• Journal of Life Science
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• v.27 no.12
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• pp.1479-1485
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• 2017

Muscle atrophy due to aging, starvation, and various chronic diseases leads to a decrease in muscle fiber area and density due to reduced muscle protein synthesis and increased protein breakdown. This study investigated the effect of dexamethasone and hydrogen peroxide on the induction of muscle atrophy and expression of atrophy-related genes in differentiated C2C12 myotubes. C2C12 myoblasts were differentiated into myotubes in differentiation medium. During myoblast differentiation, muscle-specific transcription factors, such as myogenin, and MyoD expression increased. Differentiated C2C12 myotubes exposed to noncytotoxic levels of dexamethasone and hydrogen peroxide showed a decrease in myotube diameter, which was associated with up-regulation of muscle-specific ubiquitin ligases, such as muscle atrophy F-box (MAFbx)/atrogin-1 and muscle RING finger-1 (MuRF1), and down-regulation of myogenin and MyoD. These results demonstrated that dexamethasone and hydrogen peroxide induced atrophy through regulation of muscle-specific ubiquitin ligases and muscle-specific transcription factors in C2C12 myotubes. In this study, we confirmed the process of differentiation of C2C12 myoblasts into myotubes in in vitro experiments in the presence of atrophy. This muscle atrophy model of C2C12 cells induced by dexamethasone or hydrogen peroxide seems suited to studies of the mechanism of muscle atrophy suppression and to exploit the experiment for excavating new muscle atrophy.

• Molecules and Cells
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• v.21 no.2
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• pp.206-212
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• 2006

We have established in culture a spontaneously immortalized bovine embryonic fibroblast (BEF) cell line that has lost p53 and $p16^{INK4a}$ functions. MyoD is a muscle-specific regulator capable of inducing myogenesis in a number of cell types. When the BEF cells were transduced with MyoD they differentiated efficiently to desmin-positive myofibers in the presence of 2% horse serum and 1.7 nM insulin. The myogenic differentiation of this cell line was more rapid and obvious than that of C2C12 cells, as judged by morphological changes and expression of various muscle regulatory factors. To confirm that lack of the p53 and $p16^{INK4a}$ pathway does not prevent MyoD-mediated myogenesis, we established a cell line transformed with SV40LT (BEFV) and introduced MyoD into it. In the presence of 2% horse serum and 1.7 nM insulin, the MyoD-transduced BEFV cells differentiated like the MyoD-transduced BEFS cells, and displayed a similar pattern of expression of muscle regulatory proteins. Taken together, our results indicate that MyoD overexpression overcomes the defect in muscle differentiation associated with immortalization and cell transformation caused by the loss of p53 and Rb functions.

• Molecules and Cells
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• v.22 no.3
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• pp.343-352
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• 2006

Sialic acid is a sugar typically found at the N-glycan termini of glycoproteins in mammalian cells. Lec3 CHO cell mutants are deficient in epimerase activity, due to a defect in the gene that encodes a bifunctional UDP-GlcNAc 2-epimerase/ManNAc kinase (GNE). Sialic acid modification on the cell surface is partially affected in these cells. We have mutagenized Lec3 CHO cells and isolated six mutants (termed C2m) deficient in the cell surface expression of polysialic acid (PSA). Mutant C2m9 was partially defective in expression of cell-surface PSA and wheat germ agglutinin (WGA) binding, while in the other five mutants, both cell-surface PSA and WGA binding were undetectable. PSA expression was restored by complementation with the gene encoding the CMP-sialic acid transporter (CST), indicating that CST mutations were responsible for the phenotypes of the C2m cells. We characterized the CST mutations in these cells by Northern blotting and RT-PCR. C2m9 and C2m45 carried missense mutations resulting in glycine to glutamate substitutions at amino acids 217 (G217E) and 256 (G256E), respectively. C2m13, C2m39 and C2m31 had nonsense mutations that resulted in decreased CST mRNA stability, and C2m34 carried a putative splice site mutation. PSA and CD15s expression in CST-deficient Lec2 cells were partially rescued by G217E CST, but not by G256E CST, although both proteins were expressed at similar levels, and localized to the Golgi. These results indicate that the novel missense mutations isolated in this study affect CST activity.

• Molecules and Cells
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• v.38 no.2
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• pp.138-144
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• 2015

Raloxifene is a selective estrogen receptor modulator (SERM) that binds to the estrogen receptor (ER), and exhibits potent anti-tumor and autophagy-inducing effects in breast cancer cells. However, the mechanism of raloxifene-induced cell death and autophagy is not well-established. So, we analyzed mechanism underlying death and autophagy induced by raloxifene in MCF-7 breast cancer cells. Treatment with raloxifene significantly induced death in MCF-7 cells. Raloxifene accumulated GFP-LC3 puncta and increased the level of autophagic marker proteins, such as LC3-II, BECN1, and ATG12-ATG5 conjugates, indicating activated autophagy. Raloxifene also increased autophagic flux indicators, the cleavage of GFP from GFP-LC3 and only red fluorescence-positive puncta in mRFP-GFP-LC3-expressing cells. An autophagy inhibitor, 3-methyladenine (3-MA), suppressed the level of LC3-II and blocked the formation of GFP-LC3 puncta. Moreover, siRNA targeting BECN1 markedly reversed cell death and the level of LC3-II increased by raloxifene. Besides, raloxifene-induced cell death was not related to cleavage of caspases-7, -9, and PARP. These results indicate that raloxifene activates autophagy-dependent cell death but not apoptosis. Interestingly, raloxifene decreased the level of intracellular adenosine triphosphate (ATP) and activated the AMPK/ULK1 pathway. However it was not suppressed the AKT/mTOR pathway. Addition of ATP decreased the phosphorylation of AMPK as well as the accumulation of LC3-II, finally attenuating raloxifene-induced cell death. Our current study demonstrates that raloxifene induces autophagy via the activation of AMPK by sensing decreases in ATP, and that the overactivation of autophagy promotes cell death and thereby mediates the anti-cancer effects of raloxifene in breast cancer cells.

• Molecules and Cells
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• v.38 no.2
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• pp.130-137
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• 2015

MicroRNAs (miRNAs) are small, endogenous RNAs that play important gene-regulatory roles by binding to the imperfectly complementary sequences at the 3'-UTR of mRNAs and directing their gene expression. Here, we first discovered that miR-576-3p was down-regulated in human bladder cancer cell lines compared with the non-malignant cell line. To better characterize the role of miR-576-3p in bladder cancer cells, we over-expressed or down-regulated miR-576-3p in bladder cancer cells by transfecting with chemically synthesized mimic or inhibitor. The overexpression of miR-576-3p remarkably inhibited cell proliferation via G1-phase arrest, and decreased both mRNA and protein levels of cyclin D1 which played a key role in G1/S phase transition. The knock-down of miR-576-3p significantly promoted the proliferation of bladder cancer cells by accelerating the progression of cell cycle and increased the expression of cyclin D1. Moreover, the dual-luciferase reporter assays indicated that miR-576-3p could directly target cyclin D1 through binding its 3'-UTR. All the results demonstrated that miR-576-3p might be a novel suppressor of bladder cancer cell proliferation through targeting cyclin D1.

• Molecules and Cells
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• v.38 no.12
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• pp.1064-1070
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• 2015

Translocator protein 18 kDa (TSPO) is a mitochondrial outer membrane protein and is abundantly expressed in a variety of organ and tissues. To date, the functional role of TSPO on vascular endothelial cell activation has yet to be fully elucidated. In the present study, the phorbol 12-myristate 13-acetate (PMA, 250 nM), an activator of protein kinase C (PKC), was used to induce vascular endothelial activation. Adenoviral TSPO overexpression (10-100 MOI) inhibited PMA-induced vascular cell adhesion molecule-1 (VCAM-1) and intracellular cell adhesion molecule-1 (ICAM-1) expression in a dose dependent manner. PMA-induced VCAM-1 expressions were inhibited by Mito-TEMPO ($0.1-0.5{\mu}m$), a specific mitochondrial antioxidants, and cyclosporin A ($1-5{\mu}m$), a mitochondrial permeability transition pore inhibitor, implying on an important role of mitochondrial reactive oxygen species (ROS) on the endothelial activation. Moreover, adenoviral TSPO overexpression inhibited mitochondrial ROS production and manganese superoxide dismutase expression. On contrasts, gene silencing of TSPO with siRNA increased PMA-induced VCAM-1 expression and mitochondrial ROS production. Midazolam ($1-50{\mu}m$), TSPO ligands, inhibited PMA-induced VCAM-1 and mitochondrial ROS production in endothelial cells. These results suggest that mitochondrial TSPO can inhibit PMA-induced endothelial inflammation via suppression of VCAM-1 and mitochondrial ROS production in endothelial cells.

• Molecules and Cells
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• v.38 no.10
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• pp.886-894
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• 2015

Macrophages are divided into two subpopulations: classically activated macrophages (M1) and alternatively activated macrophages (M2). BCG (Bacilli Calmette-$Gu{\acute{e}}rin$) activates disabled $na{\ddot{i}}ve$ macrophages to M1 macrophages, which act as inflammatory, microbicidal and tumoricidal cells through cell-cell contact and/or the release of soluble factors. Various transcription factors and signaling pathways are involved in the regulation of macrophage activation and polarization. We discovered that BCG-activated macrophages (BAM) expressed a new molecule, and we named it Novel Macrophage Activated Associated Protein 1 (NMAAP1). 1 The current study found that the overexpression of NMAAP1 in macrophages results in M1 polarization with increased expression levels of M1 genes, such as inducible nitric oxide synthase (iNOS), tumor necrosis factor alpha (TNF-${\alpha}$), Interleukin 6 (IL-6), Interleukin 12 (IL-12), Monocyte chemoattractant protein-1 (MCP-1) and Interleukin-1 beta (IL-$1{\beta}$), and decreased expression of some M2 genes, such as Kruppel-like factor 4 (KLF4) and suppressor of cytokine signaling 1 (SOCS1), but not other M2 genes, including arginase-1 (Arg-1), Interleukin (IL-10), transforming growth factor beta (TGF-${\beta}$) and found in inflammatory zone 1 (Fizz1). Moreover, NMAAP1 overexpression in the RAW264.7 cell line increased cytotoxicity against MCA207 tumor cells, which depends on increased inflammatory cytokines rather than cell-cell contact. NMAAP1 also substantially enhanced the phagocytic ability of macrophages, which implies that NMAAP1 promoted macrophage adhesive and clearance activities. Our results indicate that NMAAP1 is an essential molecule that modulates macrophages phenotype and plays an important role in macrophage tumoricidal functions.

• Molecules and Cells
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• v.39 no.6
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• pp.468-476
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• 2016

PLZF-expressing invariant natural killer T cells and CD4 T cells are unique subsets of innate T cells. Both are selected via thymocyte-thymocyte interaction, and they contribute to the generation of activated/memory-like CD4 and CD8 T cells in the thymus via the production of IL-4. Here, we investigated whether $PLZF^+$ innate T cells also affect the development and function of $Foxp3^+$ regulatory CD4 T cells. Flow cytometry analysis of the thymus and spleen from both CIITA transgenic C57BL/6 and wild-type BALB/c mice, which have abundant $PLZF^+$ CD4 T cells and invariant natural killer T cells, respectively, revealed that $Foxp3^+$ T cells in these mice exhibited a $CD103^+$ activated/memorylike phenotype. The frequency of $CD103^+$ regulatory T cells was considerably decreased in $PLZF^+$ cell-deficient $CIITA^{Tg}Plzf^{lu/lu}$ and $BALB/c.CD1d^{-/-}$ mice as well as in an IL-4-deficient background, such as in $CIITA^{Tg}IL-4^{-/-}$ and $BALB/c.IL-4^{-/-}$ mice, indicating that the acquisition of an activated/ memory-like phenotype was dependent on $PLZF^+$ innate T cells and IL-4. Using fetal thymic organ culture, we further demonstrated that IL-4 in concert with TGF-${\beta}$ enhanced the acquisition of the activated/memory-like phenotype of regulatory T cells. In functional aspects, the activated/ memory-like phenotype of Treg cells was directly related to their suppressive function; regulatory T cells of $CIITA^{Tg}PIV^{-/-}$ mice more efficiently suppressed ovalbumin-induced allergic airway inflammation compared with their counterparts from wild-type mice. All of these findings suggest that $PLZF^+$ innate T cells also augmented the generation of activated/memory-like regulation via IL-4 production.

• Molecules and Cells
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• v.27 no.2
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• pp.175-181
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• 2009

The myosin light chain kinase (MYLK) gene encodes both smooth muscle and nonmuscle cell isoforms. Recently, polymorphisms in MYLK have been reported to be associated with several diseases. To examine the genetic effects of polymorphisms on the risk of asthma and related phenotypes, we scrutinized MYLK by re-sequencing/genotyping and statistical analysis in Korean population (n = 1,015). Seventeen common polymorphisms located in or near exons, having pairwise $r^2$ values less than 0.25, were genotyped. Our statistical analysis did not replicate the associations with the risk of asthma and log-transformed total IgE levels observed among African descendant populations. However, two SNPs in intron 16 (+89872C> G and +92263T> C), which were in tight LD (|D'| = 0.99), revealed significant association with log-transformed blood eosinophil level even after correction multiple testing ($P=0.002/P^{corr}=0.01$ and $P=0.002/P^{corr}=0.01$, respectively). The log-transformed blood eosinophil levels were higher in individuals bearing the minor alleles for +89872C> G and +92263T> C than in those bearing other allele. In additional subgroup analysis, the genetic effects of both SNPs were much more apparent among asthmatic patients and atopic asthma patients. Among atopic asthma patients, the log-transformed blood eosinophil levels were proportionally increased by gene-dose dependent manner of in both +89872C> G and +92263T> C(P = 0.0002 and P = 0.00007, respectively). These findings suggest that MYLK polymorphisms might be among the genetic factors underlying differential increases of blood eosinophil levels among asthmatic patients. Further biological and/or functional studies are needed to confirm our results.

• Molecules and Cells
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• v.37 no.5
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• pp.426-434
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• 2014

Peptidylarginine deiminase type 2 (PADI2) deiminates (or citrullinates) arginine residues in protein to citrulline residues in a $Ca^{2+}$-dependent manner, and is found in lymphocytes and macrophages. Vimentin is an intermediate filament protein and a well-known substrate of PADI2. Citrullinated vimentin is found in ionomycin-induced macrophage apoptosis. Citrullinated vimentin is the target of anti-Sa antibodies, which are specific to rheumatoid arthritis, and play a critical role in the pathogenesis of the disease. To investigate the role of PADI2 in apoptosis, we generated a Jurkat cell line that overexpressed the PADI2 transgene from a tetracycline-inducible promoter, and used a combination of 12-O-tetradecanoylphorbol-13-acetate and ionomycin to activate Jurkat cells. We found that PADI2 overexpression reduced the cell viability of activated Jurkat cells in1a dose- and time-dependent manner. The PADI2-overexpressed and -activated Jurkat cells presented typical manifestations of apoptosis, and exhibited greater levels of citrullinated proteins, including citrullinated vimentin. Vimentin overexpression rescued a portion of the cells from apoptosis. In conclusion, PADI2 overexpression induces apoptosis in activated Jurkat cells. Vimentin is involved in PADI2-induced apoptosis. Moreover, PADI2-overexpressed Jurkat cells secreted greater levels of vimentin after activation, and expressed more vimentin on their cell surfaces when undergoing apoptosis. Through artificially highlighting PADI2 and vimentin, we demonstrated that PADI2 and vimentin participate in the apoptotic mechanisms of activated T lymphocytes. The secretion and surface expression of vimentin are possible ways of autoantigen presentation to the immune system.