Showing papers by "David A. Pearce published in 2005"
TL;DR: Impairments in Reelin protein and mRNA and Dab 1 mRNA and elevations in Reln receptor VLDLR mRNA demonstrate impairments in the Reelin signaling system in autism, accounting for some of the brain structural and cognitive deficits observed in the disorder.
264 citations
TL;DR: A novel link between GILZ and regulation of epithelial sodium transport through modulation of ERK signaling is suggested and could represent an important pathway for mediating aldosterone actions in health and disease.
183 citations
TL;DR: It is shown that SGK1-mediated phosphorylation of Nedd4-2 induces its interaction with members of the 14-3-3 family of regulatory proteins, which provides a mechanism by which SGK 1 modulates the ENaC-mediated Na(+) current.
Abstract: Serum- and glucocorticoid-regulated kinase 1 (SGK1) is an aldosterone-regulated early response gene product that regulates the activity of several ion transport proteins, most notably that of the epithelial sodium channel (ENaC). Recent evidence has established that SGK1 phosphorylates and inhibits Nedd4-2 (neural precursor cell-expressed, developmentally down-regulated protein 4-2), a ubiquitin ligase that decreases cell surface expression of the channel and possibly stimulates its degradation. The mechanistic basis for this SGK1-induced Nedd4-2 inhibition is currently unknown. In this study we show that SGK1-mediated phosphorylation of Nedd4-2 induces its interaction with members of the 14-3-3 family of regulatory proteins. Through functional characterization of Nedd4-2-mutant proteins, we demonstrate that this interaction is required for SGK1-mediated inhibition of Nedd4-2. The concerted action of SGK1 and 14-3-3 appears to disrupt Nedd4-2-mediated ubiquitination of ENaC, thus providing a mechanism by which SGK1 modulates the ENaC-mediated Na(+) current. Finally, the expression pattern of 14-3-3 is also consistent with a functional role in distal nephron Na(+) transport. These results demonstrate a novel, physiologically significant role for 14-3-3 proteins in modulating ubiquitin ligase-dependent pathways in the control of epithelial ion transport.
173 citations
TL;DR: These results show for the first time that prenatal human influenza viral infection on day 9 of pregnancy leads to alterations in a subset of genes in brains of exposed offspring, potentially leading to permanent changes in brain structure and function.
Abstract: Schizophrenia and autism are neurodevelopmental disorders with genetic and environmental etiologies. Prenatal viral infection has been associated with both disorders. We investigated the effects of prenatal viral infection on gene regulation in offspring of Balb-c mice using microarray technology. The results showed significant upregulation of 21 genes and downregulation of 18 genes in the affected neonatal brain homogenates spanning gene families affecting cell structure and function, namely, cytosolic chaperone system, HSC70, Bicaudal D, aquaporin 4, carbonic anhydrase 3, glycine receptor, norepinephrine transporter, and myelin basic protein. We also verified the results using QPCR measurements of selected mRNA species. These results show for the first time that prenatal human influenza viral infection on day 9 of pregnancy leads to alterations in a subset of genes in brains of exposed offspring, potentially leading to permanent changes in brain structure and function.
154 citations
TL;DR: Together, these changes represent the first documented pre-symptomatic symptoms of the Cln3 mouse at 1 month of age and demonstrate the versatility of 1H NMR spectroscopy as a tool for phenotyping mouse models of disease.
147 citations
TL;DR: It is concluded that CLN3 is likely resident in the lysosomal/endosomal membrane and undergoes several posttranslational modifications and is trafficked through the endoplasmic reticulum and Golgi.
Abstract: Batten disease, an inherited neurodegenerative storage disease affecting children, results from the autosomal recessive inheritance of mutations in Cln3. The function of the CLN3 protein remains unknown. A key to understanding the pathology of this devastating disease will be to elucidate the function of CLN3 at the cellular level. CLN3 has proven difficult to study as it is predicted to be a membrane protein expressed at relatively low levels. This article is a critical review of various approaches used in examining the structure, trafficking, and localization of CLN3. We conclude that CLN3 is likely resident in the lysosomal/endosomal membrane. Different groups have postulated conflicting orientations for CLN3 within this membrane. In addition, CLN3 undergoes several posttranslational modifications and is trafficked through the endoplasmic reticulum and Golgi. Recent evidence also suggests that CLN3 traffics via the plasma membrane. Although the function of this protein remains elusive, it is apparent that genetic alterations in Cln3 may have a direct affect on lysosomal function. © 2005 Wiley-Liss, Inc.
109 citations
TL;DR: It is concluded that the cellular differences in SRC-1a to SRC -1e ratio demonstrated in vivo might be involved in cell-specific responses to corticosteroids in a promoter- and ligand-dependent way.
Abstract: The mechanisms of receptor- and cell-specific effects of the adrenal corticosteroid hormones via mineralo- (MRs) and glucocorticoid receptors (GRs) are still poorly understood. Because the expression levels of two splice variants of the steroid receptor coactivator-1 (SRC-1) 1a and 1e, can differ significantly in certain cell populations, we tested the hypothesis that their relative abundance could determine cell- and receptor-specific effects of corticosteroid receptor-mediated transcription. In transient transfections, we demonstrate three novel types of SRC-1a- and SRC-1e-specific effects for corticosteroid receptors. One is promoter dependence: SRC-1e much more potently coactivated transcription from several multiple response element-containing promoters. Mammalian 1-hydrid studies indicated that this likely does not involve promoter-specific coactivator recruitment. Endogenous phenylethanolamine-N-methyltransferase mRNA induction via GRs was also differentially affected by the splice variants. Anothe...
100 citations
TL;DR: Serum- and glucocorticoid-regulated kinase 1 (SGK1) has been identified as an important mediator of this process and its physiological relevance has been revealed through heterologous expression in cultured cells and generation of SGK1 knockout mice.
Abstract: Recently, substantial progress has been made in understanding the mechanisms by which aldosterone rapidly stimulates sodium transport in the distal nephron and other tight epithelia. Serum- and glucocorticoid-regulated kinase 1 (SGK1) has been identified as an important mediator of this process. Its physiological relevance has been revealed through heterologous expression in cultured cells and generation of SGK1 knockout mice.
93 citations
TL;DR: It is reported that lysosomes isolated from juvenile Batten disease lymphoblasts are only defective for arginine transport, suggesting that the CLN3 defect in juvenile batten disease may affect how intracellular levels ofArginine are regulated or distributed throughout the cell.
Abstract: Mutations in the CLN3 gene, which encodes a lysosomal membrane protein, are responsible for the neurodegenerative disorder juvenile Batten disease. A previous study on the yeast homolog to CLN3, designated Btn1p, revealed a potential role for CLN3 in the transport of arginine into the yeast vacuole, the equivalent organelle to the mammalian lysosome. Lysosomes isolated from lymphoblast cell lines, established from individuals with juvenile Batten disease-bearing mutations in CLN3, but not age-matched controls, demonstrate defective transport of arginine. Furthermore, we show that there is a depletion of arginine in cells derived from individuals with juvenile Batten disease. We have, therefore, characterized lysosomal arginine transport in normal lysosomes and show that it is ATP-, v-ATPase- and cationic-dependent. This and previous studies have shown that both arginine and lysine are transported by the same transport system, designated system c. However, we report that lysosomes isolated from juvenile Batten disease lymphoblasts are only defective for arginine transport. These results suggest that the CLN3 defect in juvenile Batten disease may affect how intracellular levels of arginine are regulated or distributed throughout the cell. This assertion is supported by two other experimental approaches. First, an antibody to CLN3 can block lysosomal arginine transport and second, expression of CLN3 in JNCL cells using a lentiviral vector can restore lysosomal arginine transport. CLN3 may have a role in regulating intracellular levels of arginine possibly through control of the transport of this amino acid into lysosomes.
88 citations
TL;DR: The Unified Batten Disease Rating Scale (UBDRS) is a reliable instrument that effectively tests for neurologic function in blind and demented patients and is useful for monitoring the diverse clinical findings seen in Batten disease.
Abstract: Background: Batten disease (juvenile neuronal ceroid lipofuscinosis [JNCL]) is an autosomal recessive neurodegenerative disorder characterized by blindness, seizures, and relentless decline in cognitive, motor, and behavioral function. Onset is in the early school years, with progression to death typically by late adolescence. Development of a clinical instrument to quantify severity of illness is a prerequisite to eventual assessment of experimental therapeutic interventions Objective: To develop a clinical rating instrument to assess motor, behavioral, and functional capability in JNCL. Methods: A clinical rating instrument, the Unified Batten Disease Rating Scale (UBDRS), was developed by the authors to assess motor, behavioral, and functional capability in JNCL. Children with verified JNCL were evaluated independently by three neurologists. Intraclass correlation coefficients (ICCs) were used to estimate the interrater reliability for total scores in each domain. Interrater reliability for scale items was assessed with weighted κ statistics Results: Thirty-one children with confirmed JNCL (10 boys, 21 girls) were evaluated. The mean age at symptom onset was 6.1 ± 1.6 years, and the mean duration of illness was 9.0 ± 4.4 years. The ICCs for the domains were as follows: motor = 0.83, behavioral = 0.68, and functional capability = 0.85. Conclusions: The Unified Batten Disease Rating Scale (UBDRS) is a reliable instrument that effectively tests for neurologic function in blind and demented patients. In its current form, the UBDRS is useful for monitoring the diverse clinical findings seen in Batten disease.
86 citations
TL;DR: Comparison of the results from lakes of different nutrient status suggest that increased levels of nutrient input, and in the timing and duration of ice cover will lead to marked changes in the structure and stability of the bacterioplankton community at existing levels of environmental change.
TL;DR: The significant impact of natural nutrient enrichment on the microbiology of Heywood Lake suggests that low-temperature oligotrophic freshwater lake systems might have low resistance to environmental change.
Abstract: Nutrient enrichment is known to increase bacterioplankton population density in a variety of Antarctic freshwater lakes. However, relatively little is known about the associated changes in species composition. In this study, the bacterioplankton community composition of one such lake was studied following natural nutrient enrichment to investigate the resistance of the system to environmental change. Heywood Lake is an enriched freshwater maritime Antarctic lake, with nitrogen and phosphorus concentrations significantly higher than its more oligotrophic neighbours (by at least an order of magnitude). This major change in lake chemistry has occurred following large increases in the fur seal population over the last 30 years. Using analysis of 16S rRNA gene fragments, fatty acid methyl ester analysis, denaturing gradient gel electrophoresis and fluorescence in situ hybridization, significant changes are reported in lake microbiology which have resulted in a distinct bacterioplankton community. In comparison to its more oligotrophic neighbours, nutrient-enriched Heywood Lake has a high bacterioplankton population density, reduced species richness and an increasing evenness among key groups. Only 42·3 % of the clones found with ≥97 % similarity to a named genus were also present in adjacent oligotrophic lakes, including three of the dominant groups. Critically, there was an apparent shift in dominance with trophic status (from the β-Proteobacteria to the Actinobacteria). Other key observations included the absence of a dominant group of Cyanobacteria and the presence of marine bacteria. The significant impact of natural nutrient enrichment on the microbiology of Heywood Lake, therefore, suggests that low-temperature oligotrophic freshwater lake systems might have low resistance to environmental change.
TL;DR: This study is the first demonstration that a diverse facultatively methylotrophic microbiota exists in some Antarctic locations, growing on various C1-substrates, including C2-sulfur compounds.
TL;DR: Btn2p may play a regulatory role across the cell in response to alterations in the intracellular environment that may be caused by changes in amino acid levels or pH, a disruption in protein trafficking, or imbalances in ion homeostasis resulting from either genetic or environmental manipulation.
Abstract: Btn2p, a novel cytosolic coiled-coil protein in Saccharomyces cerevisiae, was previously shown to interact with and to be necessary for the correct localization of Rhb1p, a regulator of arginine uptake, and Yif1p, a Golgi protein. We now report the biochemical and physical interactions of Btn2p with Ist2p, a plasma membrane protein that is thought to have a function in salt tolerance. A deletion in Btn2p (btn2Δ strains) results in a failure to correctly localize Ist2p, and strains lacking Btn2p and Ist2p (btn2Δ ist2Δ strains) are unable to grow in the presence of 0.5 or 1.0 M NaCl. Btn2p was originally identified as being up-regulated in a btn1Δ strain, which lacks the vacuolar-lysosomal membrane protein, Btn1p, and serves as a model for Batten disease. This up-regulation of Btn2p was shown to contribute to the maintenance of a stable vacuolar pH in the btn1Δ strain. Btn1p was subsequently shown to be required for the optimal transport of arginine into the vacuole. Interestingly, btn1Δ ist2Δ strains are also unable to grow in the presence of 0.5 or 1.0 M NaCl, and ist2Δ suppresses the vacuolar arginine transport defect in btn1Δ strains. Although further investigation is required, we speculate that altered vacuolar arginine transport in btn1Δ strains represents a mechanism for maintaining or balancing cellular ion homeostasis. Btn2p interacts with at least three proteins that are seemingly involved in different biological functions in different subcellular locations. Due to these multiple interactions, we conclude that Btn2p may play a regulatory role across the cell in response to alterations in the intracellular environment that may be caused by changes in amino acid levels or pH, a disruption in protein trafficking, or imbalances in ion homeostasis resulting from either genetic or environmental manipulation.
TL;DR: In Xenopus oocytes expressing the AMPA subunit GluR1, it is shown that SGK3, and to a lesser extent SGK2, but not SGK1, increase glutamate‐induced currents by increasing the abundance of GLUR1 protein in the cell membrane.
Abstract: Phosphatidylinositol 3 kinase (PI3-kinase) is activated during and is required for hippocampal glutamate receptor-dependent long-term potentiation. It mediates the delivery of AMPA receptors to the neuronal surface. Among the downstream targets of PI3-kinase are three members of the serum- and glucocorticoid-inducible kinase family, SGK1, SGK2 and SGK3. In Xenopus oocytes expressing the AMPA subunit GluR1, we show that SGK3, and to a lesser extent SGK2, but not SGK1, increase glutamate-induced currents by increasing the abundance of GluR1 protein in the cell membrane. We further show Sgk3 mRNA expression in the hippocampus by RT-PCR and in situ hybridization. According to Western blotting, the hippocampal abundance of GluR1 is significantly lower in gene-targeted mice lacking SGK3 (Sgk3−/−) than in their wild-type littermates (Sgk3+/+). The present observations disclose a novel mechanism in the regulation of GluR1.
TL;DR: This is the first report of methanesulfonate-degrading bacteria from the Antarctic and of methylotrophy in Afipia, and the first description of any bacterium able to use both methanesolfonate and dimethylsulfone.
Abstract: Three novel strains of methylotrophic Afipia felis were isolated from several locations on Signy Island, Antarctica, and a fourth from estuary sediment from the River Douro, Portugal. They were identified as strains of the alpha-2 proteobacterium A. felis by 16S rRNA gene sequence analysis. Two strains tested were shown to contain the fdxA gene, diagnostic for A. felis. All strains grew with methanesulfonate (and two strains with dimethylsulfone) as sole carbon substrate. Growth on methanesulfonate required methanesulfonate monooxygenase (MSAMO), using NADH as the reductant and stimulated by reduced flavin nucleotides and Fe(II). Polymerase chain reaction amplification of DNA from an Antarctic strain showed a typical msmA gene for the alpha-hydroxylase of MSAMO, and both Antarctic and Portuguese strains contained mxaF, the methanol dehydrogenase large subunit gene. This is the first report of methanesulfonate-degrading bacteria from the Antarctic and of methylotrophy in Afipia, and the first description of any bacterium able to use both methanesulfonate and dimethylsulfone. In contrast, the type strain of A. felis DSM 7326(T) was not methylotrophic, but grew in defined mineral medium with a wide range of single simple organic substrates. Free-living Afipia strains occurring widely in the natural environment may be significant as methylotrophs, degrading C(1)-sulfur compounds, including the recalcitrant organosulfur compound methanesulfonate.
TL;DR: SGK3 is required for adequate intestinal Na+ coupled glucose transport and impaired glucose absorption may contribute to delayed growth and decreased plasma glucose concentrations of SGK3 deficient mice.
Abstract: Xenopus oocyte coexpression experiments revealed the capacity of the serum- and glucocorticoid-inducible kinase isoform 3 (SGK3) to up-regulate a variety of transport systems including the sodium-dependent glucose transporter SGLT1. The present study explored the functional significance of SGK3-dependent regulation of intestinal transport. To this end, experiments were performed in gene targeted mice lacking functional sgk3 (sgk3−/−) and their wild type littermates (sgk3+/+). Oral food intake and fecal dry weight were significantly larger in sgk3−/− than in sgk3+/+ mice. Glucose-induced current (Ig) in Ussing chamber as a measure of Na+ coupled glucose transport was significantly smaller in sgk3−/− than in sgk3+/+ mouse jejunal segments. Fasting plasma glucose concentrations were significantly lower in sgk3−/− than in sgk3+/+ mice. Intestinal electrogenic transport of phenylalanine, cysteine, glutamine and proline were not significantly different between sgk3−/− and sgk3+/+ mice. In conclusion, SGK3 is required for adequate intestinal Na+ coupled glucose transport and impaired glucose absorption may contribute to delayed growth and decreased plasma glucose concentrations of SGK3 deficient mice. The hypoglycemia might lead to enhanced food intake to compensate for impaired intestinal absorption.
TL;DR: A novel interaction is shown between Hook1 and Ankyrin G, an adaptor protein that binds the spectrin-actin cytoskeleton and targets proteins to the peripheral membrane that could lead to alterations in the functioning and positioning of organelles and membrane proteins through this Hook1-AnkyrinG interaction.
TL;DR: Batten patients did not possess autoantibodies against other type 1 diabetes-associated autoantigens and human leukocyte antigen genotypes revealed no specific associations with this disease.
Abstract: The pathogenic mechanisms underlying Batten disease are unclear. Patients uniformly possess autoantibodies against glutamic acid decarboxylase (GAD) that are predominantly reactive with a region of GAD (amino acids 1 to 20) distinct from subjects with autoimmune type 1 diabetes or stiff-person syndrome. Batten patients did not possess autoantibodies against other type 1 diabetes-associated autoantigens and human leukocyte antigen genotypes revealed no specific associations with this disease.
TL;DR: Using a mouse model of the most severe form of NCL (the PPT1 knockout mouse), it is shown that accumulated LLOs are not the result of a defect in LLO synthesis, extension, or transfer but rather are catabolic intermediates derived from LLO degradation.
Abstract: The neuronal ceroid lipofuscinoses (NCLs, also known collectively as Batten disease) are a group of lysosomal storage disorders characterized by the accumulation of autofluorescent storage material in the brain and other tissues. A number of genes underlying various forms of NCL have been cloned, but the basis for the neurodegeneration in any of these is unknown. High levels of dolichol pyrophosphoryl oligosaccharides have previously been demonstrated in brain tissue from several NCL patients, but the specificity of the effect for the NCLs has been unclear. In the present study, we examine eight mouse models of lysosomal storage disorders by modern FACE and found striking lipid-linked oligosaccharide (LLO) accumulation in NCL mouse models (especially CLN1, CLN6, and CLN8 knockout or mutant mice) but not in several other lysosomal storage disorders affecting the brain. Using a mouse model of the most severe form of NCL (the PPT1 knockout mouse), we show that accumulated LLOs are not the result of a defect in LLO synthesis, extension, or transfer but rather are catabolic intermediates derived from LLO degradation. LLOs are enriched about 60-fold in the autofluorescent storage material purified from PPT1 knockoutmouse brain but comprise only 0.3% of the autofluorescent storage material by mass. The accumulation of LLOs is postulated to result from inhibition of late stages of lysosomal degradation of autophagosomes, which may be enriched in these metabolic precursors.
Journal Article•
TL;DR: Analysis of the ribosomal DNA internally transcribed spacer (ITS) and 18s subunit sequences showed the fungus to be distinct from other Paecilomyces species, and suggested a close relationship with Cordyceps species.
Abstract: A monophialidic species of Paecilomyces was isolated from the Antarctic springtail Cryptopygus antarcticus in the peninsular Antarctic The fungus emerged through the carapace of dead arthropods during incubation at 4oC, and produced colonies on agar media at both 4 and 17oC The fungus was morphologically similar to a number of existing monophialidic species of Paecilomyces, but differed in colony pigmentation, the size of phialides and conidial features Analysis of the ribosomal DNA internally transcribed spacer (ITS) and 18s subunit sequences showed the fungus to be distinct from other Paecilomyces species, and suggested a close relationship with Cordyceps species The new species Paecilomyces antarcticus is described
TL;DR: A novel mutation identified as a G to T transversion at nucleotide 49 (G49T) in exon 2 of CLN3, introducing a premature stop codon (E17X) near the N-terminus represents the most 5' mutation described to date.
04 Sep 2005
TL;DR: A standards-based architecture that enables ubiquitous access to distributed speech and multimodal services and maximally leverages existing mobile content ecosystems is presented.
Abstract: In this paper we present a standards-based architecture that enables ubiquitous access to distributed speech and multimodal services. Motorola's “Seamless Mobility” initiatives are focused on giving people continuity of services regardless of context, location, device, or type of network connectivity. Speech technology is a key aspect of seamless mobility: not only does it make it easier to enter information on small devices, but it allows devices to be used in contexts where eyes and hands cannot be used. But the visual modality comprised of keypad input and display output is also vital: speech input can't be used in very noisy environments or where privacy is an issue, and speech output is difficult to remember. Multimodal systems combining visual, speech, and other modalities are therefore crucial for seamless mobility. The architecture depends on standard VoIP protocols such as SIP and RTP. It also uses standard web languages for voice dialogs (VoiceXML) and visual dialogs (XHTML, J2ME). And to provide very high performance speech recognition we use the Distributed Speech Recognition (DSR) standards. The result is a responsive system that places minimal demands on the device and maximally leverages existing mobile content ecosystems.
TL;DR: ADD appeared to be specifically suppressed to various extents by deletions of any of the YME1, AFG3, or RCA1 genes encoding membrane-associated mitochondrial proteases, probably because the amphipathic structures caused a stronger association with the mitochondrial inner membrane and its associated proteases.
Abstract: The dispensable N-terminus of iso-1-cytochrome c (iso-1) in the yeast Saccharomyces cerevisiae was replaced by 11 different amphipathic structures. Rapid degradation of the corresponding iso-1 occurred, with the degree of degradation increasing with the amphipathic moments; and this amphipathic-dependent degradation was designated ADD. ADD occurred with the holo-forms in the mitochondria but not as the apo-forms in the cytosol. The extreme mutant type degraded with a half-life of approximately 12 min, whereas the normal iso-1 was stable over hours. ADD was influenced by the ρ+/ρ− state and by numerous chromosomal genes. Most importantly, ADD appeared to be specifically suppressed to various extents by deletions of any of the YME1, AFG3, or RCA1 genes encoding membrane-associated mitochondrial proteases, probably because the amphipathic structures caused a stronger association with the mitochondrial inner membrane and its associated proteases. The use of ADD assisted in the differentiation of substrates of different mitochondrial degradation pathways.
Journal Article•
TL;DR: The use of intracell handoffs in this environment can provide capacities in excess of any scheme that does not use 100% frequency re-use, and it is shown that previously reported optimum schemes concerning the use of adaptive modulation and coding, channel selection and power control have to be modified when intraceLL handoffs are considered.
Abstract: Fixed wireless schemes are increasingly being used for broadband access, and maximising the spectrum efficiency is an important concern for these applications. However, the fixed wireless access environment differs from the more widely studied mobile cellular case, and the optimum algorithms for achieving high spectrum efficiencies are different, since intercell handoff and fast fading are in many cases not significant concerns. We show that the use of intracell handoffs in this environment can provide capacities in excess of any scheme that does not use 100% frequency re-use. Further, we show that previously reported optimum schemes concerning the use of adaptive modulation and coding, channel selection and power control have to be modified when intracell handoffs are considered.