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Jung, Hyeyun,Shin, Jihyun,Chae, Changju,Lee, Jung Kyoo,Kim, Jongsik American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.29
<P>FeF<SUB>3</SUB> is of great interest as a potential candidate cathode material because of its low cost, abundance, environmental friendliness, and high theoretical capacity of about 237 mAh·g<SUP>–1</SUP> in the voltage range of 2.0–4.5 V. However, FeF<SUB>3</SUB> has drawbacks of poor cycling stability and rate performance because of its low intrinsic electrical conductivity and slow diffusion of lithium ions. These issues should be improved for the practical application of FeF<SUB>3</SUB> in lithium-ion battery systems. In this study, FeF<SUB>3</SUB>/ordered mesoporous carbon (OMC) nanocomposites were synthesized by an incipient-wetness impregnation technique in a facile and scalable method. The tubular shaped OMC was utilized as both a conductive agent and a hard template for the formation of nanosized FeF<SUB>3</SUB> particles. The FeF<SUB>3</SUB>/OMC nanocomposites showed enhanced capacity, cycling stability, and rate performance compared to bulk FeF<SUB>3</SUB> in the voltage range of 2.0–4.5 V at room temperature.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-29/jp4023162/production/images/medium/jp-2013-023162_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp4023162'>ACS Electronic Supporting Info</A></P>
Inactivation of Medial Prefrontal Cortex Impairs Time Interval Discrimination in Rats
Kim, Jieun,Jung, Amy Hyeyun,Byun, Jayoung,Jo, Suhyun,Jung, Min Whan Frontiers Research Foundation 2009 Frontiers in Behavioral Neuroscience Vol.3 No.-
<P>Several lines of evidence suggest the involvement of prefrontal cortex in time interval estimation. The underlying neural processes are poorly understood, however, in part because of the paucity of physiological studies. The goal of this study was to establish an interval timing task for physiological recordings in rats, and test the requirement of intact medial prefrontal cortex (mPFC) for performing the task. We established a temporal bisection procedure using six different time intervals ranging from 3018 to 4784 ms that needed to be discriminated as either long or short. Bilateral infusions of muscimol (GABA<SUB>A</SUB> receptor agonist) into the mPFC significantly impaired animal's performance in this task, even when the animals were required to discriminate between only the longest and shortest time intervals. These results show the requirement of intact mPFC in rats for time interval discrimination in the range of a few seconds.</P>
Kim, Won-Kon,Jung, Hyeyun,Kim, Do-Hyung,Kim, Eun-Young,Chung, Jin-Woong,Cho, Yee-Sook,Park, Sung-Goo,Park, Byoung-Chul,Ko, Yong,Bae, Kwang-Hee,Lee, Sang-Chul Cambridge University Press 2009 Journal of cell science Vol.122 No.22
<P>Mesenchymal stem cells (MSCs) are multipotent adult stem cells that can differentiate into a variety of mesodermal-lineage cells. MSCs have significant potential in tissue engineering and therapeutic applications; however, the low differentiation and proliferation efficiencies of these cells in the laboratory are fundamental obstacles to their therapeutic use, mainly owing to the lack of information on the detailed signal-transduction mechanisms of differentiation into distinct lineages. With the aid of protein-tyrosine-phosphatase profiling studies, we show that the expression of leukocyte common antigen related (LAR) tyrosine phosphatase is significantly decreased during the early adipogenic stages of MSCs. Knockdown of endogenous LAR induced a dramatic increase in adipogenic differentiation, whereas its overexpression led to decreased adipogenic differentiation in both 3T3-L1 preadipocytes and MSCs. LAR reduces tyrosine phosphorylation of the insulin receptor, in turn leading to decreased phosphorylation of the adaptor protein IRS-1 and its downstream molecule Akt (also known as PKB). We propose that LAR functions as a negative regulator of adipogenesis. Furthermore, our data support the possibility that LAR controls the balance between osteoblast and adipocyte differentiation. Overall, our findings contribute to the clarification of the mechanisms underlying LAR activity in the differentiation of MSCs and suggest that LAR is a candidate target protein for the control of stem-cell differentiation.</P>
Kim, Won Kon,Jung, Hyeyun,Kim, Eun Young,Kim, Do Hyung,Cho, Yee Sook,Park, Byoung Chul,Park, Sung Goo,Ko, Yong,Bae, Kwang-Hee,Lee, Sang Chul The American Society for Cell Biology 2011 Molecular biology of the cell Vol.22 No.24
<P>Adipocyte differentiation can be regulated by the combined activity of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). In particular, PTPs act as key regulators in differentiation-associated signaling pathways. We recently found that receptor-type PTPμ (RPTPμ) expression is markedly increased during the adipogenic differentiation of 3T3-L1 preadipocytes and mesenchymal stem cells. Here, we investigate the functional roles of RPTPμ and the mechanism of its involvement in the regulation of signal transduction during adipogenesis of 3T3-L1 cells. Depletion of endogenous RPTPμ by RNA interference significantly inhibited adipogenic differentiation, whereas RPTPμ overexpression led to an increase in adipogenic differentiation. Ectopic expression of p120 catenin suppressed adipocyte differentiation, and the decrease in adipogenesis by p120 catenin was recovered by introducing RPTPμ. Moreover, RPTPμ induced a decrease in the cytoplasmic p120 catenin expression by reducing its tyrosine phosphorylation level, consequently leading to enhanced translocation of Glut-4 to the plasma membrane. On the basis of these results, we propose that RPTPμ acts as a positive regulator of adipogenesis by modulating the cytoplasmic p120 catenin level. Our data conclusively demonstrate that differentiation into adipocytes is controlled by RPTPμ, supporting the utility of RPTPμ and p120 catenin as novel target proteins for the treatment of obesity.</P>
Yu, Keum Ran,Kim, Young Jun,Jung, Suk-Kyeong,Ku, Bonsu,Park, Hwangseo,Cho, Sa Yeon,Jung, Hyeyun,Chung, Sang J,Bae, Kwang Hee,Lee, Sang Chul,Kim, Bo Yeon,Erikson, Raymond L,Ryu, Seong Eon,Kim, Seung Ju Wiley-Blackwell 2013 Acta crystallographica. Section D, Biological crys Vol.69 No.8
<P>Unlike other classical protein tyrosine phosphatases (PTPs), PTPRQ (PTP receptor type Q) has dephosphorylating activity towards phosphatidylinositide (PI) substrates. Here, the structure of the catalytic domain of PTPRQ was solved at 1.56?? resolution. Overall, PTPRQ adopts a tertiary fold typical of other classical PTPs. However, the disordered M6 loop of PTPRQ surrounding the catalytic core and the concomitant absence of interactions of this loop with residues in the PTP loop results in a flat active-site pocket. On the basis of structural and biochemical analyses, it is proposed that this structural feature might facilitate the accommodation of large substrates, making it suitable for the dephosphorylation of PI substrates. Moreover, subsequent kinetic experiments showed that PTPRQ has a strong preferences for PI(3,4,5)P3 over other PI substrates, suggesting that its regulation of cell survival and proliferation reflects downregulation of Akt signalling.</P>
( Sun Young Lee ),( Jeong Hoon Kim ),( Hyeyun Jung ),( Seung Wook Chi ),( Sang J. Chung ),( Chong Kil Lee ),( Byoung Chul Park ),( Kwang Hee Bae ),( Sung Goo Park ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.4
Glyceraldehyde-3-phosphate (G-3-P), the substrate of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), is a key intermediate in several metabolic pathways. Recently, we reported that G-3-P directly inhibits caspase-3 activity in a reversible noncompetitive mode, suggesting the intracellular G-3-P level as a cell fate decision factor. It has been known that apoptotic stimuli induce the generation of NO, and NO S-nitrosylates GAPDH at the catalytic cysteine residue, which confers GAPDH the ability to bind to Siah-1, an E3 ubiquitin ligase. The GAPDH-Siah-1 complex is translocated into the nucleus and subsequently triggers the apoptotic process. Here, we clearly showed that intracellular G-3-P protects GAPDH from S-nitrosylation at above a certain level, and consequently maintains the cell survival. In case G-3-P drops below a certain level as a result of exposure to specific stimuli, G-3-P cannot inhibit S-nitrosylation of GAPDH anymore, and consequently GAPDH translocates with Siah-1 into the nucleus. Based on these results, we suggest that G-3-P functions as a molecule switch between cell survival and apoptosis by regulating S-nitrosylation of GAPDH.
Phosphoproteomic analysis of neuronal cell death by glutamate-induced oxidative stress
Kang, Tae Hyuk,Bae, Kwang-Hee,Yu, Min-jung,Kim, Won-Kon,Hwang, Hyang-Ran,Jung, Hyeyun,Lee, Phil Young,Kang, Sunghyun,Yoon, Tae-Sung,Park, Sung Goo,Ryu, Seong Eon,Lee, Sang Chul WILEY-VCH Verlag 2007 Proteomics Vol.7 No.15
<P>Oxidative stress is one of the major causes of neuronal cell death in disorders such as perinatal hypoxia and ischemia. Protein phosphorylation is the most significant PTM of proteins and plays an important role in stress-induced signal transduction. Thus, the analysis of alternative protein phosphorylation states which occur during oxidative stress-induced cell death could provide valuable information regarding cell death. In this study, a reference phosphoproteome map of the mouse hippocampal cell line HT22 was constructed based on 125 spots that were identified by MALDI-TOF or LC-ESI-Q-TOF-MS analysis. In addition, proteins of HT22 cells at various stages of oxidative stress-induced cell death were separated by 2-DE and alterations in phosphoproteins were detected by Pro-Q Diamond staining. A total of 17 spots showing significant quantitative changes and seven newly appearing spots were identified after glutamate treatment. Splicing factor 2, peroxiredoxin 2, S100 calcium binding protein A11, and purine nucleoside phosphorylase were identified as up- or down-regulated proteins. CDC25A, caspase-8, and cyp51 protein appeared during oxidative stress-induced cell death. The data in this study from phosphoproteomic analysis provide a valuable resource for the understanding of HT22 cell death mechanisms mediated by oxidative stress.</P>