RSSAxon formation in neocortical neurons depends on stage-specific regulation of microtubule stability by the dual leucine zipper kinase-c-Jun N-terminal kinase pathway.
Source
Department of Molecular Biology, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan. sh3312@med.yokohama-cu.ac.jp
Abstract
Studies using cultured neurons have established the critical role of microtubule regulators in neuronal polarization. The c-Jun N-terminal kinase (JNK) pathway is one of the candidate signaling pathways driving microtubule regulation during neuronal polarization. However, the significance of the JNK pathway in axon formation, a fundamental step in neuronal polarization, in vivo, remains unclear. Here, we provide evidence supporting the notion that the JNK pathway contributes to axon formation, in vivo, by identifying the genetic interactions between mouse JNK1 and dual leucine zipper kinase (DLK). Double mutants exhibited severe defects in axon formation in the cerebral neocortex. Moreover, RNA interference rescue experiments, in vitro, showed that DLK and JNK1 function in a common pathway to support neuronal polarization by promoting short-neurite and axon formation. Defects in axon formation caused by perturbations of the DLK-JNK pathway were significantly improved by Taxol. However, defects in short-neurite formation caused by perturbations of the DLK-JNK pathway were enhanced by Taxol. Together, these in vivo and in vitro observations indicate that the DLK-JNK pathway facilitates axon formation in neocortical neurons via stage-specific regulation of microtubule stability.
Young coconut juice, a potential therapeutic agent that could significantly reduce some pathologies associated with Alzheimer's disease: novel findings.
Source
Department of Anatomy, Faculty of Science, Prince of Songkla University, Hat Yai, Thailand.
Abstract
Brains from ovariectomised (ovx) rats can display features similar to those observed in menopausal women with Alzheimer's disease (AD), and oestrogen seems to play a key role. Preliminary studies on young coconut juice (YCJ) have reported the presence of oestrogen-like components in it. The aim of the study was to investigate the effects of YCJ on the AD pathological changes in the brains of ovx rats. Rat groups included sham-operated, ovx, ovx+oestradiol benzoate (EB) and ovx+YCJ. Brain sections (4 μm) were taken and were immunostained with β-amyloid (Aβ) 1-42, glial fibrillary acidic protein (GFAP) (an intermediate neurofilament of astrocytes) and Tau-1 antibodies. Aβ 1-42, GFAP andTau-1 are considered as reliable biomarkers of amyloidosis, astrogliosis and tauopathy (neurofibrillary tangles), respectively, which in turn are characteristic features associated with AD. The serum oestradiol (E2) level was measured using a chemiluminescent immunoassay technique. YCJ restored the serum E2 to levels significantly (P < 0·001) higher than that of the ovx group, and even that of the sham group. Aβ deposition was significantly (P < 0·0001) reduced in the cerebral cortex of the YCJ group, as compared with the ovx group and with the sham and ovx+EB groups (P < 0·01). A similar trend was observed in relation to GFAP expression in the cerebral cortex and to Tau-1 expression in the hippocampus. This is a novel study demonstrating that YCJ could have positive future implications in the prevention and treatment of AD in menopausal women.
Inhibition of tau hyperphosphorylation and beta amyloid production in rat brain by oral administration of atorvastatin.
Source
Department of Neurology, People's Hospital of Henan Province, Zhengzhou, Henan 450003, China.
Abstract
BACKGROUND:
Alzheimer's disease (AD) is a neurodegenerative disorder and the leading cause of dementia in the elderly. The two hallmark lesions in AD brain are deposition of amyloid plaques and neurofibrillary tangles (NFTs). Hypercholesteremia is one of the risk factors of AD. But its role in the pathogenesis of AD is largely unknown. The aim of this study was to investigate the relationship between hypercholesteremia and tau phosphorylation or beta-amyloid (Abeta), and evaluate the effect of atorvastatin on the level of tau phosphorylation and Abeta in the brains of rats fed with high cholesterol diet.
METHODS:
Sprague-Dawley (SD) rats were randomly divided into normal diet control group, high cholesterol diet group, and high cholesterol diet plus atorvastatin (Lipitor, 15 mg x kg(-1) x d(-1)) treated group. Blood from caudal vein was collected to measure total cholesterol (TC), triglyceride (TG), low density lipoprotein (LDL) and high-density lipoprotein (HDL) at the end of the 3rd and the 6th months by an enzymatic method. The animals were sacrificed 6 months later and brains were removed. All left brain hemispheres were fixed for immunohistochemistry. Hippocampus and cerebral cortex were separated from right hemispheres and homogenized separately. Tau phosphorylation and Abeta in the brain tissue were determined by Western blotting (using antibodies PHF-1 and Tau-1) and anti-Abeta40/anti-Abeta42, respectively.
RESULTS:
We found that high cholesterol diet led to hypercholesteremia of rats as well as hyperphosphorylation of tau and increased Abeta level in the brains. Treatment of the high cholesterol diet fed rats with atorvastatin prevented the changes of both tau phosphorylation and Abeta level induced by high cholesterol diet.
CONCLUSIONS:
Hypercholesteremia could induce tau hyperphosphorylation and Abeta production in rat brain. Atorvastatin could inhibit tau hyperphosphorylation and decrease Abeta generation. It may play a protective role in the patho-process of hypercholesteremia-induced neurodegeneration in the brain.
Subcellular rearrangement of hsp90-binding immunophilins accompanies neuronal differentiation and neurite outgrowth.
Source
Instituto de Biología y Medicina Experimental/CONICET, Buenos Aires, Argentina.
Abstract
FKBP51 and FKBP52 (FK506-binding protein 51 and 52) are tetratricopeptide repeat-domain immunophilins belonging to the tetratricopeptide-protein•hsp90•hsp70•p23 heterocomplex bound to steroid receptors. Immunophilins are related to receptor folding, subcellular localization, and hormone-dependent transcription. Also, they bind the immunosuppressant macrolide FK506, which shows neuroregenerative and neuroprotective actions by a still unknown mechanism. In this study, we demonstrate that in both, undifferentiated neuroblastoma cells and embryonic hippocampal neurons, the FKBP52•hsp90•p23 heterocomplex concentrates in a perinuclear structure. Upon cell stimulation with FK506, this structure disassembles and this perinuclear area becomes transcriptionally active. The acquisition of a neuronal phenotype is accompanied by increased expression of βIII-tubulin, Map-2, Tau-1, but also hsp90, hsp70, p23, and FKBP52. During the early differentiation steps, the perinuclear heterocomplex redistributes along the cytoplasm and nascent neurites, p23 binds to intermediate filaments and microtubules acquired higher filamentary organization. While FKBP52 moves towards neurites and concentrates in arborization bodies and terminal axons, FKBP51, whose expression remains constant, replaces FKBP52 in the perinuclear structure. Importantly, neurite outgrowth is favored by FKBP52 over-expression or FKBP51 knock-down, and is impaired by FKBP52 knock-down or FKBP51 over-expression, indicating that the balance between these FK506-binding proteins plays a key role during the early mechanism of neuronal differentiation.
© 2010 The Authors. Journal of Neurochemistry © 2010 International Society for Neurochemistry.
Neurites from PC12 cells are connected to each other by synapse-like structures.
Source
Department of Biochemistry, College of Medicine, Hallym University, Chuncheon, Kangwon-Do, 200-702, Republic of Korea.
Abstract
PC12 cells have been used as a model of sympathetic neurons. Nerve growth factor (NGF), basic fibroblast growth factor (bFGF), and cAMP induce neurite outgrowth from PC12 cells. cAMP induced a greater number of neurites than did NGF. In particular, we attempted to elucidate whether PC12 cell neurites, induced by several factors including NGF, bFGF, and cAMP, form synapses, and whether each neurite has presynaptic and postsynaptic properties. Using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), we observed that neurites are connected to each other. The connected regions presented dense core vesicles and a clathrin-coated membrane invagination. In addition, typical maker proteins for axon and dendrite were identified by an immuno-staining method.Tau-1, an axonal marker in neurons, was localized at a high concentration in the terminal tips of neurites from PC12 cells, which were connected to neurite processes containing MAP-2, a dendritic marker in neurons. Furthermore, neurites containing SV2 and synaptotagmin, markers of synaptic vesicles, were in contact with neurites harboring drebrin, a marker of the postsynaptic membrane, suggesting that neurites from PC12 cells induced by NGF, bFGF, and cAMP may form synapse-like structures. Tat-C3 toxin, a Rho inhibitor, augmented neurite outgrowth induced by NGF, bFGF, and cAMP. Tat-C3 toxin together with neurotrophins also exhibited synapse-like structures between neurites. However, it remains to be studied whether RhoA inhibition plays a role in the formation of synapse-like structures in PC12 cells.
(c) 2010 Wiley-Liss, Inc.
Acetylation of microtubules influences their sensitivity to severing by katanin in neurons and fibroblasts.
Source
Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, USA.
Abstract
Here we investigated whether the sensitivity of microtubules to severing by katanin is regulated by acetylation of the microtubules. During interphase, fibroblasts display long microtubules with discrete regions rich in acetylated tubulin. Overexpression of katanin for short periods of time produced breaks preferentially in these regions. In fibroblasts with experimentally enhanced or diminished microtubule acetylation, the sensitivity of the microtubules to severing by katanin was increased or decreased, respectively. In neurons, microtubules are notably more acetylated in axons than in dendrites. Experimental manipulation of microtubule acetylation in neurons yielded similar results on dendrites as observed on fibroblasts. However, under these experimental conditions, axonal microtubules were not appreciably altered with regard to their sensitivity to katanin. We hypothesized that this may be attributable to the effects of tau on the axonal microtubules, and this was validated by studies in which overexpression of tau caused microtubules in dendrites and fibroblasts to be more resistant to severing by katanin in a manner that was not dependent on the acetylation state of the microtubules. Interestingly, none of these various findings apply to spastin, because the severing of microtubules by spastin does not appear to be strongly influenced by either the acetylation state of the microtubules or tau. We conclude that sensitivity to microtubule severing by katanin is regulated by a balance of factors, including the acetylation state of the microtubules and the binding of tau to the microtubules. In the neuron, this contributes to regional differences in the microtubule arrays of axons and dendrites.
Minocycline treatment reduces white matter damage after excitotoxic striatal injury.
Source
Edmond and Lily Safra International Institute of Neuroscience of Natal, Natal/RN, Brazil.
Abstract
We investigated the protective effects of minocycline following white matter damage (WMD) in the rat striatum. Excitotoxic lesions were induced by N-Methyl-d-Aspartate (NMDA) microinjections and caused striatal damage, concomitant with microglial/macrophage activation. The excitotoxic lesion both damaged oligodendrocytes (Tau-1(+) cells) and caused a decrease in tissue reactivity for myelin basic protein (MBP) after post-lesional day 3 (PLD). Treatment with the semi-synthetic tetracycline antibiotic minocycline, however, led to oligodendrocyte preservation and decreased myelin impairment. Taken together, these results suggest that white matter damage (WMD) is an important component of the physiopathology of acute striatal damage and that microglial/macrophage activation contributes to this pathological phenomenon.
Copyright 2010 Elsevier B.V. All rights reserved.
Tau dephosphorylation potentiates apoptosis by mechanisms involving a failed dephosphorylation/activation of Bcl-2.
Source
Department of Pathophysiology, Huazhong University of Science and Technology, Wuhan, China.
Abstract
Phosphorylation of tau, a major microtubule-associated protein, has been recently discovered to affect cell apoptosis. While the phosphorylation of tau is dynamically regulated, the role of tau dephosphorylation in cell viability is elusive. Here, we observed that the cells bearing high level of the dephosphorylated tau at Tau-1 epitope were more vulnerable to the apoptosis induced by staurosporine, camptothecin, and hydrogen peroxide, though the general outcome of tau expression was still anti-apoptotic. Further studies demonstrate that co-expression of tau and protein phosphatase 2A catalytic subunit (PP2Ac), the most active tau phosphatase, potentiates cell apoptosis with a correlatively increased dephosphorylation of tau and phosphorylation of Bcl-2 at Ser87 (pS87-Bcl2, the inactive form of the anti-apoptotic factor), whereas expression of PP2Ac alone in the absence of tau decreases the levels of pS87-Bcl2 and cleaved PARP, markers of early apoptosis. Finally, both tau and Bcl-2 were co-immunoprecipitated with PP2Ac, but the binding level of Bcl-2 with PP2Ac decreased prominently when tau was co-expressed. These data suggest that tau dephosphorylation by PP2Ac facilitates cell apoptosis with the mechanisms involving a failed dephosphorylation/activation of Bcl-2.
- PMID:
- 20157251
- [PubMed - indexed for MEDLINE]
Impaired balance of mitochondrial fission and fusion in Alzheimer's disease.
Source
Department of Pathology, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Abstract
Mitochondrial dysfunction is a prominent feature of Alzheimer's disease (AD) neurons. In this study, we explored the involvement of an abnormal mitochondrial dynamics by investigating the changes in the expression of mitochondrial fission and fusion proteins in AD brain and the potential cause and consequence of these changes in neuronal cells. We found that mitochondria were redistributed away from axons in the pyramidal neurons of AD brain. Immunoblot analysis revealed that levels of DLP1 (also referred to as Drp1), OPA1, Mfn1, and Mfn2 were significantly reduced whereas levels of Fis1 were significantly increased in AD. Despite their differential effects on mitochondrial morphology, manipulations of these mitochondrial fission and fusion proteins in neuronal cells to mimic their expressional changes in AD caused a similar abnormal mitochondrial distribution pattern, such that mitochondrial density was reduced in the cell periphery of M17 cells or neuronal process of primary neurons and correlated with reduced spine density in the neurite. Interestingly, oligomeric amyloid-beta-derived diffusible ligands (ADDLs) caused mitochondrial fragmentation and reduced mitochondrial density in neuronal processes. More importantly, ADDL-induced synaptic change (i.e., loss of dendritic spine and postsynaptic density protein 95 puncta) correlated with abnormal mitochondrial distribution. DLP1 overexpression, likely through repopulation of neuronal processes with mitochondria, prevented ADDL-induced synaptic loss, suggesting that abnormal mitochondrial dynamics plays an important role in ADDL-induced synaptic abnormalities. Based on these findings, we suggest that an altered balance in mitochondrial fission and fusion is likely an important mechanism leading to mitochondrial and neuronal dysfunction in AD brain.
Tau dephosphorylation and microfilaments disruption are upstream events of the anti-proliferative effects of DADS in SH-SY5Y cells.
Source
Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica, 00133, Rome, Italy.
Abstract
Garlic organosulphur compounds have been successfully used as redox anti-proliferative agents. In this work, we dissect the effects of diallyl disulphide (DADS) focusing on the events upstream of cell cycle arrest and apoptosis induced in neuroblastoma SH-SY5Y cells. We demonstrate that DADS is able to cause early morphological changes, cytoskeleton oxidation, microfilaments reduction and depolymerization of microtubules. These events are attenuated in cells stably overexpressing the antioxidant enzyme SOD1, suggesting that superoxide plays a crucial role in destabilizing cytoskeleton. Moreover, we evidence that the main microtubules-associated protein Tau undergoes PP1-mediated dephosphorylation as demonstrated by treatment with okadaic acid as well as by immunoreaction with anti-Tau-1 antibody, which specifically recognizes its dephosphorylated forms. Tau dephosphorylation is inhibited by the two-electron reductants NAC and GSH ester but not by SOD1. The inability of DADS to induce apoptosis in neuroblastoma-differentiated cells gives emphasis to the anti-proliferative activity of DADS, which can be regarded as a promising potent anti-neuroblastoma drug by virtue of its widespread cytoskeleton disrupting action on proliferating cells.
Anti-cancer drug induced neurotoxicity and identification of Rho pathway signaling modulators as potential neuroprotectants.
Source
Department of Anatomy and Cell Biology, The Brody School of Medicine at East Carolina University, Greenville, NC 27834, United States.
Abstract
Many chemotherapy drugs are known to cause significant clinical neurotoxicity, which can result in the early cessation of treatment. To identify and develop more effective means of neuroprotection it is important to understand the toxicity of these drugs at the molecular and cellular levels. In the present study, we examine the effects of paclitaxel (taxol), cisplatin, and methotrexate on primary rat neurons including hippocampal, cortical, and dorsal horn/dorsal root ganglion neuronal cultures. We found that all of these anti-cancer drugs induce substantial neurotoxicity evidenced by neurite degeneration. The neurons are capable of recovering after treatment withdrawal, but taxol exerts a biphasic effect that results in the collapse of processes days after treatment is withdrawn. After cisplatin and methotrexate treatment, we observed the degeneration of neuronal processes including the reduction of dendritic branching, length, and altered growth cone formation, indicating an abnormal arrangement of the actin cytoskeleton consistent with the involvement of Rho family small GTPases. Inhibiting RhoA downstream effector p160 ROCK/Rho kinase using Y-27632, or activating p75 neurotrophin receptor (p75 NTR) using non-peptide mimetic LM11A-31, were able to reverse the degeneration caused by cisplatin and methotrexate. Therefore, the neurotoxicity resulting from exposure to the anti-cancer drugs cisplatin and methotrexate can be alleviated by inhibiting Rho signaling pathway.
Functional conservation of the glutamine-rich domains of yeast Gal11 and human SRC-1 in the transactivation of glucocorticoid receptor Tau 1 in Saccharomyces cerevisiae.
Source
Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, 300 Yongbong-dong, Buk-gu, Gwangju 500-757, South Korea.
Abstract
The yeast Gal11 protein, a component of the Mediator complex, is required for the transcriptional activation of many class II genes as a physiological target of various activator proteins in vivo. In this study, we identified the yeast (Saccharomyces cerevisiae) Mediator complex as a novel coactivator of the transcriptional activity of the glucocorticoid receptor (GR) tau 1 (tau1), the major transcriptional activation domain of the GR. GR tau1 directly interacted with the Mediator complex in vivo and in vitro in a Gal11 module-dependent manner, and the Gal11p subunit interacted directly with GR tau1. Specific amino acid residues within the glutamine-rich (Qr) domain of Gal11p (residues 116 to 277) were essential for its interaction with GR tau1 and GR tau1 transactivity in yeast, as demonstrated by mutational analysis of the Gal11 Qr domain, which is highly conserved among human steroid receptor coactivator (SRC) proteins. A Gal11p variant, mini-Gal11p, comprised of the Mediator association and Qr domains of Gal11p or chimeric mini-Gal11p containing the Qr domain of SRC-1 could potentiate the GR tau1 transactivity in a gal11Delta yeast strain. These results suggest that there is functional conservation between Qr domains of yeast Gal11p and mammalian SRC proteins as direct targets of activator proteins in yeast.
[Immunohistochemistry of degenerative changes in the central nervous system in spastic paraparesis associated to human T lymphotropic virus type I (HTLV-I)].
Source
Departamento de Ciencias Neurológicas, Facultad de Medicina, Universidad de Chile, Concepción, Chile. lcartier@med.uchile.cl
Abstract
BACKGROUND:
Human T lymphotropic virus type I is associated with tropical spastic paraparesis, that is a chronic and progressive disease which damages specially the cortiespinal tracts. The pathogenesis of this degenerative process remains unknown.
AIM:
To identify histopathological aspects that could suggest a pathogenic hypothesis we studied immunohistochemical features in spinal cords obtained from patients that died due to progressive spastic paraparesis.
PATIENTS AND METHODS:
Five males and five females, who died between 1990 and 2000, with a mean age of 52 years and mean disease duration of 8.6, were studied. All had a complete clinical and virological diagnosis. Samples were obtained from the frontal motor cortex and spinal cord (cervical, dorsal and lumbar segments), were fixed in formol (10%), included in paraffin, and stained with Haematoxylin and Luxol-fast-blue. Immunohistochemical study was made with anti-neurofilament antibodies 1:100 (M0762, DAKO), anti-APP 1:20 (Rabbit Pre Amyloid protein 51-2700 ZYMED), anti-tau 1:100 (A0024 DAKO) and anti-ubiquitine 1:50 (NCL UBIQm Novocastra).
RESULTS:
All cases had demyelinization and axonal loss in the cortico-spinal tracts; distal and segmental demyelinization of Goll tract; axonal thickening, amyloid precursor protein deposits in the white matter; tau protein aggregation in the spinal cord oligodendrocytes; axonal ubiquitination of sensitive and motor tracts, and subcortical white matter. Neurona! injury was absent.
CONCLUSIONS:
The systematic damage of motor and sensitive tracts of the spinal-cord and the absence of neurona! damage, defines a degenerative process limited to axons. This central axonopathie could be caused by a disturbance of axoplasmic transport.
Spatiotemporal patterns of postsynaptic density (PSD)-95 expression after rat spinal cord injury.
Source
The Jiangsu Province Key Laboratory of Neuroregeneration, Department of Microbiology and Immunology, Nantong University (Former Nantong Medical College), Nantong, China.
Abstract
AIMS:
Postsynaptic density (PSD)-95 is a scaffolding protein linking the N-methyl-D-aspartate receptor with neuronal nitric oxide synthase (nNOS), which contributes to many physiological and pathological actions. We here investigated whether PSD-95 was involved in the secondary response following spinal cord injury (SCI).
METHODS:
Spinal cord contusion (SCC) and spinal cord transection (SCT) models at thoracic (T) segment 9 (T(9)) were established in adults rats. Real-time polymerase chain reaction, Western blot, immunohistochemistry and immunofluorescence were used to detect the temporal profile and spatial distribution of PSD-95 after SCI. The association between PSD-95 and nNOS in the injured cords was also assessed by coimmmunoprecipation and double immunofluorescent staining.
RESULTS:
The mRNA and protein for PSD-95 expression were significantly increased at 2 h or 8 h, and then gradually declined to the baseline level, ultimately up-regulated again from 5 days to 7 days for its mRNA level and at 7 days or 14 days for its protein level after either SCC or SCT. PSD-95 immunoreactivity was found in neurones, oligodendrocytes and synaptic puncta of spinal cord tissues within 5 mm from the lesion site. Importantly, injury-induced expression of PSD-95 was colabelled by active caspase-3 (apoptotic marker), Tau-1 (the marker for pathological oligodendrocytes) and nNOS.
CONCLUSIONS:
Accompanied by the spatio-temporal changes for PSD-95 expression, the association between PSD-95 and nNOS undergoes substantial alteration after SCI. These two molecules are likely to form a complex on apoptotic neurones and pathological oligodendrocytes, which may in turn be involved in the secondary response after SCI.
Dehydroevodiamine attenuates calyculin A-induced tau hyperphosphorylation in rat brain slices.
Source
Department of Pathophysiology, Hubei Provincial Key Laboratory of Neurological Diseases, Huazhong University of Science and Technology, Wuhan 430030, China.
Abstract
AIM:
This study was to investigate the effect of dehydroevodiamine (DHED) on Alzheimer's disease (AD)-like tau hyperphosphorylation induced by calyculin A (CA), an inhibitor of protein phosphatase (PP)-2A and PP-1, and the involvement of PP-2A in metabolically competent rat brain slices.
METHODS:
Rat brain slices were pre-incubated at 33 degree centigrade in the presence (10, 100, and 200 micromol/L, respectively) or absence of DHED for 1 h. Then, CA 0.1 micromol/L was added and the slices were treated for another 2 h. Western blotting and/or immunohistochemistry were used to measure the phosphorylation level of tau and PP-2A.
RESULTS:
CA treatment could remarkably increase the immunoreactivity of pS262 and decrease the staining of Tau-1, representing tau hyperphosphorylation at Ser262 (pS262) and Ser198/ 199/202 (Tau-1, as the antibody reacts with unphosphorylated tau, therefore, decreased staining represents increased phosphorylation). Pre-incubation of the brain slices with DHED could efficiently attenuate the CA-induced tau hyperphosphorylation at the above AD-related sites. Additionally, DHED also decreased the basal phosphorylation level of tau at Ser396, although CA failed to induce tau hyperphosphorylation at this site. Furthermore, CA treatment induced an increased level of Tyr307-phosphorylated PP-2A, which represents inactivation of the phosphatase, whereas DHED arrested the elevation of the inhibitory modification of PP-2A.
CONCLUSION:
DHED can attenuate CA-induced tau hyperphosphorylation at multiple AD-related sites in metabolically active rat brain slices. The underlying mechanism may involve a decreased inhibitory phosphorylation of PP-2A at Tyr307.
VIP induces the elongation of dendrites and axons in cultured hippocampal neurons: role of microtubules.
Source
Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-University, D-79104 Freiburg, Germany. jost.leemhuis@pharmakol.uni-freiburg.de
Abstract
In neurons from rat hippocampus, VIP induces the elongation of dendrites. In the present study, we have investigated in cultured hippocampal neurons whether VIP changed the actin and tubulin cytoskeleton in dendrites. VIP caused the elongation of dendrites and induced the outgrowth of microtubules, so that they extended up to the tips. In contrast, VIP reduced the F-actin content measured as total pixel after phalloidin staining in dendritic tips. These results suggest that VIP causes dendrite elongation by facilitating the outgrowth of microtubules into the newly formed extensions.
Cryopreservation of granule cells from the postnatal rat hippocampus.
Source
Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan.
Abstract
Although primary cultures of neurons are essential methods for cell biological and pharmacological researches, many animals must be sacrificed for each experiment. Here we introduce a novel system to cryopreserve hippocampal granule cells (GCs) prepared from postnatal rats. Being thawed after as long as 60 days of cryopreservation, GCs expressed the mature neuronal marker MAP-2 and elongated single tau-1-positive axons and multiple tau-1-negative dendrites. These properties closely resembled intact GCs in primary cultures, providing the advantage of being able to repeatedly prepare stable cultures with a single sacrifice of animals.
GAP-43 gene expression regulates information storage.
Source
Department of Psychology and Neurobiology, Northwestern University Interdepartmental Neuroscience Program, Northwestern University, Evanston, Illinois 60208, USA. matthew_holahan@carleton.ca
Abstract
Previous reports have shown that overexpression of the growth- and plasticity-associated protein GAP-43 improves memory. However, the relation between the levels of this protein to memory enhancement remains unknown. Here, we studied this issue in transgenic mice (G-Phos) overexpressing native, chick GAP-43. These G-Phos mice could be divided at the behavioral level into "spatial bright" and "spatial dull" groups based on their performance on two hidden platform water maze tasks. G-Phos dull mice showed both acquisition and retention deficits on the fixed hidden platform task, but were able to learn a visible platform task. G-Phos bright mice showed memory enhancement relative to wild type on the more difficult movable hidden platform spatial memory task. In the hippocampus, the G-Phos dull group showed a 50% greater transgenic GAP-43 protein level and a twofold elevated transgenic GAP-43 mRNA level than that measured in the G-Phos bright group. Unexpectedly, the dull group also showed an 80% reduction in hippocampal Tau1 staining. The high levels of GAP-43 seen here leading to memory impairment find its histochemical and behavioral parallel in the observation of Rekart et al. (Neuroscience 126: 579-584) who described elevated levels of GAP-43 protein in the hippocampus of Alzheimer's patients. The present data suggest that moderate overexpression of a phosphorylatable plasticity-related protein can enhance memory, while excessive overexpression may produce a "neuroplasticity burden" leading to degenerative and hypertrophic events culminating in memory dysfunction.
Histone deacetylase inhibition-mediated differentiation of RGC-5 cells and interaction with survival.
Source
Department of Ophthalmology and Visual Sciences, University of Wisconsin Medical School, Madison, Wisconsin 53792, USA.
Abstract
PURPOSE:
The acetylation state of histones is modulated by histone deacetylase (HDAC) and histone acetyltransferase and is an important component in regulating gene transcription, including neuronal differentiation. The authors studied the relationship between histone acetylation and the differentiation and survival of the RGC-5 cell line and compared it with nontranscriptional-dependent differentiation with staurosporine.
METHODS:
The retinal ganglion cell line RGC-5 was treated with trichostatin A (TSA), other HDAC inhibitors, and staurosporine; differentiation, neuritogenesis, neurotrophic factor dependence, and dependence on RNA transcription were assessed.
RESULTS:
TSA caused significant differentiation and neuritogenesis. Differences between HDAC inhibition and staurosporine differentiation included the proportion of differentiated cells, cell viability, cell morphology, and transcriptional dependence. HDAC inhibition, but not staurosporine differentiation, resulted in RGC-5 cells that were neurotrophic factor dependent.
CONCLUSIONS:
These results implicate two different mechanisms for RGC-5 differentiation, with a common downstream effect on neurite outgrowth but a differential effect on neurotrophic factor dependence.
p53 is upregulated in Alzheimer's disease and induces tau phosphorylation in HEK293a cells.
Source
King's College London, MRC Centre for Neurodegenerative Research, Institute of Psychiatry, De Crespigny Park, Denmark Hill, London SE5 8AF, UK.
Abstract
p53 and tau are both associated with neurodegenerative disorders. Here, we show by Western blotting that p53 is upregulated approximately 2-fold in the superior temporal gyrus of Alzheimer's patients compared to healthy elderly control subjects. Moreover, p53 was found to induce phosphorylation of human 2N4R tau at the tau-1/AT8 epitope in HEK293a cells. Confocal microscopy revealed that tau and p53 were spatially separated intracellularly. Tau was found in the cytoskeletal compartment, whilst p53 was located in the nucleus, indicating that the effects of p53 on tau phosphorylation are indirect. Collectively, these findings have ramifications for neuronal death associated with Alzheimer's disease and other tauopathies.
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