👤 Sun-Hee Park

The purpose of the present study was to identify genetic variants that confer susceptibility to dyslipidemia. A total of 5213 individuals from two independent populations were examined: Subject panel A comprised 3794 individuals who visited participating hospitals; subject panel B comprised 1419 community-dwelling elderly individuals. The genotypes for 100 polymorphisms of 65 candidate genes were determined. The chi(2) test and multivariable logistic regression analysis revealed that seven polymorphisms of APOA5, APOC3, APOA1, ACAT2, and LPL were significantly associated with hypertriglyceridemia, six polymorphisms of APOA5, LIPC, and CYP3A4 with low HDL-cholesterol, and three polymorphisms of APOE and CCR2 with high LDL-cholesterol in subject panel A. For validation of these associations, the same polymorphisms were examined in subject panel B. Six polymorphisms of APOA5, APOC3, APOA1, and LPL were again significantly associated with hypertriglyceridemia, three polymorphisms of APOA5 with low HDL-cholesterol, and two polymorphisms of APOE with high LDL-cholesterol. Serum triglyceride, HDL-cholesterol, and LDL-cholesterol concentrations differed significantly among genotypes of these corresponding polymorphisms in both subject panels. These results indicate that polymorphisms of APOA5, APOC3, APOA1, and LPL are determinants of hypertriglyceridemia and that those of APOA5 and APOE are determinants of low HDL-cholesterol and high LDL-cholesterol, respectively, in Japanese individuals. Show less

Recent studies using human and mice reported that apolipoprotein A-V (APOA5) gene plays an important role in controlling triglyceride (TG) concentrations. The purpose of the present study was to investigate the correlation between single nucleotide polymorphisms (SNPs) and haplotypes in the APOA5 gene and TG in subjects and to search for possible associations of the APOA5 gene variants and common haplotypes with hypertriglyceridemia (HTG). We examined the case-control subjects including 100 HTG patients and 243 unrelated healthy control. The genes were screened for SNPs by direct sequencing in 48 genetically unrelated individuals. Six SNPs (-1390C>T, -1020G>A, -3A>G, V150M, G182C and 1259T>C) were genotyped in case and control populations. In this study, our results indicated a strong association between APOA5 SNP -3A>G and G182C and elevated TG levels (p<0.001). Analysis of the SNPs from APOA5 gene has identified major haplotype showing very strong association with HTG, CGGGTT (p<0.001). Likelihood ratio test (LRT) of these six SNPs revealed that haplotypes were strong independent predictors of HTG (p<0.001). Haplotype-trend logistic regression (HTR) analysis revealed a significant association between the CGGGGC (haplotype 2) and CGGGTT (haplotype 4) and HTG (OR=2.48, 95% CI=1.06-5.76 and OR=8.54, 95% CI=2.66-27.42, respectively). We confirm that the APOA5 variants are associated with triglyceride levels and the haplotype may be strong independent predictors of HTG among Koreans. Show less

Calsenilin/DREAM/KChIP3, a neuronal Ca(2+)-binding protein, has multifunctions in nucleus and cytosol. Here, we identified CLN3 as a calsenilin-binding partner whose mutation or deletion is observed in Batten disease. In vitro binding and immunoprecipitation assays show that calsenilin interacts with the C-terminal region of CLN3 and the increase of Ca(2+) concentration in vitro and in cells causes significant dissociation of calsenilin from CLN3. Ectopic expression of CLN3 or its deletion mutant containing only the C-terminus (153-438) and capable of binding to calsenilin suppresses thapsigargin or A23187-induced death of neuronal cells. In contrast, CLN3 deletion mutant containing the N-terminus (1-153) or (1-263), which is frequently found in Batten disease, induces the perturbation of Ca(2+) transient and fails to inhibit the cell death. In addition, the expression of calsenilin is increased in the brain tissues of CLN3 knock-out mice and SH-SY5Y/CLN3 knock-down cells. Down-regulation of CLN3 expression sensitizes SH-SY5Y cells to thapsigargin or A23187. However, additional decrease of calsenilin expression rescues the sensitivity of SH-SY5Y/CLN3 knock-down cells to Ca(2+)-mediated cell death. These results suggest that the vulnerability of CLN3 knock-out or CLN3 deletion (1-153)-expressing neuronal cells to Ca(2+)-induced cell death may be mediated by calsenilin. Show less

Epstein-Barr virus latency is maintained by the latent membrane protein (LMP) 2A, which mimics the B-cell receptor (BCR) and perturbs BCR signaling. The cytoplasmic N-terminal domain of LMP2A is composed of 119 amino acids. The N-terminal domain of LMP2A (LMP2A NTD) contains two PY motifs (PPPPY) that interact with the WW domains of Nedd4 family ubiquitin-protein ligases. Based on our analysis of NMR data, we found that the LMP2A NTD adopts an overall random-coil structure in its native state. However, the region between residues 60 and 90 was relatively ordered, and seemed to form the hydrophobic core of the LMP2A NTD. This region resides between two PY motifs and is important for WW domain binding. Mapping of the residues involved in the interaction between the LMP2A NTD and WW domains was achieved by chemical shift perturbation, by the addition of WW2 and WW3 peptides. Interestingly, the binding of the WW domains mainly occurred in the hydrophobic core of the LMP2A NTD. In addition, we detected a difference in the binding modes of the two PY motifs against the two WW peptides. The binding of the WW3 peptide caused the resonances of five residues (Tyr(60), Glu(61), Asp(62), Trp(65), and Gly(66)) just behind the N-terminal PY motif of the LMP2A NTD to disappear. A similar result was obtained with WW2 binding. However, near the C-terminal PY motif, the chemical shift perturbation caused by WW2 binding was different from that due to WW3 binding, indicating that the residues near the PY motifs are involved in selective binding of WW domains. The present work represents the first structural study of the LMP2A NTD and provides fundamental structural information about its interaction with ubiquitin-protein ligase. Show less

To identify vitreous proteins that were differentially expressed in patients suffering from proliferative diabetic retinopathy with active neovascularization. The vitreous samples of 15 active proliferative diabetic retinopathy patients were analyzed by two-dimensional gel electrophoresis and mass spectrometry, and the results were compared with those from age-matched patients with macular hole. Twenty-five protein spots were identified in the two-dimensional gel electrophoresis gels. Eight proteins (pigmented epithelium derived factor, serine protease inhibitor, apolipoprotein A-IV precursor, prostaglandin-H2 D-isomerase, a(1)-antitrypsin precursor, ankyrin repeat domain 15 protein, alpha2-HS-glycoprotein, and beta V spectrin) in the 25 spots were expressed significantly differently between the macular hole and proliferative diabetic retinopathy patients (p value < 0.05). Five proteins were upregulated in the proliferative diabetic retinopathy patients, and three were downregulated (p value < 0.05). We constructed vitreous protein profiles for proliferative diabetic retinopathy patients and identified eight candidate proteins believed to be involved in the pathogenesis of proliferative diabetic retinopathy. Show less

The epidermal growth factor receptor (EGFR) gene is commonly amplified and rearranged in glioblastoma multiforme leading to overexpression of wild-type and mutant EGFRs. Expression of wild-type EGFR ligands, such as transforming growth factor-alpha (TGF-alpha) or heparin-binding EGF (HB-EGF), is also often increased in gliomas resulting in an autocrine loop that contributes to the growth autonomy of glioma cells. Glioblastoma multiformes express a characteristic EGFR mutant (EGFRvIII, de 2-7) that does not bind ligand, signals constitutively, and is more tumorigenic than the wild-type receptor. However, the downstream signals that mediate this increased tumorigenicity are not well understood. We hypothesized that signals induced specifically by EGFRvIII and not the wild-type receptor are more likely to mediate its increased tumorigenic activity and examined the gene expression profiles resulting from inducible expression of comparable levels of either wild-type EGFR or EGFRvIII in a U251-MG glioma cell line. Expression of EGFRvIII resulted in specific up-regulation of a small group of genes. Remarkably, all these genes, which include TGFA, HB-EGF, EPHA2, IL8, MAP4K4, FOSL1, EMP1, and DUSP6, influence signaling pathways known to play a key role in oncogenesis and function in interconnected networks. Increased expression of EGFRvIII-induced genes was validated by real-time PCR. The mutant receptor does not bind ligand, and EGFRvIII-induced expression of TGF-alpha and HB-EGF suggests that EGFRvIII plays a role in generating an autocrine loop using the wild-type EGFR in glioma. It also raises the possibility that EGFRvIII may signal, at least in part, through the wild-type receptor. Indeed, we show that inhibiting the activity of HB-EGF, a potent mitogen, with neutralizing antibodies reduces cell proliferation induced by expression of EGFRvIII. This suggests that the EGFRvIII-HB-EGF-wild-type EGFR autocrine loop plays an important role in signal transduction by EGFRvIII in glioma cells. We also show by immunohistochemistry that HB-EGF expression correlates with the presence of EGFRvIII in glioblastoma multiforme. Thus, our study provides a new insight into oncogenic signaling by EGFRvIII and improves our understanding of how autocrine loops are generated in glioma. Show less

A major obstacle for successful axon regeneration in the adult central nervous system (CNS) arises from inhibitory molecules in CNS myelin, which signal through a common receptor complex on neurons consisting of the ligand-binding Nogo-66 receptor (NgR) and two transmembrane coreceptors, p75 and LINGO-1. However, p75 expression is only detectable in subpopulations of mature neurons, raising the question of how these inhibitory signals are transduced in neurons lacking p75. In this study, we demonstrate that TROY (also known as TAJ), a TNF receptor family member selectively expressed in the adult nervous system, can form a functional receptor complex with NgR and LINGO-1 to mediate cellular responses to myelin inhibitors. Also, both overexpressing a dominant-negative TROY or presence of a soluble TROY protein can efficiently block neuronal response to myelin inhibitors. Our results implicate TROY in mediating myelin inhibition, offering new insights into the molecular mechanisms of regeneration failure in the adult nervous system. Show less

Adenomatous polyposis coli (APC) protein and Axin form a complex that mediates the down-regulation of beta-catenin, a key effector of Wnt signaling. Truncation mutations in APC are responsible for familial and sporadic colorectal tumors due to failure in the down-regulation of beta-catenin. While the regulation of beta-catenin by APC has been extensively studied, the regulation of APC itself has received little attention. Here we show that the level of APC is down-regulated by the ubiquitin-proteasome pathway and that Wnt signaling inhibits the process. The domain responsible for the down-regulation and direct ubiquitination was identified. We also show an unexpected role for Axin in facilitating the ubiquitination-proteasome-mediated down-regulation of APC through the oligomerization of Axin. Our results suggest a new mechanism for the regulation of APC by Axin and Wnt signaling. Show less

The pathology of diabetic retinopathy includes dilatation and beading of retinal vessels, and vascular sheathing. To gain a better understanding of the molecular events leading to diabetic retinopathy, we investigated disease-specific gene responses by screening differential expression using cDNA microarray. Male Sprague-Dawley rats were intraperitoneally injected with streptozotocin (STZ, 50 mg/kg) or the control buffer and were maintained for 6 weeks. Total RNA extracted from the retinas of both groups was used for cDNA microarray analysis. Signals from all the spots representing hybridized DNA were quantified and compared between the normal and diabetic rat retinas. Among 1176 genes analyzed, the retinal expression of glucose-dependent insulinotropic polypeptide (GIP) was found to increase in STZ-induced diabetic rats compared to controls. GIP is a secreted protein, known to be released from the small intestine, which potentiates glucose-induced insulin secretion from the pancreas. However, the expression of GIP and its receptor (GIPR) has not been previously noted in the rat retina. To further validate the expression of GIP in the rat retina and to determine its possible role in the development of early diabetic retinopathy, we investigated its expression by RT-PCR, Northern blotting, and immunohistochemistry in normal and diabetic rat retinas. GIP mRNA and protein are not only expressed in the rat retina, but their levels are greater in the diabetic rat as compared to controls. And GIPR expression was also upregulated in the retinas of STZ-induced diabetic rats. We here demonstrate for the first time the expression of GIP and GIPR in the rat retina. And we also revealed some genetic events in the early stage of diabetic retinopathy including the de novo increment of GIP and GIPR expression in the retina. Show less

RNA undergoing nuclear export first encounters the basket of the nuclear pore. Two basket proteins, Nup98 and Nup153, are essential for mRNA export, but their molecular partners within the pore are largely unknown. Because the mechanism of RNA export will be in question as long as significant vertebrate pore proteins remain undiscovered, we set out to find their partners. Fragments of Nup98 and Nup153 were used for pulldown experiments from Xenopus egg extracts, which contain abundant disassembled nuclear pores. Strikingly, Nup98 and Nup153 each bound the same four large proteins. Purification and sequence analysis revealed that two are the known vertebrate nucleoporins, Nup96 and Nup107, whereas two mapped to ORFs of unknown function. The genes encoding the novel proteins were cloned, and antibodies were produced. Immunofluorescence reveals them to be new nucleoporins, designated Nup160 and Nup133, which are accessible on the basket side of the pore. Nucleoporins Nup160, Nup133, Nup107, and Nup96 exist as a complex in Xenopus egg extracts and in assembled pores, now termed the Nup160 complex. Sec13 is prominent in Nup98 and Nup153 pulldowns, and we find it to be a member of the Nup160 complex. We have mapped the sites that are required for binding the Nup160 subcomplex, and have found that in Nup98, the binding site is used to tether Nup98 to the nucleus; in Nup153, the binding site targets Nup153 to the nuclear pore. With transfection and in vivo transport assays, we find that specific Nup160 and Nup133 fragments block poly[A]+ RNA export, but not protein import or export. These results demonstrate that two novel vertebrate nucleoporins, Nup160 and Nup133, not only interact with Nup98 and Nup153, but themselves play a role in mRNA export. Show less

Hereditary multiple exostoses (EXT) is an autosomal dominantly inherited disease characterized by the formation of cartilage-capped prominences (exostoses) that develop from the juxtaepiphyseal regions of the long bones. Recently, EXT1 and EXT2 genes were cloned and germline mutations of EXT1 and EXT2 were identified in EXT families. In this study, we performed a mutational analysis of EXT1 and EXT2 genes in eight unrelated Korean EXT families by polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis followed by direct DNA sequencing. As a result, we were able to identify one family (SNU-OC3) with the EXT1 mutation and another family (SNU-OC15) with the EXT2 mutation. The EXT1 mutation was a 10-bp deletion at the 3' end of exon 5 (CTAATTTAGg) including the splice site of this exon. The EXT2 mutation identified in the SNU-OC15 family was a missense mutation at codon 85 of exon 2 (TGC-->CGC), resulting in an amino acid change from cysteine to arginine. This missense mutation cosegregated with the disease phenotype in this family, suggesting that it is the disease-causing mutation. These two mutations identified in EXT1 and EXT2 are novel ones. Show less

Hepatocellular carcinoma (HCC) is one of the most common human tumors in Asia and Africa. The molecular genetic changes involving both protooncogenes and tumor suppressor genes are known to be involved in hepatocarcinogenesis, but the roles of the known tumor suppressor genes in hepatocarcinogenesis are not fully elucidated. In this study, the authors analyzed the loss of heterozygosity (LOH) of known tumor suppressor genes in HCC and evaluated the relationship between LOH of tumor suppressor genes and clinicopathologic features. The authors assessed the LOH of the 10 known tumor suppressor genes (VHL, APC, EXT1, WT1, Rb1, p53, BRCA1, nm23, DPC4, and DCC) with microsatellite markers in 29 consecutively resected HCC specimens. The authors found frequent LOH of tumor suppressor genes in HCC. Twenty five of 29 cases (86%) had LOH of tumor suppressor genes and 17 cases (59%) had LOHs involving 2-4 tumor suppressor genes. Among the tumor suppressor genes, frequent LOH was noted in the p53 (66%), Rb1 (33%), EXT1 (33%), and APC (20%) genes. LOH of the p53 gene and multiple LOH of the tumor suppressor genes were more frequent in poorly differentiated HCCs (P = 0.02). The LOH of tumor suppressor genes is frequent in HCCs and LOH of the p53 gene and accumulated LOHs are related to poorly differentiated HCC. Abnormalities of the p53 gene or the accumulated abnormalities of the tumor suppressor genes may play a role in the aggressive progression of HCC. Show less