• Genomics & Informatics
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• v.7 no.4
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• pp.203-207
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• 2009

The target of rapamycin (TOR) signaling pathway conserved from yeast to human plays critical roles in regulation of eukaryotic cell growth. It has been shown that TOR pathway is involved in several cellular processes, including ribosome biogenesis, nutrient response, autophagy and aging. However, due to the functional diversity of TOR pathway, we do not know yet some key effectors of the pathway. To find unknown effectors of TOR signaling pathway, we took advantage of a green fluorescent protein (GFP)-tagged collection of budding yeast Saccharomyces cerevisiae. We analyzed protein abundance changes by measuring the GFP fluorescence intensity of 4156 GFP-tagged yeast strains under inhibition of TOR pathway. Our proteomic analysis argues that 83 proteins are decreased whereas 32 proteins are increased by treatment of rapamycin, a specific inhibitor of TOR complex 1 (TORC1). We found that, among the 115 proteins that show significant changes in protein abundance under rapamycin treatment, 37 proteins also show expression changes in the mRNA levels by more than 2-fold under the same condition. We suggest that the 115 proteins indentified in this study may be directly or indirectly involved in TOR signaling and can serve as candidates for further investigation of the effectors of TOR pathway.

• Biomolecules & Therapeutics
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• v.29 no.4
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• pp.434-444
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• 2021

BRAF inhibitors are insufficient monotherapies for BRAF-mutated cancer; therefore, we investigated which inhibitory pathway would yield the most effective therapeutic approach when targeted in combination with BRAF inhibition. The oncogenic BRAF inhibitor, PLX4720, increased basal autophagic flux in BRAF-mutated cells compared to wild-type (WT) BRAF cells. Interestingly, early autophagy inhibition improved the effectiveness of PLX4720 regardless of BRAF mutation, whereas late autophagy inhibition did not. Although ATG5 knockout led to PLX4720 resistance in both WT and BRAF-mutated cells, the MEK inhibitor trametinib exhibited a synergistic effect on PLX4720 sensitivity in WT BRAF cells but not in BRAF-mutated cells. Conversely, the prolonged inhibition of endoplasmic reticulum (ER) stress reduced basal autophagy in BRAF-mutated cells, thereby increasing PLX4720 sensitivity. Taken together, our results suggest that the combined inhibition of ER stress and BRAF may simultaneously suppress both pro-survival ER stress and autophagy, and may therefore be suitable for treatment of BRAF-mutated tumors whose autophagy is increased by chronic ER stress. Similarly, for WT BRAF tumors, therapies targeting MEK signaling may be a more effective treatment strategy. Together, this study presents a rational combination treatment strategy to improve the efficacy of BRAF inhibitors depending on BRAF mutation status.

• 한국약용작물학회:학술대회논문집
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• 2011.04a
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• pp.108-109
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• 2011

• Molecules and Cells
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• v.37 no.9
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• pp.672-684
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• 2014

The exact causes of cell death in Parkinson's disease (PD) remain unknown despite extensive studies on PD.The identification of signaling and metabolic pathways involved in PD might provide insight into the molecular mechanisms underlying PD. The neurotoxin 1-methyl-4-phenylpyridinium ($MPP^+$) induces cellular changes characteristic of PD, and $MPP^+$-based models have been extensively used for PD studies. In this study, pathways that were significantly perturbed in $MPP^+$-treated human neuroblastoma SH-EP cells were identified from genome-wide gene expression data for five time points (1.5, 3, 9, 12, and 24 h) after treatment. The mitogen-activated protein kinase (MAPK) signaling pathway and endoplasmic reticulum (ER) protein processing pathway showed significant perturbation at all time points. Perturbation of each of these pathways resulted in the common outcome of upregulation of DNA-damage-inducible transcript 3 (DDIT3). Genes involved in ER protein processing pathway included ubiquitin ligase complex genes and ER-associated degradation (ERAD)-related genes. Additionally, overexpression of DDIT3 might induce oxidative stress via glutathione depletion as a result of overexpression of CHAC1. This study suggests that upregulation of DDIT3 caused by perturbation of the MAPK signaling pathway and ER protein processing pathway might play a key role in $MPP^+$-induced neuronal cell death. Moreover, the toxicity signal of $MPP^+$ resulting from mitochondrial dysfunction through inhibition of complex I of the electron transport chain might feed back to the mitochondria via ER stress. This positive feedback could contribute to amplification of the death signal induced by $MPP^+$.

• BMB Reports
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• v.48 no.2
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• pp.109-114
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• 2015

The COX-2/$PGE_2$ pathway has been implicated in the occurrence and progression of cancer. The underlying mechanisms facilitating the production of COX-2 and its mediator, $PGE_2$, in cancer survival remain unknown. Herein, we investigated $PGE_2$-induced COX-2 expression and signaling in HL-60 cells following menadione treatment. Treatment with $PGE_2$ activated anti-apoptotic proteins such as Bcl-2 and Bcl-xL while reducing pro-apoptotic proteins, thereby enhancing cell survival. $PGE_2$ not only induced COX-2 expression, but also prevented casapse-3, PARP, and lamin B cleavage. Silencing and inhibition of COX-2 with siRNA transfection or treatment with indomethacin led to a pronounced reduction of the extracellular levels of $PGE_2$, and restored the menadione- induced cell death. In addition, pretreatment of cells with the MEK inhibitor PD98059 and the PKA inhibitor H89 abrogated the $PGE_2$-induced expression of COX-2, suggesting involvement of the MAPK and PKA pathways. These results demonstrate that $PGE_2$ signaling acts in an autocrine manner, and specific inhibition of $PGE_2$ will provide a novel approach for the treatment of leukemia.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.3
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• pp.211-218
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• 2015

The present study showed that silymarin, a polyphenolic flavonoid isolated from milk thistle (Silybum marianum), inhibited lipopolysaccharide (LPS)-induced morphological changes in the mouse RAW264.7 macrophage cell line. We also showed that silymarin inhibited the nuclear translocation and transactivation activities of nuclear factor-kappa B (NF-${\kappa}B$), which is important for macrophage activation-associated changes in cell morphology and gene expression of inflammatory cytokines. BAY-11-7085, an NF-${\kappa}B$ inhibitor, abrogated LPS-induced morphological changes and NO production, similar to silymarin. Treatment of RAW264.7 cells with silymarin also inhibited LPS-stimulated activation of mitogen-activated protein kinases (MAPKs). Collectively, these experiments demonstrated that silymarin inhibited LPS-induced morphological changes in the RAW264.7 mouse macrophage cell line. Our findings indicated that the most likely mechanism underlying this biological effect involved inhibition of the MAPK pathway and NF-${\kappa}B$ activity. Inhibition of these activities by silymarin is a potentially useful strategy for the treatment of inflammation because of the critical roles played by MAPK and NF-${\kappa}B$ in mediating inflammatory responses in macrophages.

• Archives of Pharmacal Research
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• v.25 no.1
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• pp.93-101
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• 2002

The extract of European mistletoe ( Viscum album, L) has been used in adjuvant chemotherapy of cancer and mistletoe lectins are considered to be major active components. The present work was performed to investigate the effects of Korean mistletoe lectin (Viscum album L. coleratum agglutinin, VCA) on proliferation and apoptosis of human hepatoma cells as well as the underlying mechamisns for these effects. We showed that VCA induced atoptosis in both SK-Hep-1 and Hep 3B (p53-negative) cells through p53- and p21 -independent pathways. VCA induced apoptosis by down-regulation of Bcl-2 and by up-regulation of Bax functioning upstream of caspase-3 in both cell lines. In addition, we observed down-regulation of telomerase activity in both VCA-treated cells. Our results provide direct evidence of the anti-tumor potential of this biological response which comes from inhibition of telomerase and consequent inducing apoptosis. VCA-induced apoptosis is regulated by mitochondria controlled pathway independently of p53. These findings are important for the therapy with preparation of mistletoe because they show that telomerase-dependent mechanism can be targeted by VCA in human hepatocarcinoma. Taken together, our results suggest that the VCA, considered as a telomerase-inhibitor, can be envisaged as a candidate for enhancing sensitivity of conventional anticancer drugs.

• Korean Journal of Plant Resources
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• v.34 no.4
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• pp.377-383
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• 2021

In this study, we investigated in vitro immunostimulatory activity of fruit extracts from Pyrus ussuriensis var. hakunensis (Nakai) T.B. Lee (PUF) using mouse macrophage RAW264.7 cells. PUF increased the production of immunostimulatory factors such as NO, iNOS, IL-1β, IL-6 and TNF-α, and phagocytic activity in RAW264.7 cells. The inhibition of TLR2 and TLR4 blocked PUF-mediated production of immunostimulatory factors in RAW264.7 cells. In addition, the inhibition of MAPKs signaling pathway reduced PUF-mediated production of immunostimulatory factors. From these results, PUF may have immunostimulatory activity via TLR2/4-mediated activation of MAPKs signaling pathway. Therefore, PUF expected to be used as a potential immune-enhancing agent.

• Journal of Applied Biological Chemistry
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• v.65 no.1
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• pp.23-31
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• 2022

Oxidative stress and neuroinflammation play important roles in the pathogenesis of Alzheimer's disease (AD). This study investigated the protective effects of paeoniflorin (PF) against neuronal oxidative stress and neuroinflammation in lipopolysaccharide (LPS)-induced mice. The brains of LPS-injected control group showed significantly increased neuroinflammation by activating the nuclear factor kappa B (NF-κB) pathway and increasing inflammatory mediators. However, administration of PF significantly attenuated oxidative stress by inhibiting lipid peroxidation, nitric oxide levels, and reactive oxygen species production in the brain; PF at doses of 5 and 10 mg/kg/day downregulated the expression of NF-κB pathway-related proteins and significantly decreased inflammatory mediators including inducible nitric oxide synthase and cyclooxygenase-2. Moreover, the levels of brain-derived neurotrophic factor and its receptor, tropomycin receptor kinase B, were significantly increased in PF-treated mice. Furthermore, acetylcholinesterase activity and the ration of B-cell lymphoma 2 (Bcl-2)/Bcl-2 associated X were significantly reduced by PF in the brains of LPS-induced mice, resulting in the inhibition of cholinergic dysfunction and neuronal apoptosis. Thus, we can conclude that administration of PF to mice prevents the development of LPS-induced AD pathology through the inhibition of neuronal oxidative stress and neuroinflammation, suggesting that PF has a therapeutic potential for AD.

• Biomolecules & Therapeutics
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• v.22 no.3
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• pp.184-192
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• 2014

${\beta}$-lapachone is a naturally occurring quinone that selectively induces apoptotic cell death in a variety of human cancer cells in vitro and in vivo; however, its mechanism of action needs to be further elaborated. In this study, we investigated the effects of ${\beta}$-lapachone on the induction of apoptosis in human gastric carcinoma AGS cells. ${\beta}$-lapachone significantly inhibited cellular proliferation, and some typical apoptotic characteristics such as chromatin condensation and an increase in the population of sub-G1 hypodiploid cells were observed in ${\beta}$-lapachone-treated AGS cells. Treatment with ${\beta}$-lapachone caused mitochondrial transmembrane potential dissipation, stimulated the mitochondria-mediated intrinsic apoptotic pathway, as indicated by caspase-9 activation, cytochrome c release, Bcl-2 downregulation and Bax upregulation, as well as death receptor-mediated extrinsic apoptotic pathway, as indicated by activation of caspase-8 and truncation of Bid. This process was accompanied by activation of caspase-3 and concomitant with cleavage of poly(ADP-ribose) polymerase. The general caspase inhibitor, z-VAD-fmk, significantly abolished ${\beta}$-lapachone-induced cell death and inhibited growth. Further analysis demonstrated that the induction of apoptosis by ${\beta}$-lapachone was accompanied by inactivation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. The PI3K inhibitor LY29004 significantly increased ${\beta}$-lapachone-induced apoptosis and growth inhibition. Taken together, these findings indicate that the apoptotic activity of ${\beta}$-lapachone is probably regulated by a caspase-dependent cascade through activation of both intrinsic and extrinsic signaling pathways, and that inhibition of the PI3K/Akt signaling may contribute to ${\beta}$-lapachone-mediated AGS cell growth inhibition and apoptosis induction.