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Omar S.I.,University of Manitoba | Albensi B.C.,University of Manitoba | Albensi B.C.,St Boniface Hospital Research | Gough K.M.,University of Manitoba
Current Alzheimer Research | Year: 2016

Calcium homeostasis is an essential physiological process requiring tight control in the normal cell. The dysregulation of calcium homeostasis may play a key role in the onset of Alzheimer’s disease (AD) and other disorders, whether through the loss of calcium binding or calcium sensing capacity. Calbindin D28k(CB-D28k), a calcium binding protein composed of six EF-hands, four of which can bind Ca2+, has been implicated in AD-related calcium dysregulation. In this study, docking and molecular dynamics calculations were employed to refine the protein data base model in order to understand the underlying structural variations between functional and non-functional EF-hands. Molecular modeling calculations improved the modelled protein structure: helix-loop-helix sequences were formed in all hands and most canonical interactions were formed in the four functional hands. The protein can also bind Zn2+, potentially altering the Ca2+ binding capability. Analysis of calculated structures of Zn2+ bound protein showed that only half of the correct EF-hand canonical interactions of Ca2+ were formed with loop residues. These results have important implications for the understanding of calcium dysregulation as well as for the development of novel therapeutic strategies in AD and other central nervous system disease processes, or in conditions of brain injury where calcium homeostasis is compromised. © 2016 Bentham Science Publishers. Source

Oikawa K.,St Boniface Hospital Research | Odero G.L.,St Boniface Hospital Research | Nafez S.,St Boniface Hospital Research | Nafez S.,University of Manitoba | And 8 more authors.
Cell Biochemistry and Biophysics | Year: 2016

Visinin-like proteins (VILIPs) belong to the calcium sensor protein family. VILIP-1 has been examined as a cerebrospinal fluid biomarker and as a potential indicator for cognitive decline in Alzheimer’s disease (AD). However, little is known about VILIP-3 protein biochemistry. We performed co-immunoprecipitation experiments to examine whether VILIP-3 can interact with reduced nicotine adenine dinucleotide (NADH)-cytochrome b5 reductase. We also evaluated the specificity of cytochrome b5 within the visinin-like protein subfamily and identified cytochrome P450 isoforms in the brain. In this study, we show that cytochrome b5 has an affinity for hippocalcin, neurocalcin-δ, and VILIP-3, but not visinin-like protein-1. VILIP-3 was also shown to interact with NADH-cytochrome b5 reductase in a Ca2+-dependent manner. These results suggest that VILIP-3, hippocalcin, and neurocalcin-δ provide a Ca2+-dependent modulation to the NADH-dependent microsomal electron transport. The results also suggest that future therapeutic strategies that target calcium-signaling pathways and VILIPs may be of value. © 2016 Springer Science+Business Media New York Source

Snow W.M.,St Boniface Hospital Research | Snow W.M.,University of Manitoba | Pahlavan P.S.,St Boniface Hospital Research | Pahlavan P.S.,University of Manitoba | And 9 more authors.
Frontiers in Molecular Neuroscience | Year: 2015

Research has identified several transcription factors that regulate activity-dependent plasticity and memory, with cAMP-response element binding protein (CREB) being the most well-studied. In neurons, CREB activation is influenced by the transcription factor nuclear factor kappa B (NF-κB), considered central to immunity but more recently implicated in memory. The transcription factor early growth response-2 (Egr-2), an NF-κB gene target, is also associated with learning and memory. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2), an antioxidant transcription factor linked to NF-κB in pathological conditions, has not been studied in normal memory. Given that numerous transcription factors implicated in activity-dependent plasticity demonstrate connections to NF-κB, this study simultaneously evaluated protein levels of NF-κB, CREB, Egr-2, Nrf2, and actin in hippocampi from young (1 month-old) weanling CD1 mice after training in the Morris water maze, a hippocampal-dependent spatial memory task. After a 6-day acquisition period, time to locate the hidden platform decreased in the Morris water maze. Mice spent more time in the target vs. non-target quadrants of the maze, suggestive of recall of the platform location. Western blot data revealed a decrease in NF-κB p50 protein after training relative to controls, whereas NF-κB p65, Nrf2 and actin increased. Nrf2 levels were correlated with platform crosses in nearly all tested animals. These data demonstrate that training in a spatial memory task results in alterations in and associations with particular transcription factors in the hippocampus, including upregulation of NF-κB p65 and Nrf2. Training-induced increases in actin protein levels caution against its use as a loading control in immunoblot studies examining activity-dependent plasticity, learning, and memory. © 2015 Snow, Pahlavan, Djordjevic, McAllister, Platt, Alashmali, Bernstein, Suh and Albensi. Source

Lemaistre J.L.,University of Manitoba | Lemaistre J.L.,St Boniface Hospital Research | Sanders S.A.,University of Manitoba | Sanders S.A.,St Boniface Hospital Research | And 8 more authors.
Journal of Cerebral Blood Flow and Metabolism | Year: 2012

N-methyl-D-aspartate (NMDA) receptors are glutamate-gated cation channels that mediate excitatory neurotransmission in the central nervous system. In addition to glutamate, NMDA receptors are also activated by coagonist binding of the gliotransmitter, D-serine. Neuronal NMDA receptors mediate activity-dependent blood flow regulation in the brain. Our objective was to determine whether NMDA receptors expressed by brain endothelial cells can induce vasodilation of isolated brain arteries. Adult mouse middle cerebral arteries (MCAs) were isolated, pressurized, and preconstricted with norepinephrine. N-methyl-D-aspartate receptor agonists, glutamate and NMDA, significantly dilated MCAs in a concentration-dependent manner in the presence of D-serine but not alone. Dilation was significantly inhibited by NMDA receptor antagonists, D-2-amino-5-phosphonopentanoate and 5,7-dichlorokynurenic acid, indicating a response dependent on NMDA receptor glutamate and D-serine binding sites, respectively. Vasodilation was inhibited by denuding the endothelium and by selective inhibition or genetic knockout of endothelial nitric oxide synthase (eNOS). We also found evidence for expression of the pan-NMDA receptor subunit, NR1, in mouse primary brain endothelial cells, and for the NMDA receptor subunit NR2C in cortical arteries in situ. Overall, we conclude that NMDA receptor coactivation by glutamate and D-serine increases lumen diameter in pressurized MCA in an endothelial and eNOS-dependent mechanism. © 2012 ISCBFM All rights reserved. Source

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