• Biomedical Science Letters
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• v.9 no.2
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• pp.59-65
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• 2003

When cells are exposed to proteotoxic stresses such as heat shock, amino acid analogs, and heavy metals, they increase the synthesis of the heat shock proteins (HSPs) by activating the heat shock transcription factor 1 (HSF1), whose activity is controlled via multiple steps including homotrimerization, nuclear translocation, DNA binding, and hyperphosphorylation. Under unstressed conditions, the HSF1 activity is repressed through its constitutive phosphorylation by glycogen synthase kinase 3$\beta$ (GSK3$\beta$), extracellular regulated kinase 1/2 (ERK1/2), and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK). However, the protein kinase (s) responsible for HSF1 hyperphosphorylation and activation is not yet identified. In the present study, we observed that profile of p38 mitogen-activated protein kinase (p38MAPK) activation in response to heat shock was very similar to those of HSF1 hyperphosphorylation and nuclear translocation. Therefore, we investigated whether p38MAPK is involved in the heat shock-induced HSF1 activation and HSP expression. Here we show that the p38MAPK inhibitors, SB202190 and SB203580, but not other inhibitors including the MEK1/2 inhibitor PD98059 and the PI3-K inhibitor LY294002 and wortmannin, suppress HSF1 hyperphosphorylation in response to heat shock and L-azetidine 2-carboxylic acid (Azc), but not to heavy metals. Furthermore, heat shock-induced HSF1-DNA binding and HSP72 expression was specifically prevented by the p38MAPK inhibitors, but not by the MEK1/2 inhibitor and the PI3-K inhibitors. These results suggest that SB202190- and SB203580-sensitive p38MAPK may positively regulate HSP gene regulation in response to heat shock and amino acid analogs.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.5
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• pp.3187-3190
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• 2013

Background: Epidermal growth factor receptor (EGFR) is a transmembrane receptor which contributes to many processes involved in cell survival, proliferation and inhibits apoptosis, that may lead to cancer development. Gastric cancer is one of the most common diseases of digestive system that has low 5-year-survival. The aim of this research was to determine the significance of EGFR tyrosine kinase domain gene polymorphisms in gastric cancer in Iran. Materials and Methods: In the present study, 83 patients with gastric cancer and 40 normal subjects were investigated for EGFR gene polymorphisms in exons 18-21 by PCR-SSCP. Then, DNA sequencing was conducted for different mobility shift bands. Finally the data were statistically analyzed using the chi-2 test and the SPSSver.16 program. Results: Exon 18 of EGFR gene showed three different bands in SSCP pattern and DNA sequencing displayed one mutation. SSCP pattern of Exons 19 and 21 did not show different migration bands. Exon 20 of EGFR gene revealed multiple migrate bands in SSCP pattern. DNA sequencing displayed 2 mutations in this exon: one mutation was caused amino acid change and another mutation was silent. Conclusion: It may be that EGFR tyrosine kinase gene polymorphisms differ between populations and screening could be useful in gastric cancer patients who might benefit from tyrosine kinase inhibitor therapy.

• Animal cells and systems
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• v.7 no.3
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• pp.173-186
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• 2003

The transition metal cadmium is a serious occupational and environmental toxin. To inhibit cadmium-induced damage, cells respond by increasing the expression of genes that encode stress-responsive proteins. The metal-regulatory transcription factor 1 (MTF-1) is a key regulator of heavy-metal induced transcription of metallothionein-I and II and other genes in mammals and other metazoans. Transcriptional activation of genes by MTF-1 is mediated through binding to metal-responsive elements in the target gene promoters. Phosphorylation of MTF-1 plays a critical role in the cadmium-inducible transcriptional activation of metallothionein and other responses. Studies using inhibitors indicate that multiple kinases and signal transduction cascades, including those mediated by protein kinase C, tyrosine kinase and casein kinase II, are essential for cadmium-mediated transcriptional activation. In addition, calcium signaling is also involved in regulating metal-activated transcription. In several species, cadmium induces heat shock genes. Recently much progress has been made in elucidating the cellular machinery that regulates this metal-inducible gene expression. This review summarizes these recent advances in understanding the role of some known cadmium-responsive genes and the molecular mechanisms that activate metal-responsive transcription factor, MTF-1.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.3
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• pp.203-210
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• 2015

AMP-activated protein kinase (AMPK) is a key regulator of energy metabolism. Previous studies have shown that activation of AMPK results in suppression of cardiac myocyte hypertrophy via inhibition of the p70S6 kinase (p70S6K) and eukaryotic elongation factor-2 (eEF2) signaling pathways. Epigallocatechin-3-gallate (EGCG), the major polyphenol found in green tea, possesses multiple protective effects on the cardiovascular system including cardiac hypertrophy. However, the molecular mechanisms has not been well investigated. In this study, we found that EGCG could significantly reduce natriuretic peptides type A (Nppa), brain natriuretic polypeptide (BNP) mRNA expression and decrease cell surface area in H9C2 cardiomyocytes stimulated with phenylephrine (PE). Moreover, we showed that AMPK is activated in H9C2 cardiomyocytes by EGCG, and AMPK-dependent pathway participates in the inhibitory effects of EGCG on cardiac hypertrophy. Taken together, our findings provide the first evidence that the effect of EGCG against cardiac hypertrophy may be attributed to its activation on AMPK-dependent signaling pathway, suggesting the therapeutic potential of EGCG on the prevention of cardiac remodeling in patients with pressure overload hypertrophy.

• Animal cells and systems
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• v.2 no.2
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• pp.229-232
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• 1998

Lysophosphatidylcholine (LPC) has been reported to be responsible for the sustained activation of protein kinase C (PKC). As chondroqenesis is known to be regulated by PKC, this study was performed to investigate the effects of LPC on chondrogenesis of chick limb bud mesenchymes in vitro. LPC treatment of mesenchymes during micromass culture significantly enhanced chondrogenic differentiation. The most effective time of LPC on the stimulation of chondrogenesis was the first day of micromass culture. Analysis of LPC effects on the expression of PKC isoforms revealed that LPC treatment increased expression of PKCa, among the multiple PKC isoforms, in the membrane fraction on day one of culture. The stimulatory effect of LPC on chondrogenesis was abolished if PKCa was down regulated by the prolonged treatment of cells with phorbol ester. The results suqqest that LPC promotes chondrogenesis through the activation of PKCa at the early stage of chondrogenic differentiation.

• Molecules and Cells
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• v.37 no.4
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• pp.286-294
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• 2014

Mammalian polo-like kinase 1 (Plk1) has been studied intensively as a key regulator of various cell cycle events that are critical for proper M-phase progression. The polobox domain (PBD) present in Plk1's C-terminal noncatalytic region has been shown to play a central role in targeting the N-terminal kinase domain of Plk1 to specific subcellular locations. Subsequent studies reveal that PBD binds to a phosphorylated motif generated by one of the two mechanisms - self-priming by Plk1 itself or non-self-priming by a Pro-directed kinase, such as Cdc2. Here, we comparatively review the differences in the biochemical steps of these mechanisms and discuss their physiological significance. Considering the diverse functions of Plk1 during the cell cycle, a better understanding of how the catalytic activity of Plk1 functions in concert with its cisacting PBD and how this coordinated process is intricately regulated to promote Plk1 functions will be important for providing new insights into different mechanisms underlying various Plk1-mediated biological events that occur at the multiple stages of the cell cycle.

• BMB Reports
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• v.50 no.11
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• pp.535-536
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• 2017

A novel approach has been used to identify functional interactions relevant to human disease. Using high-throughput human-yeast genetic interaction screens, a first draft of disease interactome was obtained. This was achieved by first searching for candidate human disease genes that confer toxicity in yeast, and second, identifying modulators of toxicity. This study found potentially disease-relevant interactions by analyzing the network of functional interactions and focusing on genes implicated in amyotrophic lateral sclerosis (ALS), for example. In the subsequent proof-of-concept study focused on ALS, similar functional relationships between a specific kinase and ALS-associated genes were observed in mammalian cells and zebrafish, supporting findings in human-yeast genetic interaction screens. Results of combined analyses highlighted MAP2K5 kinase as a potential therapeutic target in ALS.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1995.10a
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• pp.9-15
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• 1995

When quiescent cells ate stimulated to enter the cell cycle, the thymidine kinase(TK) gene is transcriptionally activated at the border of Gl and 5. In this report we show that the human TK promoter contains multiple protein-binding sites. By site-directed mutagenesis, we identified a protein-binding site on the human TK promoter requited for conferring Gl-S-regulated transcription to a heterologous promoter and dissociated it functionally from an adjacent protein-binding domain containing an inverted CCAAT motif requited for high basal level expression. Substitution-mutation of this site results in constitutive expression of the neo reporter gene in serum-stimulated fibroblasts, as well as in cells arrested in mid-Gl by a temperature-sensitive mutation. The regulatory domains for the human TK promoter exhibit interesting symmetrical features, including a set of CCAAT motifs and sites similar to the novel Yi protein-binding site recently discovered in the mouse TK promoter. Thus, components of the hTK complex is important for hTK gene regulation.

• BMB Reports
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• v.53 no.1
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• pp.28-34
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• 2020

Sphingolipids are ubiquitous building blocks of eukaryotic cell membranes that function as signaling molecules for regulating a diverse range of cellular processes, including cell proliferation, growth, survival, immune-cell trafficking, vascular and epithelial integrity, and inflammation. Recently, several studies have highlighted the pivotal role of sphingolipids in neuroinflammatory regulation. Sphingolipids have multiple functions, including induction of the expression of various inflammatory mediators and regulation of neuroinflammation by directly effecting the cells of the central nervous system. Accumulating evidence points to sphingolipid engagement in neuroinflammatory disorders, including Alzheimer's and Parkinson's diseases. Abnormal sphingolipid alterations, which involves an increase in ceramide and a decrease in sphingosine kinase, are observed during neuroinflammatory disease. These trends are observed early during disease development, and thus highlight the potential of sphingolipids as a new therapeutic and diagnostic target for neuroinflammatory diseases.

• Bulletin of the Korean Chemical Society
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• v.18 no.4
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• pp.428-432
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• 1997

The dephosphorylation specificity of protein phosphatase 2A (PP2A), calcineurin (PP2B) and protein phosphatase 2C (PP2C) were studied in vitro using myelin basic protein (MBP) as a model substrate which was fully phosphorylated at multiple sites by protein kinase C (PKC) or cyclic AMP-dependent protein kinase (PKA). In order to determine the site specificity of phosphates in myelin basic protein, the protein was digested with trypsin and the radioactive phosphopeptide fragments were isolated by high performance liquid chromatography (HPLC) on reversed-phase column. Subsequent analysis and/or sequential manual Edman degradation of the purified phosphopeptides revealed that Thr-65 and Ser-115 were most extensively phophorylated by PKA and Ser-55 by PKC. For the dephosphorylation kinetics, the phosphorylated MBP was treated with calcineurin or PP2C with various time intervals and the reaction was terminated by direct tryptic digest. Both Thr-65 and Ser-115 residues were dephosphorylated more rapidly than any other ones by phosphatases. However it can be differentiated further by first-order kinetics that the PP2B dephosphorylated both Thr-65 and Ser-115 with almost same manner, whereas PP2C dephosphorylated somewhat preferentially the Ser-115.