11:10-12:00, Rm 103

Cell: differentiation, division and deathC-17-51Activation of p53 suppresses WID expression to induce apoptosis inU2OS cellsKyoung-Won Ko, Yun-Jung Choe, Sun-Young Lee and Ho-Shik KimDepartment of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul 137-701,KoreaWT1-induced inhibitor of dishevelled (WID), also known as CXXC5, belongs to a recentlyidentified gene family characterized by a CXXC motif. Although it was reported thatCXXC5 is involved in inhibition of WNT signaling and modulation of retinoid-inducedleukemic cell differentiation, the functions of CXXC5 in p53-induced apoptosis have notbeen clarified, yet. The expression level of WID was higher in p53-null SAOS cells thanthat in wild-type p53-containing U2OS cells. Whereas activation of p53 by doxorubicin(Dox), a DNA-damaging reagent, and nutlin-3, a MDM2 antagonist, diminished WIDexpression in U2OS cells, overexpression of p53 caused attenuation of WID expressionin SAOS cells. Interestingly, knockdown of WID by WID siRNA in U2OS cells inducedaccumulation of sub-G1 population associated with caspase-3 activation and PARP1cleavage. The pan-caspase inhibitor, z-VAD-fmk, completely abolished cell deathinduced by WID knockdown. Moreover, U2OS cells transfected with WID siRNAexhibited augmentation of Dox or nutlin-3-induced cell death. Collectively, it can beconcluded that WID expression is essential for the cell survival and suppressed by p53,contributing to induction of apoptosis.C-17-55Monensin sensitizes TRAIL-resistant glioma cells to TRAIL-inducedapoptosis via induction of reactive oxygen species and ER stressYou Jung Kang, Mi Jin Yoon, In Young Kim, Ju Ahn Lee and Kyeong Sook ChoiDepartment of Molecular Science & Technology, Institute for Medical Sciences, Ajou UniversitySchool of Medicine, Suwon 443-749, KoreaAlthough tumor necrosis factor-related apoptosis-induced ligand (TRAIL) is preferentiallycytotoxic to cancer cells over normal cells, many cancer cells are resistant to TRAIL. Inthis study, we investigated the potential use of monensin, the monocarboxylic acidionophore, as a TRAIL sensitizer in TRAIL-resistant glioma cells. Combined treatment ofglioma cells with subtoxic doses of monensin and TRAIL induced a rapid apoptosis, butnot in astrocytes, suggesting that this combined treatment may propose an attractivestrategy for safely treating resistant gliomas. We found that monensin increased ROSlevels and the cell death induced by monensin plus TRAIL was effectively blocked bypretreatment with antioxidants. Furthermore, monensin increased the protein levels ofCHOP and DR5. Knockdown of CHOP or DR5 expression inhibited the cell death bymonensin plus TRAIL. Taken together, monensin-induced oxidative stress as well asCHOP-mediated DR5 up-regulation may contribute to amplification of TRAIL-inducedapoptotic signaling in glioma cells.C-17-52The role of SIRT2 in autophagy associated with NFκB regulationMyung Ho Kor, Jung Sun Min, Moon-gi Chae, Mi-jee Kim, Ji Ae Kim, Sung-minKang, Jiyoung Park and Jeong Keun AhnDepartment of Microbiology, Chungnam National University, Daejeon 305-764, KoreaAutophagy is a catabolic process involving in various cellular events including aging, celldeath, and starvation response. Autophagy is the degradation pathway of cellularcomponents by the lysosomal machinery and characterized by the formation ofautophagosomes, which fuse with lysosomes to form autolysosomes. Recently, it hasbeen reported that the NFκB family member p65/RelA up-regulates the expression ofBeclin 1 which is an autophagy regulator. NFκB is a transcription factor that is inactivatedby IκBα, one member of IκB family. Phosphorylation of IκBαprotein by IKK complex isfollowed by ubiquitination and proteasomal degradation. We found that SIRT2, one of thesirtuins, deacetylates HSP90 and reduces its stability. HSP90 has been found to be anovel regulator of the IKK complex. In this study, we report that SIRT2 decreases thelevel of IKK complex and inhibits NFκB activity. In addition, NFκB is localized to thenucleus when SIRT2 expression is repressed. Autophagosome formation induced by p65is also decreased by SIRT2. These results suggest that SIRT2 suppresses NFκB activityby reducing the stability of IKK complex and down-regulates autophagy.C-17-56Mitochondrial Ca2+ influx critically contributes to curcumin-inducedparaptosis in malignant breast cancer cellsMi Jin Yoon, Eun Hee Kim, Taeg Kyu Kwon, Kyeong Sook ChoiDepartment of Molecular Science & Technology, Institute for Medical Sciences, Ajou UniversitySchool of Medicine, Suwon, KoreaPreviously, we have shown that curcumin demonstrates an anti-cancer effect onmalignant breast cancer cells, but not on normal breast cells, via induction of paraptosisaccompanying the dilation of mitochondria and ER. Since mitochondria and ER are majorreservoirs of intracellular Ca2+, we investigated whether perturbation of Ca2+homeostasis by curcumin is involved in the induction of paraptosis. Both the cytosolic andmitochondrial Ca2+ levels were dramatically increased in curcumin-treated MDA-MB435S cells. Interestingly, pretreatment with the inhibitor of the mitochondrial calciumuniporter significantly blocked all the paraptotic events induced by curcumin, including theincrease in mitochondrial superoxide and Ca2+ levels, activation of ERK and JNK, Alixdownregulation, proteasomal dysfunction, dilation of mitochondria and ER, andsubsequent cell death. In addition, we found that while treatment with the proteasomeinhibitor induced ER dilation without an evident sign of cell death in MDA-MB 435S cells,co-treatment with CGP-37157 and the proteasome inhibitor dramatically sensitized thesecells to paraptotic cell death. Taken together, these results suggest that mitochondrialCa2+ influx plays an initial and critical signal for curcumin-induced paraptosis.C-17-53Salubrinal overcomes bortezomib-mediated resistance in glioma cellsvia aggravation of proteotoxicityIn Young Kim, Eun Hee Kim, Mi Jin Yoon and Kyeong Sook ChoiDepartment of Molecular Science & Technology, Institute for Medical Sciences, Ajou UniversitySchool of Medicine, Suwon 443-749, KoreaProteasome inhibitors (PIs), such as bortezomib, have demonstrated an effective anticancereffect on multiple myeloma and leukemic cells. However, the anti-cancer effect ofthe PI is limited in solid tumors, including gliomas. We found that combined treatment withsalubrinal, an inhibitor of eIF2a dephosphatase, with PI significantly increased cell deathin glioma cells, but not in astrocytes. We found that co-treatment with salubrinalenhanced PI-mediated impairment of proteasome and upregulation of CHOP, Noxa andDR5 protein levels, leading to activation of caspase-3. In addition, combined treatmentwith salubrinal and PI induced the dilation of endoplasmic reticulum and dispersion ofaggresomes. Taken together, these results suggest that salubrinal may contribute toovercome resistance to PI via aggravation of proteotoxicity in glioma cells.C-17-57Ssu72 is a cohesin-binding protein that regulates the resolution of sisterchromatid arm cohesionHyun-Soo Kim¹ , ², Geun-Hyoung Ha¹ , ²and Chang-Woo Lee¹ , ²¹Department of Molecular Cell Biology, ²Center for Molecular Medicine, Samsung BiomedicalResearch Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, KoreaIn vertebrates, sister chromatid cohesion is dissolved in a stepwise manner: Mostcohesins are removed from chromosome arms via a process that requires Plk1, aurora Band Wapl, while a minor amount of cohesin, found preferentially at the centromere, iscleaved by separase following its activation by the anaphase-promotingcomplex/cyclosome. In this study, we identified hsSsu72 as a Rad21-binding proteinusing yeast two-hybrid assay. Additional experiments revealed that Ssu72 directlyinteracts with Rad21 and SA2 in vitro and in vivo, and associates with mitotic sisterchromatids. Interestingly, depletion of Ssu72 phosphatase activity caused prematuresister chromatid separation, whereas the overexpression of Ssu72 yielded highresistance to the resolution of sister chromatid cohesion. Further studies showed thatSsu72 regulates the cohesion of chromosome arms but not centromeres. Thus, our studyprovides important new evidence suggesting that Ssu72 is a novel cohesin-regulatoryprotein capable of regulating cohesion between sister chromatid arms.208 Korean Society for Biochemistry and Molecular Biology