Protein Phosphatase 6 Down-regulates TAK1 Kinase Activation in the IL-1 Signaling Pathway

Department of Molecular Biology, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan.
Journal of Biological Chemistry (Impact Factor: 4.57). 01/2007; 281(52):39891-6. DOI: 10.1074/jbc.M608155200
Source: PubMed


TAK1 (transforming growth factor beta-activated kinase 1) is a serine/threonine kinase that is a mitogen-activated protein kinase kinase kinase and an essential intracellular signaling component in inflammatory signaling pathways. Upon stimulation of cells with inflammatory cytokines, TAK1 binds proteins that stimulate autophosphorylation within its activation loop and is thereby catalytically activated. This activation is transient; it peaks within a couple of minutes and is subsequently down-regulated rapidly to basal levels. The mechanism of down-regulation of TAK1 has not yet been elucidated. In this study, we found that toxin inhibition of type 2A protein phosphatases greatly enhances interleukin 1 (IL-1)-dependent phosphorylation of Thr-187 in the TAK1 activation loop as well as the catalytic activity of TAK1. From proteomic analysis of TAK1-binding proteins, we identified protein phosphatase 6 (PP6), a type-2A phosphatase, and demonstrated that PP6 associated with and inactivated TAK1 by dephosphorylation of Thr-187. Ectopic and endogenous PP6 co-precipitated with TAK1, and expression of PP6 reduced IL-1 activation of TAK1 but did not affect osmotic activation of MLK3, another MAPKKK. Reduction of PP6 expression by small interfering RNA enhances IL-1-induced phosphorylation of Thr-187 in TAK1. Enhancement occurred without change in levels of PP2A showing specificity for PP6. Our results demonstrate that PP6 specifically down-regulates TAK1 through dephosphorylation of Thr-187 in the activation loop, which is likely important for suppressing inflammatory responses via TAK1 signaling pathways.

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    • "We found that LPS activated TAK1 and its downstream IKK and p38 in macrophages (Figure 4A, middle 4 lanes), and Tak1 deficiency reduced activation of both IKK and p38 (Figure 4A, left 4 lanes). TAK1 activity was monitored by phosphorylation of Thr 187 (Figure 4A, top panel), which is known to be associated with activation of TAK1 [40] However, non-specific bands were detected around the phosphorylated TAK1 in macrophages protein extracts, which were seen even in unstimulated macrophagse (Figure 4A, asterisks). Thus, we also utilized retardation of TAK1 band on SDS-PAGE to monitor TAK1 activation, which is caused by phosphorylation of several sites associated with TAK1 activation [41], [42]. "
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    ABSTRACT: Macrophages play diverse roles in tissue homeostasis and immunity, and canonically activated macrophages are critically associated with acute inflammatory responses. It is known that activated macrophages undergo cell death after transient activation in some settings, and the viability of macrophages impacts on inflammatory status. Here we report that TGFβ- activated kinase (TAK1) activators, TAK1-binding protein 1 (TAB1) and TAK1-binding protein 2 (TAB2), are critical molecules in the regulation of activated macrophage survival. While deletion of Tak1 induced cell death in bone marrow derived macrophages even without activation, Tab1 or Tab2 deletion alone did not profoundly affect survival of naïve macrophages. However, in lipopolysaccharide (LPS)-activated macrophages, even single deletion of Tab1 or Tab2 resulted in macrophage death with both necrotic and apoptotic features. We show that TAB1 and TAB2 were redundantly involved in LPS-induced TAK1 activation in macrophages. These results demonstrate that TAK1 activity is the key to activated macrophage survival. Finally, in an in vivo setting, Tab1 deficiency impaired increase of peritoneal macrophages upon LPS challenge, suggesting that TAK1 complex regulation of macrophages may participate in in vivo macrophage homeostasis. Our results demonstrate that TAB1 and TAB2 are required for activated macrophages, making TAB1 and TAB2 effective targets to control inflammation by modulating macrophage survival.
    PLoS ONE 04/2014; 9(4):e94982. DOI:10.1371/journal.pone.0094982 · 3.23 Impact Factor
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    • "VopZ might interfere with induction of the TAK1 conformational shift that is thought to enable activating autophosphorylation, either via interacting with a TAB protein or with TAK1 itself. Alternatively, VopZ might increase the activity of a TAK1-associated phosphatase , such as the type 2A protein phosphatase PP6 (Kajino et al., 2006), or possess phosphatase activity itself, although no conserved enzymatic domains were detected. The TAK1- inhibitory activity of VopZ was correlated with punctate localization of VopZ; however, it is currently unclear whether VopZ's localization directly contributes to its activity. "
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    ABSTRACT: Vibrio parahaemolyticus type III secretion system 2 (T3SS2) is essential for the organism's virulence, but the effectors required for intestinal colonization and induction of diarrhea by this pathogen have not been identified. Here, we identify a type III secretion system (T3SS2)-secreted effector, VopZ, that is essential for V. parahaemolyticus pathogenicity. VopZ plays distinct, genetically separable roles in enabling intestinal colonization and diarrheagenesis. Truncation of VopZ prevents V. parahaemolyticus colonization, whereas deletion of VopZ amino acids 38-62 abrogates V. parahaemolyticus-induced diarrhea and intestinal pathology but does not impair colonization. VopZ inhibits activation of the kinase TAK1 and thereby prevents the activation of MAPK and NF-κB signaling pathways, which lie downstream. In contrast, the VopZ internal deletion mutant cannot counter the activation of pathways regulated by TAK1. Collectively, our findings suggest that VopZ's inhibition of TAK1 is critical for V. parahaemolyticus to induce diarrhea and intestinal pathology.
    Cell Reports 04/2013; 3(5). DOI:10.1016/j.celrep.2013.03.039 · 8.36 Impact Factor
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    • "ItisthoughtthatdysregulatedandprolongedTGF-b signalingisimplicatedindiseasestates.Inordertoprevent excessiveactionsofTGF-b1,amechanismforefficientdown- regulationofTAK1activitywouldbeimportant.Ingeneral, tightregulationofintracellularsignalingcascadesisaccomplishedbycyclicphosphorylationanddephosphorylation .In thecaseofTAK1inactivation,severalmembersoftheSer/Thr proteinphosphatasefamilyhavebeendemonstratedtonega- tivelyregulateTAK1activity.PP2Ciscapableofbindingand dephosphorylatingTAK1in293cellsundernonstimulated condition[88] [89].AnotherSer/Thrproteinphosphatase familymember,PP6,interactswithandnegativelyregulates IL-1-inducedTAK1in293cells[90]andTNF-a-inducedTAK1 infibroblasts[91]. WehavereportedthatTAK1activationbyTGF-b1in glomerularmesangialcellsisnegativelyregulatedbyanother Ser/Thrproteinphosphatasefamilymember,PP2A[92], whichwaspreviouslyshowntomediateTGF-binhibitionof p70S6kinase(p70S6K)toinducecell-cycleG1arrest[49]. "
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    ABSTRACT: Transforming growth factor-β (TGF-β) is a multifunctional cytokine that regulates a wide variety of cellular functions, including cell growth, cellular differentiation, apoptosis, and wound healing. TGF-β1, the prototype member of the TGF-β superfamily, is well established as a central mediator of renal fibrosis. In chronic kidney disease, dysregulation of expression and activation of TGF-β1 results in the relentless synthesis and accumulation of extracellular matrix proteins that lead to the development of glomerulosclerosis and tubulointerstitial fibrosis, and ultimately to end-stage renal disease. Therefore, specific targeting of the TGF-β signaling pathway is seemingly an attractive molecular therapeutic strategy in chronic kidney disease. Accumulating evidence demonstrates that the multifunctionality of TGF-β1 is connected with the complexity of its cell signaling networks. TGF-β1 signals through the interaction of type I and type II receptors to activate distinct intracellular pathways. Although the Smad signaling pathway is known as a canonical pathway induced by TGF-β1, and has been the focus of many previous reviews, importantly TGF-β1 also induces various Smad-independent signaling pathways. In this review, we describe evidence that supports current insights into the mechanism and function of TGF-β-activated kinase 1 (TAK1), which has emerged as a critical signaling molecule in TGF-β-induced Smad-independent signaling pathways. We also discuss the functional role of TAK1 in mediating the profibrotic effects of TGF-β1.
    06/2012; 31(2):94–105. DOI:10.1016/j.krcp.2012.04.322
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