bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of gene structure and subcellular localization of human centaurin α2, and p42IP4, a family of two highly homologueous, Ins 1,3,4,5‐P4‐/PtdIns 3,4,5‐P3‐binding, adapter proteins
Authors: Hanck Theodor , Stricker Rolf , Sedehizade Fariba , Reiser Georg 
Published: July 2010

AbstractProteins which recognize the two messengers phosphatidylinositol 3,4,5‐trisphosphate (PtdInsP3), a membrane lipid, and inositol 1,3,4,5‐tetrakisphosphate (InsP4), a water‐soluble ligand, play important roles by integrating external stimuli, which lead to differentiation, cell death or survival. p42IP4, a PtdInsP3/InsP4‐binding protein, is predominantly expressed in brain. The recently described centaurin α2 of similar molecular mass which is 58% identical and 75% homologous to the human p42IP4 orthologue, is expressed rather ubiquitously in many tissues. Here, elucidating the gene structure for both proteins, we found the human gene for centaurin α2 located on chromosome 17, position 17q11.2, near to the NF1 locus, and human p42IP4 on chromosome 7, position 7p22.3. The two isoforms, which both have 11 exons and conserved exon/intron transitions, seem to result from gene duplication. Furthermore, we studied binding of the two second messengers, PtdInsP3 and InsP4, and subcellular localization of the two proteins. Using recombinant baculovirus we expressed centaurin α2 and p42IP4 in Sf9 cells and purified the proteins to homogeneity. Recombinant centaurin α2 bound both InsP4 and PtdInsP3 equally well in vitro. Furthermore, fusion proteins of centaurin α2 and p42IP4, respectively, with the green fluorescent protein (GFP) were expressed in HEK 293 cells to visualize subcellular distribution. In contrast to p42IP4, which was distributed throughout the cell, centaurin α2 was concentrated at the plasma membrane already in unstimulated cells. The protein centaurin α2 was released from the membrane upon addition of wortmannin, which inhibits PI3‐kinase. p42IP4, however, translocated to plasma membrane upon growth factor stimulation. Thus, in spite of the high homology between centaurin α2 and p42IP4 and comparable affinities for InsP4 and PtdInsP3, both proteins showed clear differences in subcellular distribution. We suggest a model, which is based on the difference in phosphoinositide binding stoichiometry of the two proteins, to account for the difference in subcellular localization.
Mitochondrial glutaminase enhances extracellular glutamate production in HIV‐1‐infected macrophages: Linkage to HIV‐1 associated dementia
Authors: Zhao Jianxing , Lopez Alicia L. , Erichsen David , Herek Shelley , Cotter Robin L. , Curthoys Norman P. , Zheng Jialin 
Published: July 2010

AbstractDysfunction in mononuclear phagocyte (MP, macrophages and microglia) immunity is thought to play a significant role in the pathogenesis of HIV‐1 associated dementia (HAD). In particular, elevated extracellular concentrations of the excitatory neurotransmitter glutamate, produced by MP as a consequence of viral infection and immune activation, can induce neuronal injury. To determine the mechanism by which MP‐mediated neuronal injury occurs, the concentration and rates of production of extracellular glutamate were measured in human monocyte‐derived macrophage (MDM) supernatants by reverse phase high‐performance liquid chromatography (RP‐HPLC). Measurements were taken of supernatants from MDM infected with multiple HIV‐1 strains including ADA and DJV (macrophage tropic, M‐tropic), and 89.6 (dual tropic). High levels of glutamate were produced by MDM infected with M‐tropic viruses. AZT, an inhibitor of HIV‐1 replication, inhibited glutamate generation, demonstrating a linkage between HIV‐1 infection and enhanced glutamate production. In our culture system, glutamate production was dependent upon the presence of glutamine and was inhibited by 6‐diazo‐5‐oxo‐l‐norleucine, a glutaminase inhibitor. Supernatants collected from HIV‐1‐infected MP generated more glutamate following glutamine addition than supernatants isolated from uninfected MP. These findings implicate the involvement of a glutamate‐generating enzyme, such as phosphate‐activated mitochondrial glutaminase (PMG) in MP‐mediated glutamate production.
Delayed but sustained induction of mitogen‐activated protein kinase activity is associated with β‐adrenergic receptor‐mediated morphological differentiation of astrocytes
Authors: Gharami Kusumika , Das Sumantra 
Published: July 2010

AbstractAstroglial β‐adrenergic receptors (β‐ARs) are functionally linked to regulate cellular morphology. In primary cultures, the β‐AR agonist isoproterenol (ISP) can transform flat polygonal astrocytes into process‐bearing, mature stellate cells by 48 h, an effect that can be blocked by the β‐AR antagonist, propranolol. ISP induced immediate activation of protein kinase A (PKA) which persisted up to 2 h, with no visible change in cell morphology. However, activation of PKA was sufficient to drive the process of transformation to completion, suggesting the involvement of downstream regulators of PKA. In addition to PKA inhibitors, the mitogen‐activated protein kinase (MAPK) kinase inhibitor PD098059 also blocked ISP‐induced morphological transformation. ISP treatment resulted in a biphasic response of cellular phosphorylated MAPK (phosphorylated extracellular signal‐regulated kinase; p‐ERK) level: an initial decline in p‐ERK level followed by a sustained induction at 12–24 h, both of which were blocked by PKA inhibitor. The induction in pERK level coincided with initiation of morphological differentiation of the astrocytes and nuclear translocation of p‐ERK. A long‐lasting activation of p‐ERK activity by ISP, at a later stage, appears to be critical for the transformation of astrocytes.
Activation of brain prostanoid EP3 receptors via arachidonic acid cascade during behavioral suppression induced by Δ8‐tetrahydrocannabinol
Authors: Yamaguchi Taku , Kubota Takashi , Watanabe Shigenori , Yamamoto Tsuneyuki 
Published: July 2010

AbstractWe have previously shown that behavioral changes induced by cannabinoid were due to an elevation of prostaglandin E2(PGE2) via the arachidonic acid cascade in the brain. In the present study, we investigated the participation of the prostanoid EP3 receptor, the target of PGE2in the brain, in behavioral suppression induced by Δ8‐tetrahydrocannabinol (Δ8‐THC), an isomer of the naturally occurring Δ9‐THC, using a one‐lever operant task in rats. Intraperitoneal administration of Δ8‐THC inhibited the lever‐pressing behavior, which was significantly antagonized by both the selective cannabinoid CB1 receptor antagonist SR141716A and the cyclooxygenase inhibitor diclofenac. Furthermore, intracerebroventricular (i.c.v.) administration of PGE2significantly inhibited the lever‐pressing performance similar to Δ8‐THC. Prostanoid EP3 receptor antisense‐oligodeoxynucleotide (AS‐ODN; twice a day for 3 days, i.c.v.) significantly decreased prostanoid EP3 receptor mRNA levels as determined by the RT‐PCR analysis in the cerebral cortex, hippocampus and midbrain. AS‐ODN also antagonized the PGE2‐induced suppression of the lever pressing. In the same way, the suppression of lever‐pressing behavior by Δ8‐THC was significantly improved by AS‐ODN. It is concluded that the suppression of lever‐pressing behavior by cannabinoid is due to activation of the prostanoid EP3 receptor through an elevation of PGE2in the brain.
CEP11004, a novel inhibitor of the mixed lineage kinases, suppresses apoptotic death in dopamine neurons of the substantia nigra induced by 6‐hydroxydopamine
Authors: Ganguly Anindita , Oo Tinmarla Frances , Rzhetskaya Margarita , Pratt Robert , Yarygina Olga , Momoi Takashi , Kholodilov Nikolai , Burke Robert E. 
Published: July 2010

AbstractThere is much evidence that the kinase cascade which leads to the phosphorylation of c‐jun plays an important signaling role in the mediation of programmed cell death. We have previously shown that c‐jun is phosphorylated in a model of induced apoptotic death in dopamine neurons of the substantia nigrain vivo. To determine the generality and functional significance of this response, we have examined c‐jun phosphorylation and the effect on cell death of a novel mixed lineage kinase inhibitor, CEP11004, in the 6‐hydroxydopamine model of induced apoptotic death in dopamine neurons. We found that expression of total c‐jun and Ser73‐phosphorylated c‐jun is increased in this model and both colocalize with apoptotic morphology. CEP11004 suppresses apoptotic death to levels of 44 and 58% of control values at doses of 1.0 and 3.0 mg/kg, respectively. It also suppresses, to approximately equal levels, the number of profiles positive for the activated form of capase 9. CEP11004 markedly suppresses striatal dopaminergic fiber loss in these models, to only 22% of control levels. We conclude that c‐jun phosphorylation is a general feature of apoptosis in living dopamine neurons and that the mixed lineage kinases play a functional role as up‐stream mediators of cell death in these neurons.
Membrane properties of rat embryonic multipotent neural stem cells
Authors: Cai Jingli , Cheng Aiwu , Luo Yongquan , Lu Chengbiao , Mattson Mark P. , Rao Mahendra S. , Furukawa Katsutoshi 
Published: July 2010

AbstractWe have characterized several potential stem cell markers and defined the membrane properties of rat fetal (E10.5) neural stem cells (NSC) by immunocytochemistry, electrophysiology and microarray analysis. Immunocytochemical analysis demonstrates specificity of expression of Sox1, ABCG2/Bcrp1, and shows that nucleostemin labels both progenitor and stem cell populations. NSCs, like hematopoietic stem cells, express high levels of aldehyde dehydrogenase (ALDH) as assessed by Aldefluor labeling. Microarray analysis of 96 transporters and channels showed that Glucose transporter 1 (Glut1/Slc2a1) expression is unique to fetal NSCs or other differentiated cells. Electrophysiological examination showed that fetal NSCs respond to acetylcholine and its agonists, such as nicotine and muscarine. NSCs express low levels of tetrodotoxin (TTX) sensitive and insensitive sodium channels and calcium channels while expressing at least three kinds of potassium channels. We find that gap junction communication is mediated by connexin (Cx)43 and Cx45, and is essential for NSC survival and proliferation. Overall, our results show that fetal NSCs exhibit a unique signature that can be used to determine their location and assess their ability to respond to their environment.
Calpain‐mediated proteolytic cleavage of the neuronal glycine transporter, GlyT2
Authors: Baliova Martina , Betz Heinrich , Jursky Frantisek 
Published: July 2010

AbstractThe glycine transporter 2 (GlyT2) belongs to the family of Na+/CL–‐dependent plasma membrane transporters and is localized on the presynaptic terminals of glycinergic neurons. GlyT2 differs from other family members by its extended N‐terminal cytoplasmic region. We report that activation of a Ca2+‐dependent protease, most likely calpain, in spinal cord synaptosomes or cultured spinal cord neurons, results in partial proteolysis of GlyT2. Regions sensitive to calpain cleavagein vivoare located in the N‐terminal and, to a lesser extent, C‐terminal regions of the transporter protein. Incubation of a GlyT2 N‐terminal fusion protein with spinal cord extract in the presence of calcium followed by protein sequence analysis localized the major N‐terminal cleavage site after methionine 156, with a second cleavage site being situated after glycine 164. Interestingly, the size of the N‐terminally truncated GlyT2 protein (70 kDa) is similar to that of most other transporter family members, and truncated GlyT2 displayed full transport activity upon expression in HEK293 cells. Our data suggest that Ca2+‐triggered proteolysis may contribute to the regulation of GlyT2 trafficking and/or function in the neuronal plasma membrane.
Hypoxic remodelling of Ca2+ mobilization in type I cortical astrocytes: involvement of ROS and pro‐amyloidogenic APP processing
Authors: Smith Ian F. , Boyle John P. , Green Kim N. , Pearson Hugh A. , Peers Chris 
Published: July 2010

AbstractChronic hypoxia (CH) alters Ca2+ homeostasis in various cells and may contribute to disturbed Ca2+ homeostasis of Alzheimer's disease. Here, we have employed microfluorimetric measurements of [Ca2+]i to investigate the mechanism underlying augmentation of Ca2+ signalling by chronic hypoxia in type I cortical astrocytes. Application of bradykinin evoked significantly larger rises of [Ca2+]i in hypoxic cells as compared with control cells. This augmentation was prevented fully by either melatonin (150 µm) or ascorbic acid (200 µm), indicating the involvement of reactive oxygen species. Given the association between hypoxia and increased production of amyloid β peptides (AβPs) of Alzheimer's disease, we performed immunofluorescence studies to show that hypoxia caused a marked and consistent increased staining for AβPs and presenilin‐1 (PS‐1). Western blot experiments also confirmed that hypoxia increased PS‐1 protein levels. Hypoxic increases of AβP production was prevented with inhibitors of either γ‐ or β‐secretase. These inhibitors also partially prevented the augmentation of Ca2+ signalling in astrocytes. Our results indicate that chronic hypoxia enhances agonist‐evoked rises of [Ca2+]i in cortical astrocytes, and that this can be prevented by antioxidants and appears to be associated with increased AβP formation.
Brain trauma induces X‐box protein 1 processing indicative of activation of the endoplasmic reticulum unfolded protein response
Authors: Paschen Wulf , Yatsiv Ido , Shoham Shai , Shohami Esther 
Published: July 2010

AbstractBrain trauma was induced in mice using a closed head injury (CHI) model. At 1, 6 or 24 h after trauma, brains were dissected into the cortex, striatum and hippocampus. Changes in levels of processed X‐box protein 1 (xbp1), glucose‐regulated protein 78 (grp78), growth arrest and DNA damage‐inducible gene 153 (gadd153) and heat‐shock protein 70 (hsp70) mRNA, indicating impaired endoplasmic reticulum (ER) and cytoplasmic functioning, were evaluated by quantitative PCR. In the cortex, processed xbp1 mRNA levels rose to 2000% of control 1 h after CHI, and stayed high throughout the experiments. In the hippocampus and striatum, processed xbp1 mRNA levels rose in a delayed fashion, peaking at 6 h (1000% of control) and 24 h after CHI (1500% of control) respectively. Levels of grp78 mRNA were only slightly increased in the cortex 24 h after CHI (150% of control), and were unchanged or transiently decreased in the hippocampus and striatum. Levels of gadd153 mRNA did not change significantly after trauma. A transient rise in hsp70 mRNA levels was observed only in the cortex, peaking at 1 h after CHI (600% of control). Processing of xbp1 mRNA is a sign of activation of the unfolded protein response indicative of ER dysfunction. The results suggest that brain trauma induces ER dysfunction, which spreads from the ipsilateral cortex to the hippocampus and striatum. These observations may have clinical implications and should therefore be considered for future investigations on therapeutic intervention of brain injury caused by contusion‐induced neurotrauma.
Neuregulin‐1‐β1 enters brain and spinal cord by receptor‐mediated transport
Authors: Kastin Abba J. , Akerstrom Victoria , Pan Weihong 
Published: July 2010

AbstractProteins of the neuregulin (NRG) family play important regulatory roles in neuronal survival and synaptic activity. NRG‐1‐β1 has particular potential as a therapeutic agent because it enhances myelination of neurites in spinal cord explants. In this study, we determined the permeation of NRG‐1‐β1 across the blood‐brain and blood–spinal cord barriers (BBB and BSCB respectively). Intact radioactively labeled NRG‐1‐β1 had a saturable and relatively rapid influx rate from blood to the CNS in mice. Capillary depletion studies showed that NRG‐1‐β1 entered the parenchyma of the brain and spinal cord rather than being trapped in the capillaries that compose the BBB. The possible mechanism of receptor‐mediated transport was shown by the ability of antibodies to erbB3 and erbB4 receptors to inhibit the influx. Lipophilicity, less important for such saturable transport mechanisms, was measured by the octanol : buffer partition coefficient and found to be low. The results indicate that NRG‐1‐β1 enters spinal cord and brain by a saturable receptor‐mediated mechanism, which provides the opportunity for possible therapeutic manipulation at the BBB level.
Mice deficient in dihydrolipoamide dehydrogenase show increased vulnerability to MPTP, malonate and 3‐nitropropionic acid neurotoxicity
Authors: Klivenyi Peter , Starkov Anatoly A. , Calingasan Noel Y. , Gardian Gabrielle , Browne Susan E. , Yang Lichuan , Bubber Parvesh , Gibson Gary E. , Patel Mulchand S. , Beal M. Flint 
Published: July 2010

AbstractAltered energy metabolism, including reductions in activities of the key mitochondrial enzymes α‐ketoglutarate dehydrogenase complex (KGDHC) and pyruvate dehydrogenase complex (PDHC), are characteristic of many neurodegenerative disorders including Alzheimer's Disease (AD), Parkinson's disease (PD) and Huntington's disease (HD). Dihydrolipoamide dehydrogenase is a critical subunit of KGDHC and PDHC. We tested whether mice that are deficient in dihydrolipoamide dehydrogenase (Dld+/–) show increased vulnerability to 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP), malonate and 3‐nitropropionic acid (3‐NP), which have been proposed for use in models of PD and HD. Administration of MPTP resulted in significantly greater depletion of tyrosine hydroxylase‐positive neurons in the substantia nigra of Dld+/– mice than that seen in wild‐type littermate controls. Striatal lesion volumes produced by malonate and 3‐NP were significantly increased in Dld+/– mice. Studies of isolated brain mitochondria treated with 3‐NP showed that both succinate‐supported respiration and membrane potential were suppressed to a greater extent in Dld+/– mice. KGDHC activity was also found to be reduced in putamen from patients with HD. These findings provide further evidence that mitochondrial defects may contribute to the pathogenesis of neurodegenerative diseases.
Identification of a residue in the γ‐aminobutyric acid type A receptor α subunit that differentially affects diazepam‐sensitive and ‐insensitive benzodiazepine site binding
Authors: Derry Jason M. C. , Dunn Susan M. J. , Davies Martin 
Published: July 2010

AbstractGABAAreceptors that contain either the α4‐ or α6‐subunit isoform do not recognize classical 1,4‐benzodiazepines (BZDs). However, other classes of BZD site ligands, including β‐carbolines, bind to these diazepam‐insensitive receptor subtypes. Some β‐carbolines [e.g. ethyl β‐carboline‐3‐carboxylate (β‐CCE) and methyl 6,7‐dimethoxy‐4‐ethyl‐β‐carboline‐3‐carboxylate (DMCM)] display a higher affinity for α4‐ compared to α6‐containing receptors. In order to identify the structural determinants that underlie these affinity differences, we constructed chimeric α6/α4 subunits and co‐expressed these with wild‐type rat β2 and γ2Lsubunits in tsA201 cells for radioligand binding analysis. After identification of candidate regions, site‐directed mutagenesis was used to narrow the ligand selectivity to a single amino acid residue (α6N204/α4I203). Substitutions at α6N204 did not alter the affinity of the imidazobenzodiazepine Ro15‐4513. A homologous mutation in the diazepam‐sensitive α1 subunit (S205N) resulted in a 7–8‐fold reduction in affinity for the β‐carbolines examined. Although the binding of the classical agonist flunitrazepam was relatively unaffected by this mutation in the α1 subunit, the affinity for Ro15‐1788 and Ro15‐4513 was decreased by ∼19‐fold and ∼38‐fold respectively. The importance of this residue, located in the Loop C region of the extracellular N‐terminus of the subunit protein, emphasizes the differential interaction of ligands with the α subunit in diazepam‐sensitive and ‐insensitive receptors.
Prothrombin overexpressed in post‐natal neurones requires blood factors for activation in the mouse brain
Authors: Sinnreich Michael , Meins Marita , Niclou Simone P. , Suidan Hana S. , Monard Denis 
Published: July 2010

AbstractThrombin is thought to mediate, through protease‐activated receptors, both protective as well as cytotoxic effects. As thrombin receptors are expressed in the CNS, an important question arises as to whether the intact nervous system is able to generate thrombin by activation of its precursor prothrombin, derived endogenously or only upon extravasation following brain injury. To address this question, transgenic mice that express C‐terminally haemagglutinin tagged human prothrombin in post‐mitotic neurones were generated.In situhybridization and immunohistochemical analysis showed abundant and widespread cerebral expression of the transgene. Amidolytic assays of brain homogenates and hippocampal slice cultures demonstrated that activation of transgenic prothrombin required added factors, such as snake venom or blood components. This strongly suggests that any possible action of thrombin in the adult CNS depends on blood‐derived factors that activate prothrombin. Furthermore, the results are consistent with the idea that in the non‐pathological situation an as yet unidentified ligand activates thrombin receptors in the nervous system.
Cell signaling pathways in the neuroprotective actions of the green tea polyphenol (‐)‐epigallocatechin‐3‐gallate: implications for neurodegenerative diseases
Authors: Mandel Silvia , Weinreb Orly , Amit Tamar , Youdim Moussa B. H. 
Published: July 2010

AbstractAccumulating evidence supports the hypothesis that brain iron misregulation and oxidative stress (OS), resulting in reactive oxygen species (ROS) generation from H2O2and inflammatory processes, trigger a cascade of events leading to apoptotic/necrotic cell death in neurodegenerative disorders, such as Parkinson's (PD), Alzheimer's (AD) and Huntington's diseases, and amyotrophic lateral sclerosis (ALS). Thus, novel therapeutic approaches aimed at neutralization of OS‐induced neurotoxicity, support the application of ROS scavengers, transition metals (e.g. iron and copper) chelators and non‐vitamin natural antioxidant polyphenols, in monotherapy, or as part of antioxidant cocktail formulation for these diseases. Both experimental and epidemiological evidence demonstrate that flavonoid polyphenols, particularly from green tea and blueberries, improve age‐related cognitive decline and are neuroprotective in models of PD, AD and cerebral ischemia/reperfusion injuries. However, recent studies indicate that the radical scavenger property of green tea polyphenols is unlikely to be the sole explanation for their neuroprotective capacity and in fact, a wide spectrum of cellular signaling events may well account for their biological actions. In this article, the currently established mechanisms involved in the beneficial health action and emerging studies concerning the putative novel molecular neuroprotective activity of green tea and its major polyphenol (‐)‐epigallocatechin‐3‐gallate (EGCG), will be reviewed and discussed.