Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rheumatoid arthritis (RA) is a connective tissue disease characterized by destruction of the joint cartilage and subsequently of the underlying bone. Cartilage destruction is due to proteolysis by enzymes called metalloproteinases (MMPs), whose production and expression are regulated by numerous local mediators such as cytokines, growth factors, prostaglandins, oxygen species, and neuropeptides. MMP activation is largely due to a stimulatory effect of cytokines including IL-1beta and TNFalpha. When these cytokines bind to their membrane receptor, they set off signaling cascades, with activation of TGFbeta-activating kinase (TAK-1), of NF-kappaB by Ikappa-B kinase, of mitogen-activated protein kinases (MAP kinases), and finally of activator protein-1 (AP-1). Tissue inhibitors of MMPs (TIMPs) specifically inhibit MMPs. The interrelations between joint inflammation and joint destruction remain poorly understood. Experimental data suggest that IL-1 may be involved chiefly in joint destruction and TNF in joint inflammation. However, TNF antagonists are potent inhibitors of joint destruction in clinical practice. These results suggest that the mediators function as a network and that inhibition of a single mediator can affect the entire web. Insights gained into the innermost mechanisms of cartilage breakdown in patients with RA have led to major therapeutic breakthroughs. Thus, TNF antagonists have proved highly effective in RA. Future progress will no doubt stem from new knowledge about the extracellular mediators and intracellular signaling pathways that lead to the production and activation of enzymes responsible for cartilage degradation.
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PMID:Cartilage breakdown in rheumatoid arthritis. 1608 81

The cytokine TNF activates multiple signaling pathways leading to cellular responses ranging from proliferation and survival to apoptosis. While most of these pathways have been elucidated in detail over the past few years, the molecular mechanism leading to the activation of the MAP kinases ERK remains ill defined and is controversially discussed. Therefore, we have analyzed TNF-induced ERK activation in various human and murine cell lines and show that it occurs in a cell-type-specific manner. In addition, we provide evidence for the involvement of the signaling components Fas-associated death domain protein (FADD), caspase-8, and c-FLIP in the pathway activating ERK in response to TNF. This conclusion is based on the following observations: (I) Overexpression of FADD, caspase-8, or a c-FLIP protein containing the death effector domains only leads to enhanced and prolonged ERK activation after TNF treatment. (II) TNF-induced ERK activation is strongly diminished in the absence of FADD. Interestingly, the enzymatic function of caspase-8 is not required for TNF-induced ERK activation. Additional evidence suggests a role for this pathway in the proliferative response of murine fibroblasts to TNF.
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PMID:The Fas-associated death domain protein/caspase-8/c-FLIP signaling pathway is involved in TNF-induced activation of ERK. 1612 31

Lipopolysaccharide (LPS) and muramyl dipeptide (MDP) are components of bacterial cell walls that cause innate immune responses and inflammation. Toll-like receptor 4 (TLR4) is a receptor for LPS and transduces signals through myeloid differentiation factor 88 (MyD88), which plays essential roles in the TLR/interleukin (IL)-1R signaling and activates MAP/ERK kinase (MEK)/ERK pathway to induce receptor activator of NF-kappaB ligand (RANKL) expression in osteoblasts. Osteoblasts express nucleotide oligomerization domain (NOD)2, an intracellular sensor for MDP, in response to LPS, IL-1 and TNF. NOD2 binds receptor-interacting protein (RIP2), a serine/threonine kinase which transduces NF-kappaB signaling. MDP synergistically enhances osteoclast formation induced by LPS, IL-1 and TNF through RANK ligand up-regulation in osteoblasts. TLR4 and NOD2 recognize bacterial components on cell surfaces and inside cells, respectively, and these signals up-regulate RANKL expression in osteoblasts, which results in enhancing osteoclast formation and function.
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PMID:[Bone destruction caused by osteoclasts]. 1646 24

Erosive osteolysis induced by implant-derived wear debris is mediated by recruitment and activation of osteoclasts in a pro-inflammatory microenvironment that is enriched with osteoclastogenic and pro-inflammatory cytokines such as RANKL and tumor necrosis factor alpha (TNF-alpha). These cytokines activate the transcription factor NF-kappaB and MAP kinases, including c-Jun, Erks, and p38, all known to be essential for the development of osteoclasts. We have recently documented that TNF and RANKL play a pivotal role in the development of inflammatory osteolysis. We have also found that polymethyl methacrylate (PMMA) particles stimulate osteoclastogenesis, at least in part, by induction of RANKL, TNF, and by activation of NF-kappaB and MAP kinases. More importantly, our data indicate that inhibitors of NF-kappaB and the MAP kinases p38 and ERK abrogate particle-induced osteoclastogenesis. In the current study, we investigated if inhibition of c-Jun N-Terminal kinase (JNK) pathway alters PMMA-induced osteoclastogenesis. Our findings point out that PMMA particles activate the JNK pathway in wild-type and TLR4-null (endotoxin-resistant) osteoclast precursors. This activation was selectively blocked in a dose-dependent fashion by the JNK inhibitor SP600125. Most importantly, we provide evidence that SP600125 inhibits osteoclast formation in a reversible manner. Collectively, our findings demonstrate that activation of the JNK pathway is essential for basal and PMMA-stimulated osteoclastogenesis, and buttress the potential significance of targeting the JNK pathway to inhibit osteolysis.
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PMID:Map kinase c-JUN N-terminal kinase mediates PMMA induction of osteoclasts. 1673 13

TNF is implicated in the suppression of neutrophil apoptosis during sepsis. Multiple signaling pathways are involved in TNF-mediated antiapoptotic signaling; a role for the MAP kinases (MAPK), ERK1/2, and p38 MAPK has been suggested. Antiapoptotic signaling is mediated principally through TNF receptor-1 (TNFR-1), and the PKC isotype-delta (delta-PKC) is a critical regulator of TNFR-1 signaling. delta-PKC associates with TNFR-1 in response to TNF and is required for NFkappaB activation and inhibition of caspase 3. The role of delta-PKC in TNF-mediated activation of MAPK is not known. The purpose of this study was to determine whether the MAPK, ERK1/2, and p38 MAPK are involved in TNF antiapoptotic signaling and whether delta-PKC is a key regulator of MAPK activation by TNF. In human neutrophils, TNF activated both p38 MAPK and ERK1/2 principally via TNFR-1. The MEK1/2 inhibitors PD098059 and U0126, but not the p38 MAPK inhibitor SB203580, decreased TNF antiapoptotic signaling as measured by caspase 3 activity. A specific delta-PKC antagonist, V1.1delta-PKC-Tat peptide, inhibited TNF-mediated ERK1/2 activation, but not p38 MAPK. ERK1/2 inhibition did not alter recruitment of delta-PKC to TNFR-1, indicating delta-PKC is acting upstream of ERK1/2. In HL-60 cells differentiated to a neutrophilic phenotype, delta-PKC depletion by delta-PKC siRNA resulted in inhibition of TNF mediated ERK1/2 activation but not p38 MAPK. Thus, ERK1/2, but not p38 MAPK, is an essential component of TNF-mediated antiapoptotic signaling. In human neutrophils, delta-PKC is a positive regulator of ERK1/2 activation via TNFR-1 but has no role in p38 MAPK activation.
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PMID:Regulation of TNF mediated antiapoptotic signaling in human neutrophils: role of delta-PKC and ERK1/2. 1713 60

Activation of the vascular endothelium with cytokines such as TNF is widely used to study the role of the vasculature in proinflammatory disease. To gain insight into mechanisms of prolonged vascular endothelial activation we compared changes in gene expression induced by continuous activation in stable tmTNF-expressing cells with changes due to acute TNF challenge in vitro. Affymetrix Genechip analysis was performed on RNA from control, acute and continuous TNF-activated endothelial cells. Only 36% of the significant changes in gene expression were convergent between the acute and continuously activated endothelial cells compared with the control. From the divergently regulated genes, for example the cytokine ENA-78 was specifically induced in chronically activated cells, while E-selectin, a cell adhesion molecule, was upregulated only in acutely activated endothelial cells. Antioxidant SOD gene induction was noted in acute activation, while a regulatory NADPH oxidase subunit was selectively upregulated in continuously activated endothelium in accordance with significant reactive oxygen species induction occurred only in these cells. Accordingly, p38 and ERK1/2, two MAP kinases downstream of reactive oxygen species, were activated in stable transmembrane-spanning precursor (tm) TNF-expressing cells and were refractory to activation with soluble TNF or VEGF. In consequence, the increased p38 MAP kinase activity contributed to increased endothelial cell migration in tmTNF-expressing cells. These data suggest that continuous activation of endothelial cells leads to specific expression and functional changes, consistent with alterations observed in dysfunctional endothelium exposed to or involved in chronic inflammation.
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PMID:Divergent and convergent effects on gene expression and function in acute versus chronic endothelial activation. 1756 77

Bidirectional signalling, i.e. simultaneous signalling through a receptor as well as its cell surface-bound ligand has been identified for several members of the TNF and TNF receptor family members. Reverse signalling through the ligands offers the advantage of an immediate feed-back and a more precise fine tuning of biological responses. Little is known about the molecular nature of reverse signalling through the ligands. CD137 ligand, member of the TNF family is expressed on monocytes and induces activation, migration, prolongation of survival and proliferation of monocytes. Here we show that reverse signalling by CD137 ligand is mediated by protein tyrosine kinases, p38 mitogen activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK)1,2, MAP/ERK kinase (MEK), Phosphoinositide-3-kinase (PI3-K) and protein kinase A (PKA) but not by protein kinase C (PKC). This study also shows that reverse signalling relies on the same signal transduction molecules as signalling through classical receptors and is in its nature not different from it.
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PMID:Signal transduction mechanisms of CD137 ligand in human monocytes. 1785 13

With only few exceptions that include Hes-1 p53, and IkappaB, the expression of genes has never been shown to be oscillatory. Here, we show that the inflammatory cytokine TNF triggers oscillations in >5000 genes. We utilize microarrays at 30-min intervals to analyze the pattern of global gene expression in murine macrophages. We find that 15% of genes in the genome underwent a significant >3-fold increase in expression, with 89% of these displaying oscillations at frequencies as low as every 50min. We analyze further two sub-clusters of genes that either began oscillating early or after a lag phase. Through the use of quantitative PCR, we confirm the oscillations and show that the oscillations are continuous. Moreover, we show that these continuous oscillations are not unique to TNF, but that related cytokines such as RANK-L produces oscillations with a unique induction profile. In the two papers accompanying this one, we analyze the mechanism of these oscillations and find that TNF also triggers oscillations in the phosphorylation of MAP kinases, and that these oscillations combine to recruit transcription factors to promoters in a cyclical fashion. The results presented here suggest that gene transcription is a highly dynamic processes, with thousands of genes displaying rapid (<60min) oscillations over time. Considering this dynamism, time-resolved measurements of gene transcription should become the experimental norm.
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PMID:TNF-induced gene expression oscillates in time. 1838 46

Oscillations in the activation of multiple signaling pathways have never been shown before. Our results presented in the previous accompanying paper showed that TNF induces highly dynamic oscillations in mRNA production in approximately 13% of the mouse genome. Here, we further analyze the TNF time-series microarray data and find that multiple signaling components downstream of the TNF receptor undergo oscillations. Prior studies implicate IkappaBalpha and A-20 as the only oscillatory components in the TNF signaling cascade. We find however, that other components, such as TRAF1, displayed oscillations. This suggested the possibility that all signaling output from the TNF receptor may be oscillatory in nature. Indeed, we show that TNF triggers oscillations in the phosphorylation of three MAP kinases, as well as p65. Because Baltimore and colleagues had proposed that NF-kappaB drives the oscillatory nature of the IkappaBalpha/NF-kappaB feedback loop, we studied the effects of an NF-kappaB super-repressor on oscillations in MAPK phosphorylation; we find that the super-repressor altered the amplitude and frequency of MAP kinase phosphorylation, but failed to abolish oscillations. These results attest to a role for NF-kappaB as a modulator, but not the sole determinant of cyclical activation of signal transduction pathways. These results, together with those of the two accompanying papers, constitute a new paradigm through which cells orchestrate signaling molecules to produce highly dynamic physiological processes such as gene transcription and protein secretion. In view of the discovery that multiple phosphorylation pathways display dynamic oscillations, time-resolved, instead of static, measurements of kinase phosphorylation should become the experimental norm.
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PMID:TNF-induced MAP kinase activation oscillates in time. 1838 51

Staphylococcus aureus is a common etiologic agent for Gram-positive sepsis, and its lipoteichoic acid (LTA) may be important in causing Gram-positive bacterial septic shock. Here, we demonstrate that highly purified LTA (pLTA) isolated from Lactobacillus plantarum inhibited aureus LTA (aLTA)-induced TNF-alpha production in THP- cells. Whereas pLTA scarcely induced TNF-alpha production, aLTA induced excessive TNF-alpha production. Interestingly, aLTA-induced TNF-alpha production was inhibited by pLTA pretreatment. Compared with pLTA, aLTA induced strong signal transduction through the MyD88, NF-kappaB, and MAP kinases. This signaling, however, was reduced by a pLTA pretreatment, and resulted in the inhibition of aLTA-induced TNF-alpha production. Whereas dealanylated LTAs, as well as native LTAs, contributed to TNF- induction or TNF-alpha reduction, deacylated LTAs did not, indicating that the acyl chain of LTA played an important role in the LTA-mediated immune regulation. These results suggest that pLTA may act as an antagonist for aLTA, and that an antagonistic pLTA may be a useful agent for suppressing the septic shock caused by Gram-positive bacteria.
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PMID:Inhibitory effects of Lactobacillus plantarum lipoteichoic acid (LTA) on Staphylococcus aureus LTA-induced tumor necrosis factor-alpha production. 1860 67


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