Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.25.1 (proteasome)
28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Disruption of the postsynaptic density (PSD), a network of scaffold proteins located in dendritic spines, is thought to be responsible for synaptic dysfunction and loss in early-stage Alzheimer's disease (AD). Extending our previous demonstration that derangement of the PSD by soluble amyloid-beta (Abeta) involves proteasomal degradation of PSD-95, a protein important for ionotropic glutamate receptor trafficking, we now show that Abeta also disrupts two other scaffold proteins, Homer1b and Shank1, that couple PSD-95 with ionotropic and metabotropic glutamate receptors. Treatment of fronto-cortical neurons with soluble Abeta results in rapid (within 1 h) and significant thinning of the PSD, decreased synaptic levels of Homer1b and Shank1, and reduced synaptic mGluR1 levels. We show that de novo protein synthesis is required for the declustering effects of Abeta on Homer1b (but not Shank1) and that, in contrast to PSD-95, Abeta-induced Homer1b and Shank1 cluster disassembly does not depend on proteasome activity. The regulation of Homer1b and Shank1 by Abeta diverges in two other respects: i) whereas the activity of both NMDAR and VDCC is required for Abeta-induced declustering of Homer1b, Abeta-induced declustering of Shank1 only requires NMDAR activity; and ii) whereas the effects of Abeta on Homer1b involve engagement of the PI-3K pathway and calcineurin phosphatase (PP2B) activity, those on Shank1 involve activation of the ERK pathway. In summary, soluble Abeta recruits discrete signalling pathways to rapidly reduce the synaptic localization of major components of the PSD and to regulate the availability of mGluR1 in the synapse.
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PMID:Disassembly of shank and homer synaptic clusters is driven by soluble beta-amyloid(1-40) through divergent NMDAR-dependent signalling pathways. 1954 99

KSR-1 is a scaffold protein that is essential for Ras-induced activation of the highly conserved RAF-MEK-ERK kinase module. Previously, we identified a close homolog of KSR-1, called KSR-2, through structural homology-based data mining. In order to further understand the role of KSR-2 in MAPK signaling, we undertook a functional proteomics approach to elucidate the dynamic composition of the KSR-2 functional complex in HEK-293 cells under conditions with and without TNF-alpha stimulation. We found nearly 100 proteins that were potentially associated with KSR-2 complex and 43 proteins that were likely recruited to the super molecular complex after TNF-alpha treatment. Our results indicate that KSR-2 may act as a scaffold protein similar as KSR-1 to mediate the MAPK core (RAF-MEK-ERK) signaling but with a distinct RAF isoform specificity, namely KSR-2 may only mediate the A-RAF signaling while KSR-1 is responsible for transducing signals only from c-RAF. In addition, KSR-2 may be involved in the activation of many MAPK downstream signaling molecules such as p38 MAPK, IKAP, AIF, and proteins involved in ubiquitin-proteasome, apoptosis, cell cycle control, and DNA synthesis and repair pathways, as well as mediating crosstalks between MAPK and several other signaling pathways, including PI3K and insulin signaling. While interactions with these molecules are not known for KSR-1, it's reasonable to hypothesize that KSR-1 may also play a similar role in mediating these downstream signaling pathways.
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PMID:Proteomic characterization of the dynamic KSR-2 interactome, a signaling scaffold complex in MAPK pathway. 1956 21

Berberine, an alkaloid derivative from Berberis vulgaris L., has been used extensively in traditional Chinese medicine to treat diarrhea and diabetes, but the underlying mechanisms for treating diabetes are not fully understood. Recent studies suggested that berberine has many beneficial biological effects, including anti-inflammation. Because type 1 diabetes is caused by T cell-mediated destruction of beta cells and severe islet inflammation, we hypothesized that berberine could ameliorate type 1 diabetes through its immune regulation properties. Here we reported that 2 weeks of oral administration of berberine prevented the progression of type 1 diabetes in half of the NOD mice and decreased Th17 and Th1 cytokine secretion. Berberine suppressed Th17 and Th1 differentiation by reducing the expression of lineage markers. We found that berberine inhibited Th17 differentiation by activating ERK1/2 and inhibited Th1 differentiation by inhibiting p38 MAPK and JNK activation. Berberine down-regulated the activity of STAT1 and STAT4 through the suppression of p38 MAPK and JNK activation, and it controlled the stability of STAT4 through the ubiquitin-proteasome pathway. Our findings indicate that berberine targets MAPK to suppress Th17 and Th1 differentiation in type 1 diabetic NOD mice. This study revealed a novel role of ERK in Th17 differentiation through down-regulation of STAT3 phosphorylation and RORgamma t expression.
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PMID:Berberine differentially modulates the activities of ERK, p38 MAPK, and JNK to suppress Th17 and Th1 T cell differentiation in type 1 diabetic mice. 1966 Oct 66

The proinflammatory cytokine TNF-alpha exerts its pleiotropic functions through activation of multiple downstream effectors, including JNK1. Yet, the underlying regulatory mechanism is incompletely understood. Here, we report that the transcription factor Myc-interacting zinc-finger protein 1 (Miz1) selectively suppresses TNF-alpha-induced JNK1 activation and cell death independently of its transcription activity. Proteomics analysis and yeast two-hybrid screening reveal that Miz1 is a JNK-associated protein. The TNF-alpha-induced activation of JNK1 is augmented in Miz1-deficient mouse embryonic fibroblasts (Miz1(-/-) MEFs), but the augmentation is abrogated by reintroduction of Miz1 or its transcription-deficient mutant. The regulation by Miz1 is highly specific, because it regulates TNF-alpha-induced TRAF2 K63-linked polyubiquitination. Neither JNK1 activation by IL-1beta or UV nor TNF-alpha-induced activation of p38, ERK, or IkappaB kinase complex is affected by the loss of Miz1. The TNF-alpha-induced cell death also is accelerated in Miz1(-/-) MEFs. Upon TNF-alpha stimulation, Miz1 is degraded rapidly by the proteasome, relieving its suppression on JNK1 activation. Thus, our results show that in addition to being a transcription factor Miz1 acts as a signal- and pathway-specific modulator or regulator that specifically regulates TNF-alpha-induced JNK1 activation and cell death.
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PMID:Miz1 is a signal- and pathway-specific modulator or regulator (SMOR) that suppresses TNF-alpha-induced JNK1 activation. 1981 9

Multiple myeloma is characterized by increased bone marrow neovascularization driven in part by vascular endothelial growth factor (VEGF). In addition, the Ras/Raf/MEK/ERK pathway is critical for the proliferation of myeloma cells and is often upregulated. Sorafenib (Nexavar) is a novel multi-kinase inhibitor that acts predominantly through inhibition of Raf-kinase and VEGF receptor 2, offering the potential for targeting two important aspects of disease biology. In in vitro studies, sorafenib-induced cytotoxicity in MM cell lines as well as freshly isolated patient myeloma cells. It retained its activity against MM cells in co-culture with stromal cells or with interleukin-6, VEGF or IGF; conditions mimicking tumor microenvironment. Examination of cellular signaling pathways showed downregulation of Mcl1 as well as decreased phosphorylation of the STAT3 and MEK/ERK, as potential mechanisms of its anti-tumor effect. Sorafenib induces reciprocal upregulation of Akt phosphorylation; and simultaneous inhibition of downstream mTOR with rapamycin leads to synergistic effects. Sorafenib also synergizes with drugs such as proteasome inhibitors and steroids. In a human in vitro angiogenesis assay, sorafenib showed potent anti-angiogenic activity. Sorafenib, through multiple mechanisms exerts potent anti-myeloma activity and these results favor further clinical evaluation and development of novel sorafenib combinations.
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PMID:Sorafenib, a dual Raf kinase/vascular endothelial growth factor receptor inhibitor has significant anti-myeloma activity and synergizes with common anti-myeloma drugs. 1993 17

Evodiamine, a major alkaloidal component of Evodiae fructus exhibits anti-tumor activities. We have previously reported that evodiamine has a marked inhibitory effect on IL-1 sensitive human melanoma A375-S2 cells proliferation, and this action might be through inactivation of PI3K signaling. However, the detailed molecular mechanisms of evodiamine-induced cell death remains poorly understood. In present study, we further confirmed that Akt is the main effector molecule involved in this pathway. Evodiamine also led to IkappaBalpha phosphorylation and degradation that reflect translocation of NF-kappaB. Pretreatment of A375-S2 cells with ubiquitin-proteasome inhibitor MG132 was shown to aggregate the evodiamine caused cell death at 24h. In addition, MG132 reduced ERK phosphorylation, increased caspase-3 activation, Fas-L expression and Bcl-2 cleavage in evodiamine-treated A375-S2 cells. These results suggested the PI3K/Akt/caspase and Fas-L/NF-kappaB signaling pathways might account for the responses of A375-S2 cell death induced by evodiamine, and these signals could be augmented by ubiquitin-proteasome pathway.
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PMID:Evodiamine-induced human melanoma A375-S2 cell death was mediated by PI3K/Akt/caspase and Fas-L/NF-kappaB signaling pathways and augmented by ubiquitin-proteasome inhibition. 2000 89

The ubiquitin-proteasome system and macroautophagy are two complementary pathways for protein degradation. Emerging evidence suggests that proteasome inhibition might be a promising approach for the treatment of cancer. In this study, we show that proteasome inhibitor MG-132 suppressed gastric cancer cell proliferation and induced macroautophagy. The induction of macroautophagy was evidenced by the formation of LC3(+) autophagosomes and the accumulation of acidic vesicular organelles and autolysosomes and was accompanied by the suppression of mammalian target of rapamycin complex 1 activity. Abolition of macroautophagy by knockdown of Class III phosphatidylinositol-3 kinase Vps34 or ATG5/7 sensitized gastric cancer cells to the antiproliferative effect of MG-132 by promoting G(2)/M cell cycle arrest. In addition, MG-132 increased ERK phosphorylation whose inhibition by MEK inhibitor significantly enhanced the antiproliferative effect of proteasome inhibition. To conclude, this study demonstrates that macroautophagy and ERK phosphorylation serve as protective mechanisms to counteract the antiproliferative effect of proteasome inhibition. This discovery may have implications for the application of proteasome-directed therapy for the treatment of cancer.
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PMID:Macroautophagy and ERK phosphorylation counteract the antiproliferative effect of proteasome inhibitor in gastric cancer cells. 2008 64

Resistance to drug treatments underlies the high lethality of pancreatic ductal adenocarcinoma. Along with others, we have recently identified that proteasome inhibition is a promising therapeutic option in this highly refractory disease. The pleiotropic effects of proteasome inhibition include the activation of apoptotic signaling pathways and also antiapoptotic signaling pathways such as EGFR, AKT and the MAP kinases that reduce the apoptotic potential of this class of drug. In this study, we sought to determine the mechanism behind the activation of EGFR in response to proteasome inhibition in pancreatic cancer cells. We found that the second-generation proteasome inhibitor NPI-0052 induced the mRNA transcription of several EGFR family ligands (EGF, HB-EGF and epiregulin), however only increases in HB-EGF were detected at the protein level. Using both pharmacological inhibitors and lentiviral-mediated shRNA knockdown of EGFR ligand expression, we discovered that ligand cleavage by MMP/ADAMs and HB-EGF expression is required for activation of EGFR in response to proteasome inhibition. Furthermore, we discover that induction of HB-EGF is dependent on reactive oxygen species and p38-MAPK signaling but not ERK and that the transcription factor SP-1 is involved in NPI-0052-induced HB-EGF transcription. Together, these results indicate that stress signaling leading to induction of HB-EGF expression and increases in MMP/ADAM-dependent HB-EGF cleavage are responsible for proteasome inhibitor-induced activation of EGFR in pancreatic cancer cells.
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PMID:Activation of EGFR by proteasome inhibition requires HB-EGF in pancreatic cancer cells. 2020 58

Many tumor suppressor proteins act to blunt the effects of mitogenic signaling pathways. Loss of function mutations in the merlin tumor suppressor underlie neurofibromatosis type 2 (NF2), a familial autosomal dominant cancer syndrome. Studies of Drosophila suggest that Hippo (hpo) is required for inhibition of cell proliferation mediated by dMer, the orthologue of human merlin. Mammalian sterile 20-like kinase-2 (Mst2) is a mammalian Hpo orthologue, and numerous studies implicate Mst2 as a tumor suppressor. Mst2 is negatively regulated by the proto-oncoprotein Raf-1 in a manner independent of the kinase activity of Raf-1. We sought to determine whether, in mammalian cells, merlin could positively regulate Mst2. We also sought to determine whether Mst2, in addition to being negatively regulated by Raf-1, might itself reciprocally regulate Raf-1. In contrast to findings from Drosophila, we find no evidence that mammalian merlin positively regulates mammalian Mst2. Instead, surprisingly, RNA interference silencing of Mst2 leads to elevated inhibitory phosphorylation of Raf-1 at Ser-259 and impaired Raf-1 kinase activity. Consequent to this, ERK pathway activation and cell proliferation are attenuated. Phosphatase-2A (PP2A) dephosphorylates Raf-1 Ser-259 in response to mitogens. Interestingly RNA interference silencing of Mst2 triggers a striking proteasome-dependent decrease in the levels of the catalytic subunit of PP2A (PP2A-C). A similar effect is achieved upon silencing of large tumor suppressor (LATS)-1 and LATS2, direct substrates of Mst2. Our studies reveal a more complex role for Mst2 than previously thought. The Mst2 --> LATS1/2 pathway, by maintaining PP2A-C levels, may, in some situations, positively affect mitogenic signaling.
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PMID:Mammalian Ste20-like kinase (Mst2) indirectly supports Raf-1/ERK pathway activity via maintenance of protein phosphatase-2A catalytic subunit levels and consequent suppression of inhibitory Raf-1 phosphorylation. 2021 43

Muscle atrophy is a consequence of chronic diseases (e.g., diabetes) and glucocorticoid-induced insulin resistance that results from enhanced activity of the ubiquitin-proteasome pathway. The PI3K/Akt pathway inhibits the FOXO-mediated transcription of the muscle-specific E3 ligase atrogin-1/MAFbx (AT-1), whereas the MEK/ERK pathway increases Sp1 activity and ubiquitin (UbC) expression. The observations raise a question about how the transcription of these atrogenes is synchronized in atrophic muscle. We tested a signaling model in which FOXO3a mediates crosstalk between the PI3K/Akt and MEK/ERK pathways to coordinate AT-1 and UbC expression. In rat L6 myotubes, dexamethasone (> or = 24 h) reduced insulin receptor substrate (IRS)-1 protein and PI3K/Akt signaling and increased AT-1 mRNA. IRS-2 protein, MEK/ERK signaling, Sp1 phosphorylation, and UbC transcription were simultaneously increased. Knockdown of IRS-1 using small interfering RNA or adenovirus-mediated expression of constitutively activated FOXO3a increased IRS-2 protein, MEK/ERK signaling, and UbC expression. Changes in PI3K/Akt and MEK/ERK signaling were recapitulated in rat muscles undergoing atrophy due to streptozotocin-induced insulin deficiency and concurrently elevated glucocorticoid production. IRS-1 and Akt phosphorylation were decreased, whereas MEK/ERK signaling and expression of IRS-2, UbC and AT-1 were increased. We conclude that FOXO3a mediates a reciprocal communication between the IRS-1/PI3K/Akt and IRS-2/MEK/ERK pathways that coordinates AT-1 and ubiquitin expression during muscle atrophy.
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PMID:FOXO3a mediates signaling crosstalk that coordinates ubiquitin and atrogin-1/MAFbx expression during glucocorticoid-induced skeletal muscle atrophy. 2037 24


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