Tumor necrosis factor receptor-associated factor (TRAF) 4 is a new binding partner for the p70S6 serine/threonine kinase

Fleckenstein, Diana; Dirks, Wilhelm G.; Drexler, Hans G.; Quentmeier, Hilmar

doi:10.1016/s0145-2126(02)00325-9

Cited by 27 publications

(24 citation statements)

References 14 publications

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“…It has previously been shown that LTC4S is also regulated by phosphorylation, and p70S6k was found to be one of the key players in this process (10,18). The p70S6k is a serine/threonine-specific kinase localized both in the cytosol and nucleus (20). In this study, we show that the predominant p70S6k phosphorylation site on LTC4S is Ser 36 .…”

Section: Resultssupporting

confidence: 58%

Phosphorylation of Leukotriene C4 Synthase at Serine 36 Impairs Catalytic Activity

Ahmad

Ytterberg

Thulasingam

et al. 2016

Journal of Biological Chemistry

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Leukotriene C 4 synthase (LTC4S) catalyzes the formation of the proinflammatory lipid mediator leukotriene C 4 (LTC 4 ). LTC 4 is the parent molecule of the cysteinyl leukotrienes, which are recognized for their pathogenic role in asthma and allergic diseases. Cellular LTC4S activity is suppressed by PKC-mediated phosphorylation, and recently a downstream p70S6k was shown to play an important role in this process. Here, we identified Ser 36 as the major p70S6k phosphorylation site, along with a low frequency site at Thr 40 , using an in vitro phosphorylation assay combined with mass spectrometry. The functional consequences of p70S6k phosphorylation were tested with the phosphomimetic mutant S36E, which displayed only about 20% (20 mol/min/mg) of the activity of WT enzyme (95 mol/min/mg), whereas the enzyme activity of T40E was not significantly affected. The enzyme activity of S36E increased linearly with increasing LTA 4 concentrations during the steady-state kinetics analysis, indicating poor lipid substrate binding. The Ser 36 is located in a loop region close to the entrance of the proposed substrate binding pocket. Comparative molecular dynamics indicated that Ser 36 upon phosphorylation will pull the first luminal loop of LTC4S toward the neighboring subunit of the functional homotrimer, thereby forming hydrogen bonds with Arg 104 in the adjacent subunit. Because Arg 104 is a key catalytic residue responsible for stabilization of the glutathione thiolate anion, this phosphorylation-induced interaction leads to a reduction of the catalytic activity. In addition, the positional shift of the loop and its interaction with the neighboring subunit affect active site access. Thus, our mutational and kinetic data, together with molecular simulations, suggest that phosphorylation of Ser 36 inhibits the catalytic function of LTC4S by interference with the catalytic machinery. Leukotriene (LT)2 C 4 synthase (LTC4S) catalyzes the formation of LTC 4 by conjugating the unstable allylic epoxide intermediate LTA 4 with reduced glutathione (GSH) (1). LTC 4 and its metabolites LTD 4 and LTE 4 are known as cysteinyl leukotrienes (cys-LTs), which are involved in bronchial asthma and allergic inflammatory disorders (1-3). The cys-LTs signal through two G-protein-coupled receptors, denoted CysLT1 and CysLT2, to exert their biological functions such as smooth muscle contraction and increased vascular permeability. Several drugs, typified by montelukast, have been developed that specifically target the CysLT1 receptor (4). Recently, additional G-protein-coupled receptors that recognize cys-LTs have been identified, in particular gpr17 and CysLT3 (5, 6). The increasing complexity of cys-LT signaling has promoted research and drug development efforts targeting the upstream LTC4S as it catalyzes the committed step in cys-LT biosynthesis (7).The leukotrienes are derived from arachidonic acid through the 5-lipoxygenase pathway where cytosolic phospholipase A 2 , 5-lipoxygenase, and 5-lipoxygenase-activating protein play important rol...

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Section: Resultssupporting

confidence: 58%

Phosphorylation of Leukotriene C4 Synthase at Serine 36 Impairs Catalytic Activity

Ahmad

Ytterberg

Thulasingam

et al. 2016

Journal of Biological Chemistry

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“…Through its interaction with p47 phox , the adapter subunit of NAD(P)H oxidase, TRAF4 is involved in the oxidative activation of JNK mediated by TNF-a and HIV-1 Tat [40]. Furthermore, TRAF4 expression facilitates TNF-a-induced S6 kinase activity [14]. Signaling through GITR has been shown to counteract the suppressive function of T reg cells, leading to organ-specific autoimmune disease [18,19,41].…”

Section: Discussionmentioning

confidence: 99%

“…Consistent with its cytoplasmic localization, TRAF4 has been observed in over-expression systems and in vitro binding assays to interact with the p75 neural growth factor receptor and the lymphotoxin-b receptor [10,12]. Paradoxically, TRAF4 has been implicated in promoting apoptotic pathways mediated by p53, yet has been observed to inhibit Fasmediated cell death [13,14]. Expression of TRAF4 in T cells is dependent on stimulators of the NF-kB pathway [11].…”

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confidence: 96%

TRAF4 functions as an intermediate of GITR-induced NF-?B activation

Esparza

Arch

2004

CMLS, Cell. Mol. Life Sci.

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Members of the tumor necrosis factor receptor (TNFR) family regulate the activation, differentiation, and function of many cell types, including cells of the immune system. TNFR-associated factors (TRAFs) function as adapter molecules controlling signaling pathways triggered by TNFR family members, such as activation of nuclear factor kappaB (NF-kappaB). Despite intensive research, the function of TRAF4 in signaling pathways triggered by TNFR-related proteins remains enigmatic. Intriguingly, our functional studies indicated that TRAF4 augments NF-kappaB activation triggered by glucocorticoid-induced TNFR (GITR), a receptor expressed on T cells, B cells, and macrophages. Further analyses revealed that TRAF4-mediated NF-kappaB activation downstream of GITR depends on a previously mapped TRAF-binding site in the cytoplasmic domain of the receptor and is inhibited by the cytoplasmic protein A20. GITR is thought to inhibit the suppressive function of regulatory T cells (Treg cells) and to promote activation of T cells. Taken together, our studies provide the first indications that TRAF4 elaborates GITR signaling and suggest that TRAF4 can modulate the suppressive functions of Treg cells.

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“…TRAF4 has so far not been shown to interact physically with receptors of the TNFR superfamily, in spite of its high homology to the other TRAFs. However, TRAF4 can signal to JNK as well as to NF-κB, and situations have been discovered in which it is involved in signal transmission downstream of TNF-superfamily receptors (Esparza and Arch, 2004;Fleckenstein et al, 2003;Ye et al, 1999). In view of these connections, we consider it useful to discuss the role of TRAF4 in the context of TNF-dependent cell-shape changes.…”

Section: Morphogenetic Functions Of Trafsmentioning

confidence: 99%

Looking beyond death: a morphogenetic role for the TNF signalling pathway

Mathew

Haubert

Krönke

et al. 2009

Journal of Cell Science

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Tumour necrosis factor α (TNFα) is a pro-inflammatory mediator with the capacity to induce apoptosis. An integral part of its apoptotic and inflammatory programmes is the control of cell shape through modulation of the cytoskeleton, but it is now becoming apparent that this morphogenetic function of TNF signalling is also employed outside inflammatory responses and is shared by the signalling pathways of other members of the TNF-receptor superfamily. Some proteins that are homologous to the components of the TNF signalling pathway, such as the adaptor TNF-receptor-associated factor 4 and the ectodysplasin A receptor (and its ligand and adaptors), have dedicated morphogenetic roles. The mechanism by which TNF signalling affects cell shape is not yet fully understood, but Rhofamily GTPases have a central role. The fact that the components of the TNF signalling pathway are evolutionarily old suggests that an ancestral cassette from unicellular organisms has diversified its functions into partly overlapping morphogenetic, inflammatory and apoptotic roles in multicellular higher organisms.

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Tumor necrosis factor receptor-associated factor (TRAF) 4 is a new binding partner for the p70S6 serine/threonine kinase

Cited by 27 publications

References 14 publications

Phosphorylation of Leukotriene C4 Synthase at Serine 36 Impairs Catalytic Activity

Phosphorylation of Leukotriene C4 Synthase at Serine 36 Impairs Catalytic Activity

TRAF4 functions as an intermediate of GITR-induced NF-?B activation

Looking beyond death: a morphogenetic role for the TNF signalling pathway

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