• Journal of Life Science
• /
• v.22 no.3
• /
• pp.428-436
• /
• 2012

Protein phosphorylation is a universal mechanism that regulates cellular activities. The brassinosteroid (BR) signal transduction pathway is a relay of phosphorylation and dephosphorylation cascades. It starts with the BR-induced activation of the membrane receptor kinase brassinosteroid insensitive 1 (BRI1), resulting in the dephosphorylation of transcription factors such as BZR1/BES2 and BZR2/BES1 followed by BR-induced gene expression. Brassinosteroid signal transduction research has progressed rapidly by identifying the phosphorylation/dephosphorylation site(s) of the BR-regulated kinase and phosphatase substrates with a simultaneous pursuit of mutant phenotypes. Autophosphorylation, transphosphorylation, and serine/threonine and tyrosine phosphorylation of the receptor protein kinases BRI1 and BRI1-associated kinase (BAK1) have increased the understanding of the regulatory role of those kinases during physiological and developmental processes in plants. The phosphorylation event initiated by BR is also found in the regulation of receptor-mediated endocytosis and the subsequent degradation of the receptor. However, the basic molecular links of the BR signal transduction pathway are not well understood regarding this phosphorylation/dephosphorylation event. This review summarizes the current state of BR signal transduction research to uncover the phosphorylation/dephosphorylation networks and suggests directions for future research on steroid signal transduction to gain a more comprehensive understanding of the process.

• Molecules and Cells
• /
• v.43 no.1
• /
• pp.66-75
• /
• 2020

Saturated fatty acids contribute to β-cell dysfunction in the onset of type 2 diabetes mellitus. Cellular responses to lipotoxicity include oxidative stress, endoplasmic reticulum (ER) stress, and blockage of autophagy. Palmitate induces ER Ca²⁺ depletion followed by notable store-operated Ca²⁺ entry. Subsequent elevation of cytosolic Ca²⁺ can activate undesirable signaling pathways culminating in cell death. Mitochondrial Ca²⁺ uniporter (MCU) is the major route for Ca²⁺ uptake into the matrix and couples metabolism with insulin secretion. However, it has been unclear whether mitochondrial Ca²⁺ uptake plays a protective role or contributes to lipotoxicity. Here, we observed palmitate upregulated MCU protein expression in a mouse clonal β-cell, MIN6, under normal glucose, but not high glucose medium. Palmitate elevated baseline cytosolic Ca²⁺ concentration ([Ca²⁺]_i) and reduced depolarization-triggered Ca²⁺ influx likely due to the inactivation of voltage-gated Ca²⁺ channels (VGCCs). Targeted reduction of MCU expression using RNA interference abolished mitochondrial superoxide production but exacerbated palmitate-induced [Ca²⁺]_i overload. Consequently, MCU knockdown aggravated blockage of autophagic degradation. In contrast, co-treatment with verapamil, a VGCC inhibitor, prevented palmitate-induced basal [Ca²⁺]_i elevation and defective [Ca²⁺]_i transients. Extracellular Ca²⁺ chelation as well as VGCC inhibitors effectively rescued autophagy defects and cytotoxicity. These observations suggest enhanced mitochondrial Ca²⁺ uptake via MCU upregulation is a mechanism by which pancreatic β-cells are able to alleviate cytosolic Ca²⁺ overload and its detrimental consequences.

• Proceedings of the Plant Resources Society of Korea Conference
• /
• 2019.04a
• /
• pp.111-111
• /
• 2019

Glycyrrhizae radix is one of the most frequently prescribed ingredients in Oriental medicine, and G. radix extract has been shown to exert anti-cancer effects. However, the cellular and molecular mechanisms of apoptosis by G. radix are poorly defined. In the present study, it was examined the biochemical mechanisms of apoptosis by water extract of G. radix (WEGR) in human bladder T24 cancer cells. It was found that WEGR could inhibit the cell growth of T24 cells in a dose-dependent manner, which was associated with the induction of apoptotic cell death, as evidenced by the formation of apoptotic bodies, DNA fragmentation and increased populations of annexin-V positive cells. The induction of apoptotic cell death by WEGR was connected with an up-regulation of pro-apoptotic Bax protein expression and down-regulation of anti-apoptotic Bcl-2 and Bcl-xL proteins, and inhibition of apoptosis family proteins (XIAP, cIAP-1 and cIAP-2). In addition, apoptosis-inducing concentrations of WEGR induced the activation of caspase-9, an initiator caspase of the mitochondrial-mediated intrinsic pathway, and caspase-3, accompanied by proteolytic degradation of poly (ADP-ribose)-polymerase. WEGR also induced apoptosis via a death receptor-mediated extrinsic pathway by caspase-8 activation, resulting in the down-regulation of total Bid and suggesting the existence of cross-talk between the extrinsic and intrinsic pathways. Taken together, the present results suggest that WEGR may be a potential chemotherapeutic agent for the control of human bladder cancer cells.

• Korean Journal of Pharmacognosy
• /
• v.50 no.1
• /
• pp.11-17
• /
• 2019

Cassia tora L. have been used as a folk medicine in Korea. This study investigated anti-inflammatory effect of aurantio-obtusin isolated from C. tora. We isolated aurantio-obtusin from 50% ethanol extracts of C. tora L. We investigated the anti-inflammatory effects of aurantio-obtusin on the lipopolysaccharide (LPS)-stimulated inflammatory response in murine macrophage cell line (Raw 264.7). To investigate the cytotoxicity of aurantio-obtusin on RAW 264.7 cells, MTS assay was performed. RAW 264.7 cells were treated with aurantio-obtusin at different concentrations (12.5, 25, 50, $100{\mu}M$) for 30 h. The result showed that aurantio-obtusin had no cytotoxic effect in a concentration range of $12.5-100{\mu}M$. To determine the effect of aurantio-obtusin on LPS-induced NO production, the NO concentration measurement was performed. RAW 264.7 cells were treated with aurantio-obtusin at 12.5, 25, 50 and $100{\mu}M$ for 24 h, and the results showed that the NO production of aurantio-obtusin-treated cells compared to LPS alone treated group was significantly decreased in a dose-dependent manner. Pretreatment of aurantio-obtusin inhibited LPS-induced NO production in a dose-dependent manner. To find out inhibitory mechanisms of aurantio-obtusin on inflammatory mediators, we examined the $PGE_2$ pathways. As a result, $PGE_2$ were decreased in a dose-dependent manner by aurantio-obtusin. The release of interleukin-$1{\beta}$ (IL-$1{\beta}$) and IL-6 were also reduced. Moreover, aurantio-obtusin suppressed LPL-induced $I{\kappa}B-{\alpha}$ degradation. These results suggest that the down regulation of NO, $PGE_2$, IL-$1{\beta}$ and IL-6 expression by aurantio-obtusin are achieved by the downregulation of NF-${\kappa}B$ activity.

• Journal of Korean Society of Water and Wastewater
• /
• v.35 no.6
• /
• pp.405-415
• /
• 2021

MMBR system has been suggested as a promising system to resolve harvesting problems induced from low settling efficiency of microalgae. And recently, a lot of research on reducing fouling at the MMBR system has investigated focused on EPS in many cases. EPS of microalgae mainly consists of polysaccharides and protein components, and is produced through photosynthesis and nitrogen-carbon metabolic pathways. Especially, P-EPS is one of major compounds which occur membrane fouling phenomenon, as its hydrophobic protein components cause floc formation and cake layer accumulation. And it is already known that almost every microalgae can metabolize P-EPS or Chl-a when nitrogen sources as a substrate is insufficient or exhausted situation. With the above backgrounds, uptake rates of P-EPS or Chl-a by Scenedesmus quadricauda according to the type of carbon source and nitrogen concentration were evaluated in order to verify correlation between carbon source vs P-EPS production, and indeed Scenedesmus quadricauda uses P-EPS or Chl-a when the amounts of nitrogen sourc es in the feed is not satisfied. As a result, it was shown that P-EPS and Chl-a production were increased proportional to nitrogen concentration under organic carbon condition. And especially, the amo unts of P-EPS and Chl-a in the cell were diminished with the nitrogen source becomes insufficient or exhausted. Because P-EPS accelerates fouling at the MMBR system, P-EPS degradation by Scenedesmus quadricauda in order to get nitrogen source may contribute to reducing fouling. About a affects of N-consumed Chl-a to the MMBR fouling, more survey is needed. On the contrary, considering the purpose of MMBR system of this study, i.e. harvesting useful high value microalgae efficiently feeding adequate industrial process wastewater, it seems like difficult to maintain satisfied metabolic activity and to harvest with high yield rate using nitrogen-poor MMBR feed.

• The Korea Journal of Herbology
• /
• v.33 no.2
• /
• pp.19-28
• /
• 2018

Objectives : Epimedii Herba has been frequently used in Korean Traditional Medicine to treat impotence, spermatorrhoea, exophthalmos, and forgetfulness. Present study investigated anti-inflammatory effects of Epimedii Herba water extract (EWE) and attempted to elucidate molecular mechanisms involved. Methods : To explore anti-inflammatory effects of EWE, RAW 264.7 cells, a murine macrophage cell line, were pretreated with $10-100{\mu}g/m{\ell}$ of EWE, and then subsequently exposed to $1{\mu}g/m{\ell}$ of lipopolysaccharide (LPS). Levels of nitric oxide (NO), interleukin-6, $interleukin-1{\beta}$, and tumor necrosis $factor-{\alpha}$ were monitored in the medium. Expression levels of inducible nitric oxide synthase and cyclooxygenase-2 were determined by immunoblot and real-time PCR analyses. Signaling pathways related with nuclear $factor-{\kappa}B$ ($NF-{\kappa}B$) and mitogen-activated protein kinases were monitored to elucidate molecular mechanisms involved. Finally, the role of three flavonoid compounds in EWE on LPS-mediated NO production were investigated. Results : In conditioned medium, pretreatment of EWE ($100{\mu}g/m{\ell}$) significantly inhibited LPS-stimulated NO and pro-inflammatory cytokine production. In addition, EWE attenuated the expressions of inducible nitric oxide synthase and cyclooxygenase-2 by LPS. EWE prevented the phosphorylation and degradation of inhibitory ${\kappa}B{\alpha}$, nuclear translocation of $NF-{\kappa}B$, and DNA binding of $NF-{\kappa}B$, while EWE did not change the phosphorylation of mitogen-activated protein kinases by LPS. Moreover, icariin, icaritin, and quercetin partly, but significantly, inhibited the LPS-stimulated NO production. Conclusions : These results suggest that EWE has an ability to prevent inflammation in macrophages through inhibition of $NF-{\kappa}B$ signaling pathway.

• Journal of Life Science
• /
• v.33 no.6
• /
• pp.523-529
• /
• 2023

Ubiquitination is a post-translational modification that is involved in the quality control of proteins and responsible for modulating a variety of cellular physiological processes. Protein ubiquitination and deubiquitination are reversible processes that regulate the stability of target substrates. The ubiquitin proteasome system (UPS) helps regulate tumor-promoting processes, such as DNA repair, cell cycle, apoptosis, metastasis, and angiogenesis. The UPS comprises a combination of ubiquitin, ubiquitin-activating enzymes (E1), ubiquitin-conjugating enzymes (E2), and ubiquitin-ligase enzymes (E3), which complete the degradation of target proteins. Ubiquitin-conjugating enzymes (UBE2s) play an inter-mediate role in the UPS process by moving activated ubiquitin to target proteins through E3 ligases. UBE2s consist of 40 members and are classified according to conserved catalytic ubiquitin-conjugating (UBC) domain-flanking extensions in humans. Since UBE2s have specificity to substrates like E3 ligase, the significance of UBE2 has been accentuated in tumorigenesis. The dysregulation of multiple E2 enzymes and their critical roles in modulating oncogenic signaling pathways have been reported in several types of cancer. The elevation of UBE2 expression is correlated with a worse prognosis in cancer patients. In this review, we summarize the basic functions and regulatory mechanisms of UBE2s and suggest the possibility of their use as therapeutic targets for cancer.

• Nutrition Research and Practice
• /
• v.17 no.5
• /
• pp.899-916
• /
• 2023

BACKGROUND/OBJECTIVES: Oxidative stress is a fundamental neurodegenerative disease trigger that damages and decimates nerve cells. Neurodegenerative diseases are chronic central nervous system disorders that progress and result from neuronal degradation and loss. Recent studies have extensively focused on neurodegenerative disease treatment and prevention using dietary compounds. Heseperetin is an aglycone hesperidin form with various physiological activities, such as anti-inflammation, antioxidant, and antitumor. However, few studies have considered hesperetin's neuroprotective effects and mechanisms; thus, our study investigated this in hydrogen peroxide (H₂O₂)-treated SH-SY5Y cells. MATERIALS/METHODS: SH-SY5Y cells were treated with H₂O₂ (400 µM) in hesperetin absence or presence (10-40 µM) for 24 h. Three-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assays detected cell viability, and 4',6-diamidino-2-phenylindole staining allowed us to observe nuclear morphology changes such as chromatin condensation and apoptotic nuclei. Reactive oxygen species (ROS) detection assays measured intracellular ROS production; Griess reaction assays assessed nitric oxide (NO) production. Western blotting and quantitative polymerase chain reactions quantified corresponding mRNA and proteins. RESULTS: Subsequent experiments utilized various non-toxic hesperetin concentrations, establishing that hesperetin notably decreased intracellular ROS and NO production in H₂O₂-treated SH-SY5Y cells (P < 0.05). Furthermore, hesperetin inhibited H₂O₂-induced inflammation-related gene expression, including interluekin-6, tumor necrosis factor-α, and nuclear factor kappa B (NF-κB) p65 activation. In addition, hesperetin inhibited NF-κB translocation into H₂O₂-treated SH-SY5Y cell nuclei and suppressed mitogen-activated protein kinase protein expression, an essential apoptotic cell death regulator. Various apoptosis hallmarks, including shrinkage and nuclear condensation in H₂O₂-treated cells, were suppressed dose-dependently. Additionally, hesperetin treatment down-regulated Bax/Bcl-2 expression ratios and activated AMP-activated protein kinase-mammalian target of rapamycin autophagy pathways. CONCLUSION: These results substantiate that hesperetin activates autophagy and inhibits apoptosis and inflammation. Hesperetin is a potentially potent dietary agent that reduces neurodegenerative disease onset, progression, and prevention.

• Journal of Life Science
• /
• v.20 no.12
• /
• pp.1772-1776
• /
• 2010

Transcription factors Nrf2 and NF-${\kappa}B$ are important regulators of the innate immune response, and their cross-talks in inflammation have been reported. Previously, we demonstrated that gold(I)-compound auranofin, an inhibitor of NF-${\kappa}B$ signal, induced Nrf2 activation in human synovial cells and monocytic cells. To investigate whether the Nrf2 activation is involved in the mechanism of the auranofin-attenuated NF-${\kappa}B$ signaling, we examined the effects of Nrf2 knockdown on NF-${\kappa}B$ activation using rheumatic synovial cells. When the cells were transfected with a specific siRNA for Nrf2, the gene expression was perfectly blocked. However, the Nrf2 knockdown did not cancel the suppressive effect of auranofin on TNF-$\alpha$-induced $I{\kappa}B-{\alpha}$ degradation. Treatment with a specific siRNA for HO-1, which is a target of Nrf2 and plays a role in anti-inflammation, also did not affect the blocking activity of auranofin on $I{\kappa}B-{\alpha}$ degradation. In addition, auranofin-inhibited ICAM-1 expression was not restored by Nrf2 knockdown. These findings indicate that the activated Nrf2 and HO-1 are not associated with the suppressive action of auranofin on the pro-inflammatory cytokines-stimulated NF-${\kappa}B$ activation. This suggests that Nrf2/HO-1 and NF-${\kappa}B$ signals, which are regulated by auranofin, participate in the anti-inflammatory action of auranofin via independent pathways in rheumatic synovial cells.

• Radiation Oncology Journal
• /
• v.20 no.4
• /
• pp.367-374
• /
• 2002

Purpose : To investigate the growth inhibitory effects, and the underlying mechanism of human colon cancer cell (HT-29) death, induced by a new synthetic bile acid derivative (HS-1200). Materials and Methods : Human colon cancer cells (HT-29), in exponential growth phase, were treated with various concentrations of a new synthetic bile acid derivative (HS-1200). The growth inhibitory effects on HT-29 cells were examined using a frypan blue exclusion assay. The extent of apoptosis was determined using agarose gel electrophoresis, TUNEL assays and Hoechst staining. The apoptotic cell death was also confirmed by Western blotting of PARP, caspase-3 and DNA fragmentation factor (DFF) analysis. To investigate the involvement of mitochondria, we employed immunofluorescent staining of cytochrome c and mitochondrial membrane potential analyses. Results : The dose required for the half maximal inhibition $(IC_{50})$ of the HT-29 cell growth was $100\~150\;{\mu}M$ of HS-1200. Several changes, associated with the apoptosis of the HT-29 cells, were reveal by the agarose gel eletrophoresis, TUNEL assays and Hoechst staining, following their treatment with $100\;{\mu}M$ of HS-1200. HS-1200 treatment also induced caspase-3, PARP and DFF degradations, and the western blotting showed the processed caspase-3 p20, PARP p85 and DFF p30 and p11 cleaved products. Mitochondrial events were also demonstrated. The cytochrome c staining indicated that cytochrome c had been released from the mitochondria in the HS-1200 treated cells. The mitochondrial membrane potential $(\Delta\Psi_m)$ was also prominently decreased in the HS-1200 treated cells. Conclusion : These findings suggest that the HS-1200 - induced apoptosis of human colon cancer cells (HT-29) is mediated via caspase and mitochondrial pathways.