bluuebunny/crossref_metadata_2025_split huggingface dataset:
The significance of the mutated divalent metal transporter (DMT1) on iron transport into the Belgrade rat brain
Authors: Moos Torben , Morgan Evan H. 
Published: July 2010

AbstractBrain iron transport and distributional pattern of divalent metal transporter I (DMT1) were studied in homozygous Belgrade rats (b/b) which suffer from a mutation in the DMT1 gene. In adult rats, brain uptake of transferrin‐bound iron injected intravenously (i.v.) was significantly lower compared with that in heterozygous Belgrade (+/b) and Wistar rats, whereas transferrin uptake was identical. The difference in iron uptake was not apparent until 30 min after injection. The brain iron concentration was lower, and neuronal transferrin receptor‐immunoreactivity higher, in adult b/b rats, thus confirming their iron‐deficient stage. Antibodies targeting different sites on the DMT1 molecule consistently detected DMT1 in neurones and choroid plexus at the same level irrespective of strain, but failed to detect DMT1 in brain capillary endothelial cells (BCECs), or macro‐ or microglial cells. The absence of DMT1 in BCECs was confirmed in immunoblots of purified BCECs. DMT1 was virtually undetectable in neurones of rats aged 18 post‐natal days irrespective of strain. Neuronal expression of transferrin receptors and DMT1 in adult rats implies that neurones at this age acquire iron by receptor‐mediated endocytosis of transferrin followed by iron transport out of endosomes mediated by DMT1. The existence of the mutated DMT1 molecule in neurones suggests that the low cerebral iron uptake in b/b rats derives from a reduced neuronal uptake rather than an impaired iron transport through the blood–brain barrier.
Enhanced detection and retrograde axonal transport of PrPc in peripheral nerve
Authors: Moya Kenneth L. , Hässig Raymonde , Créminon Christophe , Laffont Isabelle , Di Giamberardino Luigi 
Published: July 2010

AbstractNeuroinvasion of the CNS during orally acquired transmissible spongiform encephalopathies (TSEs) may involve the transport of the infectious agent from the periphery to the CNS via the peripheral nerves. If this occurs within axons, the mechanism of axonal transport may be fundamental to the process. In studies of peripheral nerve we observed that the cellular prion protein (PrPc) is highly resistant to detergent extraction. The implication of this is an underestimation of the abundance of PrPc in peripheral nerve. We have developed nerve extraction conditions that enhance the quantification of the protein in nerve 16‐fold. Application of these conditions to evaluate the accumulation of PrPc distal to a cut nerve now reveals that PrPc is retrogradely transported from the axon ending. These results provide a potential cellular mechanism for TSE infectivity to gain entry to the CNS from the periphery.
Axonal transport of human α‐synuclein slows with aging but is not affected by familial Parkinson's disease‐linked mutations
Authors: Li Wenxue , Hoffman Paul N. , Stirling Wanda , Price Donald L. , Lee Michael K. 
Published: July 2010

AbstractBiochemical and genetic abnormalities of α‐synuclein (α‐Syn) are implicated in the pathogenesis of Parkinson's disease (PD) and other α‐synucleinopathies. The abnormal intraneuronal accumulations of α‐Syn in Lewy bodies (LBs) and Lewy neurites (LNs) have implicated defects in axonal transport of α‐Syn in the α‐synucleinopathies. Using human (Hu) α‐Syn transgenic (Tg) mice, we have examined whether familial PD (FPD)‐linked mutations (A30P and A53T) alter axonal transport of Huα‐Syn. Our studies using peripheral nerves show that Huα‐Syn and Moα‐Syn are almost exclusively transported in the slow component (SC) of axonal transport and that the FPD‐linked α‐Syn mutations do not have obvious effects on the axonal transport of α‐Syn. Moreover, older pre‐symptomatic A53T Huα‐Syn Tg mice do not show gross alterations in the axonal transport of α‐Syn and other proteins in the SC, indicating that the early stages of α‐synucleinopathy in A53T α‐Syn Tg mice are not associated with gross alterations in the slow axonal transport. However, the axonal transport of α‐Syn slows significantly with aging. Because the rate of axonal transport affects the stability and accumulation of proteins in axons, age‐dependent‐slowing α‐Syn is a likely contributor to axonal aggregation of α‐Syn in α‐synucleinopathy.
Trk is a calmodulin‐binding protein: implications for receptor processing
Authors: Llovera Marta , De Pablo Yolanda , Egea Joaquim , Encinas Mario , Peiró Sandra , Martín‐Zanca Dionisio , Rocamora Nativitat , Comella Joan X. 
Published: July 2010

AbstractThe tyrosine kinase receptors for the neurotrophins (Trk) are a family of transmembrane receptors that regulate the differentiation and survival of different neuronal populations. Neurotrophin binding to Trk leads to the activation of several signalling pathways including a rapid, but moderate, increase in intracellular calcium levels. We have previously described the role of calcium and its sensor protein, calmodulin, in Trk‐activated intracellular pathways. Here we demonstrate that calmodulin is able to precipitate TrkA from PC12 cell lysates. Using recombinant GST‐fusion proteins containing the complete intracellular domain of TrkA, or fragments of this region, we show that calmodulin binds directly to the C‐terminal domain of TrkA in a Ca2+‐dependent manner. We have also co‐immunoprecipitated endogenous Trk and calmodulin in primary cultures of cortical neurones. Moreover, we provide evidence that calmodulin is involved in the regulation of TrkA processing in PC12 cells. Calmodulin inhibition results in the generation of a TrkA‐derived p41 fragment from the cytosolic portion of the protein. This fragment is autophosphorylated in tyrosines and can recruit PLCγ and Shc adaptor proteins. These results suggest that calmodulin binding to Trk may be important for the regulation of Trk intracellular localization and cleavage.
Topiramate modulation of kainate‐induced calcium currents is inversely related to channel phosphorylation level
Authors: Ängehagen Mikael , Ben‐Menachem Elinor , Shank Richard , Rönnbäck Lars , Hansson Elisabeth 
Published: July 2010

AbstractTopiramate (TPM) is a structurally novel broad‐spectrum anticonvulsant known to modulate the activity of several ligand‐ and voltage‐gated ion channels in neurons. These include an inhibitory effect on the AMPA and kainate subtypes of glutamate receptors, mixed modulatory effects (usually positive) on some types of GABAA receptors, negative modulatory effects on some types of voltage‐gated Na+ and Ca2+ channels, and a positive modulatory effect on at least one type of K+ channel. The nature of these effects at the molecular level has not been established, but two previous studies have implicated the phosphorylation state of these receptor/channel complexes as an influencing factor in the activity of TPM. Here, we report that the ability of TPM to inhibit a kainate‐induced accumulation of free Ca2+ in cultured neurons from rat cerebral cortex is inversely related to the level of cAMP‐dependent protein kinase (cAPK) mediated phosphorylation of kainate‐activated receptors/channels. Specifically, when cell cultures were pre‐treated with forskolin or dibutyryl cAMP, indirect activators of cAPK, the activity of TPM was abolished, whereas when the cells were pre‐treated with H89, an inhibitor of cAPK, the relative activity of TPM was enhanced. The results of this study support the hypothesis that TPM binds to phosphorylation sites on AMPA and kainate receptors, but only in the dephosphorylated state and thereby exerts an allosteric modulatory effect on channel conductance.
PrPc on the road: trafficking of the cellular prion protein
Authors: Prado Marco A. M. , Alves‐Silva Juliana , Magalhães Ana C. , Prado Vania F. , Linden Rafael , Martins Vilma Regina , Brentani Ricardo Renzo 
Published: July 2010

AbstractThe glycosylphosphatidylinositol (GPI)‐anchored cellular prion protein (PrPc) has a fundamental role in prion diseases. Intracellular trafficking of PrPc is important in the generation of protease resistant PrP species but little is known of how endocytosis affects PrPc function. Here, we discuss recent experiments that have illuminated how PrPc is internalized and what are the possible destinations taken by the protein. Contrary to what would be expected for a GPI‐anchored protein there is increasing evidence that clathrin‐mediated endocytosis and classical endocytic organelles participate in PrPc trafficking. Moreover, the N‐terminal domain of PrPc may be involved in sorting events that can direct the protein during its intracellular journey. Indeed, the concept that the GPI‐anchor determines PrPc trafficking has been challenged. Cellular signaling can be triggered or be regulated by PrPc and we suggest that endocytosis of PrPc may influence signaling in several ways. Definition of the processes that participate in PrPc endocytosis and intracellular trafficking can have a major impact on our understanding of the mechanisms involved in PrPc function and conversion to protease resistant conformations.
Expression of SOD1 G93A or wild‐type SOD1 in primary cultures of astrocytes down‐regulates the glutamate transporter GLT‐1: lack of involvement of oxidative stress
Authors: Tortarolo Massimo , Crossthwaite Andrew J. , Conforti Laura , Spencer Jeremy P. , Williams Robert J. , Bendotti Caterina , Rattray Marcus 
Published: July 2010

AbstractGlutamate excitotoxicity is implicated in the aetiology of amyotrophic lateral sclerosis (ALS) with impairment of glutamate transport into astrocytes a possible cause of glutamate‐induced injury to motor neurons. It is possible that mutations of Cu/Zn superoxide dismutase (SOD1), responsible for about 20% of familial ALS, down‐regulates glutamate transporters via oxidative stress. We transfected primary mouse astrocytes to investigate the effect of the FALS‐linked mutant hSOD1G93A and wild‐type SOD1 (hSOD1wt) on the glutamate uptake system. Using western blotting, immunocytochemistry and RT‐PCR it was shown that expression of either hSOD1G93A or hSOD1wt in astrocytes produced down‐regulation of the levels of a glutamate transporter GLT‐1, without alterations in its mRNA level. hSOD1G93A or hSOD1wt expression caused a decrease of the monomeric form of GLT‐1 without increasing oxidative multimers of GLT‐1. The effects were selective to GLT‐1, since another glutamate transporter GLAST protein and mRNA levels were not altered. Reflecting the decrease in GLT‐1 protein, [3H]d‐aspartate uptake was reduced in cultures expressing hSOD1G93A or hSOD1wt. The hSOD1‐induced decline in GLT‐1 protein and [3H]d‐aspartate uptake was not blocked by the antioxidant Trolox nor potentiated by antioxidant depletion using catalase and glutathione peroxidase inhibitors. Measurement of 2′,7′‐dichlorofluorescein (DCF)‐induced fluorescence revealed that expression of hSOD1G93A or hSOD1wt in astrocytes does not lead to detectable increase of intracellular reactive oxygen species. This study suggests that levels of GLT‐1 protein in astrocytes are reduced rapidly by overexpression of hSOD1, and is due to a property shared between the wild‐type and G93A mutant form, but does not involve the production of intracellular oxidative stress.
X11α impairs γ‐ but not β‐cleavage of amyloid precursor protein
Authors: King Gwendalyn D. , Cherian Kay , Turner R. Scott 
Published: July 2010

AbstractThe phosphotyrosine binding domain of the neuronal protein X11α/mint‐1 binds to the C‐terminus of amyloid precursor protein (APP) and inhibits catabolism to β‐amyloid (Aβ), but the mechanism of this effect is unclear. Coexpression of X11α or its PTB domain with APPswe inhibited secretion of Aβ40 but not APPsβswe, suggesting inhibition of γ‐ but not β‐secretase. To further probe cleavage(s) inhibited by X11α, we coexpressed β‐secretase (BACE‐1) or a component of the γ‐secretase complex (PS‐1Δ9) with APP, APPswe, or C99, with and without X11α, in HEK293 cells. X11α suppressed the PS‐1Δ9‐induced increase in Aβ42 secretion generated from APPswe or C99. However, X11α did not impair BACE‐1‐mediated proteolysis of APP or APPswe to C99. In contrast to impaired γ‐cleavage of APPswe, X11α or its PTB domain did not inhibit γ‐cleavage of NotchΔE to NICD (the Notch intracellular domain). The X11α PDZ–PS.1Δ9 interaction did not affect γ‐cleavage activity. In a cell‐free system, X11α did not inhibit the catabolism of APP C‐terminal fragments. These data suggest that X11α may inhibit Aβ secretion from APP by impairing its trafficking to sites of active γ‐secretase complexes. By specifically targeting substrate instead of enzyme X11α may function as a relatively specific γ‐secretase inhibitor.
Glucocorticoids modulate neurotransmitter‐induced glycogen metabolism in cultured cortical astrocytes
Authors: Allaman Igor , Pellerin Luc , Magistretti Pierre J. 
Published: July 2010

AbstractGlucocorticoids (GC) are considered as key modulators of glycogen homeostasis in peripheral tissues, but their role in the central nervous system has only partially been characterized. Exposure of primary cultures of cortical astrocytes to dexamethasone (DEX), a synthetic glucocorticoid, results in the reduction of noradrenaline (NA)‐induced glycogen synthesis in a concentration‐dependent manner with a IC50 of 4.88 nm and a maximum inhibition of 51%. Such an effect is mediated via glucocorticoid receptors (GRs), since it is mimicked by the glucocorticoid analogue RU28362 (100 nm) and prevented by the GR antagonist RU38486 (1 µm). DEX does not act through alteration of signal transduction mechanisms, as cAMP formation induced by noradrenergic stimulation was unchanged. Moreover, glycogen synthesis was inhibited to the same extent when DEX was applied either together or only after a brief NA application. Neither [3H]2‐deoxyglucose uptake nor lactate release was altered by DEX in the presence of NA, demonstrating that inhibition of glycogen synthesis is not a consequence of reduced glucose utilization or availability. Interestingly, enhancement of glycogen synthase activity induced by NA was reduced in the presence of DEX (−27%). These results suggest that GC could have a significant influence on neuroenergetics as they could modulate activity‐related changes in brain glycogen metabolism.
HSP27 but not HSP70 has a potent protective effect against α‐synuclein‐induced cell death in mammalian neuronal cells
Authors: Zourlidou Alexandra , Payne Smith Martin D. , Latchman David S. 
Published: July 2010

Abstractα‐Synuclein is a neuronally expressed protein which is mutated in familial Parkinson's disease. We have previously shown that disease‐associated mutants of α‐synuclein cause enhanced neuronal cell death in response to a variety of stimuli, whereas wild‐type α‐synuclein has a protective effect against some stimuli, whilst enhancing the death response to others. We demonstrate, for the first time, that over‐expression of the heat shock protein HSP27 has a potent protective anti‐apoptotic effect against the damaging effects of wild‐type and particularly of mutant α‐synuclein. In contrast, HSP70 has some protective effect against the damaging effect of the wild‐type protein, but has no effect against the mutant proteins, whilst HSP56 has no protective effect in this system. Our results indicate that disease‐associated mutants of α‐synuclein enhance its death‐inducing properties and lead to increased apoptosis, which can be mitigated by either the use of specific caspase inhibitors or HSP27 over‐expression. This potent protective effect of HSP27 against the mutant and wild‐type proteins may be of potential therapeutic importance.
DNA methylation as an epigenetic regulator of neural 5‐lipoxygenase expression: evidence in human NT2 and NT2‐N cells
Authors: Zhang Zhijing , Chen Chang‐qing , Manev Hari 
Published: July 2010

AbstractIncreased expression of 5‐lipoxygenase is associated with various neuropathologies and may be related to epigenetic gene regulation. DNA methylation in promoter regions is typically associated with gene silencing. We found that human NT2 cells, which differentiate into neuron‐like NT2‐N cells, express 5‐lipoxygenase and we investigated the relationship between 5‐lipoxygenase expression and the methylation state of the 5‐lipoxygenase core promoter. We used the demethylating agent 5‐aza‐2′‐deoxycytidine and the histone deacetylase inhibitor valproate to alter DNA methylation and to induce histone modifications. 5‐Lipoxygenase expression and DNA methylation were assayed with RT‐PCR and bisulfite genomic sequencing, respectively. Neuronal differentiation of proliferating NT2 precursors decreased 5‐lipoxygenase expression. 5‐Aza‐2′‐deoxycytidine increased 5‐lipoxygenase mRNA levels only in proliferating cells, whereas valproate increased 5‐lipoxygenase mRNA levels in a cell cycle‐independent manner. In both precursors and differentiated cells, CpG dinucleotides of the promoter were poorly methylated. In precursors, both 5‐aza‐2′‐deoxycytidine and valproate further reduced the number of methylated CpGs. Moreover, we found evidence for cytosine methylation in CpWpG (W = adenine or thymine) and other asymmetrical sequences; CpWpG methylation was reduced by valproate in NT2‐N but not in NT2 cells. This is the first report demonstrating that the dynamics of DNA methylation relates to neural 5‐lipoxygenase gene expression.
Proteomic analysis of brain proteins in the gracile axonal dystrophy (gad) mouse, a syndrome that emanates from dysfunctional ubiquitin carboxyl‐terminal hydrolase L‐1, reveals oxidation of key proteins
Authors: Castegna Alessandra , Thongboonkerd Visith , Klein Jon , Lynn Bert C. , Wang Yu‐Lai , Osaka Hitoshi , Wada Keiji , Butterfield D. Allan 
Published: July 2010

AbstractUbiquitin carboxyl‐terminal hydrolase L‐1 (UCH L‐1) is a crucial enzyme for proteasomal protein degradation that generates free monomeric ubiquitin. Our previous proteomic study identified UCH L‐1 as one specific target of protein oxidation in Alzheimer's disease (AD) brain, establishing a link between the effect of oxidative stress on protein and the proteasomal dysfunction in AD. However, it is unclear how protein oxidation affects function, owing to the different responses of proteins to oxidation. Analysis of systems in which the oxidized protein displays lowered or null activity might be an excellent model for investigating the effect of the protein of interest in cellular metabolism and evaluating how the cell responds to the stress caused by oxidation of a specific protein. The gracile axonal dystrophy (gad) mouse is an autosomal recessive spontaneous mutant with a deletion on chromosome 5 within the gene encoding UCH L‐1. The mouse displays axonal degeneration of the gracile tract. The aim of this proteomic study on gad mouse brain, with dysfunctional UCH L‐1, was to determine differences in brain protein oxidation levels between control and gad samples. The results showed increased protein oxidation in thioredoxin peroxidase (peroxiredoxin), phosphoglycerate mutase, Rab GDP dissociation inhibitor α/ATP synthase and neurofilament‐L in the gad mouse brain. These findings are discussed with reference to the effect of specific protein oxidation on potential mechanisms of neurodegeneration that pertain to the gad mouse.
Detection of basal and potassium‐evoked acetylcholine release from embryonic DRG explants
Authors: Bernardini Nadia , Tomassy Giulio Srubek , Tata Ada Maria , Augusti‐Tocco Gabriella , Biagioni Stefano 
Published: July 2010

AbstractSpontaneous and potassium‐induced acetylcholine release from embryonic (E12 and E18) chick dorsal root ganglia explants at 3 and 7 days in culture was investigated using a chemiluminescent procedure. A basal release ranging from 2.4 to 13.8 pm/ganglion/5 min was detected. Potassium application always induced a significant increase over the basal release. The acetylcholine levels measured in E12 explants were 6.3 and 38.4 pm/ganglion/5 min at 3 and 7 days in culture, respectively, while in E18 explant cultures they were 10.7 and 15.5 pm/ganglion/5 min. In experiments performed in the absence of extracellular Ca2+ ions, acetylcholine release, both basal and potassium‐induced, was abolished and it was reduced by cholinergic antagonists. A morphometric analysis of explant fibre length suggested that acetylcholine release was directly correlated to neurite extension. Moreover, treatment of E12 dorsal root ganglion‐dissociated cell cultures with carbachol as cholinergic receptor agonist was shown to induce a higher neurite outgrowth compared with untreated cultures. The concomitant treatment with carbachol and the antagonists at muscarinic receptors atropine and at nicotinic receptors mecamylamine counteracted the increase in fibre outgrowth. Although the present data have not established whether acetylcholine is released by neurones or glial cells, these observations provide the first evidence of a regulated release of acetylcholine in dorsal root ganglia.
Glial soluble factors regulate the activity and expression of the neuronal glutamate transporter EAAC1: implication of cholesterol
Authors: Canolle B. , Masmejean F. , Melon C. , Nieoullon A. , Pisano P. , Lortet S. 
Published: July 2010

AbstractA co‐ordinated regulation between neurons and astrocytes is essential for the control of extracellular glutamate concentration. Here, we have investigated the influence of astrocytes and glia‐derived cholesterol on the regulation of glutamate transport in primary neuronal cultures from rat embryonic cortices. Glutamate uptake rate and expression of the neuronal glutamate transporter EAAC1 were low when neurons were grown without astrocytes and neurons were unable to clear extracellular glutamate. Treatment of the neuronal cultures with glial conditioned medium (GCM) increased glutamate uptake Vmax, EAAC1 expression and restored the capacity of neurons to eliminate extracellular glutamate. Thus, astrocytes up‐regulate the activity and expression of EAAC1 in neurons. We further showed that cholesterol, present in GCM, increased glutamate uptake activity when added directly to neurons and had no effect on glutamate transporter expression. Furthermore, part of the GCM‐induced effect on glutamate transport activity was lost when cholesterol was removed from GCM (low cholesterol‐GCM) and was restored when cholesterol was added to low cholesterol‐GCM. This demonstrates that glia‐derived cholesterol regulates glutamate transport activity. With these experiments, we provide new evidences for neuronal glutamate transport regulation by astrocytes and identified cholesterol as one of the factors implicated in this regulation.
The three sorCS genes are differentially expressed and regulated by synaptic activity
Authors: Hermey Guido , Plath Niels , Hübner Christian A. , Kuhl Dietmar , Schaller H. Chica , Hermans‐Borgmeyer Irm 
Published: July 2010

AbstractWe have isolated the murine sorCS3 gene, a new member of the family of receptors containing a Vps10p‐domain. Receptors of this family facilitate rapid endocytosis and are thought to be involved in intracellular sorting. SorCS3 and the highly homologous sorCS1 and sorCS2 genes were expressed in a combinatorial, mostly non‐overlapping pattern in both the developing and mature central nervous system. During development, distribution and abundancy of their transcripts was regulated. Moreover, their expression was differentially influenced by neuronal activity in the hippocampus of adult mice. Although kainic acid‐induced seizures had no effect on sorCS2 mRNA levels, they dramatically increased the expression of sorCS1 and sorCS3. The activity‐dependent induction of sorCS1 expression required de novo protein synthesis, whereas that of sorCS3 did not. Our results imply that the three sorCS genes have diverse, but partly overlapping functions in the developing and mature central nervous system.