Brain Korea

Seoul, South Korea

Brain Korea

Seoul, South Korea
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Kim S.,Kyungpook National University | Rahman M.,Kyungpook National University | Seol S.Y.,Kyungpook National University | Yoon S.S.,Brain Korea | And 2 more authors.
Applied and Environmental Microbiology | Year: 2012

We isolated a new lytic Pseudomonas aeruginosa phage that requires type IV pili for infection. PA1Ø has a broad bactericidal spectrum, covering Gram-positive and Gram-negative bacteria, and can eradicate biofilm cells. PA1Ø may be developed as a therapeutic agent for biofilm-related mixed infections with P. aeruginosa and Staphylococcus aureus. © 2012, American Society for Microbiology.

Jang J.H.,Kyungpook National University | Jung J.,Brain Korea | Jung J.,Yonsei University | Kim A.R.,Seoul National University | And 6 more authors.
Audiology and Neurotology | Year: 2014

Mutations in the SLC26A4 gene, which encodes pendrin, cause congenital hearing loss as a manifestation of Pendred syndrome (PS) with an iodide organification defect or nonsyndromic enlarged vestibular aqueduct (NSEVA, DFNB4). There have been reports of differences between PS and NSEVA, including their auditory phenotypes and molecular genetic bases. For appropriate genetic diagnosis and counseling, it is important to functionally characterize SLC26A4 variants. In this study, we identified and evaluated a novel null mutation of SLC26A4 and report our method of assessing the pathogenic potential of mutations in SLC26A4, one of the most frequent causative genes of deafness in humans. A 3-year-old female with progressive sensorineural hearing loss and her parents were recruited. They underwent clinical, audiological, radiological and genetic evaluations, which revealed that the female patient had an enlarged vestibular aqueduct and an incomplete partition type II anomaly in the cochlea bilaterally. Sanger sequencing of the SLC26A4 gene was also performed. For a confirmatory genetic diagnosis, we first characterized the anion/base exchange ability of mutant pendrin products in HEK 293 cells and, if necessary, evaluated whether the mutant pendrin traffics to the plasma membrane in COS-7 cells. We also expressed a null function mutant, p.H723R, and a previously documented polymorphism, p.P542R, as controls. The pure tone average was 66 dB HL in the right ear and 75 dB HL in the left ear. Sequencing of SLC26A4 revealed a known pathogenic mutation (p.H723R) and a novel missense variant (p.V510D) as a compound heterozygote. When we expressed the p.V510D mutant pendrin in mammalian cells, the rate constants for Cl-/HCO3-exchange were 10.96 ± 4.79% compared with those of wild-type pendrin. This figure was comparable to that of p.H723R, indicating p.V510D to be another pathogenic mutation with a null function. The p.V510D pendrin product was shown to be entrapped in the endoplasmic reticulum (ER) at 24-30 h after transfection, and not trafficked to the plasma membrane in COS-7 cells, suggesting retention in the ER and abnormal trafficking as the pathogenic mechanism. This was similar to p.H723R, which is a null function founder mutant in this population but is a candidate variant for future drug therapy to rescue the abnormal cell trafficking. Impaired cellular trafficking due to ER retention and abolished exchange activity of the newly detected p.V510D indicates the pathogenic potential of this variant. These missense variants may be good candidate variants for drug therapy if the intrinsic exchange activity is not damaged by the change. © 2014 S. Karger AG, Basel.

Gee H.Y.,Brain Korea | Kim C.K.,Inje University | Kim S.W.,Brain Korea | Lee J.H.,Brain Korea | And 3 more authors.
Journal of Korean Medical Science | Year: 2010

Cystic fibrosis (CF) is an autosomal recessive disorder usually found in populations of white Caucasian descent. CF is caused by mutations in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. A 5-yr-old Korean girl was admitted complaining of coughing and greenish sputum. Chest radiographs and computed tomographic (CT) scan revealed diffuse bronchiectasis in both lungs. The patient had chronic diarrhea and poor weight gain, and the abdominal pancreaticobiliary CT scan revealed atrophy of the pancreas. Finally, CF was confirmed by the repeated analysis of the quantitative pilocarpine iontophoresis test. The chloride concentration of sweat samples taken from both forearms of the pateint was an average of 88.7 mM/L (normal value <40 mM/L). After a comprehensive search for mutations in the CFTR gene, the patient was found to carry the non-synonymous L441P mutation in one allele. Molecular physiologic analysis of the L441P mutation of CFTR revealed that the L441P mutation completely abolished the CFTR Cl-channel activity by disrupting proper protein folding and membrane trafficking of CFTR protein. These results confirmed the pathogenicity of the L441P mutation of CFTR circulating in the Korean population. The possibility of CF should be suspected in patients with chronic bronchiectasis, although the frequency of CF is relatively rare in East Asia. © 2010 The Korean Academy of Medical Sciences.

Kim D.-S.,Brain Korea | Lee J.S.,Brain Korea | Leem J.W.,Brain Korea | Huh Y.J.,Brain Korea | And 7 more authors.
Stem Cell Reviews and Reports | Year: 2010

Our analyses of three human induced pluripotent stem cell (hiPSC) and six human embryonic stem cell (hESC) lines showed marked variability in differentiation potential into specific lineages, which often hampers their differentiation into specific cell types or cell lineages of interest. Simultaneous inhibition of both Activin/Nodal and BMP pathways with small molecules, SB431542 and dorsomorphin (DM), respectively, promoted significant neural differentiation from all human pluripotent stem cell (hPSC) lines tested, regardless of their differentiation propensity. On the contrary, differentiation into other cell lineages and the number of undifferentiated cells were significantly reduced after differentiation by the dual inhibition. These results demonstrate that innate differentiation propensity of hPSCs could be overcome, at least in part, by modulation of intracellular signaling pathways, resulting in efficient generation of desirable cell types, such as neural cells. © 2010 Springer Science+Business Media, LLC.

Oh Y.T.,Brain Korea | Lee K.-M.,Brain Korea | Bari W.,Brain Korea | Raskin D.M.,Marian University at Indianapolis | And 2 more authors.
Journal of Biological Chemistry | Year: 2015

When V. cholerae encounters nutritional stress, it activates (p)ppGpp-mediated stringent response. The genes relA and relV are involved in the production of (p)ppGpp, whereas the spoT gene encodes an enzyme that hydrolyzes it. Herein, we show that the bacterial capability to produce (p)ppGpp plays an essential role in glucose metabolism. The V. cholerae mutants defective in (p)ppGpp production (i.e. ΔrelAΔrelV and ΔrelAΔrelVΔspoT mutants) lost their viability because of uncontrolled production of organic acids, when grown with extra glucose. In contrast, the ΔrelAΔspoT mutant, a (p)ppGpp overproducer strain, exhibited better growth in the presence of the same glucose concentration. An RNA sequencing analysis demonstrated that transcriptions of genes consisting of an operon for acetoin biosynthesis were markedly elevated in N16961, a seventh pandemic O1 strain, but not in its (p)ppGpp0 mutant during glucose-stimulated growth. Transposon insertion in acetoin biosynthesis gene cluster resulted in glucose-induced loss of viability of the ΔrelAΔspoT mutant, further suggesting the crucial role of acetoin production in balanced growth under glucose-rich environments. Additional deletion of the aphA gene, encoding a negative regulator for acetoin production, failed to rescue the (p)ppGpp0 mutant from the defective glucose-mediated growth, suggesting that (p)ppGpp-mediated acetoin production occurs independent of the presence of AphA. Overall, our results reveal that (p)ppGpp, in addition to its well known role as a stringent response mediator, positively regulates acetoin production that contributes to the successful glucose metabolism and consequently the proliferation of V. cholerae cells under a glucose-rich environment, a condition that may mimic the human intestine. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc. Published in the U.S.A.

Lee H.J.,Brain Korea | Lee E.J.,Brain Korea | Seo M.,Yonsei University
Yonsei Medical Journal | Year: 2016

Purpose: Apoptosis of vascular endothelial cells is a type of endothelial damage that is associated with the pathogenesis of cardiovascular diseases such as atherosclerosis. Heterotrimeric GTP-binding proteins (G proteins), including the alpha 12 subunit of G protein (Gα12), have been found to modulate cellular proliferation, differentiation, and apoptosis of numerous cell types. However, the role of Gα12 in the regulation of apoptosis of vascular cells has not been elucidated. We investigated the role of Gα12 in serum withdrawal-induced apoptosis of human umbilical vein endothelial cells (HUVECs) and its underlying mechanisms. Materials and Methods: HUVECs were transfected with Gα12 small-interfering RNA (siRNA) to knockdown the endogenous Gα12 expression and were serum-deprived for 6 h to induce apoptosis. The apoptosis of HUVECs were assessed by Western blotting and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The expressions of microRNAs were analyzed by quantitative real-time PCR. Results: Knockdown of Gα12 with siRNA augmented the serum withdrawal-induced apoptosis of HUVECs and markedly repressed the expression of microRNA-155 (miR-155). Serum withdrawal-induced apoptosis of HUVECs was inhibited by the overexpression of miR-155 and increased significantly due to the inhibition of miR-155. Notably, the elevation of miR-155 expression prevented increased apoptosis of Gα12-deficient HUVECs. Conclusion: From these results, we conclude that Gα12 protects HUVECs from serum withdrawal-induced apoptosis by retaining miR-155 expression. This suggests that Gα12 might play a protective role in vascular endothelial cells by regulating the expression of microRNAs. © Yonsei University College of Medicine 2016.

Cho S.O.,Brain Korea | Lim J.W.,Yonsei University | Kim K.H.,Brain Korea | Kim H.,Yonsei University
Digestive Diseases and Sciences | Year: 2010

Helicobacter pylori (H. pylori) is an important risk factor for chronic gastritis, peptic ulcer, and gastric cancer. The genetic differences of H. pylori isolates play a role in the clinical outcome of the infection. Inflammatory genes including cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) are involved in H. pylori gastritis. Transcription factor AP-1 is composed of c-Fos and c-Jun and mediates inflammation and carcinogenesis. Ras acts as a regulator for AP-1 activation in various cells. We investigated whether H. pylori in a Korean isolate (HP99), a cagA +, vacA + strain, induces the expression of c-Fos and c-Jun for AP-1 activation to induce COX-2 and iNOS and whether HP99-induced expressions of COX-2 and iNOS are mediated by Ras and AP-1, determined by the expressions of c-Fos and c-Jun, in gastric epithelial AGS cells, using transfection with mutant genes for Ras (ras N-17) and c-Jun (TAM-67). As a result, HP99 induced the expression of c-Fos and c-Jun and the expressions of COX-2 and iNOS in AGS cells. Transfection with mutant genes for Ras or c-Jun suppressed HP99-induced expressions of COX-2 and iNOS in AGS cells. In conclusion, H. pylori in a Korean isolate induces the expression of COX-2 and iNOS via AP-1 activation, which may be mediated by Ras and the expression of c-Fos and c-Jun in gastric epithelial cells. © 2009 Springer Science+Business Media, LLC.

PubMed | Brain Korea
Type: | Journal: Scientific reports | Year: 2015

Pseudomonas aeruginosa establishes airway infections in Cystic Fibrosis patients. Here, we investigate the molecular interactions between P. aeruginosa and airway mucus secretions (AMS) derived from the primary cultures of normal human tracheal epithelial (NHTE) cells. PAO1, a prototype strain of P. aeruginosa, was capable of proliferating during incubation with AMS, while all other tested bacterial species perished. A PAO1 mutant lacking PA4834 gene became susceptible to AMS treatment. The PA4834 mutant was grown in AMS supplemented with 100M ferric iron, suggesting that the PA4834 gene product is involved in iron metabolism. Consistently, intracellular iron content was decreased in the mutant, but not in PAO1 after the AMS treatment. Importantly, a PAO1 mutant unable to produce both pyoverdine and pyochelin remained viable, suggesting that these two major siderophore molecules are dispensable for maintaining viability during incubation with AMS. The PA4834 mutant was regrown in AMS amended with 100M nicotianamine, a phytosiderophore whose production is predicted to be mediated by the PA4836 gene. Infectivity of the PA4834 mutant was also significantly compromised in vivo. Together, our results identify a genetic element encoding a novel iron acquisition system that plays a previously undiscovered role in P. aeruginosa airway infection.

PubMed | Brain Korea
Type: Journal Article | Journal: The Journal of biological chemistry | Year: 2012

Vibrio cholerae is a gram-negative bacterium that causes cholera. Although the pathogenesis caused by this deadly pathogen takes place in the intestine, commonly thought to be anaerobic, anaerobiosis-induced virulence regulations are not fully elucidated. Anerobic growth of the V. cholerae strain, N16961, was promoted when trimethylamine N-oxide (TMAO) was used as an alternative electron acceptor. Strikingly, cholera toxin (CT) production was markedly induced during anaerobic TMAO respiration. N16961 mutants unable to metabolize TMAO were incapable of producing CT, suggesting a mechanistic link between anaerobic TMAO respiration and CT production. TMAO reductase is transported to the periplasm via the twin arginine transport (TAT) system. A similar defect in both anaerobic TMAO respiration and CT production was also observed in a N16961 TAT mutant. In contrast, the abilities to grow on TMAO and to produce CT were not affected in a mutant of the general secretion pathway. This suggests that V. cholerae may utilize the TAT system to secrete CT during TMAO respiration. During anaerobic growth with TMAO, N16961 cells exhibit green fluorescence when stained with 2,7-dichlorofluorescein diacetate, a specific dye for reactive oxygen species (ROS). Furthermore, CT production was decreased in the presence of an ROS scavenger suggesting a positive role of ROS in regulating CT production. When TMAO was co-administered to infant mice infected with N16961, the mice exhibited more severe pathogenic symptoms. Together, our results reveal a novel anaerobic growth condition that stimulates V. cholerae to produce its major virulence factor.

PubMed | Yonsei University, Brain Korea, South Korea Institute for Immunology and Immunological Diseases and University of Tsukuba
Type: Journal Article | Journal: Antimicrobial agents and chemotherapy | Year: 2014

Pseudomonas aeruginosa, a Gram-negative bacterium of clinical significance, produces elastase as a predominant exoprotease. Here, we screened a library of chemical compounds currently used for human medication and identified diethylene triamine penta-acetic acid (DTPA, pentetic acid) as an agent that suppresses the production of elastase. Elastase activity found in the prototype P. aeruginosa strain PAO1 was significantly decreased when grown with a concentration as low as 20 M DTPA. Supplementation with Zn(2+) or Mn(2+) ions restored the suppressive effect of DTPA, suggesting that the DTPA-mediated decrease in elastase activity is associated with ion-chelating activity. In DTPA-treated PAO1 cells, transcription of the elastase-encoding lasB gene and levels of the Pseudomonas quinolone signal (PQS), a molecule that mediates P. aeruginosa quorum sensing (QS), were significantly downregulated, reflecting the potential involvement of the PQS QS system in DTPA-mediated elastase suppression. Biofilm formation was also decreased by DTPA treatment. When A549 alveolar type II-like adenocarcinoma cells were infected with PAO1 cells in the presence of DTPA, A549 cell viability was substantially increased. Furthermore, the intranasal delivery of DTPA to PAO1-infected mice alleviated the pathogenic effects of PAO1 cells in the animals. Together, our results revealed a novel function for a known molecule that may help treat P. aeruginosa airway infection.

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