Ji Soo Chae

Korea University, Seoul, Seoul, South Korea

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Publications (7)57.64 Total impact

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    ABSTRACT: The Mammalian STE20-like kinase-1 (MST1), a multifunctional serine-threonine kinase in mammalian cells, has been recently implicated in the mediation of oxidative stress-induced signaling processes that lead to cell death. However, the molecular mechanism by which oxidative stress induces the stimulation of MST1 remains unclear. In the present study, we found that thioredoxin-1 physically associated with MST1 in intact cells, and that this interaction was abolished by H(2)O(2). Thioredoxin-1, by binding to the SARAH domain of MST1, inhibited the homodimerization and autophosphorylation of MST1, thereby preventing its activation. Furthermore, TNF-α prevented the physical interaction between thioredoxin-1 and MST1 and promoted the homodimerization and activation of MST1. The effect of TNF-α on MST1 activation was reversed by the reducing agent N-acetyl-L-cysteine. Taken together, our results suggest that thioredoxin-1 functions as a molecular switch to turn off the oxidative stress-induced activation of MST1.
    Free Radical Biology and Medicine 10/2012; · 5.27 Impact Factor
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    ABSTRACT: Son of sevenless 1 (SOS1) is a dual guanine nucleotide exchange factor (GEF) that activates the guanosine triphosphatases Rac1 and Ras, which mediate signaling initiated by peptide growth factors. In this paper, we show that CIIA is a new binding partner of SOS1. CIIA promoted the SOS1-Rac1 interaction and inhibited the SOS1-Ras interaction. Furthermore, CIIA promoted the formation of an SOS1-EPS8 complex and SOS1-mediated Rac1 activation, whereas it inhibited SOS1-mediated activation of Ras. Transforming growth factor β (TGF-β) up-regulated the expression of CIIA and thereby promoted the association between CIIA and SOS1 in A549 human lung adenocarcinoma cells. Depletion of CIIA in these cells by ribonucleic acid interference inhibited the TGF-β-induced interaction between SOS1 and EPS8, activation of Rac1, and cell migration. Together, these results suggest that CIIA mediates the TGF-β-induced activation of SOS1-Rac1 signaling and cell migration in A549 cells. They further show that CIIA functions as a molecular switch for the GEF activity of SOS1, directing this activity toward Rac1.
    The Journal of Cell Biology 10/2011; 195(3):377-86. · 10.82 Impact Factor
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    ABSTRACT: Microglia, the resident macrophages of the mammalian central nervous system, migrate to sites of tissue damage or infection and become activated. Although the persistent secretion of inflammatory mediators by the activated cells contributes to the pathogenesis of various neurological disorders, most activated microglia eventually undergo apoptosis through the process of activation-induced cell death (AICD). The molecular mechanism of AICD, however, has remained unclear. Here, we show that Daxx and mammalian Ste20-like kinase-1 (MST1) mediate apoptosis elicited by interferon-γ (IFN-γ) in microglia. IFN-γ upregulated the expression of Daxx, which in turn mediated the homodimerization, activation, and nuclear translocation of MST1 and apoptosis in microglial cells. Depletion of Daxx or MST1 by RNA interference also attenuated IFN-γ-induced cell death in primary rat microglia. Furthermore, the extent of IFN-γ-induced death of microglia in the brain of MST1-null mice was significantly reduced compared with that apparent in wild-type mice. Our results thus highlight new functions of Daxx and MST1 that they are the key mediators of microglial cell death initiated by the proinflammatory cytokine IFN-γ.
    The EMBO Journal 01/2011; 30(12):2465-76. · 9.82 Impact Factor
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    ABSTRACT: Calcium and integrin binding protein 1 (CIB1) is a Ca(2+)-binding protein of 22 kDa that was initially identified as a protein that interacts with integrin alpha(IIb). Although it interacts with various proteins and has been implicated in diverse cellular functions, the molecular mechanism by which CIB1 regulates intracellular signaling networks has remained unclear. We now show that, by targeting apoptosis signal-regulating kinase 1 (ASK1), CIB1 negatively regulates stress-activated MAPK signaling pathways. CIB1 was thus shown to bind to ASK1, to interfere with the recruitment of TRAF2 to ASK1, and to inhibit the autophosphorylation of ASK1 on threonine-838, thereby blocking ASK1 activation. Furthermore, CIB1 mitigated apoptotic cell death initiated either by TNF-alpha in breast cancer MCF7 cells or by 6-hydroxydopamine (6-OHDA) in dopaminergic cells. Ca(2+) influx induced by membrane depolarization reversed the inhibitory effect of CIB1 on 6-OHDA-induced ASK1 activation and cell death in dopaminergic neurons. These observations thus suggest that CIB1 functions as a Ca(2+)-sensitive negative regulator of ASK1-mediated signaling events.
    Proceedings of the National Academy of Sciences 09/2009; 106(41):17389-94. · 9.81 Impact Factor
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    ABSTRACT: Epithelial-mesenchymal transition (EMT) and the acquisition of invasive potential are key events in tumor progression. We now show that CIIA, originally identified as an anti-apoptotic protein, induces the EMT and promotes cell migration and invasion. Ectopic expression of CIIA induced down-regulation of E-cadherin and claudin-1 as well as up-regulation of N-cadherin in MDCK cells. It also disrupted the differentiated epithelial morphology of MDCK cells grown in three-dimensional Matrigel cultures as well as increased the migration and invasion of MDCK cells in vitro. Furthermore, depletion of endogenous CIIA by RNA interference inhibited the migration and invasion of HeLa cells, and this inhibition was abolished by RNA interference-mediated depletion of claudin-1. These results suggest that CIIA functions as an inducer of cell invasion, and this effect is mediated, at least in part, through down-regulation of claudin-1.
    Biochemical and Biophysical Research Communications 08/2009; 387(3):548-52. · 2.28 Impact Factor
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    ABSTRACT: Serum- and glucocorticoid-inducible protein kinase 1 (SGK1) has been implicated in diverse cellular activities including the promotion of cell survival. The molecular mechanism of the role of SGK1 in protection against cellular stress has remained unclear, however. We have now shown that SGK1 inhibits the activation of SEK1 and thereby negatively regulates the JNK signaling pathway. SGK1 was found to physically associate with SEK1 in intact cells. Furthermore, activated SGK1 mediated the phosphorylation of SEK1 on serine 78, resulting in inhibition of the binding of SEK1 to JNK1, as well as to MEKK1. Replacement of serine 78 of SEK1 with alanine abolished SGK1-mediated SEK1 inhibition. Oxidative stress upregulated SGK1 expression, and depletion of SGK1 by RNA interference potentiated the activation of SEK1 induced by oxidative stress in Rat2 fibroblasts. Moreover, such SGK1 depletion prevented the dexamethasone-induced increase in SGK1 expression, as well as the inhibitory effects of dexamethasone on paclitaxel-induced SEK1-JNK signaling and apoptosis in MDA-MB-231 breast cancer cells. Together, our results suggest that SGK1 negatively regulates stress-activated signaling through inhibition of SEK1 function.
    The EMBO Journal 08/2007; 26(13):3075-85. · 9.82 Impact Factor
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    ABSTRACT: The transmembrane protein Notch is cleaved by gamma-secretase to yield an active form, Notch intracellular domain (Notch-IC), in response to the binding of ligands, such as Jagged. Notch-IC contributes to the regulation of a variety of cellular events, including cell fate determination during embryonic development as well as cell growth, differentiation, and survival. We now show that Notch1-IC suppresses the scaffold activity of c-Jun N-terminal kinase (JNK)-interacting protein 1 (JIP1) in the JNK signaling pathway. Notch1-IC physically associated with the JNK binding domain of JIP1 and thereby interfered with the interaction between JIP1 and JNK. JIP1 mediated the activation of JNK1 induced by glucose deprivation in mouse embryonic fibroblasts, and ectopic expression of Notch1-IC inhibited JNK activation and apoptosis triggered by glucose deprivation. Taken together, these findings suggest that Notch1-IC negatively regulates the JNK pathway by disrupting the scaffold function of JIP1.
    Proceedings of the National Academy of Sciences 11/2005; 102(40):14308-13. · 9.81 Impact Factor