bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of the role of the retinal G protein‐coupled receptor (RGR) in the vertebrate retina in vivo
Authors: Maeda Tadao , Van Hooser J. Preston , Driessen Carola A. G. G. , Filipek Sławomir , Janssen Jacques J. M. , Palczewski Krzysztof 
Published: July 2010

AbstractThe retinal G protein‐coupled receptor (RGR) is a protein that structurally resembles visual pigments and other G protein‐coupled receptors. RGR may play a role as a photoisomerase in the production of 11‐cis‐retinal, the chromophore of the visual pigments. As the proposed function of RGR, in a complex with 11‐cis‐retinol dehydrogenase (RDH5), is to regenerate 11‐cis‐retinal under light conditions and RDH5 is expected to function in the light‐independent part of the retinoid cycle, we speculated that the simultaneous loss of function of both proteins should more severely affect the rhodopsin regeneration capacity. Here, we evaluated the role of RGR using rgr–/– single and rdh5–/–rgr–/– double knockout mice under a number of light conditions. The most striking phenotype of rgr–/– mice after a single flash of light includes light‐dependent formation of 9‐cis‐ and 13‐cis‐retinoid isomers. These isomers are not formed in wild‐type mice because either all‐trans‐retinal is bound to RGR and protected from isomerization to 9‐cis‐ or 13‐cis‐retinal or because RGR is able to eliminate these isomers directly or indirectly. After intense bleaching, a transient accumulation of all‐trans‐retinyl esters and an attenuated recovery of 11‐cis‐retinal were observed. Finally, even under conditions of prolonged light illumination, as investigated in vitro in biochemical assays or in vivo by electroretinogram (ERG) measurements, no evidence of catalytic‐like photoisomerization‐driven production of 11‐cis‐retinal could be attained. These and previous results suggest that RGR and RDH5 are likely to function in the retinoid cycle, although their role is not essential and regeneration of visual pigment is only mildly affected by the absence of both proteins in rod‐dominated mice.
Co‐ordinate transcriptional regulation of dopamine synthesis genes by α‐synuclein in human neuroblastoma cell lines
Authors: Baptista Melisa J. , O'Farrell Casey , Daya Sneha , Ahmad Rili , Miller David W. , Hardy John , Farrer Matthew J. , Cookson Mark R. 
Published: July 2010

AbstractAbnormal accumulation of α‐synuclein in Lewy bodies is a neuropathological hallmark of both sporadic and familial Parkinson's disease (PD). Although mutations in α‐synuclein have been identified in autosomal dominant PD, the mechanism by which dopaminergic cell death occurs remains unknown. We investigated transcriptional changes in neuroblastoma cell lines transfected with either normal or mutant (A30P or A53T) α‐synuclein using microarrays, with confirmation of selected genes by quantitative RT‐PCR. Gene products whose expression was found to be significantly altered included members of diverse functional groups such as stress response, transcription regulators, apoptosis‐inducing molecules, transcription factors and membrane‐bound proteins. We also found evidence of altered expression of dihydropteridine reductase, which indirectly regulates the synthesis of dopamine. Because of the importance of dopamine in PD, we investigated the expression of all the known genes in dopamine synthesis. We found co‐ordinated downregulation of mRNA for GTP cyclohydrolase, sepiapterin reductase (SR), tyrosine hydroxylase (TH) and aromatic acid decarboxylase by wild‐type but not mutant α‐synuclein. These were confirmed at the protein level for SR and TH. Reduced expression of the orphan nuclear receptor Nurr1 was also noted, suggesting that the co‐ordinate regulation of dopamine synthesis is regulated through this transcription factor.
Levodopa treatment reverses endocannabinoid system abnormalities in experimental parkinsonism
Authors: Maccarrone Mauro , Gubellini Paolo , Bari Monica , Picconi Barbara , Battista Natalia , Centonze Diego , Bernardi Giorgio , Finazzi‐Agrò Alessandro , Calabresi Paolo 
Published: July 2010

AbstractCannabinoid receptors and their endogenous ligands are potent inhibitors of neurotransmitter release in the brain. Here, we show that in a rat model of Parkinson's disease induced by unilateral nigral lesion with 6‐hydroxydopamine (6‐OHDA), the striatal levels of the endocannabinoid anandamide (AEA) were increased, while the activity of its membrane transporter and hydrolase (fatty‐acid amide hydrolase, FAAH) were decreased. These changes were not observed in the cerebellum of the same animals. Moreover, the frequency and amplitude of glutamate‐mediated spontaneous excitatory post‐synaptic currents were augmented in striatal spiny neurones recorded from parkinsonian rats. Remarkably, the anomalies in the endocannabinoid system, as well as those in glutamatergic activity, were completely reversed by chronic treatment of parkinsonian rats with levodopa, and the pharmacological inhibition of FAAH restored a normal glutamatergic activity in 6‐OHDA‐lesioned animals. Thus, the increased striatal levels of AEA may reflect a compensatory mechanism trying to counteract the abnormal corticostriatal glutamatergic drive in parkinsonian rats. However, this mechanism seems to be unsuccessful, since spontaneous excitatory activity is still higher in these animals. Taken together, these data show that anomalies in the endocannabinoid system induced by experimental parkinsonism are restricted to the striatum and can be reversed by chronic levodopa treatment, and suggest that inhibition of FAAH might represent a possible target to decrease the abnormal cortical glutamatergic drive in Parkinson's disease.
Oligodendrocyte myelin glycoprotein growth inhibition function requires its conserved leucine‐rich repeat domain, not its glycosylphosphatidyl‐inositol anchor
Authors: Vourc'h Patrick , Moreau Thierry , Arbion Flavie , Marouillat‐Védrine Sylviane , Müh Jean‐Pierre , Andres Christian 
Published: July 2010

AbstractThe oligodendrocyte myelin glycoprotein (OMgp) inhibits neurite outgrowth and axonal regeneration after brain injury, but its normal function remains unknown. Several observations suggest its implication in cell growth regulation. Here we report an analysis of the domain requirement in OMgp proliferation inhibitory function. We first studied the OMgp protein sequence in 14 mammal species and observed a high conservation of its leucine‐rich repeat (LRR) domain. The deletion of this LRR domain is responsible for a total loss of function in an in vitro expression system. The possible three‐dimensional structure of the LRR domain of OMgp was modelled using the structure of Yersinia pestis YopM cytotoxin as a template. The predicted arrangement of the LRR segments is compatible with a function of OMgp as a binding protein. The OMgp is a glycosylphosphatidyl‐inositol‐linked protein anchored in the plasma membrane of oligodendrocytes and neurones. Using deletion mutagenesis, we demonstrated the dispensability of the glycosylphosphatidyl‐inositol anchor for OMgp proliferation inhibition function. Our results suggest that OMgp is part of a receptor complex, either as a coreceptor or as a membrane‐bound or soluble ligand, involved in the transmission of a growth suppressive signal.
The synergistic effects of NGF and IGF‐1 on neurite growth in adult sensory neurons: convergence on the PI 3‐kinase signaling pathway
Authors: Jones David M. , Tucker Budd A. , Rahimtula Masuma , Mearow Karen M. 
Published: July 2010

AbstractNerve growth factor (NGF) and insulin‐like growth factor‐1 (IGF‐1) play an important role in promoting axonal growth from dorsal root ganglion (DRG) neurons. Adult DRG neurons exhibit neurotrophin‐independent survival, providing an excellent system with which to study trophic factor effects on neurite growth in the absence of significant survival effects. Using young adult rat DRG neurons we have demonstrated a synergistic effect of NGF plus IGF (N + I), compared with either factor alone, in promoting neurite growth. Not only does the presence of NGF and IGF‐1 enhance neurite initiation, it also significantly augments the extent of neurite branching and elongation. We have also examined potential mechanism(s) underlying this synergistic effect. Immunoblotting experiments of classical growth factor intermediary signalling pathways (PI 3‐K‐Akt‐GSK‐3 and Ras‐Raf‐MAPK) were performed using phospho‐specific antibodies to assess activation state. We found that activation of Akt and MAPK correlated with neurite elongation and branching. However, using pharmacological inhibitors, we observed that a PI 3‐K pathway involving both Akt and GSK‐3 appeared to be more important for neurite extension and branching than MAPK‐dependent signalling. In fact, inhibition of activation of MAPK with U0126 resulted in increased neuritic branching, possibly as a result of the concomitant increase observed in phospho‐Akt. Furthermore, inhibition of GSK3 (which is negatively regulated by phosphorylation on S9/S21) also resulted in increased growth. Our data point to signalling convergence upon the PI 3‐K‐Akt‐GSK‐3 pathway that underlies the NGF plus IGF synergism. In addition, to our knowledge, this is the first report in primary neurons that inhibition of GSK3 results in an enhanced neurite growth.
Activity of the rat GluR4 promoter in transfected cortical neurons and glia
Authors: Borges Karin , Myers Scott J. , Zhang Sunan , Dingledine Raymond 
Published: July 2010

AbstractAMPA (alpha‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate) receptors are assembled from four subunits, GluR1‐4. Although GluR4 is widely expressed in brain its abundance is less than GluR1‐3. We have isolated ∼5 kb of the rat GluR4 promoter region and analyzed its capacity to drive expression of a luciferase reporter gene in transfected rat cortical neurons and glia, and C6 glioma cells. Multiple transcriptional start sites were identified in a GC‐rich region lacking TATA‐boxes between − 1090 and − 1011 bp from ATG. In transfected mixed cortical cultures, luciferase expression driven by GluR4 promoter segments were found predominantly in TuJ1‐positive neurons, indicating neuronal preference of GluR4. The GluR4 promoter fragments were 6–12‐fold more active in neurons than glia, compared with a 30‐fold neuronal selectivity of GluR2. Deletion of the GluR4 transcriptional initiation region decreased luciferase activity in neurons, but increased activity in C6 cells, suggesting that regulatory elements governing neuronal expression reside in this region. An intron within the 5′‐untranslated region and Sp1, IK2 and E‐box sites are conserved in the rat, mouse and human GluR4 promoters. The relative activity of GluR4 and GluR2 promoters in transfected cells correlates with their expression in brain, and in both promoters regulatory elements for neuronal expression reside near the initiation sites.
Cellular distribution and bioactivity of the key steroidogenic enzyme, cytochrome P450side chain cleavage, in sensory neural pathways
Authors: Patte‐Mensah Christine , Kappes Vincent , Freund‐Mercier Marie‐José , Tsutsui Kazuyoshi , Mensah‐Nyagan Ayikoe G. 
Published: July 2010

AbstractNeurosteroids are steroids produced within the nervous system. Based on behavioural responses evoked in animals by synthetic steroid injections, several studies suggested neurosteroid involvement in important neurophysiological processes. These observations should be correlated only to neuroactive effects of the injected steroids. Neurosteroids mostly control the CNS activity through allosteric modulation of neurotransmitter receptors within concentration ranges used by neurotransmitters themselves. Therefore, neurosteroid production within pathways controlling a neurophysiological process is necessary to consider neurosteroid involvement in that process. Because of the increasing speculation about pain modulation by neurosteroids based on pharmacological observations, we decided to clarify the situation by investigating neurosteroidogenesis occurrence in sensory pathways, particularly in nociceptive structures. We studied the presence and activity of cytochrome P450side chain cleavage (P450scc) in rat pain pathways. P450scc‐immunoreactive cells were localized in dorsal root ganglia (DRG), spinal cord (SC) dorsal horn, nociceptive supraspinal nuclei (SSN) and somatosensory cortex. Incubation of DRG, SSN or SC tissue homogenates with [3H]cholesterol yielded the formation of radioactive metabolites including [3H]pregnenolone of which the synthesis was reduced in presence of aminogluthetimide, a P450scc inhibitor. These first neuroanatomical and neurochemical results demonstrate the occurrence of neurosteroidogenesis in nociceptive pathways and strongly suggest that neurosteroids may control pain mechanisms.
Glucocorticoid‐regulated human serotonin transporter (5‐HTT) expression is modulated by the 5‐HTT gene‐promotor‐linked polymorphic region
Authors: Glatz K. , Mössner R. , Heils A. , Lesch K. P. 
Published: July 2010

AbstractMood, emotion and cognition are modulated by serotonergic neurotransmission, while the physiological function of serotonergic synapses depends on serotonin reuptake, which is mediated by the serotonin transporter (5‐HTT). Allelic variation of 5‐HTT expression in humans is caused by a functional gene‐promoter polymorphism with two predominant variant alleles, which are associated with variations in anxiety measures as previously reported. Here we report that administration of dexamethasone, a potent glucocorticosteroid hormone, results in an increase in 5‐HTT expression in immortalized human B‐lymphoblastoid cells, which express the human 5‐HTT. Functional reporter gene assays as well as 5‐HT uptake and inhibitor binding measures revealed a genotype‐dependent dose–response to glucocorticosteroid administration, which was antagonized by RU 38486, a non‐specific glucocorticosteroid hormone antagonist. The allele‐specific differences after administration of dexamethasone depended on the repetitive GC‐rich sequence located approximately 1.4 kb upstream of the 5‐HTT gene transcription site because of absence of a significant steroid effect after transfecting a deletional mutant reporter gene construct, which lacks this repetitive promoter sequence. Our findings may contribute to explain the vulnerability to stress‐related disorders in susceptible individuals, in whom further clinical studies should follow up on these in vitro findings.
Overactivation of glycogen synthase kinase‐3 by inhibition of phosphoinositol‐3 kinase and protein kinase C leads to hyperphosphorylation of tau and impairment of spatial memory
Authors: Liu Shi Jie , Zhang Ai Hong , Li Hong Lian , Wang Qun , Deng Heng Mei , Netzer William J. , Xu Huaxi , Wang Jian Zhi 
Published: July 2010

AbstractNeurofibrillary tangles (NFTs) consisting of the hyperphosphorylated microtubule‐associated protein tau are a defining pathological characteristic of Alzheimer's disease (AD). Hyperphosphorylation of tau is hypothesized to impair the microtubule stabilizing function of tau, leading to the formation of paired helical filaments and neuronal death. Glycogen synthase kinase‐3 (GSK‐3) has been shown to be one of several kinases that mediate tau hyperphosphorylation in vitro. However, molecular mechanisms underlying overactivation of GSK‐3 and its potential linkage to AD‐like pathologies in vivo remain unclear. Here, we demonstrate that injection of wortmannin (a specific inhibitor of phosphoinositol‐3 kinase) or GF‐109203X (a specific inhibitor of protein kinase C) into the left ventricle of rat brains leads to overactivation of GSK‐3, hyperphosphorylation of tau at Ser 396/404/199/202 and, most significantly, impaired spatial memory. The effects of wortmannin and GF‐109203X are additive. Significantly, specific inhibition of GSK‐3 activity by LiCl prevents hyperphosphorylation of tau, and spatial memory impairment resulting from PI3K and PKC inhibition. These results indicate that in vivo inhibition of phosphoinositol‐3 kinase and protein kinase C results in overactivation of GSK‐3 and tau hyperphosphorylation and support a direct role of GSK‐3 in the formation of AD‐like cognitive deficits.
Molecular cloning, characterization and brain mapping of the melanocortin 5 receptor in the goldfish
Authors: Cerdá‐Reverter José Miguel , Ling Maria Kristina , Schiöth Helgi Birgir , Peter Richard Ector 
Published: July 2010

AbstractThe melanocortin 5 receptor (MC5R) is activated by melanocyte‐stimulating hormones (MSHs) and has a widespread tissue distribution, while its detailed central expression pattern and brain functions are fairly unknown. We report cloning, pharmacological characterization, tissue distribution and detailed brain mapping of melanocortin 5 receptor in goldfish (gMC5R). The goldfish orthologue protein is 69% identical to human MC5R and is conserved in important functional domains. The gMC5R showed similar potency to α‐, β‐ and γ‐MSH peptides in radioligand binding as the mammalian orthologues, while MTII and HS024 were both agonists at this receptor. The gMC5R‐mRNA was found in the peripheral tissues including kidney, spleen, skin and retina, with low expression levels in the intestine, fat, muscle, gill, pituitary and ovary. In situ hybridization studies demonstrated that gMC5R transcripts are widely distributed in the goldfish brain. The gMC5R expression was found in ventral telencephalon, pre‐optic area, dorsal and ventral thalamus, infundibular hypothalamus, posterior tuberculum, tectum and tegmentum mesencephali, reticular formation, vagal and facial lobes and spinal cord. The cloning and characterization of this receptor provides an important tool to elucidate its participation in neuroendocrine and behavioural control.
The expression of brain cyclooxygenase‐2 is down‐regulated in the cytosolic phospholipase A2 knockout mouse
Authors: Bosetti Francesca , Weerasinghe Gayani R. 
Published: July 2010

AbstractWe examined brain phospholipase A2 (PLA2) activity and the expression of enzymes metabolizing arachidonic acid (AA) in cytosolic PLA2 knockout () mice to see if other brain PLA2 can compensate for the absence of cPLA2 alpha and if cPLA2 couples with specific downstream enzymes in the eicosanoid biosynthetic pathway. We found that the rate of formation of prostaglandin E2 (PGE2), an index of net cyclooxygenase (COX) activity, was decreased by 62% in the compared with the control mouse brain. The decrease was accompanied by a 50–60% decrease in mRNA and protein levels of COX‐2, but no change in these levels in COX‐1 or in PGE synthase. Brain 5‐lipoxygenase (5‐LO) and cytochrome P450 epoxygenase (cyp2C11) protein levels were also unaltered. Total and Ca2+‐dependent PLA2 activities did not differ significantly between and control mice, and protein levels of type VI iPLA2 and type V sPLA2, normalized to actin, were unchanged. These results show that type V sPLA2 and type VI iPLA2 do not compensate for the loss of brain cPLA2 alpha, and that this loss has significant downstream effects on COX‐2 expression and PGE2 formation, sparing other AA oxidative enzymes. This suggests that cPLA2 is critical for COX‐2‐derived eicosanoid production in mouse brain.
Long‐term alterations in glutamate receptor and transporter expression following early‐life seizures are associated with increased seizure susceptibility
Authors: Zhang Guojun , Raol Yogendra Sinh H. , Hsu Fu‐Chun , Brooks‐Kayal Amy R. 
Published: July 2010

AbstractProlonged seizures in early childhood are associated with an increased risk of development of epilepsy in later life. The mechanism(s) behind this susceptibility to later development of epilepsy is unclear. Increased synaptic activity during development has been shown to permanently alter excitatory neurotransmission and could be one of the mechanisms involved in this increased susceptibility to the development of epilepsy. In the present study we determine the effect of status‐epilepticus induced by lithium/pilocarpine at postnatal day 10 (P10 SE) on the expression of glutamate receptor and transporter mRNAs in hippocampal dentate granule cells and protein levels in dentate gyrus of these animals in adulthood. The results revealed a decrease in glutamate receptor 2 (GluR2) mRNA expression and protein levels as well as an increase in protein levels for the excitatory amino acid carrier 1 (EAAC1) in P10 SE rats compared to controls. Expression of glutamate receptor 1 (GluR1) mRNA was decreased in both P10 SE rats and identically handled, lithium‐injected littermate controls compared to naive animals, and GluR1 protein levels were significantly lower in lithium‐controls than in naive rats, suggesting an effect of either the handling or the lithium on GluR1 expression. These changes in EAA receptors and transporters were accompanied by an increased susceptibility to kainic acid induced seizures in P10 SE rats compared to controls. The current data suggest that early‐life status‐epilepticus can result in permanent alterations in glutamate receptor and transporter gene expression, which may contribute to a lower seizure threshold.
The voltage‐gated calcium channel UNC‐2 is involved in stress‐mediated regulation of tryptophan hydroxylase
Authors: Estevez Miguel , Estevez Annette O. , Cowie Robin H. , Gardner Kathy L. 
Published: July 2010

AbstractMigraine is an episodic pain disorder whose pathophysiology is related to deficiency of serotonin signaling and abnormal function of the P/Q‐type calcium channel, CACNA1A. Because the relationship of the CACNA1A channel to serotonin signaling is unknown and potentially of therapeutic interest we have used genetic analysis of the Caenorhabditis elegans ortholog of this calcium channel, UNC‐2, to help identify candidate downstream effectors of the human channel. By genetic dissection of the lethargic mutant phenotype of unc‐2, we have established an epistasis pathway showing that UNC‐2 function antagonizes a transforming growth factor (TGF)‐β pathway influencing movement rate. This same UNC‐2/TGF‐β pathway is required for accumulation of normal serotonin levels and stress‐induced modulation of tryptophan hydroxylase (tph) expression in the serotonergic chemosensory ADF neurons, but not the NSM neurons. We also show that transgenic expression of the migraine‐associated Ca2+ channel, CACNA1A, in unc‐2 animals can functionally substitute for UNC‐2 in stress‐activated regulation of tph expression. The demonstration that these evolutionarily related channels share a conserved ability to modulate tph expression through their effects on TGF‐β signaling provides the first specific example of how CACNA1A function may influence levels of the critical migraine neurotransmitter serotonin.