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Biomedical subjects

W Ju

Publications and source records attributed to W Ju.

At least 19 recordsLinked to original sources
PubMed2006

GABAA receptor-associated phosphoinositide 3-kinase is required for insulin-induced recruitment of postsynaptic GABAA receptors.

Type A gamma-aminobutyric acid (GABAA) receptors mediate most of the fast inhibitory synaptic transmission within the vertebrate brain. The regulation of this inhibition is vital in modulating neural activity. One regulator of GABAA receptor function is insulin, which can serve to enhance GABAA receptor-mediated miniature inhibitory postsynaptic currents, via an increase in the number of receptors at the plasma membrane. We set out to investigate the molecular mechanisms involved in the insulin-induced potentiation of GABAA receptor-mediated responses, by examining the role of phosphoinositide 3-kinase (PI3-K), a key mediator of the insulin response within the brain. We found that PI3-K associates with the GABAA receptor, and this interaction is increased following insulin treatment. Additionally, the beta2 subunit of the GABAA receptor appears to mediate the insulin-stimulated association with the N-terminal SH2 domain of the p85 subunit of PI3-K. Our results imply a mechanism whereby insulin can regulate changes in synaptic transmission through its downstream actions on the GABAA receptor.

Analysis of Variance↗
PubMed2006

Activin receptor-like kinase 7 induces apoptosis of pancreatic beta cells and beta cell lines.

AIMS/HYPOTHESIS: Activin receptor-like kinase 7 (ALK7), a member of the type I receptor serine/threonine kinases of the TGF-beta superfamily, was recently reported to regulate cell proliferation and apoptosis. We hypothesised that ALK7 may play a role in modulating pancreatic beta cell proliferation and/or apoptosis. METHODS: We detected ALK7 expression in beta cells using RT-PCR, immunostaining and western blotting. Constitutively active, dominant negative or wild-type ALK7 was introduced into beta cells using adenoviral delivery. Proliferation was assessed using (3)H-thymidine incorporation and apoptosis was quantified using terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling detection, DNA degradation analysis and caspase-3 assays. RESULTS: Induction of constitutively active ALK7 in beta cells resulted in growth inhibition and enhanced apoptosis; no effect was seen with INS-1 cells expressing wild-type or dominant negative ALK7. Elevated glucose concentrations and fatty acid (palmitate) markedly increased expression levels of ALK7 transcripts and proteins in INS-1 and rat islets and increased beta cell apoptosis. Activation of ALK7 increased Smad2 phosphorylation, reduced protein kinase B (Akt) kinase activity and was associated with increased levels of the bioactive forms of caspase-3, whereas co-expression of constitutively active ALK7 with dominant negative Smad2 or constitutively active Akt significantly diminished ALK7-induced growth inhibition and apoptosis in INS-1 cells. Although overexpression of constitutively active Akt significantly reduced ALK7-induced growth inhibition and ALK7-enhanced beta cell apoptosis, ALK7-stimulated Smad2 phosphorylation was not affected. CONCLUSIONS/INTERPRETATION: These results suggest that the pancreatic beta cell apoptosis induced by ALK7 activation occurs via the activation of two distinct downstream pathways: the suppression of Akt activation and the activation of the Smad2-caspase-3 cascade.

Activin Receptors, Type I↗
PubMed2005

Progression of early postnatal retinal pathology in a mouse model of neuronal ceroid lipofuscinosis.

PURPOSE: Accumulation of autofluorescent storage material in the CNS is a hallmark of neuronal ceroid lipofuscinosis (NCL, Batten disease). Since the retina is generally the first CNS target affected in NCL and could serve as a means to assess early disease progression as well as potential therapeutic responses, we followed the course of postnatal retinal pathology in tissues from the CLN8 (mnd) mouse model of NCL. RESULTS: Cytoplasmic inclusions in the retinal ganglion cell (RGC) layer were shown by periodic acid schiff stain by P7. TUNEL measurements of cell death became significant at P21 (P<0.001) with most cell death occurring in the photoreceptor layer. Significant autofluorescence and RGC hypertrophy were evident in mnd mice at P0, prior to eye opening or significant cell death. CONCLUSION: An increased understanding of the timing, location, and characteristic retinal pathologies of Batten disease may lead to diagnostic and therapeutic advances in the clinical setting.

Aging↗
PubMed2003

Ovarian steroids reduce apoptosis induced by trophic insufficiency in nerve growth factor-differentiated PC12 cells and axotomized rat facial motoneurons.

Previous studies have demonstrated that ovarian steroids exert neuroprotective effects in a variety of in vitro and in vivo systems. The mechanisms underlying these effects remain poorly understood. In the present study, the neuroprotective effects of estradiol (E(2)) and progesterone (P) were examined in two models of apoptosis induced by growth factor insufficiency: partially nerve growth factor (NGF)-differentiated PC12 cells, after serum and NGF withdrawal; and axotomized immature rat facial motor motoneurons. E(2) and P both increased the survival of trophically withdrawn NGF-differentiated PC12 cells, at physiologically relevant concentrations. However, neither steroid had a significant effect on the survival of PC12 cells that had not been NGF treated. Exposure to NGF had no effect on the expression of estrogen receptor (ER)beta, but markedly increased the levels of ERalpha and altered the expression of the progesterone receptor (PR) from predominantly PR-B in NGF naive cells, to predominantly PR-A after NGF. The survival promoting effects of E(2) and P were blocked by the specific steroid receptor antagonists Faslodex (ICI 182780) and onapristone (ZK98299), respectively. Inhibitors of RNA (actinomycin D) or protein (cycloheximide) synthesis also abrogated the protective effects of both steroids. In immature rats, E(2) and P both significantly increased the numbers of surviving facial motor neurons at 21 days after axotomy. These data demonstrate significant protective effects of E(2) and P in two well-characterized models of apoptosis induced by trophic withdrawal and suggest that, at least in PC12 cells, the effects of the steroids are mediated via interaction with nuclear steroid receptor systems. The lack of steroid responsiveness in NGF-naive PC12 cells despite the presence of abundant ERbeta and PR-B are consistent with the view that ERalpha and PR-A may be particularly important as mediators of the neuroprotective effects of their corresponding hormonal ligands.

Animals↗
PubMed2001

LTP in a culture dish.

The "aging" of populations in the developed world is rapidly altering demographics and presents a number of challenges for science and medicine. Foremost among these challenges is the need to enhance the quality of life for this "aging" majority. Paradoxically, improved prevention and treatment of diseases will only increase the number of individuals who will lose quality of life because of cognitive deficits in learning and memory. Such cognitive deficits are particularly vexing in societies where the ability to deal with information technology has become an increasing necessity. Understanding how the human brain encodes and stores information becomes critical in designing required therapeutic strategies.

Cell Culture Techniques↗
PubMed2001

Activation of synaptic NMDA receptors induces membrane insertion of new AMPA receptors and LTP in cultured hippocampal neurons.

Long-term potentiation (LTP) of excitatory transmission in the hippocampus likely contributes to learning and memory. The mechanisms underlying LTP at these synapses are not well understood, although phosphorylation and redistribution of AMPA receptors may be responsible for this form of synaptic plasticity. We show here that miniature excitatory postsynaptic currents (mEPSCs) in cultured hippocampal neurons reliably demonstrate LTP when postsynaptic NMDA receptors are briefly stimulated with glycine. LTP of these synapses is accompanied by a rapid insertion of native AMPA receptors and by increased clustering of AMPA receptors at the surface of dendritic membranes. Both LTP and glycine-facilitated AMPA receptor insertion are blocked by intracellular tetanus toxin (TeTx), providing evidence that AMPA receptors are inserted into excitatory synapses via a SNARE-dependent exocytosis during LTP.

Animals↗
PubMed2001

New mutations in the neuronal ceroid lipofuscinosis genes.

Thirty-eight mutations and seven polymorphisms have recently been reported in the genes underlying the neuronal ceroid lipofuscinoses (NCLs) including 11 new mutations described here. A total of 114 mutations and 28 polymorphisms have now been described in the five human genes identified which cause NCL. Thirty-eight mutations are recorded for CLN1/PPT; 40 for CLN2/TTP-1, 31 for CLN3, four for CLN5, one for CLN8. Two mutations have been described in animal genes (cln8/mnd, CTSD). All mutations in NCL genes are contained in the NCL Mutation Database (http://www.ucl.ac.uk/NCL).

Child↗
PubMed2001

Naturally acquired antibody responses to the C-terminal region of merozoite surface protein 1 of Plasmodium vivax in Korea.

We expressed a protein in Saccharomyces cerevisiae in order to evaluate the humoral immune responses to the C-terminal region of the merozoite surface protein 1 of Plasmodium vivax. This protein (Pv200(18)) had a molecular mass of 18 kDa and was reactive with the sera of individuals with patent vivax malaria on immunoblotting analysis. The levels of immunoglobulin M (IgM) and IgG antibodies against Pv200(18) were measured in 421 patients with vivax malaria (patient group), 528 healthy individuals from areas of nonendemicity (control group 1), and 470 healthy individuals from areas of endemicity (control group 2), using the indirect enzyme-linked immunosorbent assay (ELISA) method. To study the longevity of the antibodies, 20 subjects from the patient group were also tested for the antibody levels once a month for 1 year. When the cutoff values for seropositivity were determined as the mean + 3 x standard deviation of the antibody levels in control group 1, both IgG and IgM antibody levels were negative in 98.5% (465 of 472) of control group 2. The IgG and IgM antibodies were positive in 88.1% (371 of 421) and 94.5% (398 of 421) of the patient group, respectively. The IgM antibody became negative 2 to 4 months after the onset of symptoms, whereas the IgG antibody usually remained positive for more than 5 months. In conclusion, indirect ELISA using Pv200(18) expressed in S. cerevisiae may be a useful diagnostic method for vivax malaria.

Adult↗
PubMed2000

Intracellular trafficking of AMPA receptors in synaptic plasticity.

Modification of ligand-gated receptor function at the postsynaptic domain is one of the most important mechanisms by which the efficacy of synaptic transmission in the nervous system is regulated. Traditionally, these types of modifications have been thought to be achieved mainly by altering the channel-gating properties or conductance of the receptors. However, recent evidence suggests that AMPA (alpha-amino-3-hydroxyl-5-methyl-4-isoxayolepropionic acid)-type ligand-gated glutamate receptors are continuously recycling between the plasma membrane and the intracellular compartments via vesicle-mediated plasma membrane insertion and clathrin-dependent endocytosis. Regulation of either receptor insertion or endocytosis results in a rapid change in the number of these receptors expressed on the plasma membrane surface and in the receptor-mediated responses, thereby playing an important role in mediating certain forms of synaptic plasticity. Thus, controlling the number of postsynaptic receptors by regulating the intracellular trafficking and plasma membrane expression of the postsynaptic receptors may be a common and important mechanism of synaptic plasticity in the mammalian central nervous system.

Cell Line↗
PubMed2000

CLN-encoded proteins do not interact with each other.

The lysosomal storage of lipofuscins is the common pathological feature that characterizes the infantile, late-infantile, juvenile (Batten's disease), and Finnish-variant neuronal ceroid lipofuscinosis (INCL, LINCL, JNCL and FNCL), which are due to mutations in the genes CLN1, CLN2, CLN3, and CLN5, respectively. The CLN1 and CLN2 genes encode lysosomal enzymes, but the CLN3 and CLN5 genes encode membrane-spanning proteins. Why deficiencies of lysosomal enzymes and membrane-spanning proteins produce similar clinical phenotypes and pathological changes is still unanswered. We hypothesize that CLN-encoded proteins may comprise a functional pathogenic pathway, in which protein associations may play important roles. To test this hypothesis, we studied protein-protein interactions among the CLN1-, CLN2-, and CLN3-encoded proteins using a yeast two-hybrid system. Our results provided no evidence that CLN-encoded proteins interact with each other. This suggests there may be unidentified components in NCL pathogenesis.

Chromosome Mapping↗
PubMed2000

Distinct molecular mechanisms and divergent endocytotic pathways of AMPA receptor internalization.

Internalization of postsynaptic AMPA receptors depresses excitatory transmission, but the underlying dynamics and mechanisms of this process are unclear. Using immunofluorescence and surface biotinylation, we characterized and quantified basal and regulated AMPA receptor endocytosis in cultured hippocampal neurons, in response to synaptic activity, AMPA and insulin. AMPA-induced AMPA receptor internalization is mediated in part by secondary activation of voltage-dependent calcium channels, and in part by ligand binding independent of receptor activation. Although both require dynamin, insulin- and AMPA-induced AMPA receptor internalization are differentially dependent on protein phosphatases and sequence determinants within the cytoplasmic tails of GluR1 and GluR2 subunits. AMPA receptors internalized in response to AMPA stimulation enter a recycling endosome system, whereas those internalized in response to insulin diverge into a distinct compartment. Thus, the molecular mechanisms and intracellular sorting of AMPA receptors are diverse, and depend on the internalizing stimulus.

Animals↗
PubMed2000

Molecular diagnosis of and carrier screening for the neuronal ceroid lipofuscinoses.

The neuronal ceroid lipofuscinoses (NCLs) are a large group of autosomal recessive lysosomal storage disorders with both enzymatic deficiency and structural protein dysfunction. Three typical forms, the infantile (INCL), late-infantile (LINCL), and juvenile (JNCL), are among the most common childhood-onset neurodegenerative disorders. They result from mutations on genes CLN1, CLN2, and CLN3, respectively. We determined that the mutations 223A --> G and 451C --> T in CLN1, T523-1G --> C, and 636 C --> T in CLN2, and deletion of a 1.02-kb genomic fragment in CLN3 are the five common mutations for NCL. To offer clinical genetic testing for the NCLs, we have developed simple and quick PCR-based molecular tests for detecting INCL-, LINCL-, and JNCL-affected individuals from 180 NCL families (27 INCL, 76 LINCL, and 77 JNCL). The sensitivity of testing to detect NCL patients among clinically suspected individuals was determined to be 78% (21/27) for INCL, 66% (54/76) for LINCL, and 75% (58/77) for JNCL. When molecular screening for carriers was conducted among the normal siblings or parents of the probands, we identified two carriers out of three individuals tested for INCL, 20/56 (35.7%) carriers for LINCL, and 48/106 (45.3%) carriers for JNCL families. In addition, 5% (9/180) of NCL patients revealed genetic heterogeneity and were reclassified. Seven patients previously diagnosed as having JNCL were now found to carry mutations of CLN2 (5/7) or CLN1 (2/7) and 2 with late-infantile onsets were identified as carrying mutations of CLN1. Our data demonstrate the importance of DNA testing to detect accurately both affected individuals and carriers in NCL families.

Adolescent↗
PubMed2000

The bone morphogenetic protein 2 signaling mediator Smad1 participates predominantly in osteogenic and not in chondrogenic differentiation in mesenchymal progenitors C3H10T1/2.

The role of the bone morphogenetic protein (BMP)-signaling mediator Smad1 in osteogenic or chondrogenic differentiation was investigated in murine parental mesenchymal progenitors C3H10T1/2 and its derivatives constitutively expressing BMP-2 (C3H10T1/2-BMP-2) and, therefore, undergo BMP-mediated osteogenic/ chondrogenic development. The functions of the three Smad1 domains, that is, the N-terminal (MH1) domain, the C-terminal (MH2) domain, and the midregional proline-rich linker domain, were documented and compared with full-length Smadl. We showed that expression of the MH2 domain in parental C3H10T1/2 cells was sufficient to initiate osteogenic differentiation. Interestingly, MH1 was sufficient to initiate transcription of osteogenic marker genes like the osteocalcin or parathyroid hormone/parathyroid hormone-related protein (PTH/PTHrP) receptor. However, MH1 interfered with the histologically distinct formation of osteoblast-like cells. A dominant-negative effect on MH2-mediated osteogenic development in C3H10T1/2 cells was observed by the dose-dependent trans-expression of the midregional linker domain. Importantly, in contrast to osteogenic differentiation, Smad1 and its domains do not mimic or interfere with BMP-2-dependent chondrogenic development as monitored by the inability of MH2 to give rise to histologically distinct chondrocytes in parental C3H10T1/2 cells and by the inefficiency of the MH1 or linker domain to interfere with BMP-2-mediated chondrogenic differentiation.

Alkaline Phosphatase↗
PubMed2000

An epidemiology and molecular genetic study on breast cancer susceptibility.

OBJECTIVES: To investigate the genetic susceptibility for breast cancer of Chinese, a hospital-based case-control study, pedigree survey and molecular genetic study were conducted. METHODS: Logistic regression model and stratification methods were used in the risk factors analysis. Li-Mantel-Gart and Falconer methods were used to analyse the segregation ratio and heritability. Polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis were used to detect AI, G-binding technique was used to detect the chromosome aberration of peripheral blood lymphocyte. RESULTS: Family history of breast cancer is related to enhanced breast cancer risk significantly, OR is 3.905 (95% CI = 1.079 approximately 14.13), and it widely interacts with other risk factors. Accumulative incidence of breast cancer in first degree relatives is 9.99%, which is larger than that in second, third degree and non-blood relatives. Segregation ratio is 0.021, heritability among first degree relatives is 35.6 +/- 5.8%. Frequencies of LOH at BRCA1 and BRCA2 loci in sporadic breast cancer are 6.12% and 5.77% respectively. In the sibs, both of them show LOH at D13S173 locus, and high frequencies of chromosome aberrations were observed. CONCLUSIONS: Genetic susceptibility contributes to breast cancer occurrence of Chinese, and its racial variation may be one of the important reasons for the large difference of incidence between western and eastern countries.

Adult↗
PubMed1999

Frequency of the fragile X syndrome in Chinese mentally retarded populations is similar to that in Caucasians.

Fragile X syndrome is recognized as the most common inherited cause of mental retardation in western countries. The prevalence of the fragile X syndrome in Asian populations is uncertain. We report a multi-institutional collaborative study of molecular screening for the fragile X syndrome from 1,127 Chinese mentally retarded (MR) individuals. We found that 2.8% of the Chinese MR population screened by DNA analysis had the fragile X full mutation. Our screening indicated that the fragile X syndrome prevalence was very close to that of Caucasian subjects. In addition, we found that 62.5% of fragile X chromosomes had a single haplotype for DXS548-FRAXAC1 (21-18 repeats) which was present in only 9.7% of controls. This unique distribution of microsatellite markers flanking the FMR1 CGG repeats suggests that the fragile X syndrome in Chinese populations, as in the Caucasian, may also be derived from founder chromosomes.

Alleles↗
PubMed1999

Reduced mRNA for G3BP in fragile X cells: evidence of FMR1 gene regulation.

Although fragile X syndrome is caused by the absence of fragile X gene expression, little is known about the pathogenic processes underlying the mental retardation. Recent findings that the fragile X protein, FMRP, contains RNA binding motifs and nuclear transport signals and associates with ribosomes suggest that FMRP may be involved in either mRNA processing, transport, or translation. To test the hypothesis that absence of FMRP may affect the processing of specific transcripts, we have used an RNA differential display assay (RDDA) to identify differentially expressed transcripts in lymphoblast lines derived from fragile X syndrome patients. A 0.9-kb cDNA fragment that showed reduced expression in a fragile X lymphoblast cell line was found to be identical to G3BP (Ras-GTPase-Activating protein SH3-domain-binding protein). Quantitative reverse transcriptase-polymerase chain reaction showed that the expressed levels of G3BP mRNA in fragile X lymphoblast cell lines were significantly less than controls. Our results indicate that G3BP mRNA may be regulated by FMRP and supports the hypothesis that FMRP may modulate the transcription of specific transcripts.

Base Sequence↗