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RISS 인기검색어
- 검색키워드
- 저자 : Yong-Sung Juhnn (검색결과 17 건)
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Kim, Eui-Jun,Juhnn, Yong-Sung American Society for Biochemistry and Molecular Bi 2015 The Journal of biological chemistry Vol.290 No.15
<P>The cAMP signaling system regulates various cellular functions, including metabolism, gene expression, and death. Sirtuin 6 (SIRT6) removes acetyl groups from histones and regulates genomic stability and cell viability. We hypothesized that cAMP modulates SIRT6 activity to regulate apoptosis. Therefore, we examined the effects of cAMP signaling on SIRT6 expression and radiation-induced apoptosis in lung cancer cells. cAMP signaling in H1299 and A549 human non-small cell lung cancer cells was activated via the expression of constitutively active G alpha(s) plus treatment with prostaglandin E2 (PGE2), isoproterenol, or forskolin. The expression of sirtuins and signaling molecules were analyzed by Western blotting. Activation of cAMP signaling reduced SIRT6 protein expression in lung cancer cells. cAMP signaling increased the ubiquitination of snrr6 protein and promoted its degradation. Treatment with MG132 and inhibiting PKA with H89 or with a dominant-negative PKA abolished the cAMP-mediated reduction in SIRT6 levels, Treatment with PGE2 inhibited c-Raf activation by increasing inhibitory phosphorylation at Ser-259 in a PKA-dependent manner, thereby inhibiting downstream MEK-ERK signaling. Inhibiting ERK with inhibitors or with dominant-negative ERKs reduced SIRT6 expression, whereas activation of ERK by constitutively active MEK abolished the SIRT6-depleting effects of PGE2. cAMP signaling also augmented radiation-induced apoptosis in lung cancer cells. This effect was abolished by exogenous expression of SIRT6. It is concluded that cAMP signaling reduces SIRT6 expression by promoting its ubiquitin-protea-some-dependent degradation, a process mediated by the PKA-dependent inhibition of the Raf-MEK-ERK pathway. Reduced SIRT6 expression mediates the augmentation of radiation-induced apoptosis by cAMP signaling in lung cancer cells.</P>
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Lee, Eun Young,Seo, MiRan,Juhnn, Yong-Sung,Kim, Jeong Yeon,Hong, Yoo Jin,Lee, Yun Jong,Lee, Eun Bong,Song, Yeong Wook BioMed Central 2011 Arthritis research & therapy Vol.13 No.3
<P><B>Introduction</B></P><P>IFN-gamma inducible protein-10 (CXCL10), a member of the CXC chemokine family, and its receptor CXCR3 contribute to the recruitment of T cells from the blood stream into the inflamed joints and have a crucial role in perpetuating inflammation in rheumatoid arthritis (RA) synovial joints. Recently we showed the role of CXCL10 on receptor activator of nuclear factor kappa-B ligand (RANKL) expression in an animal model of RA and suggested the contribution to osteoclastogenesis. We tested the effects of CXCL10 on the expression of RANKL in RA synoviocytes and T cells, and we investigated which subunit of CXCR3 contributes to RANKL expression by CXCL10.</P><P><B>Methods</B></P><P>Synoviocytes derived from RA patients were kept in culture for 24 hours in the presence or absence of TNF-α. CXCL10 expression was measured by reverse transcriptase polymerase chain reaction (RT-PCR) of cultured synoviocytes. Expression of RANKL was measured by RT-PCR and western blot in cultured synoviocytes with or without CXCL10 and also measured in Jurkat/Hut 78 T cells and CD4+ T cells in the presence of CXCL10 or dexamethasone. CXCL10 induced RANKL expression in Jurkat T cells was tested upon the pertussis toxin (PTX), an inhibitor of Gi subunit of G protein coupled receptor (GPCR). The synthetic siRNA for Gαi<SUB>2 </SUB>was used to knock down gene expression of respective proteins.</P><P><B>Results</B></P><P>CXCL10 expression in RA synoviocytes was increased by TNF-α. CXCL10 slightly increased RANKL expression in RA synoviocytes, but markedly increased RANKL expression in Jurkat/Hut 78 T cell or CD4+ T cell. CXCL10 augmented the expression of RANKL by 62.6%, and PTX inhibited both basal level of RANKL (from 37.4 ± 16.0 to 18.9 ± 13.0%) and CXCL10-induced RANKL expression in Jurkat T cells (from 100% to 48.6 ± 27.3%). Knock down of Gα<SUB>i2 </SUB>by siRNA transfection, which suppressed the basal level of RANKL (from 61.8 ± 17.9% to 31.1 ± 15.9%) and CXCL10-induced RANKL expression (from 100% to 53.1 ± 27.1%) in Jurkat T cells, is consistent with PTX, which inhibited RANKL expression.</P><P><B>Conclusions</B></P><P>CXCL10 increased RANKL expression in CD4+ T cells and it was mediated by Gα<SUB>i </SUB>subunits of CXCR3. These results indicate that CXCL10 may have a potential role in osteoclastogenesis of RA synovial tissue and subsequent joint erosion.</P>
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So-Young Kim,Miran Seo,Jung-Min Oh,Eun-Ah Cho,Yong-Sung Juhnn 생화학분자생물학회 2007 Experimental and molecular medicine Vol.39 No.5
Heterotrimeric GTP-binding proteins (G proteins) transduce extracellular signals into intracellular sig-nals by activating effector molecules including ad-enylate cyclases that catalyze cAMP formation, and thus regulate various cellular responses such as me-tabolism, proliferation, and apoptosis. cAMP signaling izing radiation-induced apoptosis, but however, the protective mechanism is not clear. Therefore, this study aimed to investigate the signaling molecules and the mechanism mediating the anti-apoptotic action of cAMP signaling system in radiation-induced apopto-sis. Stable expression of a constitutively active mutant of Gαs (GαsQL) protected gamma ray-induced apop-tosis which was asesed by analysis of the cleavages of PARP, caspase-9, and caspase-3 and cytochrome C GαsQL repressed the gamma ray-induced down-regu-lation of Bcl-xL protein, but transfection of Bcl-xL siRNA increased the gamma ray-induced apoptosis and abolished the anti-apoptotic effect of GαsQL. GαsQL decreased the degradation rate of Bcl-xL pro-tein, and it also restrained the decrease in Bcl-xL mRNA by increasing the stability following ionizing irradia-tion. Furthermore, prostaglandin E2 that activates Gαs and the protective effect was abolished by treatment with prostanoid receptor antagonist specific to EP2/4R subtype. Moreover, specific agonists for adenosine A1 receptor that inhibits cAMP signaling pathway aug-mented gamma ray-induced apoptosis. From this study, it is concluded that Gαs-cAMP signaling system can protect SH-SY5Y cells from gamma ray-induced apoptosis partly by restraining down-regulation of Bcl-xL expression, suggesting that radiation-induced apoptosis can be modulated by GPCR ligands to improve the efficiency of radiation therapy.
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STAT3 inhibits the degradation of HIF-1α by pVHL-mediated ubiquitination
Joo Eun Jung,Hong Sook Kim,Chang Seok Lee,Yong-Jae Shin,김용연,Gyeong-Hoon Kang,Tae-You Kim,Yong-Sung Juhnn,Sung-Joon Kim,Jong-Wan Park,Sang-Kyu Ye,Myung-Hee Chung 생화학분자생물학회 2008 Experimental and molecular medicine Vol.40 No.5
Hypoxia-inducible factor 1α (HIF-1α) is rapidly degraded by the ubiquitin-proteasome pathway under normoxic conditions. Ubiquitination of HIF-1α is mediated by interaction with von Hippel-Lindau tumor suppressor protein (pVHL). In our previous report, we found that hypoxia-induced active signal transducer and activator of transcription3 (STAT3) accelerated the accumulation of HIF-1α protein and prolonged its half-life in solid tumor cells. However, its specific mechanisms are not fully understood. Thus, we examined the role of STAT3 in the mechanism of pVHL-mediated HIF-1α stability. We found that STAT3 interacts with C-terminal domain of HIF-1α and stabilizes HIF-1α by inhibition of pVHL binding to HIF-1α. The binding between HIF-1α and pVHL, negative regulator of HIF-1α stability, was interfered dose-dependently by overexpressed constitutive active STAT3. Moreover, we found that the enhanced HIF-1α protein levels by active STAT3 are due to decrease of poly-ubiquitination of HIF-1α protein via inhibition of interaction between pVHL and HIF-1α. Taken together, our results suggest that STAT3 decreases the pVHL-mediated ubiquitination of HIF-1α through competition with pVHL for binding to HIF-1 α, and then stabilizes HIF-1α protein levels. Hypoxia-inducible factor 1α (HIF-1α) is rapidly degraded by the ubiquitin-proteasome pathway under normoxic conditions. Ubiquitination of HIF-1α is mediated by interaction with von Hippel-Lindau tumor suppressor protein (pVHL). In our previous report, we found that hypoxia-induced active signal transducer and activator of transcription3 (STAT3) accelerated the accumulation of HIF-1α protein and prolonged its half-life in solid tumor cells. However, its specific mechanisms are not fully understood. Thus, we examined the role of STAT3 in the mechanism of pVHL-mediated HIF-1α stability. We found that STAT3 interacts with C-terminal domain of HIF-1α and stabilizes HIF-1α by inhibition of pVHL binding to HIF-1α. The binding between HIF-1α and pVHL, negative regulator of HIF-1α stability, was interfered dose-dependently by overexpressed constitutive active STAT3. Moreover, we found that the enhanced HIF-1α protein levels by active STAT3 are due to decrease of poly-ubiquitination of HIF-1α protein via inhibition of interaction between pVHL and HIF-1α. Taken together, our results suggest that STAT3 decreases the pVHL-mediated ubiquitination of HIF-1α through competition with pVHL for binding to HIF-1 α, and then stabilizes HIF-1α protein levels.
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Yoon Jung Choi,So-Young Kim,Jung-Min Oh,Yong-Sung Juhnn 생화학분자생물학회 2009 Experimental and molecular medicine Vol.41 No.8
Stimulatory heterotrimeric GTP-binding proteins (Gs protein) stimulate cAMP generation in response to various signals, and modulate various cellular phenomena such as proliferation and apoptosis. This study aimed to investigate the effect of Gs proteins on gamma ray-induced apoptosis of lung cancer cells and its molecular mechanism, as an attempt to develop a new strategy to improve the therapeutic efficacy of gamma radiation. Expression of constitutively active mutant of the α subunit of Gs (GαsQL) augmented gamma ray-induced apoptosis via mitochondrial dependent pathway when assessed by clonogenic assay, FACS analysis of PI stained cells, and western blot analysis of the cytoplasmic translocation of cytochrome C and the cleavage of caspase-3 and ploy(ADP-ribose) polymerase (PARP) in H1299 human lung cancer cells. GαsQL up-regulated the Bak expression at the levels of protein and mRNA. Treatment with inhibitors of PKA (H89), SP600125 (JNK inhibitor), and a CRE-decoy blocked GαsQL-stimulated Bak reporter luciferase activity. Expression of GαsQL increased basal and gamma ray-induced luciferase activity of cAMP response element binding protein (CREB) and AP-1, and the binding of CREB and AP-1 to Bak promoter. Furthermore, prostaglandin E2, a Gαs activating signal, was found to augment gamma ray-induced apoptosis, which was abolished by treatment with a prostanoid receptor antagonist. These results indicate that Gαs augments gamma ray-induced apoptosis by up-regulation of Bak expression via CREB and AP-1 in H1299 lung cancer cells, suggesting that the efficacy of radiotherapy of lung cancer may be improved by modulating Gs signaling pathway. Stimulatory heterotrimeric GTP-binding proteins (Gs protein) stimulate cAMP generation in response to various signals, and modulate various cellular phenomena such as proliferation and apoptosis. This study aimed to investigate the effect of Gs proteins on gamma ray-induced apoptosis of lung cancer cells and its molecular mechanism, as an attempt to develop a new strategy to improve the therapeutic efficacy of gamma radiation. Expression of constitutively active mutant of the α subunit of Gs (GαsQL) augmented gamma ray-induced apoptosis via mitochondrial dependent pathway when assessed by clonogenic assay, FACS analysis of PI stained cells, and western blot analysis of the cytoplasmic translocation of cytochrome C and the cleavage of caspase-3 and ploy(ADP-ribose) polymerase (PARP) in H1299 human lung cancer cells. GαsQL up-regulated the Bak expression at the levels of protein and mRNA. Treatment with inhibitors of PKA (H89), SP600125 (JNK inhibitor), and a CRE-decoy blocked GαsQL-stimulated Bak reporter luciferase activity. Expression of GαsQL increased basal and gamma ray-induced luciferase activity of cAMP response element binding protein (CREB) and AP-1, and the binding of CREB and AP-1 to Bak promoter. Furthermore, prostaglandin E2, a Gαs activating signal, was found to augment gamma ray-induced apoptosis, which was abolished by treatment with a prostanoid receptor antagonist. These results indicate that Gαs augments gamma ray-induced apoptosis by up-regulation of Bak expression via CREB and AP-1 in H1299 lung cancer cells, suggesting that the efficacy of radiotherapy of lung cancer may be improved by modulating Gs signaling pathway.
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Interaction between Neuronal Depolarization and MK-801 in SH-SY5Y Cells and the Rat Cortex
김예니,Miran Seo,이윤일,So-Young Kim,Eun-Ah Cho,김세현,Yong-Min Ahn,Ung-Gu Kang,김용식,Yong-Sung Juhnn 대한신경정신의학회 2008 PSYCHIATRY INVESTIGATION Vol.5 No.2
Objective: The interaction between MK-801, a model of psychosis and KCl-induced depolarization or electroconvulsive shock (ECS), a therapeutic model of electroconvulsive therapy (ECT), was investigated in SH-SY5Y cells and the rat frontal cortex. Methods: SH-SY5Y cells were pretreated with 1 μM MK-801 for 15 min, followed by cotreatment with 100 mM KCl for 5 min. MK-801 was reintroduced after the KCl was washed out, and the samples were incubated before harvesting. For the experiments in rats, male Sprague-Dawley rats were treated with MK-801 followed by ECS. Immunoblot analyses of glycogen synthase kinase 3β (GSK3β) (Ser9), AKT (Ser473) and extracellular legulated kinase (ERK)1/2 in SH-SY5Y cells and the rat frontal cortex were performed. Results: KCl-induced neuronal depolarization resulted in the transient dephosphorylation of AKT (Ser473) and GSK3β (Ser9), followed by increased phosphorylation of the enzymes in SH-SY5Y cells. Cotreatment with MK-801 and KCl inhibited the initial dephosphorylation of AKT and GSK3β produced by KCl-induced neuronal depolarization. Similarly, ECS resulted in the transient dephosphorylation of AKT (Ser473) and GSK3β (Ser9), whereas cotreatment with MK-801 inhibited the initial dephosphorylation of AKT (Ser473) and GSK3β (Ser9) produced by ECS in the rat frontal cortex. No significant interaction was observed between MK-801 and KCl in the dephosphorylation of ERK1/2. Conclusion: These results suggest that an antagonistic interplay between MK-801 and neuronal depolarization by KCl or ECS is involved the regulation of AKT (Ser473) and GSK3β (Ser9) phosphorylation.
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