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Search Results: 1 - 10 of 29782 matches for " Seok-Yong Choi "
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A novel cell-free mitochondrial fusion assay amenable for high-throughput screenings of fusion modulators
Astrid C Schauss, Huiyan Huang, Seok-Yong Choi, Liqun Xu, Sébastien Soubeyrand, Patricia Bilodeau, Rodolfo Zunino, Peter Rippstein, Michael A Frohman, Heidi M McBride
BMC Biology , 2010, DOI: 10.1186/1741-7007-8-100
Abstract: In order to overcome these technical limitations, we have developed a new, highly quantitative cell-free assay for mitochondrial fusion in mammalian cells. This assay system has allowed us to establish the energetic requirements for mitochondrial fusion. In addition, our data reveal a dependence on active protein phosphorylation for mitochondrial fusion, confirming emerging evidence that mitochondrial fusion is tightly integrated within the global cellular response to signaling events. Indeed, we have shown that cytosol derived from cells stimulated with different triggers either enhance or inhibit the cell-free fusion reaction.The adaptation of this system to high-throughput analysis will provide an unprecedented opportunity to identify and characterize novel regulatory factors. In addition, it provides a framework for a detailed mechanistic analysis of the process of mitochondrial fusion and the various axis of regulation that impinge upon this process in a wide range of cellular conditions.See Commentary: http://www.biomedcentral.com/1741-7007/8/99 webciteMitochondria are highly dynamic organelles, whose plasticity allows them to respond quickly to cellular cues that regulate their cellular position, interconnectivity and function [1]. In this way, the dynamic behaviour of the mitochondria must be tightly coupled to cellular signalling cascades in order to respond in such a coordinated fashion. The molecular mechanisms that govern mitochondrial fusion have been best described using yeast genetics, where genome-wide screens have identified the essential components of the fusion reaction [2-4]. In addition to these genetic screens, a cell-free mitochondrial fusion assay has been developed using yeast mitochondria labelled with various fluorescent markers within the matrix and outer membranes [5]. This assay has provided important insights into the specific role of the fusion GTPases Fzo1 and Mgm1, along with the multispanning membrane protein Ugo1, in the regulatio
A role for Phospholipase D in Drosophila embryonic cellularization
Mary LaLonde, Hilde Janssens, Suyong Yun, Juan Crosby, Olga Redina, Virginie Olive, Yelena M Altshuller, Seok-Yong Choi, Guangwei Du, J Peter Gergen, Michael A Frohman
BMC Developmental Biology , 2006, DOI: 10.1186/1471-213x-6-60
Abstract: We describe here involvement of the signaling enzyme Phospholipase D (Pld) in regulation of this developmental step. Functional analysis using gene targeting revealed that cellularization is hindered by the loss of Pld, resulting frequently in early embryonic developmental arrest. Mechanistically, chronic Pld deficiency causes abnormal Golgi structure and secretory vesicle trafficking.Our results suggest that Pld functions to promote trafficking of Golgi-derived fusion-competent vesicles during cellularization.Embryogenesis in Drosophila melanogaster commences with 13 nuclear divisions in the absence of cytokinesis, generating a syncytium of ~6,000 nuclei located immediately beneath the plasma membrane. Cellularization then ensues, resulting in the synchronous formation of lateral and then basal membranes around each nucleus through rearrangement of the actin cytoskeleton and extensive formation of de novo membrane. It is estimated that a 25-fold increase in plasma membrane is necessary to complete the process. The de novo membrane comes from the resorption of microvilli on the outer surface of the blastoderm [1,2] and the incorporation of ER- and/or Golgi-derived secretory vesicles [3-7].Genetic screens have identified numerous proteins that regulate cytoskeletal reorganization during cellularization, several proteins of unknown function including SLAM [7] that are required at the leading edge of the extending lateral membrane (the furrow canal), and a plasma-membrane associated component of the exocytic membrane trafficking machinery, the SNARE protein Syntaxin1 (Syx1A, reviewed in Mazumdar and Mazumdar, 2002). Both Syx1A and SLAM enable the fusion of incoming membrane vesicles into the expanding membranes. In the absence of SLAM, membrane vesicles accumulate in the apical cytoplasm. However, the accumulating vesicles contain Rab11, a marker for recycling endosomes, suggesting that the incoming Golgi-derived secretory vesicles either first fuse into the apical pla
High Cleavage Efficiency of a 2A Peptide Derived from Porcine Teschovirus-1 in Human Cell Lines, Zebrafish and Mice
Jin Hee Kim,Sang-Rok Lee,Li-Hua Li,Hye-Jeong Park,Jeong-Hoh Park,Kwang Youl Lee,Myeong-Kyu Kim,Boo Ahn Shin,Seok-Yong Choi
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018556
Abstract: When expression of more than one gene is required in cells, bicistronic or multicistronic expression vectors have been used. Among various strategies employed to construct bicistronic or multicistronic vectors, an internal ribosomal entry site (IRES) has been widely used. Due to the large size and difference in expression levels between genes before and after IRES, however, a new strategy was required to replace IRES. A self-cleaving 2A peptide could be a good candidate to replace IRES because of its small size and high cleavage efficiency between genes upstream and downstream of the 2A peptide. Despite the advantages of the 2A peptides, its use is not widespread because (i) there are no publicly available cloning vectors harboring a 2A peptide gene and (ii) comprehensive comparison of cleavage efficiency among various 2A peptides reported to date has not been performed in different contexts. Here, we generated four expression plasmids each harboring different 2A peptides derived from the foot-and-mouth disease virus, equine rhinitis A virus, Thosea asigna virus and porcine teschovirus-1, respectively, and evaluated their cleavage efficiency in three commonly used human cell lines, zebrafish embryos and adult mice. Western blotting and confocal microscopic analyses revealed that among the four 2As, the one derived from porcine teschovirus-1 (P2A) has the highest cleavage efficiency in all the contexts examined. We anticipate that the 2A-harboring cloning vectors we generated and the highest efficiency of the P2A peptide we demonstrated would help biomedical researchers easily adopt the 2A technology when bicistronic or multicistronic expression is required.
Two Separate Interfaces between the Voltage Sensor and Pore Are Required for the Function of Voltage-Dependent K+ Channels
Seok-Yong Lee,Anirban Banerjee,Roderick MacKinnon
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1000047
Abstract: Voltage-dependent K+ (Kv) channels gate open in response to the membrane voltage. To further our understanding of how cell membrane voltage regulates the opening of a Kv channel, we have studied the protein interfaces that attach the voltage-sensor domains to the pore. In the crystal structure, three physical interfaces exist. Only two of these consist of amino acids that are co-evolved across the interface between voltage sensor and pore according to statistical coupling analysis of 360 Kv channel sequences. A first co-evolved interface is formed by the S4-S5 linkers (one from each of four voltage sensors), which form a cuff surrounding the S6-lined pore opening at the intracellular surface. The crystal structure and published mutational studies support the hypothesis that the S4-S5 linkers convert voltage-sensor motions directly into gate opening and closing. A second co-evolved interface forms a small contact surface between S1 of the voltage sensor and the pore helix near the extracellular surface. We demonstrate through mutagenesis that this interface is necessary for the function and/or structure of two different Kv channels. This second interface is well positioned to act as a second anchor point between the voltage sensor and the pore, thus allowing efficient transmission of conformational changes to the pore's gate.
Two Separate Interfaces between the Voltage Sensor and Pore Are Required for the Function of Voltage-Dependent K+ Channels
Seok-Yong Lee equal contributor,Anirban Banerjee equal contributor,Roderick MacKinnon
PLOS Biology , 2009, DOI: 10.1371/journal.pbio.1000047
Abstract: Voltage-dependent K+ (Kv) channels gate open in response to the membrane voltage. To further our understanding of how cell membrane voltage regulates the opening of a Kv channel, we have studied the protein interfaces that attach the voltage-sensor domains to the pore. In the crystal structure, three physical interfaces exist. Only two of these consist of amino acids that are co-evolved across the interface between voltage sensor and pore according to statistical coupling analysis of 360 Kv channel sequences. A first co-evolved interface is formed by the S4-S5 linkers (one from each of four voltage sensors), which form a cuff surrounding the S6-lined pore opening at the intracellular surface. The crystal structure and published mutational studies support the hypothesis that the S4-S5 linkers convert voltage-sensor motions directly into gate opening and closing. A second co-evolved interface forms a small contact surface between S1 of the voltage sensor and the pore helix near the extracellular surface. We demonstrate through mutagenesis that this interface is necessary for the function and/or structure of two different Kv channels. This second interface is well positioned to act as a second anchor point between the voltage sensor and the pore, thus allowing efficient transmission of conformational changes to the pore's gate.
Differential Immune Responses to Segniliparus rotundus and Segniliparus rugosus Infection and Analysis of Their Comparative Virulence Profiles
Jong-Seok Kim, Woo Sik Kim, Keehoon Lee, Choul-Jae Won, Jin Man Kim, Seok-Yong Eum, Won-Jung Koh, Sung Jae Shin
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0059646
Abstract: Two closely related bacterial species, Segniliparus rotundus and Segniliparus rugosus, have emerged as important human pathogens, but little is known about the immune responses they elicit or their comparative pathophysiologies. To determine the virulence and immune responses of the two species, we compared their abilities to grow in phagocytic and non-phagocytic cells. Both species maintained non-replicating states within A549 epithelial cells. S. rugosus persisted longer and multiplied more rapidly inside murine bone marrow-derived macrophages (BMDMs), induced more pro-inflammatory cytokines, and induced higher levels of macrophage necrosis. Activation of BMDMs by both species was mediated by toll-like receptor 2 (TLR2), followed by mitogen-activated protein kinases (MAPK) and nuclear factor κB (NF-κB) signaling pathways, indicating a critical role for TLR2 in Segniliparus-induced macrophage activation. S. rugosus triggered faster and stronger activation of MAPK signaling and IκB degradation, indicating that S. rugosus induces more pro-inflammatory cytokines than S. rotundus. Multifocal granulomatous inflammations in the liver and lung were observed in mice infected with S. rugosus, but S. rotundus was rapidly cleared from all organs tested within 15 days post-infection. Furthermore, S. rugosus induced faster infiltration of innate immune cells such as neutrophils and macrophages to the lung than S. rotundus. Our results suggest that S. rugosus is more virulent and induces a stronger immune response than S. rotundus.
Metaplastic ossification in the cartilage of the bronchus of a patient with chronic multi-drug resistant tuberculosis: a case report
Seok-Yong Eum, Ji-Hye Kong, Bo-Young Jeon, Sang-Nae Cho, Jhingook Kim, Laura E Via, Clifton E Barry III, Won-Jung Koh
Journal of Medical Case Reports , 2010, DOI: 10.1186/1752-1947-4-156
Abstract: We report the case of a 41-year-old Asian man from Korea with chronic multi-drug resistant tuberculosis with a rare focus of bone formation from the cartilage of a bronchus subtending an active cavity. The patient had a large multi-lobed, thick-walled cavitary tuberculosis lesion in his left upper lobe. Severe infiltration of his lymphocytes and epithelioid cells, along with some giant cells and neutrophils, was observed in the patient's bronchial wall. Desquamated bronchial epithelium and acid-fast bacilli were found inside his bronchus. A small focus of bony metaplasia was found in the cartilage of his bronchial wall. Histopathological examination confirmed calcification and showed hematopoietic cells forming in his marrow cavity.Chronic inflammation in the lungs of our patient, caused by underlying tuberculosis, probably played a role in the development of osseous metaplasia from the associated cartilage of the bronchial wall.Pulmonary ossification is rare and usually identified and diagnosed post-mortem by the pathologist. This phenomenon has been observed in pulmonary fibrosis and in some chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD) [1-5]. We report here an unusual case of bone formation in the bronchial wall upon examination of surgically resected lung tissue from a patient with multi-drug resistant tuberculosis (MDR-TB) with chronic inflammation of the bronchial wall.A 41-year-old Asian man from Korea was referred for treatment of MDR-TB. He had been previously treated for MDR-TB with second-line anti-TB drugs for six years at another institution. Despite this treatment, his sputum smear and culture examinations were persistently positive. He used to smoke. He had a white blood cell count of 6260/μL, an erythrocyte sedimentation rate of 60 mm/h, and his C-reactive protein levels were elevated at 0.65 mg/dL. His human immunodeficiency virus antibody test was negative. On his chest X-ray examination, two cavities were observ
Synthesis of SiOx Nano-Powders Using a Microwave Plasma Torch at Atmospheric Pressure  [PDF]
Dong Hun Shin, Yun Seok Choi, Dong Jin Ku, Yong Cheol Hong, Bong Ju Lee
Soft Nanoscience Letters (SNL) , 2016, DOI: 10.4236/snl.2016.62003
Abstract: The silicon oxide nano-powders (SiOx-NPs) were obtained in an atmospheric microwave plasma torch using a gas-phase silicon tetrachloride (SiCl4) with N2 and H2. The gas-phase SiCl4 was injected with H2 gas into the microwave plasma torch generated by N2 and air swirl gas, and then the dark brown powders were deposited on the inner wall of a quartz tube. The sample was analyzed by an X-ray photoelectron spectroscopy (XPS), a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and an X-ray diffraction (XRD). The average size and oxidation x values of synthesized SiOx-NPs were approximately 230 nm and 0.91, respectively. Furthermore, the volumetric charge capacity is 1127 mAh/g and has 89.2% retention after 100 cycles.
Intrauterine midgut volvulus without malrotation: Diagnosis from the coffee bean sign
Jun Seok Park, Seong Jae Cha, Beom Gyu Kim, Yong Seok Kim, Yoo Shin Choi, In Taik Chang, Gwang Jun Kim, Woo Seok Lee, Gi Hyeon Kim
World Journal of Gastroenterology , 2008,
Abstract: Fetal midgut volvulus is quite rare, and most cases are associated with abnormalities of intestinal rotation or fixation. We report a case of midgut volvulus without malrotation, associated with a meconium pellet, during the gestation period. This 2.79 kg, 33-wk infant was born via a spontaneous vaginal delivery caused by preterm labor. Prenatal ultrasound showed dilated bowel loops with the appearance of a ‘coffee bean sign’. This patient had an unusual presentation with a distended abdomen showing skin discoloration. An emergency laparotomy revealed a midgut volvulus and a twisted small bowel, caused by complicated meconium ileus. Such nonspecific prenatal radiological signs and a low index of suspicion of a volvulus during gestation might delay appropriate surgical management and result in ischemic necrosis of the bowel. Preterm labor, specific prenatal sonographic findings (for example, the coffee bean sign) and bluish discoloration of the abdominal wall could suggest intrauterine midgut volvulus requiring prompt surgical intervention.
An ultrahigh-Q microsphere laser based on the evanescent-wave-coupled gain
Yong-Seok Choi,Hee-Jong Moon,Sang Wook Kim,Kyungwon An
Physics , 2001,
Abstract: We have demonstrated an ultrahigh-Q whispering-gallery-mode (WGM) microsphere laser based on the evanescent-wave-coupled gain. Dye molecules outside the sphere near the equator were excited, resulting in WGM lasing in the lowest radial mode order. The loaded quality factor of the lasing WGM was 8(2)\times 10^9, the highest ever achieved in the microlaser.
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