• Archives of Pharmacal Research
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• v.21 no.6
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• pp.629-633
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• 1998

In addition to selecting proteins for degradation by the 26S proteasome, ubiqitination appears to serve other regulatory functions, including for endosomal/lysosomal targeting, protein translocation, and enzyme modification. Currently, little is known how multiubiquitin chains are recognized by these cellular mechanisms. Within the 26S proteasome, one subunit (Mcb1/S5a) has been identified that has affinity for multiubiquitin chains and may function as a ubiquitin receptor. We recently found that a non-proteasomal protein p62 also preferentially binds multiubiquitin chains and forms a novel cytoplasmic structure "sequestosome" which serves as a storage place for ubiquitinated proteins. In the present manuscript, the role and regulation of p62 in relation to the sequestosomal function will be reviewed.

• Journal of Life Science
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• v.24 no.8
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• pp.895-902
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• 2014

Adiponectin has been known to improve insulin sensitivity and elicit glucose uptake via increased glucose transporter 4 (GLUT4) translocation. In the current study, mRNA expression levels of adiponectin and GLUT4 were measured in subcutaneous adipose tissue from C57BL/6 mice fed normal (ND) or high-fat diet (HFD) until 16, 26, 36, 47, or 77 weeks of age starting from 6 weeks of age. Expression levels were also measured in mice with calorie restriction (CR) and in thiazolidinedione (TZD) treated mice. Using quantitative real-time PCR, we demonstrated that GLUT4 expression in adipose tissue significantly decreased in HFD mice groups and increased in CR (p<0.05) and TZD (p=0.007) groups while there was no difference in adiponectin mRNA expression levels between experimental and control groups. General linear regression models were used to assess the association of gene expression levels between adiponectin and GLUT4 and to determine whether adiponectin affects GLUT4 transcription. mRNA expression levels of adiponectin and GLUT4 are significantly associated each other in mice fed a ND (p<0.0001) or HFD (p<0.0001), in groups separated into each age and diet, and CR group (p=0.002), but not in TZD group (p=0.73). These results demonstrated that gene expression of adiponectin and GLUT4 is strongly associated, suggesting that there is a common regulatory mechanism for adiponectin and GLUT4 gene expression and/or adiponectin has a direct role in GLUT4 gene expression in adipose tissue.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.2
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• pp.221-234
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• 2019

Cancer is genetically, metabolically and infectiously induced life threatening disorder showing aggressive growing pattern with invasive tendency. In order to prevent this global menace from jeopardizing human life, enormous studies on carcinogenesis and treatment for chemotherapy resistance have been intensively researched. Hinokitiol (${\beta}$-thujaplicin) extracted from heart wood of cupressaceous is a well-known bioactive compound demonstrating anti-inflammation, anti-bacteria and anti-cancer effects on several cancer types via apoptosis and autophagy. This study proposed that hinokitiol activates transcription factor EB (TFEB) nuclear translocation for autophagy and lysosomal biogenesis regardless of nutrient condition in cancer cells. Mitophagy and ${\beta}$-catenin translocation into the nucleus under treatment of hinokitiol on non-small cell lung cancer (NSCLC) cells and HeLa cells were investigated. Hinokitiol exerted cytotoxicity on HeLa and HCC827 cells; moreover, artificially induced autophagy by overexpression of TFEB granted imperfect sustainability onto HeLa cells. Taken together, hinokitiol is the prominent autophagy inducer and activator of TFEB nuclear translocation. Alternative cancer therapy via autophagy is pros and cons since the autophagy in cancer cells is related to prevention and survival mechanism depending on nutrition. To avoid paradox of autophagy in cancer therapy, fine-tuned regulation and application of hinokitiol in due course for successful suppressing cancer cells are recommended.

• Journal of Microbiology and Biotechnology
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• v.29 no.5
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• pp.704-712
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• 2019

Although nanometric dead Lactobacillus plantarum has emerged as a potentially important modulator of immune responses, its underlying mechanism of action has not been fully understood. This study aimed to identify the detailed biochemical mechanism of immune modulation by micronized and heat-treated L. plantarum LM1004 (MHT-LM1004, <$1{\mu}m$ in size). MHT-LM1004 was prepared from L. plantarum LM1004 via culture in a specifically designed membrane bioreactor and heat treatment. MHT-LM1004 was shown to effectively induce the secretion of $TNF-{\alpha}$ and IL-6 and the mRNA expression of inducible nitric oxide synthase (iNOS). MHT-LM1004 enhanced the expression of TLR-2, phosphorylation of MAPKs (ERK), and nuclear translocation of $NF-{\kappa}B$ in a dose-dependent manner. Oral administration of MHT-LM1004 ($4{\times}10^9$ or $4{\times}10^{11}cells/kg$ mouse body weight) increased the splenocyte proliferation and serum cytokine levels. These results suggested that MHT-LM1004 effectively enhances early innate immunity by activating macrophages via the TLR-2/MAPK/$NF-{\kappa}B$ signalling pathway and that this pathway is one of the major routes in immune modulation by the Lactobacillus species.

• Korean Journal of Plant Tissue Culture
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• v.27 no.5
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• pp.407-409
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• 2000

Outer envelope membrane proteins of chloroplasts encoded by the nuclear genome are transported without the N-terminal transit peptide. Here, we investigated the targeting mechanism of AtOEP7, an Arabidopsis homolog of small outer envelope membrane proteins in vivo. AtOEP7 was expressed transiently in protoplasts or stably in transgenic plants as fusion proteins with GFP. In both cases AtOEP7:GFP was targeted to the outer envelope membrane when assayed under a fluorescent microscope or by Western blot analysis. Except the transmembrane domain, deletions of the N- or C-terminal regions of AtOEP7 did not affect targeting although a region closed to the C-terminal side of the transmembrane domain affected the targeting efficiency. Targeting experiments with various hybrid transmembrane mutants revealed that the amino acid sequence of the transmembrane domain determines the targeting specificity The targeting mechanism was further studied using a fusion protein, AtOEP7：NLS：GFP, that had a nuclear localization signal. AtOEP7：NLS：GFP was efficiently targeted to the chloroplast envelope despite the presence of the nuclear localization signal. Taken together, these results suggest that the transmembrane domain of AtOEP7 functions as the sole determinant of targeting specificity and that AtOEP7 may be associated with a cytosolic component during translocation to the chloroplast envelope membrane.

• The Korean Journal of Physiology
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• v.24 no.2
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• pp.331-344
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• 1990

What makes glucose transport function sensitive to insulin in one cell type such as adipocyte, and insensitive in another such as liver cells is unresolved question at this time. Recently it is known that insulin stimulates glucose transport in adipocytes largely by redistributing transporter from the storage pool that is included in a low density microsomal fraction to plasma membrane. Therefore, insulin sensitivity may depend upon the relative distribution of gluscose transporters between the plasma membrane and in an intracellular storage compartment. In hepatocytes, the subcellular distribution of glucose transporter is less well documented. It is thus possible that the apparent insensitivity of the hepatocyte system could be either due to lack of the constitutively maintained, intracellular storage pool of glucose transporter or lack of insulin-mediated transporter translocation mechanism in this cell. In this study, I examined if any intracellular glucose transporter pool exists in hepatocytes and this pool is affected by insulin. The results obtained summarized as followings: 1) Distribution of subcellular fractions of hepatocyte showed that there are $24.9{\pm}1.3%$ of plasma membrane, $36.9{\pm}1.7%$ of nucleus-mitochondria enriched fraction, $23.5{\pm}1.2%$ of lysosomal fraction, $9.6{\pm}1.0%$ of high density microsomal fraction and $4.9{\pm}0.5%$ of low density microsomal fraction. 2) In adipocyte, there were $29.9{\pm}2.6%$ of plasma membrane, $19.4{\pm}1.9%$ of nucleus-mitochondria enriched fraction, $26.7{\pm}1.8%$ of high density microsomal fraction and $23.9{\pm}2.1%$ of low density microsomal fraction. 3) Surface labelling of sodium borohydride revealed that plasma membrane contaminated to lysosomal fraction by $26.8{\pm}2.8%$, high density microsomal fraction by $8.3{\pm}1.3%$ and low density microsomal fraction by $1.7{\pm}0.4%$ respectively. 4) Cytochalasin B bound to all of subcellular fractions with a Kd of $1.0{\times}10^{-6}M$. 5) Photolabelling of cytochalasin B to subcellular fractions occurred on 45 K dalton protein band, a putative glucose transporter and D-glucose inhibited the photolabelling. 6) Insulin didn't affect on the distribution of subcellular fractions and translocation of intracellular glucose transporters of hepatocytes. 7) HEGT reconstituted into hepatocytes was largely associated with plasma membrane and very little was found in low density microsomal fraction which equals to the native glucose transporter distribution. Insulin didn't affect on the distribution of exogeneous glucose transporter in hepatocytes. From the above results it is concluded that insulin insensitivity of hepatocyte may due to lack of intracellular storage pool of glucose transporter and thus intracellular storage pool of glucose transporter is an essential feature of the insulin action.

• Journal of Ginseng Research
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• v.46 no.2
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• pp.266-274
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• 2022

Colon cancer, the third most frequent occurred cancer, has high mortality and extremely poor prognosis. Ginsenoside, the active components of traditional Chinese herbal medicine Panax ginseng, exerts antitumor effect in various cancers, including colon cancer. However, the detailed molecular mechanism of Ginsenoside in the tumor suppression have not been fully elucidated. Here, we chose the representative ginsenoside Rg3 and reported for the first time that Rg3 induces mitophagy in human colon cancer cells, which is responsible for its anticancer effect. Rg3 treatment leads to mitochondria damage and the formation of mitophagosome; when autophagy is inhibited, the clearance of damaged mitochondria can be reversed. Next, our results showed that Rg3 treatment activates the PINK1-Parkin signaling pathway and recruits Parkin and ubiquitin proteins to mitochondria to induce mitophagy. GO analysis of Parkin targets showed that Parkin interacts with a large number of mitochondrial proteins and regulates the molecular function of mitochondria. The cellular energy metabolism enzyme GAPDH is validated as a novel substrate of Parkin, which is ubiquitinated by Parkin. Moreover, GAPDH participates in the Rg3-induced mitophagy and regulates the translocation of Parkin to mitochondria. Functionally, Rg3 exerts the inhibitory effect through regulating the nonglycolytic activity of GAPDH, which could be associated with the cellular oxidative stress. Thus, our results revealed GAPDH ubiquitination by Parkin as a crucial mechanism for mitophagy induction that contributes to the tumor-suppressive function of ginsenoside, which could be a novel treatment strategy for colon cancer.

• Environmental Analysis Health and Toxicology
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• v.22 no.3
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• pp.279-285
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• 2007

The present study attempted to analyze the mechanism of PCB-induced neurotoxicity with respect to the PKC signaling. Since the developing neuron is particularly sensitive to PCB-induced neurotoxicity, we isolated cerebellar granule cells derived from 7-day old SD rats and grew cells in culture for additional 7 days to mimic PND-14 conditions. Only non-coplanar PCBs at a high dose showed a significant increase of total PKC activity at $[^3H]PDBu$ binding assay, indicating that non-coplanar PCBs are more neuroactive than coplanar PCBs in neuronal cells. PKC isoforms were immunoblotted with respective monoclonal antibodies. PKC-alpha and-epsilon were activated with non-coplanar PCB exposure. The result suggests that coplanar PCBs have a PKC pathway different from non-coplanar PCBs. Activation of PKC with exposure was dampened with treatment of high molecular weight of chitosan. Chilean (M.W. > 1,000 kDa) inhibited the total activity of PKC induced by the non-coplanar PCBs. Translocation of PKC isoforms was also inhibited by the high molecular weight of chitosan. The study demonstrated that non-coplanar PCBs are more potent neurotoxic congeners than coplanar PCBs and the alteration of PKC activities by PCB exposure can be blocked with the treatment of chitosan. The results suggest a potential use of chitosan as a means of nutritional intervention to prevent the harmful effects of pollutant-derived diseases.

• CELLMED
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• v.4 no.4
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• pp.27.1-27.5
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• 2014

Picrorhiza kurroa Royle ex Benth. (Scrophulariaceae) is a traditional Ayurvedic herb known as Kutki. It is used as a remedy for diabetes by tribes of North Eastern Himalayan region of India. Present study was conducted to explore the mechanism of antidiabetic activity of standardized aqueous extract of Picrorhiza kurroa (PkE). PkE (100 and 200 mg/kg/day) was orally administered to streptozotocin induced diabetic rats, for 14 consecutive days. Plasma insulin levels were measured and pancreas of rat was subjected to histopathological investigations. Glucose transporter type 4 (GLUT-4) protein content in the total membrane fractions of soleus muscle was estimated by Western blot analysis. Plasma insulin level was significantly increased along with concomitant increase in GLUT-4 content of total membrane fractions of soleus muscle of diabetic rats treated with extract. There was evidence of regeneration of ${\beta}$-cells of pancreatic islets of PkE treated group in histopathological examinations. PkE increased the insulin-mediated translocation of GLUT-4 from cytosol to plasma membrane or increased GLUT-4 expression, which in turn facilitated glucose uptake by skeletal muscles in diabetic rats.

• The Korean Journal of Physiology and Pharmacology
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• v.8 no.5
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• pp.237-243
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• 2004

Glial cells are activated in neuropathy and play a key role in hyperalgesia and allodynia. This study was performed to determine whether minocycline could attenuate heat hyperalgesia and mechanical allodynia, and how glial cell activation and nuclear factor kappa B (NF-kappaB) were regulated by minocycline in a model of chronic constriction of sciatic nerve (CCl). When minocycline (50 mg/kg, oral) was daily administered from 1 day before to 9 days after ligation, heat hyperalgesia and mechanical allodynia were attenuated. Furthermore, when minocycline treatment was initiated 1 or 3 days after ligation, attenuation of the hypersensitive behavior was still robust. However, the effect of attenuation was less when minocycline was started from day 5. In order to elucidate the mechanism of pain attenuation by minocycline, we examined the changes of glia and NF-kappaB, and found that attenuated hyperalgesia and allodynia by minocycline was accompanied by reduced microglial activation. Furthermore, the number of NF-kappaB immunoreactive cells increased after CCI treatment and this increase was attenuated by minocycline. We also observed translocation of NF-kappaB into the nuclei of activated glial cells. These results suggest that minocycline inhibits activation of glial cells and NF-kappaB, thereby attenuating the development of behavioral hypersensitivity to stimuli.