Neurochemistry
Caffeine and an adenosine A(2A) receptor antagonist prevent memory impairment and synaptotoxicity in adult rats triggered by a convulsive episode in early life.
Publication Date: 2009 Oct 30 PMID: 19878534
Authors: Cognato, G. P. - Agostinho, P. M. - Hockemeyer, J. - Muller, C. E. - Souza, D. O. - Cunha, R. A.
Journal: J Neurochem
ABSTRACT Seizures early in life cause long term behavioural modifications, namely long term memory deficits in experimental animals. Since caffeine and adenosine A(2A) receptor (A(2A)R) antagonists prevent memory deficits in adult animals, we now investigated if they also prevented the long term memory deficits caused by a convulsive period early in life. Administration of kainate (KA, 2 mg/kg) to 7 days old (P7) rats caused a single period of self-extinguishable convulsions which lead to a poorer memory performance in the Y-maze only when rats were older than 90 days, without modification of locomotion or anxiety-like behaviour in the elevated-plus maze. In accordance with the relation between synapto-toxicity and memory dysfunction, the hippocampus of these adult rats treated with kainate at P7 displayed a lower density of synaptic proteins such as SNAP25 and syntaxin (but not synaptophysin), as well as vesicular glutamate transporters type 1 (but not vesicular GABA transporters), with no changes in PSD95, NMDA receptor subunits (NR1, NR2A, NR2B) or AMPA receptor subunits (GluR1, GluR2) compared to controls. Caffeine (1 g/l) or the A(2A)R antagonist, KW6002 (3 mg/kg) applied in the drinking water from P21 onwards, prevented these memory deficits in P90 rats treated with KA at P7, as well as the accompanying synaptotoxicity. These results show that a single convulsive episode in early life causes a delayed memory deficit in adulthood accompanied by a glutamatergic synaptotoxicity that was prevented by caffeine or adenosine A(2A)R antagonists.
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Authors: Cognato, G. P. - Agostinho, P. M. - Hockemeyer, J. - Muller, C. E. - Souza, D. O. - Cunha, R. A.
Journal: J Neurochem
ABSTRACT Seizures early in life cause long term behavioural modifications, namely long term memory deficits in experimental animals. Since caffeine and adenosine A(2A) receptor (A(2A)R) antagonists prevent memory deficits in adult animals, we now investigated if they also prevented the long term memory deficits caused by a convulsive period early in life. Administration of kainate (KA, 2 mg/kg) to 7 days old (P7) rats caused a single period of self-extinguishable convulsions which lead to a poorer memory performance in the Y-maze only when rats were older than 90 days, without modification of locomotion or anxiety-like behaviour in the elevated-plus maze. In accordance with the relation between synapto-toxicity and memory dysfunction, the hippocampus of these adult rats treated with kainate at P7 displayed a lower density of synaptic proteins such as SNAP25 and syntaxin (but not synaptophysin), as well as vesicular glutamate transporters type 1 (but not vesicular GABA transporters), with no changes in PSD95, NMDA receptor subunits (NR1, NR2A, NR2B) or AMPA receptor subunits (GluR1, GluR2) compared to controls. Caffeine (1 g/l) or the A(2A)R antagonist, KW6002 (3 mg/kg) applied in the drinking water from P21 onwards, prevented these memory deficits in P90 rats treated with KA at P7, as well as the accompanying synaptotoxicity. These results show that a single convulsive episode in early life causes a delayed memory deficit in adulthood accompanied by a glutamatergic synaptotoxicity that was prevented by caffeine or adenosine A(2A)R antagonists.
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Rab3a interacting molecule (RIM) and the tethering of presynaptic transmitter release site-associated CaV2.2 calcium channels.
Publication Date: 2009 Oct 30 PMID: 19878533
Authors: Wong, F. K. - Stanley, E. F.
Journal: J Neurochem
Abstract Biochemical and physiological evidence suggest that presynaptic calcium channels are attached to the transmitter release site within the active zone by a molecular tether. A recent study has proposed that 'Rab3a Interacting Molecule' (RIM) serves as the tether for CaV2.1 channels in mouse brain, based in part on biochemical co-immunoprecipitation (co-IP) using a monoclonal antibody, mRIM. We previously argued against this idea for CaV2.2 calcium channel at chick synapses based on experiments using a different anti-RIM antibody, pRIM1.2: while staining for the two proteins co-localized and co-varied at the transmitter release face, consistent with an association, they failed to co-IP from a synaptosome membrane lysate. RIM is, however, a family of proteins and we tested the possibility that the mRIM antibody used in the more recent study identifies a particular channel-tethering variant. We find that immunostaining with mRIM and CaV2.2 neither co-localized nor co-varied at the transmitter release face and the two proteins did not co-IP, arguing against a common protein complex and a key role CaV2.2 scaffolding at the avian active zone. The differing results might be reconciled, however, in a model where RIM contributes to a distinct scaffold that links the channel to the secretory vesicle docking site.
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Authors: Wong, F. K. - Stanley, E. F.
Journal: J Neurochem
Abstract Biochemical and physiological evidence suggest that presynaptic calcium channels are attached to the transmitter release site within the active zone by a molecular tether. A recent study has proposed that 'Rab3a Interacting Molecule' (RIM) serves as the tether for CaV2.1 channels in mouse brain, based in part on biochemical co-immunoprecipitation (co-IP) using a monoclonal antibody, mRIM. We previously argued against this idea for CaV2.2 calcium channel at chick synapses based on experiments using a different anti-RIM antibody, pRIM1.2: while staining for the two proteins co-localized and co-varied at the transmitter release face, consistent with an association, they failed to co-IP from a synaptosome membrane lysate. RIM is, however, a family of proteins and we tested the possibility that the mRIM antibody used in the more recent study identifies a particular channel-tethering variant. We find that immunostaining with mRIM and CaV2.2 neither co-localized nor co-varied at the transmitter release face and the two proteins did not co-IP, arguing against a common protein complex and a key role CaV2.2 scaffolding at the avian active zone. The differing results might be reconciled, however, in a model where RIM contributes to a distinct scaffold that links the channel to the secretory vesicle docking site.
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In AbetaPP-overexpressing cultured human muscle fibers proteasome inhibition enhances phosphorylation of AbetaPP751 and GSK3beta activation; effects mitigated by lithium and apparently relevant to sporadic inclusion-body myositis.
Publication Date: 2009 Oct 29 PMID: 19878439
Authors: Terracciano, C. - Nogalska, A. - King Engel, W. - Askanas, V.
Journal: J Neurochem
Abstract Muscle fiber degeneration in sporadic inclusion-body myositis (s-IBM) is characterized by accumulation of multiprotein aggregates, including aggregated amyloid-beta-precursor protein 751 (AbetaPP(751)), amyloid-beta (Abeta), phosphorylated tau (p-tau), and other "Alzheimer-characteristic" proteins. Proteasome inhibition is an important component of the s-IBM pathogenesis. In brains of Alzheimer disease (AD) patients and AD transgenic mouse models, phosphorylation of neuronal AbetaPP(695) (p-AbetaPP) on Threonine(668) (T(668)) (equivalent to T(724) of AbetaPP(751)) is considered detrimental because it increases generation of cytotoxic Abeta and induces tau phosphorylation. Activated glycogen synthase kinase3beta (GSK3beta) is involved in phosphorylation of both AbetaPP and tau. Lithium, an inhibitor of GSK3beta, was reported to reduce levels of both the total AbetaPP and p-AbetaPP in AD animal models. In relation to s-IBM, we now show for the first time that: 1. In AbetaPP-overexpressing cultured human muscle fibers (human muscle culture IBM model: a) proteasome inhibition significantly increases GSK3beta activity and AbetaPP phosphorylation; b) treatment with lithium decreases i) phosphorylated-AbetaPP; ii) total amount of AbetaPP, iii) Abeta oligomers, and iv) GSK3beta activity; and c) lithium improves proteasome function. 2. In biopsied s-IBM muscle fibers, GSK3beta is significantly activated and AbetaPP is phosphorylated on Thr(724). Accordingly, treatment with lithium, or other GSK3beta inhibitors, might benefit s-IBM patients.
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Authors: Terracciano, C. - Nogalska, A. - King Engel, W. - Askanas, V.
Journal: J Neurochem
Abstract Muscle fiber degeneration in sporadic inclusion-body myositis (s-IBM) is characterized by accumulation of multiprotein aggregates, including aggregated amyloid-beta-precursor protein 751 (AbetaPP(751)), amyloid-beta (Abeta), phosphorylated tau (p-tau), and other "Alzheimer-characteristic" proteins. Proteasome inhibition is an important component of the s-IBM pathogenesis. In brains of Alzheimer disease (AD) patients and AD transgenic mouse models, phosphorylation of neuronal AbetaPP(695) (p-AbetaPP) on Threonine(668) (T(668)) (equivalent to T(724) of AbetaPP(751)) is considered detrimental because it increases generation of cytotoxic Abeta and induces tau phosphorylation. Activated glycogen synthase kinase3beta (GSK3beta) is involved in phosphorylation of both AbetaPP and tau. Lithium, an inhibitor of GSK3beta, was reported to reduce levels of both the total AbetaPP and p-AbetaPP in AD animal models. In relation to s-IBM, we now show for the first time that: 1. In AbetaPP-overexpressing cultured human muscle fibers (human muscle culture IBM model: a) proteasome inhibition significantly increases GSK3beta activity and AbetaPP phosphorylation; b) treatment with lithium decreases i) phosphorylated-AbetaPP; ii) total amount of AbetaPP, iii) Abeta oligomers, and iv) GSK3beta activity; and c) lithium improves proteasome function. 2. In biopsied s-IBM muscle fibers, GSK3beta is significantly activated and AbetaPP is phosphorylated on Thr(724). Accordingly, treatment with lithium, or other GSK3beta inhibitors, might benefit s-IBM patients.
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Transcriptional Expression of Serotonergic Regulators in Laser-Captured Microdissected Dorsal Raphe Neurons of Subjects with Major Depressive Disorder: Sex-Specific Differences.
Publication Date: 2009 Oct 29 PMID: 19878438
Authors: Goswami, D. B. - May, W. L. - Stockmeier, C. A. - Austin, M. C.
Journal: J Neurochem
Abstract The relationship between serotonin (5-HT) and major depressive disorder (MDD) has been extensively studied but certain aspects are still ambiguous. Given the evidence that 5-HT neurotransmission is reduced in depressed subjects, it is possible that one or more of the 5-HT regulators may be altered in the dorsal raphe nucleus (DR) of depressed subjects. Candidates that regulate 5-HT synthesis and neuronal activity of 5-HT neurons include intrinsic regulators such as tryptophan hydroxylase 2 (TPH2), 5-HT autoreceptors, 5-HT transporter (SERT) and transcription factors, as well as afferent regulators such as estrogen and brain-derived neurotrophic factor (BDNF). The present study was designed to quantify mRNA concentrations of the above 5-HT regulators in an isolated population of 5-HT-containing DR neurons of MDD subjects and gender-matched psychiatrically normal control subjects. We found that mRNA concentrations of the 5-HT1D receptor and the transcription factors, NUDR and REST, were significantly increased in DR-captured neurons of female MDD subjects compared to female control subjects. No significant differences were found for the transcripts in male MDD subjects compared to male controls. This study reveals sex-specific alterations in gene expression of the presynaptic 5-HT1D autoreceptors and 5-HT-related transcription factors, NUDR and REST, in DR neurons of women with MDD.
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Authors: Goswami, D. B. - May, W. L. - Stockmeier, C. A. - Austin, M. C.
Journal: J Neurochem
Abstract The relationship between serotonin (5-HT) and major depressive disorder (MDD) has been extensively studied but certain aspects are still ambiguous. Given the evidence that 5-HT neurotransmission is reduced in depressed subjects, it is possible that one or more of the 5-HT regulators may be altered in the dorsal raphe nucleus (DR) of depressed subjects. Candidates that regulate 5-HT synthesis and neuronal activity of 5-HT neurons include intrinsic regulators such as tryptophan hydroxylase 2 (TPH2), 5-HT autoreceptors, 5-HT transporter (SERT) and transcription factors, as well as afferent regulators such as estrogen and brain-derived neurotrophic factor (BDNF). The present study was designed to quantify mRNA concentrations of the above 5-HT regulators in an isolated population of 5-HT-containing DR neurons of MDD subjects and gender-matched psychiatrically normal control subjects. We found that mRNA concentrations of the 5-HT1D receptor and the transcription factors, NUDR and REST, were significantly increased in DR-captured neurons of female MDD subjects compared to female control subjects. No significant differences were found for the transcripts in male MDD subjects compared to male controls. This study reveals sex-specific alterations in gene expression of the presynaptic 5-HT1D autoreceptors and 5-HT-related transcription factors, NUDR and REST, in DR neurons of women with MDD.
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A Novel mTOR Activating Protein Protects Dopamine Neurons Against Oxidative Stress By Repressing Autophagy Related Cell death.
Publication Date: 2009 Oct 29 PMID: 19878437
Authors: Choi, K. C. - Kim, S. H. - Ha, J. Y. - Kim, S. T. - Son, J. H.
Journal: J Neurochem
Abstract Our previous microarray analysis identified a neuroprotective protein Oxi-alpha, that was downregulated during oxidative stress (OS)-induced cell death in dopamine neurons (Yoo et al. 2004). Here we find that the phylogenetically conserved Oxi-alpha protects against OS by a novel mechanism: activation of the mammalian target of rapamycin (mTOR) kinase and subsequent repression of autophagic vacuole (AV) accumulation and cell death. To the best of our knowledge, Oxi-alpha is the first molecule discovered in dopamine neurons, which activates mTOR kinase. Indeed, the downregulation of Oxi-alpha by OS suppresses the activation of mTOR kinase. The pathogenic effect of downregulated Oxi-alpha was confirmed by gene-specific knockdown experiment, which resulted in not only the repression of mTOR kinase and the subsequent phosphorylation of p70 S6 kinase and 4E-BP1, but also enhanced susceptibility to OS. In accordance with these observations, treatment with rapamycin, an mTOR inhibitor and autophagy inducer, potentiated OS-induced cell death, while similar treatment with an autophagy inhibitor, 3-methyladenine (3-MA) protected the dopamine cells. Our findings present evidence for the presence of a novel class of molecule involved in autophagic cell death triggered by OS in dopamine neurons.
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Authors: Choi, K. C. - Kim, S. H. - Ha, J. Y. - Kim, S. T. - Son, J. H.
Journal: J Neurochem
Abstract Our previous microarray analysis identified a neuroprotective protein Oxi-alpha, that was downregulated during oxidative stress (OS)-induced cell death in dopamine neurons (Yoo et al. 2004). Here we find that the phylogenetically conserved Oxi-alpha protects against OS by a novel mechanism: activation of the mammalian target of rapamycin (mTOR) kinase and subsequent repression of autophagic vacuole (AV) accumulation and cell death. To the best of our knowledge, Oxi-alpha is the first molecule discovered in dopamine neurons, which activates mTOR kinase. Indeed, the downregulation of Oxi-alpha by OS suppresses the activation of mTOR kinase. The pathogenic effect of downregulated Oxi-alpha was confirmed by gene-specific knockdown experiment, which resulted in not only the repression of mTOR kinase and the subsequent phosphorylation of p70 S6 kinase and 4E-BP1, but also enhanced susceptibility to OS. In accordance with these observations, treatment with rapamycin, an mTOR inhibitor and autophagy inducer, potentiated OS-induced cell death, while similar treatment with an autophagy inhibitor, 3-methyladenine (3-MA) protected the dopamine cells. Our findings present evidence for the presence of a novel class of molecule involved in autophagic cell death triggered by OS in dopamine neurons.
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Myelin protein composition is altered in mice lacking either sulfated or both sulfated and non-sulfated galactolipids.
Publication Date: 2009 Oct 29 PMID: 19878436
Authors: Fewou, S. N. - Fernandes, A. - Stockdale, K. - Francone, V. P. - Dupree, J. L. - Rosenbluth, J. - Bansal, R. - Pfeiffer, S. E.
Journal: J Neurochem
Abstract Myelin is highly enriched in galactocerebroside (GalCer) and its sulfated form sulfatide. Mice, unable to synthesize GalCer and sulfatide (CGT(null)) or sulfatide alone (CST(null)), exhibit disorganized paranodal structures and progressive dysmyelination. To obtain insights into the molecular mechanisms underlying these defects, we examined myelin composition of these mutants by 2D-DIGE proteomic approach and immunoblotting. We identified several proteins whose expressions were significantly altered in these mutants. These proteins are known to regulate cytoskeletal dynamics, energy metabolism, vesicular trafficking or adhesion, suggesting a disruption in these physiological processes in the absence of myelin galactolipids. Further analysis of one of these proteins, nucleotide diphosphate kinase/Nm23, showed that it was reduced in myelin of CGT(null) and increased in CST(null), but not in whole brain homogenate. Immunostaining showed an increase in its expression in the cell bodies of CGT(null)- and a decrease in CST(null)-oligodenrocytes, together leading to the hypothesis that transport of NDK/Nm23 from oligodenrocyte cell bodies into myelin may be differentially dysregulated in the absence of these galactolipids. This study provides new insights into the changes that occur in the composition/distribution of myelin proteins in mice lacking either unsulfated and/or sulfated galactolipids and reinforces the role of these lipids in intracellular trafficking.
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Authors: Fewou, S. N. - Fernandes, A. - Stockdale, K. - Francone, V. P. - Dupree, J. L. - Rosenbluth, J. - Bansal, R. - Pfeiffer, S. E.
Journal: J Neurochem
Abstract Myelin is highly enriched in galactocerebroside (GalCer) and its sulfated form sulfatide. Mice, unable to synthesize GalCer and sulfatide (CGT(null)) or sulfatide alone (CST(null)), exhibit disorganized paranodal structures and progressive dysmyelination. To obtain insights into the molecular mechanisms underlying these defects, we examined myelin composition of these mutants by 2D-DIGE proteomic approach and immunoblotting. We identified several proteins whose expressions were significantly altered in these mutants. These proteins are known to regulate cytoskeletal dynamics, energy metabolism, vesicular trafficking or adhesion, suggesting a disruption in these physiological processes in the absence of myelin galactolipids. Further analysis of one of these proteins, nucleotide diphosphate kinase/Nm23, showed that it was reduced in myelin of CGT(null) and increased in CST(null), but not in whole brain homogenate. Immunostaining showed an increase in its expression in the cell bodies of CGT(null)- and a decrease in CST(null)-oligodenrocytes, together leading to the hypothesis that transport of NDK/Nm23 from oligodenrocyte cell bodies into myelin may be differentially dysregulated in the absence of these galactolipids. This study provides new insights into the changes that occur in the composition/distribution of myelin proteins in mice lacking either unsulfated and/or sulfated galactolipids and reinforces the role of these lipids in intracellular trafficking.
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AP-1 inhibitory peptides are neuroprotective following acute glutamate excitotoxicity in primary cortical neuronal cultures.
Publication Date: 2009 Oct 28 PMID: 19878434
Authors: Meade, A. J. - Meloni, B. P. - Cross, J. - Bakker, A. J. - Fear, M. W. - Mastaglia, F. L. - Watt, P. M. - Knuckey, N. W.
Journal: J Neurochem
Abstract Neuronal cell death caused by glutamate excitotoxicity is prevalent in various neurological disorders and has been associated with the transcriptional activation of activator protein-1 (AP-1). In this study, we tested 19 recently isolated AP-1 inhibitory peptides, fused to the cell penetrating peptide TAT, for their efficacy in preventing cell death in cortical neuronal cultures following glutamate excitotoxicity. Five peptides (PYC19D-TAT, PYC35D-TAT, PYC36D-TAT, PYC38D-TAT, PYC41D-TAT) displayed neuroprotective activity in concentration responses in both L- and retro-inverso D-isoforms with increasing levels of neuroprotection peaking at 83%. Interestingly, the D-TAT peptide displayed a neuroprotective effect increasing neuronal survival to 25%. Using an AP-1 luciferase reporter assay we confirmed that the AP-1 inhibitory peptides reduce AP-1 transcriptional activation, and that c-Jun and c-Fos mRNA following glutamate exposure is reduced. In addition, following glutamate exposure the AP-1 inhibitory peptides decreased calpain mediated alpha-fodrin cleavage, but not neuronal calcium influx. Finally, as neuronal death following glutamate excitotoxicity was transcriptionally independent (actinomycin D insensitive), our data indicate that activation of AP-1 proteins can induce cell death via non-transcriptional pathways. Thus, these peptides have potential application as therapeutics directly or for the rational design of small molecule inhibitors in both apoptotic and necrotic neuronal death associated with AP-1 activation.
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Authors: Meade, A. J. - Meloni, B. P. - Cross, J. - Bakker, A. J. - Fear, M. W. - Mastaglia, F. L. - Watt, P. M. - Knuckey, N. W.
Journal: J Neurochem
Abstract Neuronal cell death caused by glutamate excitotoxicity is prevalent in various neurological disorders and has been associated with the transcriptional activation of activator protein-1 (AP-1). In this study, we tested 19 recently isolated AP-1 inhibitory peptides, fused to the cell penetrating peptide TAT, for their efficacy in preventing cell death in cortical neuronal cultures following glutamate excitotoxicity. Five peptides (PYC19D-TAT, PYC35D-TAT, PYC36D-TAT, PYC38D-TAT, PYC41D-TAT) displayed neuroprotective activity in concentration responses in both L- and retro-inverso D-isoforms with increasing levels of neuroprotection peaking at 83%. Interestingly, the D-TAT peptide displayed a neuroprotective effect increasing neuronal survival to 25%. Using an AP-1 luciferase reporter assay we confirmed that the AP-1 inhibitory peptides reduce AP-1 transcriptional activation, and that c-Jun and c-Fos mRNA following glutamate exposure is reduced. In addition, following glutamate exposure the AP-1 inhibitory peptides decreased calpain mediated alpha-fodrin cleavage, but not neuronal calcium influx. Finally, as neuronal death following glutamate excitotoxicity was transcriptionally independent (actinomycin D insensitive), our data indicate that activation of AP-1 proteins can induce cell death via non-transcriptional pathways. Thus, these peptides have potential application as therapeutics directly or for the rational design of small molecule inhibitors in both apoptotic and necrotic neuronal death associated with AP-1 activation.
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A POINT MUTATION IN THE ECTODOMAIN-TRANSMEMBRANE 2 INTERFACE ELIMINATES THE INHIBITORY EFFECTS OF ETHANOL IN P2X4 RECEPTORS.
Publication Date: 2009 Oct 28 PMID: 19878433
Authors: Popova, M. - Asatryan, L. - Ostrovskaya, O. - Wyatt, L. R. - Li, K. - Alkana, R. L. - Davies, D. L.
Journal: J Neurochem
ABSTRACT ATP-gated P2X4 receptors (P2X4R) are abundantly expressed in the CNS. However, little is known about the molecular targets for ethanol action in P2X4Rs. The current investigation tested the hypothesis that the ectodomain-TM interface contains residues that are important for the action of ethanol in P2X4Rs. Wildtype (WT) and mutant P2X4R were expressed in Xenopus oocytes. ATP concentration-response curves and ethanol (10-200 mM)-induced changes in ATP EC(10)-gated currents were determined using two-electrode voltage clamp (-70 mV). Alanine substitution at the ectodomain-TM1 interface (positions 50-61) resulted in minimal changes in ethanol response. On the other hand, alanine substitution at the ectodomain-TM2 interface (positions 321-337) identified two key residues (D331 and M336) that the alanine mutation significantly reduced ethanol inhibition of ATP-gated currents without causing marked changes in ATP I(max), EC(50) or Hill slope. Other amino acid substitutions at positions 331 and 336 significantly altered or eliminated the modulatory effects of ethanol. Linear regression analyses revealed a significant relationship between hydropathy and polarity, but not molecular volume/molecular weight of the residues at these two positions. The results support the proposed hypothesis and represent an important step towards developing ethanol-insensitive receptors for investigating the role of P2X4Rs in mediating behavioral effects of ethanol.
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Authors: Popova, M. - Asatryan, L. - Ostrovskaya, O. - Wyatt, L. R. - Li, K. - Alkana, R. L. - Davies, D. L.
Journal: J Neurochem
ABSTRACT ATP-gated P2X4 receptors (P2X4R) are abundantly expressed in the CNS. However, little is known about the molecular targets for ethanol action in P2X4Rs. The current investigation tested the hypothesis that the ectodomain-TM interface contains residues that are important for the action of ethanol in P2X4Rs. Wildtype (WT) and mutant P2X4R were expressed in Xenopus oocytes. ATP concentration-response curves and ethanol (10-200 mM)-induced changes in ATP EC(10)-gated currents were determined using two-electrode voltage clamp (-70 mV). Alanine substitution at the ectodomain-TM1 interface (positions 50-61) resulted in minimal changes in ethanol response. On the other hand, alanine substitution at the ectodomain-TM2 interface (positions 321-337) identified two key residues (D331 and M336) that the alanine mutation significantly reduced ethanol inhibition of ATP-gated currents without causing marked changes in ATP I(max), EC(50) or Hill slope. Other amino acid substitutions at positions 331 and 336 significantly altered or eliminated the modulatory effects of ethanol. Linear regression analyses revealed a significant relationship between hydropathy and polarity, but not molecular volume/molecular weight of the residues at these two positions. The results support the proposed hypothesis and represent an important step towards developing ethanol-insensitive receptors for investigating the role of P2X4Rs in mediating behavioral effects of ethanol.
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Insulin/PI3K signaling protects dentate neurons from oxygen-glucose deprivation in organotypic slice cultures.
Publication Date: 2009 Oct 26 PMID: 19860861
Authors: Sun, X. - Yao, H. - Douglas, R. M. - Gu, X. Q. - Wang, J. - Haddad, G. G.
Journal: J Neurochem
It is known that ischemia/reperfusion induces neurodegeneration in the hippocampus in a sub-region dependent manner. The present study investigated the mechanism of selective resistance/vulnerability to oxygen glucose deprivation (OGD) using mouse organotypic hippocampal cultures. Analysis of propidium iodide uptake showed that OGD induced duration- and sub-region-dependent neuronal injury. As compared to the CA1-3 sub-regions, dentate neuronal survival was more sensitive to inhibition of PI3K/Akt signaling under basal conditions. Dentate neuronal sensitivity to PI3K/Akt signaling activation was inversely related to its vulnerability to OGD-induced injury; Insulin/IGF pretreatment conferred neuroprotection to dentate neurons via activation of PI3K/Akt signaling. In contrast, CA1 and CA3 neurons were less sensitive to disruptions of endogenous PI3K/Akt signaling and protective effects of insulin/IGF-1, but more vulnerable to OGD. OGD-induced injury in CA1 was reduced by inhibition of NMDA receptor or MAPK signaling, and was prevented by blocking NMDA receptor in the presence of insulin. The CA2 sub-region was distinctive in its response to glutamate, OGD, and insulin, compared to other CA sub-regions. CA2 neurons were sensitive to the protective effects of insulin against OGD-induced injury, but more resistant to glutamate. Distinctive distribution of insulin receptor beta and basal phospho-Akt was detected in our slice cultures. Our results suggest a role for insulin signaling in sub-regional resistance/vulnerability to cerebral ischemia.
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Authors: Sun, X. - Yao, H. - Douglas, R. M. - Gu, X. Q. - Wang, J. - Haddad, G. G.
Journal: J Neurochem
It is known that ischemia/reperfusion induces neurodegeneration in the hippocampus in a sub-region dependent manner. The present study investigated the mechanism of selective resistance/vulnerability to oxygen glucose deprivation (OGD) using mouse organotypic hippocampal cultures. Analysis of propidium iodide uptake showed that OGD induced duration- and sub-region-dependent neuronal injury. As compared to the CA1-3 sub-regions, dentate neuronal survival was more sensitive to inhibition of PI3K/Akt signaling under basal conditions. Dentate neuronal sensitivity to PI3K/Akt signaling activation was inversely related to its vulnerability to OGD-induced injury; Insulin/IGF pretreatment conferred neuroprotection to dentate neurons via activation of PI3K/Akt signaling. In contrast, CA1 and CA3 neurons were less sensitive to disruptions of endogenous PI3K/Akt signaling and protective effects of insulin/IGF-1, but more vulnerable to OGD. OGD-induced injury in CA1 was reduced by inhibition of NMDA receptor or MAPK signaling, and was prevented by blocking NMDA receptor in the presence of insulin. The CA2 sub-region was distinctive in its response to glutamate, OGD, and insulin, compared to other CA sub-regions. CA2 neurons were sensitive to the protective effects of insulin against OGD-induced injury, but more resistant to glutamate. Distinctive distribution of insulin receptor beta and basal phospho-Akt was detected in our slice cultures. Our results suggest a role for insulin signaling in sub-regional resistance/vulnerability to cerebral ischemia.
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From Wikipedia,
Neurochemistry is the specific study of neurochemicals, which include neurotransmitters and other molecules such as neuro-active drugs that influence neuron function. This principle closely examines the manner in which these neurochemicals influence the network of neural operation. This evolving area of neuroscience offers a neurochemist a micro-macro connection between the analysis of organic compounds active in the nervous system and neural processes such as cortical plasticity, neurogenesis and neural differentiation.
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