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Upstream Activator (upstream + activator)

Distribution by Scientific Domains

Life Sciences	71%
Medical Sciences	28%

Selected Abstracts

Activation of MKK6, an upstream activator of p38, in Alzheimer's disease

JOURNAL OF NEUROCHEMISTRY, Issue 2 2001
Xiongwei Zhu
Mitogen-activated protein kinase (MAPK) p38 has been implicated in the pathogenesis of Alzheimer's disease, but the upstream cascade leading to p38 activation has not been elucidated in the disease. In the present study, we focused on mitogen-activated protein kinase kinase 6 (MKK6), one of the upstream activators of p38 MAPK. We found that MKK6 was not only increased but also specifically associated with granular structures in the susceptible neurons in the hippocampus and cortex of Alzheimer's disease patients, but was only weakly diffuse in the cytoplasm in neurons in control cases. Immunoblot analysis demonstrated a significant increase of MKK6 level in Alzheimer's disease compared with age-matched controls. In this regard, in hippocampal and cortical regions of individuals with Alzheimer's disease, the activated phospho-MKK6 was localized exclusively in association with pathological alterations including neurofibrillary tangles, senile plaques, neuropil threads and granular structures, overlapping with activated p38 MAPK suggesting both a functional and mechanic link. By immunoblot analysis, phospho-MKK6 is also significantly increased in AD compared with control cases. Together, these findings lend further credence to the notion that the p38 MAPK pathway is dysregulated in Alzheimer's disease and also indicates an active role for this pathway in disease pathogenesis. [source]

cAMP blocks MAPK activation and sclerotial development via Rap-1 in a PKA-independent manner in Sclerotinia sclerotiorum

MOLECULAR MICROBIOLOGY, Issue 1 2005
Changbin Chen
Summary Sclerotinia sclerotiorum is a filamentous ascomycete phytopathogen able to infect an extremely wide range of cultivated plants. Our previous studies have shown that increases in cAMP levels result in the impairment of the development of the sclerotium, a highly differentiated structure important in the disease cycle of this fungus. cAMP also inhibits the activation of a S. sclerotiorum mitogen-activated protein kinase (MAPK), which we have previously shown to be required for sclerotial maturation; thus cAMP-mediated sclerotial inhibition is modulated through MAPK. However, the mechanism(s) by which cAMP inhibits MAPK remains unclear. Here we demonstrate that a protein kinase A (PKA)-independent signalling pathway probably mediates MAPK inhibition by cAMP. Expression of a dominant negative form of Ras, an upstream activator of the MAPK pathway, also inhibited sclerotial development and MAPK activation, suggesting that a conserved Ras/MAPK pathway is required for sclerotial development. Evidence from bacterial toxins that specifically inhibit the activity of small GTPases, suggested that Rap-1 or Ras is involved in cAMP action. The Rap-1 inhibitor, GGTI-298, restored MAPK activation in the presence of cAMP, further suggesting that Rap-1 is responsible for cAMP-dependent MAPK inhibition. Importantly, inhibition of Rap-1 is able to restore sclerotial development blocked by cAMP. Our results suggest a novel mechanism involving the requirement of Ras/MAPK pathway for sclerotial development that is negatively regulated by a PKA-independent cAMP signalling pathway. Cross-talk between these two pathways is mediated by Rap-1. [source]

Phosphorylated Map Kinase (ERK1, ERK2) Expression is Associated with Early Tau Deposition in Neurones and Glial Cells, but not with Increased Nuclear DNA Vulnerability and Cell Death, in Alzheimer Disease, Pick's Disease, Progressive Supranuclear Palsy and Corticobasal Degeneration

BRAIN PATHOLOGY, Issue 2 2001
I. Ferrer
Abnormal tau phosphorylation and deposition in neurones and glial cells is one of the major features in tau pathies. The present study examines the involvement of the Ras/MEK/ERK pathway of tau phosphorylation in Alzheimer disease (AD), Pick's disease (PiD), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), by Western blotting, single and double-labelling immunohistochemistry, and p21Ras activation assay. Since this pathway is also activated in several paradigms of cell death and cell survival, activated ERK expression is also analysed with double-labelling immunohistochemistry and in situ end-labelling of nuclear DNA fragmentation to visualise activated ERK in cells with increased nuclear DNA vulnerability. The MEK1 antibody recognises one band of 45 kD that identifies phosphorylation-independent MEK1, whose expression levels are not modified in diseased brains. The ERK antibody recognises one band of 42 kD corresponding to the molecular weight of phosphorylation-independent ERK2; the expression levels, as well as the immunoreactivity of ERK in individual cells, is not changed in AD, PiD, PSP and CBD. The antibody MAPK-P distinguishes two bands of 44 kD and 42 kD that detect phosphorylated ERK1 and ERK2. MAPK-P expression levels, as seen with Western blotting, are markedly increased in AD, PiD, PSP and CBD. Moreover, immunohistochemistry discloses granular precipitates in the cytoplasm of neurones in AD, mainly in a subpopulation of neurones exhibiting early tau deposition, whereas neurones with developed neurofibrillary tangles are less commonly immunostained. MAPK-P also decorates neurones with Pick bodies in PiD, early tau deposition in neurones in PSP and CBD, and cortical achromatic neurones in CBD. In addition, strong MAPK-P immunoreactivity is found in large numbers of tau -positive glial cells in PSP and CBD, as seen with double-labelling immunohistochemistry. Yet no co-localisation of enhanced phosphorylated ERK immunoreactivity and nuclear DNA fragmentation is found in AD, PiD, PSP and CBD. Finally, activated Ras expression levels are increased in AD cases when compared with controls. These results demonstrate increased phosphorylated (active) ERK expression in association with early tau deposition in neurones and glial cells in taupathies, and suggest activated Ras as the upstream activator of the MEK/ERK pathway of tau phosphorylation in AD. [source]

Apoptosis signal-regulating kinase 1-mediated sustained p38 mitogen-activated protein kinase activation regulates mycoplasmal lipoprotein- and staphylococcal peptidoglycan-triggered Toll-like receptor 2 signalling pathways

CELLULAR MICROBIOLOGY, Issue 9 2005
Takeshi Into
Summary Toll-like receptor (TLR) 2 functions as a sensor for detecting various microbial components conserved in bacteria or fungi in innate immunity. TLR2 induces several signalling pathways linking to activation of the transcriptional factors NF-,B and AP-1 as well as induction of cell death. In human embryonic kidney 293 cells expressed human TLR2, mycoplasmal lipoproteins (MLP) or staphylococcal peptidoglycans (PGN) induced sustained phosphorylation of p38 mitogen-activated protein kinase (MAPK), accompanied by generation of reactive oxygen species. This observation encouraged us to examine roles of apoptosis signal-regulating kinase 1 (ASK1) in TLR2 signalling, because ASK1 is an upstream activator of p38 MAPK during exposure to oxidative stress and other stressful stimuli. A kinase-inactive mutant of ASK1 greatly impaired the sustained phosphorylation of p38 MAPK induced by MLP or PGN. This mutant also attenuated MLP- or PGN-induced transcriptional activities of NF-,B and AP-1 via inhibition of p38 MAPK activation. MLP- or PGN-induced cell death reactions, including DNA fragmentation and caspase-3/7 activation, were also downregulated by the ASK1 mutant via p38 MAPK inhibition. Furthermore, TLR2 signalling had a potential to phosphorylate and dephosphorylate ASK1 at Ser83 residue. Thus, MLP and PGN have capabilities to induce ASK1-dependent signalling pathways which regulate p38 MAPK activation through TLR2, leading to activation of NF-,B and AP-1 as well as induction of cell death. [source]

Metabolism of a Highly Selective Gelatinase Inhibitor Generates Active Metabolite

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 5 2007
Mijoon Lee
(4-Phenoxyphenylsulfonyl)methylthiirane (inhibitor 1) is a highly selective inhibitor of gelatinases (matrix metalloproteinases 2 and 9), which is showing considerable promise in animal models for cancer and stroke. Despite demonstrated potent, selective, and effective inhibition of gelatinases both in vitro and in vivo, the compound is rapidly metabolized, implying that the likely activity in vivo is due to a metabolite rather than the compound itself. To this end, metabolism of inhibitor 1 was investigated in in vitro systems. Four metabolites were identified by LC/MS-MS and the structures of three of them were further validated by comparison with authentic synthetic samples. One metabolite, 4-(4-thiiranylmethanesulfonylphenoxy)phenol (compound 21), was generated by hydroxylation of the terminal phenyl group of 1. This compound was investigated in kinetics of inhibition of several matrix metalloproteinases. This metabolite was a more potent slow-binding inhibitor of gelatinases (matrix metalloproteinase-2 and matrix metalloproteinase-9) than the parent compound 1, but it also served as a slow-binding inhibitor of matrix metalloproteinase-14, the upstream activator of matrix metalloproteinase-2. [source]

Activation of MKK6, an upstream activator of p38, in Alzheimer's disease

Upregulation of ,-Catenin Levels in Superior Frontal Cortex of Chronic Alcoholics

ALCOHOLISM, Issue 6 2008
Ali M. Al-Housseini
Background:, Chronic and excessive alcohol misuse results in neuroadaptive changes in the brain. The complex nature of behavioral, psychological, emotional, and neuropathological characteristics associated with alcoholism is likely a reflection of the network of proteins that are affected by alcohol-induced gene expression patterns in specific brain regions. At the molecular level, however, knowledge remains limited regarding alterations in protein expression levels affected by chronic alcohol abuse. Thus, novel techniques that allow a comprehensive assessment of this complexity will enable the simultaneous assessment of changes across a group of proteins in the relevant neural circuitry. Methods:, A proteomics analysis was performed using antibody microarrays to determine differential protein levels in superior frontal cortices between chronic alcoholics and age- and gender-matched control subjects. Seventeen proteins related to the catenin signaling pathway were analyzed, including ,-, ,-, and ,-catenins, their upstream activators cadherin-3 (type I cadherin) and cadherin-5 (type II cadherin), and 5 cytoplasmic regulators c-Src, CK1,, GSK-3,, PP2A-C,, and APC, as well as the nuclear complex partner of ,-catenin CBP and 2 downstream genes Myc and cyclin D1. ILK, G,1, G,1, and G,2, which are activity regulators of GSK-3,, were also analyzed. Results:, Both ,- and ,-catenin showed significantly increased levels, while ,-catenin did not change significantly, in chronic alcoholics. In addition, the level of the ,-catenin downstream gene product Myc was significantly increased. Average levels of the catenin regulators c-Src, CK1,, and APC were also increased in chronic alcoholics, but the changes were not statistically significant. Conclusion:, Chronic and excessive alcohol consumption leads to an upregulation of ,- and ,-catenin levels, which in turn increase downstream gene expressions such as Myc that is controlled by ,-catenin signaling. This study showed that the ,-catenin signal transduction pathway was upregulated by chronic alcohol abuse, and prompts further investigation of mechanisms underlying the upregulation of ,- and ,-catenins in alcoholism, which may have considerable pathogenic and therapeutic relevance. [source]