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Regulated RalBP1 Binding to RalA and PSD-95 Controls AMPA Receptor Endocytosis and LTD
Han, Kihoon,Kim, Myoung-Hwan,Seeburg, Daniel,Seo, Jinsoo,Verpelli, Chiara,Han, Seungnam,Chung, Hye Sun,Ko, Jaewon,Lee, Hyun Woo,Kim, Karam,Heo, Won Do,Meyer, Tobias,Kim, Hyun,Sala, Carlo,Choi, Se-Youn Public Library of Science 2009 PLoS biology Vol.7 No.9
<▼1><P>A two step mechanism was identified that regulates receptor endocytosis during the development of long-term depression (LTD), a long-lasting decrease in synaptic transmission.</P></▼1><▼2><P>Long-term depression (LTD) is a long-lasting activity-dependent decrease in synaptic strength. NMDA receptor (NMDAR)–dependent LTD, an extensively studied form of LTD, involves the endocytosis of AMPA receptors (AMPARs) via protein dephosphorylation, but the underlying mechanism has remained unclear. We show here that a regulated interaction of the endocytic adaptor RalBP1 with two synaptic proteins, the small GTPase RalA and the postsynaptic scaffolding protein PSD-95, controls NMDAR-dependent AMPAR endocytosis during LTD. NMDAR activation stimulates RalA, which binds and translocates widespread RalBP1 to synapses. In addition, NMDAR activation dephosphorylates RalBP1, promoting the interaction of RalBP1 with PSD-95. These two regulated interactions are required for NMDAR-dependent AMPAR endocytosis and LTD and are sufficient to induce AMPAR endocytosis in the absence of NMDAR activation. RalA in the basal state, however, maintains surface AMPARs. We propose that NMDAR activation brings RalBP1 close to PSD-95 to promote the interaction of RalBP1-associated endocytic proteins with PSD-95-associated AMPARs. This suggests that scaffolding proteins at specialized cellular junctions can switch their function from maintenance to endocytosis of interacting membrane proteins in a regulated manner.</P></▼2><▼3><P><B>Author Summary</B></P><P>Neurons adapt over time in order to dampen their response to prolonged or particularly strong stimuli. This process, termed long-term depression (LTD), results in a long-lasting decrease in the efficiency of synaptic transmission. One extensively studied form of LTD requires the activation of a specific class of receptors known as NMDA glutamate receptors (NMDARs). A key molecular event initiated by NMDA receptor activation is the stimulation of protein phosphatases. Another key event is internalization via endocytosis of synaptic AMPA glutamate receptors (AMPARs). However, the mechanism by which protein dephosphorylation is coupled to AMPAR endocytosis has remained unclear. Here, we help to define this mechanism. We show that endocytic proteins, including RalBP1, are widely distributed in neurons under normal conditions. Upon NMDAR activation, the small GTPase RalA becomes activated and binds to RalBP1, resulting in the translocation of RalBP1 and RalBP1-associated endocytic proteins to synapses. At the same time, RalBP1 becomes dephosphorylated, which promotes its binding to the postsynaptic scaffold protein PSD-95, a protein that itself associates with AMPARs. This concerted recruitment of endocytic proteins to the vicinity of AMPARs results in AMPAR endocytosis. On the basis of our data, we propose a model in which dual binding of RalBP1 to both RalA and PSD-95 following RalBP1 dephosphorylation is essential for NMDAR-dependent AMPAR endocytosis during LTD.</P></▼3>
Han, Karam,Im, Won Bin,Heo, Jong,Chung, Woon Jin The Royal Society of Chemistry 2016 Chemical communications Vol.52 No.17
<P>A complete inorganic quantum dot color converter for a white LED is achieved using silicate-based quantum-dot-embedded glasses (QDEGs). The white LED exhibits a high CRI of 90 and highly improved thermal stability up to 200 degrees C, demonstrating its robustness and practicality. The CdSe/CdS core/shell structure within the silicate glass is expected to enhance the colour converting efficiency.</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>
OpenFOAM을 이용한 난류연소현상 해석 및 내연기관에의 적용
한가람(Karam Han),임성한(Seonghan Im),허강열(Kang Y. Huh) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.41
OpenFOAM(Open Field Operation And Manipulation) is based on the object oriented language and has been developed as an alternative to commercial CFD tools for industrial application. The advantages of open source CFD allow users to create a more extensive and customized code according to users needs, whereas the commercial tools have difficulty to add or modify any user defined code. To perform IC engine simulation an automatic mesh motion algorithm is built into OpenFOAM. OpenFOAM also provides users with many solvers such as heat transfer and multi phase flow with combustion. In this study simulation of sydney bluff-body HM1 flame, IC engines and gas turbine combustion were performed by OpenFOAM to analyze the turbulent combustion problems. The PaSR(Partially Stirred Reactor) model was applied for a CI engine and gas turbine, while the b-Ξmodel was applied for an SI engine. Results were compared with measurements for some typical test cases.
가스터빈 열 회수 증기 발생기의 배출 가스 예측 모사 해석
한우주(Woojoo Han),장지훈(Jihoon Jang),이영재(Youngjae Lee),한가람(Karam Han),허강열(Kang Y. Huh) 한국연소학회 2014 KOSCOSYMPOSIUM논문집 Vol.2014 No.11
We performed computational simulation for a heat recovery steam generator to predict emissions (especially carbon monoxide) and compare the results with experimental data. We used the steady laminar flamelet model(SLFM) which can consider detailed chemical mechanisms. To reduce the number of grid, we simplified the geometry of the whole heat recovery steam generator. In conclusion, the trend of simulation results is good agreement with experimental data.
Karam Kang,Kwang Yoon Jung,Doh Young Lee,Jae Hyung Kim,Hye Min Han,ln Hak Choi,Seung-Kuk Baek,Hyunjung Kim 대한연하장애학회 2018 대한연하장애학회지 Vol.8 No.1
Objective: Pharyngoesophageal stricture formation and dysphagia following total laryngectomy negatively affect quality of life and result in nutritional compromise that can be successfully managed with various techniques. This study was conducted to describe our experiences of office-based balloon dilatation by transnasal endoscopy, which can be performed by an otolaryngologist. Method: The present study investigated three patients who underwent transnasal endoscopy guided balloon dilatation of pharyngoesophageal stricture. The assessment was performed based on the number of procedures and recurrences, final subjective outcomes, and complications. Result: There were no post-procedural complications. In one patient, a scarric band was found after the procedure; therefore, steroids were injected into the stricture site. There were 2–3 balloon dilatations and the interval between dilatations was 3–6 months. All patients were able to tolerate solid diet after 2 or 3 sessions. Conclusion: Transnasal endoscopic balloon dilatation, which can be easily performed by an otolaryngologist in an office setting without sedation or general anesthesia, can be a useful modality for treating pharyngoesophageal stricture after total laryngectomy. (
Film Formation of CdSe Quantum Dot Embedded Phosphate Glass on an FTO Glass Substrate
정운진,Karam Han,김윤화,임원빈 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.4
A thick film with CdSe quantum dot (QD) embedded glass was formed on a fluorine-doped tin oxide (FTO) glass substrate. Phosphate glasses with different CdO and ZnSe concentrations were synthesized, and the heat treatment conditions were varied to determine the appropriate QD and film formation conditions. Phosphate glass with 1 mol. % CdO and 1.5 mol. % ZnSe showed controlled crystallization of CdSe QDs when they were heat treated at 550°C for 1 hr. Absorption spectra and Raman spectroscopy identified the QD formation. Precursor glass was ground into powder and pasted onto FTO only and TiO2/FTO glass substrates via the screen printing method. Glass film embedded with QDs was successfully formed after sintering, thus demonstrating its potential for film applications.