Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.25 (MEKK1)
 1,856 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The p38 MAPK pathway controls critical premitochondrial events culminating in apoptosis of UVB-irradiated human keratinocytes, but the upstream mediators of this stress signal are not completely defined. This study shows that in human keratinocytes exposed to UVB the generation of reactive oxygen species (ROS) acts as a mediator of apoptosis signal regulating kinase-1 (Ask-1), a redox-sensitive mitogen-activated protein kinase kinase kinase (MAP3K) regulating p38 MAPK and JNK cascades. The NADPH oxidase antagonist diphenylene iodonium chloride and the EGFR inhibitor AG1487 prevent UVB-mediated ROS generation, the activation of the Ask-1-p38 MAPK stress response pathway, and apoptosis, evidencing the link existing between the early plasma membrane-generated ROS and the activation of a lethal cascade initiated by Ask-1. Consistent with this, Ask-1 overexpression considerably sensitizes keratinocytes to UVB-induced mitochondrial apoptosis. Although the JNK pathway is also stimulated after UVB, the killing effect of Ask-1 overexpression is reverted by p38 MAPK inhibition, suggesting that Ask-1 exerts its lethal effects mainly through the p38 MAPK pathway. Moreover, p38alpha(-/-) murine embryonic fibroblasts are protected from UVB-induced apoptosis even if JNK activation is fully preserved. These results argue for an important role of the UVB-generated ROS as mediators of the Ask-1-p38 MAPK pathway that, by culminating in apoptosis, restrains the propagation of potentially mutagenic keratinocytes.
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PMID:Apoptosis signal regulating kinase-1 connects reactive oxygen species to p38 MAPK-induced mitochondrial apoptosis in UVB-irradiated human keratinocytes. 1702 63

Exposure of mammalian cells to ultraviolet (UV) light or glucose deprivation activates c-Jun NH2-terminal protein kinase (JNK). However, the exact mechanism by which UV induces JNK activation is not yet understood completely. Previously, we have observed that glucose deprivation activates the ASK1-SEK1-JNK signal transduction pathway. In the present study, we reveal that UVC irradiation-induced JNK activation has a different signal transduction pathway from glucose deprivation. UVC irradiation increases the interaction between JIP3 and MEKK1, SEK1, while glucose deprivation increases the interaction between JIP3 and ASK1, SEK1, and JNK. UVC irradiation activates MEKK1 rather than ASK1. We also observed that MEKK1 interacted with Grb2 and Grb2-MEKK1 complex was recruited to epidermal growth factor receptor (EGFR) after UVC irradiation. Taken together, our data demonstrate that UVC-induced JNK activation adopts a different signaling cascade (EGFR-Grb2-MEKK1-SEK1-JNK) from glucose deprivation (ASK1-SEK1-JNK).
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PMID:Differential activation of the JNK signal pathway by UV irradiation and glucose deprivation. 1702 35

Apoptosis signal-regulating kinase (ASK) 1 is a mitogen-activated protein kinase kinase kinase (MAP3K) in the c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase pathways that play multiple important roles in cytokine and stress responses. Here we show that ASK2, a highly related serine/threonine kinase to ASK1, also functions as a MAP3K only in a heteromeric complex with ASK1. We found that endogenous ASK2 was constitutively degraded in ASK1-deficient cells, suggesting that ASK1 is required for the stability of ASK2. ASK2 in a heteromeric complex with a kinase-negative mutant of ASK1 (ASK1-KN) effectively activated MAP2K and was more competent to respond to oxidative stress than ASK2 alone. Knockdown of ASK2 revealed that ASK2 was required for oxidative stress-induced JNK activation. These results suggest that ASK2 forms a functional MAP3K complex with ASK1, in which ASK1 supports the stability and the active configuration of ASK2. Moreover, ASK2 was found to activate ASK1 by direct phosphorylation, suggesting that ASK1 and ASK2 in a heteromeric complex facilitate their activities to each other by distinct mechanisms. Such a formation of functional heteromeric complex between different MAP3Ks may be advantageous for cells to cope with a wide variety of stimuli by fine regulation of cellular responses.
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PMID:Apoptosis signal-regulating kinase (ASK) 2 functions as a mitogen-activated protein kinase kinase kinase in a heteromeric complex with ASK1. 1721 May 79

Behavioral plasticity induced by the integration of two sensory signals, such as associative learning, is an important issue in neuroscience, but its evolutionary origin and diversity have not been explored sufficiently. We report here a new type of such behavioral plasticity, which we call butanone enhancement, in Caenorhabditis elegans adult hermaphrodites: C. elegans specifically enhances chemotaxis to butanone by preexposure to butanone and food. Mutant analysis revealed that this plasticity requires the AWC(ON) olfactory neuron, whose fate is known to be determined by the NSY-1/ASK1 MAPKKK (mitogen-activated protein kinase kinase kinase) cascade as well as the DAF-11 and ODR-1 guanylyl cyclases. These proteins also control many aspects of olfactory sensation/plasticity in AWC neurons and seem to provide appropriate cellular conditions for butanone enhancement in the AWC(ON) neuron. Butanone enhancement also required the functions of Bardet-Biedl syndrome genes in the AWC(ON) neuron but not other genes that control ciliary transport. Furthermore, preexposure to butanone and the odor of food was enough for the enhancement of butanone chemotaxis. These results suggest that the AWC(ON) olfactory neuron may conduct a behavioral plasticity resembling associative learning and that the functions of Bardet-Biedl syndrome genes in sensory cilia may play an important role in this plasticity.
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PMID:Caenorhabditis elegans integrates the signals of butanone and food to enhance chemotaxis to butanone. 1750 48

Parkinson's disease (PD), a neurodegenerative disorder, causes severe motor impairment due to loss of dopaminergic neurons in substantia nigra pars compacta (SNpc). MPTP, a neurotoxin that causes dopaminergic cell loss in mice, was used in an animal model to study the pathogenic mechanisms leading to neurodegeneration. We observed the activation of apoptosis signal regulating kinase (ASK1, MAPKKK) and phosphorylation of its downstream targets MKK4 and JNK, 12 h after administration of a single dose of MPTP. Further, Daxx, the death-associated protein, translocated to the cytosol selectively in SNpc neurons seemingly due to MPTP mediated down-regulation of DJ-1, the redox-sensitive protein that binds Daxx in the nucleus. Coadministration of alpha-lipoic acid (ALA), a thiol antioxidant, abolished the activation of ASK1 and phosphorylation of downstream kinases, MKK4, and JNK and prevented the down-regulation of DJ-1 and translocation of Daxx to the cytosol seen after MPTP. ALA also attenuated dopaminergic cell loss in SNpc seen after subchronic MPTP treatment. Our studies demonstrate for the first time that MPTP triggers death signaling pathway by activating ASK1 and translocating Daxx, in vivo, in dopaminergic neurons in SNpc of mice and thiol antioxidants, such as ALA terminate this cascade and afford neuroprotection.
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PMID:Activation of apoptosis signal regulating kinase 1 (ASK1) and translocation of death-associated protein, Daxx, in substantia nigra pars compacta in a mouse model of Parkinson's disease: protection by alpha-lipoic acid. 1736 8

ASK1 (apoptosis signal-regulating kinase 1), a MKKK (mitogen-activated protein kinase kinase kinase), is activated in response to cytotoxic stresses, such as H2O2 and TNFalpha (tumour necrosis factor alpha). ASK1 induction initiates a signalling cascade leading to apoptosis. After exposure of cells to H2O2, ASK1 is transiently activated by autophosphorylation at Thr845. The protein then associates with PP5 (protein serine/threonine phosphatase 5), which inactivates ASK1 by dephosphorylation of Thr845. Although this feedback regulation mechanism has been elucidated, it remains unclear how ASK1 is maintained in the dephosphorylated state under non-stressed conditions. In the present study, we have examined the possible role of PP2Cepsilon (protein phosphatase 2Cepsilon), a member of PP2C family, in the regulation of ASK1 signalling. Following expression in HEK-293 cells (human embryonic kidney cells), wild-type PP2Cepsilon inhibited ASK1-induced activation of an AP-1 (activator protein 1) reporter gene. Conversely, a dominant-negative PP2Cepsilon mutant enhanced AP-1 activity. Exogenous PP2Cepsilon associated with exogenous ASK1 in HEK-293 cells under non-stressed conditions, inactivating ASK1 by decreasing Thr845 phosphorylation. The association of endogenous PP2Cepsilon and ASK1 was also observed in mouse brain extracts. PP2Cepsilon directly dephosphorylated ASK1 at Thr845 in vitro. In contrast with PP5, PP2Cepsilon transiently dissociated from ASK1 within cells upon H2O2 treatment. These results suggest that PP2Cepsilon maintains ASK1 in an inactive state by dephosphorylation in quiescent cells, supporting the possibility that PP2Cepsilon and PP5 play different roles in H2O2-induced regulation of ASK1 activity.
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PMID:Regulation of apoptosis signal-regulating kinase 1 by protein phosphatase 2Cepsilon. 1745 47

The amyloid precursor protein (APP) is a type I transmembrane protein translocated to neuronal terminals, whose function is still unknown. The C-terminus of APP mediates its interaction with cellular adaptor and signaling proteins, some of which signal to the stress-activated protein kinase (SAPK) pathway. Here we show that ASK1, a MAPKKK that activates two SAPKs, c-Jun N-terminal-kinase (JNK) and p38, is present in a complex containing APP, phospho-MKK6, JIP1 and JNK1. In primary neurons deprived of growth factors, as well as in brains of (FAD)APP-transgenic mice, ASK1 was upregulated in neuronal projections, where it interacted with APP. In non-transgenic brains, ASK1 and APP associated mainly in the ER. Our results indicate that recruitment of ASK1 to stress-signaling complexes assembled with APP may be triggered and enhanced by cellular stress. Thus, ASK1 may be the apical MAPKKK in a signaling complex assembled with APP as a response to stress.
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PMID:Interaction of ASK1 and the beta-amyloid precursor protein in a stress-signaling complex. 1771 30

Huntington's disease (HD) is a neurodegenerative disorder resulting from the expansion of a glutamine repeat (polyQ) in the N-terminus of the huntingtin (htt) protein. Expression of polyQ-containing proteins has been previously shown to induce various cellular stress responses. Among these, activation of the c-Jun N-terminal kinase (JNK) cascade has been observed in cellular models of HD. However, the implication of the JNK pathway has not previously been evaluated in the striatum of HD animal models. Here we report that the JNK pathway participates in HD pathology in a rat model of the disease. Increased phosphorylation of the JNK target c-Jun was observed as early as 4 weeks and persisted for 13 weeks after lentiviral-mediated expression of htt171-82Q. In order to assess the importance of this pathway in HD pathology, JNK inhibitors including dominant-negative mutants of upstream kinases (ASK1(K709R), MEKK1(D1369A)), a c-Jun mutant (Delta169c-Jun) and the active domain of the scaffold protein JIP-1/IBI (IBI-JBD) were tested for their ability to mitigate the effect of htt171-82Q. The overexpression of MEKK1(D1369A) and JIP-1/IBI reduced the polyQ-related loss of DARPP-32 expression, while the other inhibitors had no effect. In all cases, the formation of EM48-positive htt inclusions and P-c-Jun immunoreactivity were unaltered. These results suggest that JNK activation is involved in HD and that blockade of this pathway may be of benefit in counteracting HD-related neurotoxicity.
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PMID:Implication of the JNK pathway in a rat model of Huntington's disease. 1902 49

Incidence of Parkinson's disease (PD) is lower in women compared to men (1:1.46), which is reflected in animal models. However, precise mechanisms are unclear. Administration of MPTP (1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine) to female mice does not lead to mitochondrial complex I inhibition as seen in males and the progressive dopaminergic cell loss in substantia nigra (SNpc) is significantly attenuated. Redox driven apoptotic signaling pathways regulated by thiol disulfide oxidoreductase(s) have been implicated in the neurodegeneration seen in PD. Oxidation of thioredoxin leads to activation of apoptosis signal regulating kinase 1 (ASK1; MAPKKK) initiating cell death cascade through MAP kinase(s). Higher constitutive expression of enzymes involved in cellular redox maintenance, such as glutathione reductase, thioredoxin, and thioredoxin reductase is observed in female brain. Exposure to MPTP activates ASK1 in male but not in female mice. Higher expression of Trx in females potentially prevents ASK1 activation. Downstream of ASK1, phosphorylation of p38 MAP kinase is seen in male but not female mice. Expression of DJ-1, the redox sensing protein is higher in females and the loss of nuclear DJ-1, followed by translocation of Daxx (death associated protein) from the nucleus to the cytosol, which promotes ASK1 mediated death cascade is not seen in females. The enzymes involved in redox maintenance potentially could play a crucial role in preventing the activation of redox driven death signaling cascade and offer neuroprotection. Theraupeutic strategies that help maintain redox homeostasis may help prevent the progressive neurodegeneration seen in PD.
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PMID:Redox activated MAP kinase death signaling cascade initiated by ASK1 is not activated in female mice following MPTP: novel mechanism of neuroprotection. 1952 88

Phosphoglycerate mutase (PGAM) is an enzyme of intermediary metabolism that converts 3-phosphoglycerate to 2-phosphoglycerate in glycolysis. Here, we discovered PGAM5 that is anchored in the mitochondrial membrane lacks PGAM activity and instead associates with the MAP kinase kinase kinase ASK1 and acts as a specific protein Ser/Thr phosphatase that activates ASK1 by dephosphorylation of inhibitory sites. Mutation of an active site His-105 in PGAM5 abolished phosphatase activity with ASK1 and phospho-Thr peptides as substrates. The Drosophila and Caenorhabditis elegans orthologs of PGAM5 also exhibit specific Ser/Thr phosphatase activity and activate the corresponding Drosophila and C. elegans ASK1 kinases. PGAM5 is unrelated to the other known Ser/Thr phosphatases of the PPP, MPP, and FCP families, and our results suggest that this member of the PGAM family has crossed over from small molecules to protein substrates and been adapted to serve as a specialized activator of ASK1.
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PMID:Mitochondrial phosphoglycerate mutase 5 uses alternate catalytic activity as a protein serine/threonine phosphatase to activate ASK1. 1959 15


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