11:10-12:00, Rm 103

Cell: signal transductionL-18-40Role of CD38 for angiotensin II-induced reactive oxygen speciesproduction in hepatic stellate cellsSo-Young Rah¹, Seon-Young Kim¹, and Uh-Hyun Kim¹ , ²¹Department of Biochemistry and ²the Institute of Cardiovascular Research, Chonbuk NationalUniversity Medical School, Jeonju 561-182, KoreaAngiotensin II (Ang II) mediates the regulation of extracellular matrix via reactive oxygenspecies (ROS) and intracellular Ca2+ increase; both are activators of hepatic stellate cells(HSCs) which play a critical role in hepatic fibrosis. We have previously demonstratedthat Ang II-induced NAADP/cADPR productions via CD38 activation evoke long lastingCa2+ rises in HSCs, which contributes to liver fibrosis. In this study, we investigatedwhether CD38 is involved in Ang II-mediated ROS production of HSCs. HSCs isolatedfrom CD38 knockout mice attenuated Ang II-induced ROS production compared to HSCsfrom wild type mice. Treatment of HSCs with NAD(P)H oxidase inhibitors significantlyreduced Ang II-induced ROS production and Ca2+ increase. Preincubation of anantagonistic cADPR analog, 8-bromo-cADPR, abolished the ROS production by Ang II.Application of exogenous cADPR to HSCs significantly increased ROS production.Moreover, Ang II or cADPR-induced ROS production was not observed in the absence ofextracellular Ca2+, suggesting that Ca2+ influx is required for the ROS production by Angll. Taken together, our data suggest that Ang II-induced elevation of [Ca2+]i via CD38activation is essential for Ang II-induced ROS production in HSCs.L-18-43Recruitment of beclin1 to lipid rafts by prion protein is essential for theamyloid beta-induced autophagy activationJihoon Nah, Jong-Ok Pyo and Yong-Keun JungSchool of Biological Sciences, College of Natural Sciences, Seoul National University, 599 Gwanakro,Gwanak-gu, Seoul 151-747, KoreaAn increasing research on autophagy provides overwhelming evidence for its molecularsignaling. Beclin1, one of the most-studied mammalian autophagy-related protein, acts aspart of a core complex of a class III phosphatidylinositol-3 kinase complex with Vps34 andappears to interact with various additional binding partners. Although much is knownabout Beclin 1-interacting partners, the mechanism of Beclin1-mediated regulation ofthese cellular functions remains cryptic. Prion protein (PRNP) has been implicated invarious types of neurodegenerative dysfunctions including familial Creutzfeldt-Jakobdisease in human. Here we show that PRNP mediates amyloid beta (Aβ)-inducedautophagy through interaction with Beclin1. Aβ-induced autophagy activation wasinhibited in cultured primary neuron from PRNP knockout (Prnp0/0) compared to wildtype control mice. Immunoprecipitation assays elucidated that PRNP interacts with aBeclin1 and this interaction was mediated through N-terminal domain of PRNP. Further,this interaction promotes subcellular localization of Beclin1 to lipid-raft in plasmamembrane. Therefore, we define a novel role of PRNP that regulates autophagy viaBeclin1 and adjusts subcellular localization of Beclin1 to lipid raft.L-18-41Dual regulatory functions of DP1 in Wnt/β-catenin signalingWan-tae Kim¹ , *, Hyunjoon Kim² , *, Vladimir L. Katanaev³, Seung Joon Lee², TohruIshitani⁴, Boksik Cha¹, Jin-Kwan Han² , # and Eek-hoon Jho¹ , #¹Department of Life science, University of Seoul, Seoul 130-743, Korea, ²Division of Molecularand Life sciences, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784,Korea, ³Department of Biology, University of Konstanz, Konstanz 78457, Germany, ⁴Division ofCell Regulation Systems, Kyushu University, Higashi-ku, Fukuoka, JapanDP1, a dimerization partner protein of the transcription factor E2F, is known to inhibit Wnt/β-catenin signaling along with E2F, although the function of DP1 itself was not wellcharacterized. Here, we present a novel dual regulatory mechanism of Wnt/β-cateninsignaling by DP1 independent from E2F. DP1 negatively regulates Wnt/β-cateninsignaling by inhibiting Dvl-Axin interaction and by enhancing poly-ubiquitination of β-catenin. In contrast, DP1 positively modulates the signaling upon Wnt stimulation, viaincreasing cytosolic β-catenin and antagonizing the kinase activity of NLK. In Xenopusembryos, DP1 exerts both positive and negative roles in Wnt/β-catenin signaling duringanteroposterior neural patterning. From subcellular localization analyses, we suggest thatthe dual roles of DP1 in Wnt/β-catenin signaling are endowed by differentialnucleocytoplasmic localizations. We propose that these dual functions of DP1 canpromote and stabilize biphasic Wnt-on and Wnt-off states in response to a gradualgradient of Wnt/β-catenin signaling to determine differential cell fates.L-18-44Mxi1 regulates cell proliferation through insulin-like growth factorbinding protein-3Je Yeong Ko, Kyung Hyun Ryu and Jong Hoon Park*Department of Biological Science, Sookmyung Women’s University, Seoul 140-742, KoreaMxi1, a member of the Myc-Max-Mad network, is an antagonist of the c-Myc oncogeneand is associated with excessive cell proliferation. Abnormal cell proliferation is observedin organs of Mxi1-/- mice. However, the Mxi1-reltaed mechanism of proliferation isunclear. The present study utilized microarray analysis using Mxi1 mouse embryonicfibroblasts (MEFs) to identify genes associated with cell proliferation. Among thesegenes, insulin-like growth factor binding protein-3 (IGFBP-3) was selected as a candidategene for real-time PCR to ascertain whether IGFBP-3 expression is regulated by Mxi1.Expression of IGFBP-3 was decreased in Mxi1-/- MEFs and Mxi1-/- mice, and the genewas regulated by Mxi1 in Mxi1 MEFs. Furthermore, proliferation pathways related toIGFBP-3 were regulated in Mxi1-/- mice. To determine the effect of Mxi1 inactivation onthe induction of cell proliferation, a proliferation assay is performed in both Mxi1 MEFsand Mxi1 mice. Cell viability was regulated by Mxi1 in Mxi1 MEFs and number of PCNApositivecells was increased in Mxi1-/- mice. Moreover, the IGFBP-3 level was decreasedin proliferation defect regions in Mxi1-/- mice. The results support the suggestion thatinactivation of Mxi1 has a positive effect on cell proliferation by down-regulating IGFBP-3.L-18-42Steady laminar flow activation of ERK5 in vascular endothelium leads toHO-1 expression via NF-E2-related factor 2 (Nrf2) activationMiso Kim, Suji Kim and Chang-Hoon WooDepartment of Pharmacology, Aging-associated Vascular Disease Research Center, YeungnamUniversity College of Medicine, Daegu 705-717, KoreaDifferential responses of anti-inflammatory and anti-apoptotic genes to laminar shearstress in endothelial cells have been elucidated. Atherosclerotic lesions were often foundin areas of the arterial tree exposed to disturbed flow, whereas atheroprotective lesionsexperienced by steady laminar shear stress. The transcriptional factor Nrf2 (NF-E2-related fator2) contributes to the anti-atherosclerosis response via the ARE activationwhich is a key event to mediate HO-1 under laminar shear stress. Implication of ERK5which also mediates anti-inflammatory and anti-apoptotic genes in the presence oflaminar shear stress has been reported. We hypothesized that laminar flow activation ofboth ERK5 and Nrf2 have significant interaction to mediate atheroprotective effects invascular endothelium. In the present study, we examined the Nrf2 involved in ERK5-mediated atheroprotective gene expression. We found molecular interaction betweenERK5 and Nrf2 as well as ERK5 activation-increased transcriptional activation,suggesting that ERK5-induced anti-inflammatory gene expression via an Nrf2 elicited bylaminar shear stress may play a critical role of anti-inflammatory and anti-apoptoticmechanism in endothelial cells.L-18-45Gpx1, a novel interacting protein with GAPDH, prevents S-nitrosylationof GAPDH and inhibits the translocation to nucleusSun Young Lee, Chong-Kil Lee, Kwang-Hee Bae, Byoung Chul Park, Sung GooParkKorea Research Institute of Bioscience and Biotechnology, KoreaGlyceraldehydes-3-phosphate dehydrogenase (GAPDH) is a key enzyme in metabolism,including glycolysis and gluconeogenesis. For many decades, GAPDH has beenregarded merely as a housekeeping glycolytic enzyme that exists mainly in thecytoplasm. However, a variety of recent studies are now suggesting that GAPDH is amultifunctional protein. One of the functions is that nitric oxide- induced nuclear GAPDHmediates apoptosis in mammalian cell. Glutathione peroxidases (Gpx) are importantantioxidant enzymes in the detoxification of reactive oxygen species (ROS) includinghydrogen peroxide, lipid peroxides, and organic hydroperoxidase. Glutathione peroxidase(Gpx) is one of the antioxidant enzymes in cells. In this study, we found that there is aninteraction between GAPDH and GPX1. The results showed that Gpx1 interacts withGAPDH both in vivo and in vitro. In addition, GPX1 directly interacts with GAPDH throughits carboxy-terminal domain. Subsequent experiments demonstrated that Gpx1 preventsthe S-nitrosylation of GAPDH after nitroxide (NO) stress, and thereby inhibits thetranslocation of GAPDH to nucleus. We finded GPX1 which physiologically binds GAPDH, in not competition with Siah1, retaining GAPDH in the cytosol and preventing its nucleartraslocation. Thus, GPX1 may physioltically regulate the viability of cell.282 Korean Society for Biochemistry and Molecular Biology