 as well as p105. Together, these data raise the possibility that ABIN-2 functions in the TLR4 signaling pathway which regulates TPL-2 activation.
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Affiliation(s)
- V Lang
- Division of Immune Cell Biology, National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom
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Beinke S, Deka J, Lang V, Belich MP, Walker PA, Howell S, Smerdon SJ, Gamblin SJ, Ley SC. NF-kappaB1 p105 negatively regulates TPL-2 MEK kinase activity. Mol Cell Biol 2003; 23:4739-52. [PMID: 12832462 PMCID: PMC162207 DOI: 10.1128/mcb.23.14.4739-4752.2003] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Activation of the oncogenic potential of the MEK kinase TPL-2 (Cot) requires deletion of its C terminus. This mutation also weakens the interaction of TPL-2 with NF-kappaB1 p105 in vitro, although it is unclear whether this is important for the activation of TPL-2 oncogenicity. It is demonstrated here that TPL-2 stability in vivo relies on its high-affinity, stoichiometric association with NF-kappaB1 p105. Formation of this complex occurs as a result of two distinct interactions. The TPL-2 C terminus binds to a region encompassing residues 497 to 534 of p105, whereas the TPL-2 kinase domain interacts with the p105 death domain. Binding to the p105 death domain inhibits TPL-2 MEK kinase activity in vitro, and this inhibition is significantly augmented by concomitant interaction of the TPL-2 C terminus with p105. In cotransfected cells, both interactions are required for inhibition of TPL-2 MEK kinase activity and, consequently, the catalytic activity of a C-terminally truncated oncogenic mutant of TPL-2 is not affected by p105. Thus, in addition to its role as a precursor for p50 and cytoplasmic inhibitor of NF-kappaB, p105 is a negative regulator of TPL-2. Insensitivity of C-terminally truncated TPL-2 to this regulatory mechanism is likely to contribute to its ability to transform cells.
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Affiliation(s)
- S Beinke
- Division of Immune Cell Biology, National Institute for Medical Research, London NW7 1AA, United Kingdom
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Lang V, Janzen J, Fischer GZ, Soneji Y, Beinke S, Salmeron A, Allen H, Hay RT, Ben-Neriah Y, Ley SC. betaTrCP-mediated proteolysis of NF-kappaB1 p105 requires phosphorylation of p105 serines 927 and 932. Mol Cell Biol 2003; 23:402-13. [PMID: 12482991 PMCID: PMC140687 DOI: 10.1128/mcb.23.1.402-413.2003] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2002] [Accepted: 09/27/2002] [Indexed: 01/01/2023] Open
Abstract
NF-kappaB1 p105 functions both as a precursor of NF-kappaB1 p50 and as a cytoplasmic inhibitor of NF-kappaB. Following the stimulation of cells with tumor necrosis factor alpha (TNF-alpha), the IkappaB kinase (IKK) complex rapidly phosphorylates NF-kappaB1 p105 on serine 927 in the PEST region. This phosphorylation is essential for TNF-alpha to trigger p105 degradation, which releases the associated Rel/NF-kappaB subunits to translocate into the nucleus and regulate target gene transcription. Serine 927 resides in a conserved motif (Asp-Ser(927)-Gly-Val-Glu-Thr-Ser(932)) homologous to the IKK target sequence in IkappaBalpha. In this study, TNF-alpha-induced p105 proteolysis was revealed to additionally require the phosphorylation of serine 932. Experiments with IKK1(-/-) and IKK2(-/-) double knockout embryonic fibroblasts demonstrate that the IKK complex is essential for TNF-alpha to stimulate phosphorylation on p105 serines 927 and 932. Furthermore, purified IKK1 and IKK2 can each phosphorylate a glutathione S-transferase-p105(758-967) fusion protein on both regulatory serines in vitro. IKK-mediated p105 phosphorylation generates a binding site for betaTrCP, the receptor subunit of an SCF-type ubiquitin E3 ligase, and depletion of betaTrCP by RNA interference blocks TNF-alpha-induced p105 ubiquitination and proteolysis. Phosphopeptide competition experiments indicate that betaTrCP binds p105 more effectively when both serines 927 and 932 are phosphorylated. Interestingly, however, betaTrCP affinity for the IKK-phosphorylated sequence on p105 is substantially lower than that on IkappaBalpha. Thus, it appears that reduced p105 recruitment of betaTrCP and subsequent ubiquitination may contribute to delayed p105 proteolysis after TNF-alpha stimulation relative to that for IkappaBalpha.
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Affiliation(s)
- Valerie Lang
- Division of Immune Cell Biology, National Institute for Medical Research, London NW7 1AA, United Kingdom
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Utku N, Bulwin GC, Beinke S, Heinemann T, Beato F, Randall J, Schnieders B, Sandhoff K, Volk HD, Milford E, Gullans SR. The human homolog of Drosophila cornichon protein is differentially expressed in alloactivated T-cells. Biochim Biophys Acta 1999; 1449:203-10. [PMID: 10209299 DOI: 10.1016/s0167-4889(99)00026-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To identify novel genes induced in the early stage of T-cell activation, mRNA expression in alloactivated human lymphocytes was examined. Differential display-reverse transcription PCR analysis revealed a 207-bp cDNA fragment which was upregulated 24 h after allostimulation of a human T-cell line. The corresponding complete 1396 bp cDNA, named TGAM77, encodes a predicted 134 amino acid protein which shares 63% homology with the cornichon (cni) protein of Drosophila melanogaster. Upregulation of TGAM77 mRNA in the early phase of T-cell activation was confirmed by Northern blot and RT-PCR analysis of activated human lymphocytes. TGAM77 mRNA is expressed in a variety of human tissues with various expression levels. In analogy to cni which is involved in an epidermal growth factor-like signaling pathway inducing cellular asymmetry in Drosophila oogenesis, TGAM77 might function in similar signaling establishing vectorial re-localization and concentration of signaling events in T-cell activation.
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Affiliation(s)
- N Utku
- Institut für Medizinische Immunologie, Campus Mitte, Charité, Humboldt Universität, Schumannstrasse 20/21, 10098, Berlin, Germany.
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Utku N, Heinemann T, Tullius SG, Bulwin GC, Beinke S, Blumberg RS, Beato F, Randall J, Kojima R, Busconi L, Robertson ES, Schülein R, Volk HD, Milford EL, Gullans SR. Prevention of acute allograft rejection by antibody targeting of TIRC7, a novel T cell membrane protein. Immunity 1998; 9:509-18. [PMID: 9806637 DOI: 10.1016/s1074-7613(00)80634-2] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A novel 75 kDa membrane protein, TIRC7, is described that exhibits a central role in T cell activation in vitro and in vivo. Modulation of TIRC7-mediated signals with specific anti-TIRC7 antibodies in vitro efficiently prevents human T cell proliferation and IL-2 secretion. Moreover, anti-TIRC7 antibodies specifically inhibit type 1 subset specific IFN-gamma expression but spare the type 2 cytokine IL-4. Diminished proliferation but not IFN-gamma secretion is reversible by exogenous rIL-2. An anti-TIRC7 antibody that cross-reacts with the 75 kDa rat homolog exhibits inhibition of rat alloimmune response in vitro and significantly prolongs kidney allograft survival in vivo. Targeting of TIRC7 may provide a novel therapeutic approach for modulation of the immune response.
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Affiliation(s)
- N Utku
- Institut für Medizinische Immunologie, Campus Mitte, Humboldt Universität zu Berlin, Germany.
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