• Journal of Microbiology and Biotechnology
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• 제21권5호
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• pp.525-528
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• 2011

The Raf-1 kinase inhibitory protein (RKIP) can regulate multiple key signaling pathways. Specifically, RKIP binds to Raf-1 kinase and inhibits the Ras-Raf-1-MEK1/2- ERK1/2 pathway. Additionally, Raf-1 has been shown to translocate to mitochondria and thereby protect cells from stress-mediated apoptosis. Recently, HBx was found to stimulate the mitochondrial translocation of Raf-1, contributing to the anti-apoptotic effect. We found that RKIP was downregulated during HBx-mediated hepatocarcinogenesis. In this study, we show that RKIP bound to Raf-1 and consequently inhibited the translocation of Raf-1 into mitochondria. This promoted the apoptosis of cells treated with apoptotic stimulus. Thus, the downregulation of RKIP increased the level of free Raf-1 and thereby elevated the mitochondrial translocation of Raf-1 during HBx-mediated hepatocarcinogenesis. The elevated Raf-1 mitochondrial translocation induced the increased anti-apoptotic effect and subsequently promoted HBx-mediated hepatocarcinogenesis.

• Animal cells and systems
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• 제1권4호
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• pp.637-640
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• 1997

Raf-1, a cytoplasmic serine/threonine protein kinase, serves as a central intermediate in many signaling pathways in cell proliferation, differentiation, and development. In this study, we investigated that B-raf, Drosophila homolog of the human c-raf-1, is involved in ultraviolet (UV) responsive events by using hypomorphic mutant $D-raf^{c110}$ and Draf-lacZ transgenic fly. At first, effect of UV damage on the survival of wild-type and $D-raf^{C110}$ strains was examined. In terms of $1/LD_{50}$ value, the relative ratio of UV sensitivities of wild-type versus $D-raf^{C110}$ strain was 1 : 2.2. By using quantitative $\beta$-galactosidase activity analysis, transcriptional activity of the D-raf gene promoter was also examined in UV-irradiated Draf-lacZ transgenic larvae. UV irradiation increased the expression of lacZ reporter gene in Draf-lacZ transgenic fly. However, in $D-raf^{C110}$ strain the transcriptional activity of D-raf gene promoter by UV irradiation was extensively reduced. Results obtained in this study suggest that D-raf plays a role in UV response, leading to better survival of Drosophila to UV damage.

• 한국식품영양학회지
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• 제28권1호
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• pp.111-118
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• 2015

이전 연구들에서 rutin과 quercetin을 포함한 여러 flavonoids의 암예방 활성이 보고되었으나, rutin의 경우 섭취 시 체내에서 HVA, HPAA, DHT라는 대사체로 변형되어 흡수된다. 그러나, 이들 대사체와 관련한 암예방 효능 및 그 분자생물학적 작용기작에 대한 연구 결과는 보고된 바가 없어, 본 연구에서 이를 규명하였다. DHT는 EGF로 유도된 세포 변형을 억제하였으며, AP-1 전사인자의 활성 또한 억제하였다. DHT는 Raf-1 효소 활성을 효과적으로 저해하므로서 MEK 및 ERK의 인산화를 억제하였으며, Raf-1과 ATP는 비경쟁적으로 직접 결합하여 Raf-1 효소 활성을 저해한다는 사실을 밝혀내었다. 이와는 대조적으로, rutin은 EGF로 유도된 세포 변형, AP-1 활성, ERK 신호전달체계, Raf-1 효소 활성을 억제하지 못하였다. 이상의 연구결과는 DHT의 암예방 활성이 발암과정과 밀접한 연관이 있는 Raf-1 효소 활성을 억제하여 세포 변형을 억제하는 것과 관련되어 있다는 것을 제시한다.

• BMB Reports
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• 제43권3호
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• pp.205-211
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• 2010

Sprouty (Spry) proteins have previously been suggested as negative regulators of the MAPK pathway through interaction with Raf-1. However, the molecular basis of this inhibition has not been elucidated. In this study, we used cells expressing FLAGtagged Raf-1 with point mutations at known phosphorylation sites to reveal that activation of Raf-1 mutants does not correlate with their degree of interaction with Spry2. The association of Raf-1 with Spry2 in intact cells was further corroborated by immunofluorescence colocalization. Additionally, there was no significant change observed in the strength of interaction between Raf-1 mutants and Spry2 after paclitaxel treatment despite differences in the activation levels of these mutants. Thus, our study provides the evidence that Spry2 does not directly regulate Raf-1 kinase activity, but instead acts as a scaffolding protein that assists interactions between Raf-1 kinase and its direct regulators.

• Animal cells and systems
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• 제2권1호
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• pp.117-122
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• 1998

D-raf, a Drosophila homolog of the human c-raf-1, is known as a signal transducer in cell proliferation and differentiation. A previous study found that the D-raf gene expression is regulated by the DNA replication-related element (DRE)/DRE-binding factor (DREF) system. In this study, we found the sequences homologous to transcription factor C/EBP, MyoD, STAT and Myc recognition sites in the D-raf promoter. We have generated various base substitutional mutations in these recognition sites and subsequently examined their effects on D-raf promoter activity through transient CAT assays in Kc cells with reporter plasmids p5'-878DrafCAT carrying the mutations in these binding sites. Through gel mobility shift assay using nuclear extracts of Kc cells, we detected factors binding to these recognition sites. Our results show that transcription factor C/EBP, STAT and Myc binding sites in D-raf promoter region play a positive role in transcriptional regulation of the D-raf gene and the Myo D binding site plays a negative role.

• 생명과학회지
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• 제8권1호
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• pp.14-26
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• 1998

본 연구에서는 SDS/polyacrylamide 젤 전기영동에 의한 쥐의 성장과정에 따른 소뇌의 단백질양상의 변화양상과 immunocytochemistry를 이용하여 c-raf a-raf kinase의 정상 소뇌에서의 분포에 대해 관찰 하였으며 western blot을 이용하여 소뇌의 단백질들에서 c-raf의 존재에 대해 살펴보았다. 단백질 양상에서 쥐의 성장에 따라 crude에선,ㄴ 49,200 dalton과 169,000 dalton 사이의 bands가 양적 증가를 보였으며 cytosolic fraction 에서는 37,800 dalton의 band가 양적 증가를 보이는데 비해 membrane fraction 에서는 260,600 dalton의 band가 증가하였다. 이러한 결과로 성장 발달에 따라 고분자 량의 물질들이 이들 소뇌 부위에서 기여하였을 것으로 추정할 수 있었다. Immunocytochemistry에 의한 분석에서는 c-raf와 a-raf가 소뇌의 피질주위에서 조롱박 세포(Purkinje cell) 의 세포질 특히 핵 주변부위에서 강하게 검출되었으며 a-raf에 비해 c-raf가 더 강하게 나타났었다. 그리고 그 외에 Nucleus embolifornis의 큰 neuronal cell의 세포질 부위의 나타남을 볼 수 있었다. Immunoblot에 의한 분석에서는 crude와 cytosolic fraction에서 raf protein kinase의 존재를 확인할 수 있었으며, 이상의 결과들을 종합해 보았을 때 소뇌의 정상의 많은 신경세포(neuronal cell)에 raf protein kinase가 분포되어 있으며 이들이 정상의 cell에서 기능을 가질 것으로 추정된다.

• 한국독성학회:학술대회논문집
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• 한국독성학회 2002년도 Molecular and Cellular Response to Toxic Substances
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• pp.136-136
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• 2002

Experiments were carried out to determine the role of Raf-1 kinase in the development of drug resistance and apoptosis induced by paclitaxel. In the present study, paclitaxel sensitivity, Raf-1 activity and MAPKs activation were compared in 2 cell lines: parental human breast cancer cells and its drug resistant variant (MCF-7/Adr) cells.(omitted)

• 한국식품과학회지
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• 제52권4호
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• pp.385-395
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• 2020

This study examined the effect of 3,4-dihydroxytoluene (DHT) on UVB-induced photoaging and determined its molecular mechanisms, using HaCaT human keratinocytes and SKH-1 hairless mice. DHT suppressed UVB-induced matrix metalloproteinase-1 (MMP-1) expression in HaCaT cells. In vivo data from mouse skin supported that DHT decreased UVB-induced wrinkle formation, epidermal thickness, and matrix metalloproteinase-13 (MMP-13) expression. DHT appeared to exert its anti-aging effects by suppressing UVB-induced Raf-1 kinase activity and subsequent attenuation of UVB-induced phosphorylation of MEK, ERK, and p90RSK in HaCaT cells. In vitro and in vivo pull-down assays revealed that DHT bound with Raf-1 in ATP-noncompetitive manner. Overall, DHT appears to anti-photoaging effects in vitro and in vivo through the suppression of Raf-1 kinase activity and may have potential as a treatment for the prevention of skin aging.

• Biomolecules & Therapeutics
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• 제19권2호
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• pp.174-180
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• 2011

Experiments were carried out to determine the role of Raf-1 kinase in the development of drug resistance to paclitaxel in v-H-ras transformed NIH 3T3 fibroblasts (Ras-NIH 3T3). We established a multidrug-resistant cell line (Ras-NIH 3T3/Mdr) from Ras-NIH 3T3 cells by stepwise increases in paclitaxel. Drug sensitivity assays indicated that the $IC_{50}$ value for drug-resistant Ras-NIH 3T3/Mdr cells was more than 1 ${\mu}M$ paclitaxel, 10- or more-fold higher than for the parental Ras-NIH 3T3 cells. Western blot and RT-PCR analysis showed that the drug efflux pump a P-glycoprotein were highly expressed in Ras-NIH 3T3/Mdr cells, while not being detectable in Ras-NIH 3T3 cells. Additionally, verapamil, which appears to inhibit drug efflux by acting as a substrate for P-glycoprotein, completely reversed resistance to paclitaxel in Ras-NIH 3T3/Mdr cell line, indicating that resistance to paclitaxel is associated with overexpression of the multidrug resistance gene. Interestingly, Ras-NIH 3T3/Mdr cells have higher basal Raf-1 activity compared to Ras-NIH 3T3 cells. Unexpectedly, however, the colocalization of Raf-1 and its negative regulator Spry2 was less observed in cytoplasm of Ras-NIH 3T3/Mdr cells due to translocation of Spry2 around the nucleus in the perinuclear zone, implying that Raf-1 may be released from negative feedback inhibition by interacting with Spry2. We also showed that shRNA-mediated knockdown of Raf-1 caused a moderate increase in cell susceptibility to paclitaxel. Thus, the results presented here suggest that a Raf-1-dependent pathway plays an important role in the development of acquired drug-resistance.

• 생명과학회지
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• 제26권1호
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• pp.101-108
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• 2016

본 연구에서는 미만형 위암조직에서의 임상병리학적 인자와 HSP70, BAG1, Raf-1의 발현간의 상관관계를 평가하고자 하였다. Hsp70은 열충격단백질(heat shock protein)의 환경적 스트레스로부터 세포를 보호하는 분자생물학적 chaperone으로 작용하는 것뿐 아니라 anti-apoptotic 작용을 통하여 암세포의 생존과 전이를 촉진시키는 것으로 알려져 있다. Proto-oncogene의 일종인 Raf는 사람을 포함한 진핵세포의 생장에 관여하는 중요한 신호전달경로인 mitogen-activated protein kinase (MAPK)경로의 중심인자로서 다양한 암에서 그 발현이 증가한다고 알려져 있다. Bcl-2에 결합하여 세포사멸을 저해하는 것으로 처음 보고된 Bcl-2-associated athanogene-1 (BAG-1)은 다양한 암에서 그 발현이 증가된다고 보고되었다. 또한 BAG-1은 HSP70과 상호작용하여 Raf-1-ERK signal pathway와 cell growth를 조절하는 것으로 보고되었다. Hsp70의 발현은 임파절 전이가 있는 경우 24례(64.9%)에서 양성, 13례(35.1%)에서 음성을 보였으며, 임파절 전이가 없는 경우 6례(26.1%)에서 양성, 17례(73.9%)에서 음성을 보여 임파절의 전이가 있는 경우가 임파절 전이가 없는 경우에 비해 유의하게 높은 발현율을 보였다(p=0.007). N-stage에 따른 발현은 N-stage가 증가함에 따라 발현율이 유의하게 증가하였다(p=0.006). BAG1의발현은 전체 대상 환자 중 43례(71.7%)에서 양성, 17례(28.3%)에서 음성소견을 보였으며, 65세 미만에서 65세 이상에 비해 유의하게 높은 발현율을 보였다(p=0.035). RAF1의 경우 전체 대상 환자 중 45례(75.0%)에서 양성, 15례(25.0%)에서 음성소견을 보였으며, BAG1 양성환자에서 RAF1의 발현이 유의하게 증가 하였다(p=0.021). 본연구 결과 Hsp70은 종양의 진행과 상관성이 있을 것으로 생각되어지며, BAG1과 Raf-1은 미만형위 암의 진단적 마커로 유용할 것으로 사료된다.