bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional protein kinase arrays reveal inhibition of p‐21‐activated kinase 4 by α‐synuclein oligomers
Authors: Danzer Karin M. , Schnack Cathrin , Sutcliffe Andrew , Hengerer Bastian , Gillardon Frank 
Published: September 2007

AbstractThere is increasing evidence that aggregation of α‐synuclein contributes to the functional and structural deterioration in the CNS of Parkinson’s disease patients and transgenic animal models. α‐Synuclein binds to various cellular proteins and aggregated α‐synuclein species may affect their physiological function. In the present study, we used protein arrays spotted with 178 active human kinases for a large‐scale analysis of the effects of recombinant α‐synuclein on kinase activities. Incubation with globular α‐synuclein oligomers significantly inhibited autophosphorylation of p21‐activated kinase (PAK4) compared to treatment with monomeric α‐synuclein or β‐synuclein. A concentration‐dependent inhibition was also observed in a solution‐based kinase assay. To show in vivo relevance, we analyzed brainstem protein extracts from α‐synuclein (A30P) transgenic mice where accumulation of α‐synuclein oligomers has been demonstrated. By immunoblotting using a phospho‐specific antibody, we detected a significant decline in phosphorylation of LIM kinase 1, a physiological substrate for PAK4. Suppression of PAK activity by amyloid‐β oligomers has been reported in Alzheimer’s disease. Thus, PAKs may represent a target for various neurotoxic protein oligomers, and signaling deficits may contribute to the behavioral defects in chronic neurodegenerative diseases.
Hierarchical recruitment by AMPA but not staurosporine of pro‐apoptotic mitochondrial signaling in cultured cortical neurons: evidence for caspase‐dependent/independent cross‐talk
Authors: Beart Philip M. , Lim Maria L. R. , Chen Baohong , Diwakarla Shanti , Mercer Linda D. , Cheung Nam Sang , Nagley Phillip 
Published: September 2007

AbstractExcitotoxicity mediated via the (S)‐α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) subtype of receptor for l‐glutamate contributes to various neuropathologies involving acute brain injury and chronic degenerative disorders. In this study, AMPA‐induced neuronal injury and staurosporine (STS)‐mediated apoptosis were compared in primary neuronal cultures of murine cerebral cortex by analyzing indices up‐ and downstream of mitochondrial activation. AMPA‐mediated apoptosis involved induction of Bax, loss of mitochondrial transmembrane potential (ΔΨm), early release of cytochrome c (cyt c), and more delayed release of second mitochondrial activator of caspases (SMAC), Omi, and apoptosis‐inducing factor (AIF) with early calpain and minor late activation of caspase 3. STS‐induced apoptosis was characterized by a number of differences, a more rapid time course, non‐involvement of ΔΨm, and relatively early recruitment of SMAC and caspase 3. The AMPA‐induced rise in intracellular calcium appeared insufficient to evoke ΔΨm as release of cyt c preceded mitochondrial depolarization, which was followed by the cytosolic translocation of SMAC, Omi, and AIF. Bax translocation preceded cyt c release for both stimuli inferring its involvement in apoptotic induction. Inclusion of the broad spectrum caspase inhibitor zVAD‐fmk reduced the AMPA‐induced release of cyt c, SMAC, and AIF, while only affecting the redistribution of Omi and AIF in the STS‐treated neurons. Only AIF release was affected by a calpain inhibitor (calpastatin) which exerted relatively minor effects on the progression of cellular injury. AMPA‐mediated release of apoptogenic proteins was more hierarchical relative to STS with its calpain activation and caspase‐dependent AIF redistribution arguing for a model with cross‐talk between caspase‐dependent/independent apoptosis.
Excitotoxic loss of post‐synaptic sites is distinct temporally and mechanistically from neuronal death
Authors: Waataja Jonathan J. , Kim Hee Jung , Roloff Alan M. , Thayer Stanley A. 
Published: September 2007

AbstractDendritic degeneration and loss of synaptic proteins are early events correlated with functional decline in neurodegenerative disease. The temporal and mechanistic relationship between synapse loss and cell death, however, remains unclear. We used confocal microscopy and image processing to count post‐synaptic sites on rat hippocampal neurons by expressing post‐synaptic density protein 95 fused to green fluorescent protein. Fluorescent puncta co‐localized with neurotransmitter release sites, NMDA‐induced Ca2+ increases and NMDA receptor immunoreactivity. During excitotoxic neurodegeneration, synaptic sites were lost and synaptic transmission impaired. These changes were mediated by NMDA receptors and required Ca2+‐dependent activation of the proteasome pathway. Tracking synapses from the same cell following brief neurotoxic insult revealed transient loss followed by recovery. The time‐course, concentration‐dependence and mechanism for loss of post‐synaptic sites were distinct from those leading to cell death. Cells expressing p14ARF, which inhibits ubiquitination of post‐synaptic density protein 95 and prevents loss of synaptic sites, displayed an increased sensitivity to glutamate‐induced cell death. Thus, excitotoxic synapse loss may be a disease‐modifying process rather than an obligatory step leading to cell death. These results demonstrate the importance of assessing synaptic function independent of neuronal survival during neurodegeneration and indicate that this approach will be useful for identifying toxins that degrade synaptic connections and for screening for agents that protect synaptic function.
Seizure‐induced formation of isofurans: novel products of lipid peroxidation whose formation is positively modulated by oxygen tension
Authors: Patel Manisha , Liang Li‐Ping , Hou Huagang , Williams Benjamin B. , Kmiec Maciej , Swartz Harold M. , Fessel Joshua P. , Roberts L. Jackson 
Published: September 2007

AbstractWe have previously shown that seizures induce the formation of F2‐isoprostanes (F2‐IsoPs), one of the most reliable indices of oxidative stress in vivo. Isofurans (IsoFs) are novel products of lipid peroxidation whose formation is favored by high oxygen tensions. In contrast, high oxygen tensions suppress the formation of F2‐IsoPs. The present study determined seizure‐induced formation of IsoFs and its relationship with cellular oxygen levels (pO2). Status epilepticus (SE) resulted in F2‐IsoP and IsoF formation, with overlapping but distinct time courses in hippocampal subregions. IsoF, but not F2‐IsoP formation coincided with mitochondrial oxidative stress. SE resulted in a transient decrease in hippocampal pO2 measured by in vivo electron paramagnetic resonance oximetry suggesting an early phase of seizure‐induced hypoxia. Seizure‐induced F2‐IsoP formation coincided with the peak hypoxia phase, whereas IsoF formation coincided with the ‘reoxygenation’ phase. These results demonstrate seizure‐induced increase in IsoF formation and its correlation with changes in hippocampal pO2 and mitochondrial dysfunction.
GSK3β mediates the induced expression of synaptic acetylcholinesterase during apoptosis
Authors: Jing Peng , Jin Qihuang , Wu Jun , Zhang Xue‐Jun 
Published: September 2007

AbstractBesides its role in terminating acetylcholine‐mediated neurotransmission, acetylcholinesterase (AChE) is found to be expressed and participate in the process of apoptosis in various cell types. However, the mechanisms underlying AChE up‐regulation in neuronal cells remain elusive. Herein we demonstrated that glycogen synthase kinase‐3β (GSK3β) mediates induced AChE‐S expression during apoptosis. In this study, A23187 and thapsigargin (TG) were employed to induce apoptosis in neuroendocrine PC12 cells. The results showed that exposure of PC12 cells to A23187 and TG up‐regulated AChE activity significantly. The same treatment also led to activation of GSK3β. Two different inhibitors of GSK3β (lithium and GSK3β‐specific inhibitor VIII) could block A23187‐ or TG‐induced up‐regulation of AChE activity, AChE‐S mRNA level and protein expression. However, lithium could not inhibit the induction of AChE‐R mRNA and protein under similar conditions. Taken together, our results show that GSK3β is specifically involved in the induction of AChE‐S expression in PC12 cells during apoptosis.
Iron trafficking inside the brain
Authors: Moos Torben , Nielsen Thomas Rosengren , Skjørringe Tina , Morgan Evan H. 
Published: September 2007

AbstractIron, an essential element for all cells of the body, including those of the brain, is transported bound to transferrin in the blood and the general extracellular fluid of the body. The demonstration of transferrin receptors on brain capillary endothelial cells (BCECs) more than 20 years ago provided the evidence for the now accepted view that the first step in blood to brain transport of iron is receptor‐mediated endocytosis of transferrin. Subsequent steps are less clear. However, recent investigations which form the basis of this review have shed some light on them and also indicate possible fruitful avenues for future research. They provide new evidence on how iron is released from transferrin on the abluminal surface of BCECs, including the role of astrocytes in this process, how iron is transported in brain extracellular fluid, and how iron is taken up by neurons and glial cells. We propose that the divalent metal transporter 1 is not involved in iron transport through the BCECs. Instead, iron is probably released from transferrin on the abluminal surface of these cells by the action of citrate and ATP that are released by astrocytes, which form a very close relationship with BCECs. Complexes of iron with citrate and ATP can then circulate in brain extracellular fluid and may be taken up in these low‐molecular weight forms by all types of brain cells or be bound by transferrin and taken up by cells which express transferrin receptors. Some iron most likely also circulates bound to transferrin, as neurons contain both transferrin receptors and divalent metal transporter 1 and can take up transferrin‐bound iron. The most likely source for transferrin in the brain interstitium derives from diffusion from the ventricles. Neurons express the iron exporting carrier, ferroportin, which probably allows them to excrete unneeded iron. Astrocytes lack transferrin receptors. Their source of iron is probably that released from transferrin on the abluminal surface of BCECs. They probably to export iron by a mechanism involving a membrane‐bound form of the ferroxidase, ceruloplasmin. Oligodendrocytes also lack transferrin receptors. They probably take up non‐transferrin bound iron that gets incorporated in newly synthesized transferrin, which may play an important role for intracellular iron transport.
Localization of the membrane‐anchored MMP‐regulator RECK at the neuromuscular junctions
Authors: Kawashima Satoshi , Imamura Yukio , Chandana Ediriweera P. S. , Noda Toru , Takahashi Rei , Adachi Eijiro , Takahashi Chiaki , Noda Makoto 
Published: September 2007

AbstractNerve apposition on nicotinic acetylcholine receptor clusters and invagination of the post‐synaptic membrane (i.e. secondary fold formation) occur by embryonic day 18.5 at the neuromuscular junctions (NMJs) in mouse skeletal muscles. Finding the molecules expressed at the NMJ at this stage of development may help elucidating how the strong linkage between a nerve terminal and a muscle fiber is established. Immunohistochemical analyses indicated that the membrane‐anchored matrix metalloproteinase regulator RECK was enriched at the NMJ in adult skeletal muscles. Confocal and electron microscopy revealed the localization of RECK immunoreactivity in secondary folds and subsynaptic intracellular compartments in muscles. Time course studies indicated that RECK immunoreactivity becomes associated with the NMJ in the diaphragm at around embryonic day 18.5 and thereafter. These findings, together with known properties of RECK, support the hypothesis that RECK participates in NMJ formation and/or maintenance, possibly by protecting extracellular components, such as synaptic basal laminae, from proteolytic degradation.
Kir4.1 channels regulate swelling of astroglial processes in experimental spinal cord edema
Authors: Dibaj Payam , Kaiser Melanie , Hirrlinger Johannes , Kirchhoff Frank , Neusch Clemens 
Published: September 2007

AbstractIn glial cells, inwardly rectifying K+ channels (Kir) control extracellular [K+]o homeostasis by uptake of K+ from the extracellular space and release of K+ into the microvasculature. Kir channels were also recently implicated in K+‐associated water influx and cell swelling. We studied the time‐dependent expression and functional implication of the glial Kir4.1 channel for astroglial swelling in a spinal cord edema model. In this CNS region, Kir4.1 is expressed on astrocytes from the second postnatal week on and co‐localizes with aquaporin 4 (AQP4). Swelling of individual astrocytes in response to osmotic stress and to pharmacological Kir blockade were analyzed by time‐lapse‐two‐photon laser‐scanning microscopy in situ. Application of 30% hypotonic solution induced astroglial soma swelling whereas no swelling was observed on astroglial processes or endfeet. Co‐application of hypotonic solution and Ba2+, a Kir channel blocker, induced prominent swelling of astroglial processes. In Kir4.1−/− mice, however, somatic as well as process swelling was observed upon application of 30% hypotonic solutions. No additional effect was provoked upon co‐application with Ba2+. Our experiments show that Kir channels prevent glial process swelling under osmotic stress. The underlying Kir channel subunit that controls glial process swelling is Kir4.1, whereas changes of the glial soma are not substantially related to Kir4.1.
The α1 subunit of nicotinic acetylcholine receptors in the inner ear: transcriptional regulation by ATOH1 and co‐expression with the γ subunit in hair cells
Authors: Scheffer Deborah , Sage Cyrille , Plazas Paola V. , Huang Mingqian , Wedemeyer Carolina , Zhang Duan‐Sun , Chen Zheng‐Yi , Elgoyhen A. Belen , Corey David P. , Pingault Veronique 
Published: September 2007

AbstractAcetylcholine is a key neurotransmitter of the inner ear efferent system. In this study, we identify two novel nAChR subunits in the inner ear: α1 and γ, encoded by Chrna1 and Chrng, respectively. In situ hybridization shows that the messages of these two subunits are present in vestibular and cochlear hair cells during early development. Chrna1 and Chrng expression begin at embryonic stage E13.5 in the vestibular system and E17.5 in the organ of Corti. Chrna1 message continues through P7, whereas Chrng is undetectable at post‐natal stage P6. The α1 and γ subunits are known as muscle‐type nAChR subunits and are surprisingly expressed in hair cells which are sensory‐neural cells. We also show that ATOH1/MATH1, a transcription factor essential for hair cell development, directly activates CHRNA1 transcription. Electrophoretic mobility‐shift assays and supershift assays showed that ATOH1/E47 heterodimers selectively bind on two E boxes located in the proximal promoter of CHRNA1. Thus, Chrna1 could be the first transcriptional target of ATOH1 in the inner ear. Co‐expression in Xenopus oocytes of the α1 subunit does not change the electrophysiological properties of the α9α10 receptor. We suggest that hair cells transiently express α1γ‐containing nAChRs in addition to α9α10, and that these may have a role during development of the inner ear innervation.
The role of the cannabinoid type 1 receptor and down‐stream cAMP/DARPP‐32 signal in the nucleus accumbens of methamphetamine‐sensitized rats
Authors: Chiang Yao‐Chang , Chen Jin‐Chung 
Published: September 2007

AbstractBlockade of the cannabinoid type 1 (CB1) receptor could suppress methamphetamine self‐administration; however, the cellular mechanism remains unclear. In this study, we intended to investigate the significance of brain CB1receptors on the development of behavioral sensitization to methamphetamine. Male Sprague‐Dawley rats treated with chronic methamphetamine (4 mg/kg, i.p.) for either 7 or 14 days developed behavioral sensitization to methamphetamine (1 mg/kg) at withdrawal day 7. A progressive decrease in numbers of CB1receptor (bothBmaxand mRNA) but increase in binding affinity (Kd) was noticed during withdrawal days 3 to 7. Microinjection of CB1antagonist [5‐(4‐bromophenyl)‐1‐(2,4‐dichlorophenyl)‐4‐ethyl‐N‐(1‐piperidinyl)‐1H‐pyrazole‐3‐carboxamide] into the nucleus accumbens (NAc) at withdrawal day 7, significantly suppressed the behavioral sensitization to methamphetamine. In NAc brain slices preparation, acute incubation with CB1agonist (1R,3R,4R)‐3‐[2‐hydroxy‐4‐(1,1‐dimethylheptyl)phenyl]‐4‐(3‐hydroxypropyl)cyclohexan‐1‐ol (CP 55940) dose‐dependently enhanced cAMP accumulation in sensitized rats; no change was noticed in control groups. Consequently, treatment of CP 55940 induced a dose‐dependent (10 nmol/L–10 μmol/L) phosphorylation on down‐stream dopamine and cAMP‐regulated phosphoprotein of Mr 32 000 (DARPP‐32)/Thr34 in sensitized rats, while only 10 μmol/L CP 55940 was able to enhance the phosphoDARPP‐32/T34 in control groups. Alternatively, both basal activity of calcineurin (PP‐2B) and CP 55940‐induced changes in the amount of PP‐2B in the NAc were both decreased in sensitized rats, but not in controls. Overall, we demonstrated that brain CB1receptor and its down‐stream cAMP/DARPP‐32/T34/PP‐2B signaling are profoundly altered in methamphetamine‐sensitized animals.
Replacement of histidine in position 105 in the α5subunit by cysteine stimulates zolpidem sensitivity of α5β2γ2GABAAreceptors
Authors: Baur Roland , Sigel Erwin 
Published: September 2007

AbstractZolpidem is a positive allosteric modulator of GABAAreceptors with sensitivity to subunit composition. While it acts with high affinity and efficacy at GABAAreceptors containing the α1subunit, it has a lower affinity to GABAAreceptors containing α2, α3, or α5subunits and has a very weak efficacy at receptors containing the α5subunit. Here, we show that replacing histidine in position 105 in the α5subunit by cysteine strongly stimulates the effect of zolpidem in receptors containing the α5subunit. The side chain volume of the amino acid residue in this position does not correlate with the modulation by zolpidem. Interestingly, serine is not able to promote the potentiation by zolpidem. The homologous residues to α5H105 in α1, α2, and α3are well‐known determinants of the action of classical benzodiazepines. Other studies have shown that replacement of these histidines α1H101, α2H101, and α3H126 by arginine, as naturally present in α4and α6, leads to benzodiazepine insensitivity of these receptors. Thus, the nature of the amino acid residue in this position is not only crucial for the action of classical benzodiazepines but in α5containing receptors also for the action of zolpidem.
An exposed carboxyl group on sialic acid is essential for gangliosides to inhibit calcium uptake via the sarco/endoplasmic reticulum Ca2+‐ATPase: relevance to gangliosidoses
Authors: Ginzburg Luba , Li Su‐Chen , Li Yu‐Teh , Futerman Anthony H. 
Published: September 2007

AbstractWe previously observed that gangliosides GM2, GM1, and GM3 inhibit Ca2+‐uptake via the sarco/endoplasmic reticulum Ca2+‐ATPase (SERCA) in neurons and in brain microsomes. We now systematically examine the effect of various gangliosides and their analogs on Ca2+‐uptake via SERCA and demonstrate that an exposed carboxyl group on the ganglioside sialic acid residue is required for inhibition. Thus, asialo‐GM2 and asialo‐GM1 have no inhibitory effect, and modifications of the carboxyl group of GM1 and GM2 into a hydroxymethyl residue (CH2OH), a methyl ester (COOCH3) or a taurine‐conjugated amide (CONHCH2CH2SO3H) drastically diminish their inhibitory activities. We also demonstrate that the saccharides must be attached to a ceramide backbone in order to inhibit SERCA as the ceramide‐free ganglioside saccharides only inhibit SERCA to a minimal extent. Finally, we attempted to use the ceramide‐free ganglioside saccharides to antagonize the effects of the gangliosides on SERCA; although some reversal was observed, the inhibitory effects of the gangliosides were not completely abolished.
Up‐regulation of L‐type high voltage‐gated calcium channel subunits by sustained exposure to 1,4‐ and 1,5‐benzodiazepines in cerebrocortical neurons
Authors: Katsura Masashi , Shibasaki Masahiro , Kurokawa Kazuhiro , Tsujimura Atsushi , Ohkuma Seitaro 
Published: September 2007

AbstractThe aim of this study is to examine how sustained exposure to two 1,4‐benzodiazepines (BZDs) with different action period, diazepam and brotizolam, and a 1,5‐BZD, clobazam, affects L‐type high voltage‐gated calcium channel (HVCC) functions and its mechanisms using primary cultures of mouse cerebral cortical neurons. The sustained exposure to these three BZDs increased [45Ca2+] influx, which was due to the enhanced [45Ca2+] entry through L‐type HVCCs but not through of Cav2.1 and Cav2.2. Increase in [3H]diltiazem binding after the exposure to these three BZDs was due to the increase in the binding sites of [3H]diltiazem. Western blot analysis showed increase of Cav1.2 and Cav1.3 in association with the increased expression of α2/δ1 subunit. Similar changes in [3H]diltiazem binding and L‐type HVCC subunit expression were found in the cerebral cortex from mouse with BZD physical dependence. These results indicate that BZDs examined here have the potential to increase L‐type HVCC functions mediated via the enhanced expression of not only Cav1.2 and Cav1.3 but also α2/δ1 subunit after their sustained exposure, which may participate in the development of physical dependence by these BZDs.
Cerebrospinal fluid concentrations of peptides derived from chromogranin B and secretogranin II are decreased in multiple sclerosis
Authors: Mattsson Niklas , Rüetschi Ulla , Podust Vladimir N. , Stridsberg Mats , Li Susann , Andersen Oluf , Haghighi Sara , Blennow Kaj , Zetterberg Henrik 
Published: September 2007

AbstractNovel biomarkers for multiple sclerosis (MS) could improve diagnosis and provide clues to pathogenesis. In this study surface‐enhanced laser desorption/ionization time‐of‐flight mass spectrometry was used to analyze protein expression in CSF from 46 MS patients, 46 healthy siblings to the patients, and 50 unrelated healthy controls. Twenty‐four proteins in the mass range 2–10 kDa were expressed at significantly different levels (p < 0.01) in a robust manner when comparing the three groups. Identities of three proteins were determined using biochemical purification followed by tandem mass spectrometric analysis. Immunoprecipitation experiments confirmed the identities for two peptides derived from chromogranin B (m/z 6252) and from secretogranin II (m/z 3679). These peptides were all decreased in MS when compared with siblings or controls. Radioimmunoassays specific for each peptide confirmed these differences. The lowered concentrations did not correlate to the axonal damage marker neurofilament light protein and may thus reflect functional changes rather than neurodegeneration. Further studies will investigate the involvement of these peptides in MS pathogenesis.