• Mycobiology
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• 제41권3호
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• pp.145-148
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• 2013

Vegetative growth signaling of the opportunistic human pathogenic fungus Aspergillus fumigatus is mediated by GpaA ($G{\alpha}$). FlbA is a regulator of G protein signaling, which attenuates GpaA-mediated growth signaling in this fungus. The flbA deletion (${\Delta}flbA$) and the constitutively active GpaA ($GpaA^{Q204L}$) mutants exhibit enhanced proliferation, precocious autolysis, and reduced asexual sporulation. In this study, we demonstrate that both mutants also show enhanced tolerance against $H_2O_2$ and their radial growth was approximately 1.6 fold higher than that of wild type (WT) in medium with 10 mM $H_2O_2$. We performed quantitative PCR (qRT-PCR) for examination of mRNA levels of three catalase encoding genes (catA, cat1, and cat2) in WT and the two mutants. According to the results, while levels of spore-specific catA mRNA were comparable among the three strains, cat1 and cat2 mRNA levels were significantly higher in the two mutants than in WT. In particular, the ${\Delta}flbA$ mutant showed significantly enhanced and prolonged expression of cat1 and precocious expression of cat2. In accordance with this result, activity of the Cat1 protein in the ${\Delta}flbA$ mutant was higher than that of $gpaA^{Q204L}$ and WT strains. For activity of the Cat2 protein, both mutants began to show enhanced activity at 48 and 72 hr of growth compared to WT. These results lead to the conclusion that GpaA activates expression and activity of cat1 and cat2, whereas FlbA plays an antagonistic role in control of catalases, leading to balanced responses to neutralizing the toxicity of reactive oxygen species.

• Journal of Radiation Protection and Research
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• 제40권3호
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• pp.187-193
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• 2015

Deleterious effects of high dose radiation exposure with high-dose-rate are unarguable, but they are still controversial in low-dose-rate. The regulator of G-protein signaling (RGS) is a negative regulator of G protein-coupled receptor (GPCR) signaling. In addition, it is reported that irradiation stress led to GPCR-mediated mitogen-activated protein kinase (MAPK) and phosphotidylinositol 3-kinase (PI3-k) signaling. The RGS mRNA expression profiles by whole body radiation with low-dose-rate has not yet been explored. In the present study, we, therefore, examined which RGS was modulated by the whole body radiation with low-dose-rate ($3.49mGy{\cdot}h^{-1}$). Among 16 RGS expression tested, RGS6, RGS13 and RGS16 mRNA were down-regulated by low-dose-rate irradiation. This is the first report that whole body radiation with low-dose-rate can modulate the different RGS expression levels. These results are expected to reveal the potential target and/or the biomarker proteins associated with male testis toxicity induced by low-dose-rate irradiation, which might contribute to understanding the mechanism beyond the testis toxicity.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2019년도 춘계학술대회
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• pp.33-33
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• 2019

The AKT signaling pathway is a highly regulated cell signaling system that forms a network with other cell signaling pathways. Hence, the AKT signaling pathway mediates several important cellular functions that include cell survival, proliferation, cell migration, and et cetera. Irregularities that led overactive AKT signaling have been linked to many diseases such as cancer and metabolic-associated diseases. Hence, modulating the overactive AKT signaling pathway via inhibitor is a tantalizing prospect for treatment of cancer and metabolic-associated diseases. Two inhibitors of the AKT signaling pathway will be presented in this symposium: 1) Bisleuconothine A (BisA), a bisindole alkaloid that inhibit autophagy and 2) Ceramicine B (CerB), a limonoid that inhibit adipogenesis. The first topic is on a bisindole alkaloid, BisA and its mechanism in inducing autophagosome formation in lung cancer cell line, A549.(1) Since most autophagy inducing agents generally induce apoptosis, we found that BisA does not induce apoptosis even in high dose. BisA up-regulation of LC3 lipidation is achieved through mTOR inactivation. The phosphorylation of PRAS40, a mTOR repressor was suppressed by BisA. This observation suggested that BisA inactivates mTOR via suppression of PRAS40 phosphorylation. Interestingly, the phosphorylation of AKT, an upstream regulator of PRAS40 phosphorylation was also down-regulated by BisA. These findings suggested that Bis-A induces autophagosomes formation by interfering with the AKT-mTOR signaling pathway. The second topic is on CerB and its mechanism in inhibiting adipogenesis in preadipocytes cell line, MC3T3-G2/PA6.(2,3) CerB inhibits the phosphorylation of protein kinase B (AKT) at the Thr308 position but not the Ser473. Consequently, the phosphorylation of FOXO3 which is located downstream of AKT is also inhibited. Considering that FOXO3 is an important regulator of PPARγ which is a key factor in adipogenesis, CerB may inhibit adipogenesis via the AKT-FOXO3 signaling pathway. Taken together, both BisA and CerB highlighted the potential of AKT signaling pathway modulation as an approach to induce autophagy and inhibit the formation of fat cells, respectively.

• 생명과학회지
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• 제19권11호
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• pp.1506-1513
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• 2009

RGS단백질은 G 단백질 신호전달작용에 있어서 신호를 억제하는 조절단백질로서 G 단백질 매개수용체(GPCR)의 활성을 억제하는 것으로 알려졌다. 그렇지만 캐너비노이드 수용체 CB2의 활성에 있어서 RGS 단백질의 조절효과에 관해서는 지금까지 알려져 있지 않다. 그러므로 본 연구에서 우리는 RGS2, 3, 4, 5와 캐너비노이드 수용체 CB2 cDNA를 동시에 HEK293 세포주에 발현시킨 후 각 RGS 단백질의 효과를 조사하였다. CB2 단백질을 발현하는 HEK293 세포주(CB2-HEK293)에서 CB2 효현제인 WIN55,212-2는 폴스콜린으로 유도된 cAMP response element (CRE) 활성을 억제하였다. 이러한 WIN55,212-2의 CRE 억제 활성은 RGS3에 의하여 차단되었지만 RGS2, 4, 및 RGS5에서는 관찰되지 않았다. 뿐만 아니라 RGS3 small interference RNA (siRNA)를 사용하여 내인성 RGS3 단백질의 발현을 저하시키면 WIN55,212-2에 의한 폴스콜린 유도 CRE 억제활성은 더욱 증강되었다. 이상의 결과는 캐너비노이드 수용체 CB2 신호전달작용에 있어서 RGS 단백질의 기능적 역할과 특히 내인성 RGS3의 캐너비노이드 수용체 CB2에 대한 선택적 작용을 나타낸다.

• BMB Reports
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• 제47권12호
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• pp.685-690
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• 2014

The Ras/Raf/MEK/Erk signaling pathway is important for regulation of cell growth, proliferation, differentiation, survival, and apoptosis in response to a variety of extracellular stimuli. Lack of Erk MAPK activation is observed in several cancer cells despite active activation of Ras. However, little is known about the modulation of Erk1/2 activity by active Ras. Here, we show that overexpression of active H-Ras (H-RasG12R) in NIH3T3 fibroblasts impaired FGF2-induced Erk1/2 phosphorylation, as compared to wild-type cells. Northern blot analysis revealed that prolonged expression of active Ras increased MAP kinase phosphatase 3 (MKP3) mRNA expression, a negative regulator of Erk MAPK. Inhibition of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway abrogated active Ras-induced up-regulation of MKP3 expression, leading to the rescue of Erk1/2 phosphorylation. Our results demonstrated that the Ras/Raf/MEK/Erk signaling cascade is negatively regulated by the PI3K/Aktdependent transcriptional activation of the MKP3 gene.

• Natural Product Sciences
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• 제16권4호
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• pp.239-244
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• 2010

Protein tyrosine phosphatase 1B (PTP1B), a negative regulator of insulin signaling, has served as a potential drug target for the treatment of type 2 diabetes. The MeOH extracts of twenty-nine medicinal plants, traditionally used in Vietnam as anti-diabetes agents, were investigated for PTP1B inhibitory activity in vitro. The results indicated that, most materials showed moderate to strong inhibitory activity with $IC_{50}$ values ranging from $3.4\;{\mu}g/mL$ to $35.1\;{\mu}g/mL$; meanwhile, eleven extracts (37.9%) could demonstrate PTP1B activity with $IC_{50}$ values less than $15.5\;{\mu}g/mL$; sixteen extracts (55.2%) could demonstrate PTP1B activity with $IC_{50}$ values ranging from $15.5\;{\mu}g/mL$ to $35.1\;{\mu}g/mL$. The study may provide a proof, at least in a part, for the ethno-medical use in diabetes disease of these plants.

• 대한의생명과학회지
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• 제12권3호
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• pp.131-137
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• 2006

RGS is a negative regulator of G-protein signaling and can be identified by the presence of a conserved $120{sim}125$ amino acid motif, which is referred to as the RGS box. A number of RGSs are induced in response to a wide variety of stimuli. Increased levels of RGSs lead to significant decreases in GPCR responsiveness. To obtain further evidence of a role of RGS proteins in rat C6 astrocytoma cells, we first determined the expression profile of RGS-specific mRNA in C6 cells using reverse transcription-polymerase chain reaction (RT-PCR) with a poly dT18 primer and transcript-specific primers. We found that RGS2, RGS3, RGS6, RGS9, RGS10, RGS12, and RGS16 were differentially expressed in C6 astrocytoma cells. The highest expression rate was found for RGS3, followed by RGS16, RGS10 and RGS9, whereas the expression level for RGS2 was barely detectable. We next assessed whether forskolin regulated the expression of RGSs expressed in C6 astrocytoma cells. The present study found that forskolin dose-dependently stimulated the expression of RGS2 transcripts. This up-regulation of RGS2 gene was abrogated by H-89, potent and broad-spectrum protein kinase A (PKA) inhibitors. Actinomycin D completely inhibited the up-regulation of RGS2 gene induced by forskolin $(10{\mu}M)$, indicating that the regulation of RGS2 gene is controlled at the transcriptional level. In addition, forskolin did significantly activate transcriptional cAMP response element (CRE) in either HEK 293 cells or C6 cells and did not modulate the $NF-{\kappa}B$ and AP-l activity as measured by luciferase reporter gene assay. Finally, forskolin induced the expression of RGS2 mRNA in C6 astrocytoma cells, which depend on the PKA pathway and CRE transcriptional pathways.

• 생명과학회지
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• 제29권5호
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• pp.514-523
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• 2019

인삼(Panax ginseng C. A. Meyer)의 사포닌 진세노사이드 Rb1이 처리된 인간 피부각질세포 HaCaT에서 microarray 분석 및 발현이 증가된 세포사멸 반응에 대한 작용기전을 연구하였다. HaCaT 세포에 진세노사이드 Rb1의 처리로 세포사멸, 유사분열 세포주기의 G2/M 전이, 세포분열, 핵분열, 그리고 단백질 수송 등의 작용기전에 관여하는 유전자들이 2 배 이상 발현이 증가된 것으로 나타났으며, DNA 수선, 감수 핵분열, 그리고 세포외기질 체계 등의 작용기전에 관여하는 유전자들은 2 배 이상 발현이 감소된 것으로 나타났다. 특히 세포사멸 신호전달은 FAS와 PLA2G4A를 경유하는 것으로 나타났으며, 이들 유전자의 상위 조절자로 STAT3가 예측되었다. 세포사멸 반응 경유 유전자 FAS와 PLA2G4A의 활성을 qPCR로 확인한 결과, FAS 유전자는 $10{\mu}g/ml$의 진세노사이드 Rb1를 24시간 동안 처리하였을 경우 약 2 배의 발현 증가와, PLA2G4A 유전자는 6시간 처리부터 약 2 배로 증가되어 24시간 동안 처리시 2 배 이상의 유전자 발현이 증가되었다. 한편 STAT3-siRNA를 이용한 knock-down 실험에서 FAS의 발현 감소와 PLA2G4A의 발현 증가로 상위 조절자 STAT3로부터 FAS 만을 경유하는 것을 알 수 있었다. 이상의 결과 진세노사이드 Rb1의 처리에 의해 상위 조절자인 STAT3는 FAS를 경유하여 세포사멸을 유도하는 것임을 알 수 있다.

• 한국환경성돌연변이발암원학회지
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• 제25권3호
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• pp.87-96
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• 2005

[ $p16^{INK4a}$ ] is a tumor suppressor that belongs to the INK4 family of the cyclin D-dependent kinases (cdk) inhibitors. It plays regulatory roles in cell proliferation and in tumorigenesis by interacting with Rb signaling. Abnormally elevated $p16^{INK4a}$ protein expression causes cell cycle arrest (G1/S transition) and loss of cyclin-cdk activity. In many cancers, $p16^{INK4a}$ is altered by mutation, deletion, and promoter methylation. This review summarizes the function of p16 as an important regulator of cancer pathobiology and a promising target fer developing cancer therapeutic and chemopreventive agents.

• 한국발생생물학회지:발생과생식
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• 제26권3호
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• pp.107-115
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• 2022

Kisspeptins, products of KISS1 gene, are ligands of the G-protein coupled receptor (GPR54), and the kisspeptin-GPR54 signaling has an important role as an upstream regulator of gonadotropin releasing hormone (GnRH) neurons. Interestingly, extrahypothalamic expressions of kisspeptin/GPR-54 in gonads have been found in primates and experimental rodents such as rats and mice. Hamsters, another potent experimental rodent, also have a kisspeptin-GPR54 system in their ovaries. The presence of testicular kisspeptin-GPR54 system, however, remains to be solved. The present study was undertaken to determine whether the kisspeptin is expressed in hamster testis. To do this, reverse transcription-polymerase chain reactions (RT-PCRs) and immunohistochemistry (IHC) were employed. After the nest PCR, two cDNA products (320 and 280 bp, respectively) were detected by 3% agarose gel electrophoresis, and sequencing analysis revealed that the 320 bp product was correctly amplified from hamster kisspeptin cDNA. Modest immunoreactive (IR) kisspeptins were detected in Leydig-interstitial cells, and the weak signals were detected in germ cells, mostly in round spermatids and residual bodies of elongated spermatids. In the present study, we found the kisspeptin expression in the testis of Syrian hamster. Further studies on the local role(s) of testicular kisspeptin are expected for a better understanding the physiology of hamster testis, including photoperiodic gonadal regression specifically occurred in hamster gonads.