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Dive into the research topics where Junseo Oh is active.

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Featured researches published by Junseo Oh.


Gut | 2012

StellaTUM: current consensus and discussion on pancreatic stellate cell research

Mert Erkan; Guido Adler; Minoti V. Apte; Max G. Bachem; Malte Buchholz; Sönke Detlefsen; Irene Esposito; Helmut Friess; Thomas M. Gress; Hans Joerg Habisch; Rosa F. Hwang; Robert Jaster; Jörg Kleeff; Günter Klöppel; Claus Kordes; Craig D. Logsdon; Atsushi Masamune; Christoph W. Michalski; Junseo Oh; Phoebe A. Phillips; Massimo Pinzani; Carolin Reiser-Erkan; Hidekazu Tsukamoto; Jeremy S. Wilson

The field of pancreatic stellate cell (PSC) biology is very young, as the essential in-vitro tools to study these cells (ie, methods to isolate and culture PSC) were only developed as recently as in 1998. Nonetheless, there has been an exponential increase in research output in this field over the past decade, with numerous research groups around the world focusing their energies into elucidating the biology and function of these cells. It is now well established that PSC are responsible for producing the stromal reaction (fibrosis) of two major diseases of the pancreas—chronic pancreatitis and pancreatic cancer. Despite exponentially increasing data, the methods for studying PSC remain variable. Although within individual laboratories methods are consistent, different methodologies used by various research groups make it difficult to compare results and conclusions. This article is not a review article on the functions of PSC. Instead, members of the Pancreatic Star Alliance (http://www.pancreaticstaralliance.com) discuss here and consolidate current knowledge, to outline and delineate areas of consensus or otherwise (eg, with regard to methodological approaches) and, more importantly, to identify essential directions for future research. Hepatic stellate cells (HSC) were first described by Karl von Kupffer in 1876; however, similar cells in the pancreas were first observed in the 1980s.1–3 In 1998, Apte et al 4 and Bachem et al 5 isolated and cultured PSC.4 5 In the normal pancreas, PSC are located in close proximity to the basal aspect of pancreatic acinar cells. In sections immunostained for the marker desmin (a cytoskeletal protein), quiescent PSC can be seen as cells with a central cell body and long cytoplasmic projections extending along the base of adjacent acinar cells similar to that of pericytes in the mammary gland. …


Journal of Biological Chemistry | 2006

Shp-1 Mediates the Antiproliferative Activity of Tissue Inhibitor of Metalloproteinase-2 in Human Microvascular Endothelial Cells

Dong Wan Seo; Hongmei Li; Cheng Kui Qu; Junseo Oh; Young Sik Kim; Tere Diaz; Beiyang Wei; Jeung Whan Han; William G. Stetler-Stevenson

The tissue inhibitors of metalloproteinases (TIMPs) regulate matrix metalloproteinase activity required for cell migration/invasion associated with cancer progression and angiogenesis. TIMPs also modulate cell proliferation in vitro and angiogenesis in vivo independent of their matrix metalloproteinase inhibitory activity. Here, we show that TIMP-2 mediates G1 growth arrest in human endothelial cells through de novo synthesis of the cyclin-dependent kinase inhibitor p27Kip1. TIMP-2-mediated inhibition of Cdk4 and Cdk2 activity is associated with increased binding of p27Kip1 to these complexes in vivo. Protein-tyrosine phosphatase inhibitors or expression of a dominant negative Shp-1 mutant ablates TIMP-2 induction of p27Kip1. Finally, angiogenic responses to fibroblast growth factor-2 and vascular endothelial growth factor-A in “motheaten viable” Shp-1-deficient mice are resistant to TIMP-2 inhibition, demonstrating that Shp-1 is an important negative regulator of angiogenesis in vivo.


Oncogene | 2005

The membrane-anchored MMP-regulator RECK is a target of myogenic regulatory factors

Michiko Echizenya; Shunya Kondo; Rei Takahashi; Junseo Oh; Satoshi Kawashima; Hitoshi Kitayama; Chiaki Takahashi; Makoto Noda

The membrane-anchored MMP-regulator RECK is down regulated in many solid tumors; the extent of RECK down regulation correlates with poor prognosis. Forced expression of RECK in tumor cells results in suppression of angiogenesis, invasion, and metastasis. Studies on the roles and the mechanisms of regulation of the RECK gene during normal development may therefore yield important insights into how the malignant behaviors of tumor cells arise and how they can be controlled. Our previous studies indicate that mice lacking RECK die around E10.5 with reduced tissue integrity. In the present study, we have found that in later stage wild-type embryos, RECK is abundantly expressed in skeletal muscles, especially in the areas where the myoblast differentiation factor MRF4 is expressed. Consistent with this finding, the RECK-promoter is activated by MRF4 in cultured cells. In contrast, a myoblast determination factor MyoD suppresses the RECK-promoter. Myoblastic cells lacking RECK expression give rise to myotubes at higher efficiency than the cells expressing RECK, indicating that RECK suppresses myotube formation. These findings suggest that MyoD down regulates RECK to facilitate myotube formation, whereas MRF4 up regulates RECK to promote other aspects of myogenesis that require extracellular matrix integrity.


Oncogene | 2006

TIMP-2 upregulates RECK expression via dephosphorylation of paxillin tyrosine residues 31 and 118

Junseo Oh; Terre Diaz; Beiyang Wei; Hyeujin Chang; Makoto Noda; William G. Stetler-Stevenson

We previously demonstrated that TIMP-2 increases the association of Crk with C3G and via subsequent activation of Rap1 enhances the expression of RECK, a membrane-anchored MMP inhibitor. In the present study, we investigate the mechanism of how the TIMP-2 signal is transduced from the α3β1 integrin receptor to the Crk-C3G-Rap1 molecular complex. TIMP-2 treatment of human microvascular endothelial cells (hMVECs) increased the phosphorylation levels of Src at Tyr-527, the negative regulatory site, through enhanced association of Src with Csk. This results in the reduction of Src kinase activity and dephosphorylation of paxillin at Tyr-31/118, the target sites for Src kinase phosphorylation and also the binding sites for the downstream effector Crk. Such TIMP-2 effects accompany the disassembly of paxillin-Crk-DOCK180 molecular complex and, in turn, Rac1 inactivation. On the contrary, levels of paxillin-Crk-C3G complex formation are not reduced, rather slightly increased, which is consistent with our previous finding. Therefore, TIMP-2-mediated inhibition of Src kinase activity leads to the signaling switch from Rac1 to Rap1, thereby leading to enhanced RECK expression.


Gut | 2009

Formation of vitamin A lipid droplets in pancreatic stellate cells requires albumin

Nayoung Kim; Wonbaek Yoo; Jaeseob Lee; Ho Kim; Hong Sik Lee; Young Sik Kim; Dong-Uk Kim; Junseo Oh

Objective: Quiescent pancreatic stellate cells (PSCs) store vitamin A as cytoplasmic lipid droplets, and, when activated by profibrogenic stimuli, they transform into myofibroblast-like cells characterised by the loss of vitamin A droplets. Activation of stellate cells is central to fibrogenesis, but the mechanism for the formation of vitamin A droplets and its relationship to stellate cell activation remain unclear. Methods: With use of cultured PSCs, an attempt was made to characterise the function of albumin endogenously expressed in stellate cells. Results: Albumin is endogenously expressed in quiescent PSCs, localised in cytoplasmic lipid droplets, and its levels are markedly reduced after stellate cell activation. Continuous albumin expression in stellate cells is sufficient to maintain their fat-storing phenotype even after cell passages and renders cells resistant to the activating effects of transforming growth factor β (TGFβ). Forced expression of albumin in PSCs after passage 2 (activated PSCs) induced the re-appearance of lipid droplets and phenotypic changes, which were previously reported with retinol treatment. Retinol increases albumin synthesis in activated PSCs and the suppression of albumin expression using small interfering RNA (siRNA) abolishes retinol-induced effects. Conclusions: The data demonstrate a novel role for albumin in the formation of cytoplasmic vitamin A lipid droplets in stellate cells, and suggest that albumin may have a direct influence on stellate cell activation.


Journal of Cell Science | 2007

Dual effects of the membrane-anchored MMP regulator RECK on chondrogenic differentiation of ATDC5 cells

Shunya Kondo; Chisa Shukunami; Yoko Morioka; Naoya Matsumoto; Rei Takahashi; Junseo Oh; Tadao Atsumi; Akihiro Umezawa; Akira Kudo; Hitoshi Kitayama; Yuji Hiraki; Makoto Noda

Extracellular matrix (ECM) undergoes continuous remodeling during mammalian development. Although involvement of matrix metalloproteinases (MMPs) in ECM degradation has been well documented, how this process is regulated to allow proper ECM accumulation remains unclear. We previously showed the involvement of a membrane-anchored MMP regulator, RECK (reversion-inducing cysteine-rich protein with Kazal motifs), in vascular development in mice. Here we report that Reck mRNA can be detected in developing cartilage in E13.5∼16.5 mouse embryos and is progressively upregulated during differentiation of a chondrogenic cell line ATDC5 in vitro. In the early phase of ATDC5 differentiation, RECK expression stays low, multiple MMPs are upregulated, and there is ECM degradation at the sites of cellular condensation. In the later phase, RECK is upregulated inside the expanding cartilaginous nodules where type II collagen is accumulated while active ECM degradation persists along the rim of the nodules. Constitutive RECK expression suppressed initial cellular condensation, whereas RECK knockdown suppressed the later ECM accumulation in the cartilaginous nodules. These results suggest that RECK expression at the right place (in the core of the nodules) and at the right time (only in the later phase) is important for proper chondrogenesis and that RECK, together with MMPs, plays a crucial role in regulating dynamic processes of tissue morphogenesis.


BMC Developmental Biology | 2010

Involvement of the Reck tumor suppressor protein in maternal and embryonic vascular remodeling in mice

Ediriweera P. S. Chandana; Yasuhiro Maeda; Akihiko Ueda; Hiroshi Kiyonari; Naoko Oshima; Mako Yamamoto; Shunya Kondo; Junseo Oh; Rei Takahashi; Yoko Yoshida; Satoshi Kawashima; David B. Alexander; Hitoshi Kitayama; Chiaki Takahashi; Yasuhiko Tabata; Tomoko Matsuzaki; Makoto Noda

BackgroundDevelopmental angiogenesis proceeds through multiple morphogenetic events including sprouting, intussusception, and pruning. Mice lacking the membrane-anchored metalloproteinase regulator Reck die in utero around embryonic day 10.5 with halted vascular development; however, the mechanisms by which this phenotype arises remain unclear.ResultsWe found that Reck is abundantly expressed in the cells associated with blood vessels undergoing angiogenesis or remodelling in the uteri of pregnant female mice. Some of the Reck-positive vessels show morphological features consistent with non-sprouting angiogenesis. Treatment with a vector expressing a small hairpin RNA against Reck severely disrupts the formation of blood vessels with a compact, round lumen. Similar defects were found in the vasculature of Reck-deficient or Reck conditional knockout embryos.ConclusionsOur findings implicate Reck in vascular remodeling, possibly through non-sprouting angiogenesis, in both maternal and embyornic tissues.


Biochemical and Biophysical Research Communications | 2010

Albumin mediates PPAR-γ or C/EBP-α-induced phenotypic changes in pancreatic stellate cells

Nayoung Kim; Soyoung Choi; Chae-Seung Lim; Hong Sik Lee; Junseo Oh

Activation of quiescent hepatic stellate cells (HSCs) into myofibroblast-like cells is a key event of liver fibrosis, and adipogenic transcription factors, PPAR-gamma and C/EBP-alpha, reverse HSC activation. As albumin was reported to maintain the quiescent phenotype of stellate cells, we examined whether it plays a role in PPAR-gamma and C/EBP-alpha-mediated effects. Pancreatic stellate cells (PSCs) were isolated from rat pancreas and used in their culture-activated phenotype. Forced expression of PPAR-gamma or C/EBP-alpha in PSCs increased albumin mRNA and protein levels by >2.5-fold, which is accompanied with increased C/EBP-beta binding to albumin promoter. PPAR-gamma and C/EBP-alpha also induced a phenotypic switch from activated to quiescent cells and, interestingly, suppression of albumin using short-hairpin RNA (shRNA) blocked their effects. Therefore, our findings suggest that albumin may be a downstream effector of PPAR-gamma and C/EBP-alpha in PSCs and that it can be an attractive molecular target for anti-fibrotic therapies.


Journal of Cellular Biochemistry | 2008

TGF‐β signaling preserves RECK expression in activated pancreatic stellate cells

Hong Sik Lee; Chae-Seung Lim; Jung Eun Lee; Nayoung Kim; Sangsu Bang; Hojae Lee; Bon Hong Min; Gilhong Park; Makoto Noda; William G. Stetler-Stevenson; Junseo Oh

Activated pancreatic stellate cells (PSCs) play a pivotal role in the pathogenesis of pancreatic fibrosis, but the detailed mechanism for dysregulated accumulation of extracellular matrix (ECM) remains unclear. Cultured rat PSCs become activated by profibrogenic mediators, but these mediators failed to alter the expression levels of matrix metalloproteinases (MMPs) to the endogenous tissue inhibitors of metalloproteinases (TIMPs). Here, we examined the expression of RECK, a novel membrane‐anchored MMP inhibitor, in PSCs. Although RECK mRNA levels were largely unchanged, RECK protein expression was barely detected at 2, 5 days after plating PSCs, but appeared following continued in vitro culture and cell passage which result in PSC activation. When PSCs at 5 days after plating (PSCs‐5d) were treated with pepstatin A, an aspartic protease inhibitor, or TGF‐β1, a profibrogenic mediator, RECK protein was detected in whole cell lysates. Conversely, Smad7 overexpression or suppression of Smad3 expression in PSCs after passage 2 (PSCs‐P2) led to the loss of RECK protein expression. These findings suggest that RECK is post‐translationally processed in pre‐activated PSCs but protected from proteolytic degradation by TGF‐β signaling. Furthermore, collagenolytic activity of PSCs‐5d was greatly reduced by TGF‐β1, whereas that of PSCs‐P2 was increased by anti‐RECK antibody. Increased RECK levels were also observed in cerulein‐induced acute pancreatitis. Therefore, our results suggest for the first time proteolytic processing of RECK as a mechanism regulating RECK activity, and demonstrate that TGF‐β signaling in activated PSCs may promote ECM accumulation via a mechanism that preserves the protease inhibitory activity of RECK. J. Cell. Biochem. 104: 1065–1074, 2008.


Biochemical and Biophysical Research Communications | 2010

Albumin expression is required for adipocyte differentiation of 3T3-L1 cells.

Wonbaek Yoo; Jaeseob Lee; Sangeun Park; Young Sik Kim; Chae-Seung Lim; Eul-Sik Yoon; Gangmin Hur; Junseo Oh

We have previously demonstrated that albumin is directly involved in the formation of cytoplasmic lipid droplets in pancreatic stellate cells and may act as a downstream effector of adipogenic transcription factors, PPAR-gamma and C/EBP-alpha. Here, we investigated the role of albumin in adipocyte differentiation using 3T3-L1 cells. Albumin expression was significantly increased at later stages of adipocyte differentiation, which was accompanied with increased C/EBP-beta binding to albumin promoter. Suppression of albumin expression using short-hairpin RNA (shRNA) during differentiation led to a considerable reduction in lipid droplet formation, whereas albumin overexpression was stimulatory. Furthermore, point mutation in its fatty acid-binding sites inhibited lipid droplet formation. Consistent with these in vitro finding, Nagase analbuminemic rats displayed reduced fat accumulation. Therefore, our findings suggest that albumin may play a distinct role in adipocyte differentiation by promoting lipid accumulation.

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