bluuebunny/crossref_metadata_2025_split huggingface dataset:
Uptake and transport of high‐density lipoprotein (HDL) and HDL‐associated α‐tocopherol by an in vitro blood–brain barrier model
Authors: Balazs Zoltan , Panzenboeck Ute , Hammer Astrid , Sovic Andrea , Quehenberger Oswald , Malle Ernst , Sattler Wolfgang 
Published: March 2006

AbstractThe present study aimed to investigate pathways that contribute to uptake and transcytosis of high‐density lipoproteins (HDLs) and HDL‐associated α‐tocopherol (αTocH) across an in vitro model of the blood–brain barrier (BBB). In primary porcine brain capillary endothelial cells HDL‐associated αTocH was taken up in 10‐fold excess of HDL holoparticles, indicating efficient selective uptake, a pathway mediated by scavenger receptor class B, type I (SR‐BI). SR‐BI was present in caveolae of brain capillary endothelial cells and expressed almost exclusively at the apical membrane. Disruption of caveolae with methyl‐β‐cyclodextrin (CDX) resulted in (mis)sorting of SR‐BI to the basolateral membrane. Immunohistochemistry of porcine brain cryosections revealed SR‐BI expression on brain capillary endothelial cells and presumably astrocytic endfeet. HDL‐associated [14C]αTocH taken up by brain capillary endothelial cells was recovered in sucrose gradient fractions containing the majority of cellular caveolin‐1, the major caveolae‐associated protein. During mass transfer studies using αTocH‐enriched HDL, approximately 50% of cellular αTocH was recovered with the bulk of cellular caveolin‐1 and SR‐BI. Efflux experiments revealed that a substantial amount of cell‐associated [14C]αTocH could be mobilized into the culture medium. In addition, apical‐to‐basolateral transport of HDL holoparticles and HDL‐associated αTocH was saturable. Results from the present study suggest that part of cerebral apolipoprotein A‐I and αTocH originates from plasma HDL transcytosed across the BBB and that caveolae‐located SR‐BI facilitates selective uptake of HDL‐associated αTocH at the BBB.
Modulating huntingtin half‐life alters polyglutamine‐dependent aggregate formation and cell toxicity
Authors: Kaytor Michael D. , Wilkinson Keith D. , Warren Stephen T. 
Published: March 2006

AbstractA common finding among the expanded polyglutamine disorders is intracellular protein aggregates. Although the precise role of these aggregates in the disease process is unclear, they are generally ubiquitinated, implicating the ubiquitin–proteasome pathway in neuronal degeneration. To investigate the mechanism of aggregate formation, we have developed a cell culture model to express huntingtin designed to have an altered degradation rate through the ubiquitin‐dependent N‐end rule pathway. We fused the first 171 amino acids of huntingtin, containing either a pathogenic or normal polyglutamine tract, to the enhanced green fluorescent protein (EGFP). The half‐life of soluble huntingtin‐EGFP was dependent on the degradation signal and the polyglutamine tract length. However, once huntingtin‐EGFP with a pathogenic tract had aggregated, the protein was extremely stable. Huntingtin‐EGFP with a pathogenic glutamine tract and a shorter half‐life displayed a delayed onset of aggregate formation and was more toxic to transfected cells. These data suggest that rapid clearance through the ubiquitin–proteasome pathway slows aggregate formation, yet increases cellular toxicity. Polyglutamine‐induced neurotoxicity may therefore be triggered by non‐aggregated protein, and aggregate formation itself may be a cellular defense mechanism.
N‐linked glycosylation sites of the motor protein prestin: effects on membrane targeting and electrophysiological function
Authors: Matsuda Keiji , Zheng Jing , Du Guo‐Guang , Klöcker Nikolaj , Madison Laird D. , Dallos Peter 
Published: March 2006

AbstractPrestin is a motor protein of outer hair cells (OHC) that plays a crucial role in mammalian hearing. Prestin is a putative N‐glycoprotein with three potential N‐linked glycosylation sites. It is not known whether glycosylation affects the function and activity of prestin. Therefore, the effects of N‐glycosylation were investigated by producing single‐point (N163Q and N166Q) or double‐point mutations (NN163/166QQ and NN163/166AA) at putative N‐glycosylation sites. Further, treatment with tunicamycin or glycopeptidase‐F was used to determine the consequences of removing N‐linked glycosylation in wild‐type prestin. We determined the effects of these manipulations on prestin's cell surface expression, molecular mass, glycosylation pattern, and electrophysiological properties in different cell‐types. Data indicate that prestin is a glycoprotein with N‐linked glycosylation sites at N163 and N166. N163 and N166 may have differential programs for synthesis and trimming of the glycans. The N166 site appears to have greater extent of glycosylation than its companion. N‐linked glycosylation is not required for plasma membrane targeting of prestin. Both glycosylated and deglycosylated prestin demonstrate non‐linear capacitance, a signature of prestin's motor function. Compared to glycosylated prestin, the fully de‐glycosylated protein has altered electrophysiological function, with a change in membrane potential at most effective charge transfer to more depolarized values. These data suggest that glycosylation of prestin may quantitatively affect OHC electromotility.
Specific molecular alterations in the norpA‐encoded phospholipase C of Drosophila and their effects on electrophysiological responses in vivo
Authors: Yoon Jaeseung , Leung Hung‐Tat , Lee Seunghee , Geng Chaoxian , Kim Younkyung , Baek Kwanghee , Pak William L. 
Published: March 2006

AbstractA large number of mutants in the norpA gene, which encodes the phospholipase C (PLC) involved in Drosophila phototransduction, is available for the investigation of the effects of specific amino acid substitutions in PLC on biochemical and electrophysiological properties of these mutants. Of the 47 norpA mutants screened for PLC protein content, all but one (H43) displayed drastically decreased amounts of the protein suggesting that almost any mutational alteration has a deleterious effect on the integrity of the protein. Three new amino acids were identified in the catalytic domains X and Y that are important for PLC catalytic activity and the generation of photoreceptor responses (ERG). One of them was found substituted in H43, which showed a low specific PLC activity, a pronounced decrease in ERG sensitivity, and a wild‐type‐like response termination time. The response termination times obtained from three mutants was found to be approximately inversely proportional to the amount of PLC. In addition, we show that (i) the specific PLC activity is a key factor determining the photoreceptor sensitivity; (ii) the catalytic activity and response termination are separable functions of PLC; and (iii) a mutation in the putative Gα‐interacting C2 domain causes a preferentially strong defect in latency.
Clearing amyloid through the blood–brain barrier
Authors: Zlokovic Berislav V. 
Published: March 2006

AbstractAccording to the amyloid hypothesis, accumulation of amyloid β‐peptide (Aβ) in the brain is the primary pathogenic event in Alzheimer's disease (AD). Recent evidence indicates that Aβ within the intravascular space is linked to Aβ deposited in the brain suggesting that transport of Aβ between the brain, blood and cerebrospinal fluid, and across the blood–brain barrier, regulates brain Aβ. Thus, understanding Aβ exchanges between brain and blood, and vice versa, and developing transport‐based systemic Aβ‐lowering strategies may provide new important insights into pathogenesis and therapeutic control of AD.
Accumulation of protein O‐GlcNAc modification inhibits proteasomes in the brain and coincides with neuronal apoptosis in brain areas with high O‐GlcNAc metabolism
Authors: Liu Kan , Paterson Andrew J. , Zhang Fengxue , McAndrew Joanne , Fukuchi Ken‐Ichiro , Wyss J. Michael , Peng Ling , Hu Yong , Kudlow Jeffrey E. 
Published: March 2006

AbstractAll tissues contain the enzymes that modify and remove O‐GlcNAc dynamically from nucleocytoplasmic proteins. These enzymes have been shown to play a role in the control of transcription, vesicular trafficking and, more recently, proteasome function. Modification by O‐GlcNAc of the 19S cap of the proteasome inhibits proteasomal function. Transcripts of both O‐GlcNAc transferase and O‐GlcNAcase are very abundant in the brain, with the highest concentrations in hippocampal neurons and Purkinje cells. When the on‐rate of modification is favored over the off‐rate by intraventricular administration of a drug, streptozocin, these areas of the brain display the most rapid accumulation of O‐GlcNAc. Cerebral proteasome function is reduced and ubiquitin and p53 accumulate in these brain regions, with the subsequent activation of a p53‐dependent transgene and the endogenous Mdm2 gene. Later, some hippocampal cells, but not Purkinje cells, undergo apoptosis. These observations suggest that the O‐GlcNAc system may participate in neurodegeneration, particularly in the hippocampus.
Alterations in ionotropic glutamate receptor subunits during binge cocaine self‐administration and withdrawal in rats
Authors: Tang Wenxue , Wesley Michael , Freeman Willard M. , Liang Bill , Hemby Scott E. 
Published: March 2006

AbstractChronic cocaine use in humans and animal models is known to lead to pronounced alterations in glutamatergic function in brain regions associated with reinforcement. Previous studies have examined ionotropic glutamate receptor (iGluR) subunit protein level changes following acute and chronic experimenter‐administered cocaine or after withdrawal periods from experimenter‐administered cocaine. To evaluate whether alterations in expression of iGluRs are associated with cocaine reinforcement, protein levels were assessed after binge (8 h/day, 15 days; 24‐h access, days 16–21) cocaine self‐administration and following 2 weeks of abstinence from this binge. Western blotting was used to compare levels of iGluR protein expression (NR1–3B, GluR1–7, KA2) in the ventral tegmental area (VTA), substantia nigra (SN), nucleus accumbens (NAc), striatum and prefrontal cortex (PFC) of rats. iGluR subunits were altered in a time‐dependent manner in all brain regions studied; however, selective alterations in certain iGluR subtypes appeared to be associated with binge cocaine self‐administration and withdrawal in a region‐specific manner. In the SN and VTA, alterations in iGluR protein levels compared with controls occurred only following binge access, whereas in the striatum and PFC, iGluR alterations occurred with binge access and following withdrawal. In the NAc, GluR2/3 levels were increased following withdrawal compared with binge access, and were the only changes observed in this region. Because subunit composition determines the functional properties of iGluRs, the observed changes may indicate alterations in the excitability of dopamine transmission underlying long‐term biochemical and behavioral effects of cocaine.
Bone morphogenetic proteins and neurotrophins provide complementary protection of septal cholinergic function during phosphatase inhibitor‐induced stress
Authors: Nonner Doris , Panickar Kiran , Barrett Ellen F. , Barrett John N. 
Published: March 2006

AbstractCultures of embryonic rat septum were exposed for 24–48 h to 2–5 nm okadaic acid (OA), an inhibitor of pp1A and pp2A phosphatases. This stress killed approximately 75% of neurons. A neurotrophin (NT) combination (nerve growth factor and brain‐derived neurotrophic factor, each 100 ng/mL) plus a bone morphogenetic protein (BMP6 or BMP7, 5 nm) reduced the death of both cholinergic and non‐cholinergic neurons, and preserved choline acetyltransferase (ChAT) activity assayed 2–6 days post‐stress. This NT + BMP combination preserved ChAT activity better than either NTs or BMPs alone, and was effective even if trophic factor addition was delayed until 12 h after stress onset. A general caspase inhibitor (qVD‐OPH, 10 µg/mL) also increased survival of stressed cholinergic neurons, but its protection of ChAT activity was shorter lived than that produced by the NT + BMP combination. Neither the NT + BMP combination nor the caspase inhibitor reduced the OA‐induced increase in tau phosphorylation. These findings indicate that NTs and BMPs have synergistic protective effects against an OA stress, and suggest that at least some of these protective effects occur upstream of caspase activation.
Modulatory action of RFamide‐related peptides on acid‐sensing ionic channels is pH dependent: the role of arginine
Authors: Ostrovskaya O. , Moroz L. , Krishtal O. 
Published: March 2006

AbstractAcid‐sensing ionic channels (ASICs) are involved in such functions of the sensory nervous system as mechanoreception, nociception and perception of acid taste. Phe‐Met‐Arg‐Phe amide‐related (FMRFa‐related) peptides in µm concentrations slow down the rate of ASICs desensitization. Here we report that this effect is strongly pH dependent: the lower the pH used to activate ASICs, the larger is the modulatory effect of Arg‐Phe amide‐related (RFa‐related) peptides. Pre‐application of the peptides results in a change to the desensitization kinetics of the ASICs‐operated current from monoexponential to biexponential: the fast component retains the control kinetics, whereas the slow one is induced by the peptide. The lower the pH, the larger is the slow component, whereas there is practically no modulation at pH 6.6. Phe‐Met‐Val‐Phe amide (FMVFa), which has neutral valine instead of arginine, similarly modulates the kinetics of ASICs, but does not reveal pH dependence of this action. Thus, positively charged arginine regulates the access of the RFa‐related peptides to the modulatory site. We suggest that the pH dependence of the modulatory action of RFa‐related peptides can be associated with the interaction of a positively charged arginine with histidine residues in the molecule of ASIC.
Increased expression of p62 in expanded polyglutamine‐expressing cells and its association with polyglutamine inclusions
Authors: Nagaoka Utako , Kim Ken , Jana Nihar Ranjan , Doi Hiroshi , Maruyama Mieko , Mitsui Kenichi , Oyama Fumitaka , Nukina Nobuyuki 
Published: March 2006

AbstractHuntington's disease is a progressive neurodegenerative disorder that is associated with a CAG repeat expansion in the gene encoding huntingtin. We found that a 60‐kDa protein was increased in Neuro2a cells expressing the N‐terminal portion of huntingtin with expanded polyglutamine. We purified this protein, and, using mass spectrometry, identified it as p62, an ubiquitin‐associated domain‐containing protein. A specific p62 antibody stained the ubiquitylated polyQ inclusions in expanded polyglutamine‐expressing cells, as well as in the brain of the huntingtin exon 1 transgenic mice. Furthermore, the level of p62 protein and mRNA was increased in expanded polyglutamine‐expressing cells. We also found that p62 formed aggresome‐like inclusions when p62 was increased in normal Neuro2a cells by a proteasome inhibitor. Knock‐down of p62 does not affect the formation of aggresomes or polyglutamine inclusions, suggesting that p62 is recruited to the aggresome or inclusions secondary to their formation. These results suggest that p62 may play important roles as a responsive protein to a polyglutamine‐induced stress rather than as a cross‐linker between ubiquitylated proteins.
Multiple promoters drive tissue‐specific expression of the human M2muscarinic acetylcholine receptor gene
Authors: Krejci Alena , Bruce Alexander W. , Dolezal Vladimir , Tucek Stanislav , Buckley Noel J. 
Published: March 2006

AbstractDespite the wealth of information on the functional and pharmacological properties of the M2muscarinic receptor, we know relatively little of structure and regulation of the M2receptor gene. Here, we describe the organisation of the human M2gene and its promoters. Four exons are present in the 5′ untranslated region of the human M2mRNA distributed over 146 kb on chromosome 7 which produce eight different splice variants in the IMR‐32 neuroblastoma cell line. The unexpectedly large size of this gene indicates that transcription initiates much further upstream of the coding region than earlier studies had indicated. We present evidence that there are three distinct human M2promoters. Analysis of endogenous transcripts revealed that promoter 2 is preferentially used in neuroblastoma cells, whereas promoter 1 in cardiac cells. All promoters are highly conserved across human, mouse, rat and pig. They contain multiple start sites and none possess a TATA‐box. In addition, we describe another M2promoter that is specific for rat. We show that GATA‐4 transcription factor binds to two sites within the regulatory regions of the M2gene using reporter gene assays, electromobility shift assays and mutational analysis.
Plasma membrane oestrogen receptor mediates neuroprotection against β‐amyloid toxicity through activation of Raf‐1/MEK/ERK cascade in septal‐derived cholinergic SN56 cells
Authors: Guerra Borja , Díaz Mario , Alonso Rafael , Marin Raquel 
Published: March 2006

AbstractRapid oestrogen neuroprotection against β‐amyloid peptide (Aβ)‐induced toxicity, a main feature of Alzheimer's disease, may be partially initiated at the plasma membrane. However, the mechanism by which this oestrogen effect occurs is unknown. In a septal murine cell line (SN56), we observed that short exposures to either 17β‐oestradiol (E2) or membrane impermeant E2 bound to horseradish peroxidase (E‐HRP) induced a biphasic stimulation of extracellular‐signal regulated protein kinase (ERK1/2) phosphorylation, with peak inductions detected around 4–8 min in the early phase and a second maximum around 8 h after treatment. ERK1/2 phosphorylation was abolished by ERK1/2 kinase (MEK) inhibitors PD98059 and U0126. Interestingly, PD98059 was also shown to block rapid E2‐related prevention of death in cells exposed to Aβ fragment 1–40 (Aβ1−40) for 24 h. In contrast, no neuroprotective effects were obtained when MEK inhibitor was used to selectively abolish the late phosphorylation phase. Furthermore, both ERK1/2 activation and E2‐associated protection were blocked by an inhibitor of Raf‐1 kinase. Raf‐1 may be involved in these effects because oestrogen caused the rapid serine 338 (Ser338) phosphorylation of this protein. In addition, the oestrogen receptor (ER) antagonist ICI 182 780 was also observed to block ERK1/2 phosphorylation. We propose a novel mechanism in SN56 cells by which rapid effects of oestrogen leading to neuroprotection are signalled through Raf‐1/MEK/ERK1/2 pathway, possibly by activation of a membrane‐related ER.
Effects of morphine on gene expression in the rat amygdala
Authors: Rodriguez Parkitna J. M. , Bilecki W. , Mierzejewski P. , Stefanski R. , Ligeza A. , Bargiela A. , Ziolkowska B. , Kostowski W. , Przewlocki R. 
Published: March 2006

AbstractInfluence of morphine self‐administration on gene expression in the rat amygdala was studied using rat genome DNA arrays U34A from Affymetrix. Animals were trained to self‐administer morphine, each having two ‘yoked’ control animals, receiving passive injections of either morphine or saline. After 40 sessions of self‐administration, amygdalae were removed, total RNA was isolated and used to prepare probes for Genechip® arrays. The treatment was found to significantly change abundance of 29 transcripts. Analysis by means of reverse transcription real‐time PCR showed significant changes in abundance of five transcripts: γ protein kinase C (PKC), upstream binding factor 2 (UBF2), lysozyme, noggin and heat shock protein 70 (hsp70). After 30 days of forced abstinence from morphine self‐administration, abundance of hsp70 and lysozyme returned to basal levels. Changes in abundance of UBF2 persisted, and abundance of three additional genes, namely nuclear factor I/A, γ1 subunit of GABAA receptor and the neuronal calcium sensor 1, changed. Additionally, acute as well as chronic intraperitoneal morphine administration changed the abundance of PKC γ, γ1 subunit of GABAA and hsp70 genes.
The arachidonic acid 5‐lipoxygenase inhibitor nordihydroguaiaretic acid inhibits tumor necrosis factor α activation of microglia and extends survival of G93A‐SOD1 transgenic mice
Authors: West Melinda , Mhatre Molina , Ceballos Alex , Floyd Robert A. , Grammas Paula , Gabbita S. Prasad , Hamdheydari Ladan , Mai Tammy , Mou Shenyun , Pye Quentin N. , Stewart Charles , West Stuart , Williamson Kelly S. , Zemlan Frank , Hensley Kenneth 
Published: March 2006

AbstractFamilial forms of amyotrophic lateral sclerosis (ALS) can be caused by mutations in copper, zinc‐superoxide dismutase (SOD1). Mice expressing SOD1 mutants demonstrate a robust neuroinflammatory reaction characterized, in part, by up‐regulation of tumor necrosis factor alpha (TNFα) and its primary receptor TNF‐RI. In an effort to identify small molecule inhibitors of neuroinflammation useful in treatment of ALS, a microglial culture system was established to identify TNFα antagonists. Walker EOC‐20 microglia cells were stimulated with recombinant TNFα, with or without inhibitors, and the cell response was indexed by NO2– output. Three hundred and fifty‐five rationally selected compounds were included in this bioassay. The arachidonic acid 5‐lipoxygenase (5LOX) and tyrosine kinase inhibitor nordihydroguaiaretic acid (NDGA), a natural dicatechol, was one of the most potent non‐cytotoxic antagonists tested (IC50 8 ± 3 μm). Investigation of the G93A‐SOD1 mouse model for ALS revealed increased message and protein levels of 5LOX at 120 days of age. Oral NDGA (2500 p.p.m.) significantly extended lifespan and slowed motor dysfunction in this mouse, when administration was begun relatively late in life (90 days). NDGA extended median total lifespan of G93A‐SOD1 mice by 10%, and life expectancy following start of treatment was extended by 32%. Disease‐associated gliosis and cleaved microtubule‐associated tau protein, an indicator of axon damage, were likewise reduced by NDGA. Thus, TNFα antagonists and especially 5LOX inhibitors might offer new opportunities for treatment of ALS.
Static, transient and permanent organization of GABAA receptor expression in calbindin‐positive interneurons in response to amygdala kindled seizures
Authors: Meguro R. , Lu J. , Gavrilovici C. , Poulter M. O. 
Published: March 2006

AbstractWe tested the hypothesis that experimentally produced epilepsy (by kindling) may induce changes in GABAA receptor expression in some but not all interneuron populations. Using laser capture microdissection and quantitative polymerase chain reaction (QPCR) analysis, GABAA receptor α subunit expression in calbindin‐ (CBir) and parvalbumin‐ (Parvir) immunoreactive interneurons was compared between normal brains and brains in which amygdala kindled seizure responses were permanently established. Two weeks after the last seizure response, Cbir neurons in the hilus and/or perirhinal cortex up‐regulated the expression of α2, α3 and α5 subunit mRNAs up to 900%. In contrast, no changes were found in Parvir neurons. In Cbir neurons contralateral to the amygdala kindling site α1 subunit mRNA expression was increased. In both Cbir and Parvir neurons, the coordinated subunit expression patterns ipsilateral (fully kindled) and contralateral (partially kindled) to the kindling site suggested that permanent and transient co‐expressional relationships occur respectively. In the perirhinal cortex α2 protein was up‐regulated in the processes but not in the cell somas of calbindin‐positive neurons, whereas α3 subunit protein expression was up‐regulated on the cell bodies of Cbir neurons in the hilus. These data indicate that different interneuron populations may selectively reorganize their GABAA subunit expression in response to seizures.