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NGL family PSD-95–interacting adhesion molecules regulate excitatory synapse formation
Kim, Seho,Burette, Alain,Chung, Hye Sun,Kwon, Seok-Kyu,Woo, Jooyeon,Lee, Hyun Woo,Kim, Karam,Kim, Hyun,Weinberg, Richard J,Kim, Eunjoon NATURE AMERICA 2006 NATURE NEUROSCIENCE Vol.9 No.10
Synaptic cell adhesion molecules (CAMs) regulate synapse formation through their trans-synaptic and heterophilic adhesion. Here we show that postsynaptic netrin-G ligand (NGL) CAMs associate with netrin-G CAMs in an isoform-specific manner and, through their cytosolic tail, with the abundant postsynaptic scaffold postsynaptic density–95 (PSD-95). Overexpression of NGL-2 in cultured rat neurons increased the number of PSD-95–positive dendritic protrusions. NGL-2 located on heterologous cells or beads induced functional presynaptic differentiation in contacting neurites. Direct aggregation of NGL-2 on the surface membrane of dendrites induced the clustering of excitatory postsynaptic proteins. Competitive inhibition by soluble NGL-2 reduced the number of excitatory synapses. NGL-2 knockdown reduced excitatory, but not inhibitory, synapse numbers and currents. These results suggest that NGL regulates the formation of excitatory synapses.
Kim, Myoung-Hwan,Choi, Jeonghoon,Yang, Jinhee,Chung, Woosuk,Kim, Ji-Hyun,Paik, Sang Kyoo,Kim, Karam,Han, Seungnam,Won, Hyejung,Bae, Young-Soo,Cho, Suk-Hee,Seo, Jinsoo,Bae, Yong Chul,Choi, Se-Young,Kim The Society 2009 The Journal of neuroscience Vol.29 No.5
<P>IRSp53 is an adaptor protein that acts downstream of Rac and Cdc42 small GTPases and is implicated in the regulation of membrane deformation and actin filament assembly. In neurons, IRSp53 is an abundant postsynaptic protein and regulates actin-rich dendritic spines; however, its in vivo functions have not been explored. We characterized transgenic mice deficient of IRSp53 expression. Unexpectedly, IRSp53(-/-) neurons do not show significant changes in the density and ultrastructural morphologies of dendritic spines. Instead, IRSp53(-/-) neurons exhibit reduced AMPA/NMDA ratio of excitatory synaptic transmission and a selective increase in NMDA but not AMPA receptor-mediated transmission. IRSp53(-/-) hippocampal slices show a markedly enhanced long-term potentiation (LTP) with no changes in long-term depression. LTP-inducing theta burst stimulation enhances NMDA receptor-mediated transmission. Spatial learning and novel object recognition are impaired in IRSp53(-/-) mice. These results suggest that IRSp53 is involved in the regulation of NMDA receptor-mediated excitatory synaptic transmission, LTP, and learning and memory behaviors.</P>
Kim, Myeong Seop,Ryu, HyungChul,Kang, Dong Wook,Cho, Seong-Hee,Seo, Sejin,Park, Young Soo,Kim, Mi-Yeon,Kwak, Eun Joo,Kim, Yong Soo,Bhondwe, Rahul S.,Kim, Ho Shin,Park, Seul-gi,Son, Karam,Choi, Sun,DeA American Chemical Society 2012 Journal of medicinal chemistry Vol.55 No.19
<P>A series of <I>N</I>-(2-amino-6-trifluoromethylpyridin-3-ylmethyl)-2-(3-fluoro-4-methylsulfonylaminophenyl)propanamides were designed combining previously identified pharmacophoric elements and evaluated as hTRPV1 antagonists. The SAR analysis indicated that specific hydrophobic interactions of the 2-amino substituents in the C-region of the ligand were critical for high hTRPV1 binding potency. In particular, compound <B>49</B><I><B>S</B></I> was an excellent TRPV1 antagonist (<I>K</I><SUB>i(CAP)</SUB> = 0.2 nM; IC<SUB>50(pH)</SUB> = 6.3 nM) and was thus approximately 100- and 20-fold more potent, respectively, than the parent compounds <B>2</B> and <B>3</B> for capsaicin antagonism. Furthermore, it demonstrated strong analgesic activity in the rat neuropathic model superior to <B>2</B> with almost no side effects. Compound <B>49</B><I><B>S</B></I> antagonized capsaicin induced hypothermia in mice but showed TRPV1-related hyperthermia. The basis for the high potency of <B>49</B><I><B>S</B></I> compared to <B>2</B> is suggested by docking analysis with our hTRPV1 homology model in which the 4-methylpiperidinyl group in the C-region of <B>49</B><I><B>S</B></I> made additional hydrophobic interactions with the hydrophobic region.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jmcmar/2012/jmcmar.2012.55.issue-19/jm300780p/production/images/medium/jm-2012-00780p_0014.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jm300780p'>ACS Electronic Supporting Info</A></P>
Synaptic removal of diacylglycerol by DGKzeta and PSD-95 regulates dendritic spine maintenance.
Kim, Karam,Yang, Jinhee,Zhong, Xiao-Ping,Kim, Myoung-Hwan,Kim, Yun Sook,Lee, Hyun Woo,Han, Seungnam,Choi, Jeonghoon,Han, Kihoon,Seo, Jinsoo,Prescott, Stephen M,Topham, Matthew K,Bae, Yong Chul,Koretzk Published for the European Molecular Biology Organ 2009 The EMBO journal Vol.28 No.8
<P>Diacylglycerol (DAG) is an important lipid signalling molecule that exerts an effect on various effector proteins including protein kinase C. A main mechanism for DAG removal is to convert it to phosphatidic acid (PA) by DAG kinases (DGKs). However, it is not well understood how DGKs are targeted to specific subcellular sites and tightly regulates DAG levels. The neuronal synapse is a prominent site of DAG production. Here, we show that DGKzeta is targeted to excitatory synapses through its direct interaction with the postsynaptic PDZ scaffold PSD-95. Overexpression of DGKzeta in cultured neurons increases the number of dendritic spines, which receive the majority of excitatory synaptic inputs, in a manner requiring its catalytic activity and PSD-95 binding. Conversely, DGKzeta knockdown reduces spine density. Mice deficient in DGKzeta expression show reduced spine density and excitatory synaptic transmission. Time-lapse imaging indicates that DGKzeta is required for spine maintenance but not formation. We propose that PSD-95 targets DGKzeta to synaptic DAG-producing receptors to tightly couple synaptic DAG production to its conversion to PA for the maintenance of spine density.</P>
Information uncertainty, market sentiment, and analyst reports
Karam Kim,Doojin Ryu,Heejin Yang 한국재무학회 2020 한국재무학회 학술대회 Vol.2020 No.11
This study examines the effects of investor sentiment and information uncertainty on the stock market response to analyst recommendation changes within a unified framework. Recent progress in the field of behavioral finance suggests that sentiment affects the classical relationship between analyst recommendations and stock return dynamics. Our novel findings suggest that the degree of information uncertainty should be considered when investigating the effect of sentiment. Although investor sentiment significantly explains the observed stock market reactions to analyst recommendation changes under high information uncertainty, it loses its explanatory power under low information uncertainty. Furthermore, analyst recommendations convey significant trading indications if information uncertainty is high, but they are less informative if information uncertainty is low.
Mo-doped BiVO<sub>4</sub> nanotextured pillars as efficient photoanodes for solar water splitting
Kim, Min-Woo,Kim, Karam,Ohm, Tae Yoon,Joshi, Bhavana,Samuel, Edmund,Swihart, Mark T.,Yoon, Hyun,Park, Hyunwoong,Yoon, Sam S. Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.726 No.-
<P><B>Abstract</B></P> <P>We present electrospray-deposited nanotextured Mo-doped BiVO<SUB>4</SUB> pillars with improved photoelectrochemical water splitting performance. The three-dimensional nanotextured Mo-BiVO<SUB>4</SUB> pillars exhibit large interstitial spaces, which result in a high photocurrent. The doping of Mo at the optimal concentration (0.15%) results in a two-fold increase in the photocurrent density (PCD) (1.78 mA·cm<SUP>−2</SUP> at 1.2 V versus Ag/AgCl) over that of pristine BiVO<SUB>4</SUB>. We attribute this increase in the PCD to increases in recombination time and in donor (electron) concentration owing to the doping with hexavalent Mo, as confirmed by Bode phase and Mott-Schottky analyses, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mo-doped BiVO<SUB>4</SUB> films are formed by electrospray deposition. </LI> <LI> Films consist of 3D nanotextured pillars, which help increase the photocurrent. </LI> <LI> Optimal Mo doping results in two-fold increase in photocurrent density. </LI> <LI> This is owing to an increase in the time constant for electron recombination. </LI> <LI> Another factor responsible is the increase in donor (electron) concentration. </LI> </UL> </P>
Packing of metalized polymer nanofibers for aneurysm embolization
Kim, Min-Woo,An, Seongpil,Kim, Karam,Kim, Tae-Gun,Jo, Hong Seok,Park, Dong-Hyuk,Yoon, Sam S.,Yarin, Alexander L. The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.14
<P>Aneurysmal subarachnoid hemorrhage (SAH) is the extravasation of blood into the subarachnoid space and is fatal in most cases. Platinum coils have been used to fill the hemorrhage site and prevent the extravasation of blood. Here we explored the use of Pt-coated polymer nanofibers (NF) to prevent blood extravasation and were able to achieve improved results <I>in vitro</I>. The polymer nanofibers were produced <I>via</I> electrospinning and were subsequently electroplated with Pt, resulting in metalized nanofibers. These nanofibers were installed within a microfluidic channel, and the resulting reduction in the permeability was evaluated using a fluid similar to blood. Based on the obtained results, these newly developed nanofibers are expected to decrease the operation cost for SAH, owing to their reduced size and low material cost. Furthermore, it is expected that these nanofibers will be used in a smaller amount during SAH operation while having the same preventive effect. This should reduce the operational risk associated with the multiple steps required to place the Pt coils at the SAH site. Finally, the underlying hydrodynamic mechanism responsible for the reduced permeability of the synthesized nanofibers is described.</P>
Kim, Min-Woo,Kim, Karam,Ohm, Tae Yoon,Yoon, Hyun,Joshi, Bhavana,Samuel, Edmund,Swihart, Mark T.,Choi, Sung Kyu,Park, Hyunwoong,Yoon, Sam S. Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.333 No.-
<P><B>Abstract</B></P> <P>We report the fabrication and the performance in photoelectrochemical water splitting of thin films of electrostatically sprayed nanotextured bismuth vanadate (BiVO<SUB>4</SUB>) pillars coated with thin ZnO/TiO<SUB>2</SUB> passivation layers formed by atomic layer deposition. The thin ZnO and TiO<SUB>2</SUB> layers deposited on the BiVO<SUB>4</SUB> nanopillars formed a heterostructure that promoted electron–hole separation and the migration of electrons toward the ITO substrate. The photocurrent density (PCD) of the ZnO/TiO<SUB>2</SUB> coated BiVO<SUB>4</SUB> was 2.5 times higher (2.25mA/cm<SUP>2</SUP> at 1.2V (versus Ag/AgCl)) than that of pristine BiVO<SUB>4</SUB> (0.9mA/cm<SUP>2</SUP> at 1.2V (versus Ag/AgCl)). We present incident/absorbed photon-to-current efficiency and electrochemical impedance measurements confirming that this improvement is a result of the heterojunction produced by the conformal ZnO/TiO<SUB>2</SUB> coating and discuss the mechanism of this dramatic enhancement of PCD.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrosprayed nanotextured bismuth vanadate (BiVO<SUB>4</SUB>) pillars were covered with ZnO/TiO<SUB>2</SUB> layers via atomic layer deposition. </LI> <LI> ZnO/TiO<SUB>2</SUB>-coated BiVO<SUB>4</SUB> pillars were used in photoelectrochemical water splitting. </LI> <LI> This heterostructure structure promoted electron–hole separation and the migration of electrons. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Lenalidomide induces apoptosis and alters gene expression in non-small cell lung cancer cells
KIM, KARAM,AN, SUNGKWAN,CHA, HWA JUN,CHOI, YEONG MIN,CHOI, SUNG JIN,AN, IN-SOOK,LEE, HONG GHI,MIN, YOO HONG,LEE, SU-JAE,BAE, SEUNGHEE D.A. Spandidos 2013 Oncology letters Vol.5 No.2
<P>Non-small cell lung cancer (NSCLC) is the most deadly type of cancer worldwide. Although a number of therapies are used in NSCLC treatment, their therapeutic efficacy remains low. Lenalidomide was originally approved for use in patients with myelodysplastic syndromes, which are associated with 5q deletions, and multiple myeloma. Recently, lenalidomide was investigated as a new NSCLC treatment, and it exerted anticancer effects. However, the primary cellular mechanism of its effects in NSCLC is largely unknown. Therefore, we attempted to elucidate a molecular portrait of lenalidomide-mediated cellular events in NSCLC. Lenalidomide reduced the viability of several NSCLC cell lines in a concentration-dependent manner. In addition, array-based gene expression analysis revealed that lenalidomide regulated the expression of several genes associated with cell survival, apoptosis and development, including BH3-interacting domain death agonist (BID), v-fos FBJ murine osteosarcoma viral oncogene homolog (FOS) and NK2 homeobox1 (NKX2-1). BID and FOS, which are known apoptosis activators, were upregulated by lenalidomide treatment, whereas NKX2-1, which is used as an immunohistochemistry marker for NSCLC, was downregulated. These results provide evidence that lenalidomide directly induces antiproliferative effects by altering the expression of genes associated with cell proliferation and apoptosis.</P>