[Efficacy and safety of ropinirole in the treatment of Parkinson's disease: a multi-center, randomized, double-blind and bromocriptine-controlled trial].

OBJECTIVE: To explore the efficacy and safety of ropinirole in the treatment of Parkinson's disease. METHODS: From November 2005 to April 2007, a total of 221 subjects from 7 hospitals of Beijing, Lanzhou and Wuhan participated in a 12-week multi-center, randomized, bromocriptine-controlled, double-blind, double-dummy and parallel-group trial. The efficacy of ropinirole was assessed with the unified Parkinson's disease rating scale (UPDRS) score, "off" time according to the patient's diary and the overall evolution of clinical efficacy. The safety was assessed on the basis of adverse events, blood pressure, pulse, laboratory measurement and electrocardiographic recordings. And the statistical analyses were performed with t, paired t, χ(2) and covariance tests. RESULTS: In the intent-to-treat population, the average UPDRSIII score decreased to (11 ± 9) in ropinirole group and (11 ± 10) in bromocriptine group while the UPDRSIIscore decreased to (4 ± 4) and (3 ± 5) respectively at Week 12 versus baseline. It showed that ropinirole was non-inferior to bromocriptine. The "off" time at Week 12 [(3.0 ± 1.2)h, (3.8 ± 1.6)h] versus baseline [(4.2 ± 2.0)h, (4.4 ± 1.7)h] decreased (t = 10.772, t = 5.746, P = 0.000) in ropinirole and bromocriptine groups. Ropinirole offered a better overall improvement rate (q = 7.241, P = 0.007). The adverse events occurring at a ratio of over 5% caused by ropinirole included orthostatic hypotension, nausea, dizziness, upper abdominal discomfort, insomnia and palpitation. No significant difference existed in the frequency of adverse events between two groups. CONCLUSIONS: Ropinirole is both effective and safe in the treatment of Chinese patients with Parkinson's disease.

Protection of synapses against Alzheimer's-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers.

Synapse deterioration underlying severe memory loss in early Alzheimer's disease (AD) is thought to be caused by soluble amyloid beta (Abeta) oligomers. Mechanistically, soluble Abeta oligomers, also referred to as Abeta-derived diffusible ligands (ADDLs), act as highly specific pathogenic ligands, binding to sites localized at particular synapses. This binding triggers oxidative stress, loss of synaptic spines, and ectopic redistribution of receptors critical to plasticity and memory. We report here the existence of a protective mechanism that naturally shields synapses against ADDL-induced deterioration. Synapse pathology was investigated in mature cultures of hippocampal neurons. Before spine loss, ADDLs caused major downregulation of plasma membrane insulin receptors (IRs), via a mechanism sensitive to calcium calmodulin-dependent kinase II (CaMKII) and casein kinase II (CK2) inhibition. Most significantly, this loss of surface IRs, and ADDL-induced oxidative stress and synaptic spine deterioration, could be completely prevented by insulin. At submaximal insulin doses, protection was potentiated by rosiglitazone, an insulin-sensitizing drug used to treat type 2 diabetes. The mechanism of insulin protection entailed a marked reduction in pathogenic ADDL binding. Surprisingly, insulin failed to block ADDL binding when IR tyrosine kinase activity was inhibited; in fact, a significant increase in binding was caused by IR inhibition. The protective role of insulin thus derives from IR signaling-dependent downregulation of ADDL binding sites rather than ligand competition. The finding that synapse vulnerability to ADDLs can be mitigated by insulin suggests that bolstering brain insulin signaling, which can decline with aging and diabetes, could have significant potential to slow or deter AD pathogenesis.

Inhibition of calcineurin-mediated endocytosis and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors prevents amyloid beta oligomer-induced synaptic disruption.

Synaptic degeneration, including impairment of synaptic plasticity and loss of synapses, is an important feature of Alzheimer disease pathogenesis. Increasing evidence suggests that these degenerative synaptic changes are associated with an accumulation of soluble oligomeric assemblies of amyloid beta (Abeta) known as ADDLs. In primary hippocampal cultures ADDLs bind to a subpopulation of neurons. However the molecular basis of this cell type-selective interaction is not understood. Here, using siRNA screening technology, we identified alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits and calcineurin as candidate genes potentially involved in ADDL-neuron interactions. Immunocolocalization experiments confirmed that ADDL binding occurs in dendritic spines that express surface AMPA receptors, particularly the calcium-impermeable type II AMPA receptor subunit (GluR2). Pharmacological removal of the surface AMPA receptors or inhibition of AMPA receptors with antagonists reduces ADDL binding. Furthermore, using co-immunoprecipitation and photoreactive amino acid cross-linking, we found that ADDLs interact preferentially with GluR2-containing complexes. We demonstrate that calcineurin mediates an endocytotic process that is responsible for the rapid internalization of bound ADDLs along with surface AMPA receptor subunits, which then both colocalize with cpg2, a molecule localized specifically at the postsynaptic endocytic zone of excitatory synapses that plays an important role in activity-dependent glutamate receptor endocytosis. Both AMPA receptor and calcineurin inhibitors prevent oligomer-induced surface AMPAR and spine loss. These results support a model of disease pathogenesis in which Abeta oligomers interact selectively with neurotransmission pathways at excitatory synapses, resulting in synaptic loss via facilitated endocytosis. Validation of this model in human disease would identify therapeutic targets for Alzheimer disease.

Anti-N-methyl-D-aspartate receptor encephalitis with serum anti-thyroid antibodies and IgM antibodies against Epstein-Barr virus viral capsid antigen: a case report and one year follow-up.

BACKGROUND: Anti-N-methyl-D-aspartate receptor encephalitis is an increasingly common autoimmune disorder mediated by antibodies to certain subunit of the N-methyl-D-aspartate receptor. Recent literatures have described anti-thyroid and infectious serology in this encephalitis but without follow-up. CASE PRESENTATION: A 17-year-old Chinese female patient presented with psychiatric symptoms, memory deficits, behavioral problems and seizures. She then progressed through unresponsiveness, dyskinesias, autonomic instability and central hypoventilation during treatment. Her conventional blood work on admission showed high titers of IgG antibodies to thyroglobulin, thyroid peroxidase and IgM antibodies to Epstein-Barr virus viral capsid antigen. An immature ovarian teratoma was found and removal of the tumor resulted in a full recovery. The final diagnosis of anti-N-methyl-D-aspartate receptor encephalitis was made by the identification of anti-N-methyl-D-aspartate receptor antibodies in her cerebral spinal fluid. Pathology studies of the teratoma revealed N-methyl-D-aspartate receptor subunit 1 positive ectopic immature nervous tissue and Epstein-Barr virus latent infection. She was discharged with symptoms free, but titers of anti-thyroid peroxidase and anti-thyroglobulin antibodies remained elevated. One year after discharge, her serum remained positive for anti-thyroid peroxidase and anti-N-methyl-D-aspartate receptor antibodies, but negative for anti-thyroglobulin antibodies and IgM against Epstein-Barr virus viral capsid antigen. CONCLUSIONS: Persistent high titers of anti-thyroid peroxidase antibodies from admission to discharge and until one year later in this patient may suggest a propensity to autoimmunity in anti- N-methyl-D-aspartate receptor encephalitis and support the idea that neuronal and thyroid autoimmunities represent a pathogenic spectrum. Enduring anti-N-methyl-D-aspartate receptor antibodies from admission to one year follow-up but seroreversion of Epstein-Barr virus viral capsid antigen IgM may raise the important issue of elucidating the triggers and boosters of anti- N-methyl-D-aspartate receptor encephalitis.

Insulin resistance and amyloidogenesis as common molecular foundation for type 2 diabetes and Alzheimer's disease.

Characterized as a peripheral metabolic disorder and a degenerative disease of the central nervous system respectively, it is now widely recognized that type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) share several common abnormalities including impaired glucose metabolism, increased oxidative stress, insulin resistance and amyloidogenesis. Several recent studies suggest that this is not an epiphenomenon, but rather these two diseases disrupt common molecular pathways and each disease compounds the progression of the other. For instance, in AD the accumulation of the amyloid-beta peptide (Abeta), which characterizes the disease and is thought to participate in the neurodegenerative process, may also induce neuronal insulin resistance. Conversely, disrupting normal glucose metabolism in transgenic animal models of AD that over-express the human amyloid precursor protein (hAPP) promotes amyloid-peptide aggregation and accelerates the disease progression. Studying these processes at a cellular level suggests that insulin resistance and Abeta aggregation may not only be the consequence of excitotoxicity, aberrant Ca(2+) signals, and proinflammatory cytokines such as TNF-alpha, but may also promote these pathological effectors. At the molecular level, insulin resistance and Abeta disrupt common signal transduction cascades including the insulin receptor family/PI3 kinase/Akt/GSK3 pathway. Thus both disease processes contribute to overlapping pathology, thereby compounding disease symptoms and progression.

Amyloid beta oligomers induce impairment of neuronal insulin receptors.

Recent studies have indicated an association between Alzheimer's disease (AD) and central nervous system (CNS) insulin resistance. However, the cellular mechanisms underlying the link between these two pathologies have not been elucidated. Here we show that signal transduction by neuronal insulin receptors (IR) is strikingly sensitive to disruption by soluble Abeta oligomers (also known as ADDLs). ADDLs are known to accumulate in AD brain and have recently been implicated as primary candidates for initiating deterioration of synapse function, composition, and structure. Using mature cultures of hippocampal neurons, a preferred model for studies of synaptic cell biology, we found that ADDLs caused a rapid and substantial loss of neuronal surface IRs specifically on dendrites bound by ADDLs. Removal of dendritic IRs was associated with increased receptor immunoreactivity in the cell body, indicating redistribution of the receptors. The neuronal response to insulin, measured by evoked IR tyrosine autophosphorylation, was greatly inhibited by ADDLs. Inhibition also was seen with added glutamate or potassium-induced depolarization. The effects on IR function were completely blocked by NMDA receptor antagonists, tetrodotoxin, and calcium chelator BAPTA-AM. Downstream from the IR, ADDLs induced a phosphorylation of Akt at serine473, a modification associated with neurodegenerative and insulin resistance diseases. These results identify novel factors that affect neuronal IR signaling and suggest that insulin resistance in AD brain is a response to ADDLs, which disrupt insulin signaling and may cause a brain-specific form of diabetes as part of an overall pathogenic impact on CNS synapses.

Increased glucose tolerance and reduced adiposity in the absence of fasting hypoglycemia in mice with liver-specific Gs alpha deficiency.

The G protein G(s)alpha is essential for hormone-stimulated cAMP generation and is an important metabolic regulator. We investigated the role of liver G(s)-signaling pathways by developing mice with liver-specific G(s)alpha deficiency (LGsKO mice). LGsKO mice had increased liver weight and glycogen content and reduced adiposity, whereas survival, body weight, food intake, and metabolic rates at ambient temperature were unaffected. LGsKO mice had increased glucose tolerance with both increased glucose-stimulated insulin secretion and increased insulin sensitivity in liver and muscle. Fed LGsKO mice were hypoglycemic and hypoinsulinemic, with low expression of hepatic gluconeogenic enzymes and PPARgamma coactivator-1. However, LGsKO mice maintained normal fasting glucose and insulin levels, probably due to prolonged breakdown of glycogen stores and possibly increased extrahepatic gluconeogenesis. Lipid metabolism was unaffected in fed LGsKO mice, but fasted LGsKO mice had increased lipogenic and reduced lipid oxidation gene expression in liver and increased serum triglyceride and FFA levels. LGsKO mice had very high serum glucagon and glucagon-like peptide-1 levels and pancreatic alpha cell hyperplasia, probably secondary to hepatic glucagon resistance and/or chronic hypoglycemia. Our results define novel roles for hepatic G(s)-signaling pathways in glucose and lipid regulation, which may prove useful in designing new therapeutic targets for diabetes and obesity.

A patient with Creutzfeldt-Jakob disease with an insertion of 7 octa-repeats in the PRNP gene: molecular characteristics and clinical features.

BACKGROUND: We evaluated the features of neuropathology, abnormal prion protein (PrP) molecules, and clinical data of a Chinese woman diagnosed with familiar Creutzfeldt-Jakob disease (CJD), having 7 octa-repeats inserted with codon 129 methionine homozygote in the PRNP gene. METHODS: Neuropathologic characteristics of the brain were analyzed by hemotoxylin-eosin stain and electronic microscopy. The presence of abnormal PrP in brains was detected by proteinase K and PrP molecules were evaluated by deglycosylation assay. RESULTS: Spongiform degeneration, with diffuse neuronal loss and mild astrocytic gliosis, as well as with profound degeneration of neurons and astrocytes was observed. Proteinase K-resistant PrP was deposited widely in various regions of the brain. Calculation of the glycosylation ratios of proteinase K-resistant PrP molecules identified that the monoglycosyl isomer was predominant. PrP deglycosylation tests allowed for the identification of a predominant 19-kDa PrP signal that represents a partially proteolytic C-terminal segment, a 27-kDa band that represents the full-length wild-type PrP molecule, and a 30-kDa band that probably corresponds to the full-length mutant PrP molecule. CONCLUSION: : Sporadic CJD-like neuropathologic changes and deposits of proteinase K-resistant PrP have been identified in this familiar CJD case with a 168 base pair nucleotide insertion. The clinical features differ from previously reported cases that had 7 octa-repeat insertion, but bear similarities to sporadic CJD.

Treatment of scrapie pathogen 263K with tetracycline partially abolishes protease-resistant activity in vitro and reduces infectivity in vivo.

OBJECTIVE: To study the possible effect of tetracycline on protease-resistant activity in vitro and infectivity in vivo of a scrapie strain 263K. METHODS: Scrapie pathogens were incubated with tetracycline at different concentrations for various periods of time and protease-resistant PrP signals were evaluated with proteinase K-treatment and Western blots. The preparations treated with tetracycline were intracerebrally inoculated into golden hamsters and typical TSE manifestations were noted. PrPSc in brain tissues of the infected animals was detected by PrP specific Western blot assays. RESULTS: Protease-resistant PrP was significantly reduced in or removed from the preparations treated with tetracycline in a dose-dependant manner. Compared with the control group after incubated for 53.75 +/- 0.50 days, the preparations treated with 5 mmol/L and 20 mmol/L tetracycline prolonged the incubation time of 61.5 +/- 1.73 and 59.5 +/- 0.58 days (P < 0.05). CONCLUSION: Treatment of scrapie pathogen 263K with tetracycline reduces or removes its protease-resistant activity in vitro.

Insulin and the insulin receptor in experimental models of learning and memory.

Insulin is best known for its action on peripheral insulin target tissues such as the adipocyte, muscle and liver to regulate glucose homeostasis. In the central nervous system (CNS), insulin and the insulin receptor are found in specific brain regions where they show evidence of participation in a variety of region-specific functions through mechanisms that are different from its direct glucose regulation in the periphery. While the insulin/insulin receptor associated with the hypothalamus plays important roles in regulation of the body energy homeostasis, the hippocampus- and cerebral cortex-distributed insulin/insulin receptor has been shown to be involved in brain cognitive functions. Emerging evidence has suggested that insulin signaling plays a role in synaptic plasticity by modulating activities of excitatory and inhibitory receptors such as glutamate and GABA receptors, and by triggering signal transduction cascades leading to alteration of gene expression that is required for long-term memory consolidation. Furthermore, deterioration of insulin receptor signaling appears to be associated with aging-related brain degeneration such as the Alzheimer's dementia and cognitive impairment in aged subjects suffering type 2 diabetes mellitus.

Disruption of neocortical histone H3 homeostasis by soluble Aß: implications for Alzheimer's disease.

Amyloid-ß peptide (Aß) fragment misfolding may play a crucial role in the progression of Alzheimer's disease (AD) pathophysiology as well as epigenetic mechanisms at the DNA and histone level. We hypothesized that histone H3 homeostasis is disrupted in association with the appearance of soluble Aß at an early stage in AD progression. We identified, localized, and compared histone H3 modifications in multiple model systems (neural-like SH-SY5Y, primary neurons, Tg2576 mice, and AD neocortex), and narrowed our focus to investigate 3 key motifs associated with regulating transcriptional activation and inhibition: acetylated lysine 14, phosphorylated serine 10 and dimethylated lysine 9. Our results in vitro and in vivo indicate that multimeric soluble Aß may be a potent signaling molecule indirectly modulating the transcriptional activity of DNA by modulating histone H3 homeostasis. These findings reveal potential loci of transcriptional disruption relevant to AD. Identifying genes that undergo significant epigenetic alterations in response to Aß could aid in the understanding of the pathogenesis of AD, as well as suggesting possible new treatment strategies.

High throughput monitoring of amyloid-ß(42) assembly into soluble oligomers achieved by sensitive conformation state-dependent immunoassays.

Accumulation of small soluble assemblies of amyloid-ß (Aß)(42) in the brain is thought to play a key role in the pathogenesis of Alzheimer's disease. As a result, there has been much interest in finding small molecules that inhibit the formation of synaptotoxic Aß(42) oligomers that necessitates sensitive methods for detecting the initial steps in the oligomerization of Aß(42). Modeling suggests that oligomerized Aß(42) adopts a conformation in which the C-terminus is embedded in the center, whereas the N-terminus is exposed at the periphery of the oligomer. Here we report that an inverse change in Aß(42) C-terminal and N-terminal epitope accessibility provides the basis of a sensitive method for assessing early steps in Aß(42) oligomerization. Using ELISA and AlphaLISA, we found that Aß(42) C-terminal immunoreactivity decreased in a time- and concentration-dependent manner under conditions favoring oligomerization. This reduction was accompanied by an increase in the N-terminal immunoreactivity, suggesting that assemblies with multiple exposed N-terminal epitopes were detected. Importantly the assay generates a robust window between monomers and oligomers at as low as 1 nM Aß(42). Using this assay, known oligomerization inhibitors produced a dose-dependent unmasking of the Aß(42) C-terminal epitope. After automation, the assay proved to be highly reproducible and effective for high throughput screening of small molecules that inhibit Aß(42) oligomerization.

Insulin receptor dysfunction impairs cellular clearance of neurotoxic oligomeric a{beta}.

Accumulation of amyloid beta (Abeta) oligomers in the brain is toxic to synapses and may play an important role in memory loss in Alzheimer disease. However, how these toxins are built up in the brain is not understood. In this study we investigate whether impairments of insulin and insulin-like growth factor-1 (IGF-1) receptors play a role in aggregation of Abeta. Using primary neuronal culture and immortal cell line models, we show that expression of normal insulin or IGF-1 receptors confers cells with abilities to reduce exogenously applied Abeta oligomers (also known as ADDLs) to monomers. In contrast, transfection of malfunctioning human insulin receptor mutants, identified originally from patient with insulin resistance syndrome, or inhibition of insulin and IGF-1 receptors via pharmacological reagents increases ADDL levels by exacerbating their aggregation. In healthy cells, activation of insulin and IGF-1 receptor reduces the extracellular ADDLs applied to cells via seemingly the insulin-degrading enzyme activity. Although insulin triggers ADDL internalization, IGF-1 appears to keep ADDLs on the cell surface. Nevertheless, both insulin and IGF-1 reduce ADDL binding, protect synapses from ADDL synaptotoxic effects, and prevent the ADDL-induced surface insulin receptor loss. Our results suggest that dysfunctions of brain insulin and IGF-1 receptors contribute to Abeta aggregation and subsequent synaptic loss.

[Studies on heredity rule of the first genealogy regarding fatal familial insomnia in Henan province].

OBJECTIVE: To investigate the epidemiological, genealogic characteristic, familial history of the families with fatal familial insomnia, its clinical and pathological features as well as the heredity rule of related genes. METHODS: 135 familial members of 7 eras were studied. Vein blood samples from patients as well as from some familial members were collected. PRNP gene was studied with PCR, its serial was determined and then authenticated with Nsp I . Brain tissue was obtained for neuropathological test and PrP(Sc) test with Western blot method. RESULTS: Clinical symptoms of the 2 diagnosed cases were typical. 11 familial members died of similar neural disease. 32 samples of their familial members, codon at D178N of PRNP of 11 members was mutated, with mutation rate as 34.38% while D129N showed as methionine. Brain tissue of both probands denaturalized into spongiform and the nerve fiber was absent but PrP(Sc) protein was identified. CONCLUSION: Genealogy was described in the family with fatal familial insomnia since the patients had typical clinical symptoms and pathological characteristics. It seemed necessary to confirm cases of fatal familial insomnia and their genealogy with epidemiological data and to investigate its gene characteristics as well as with neuropathological and Western blot tests.

Expression of annexin A2 in GABAergic interneurons in the normal rat brain.

Expression of the Ca(2+)-dependent phospholipids binding protein annexin A2 (ANX2) in the brain is thought to be largely associated with brain pathological conditions such as tumor, inflammation, and neurodegeneration. The recent findings that ANX2 heterotetramer is involved in learning and neuronal activities necessitates a systematic investigation of the physiological expression of ANX2 in the brain. With combination of in situ hybridization and immunohistochemistry, ANX2 mRNA and protein were specifically detected in a group of GABAergic interneurons throughout the brain. Although ANX2 was absent from the interior of pyramidal neurons, it was found on the membrane and seemly the extracellular space of those neurons, where they closely co-localized with glutamate decarboxylase terminals. In cultured developing neurons, ANX2 was present at high concentrations in the growth cones co-distributing with several growth-associated proteins such as growth associated protein 43 (GAP43), turned on after division/Ulip/CRMP (TUC-4), tubulin, and tissue-plasminogen activator. It then became predominantly distributed on the membrane and mostly in axonal branches as neurons grew and extended synaptic networks. ANX2 was also secreted from cultured neurons, in a membrane-bound form that was Ca(2+)-dependent, which was significantly increased by neuronal depolarization. These results may have implications in the function and regulatory mechanism of ANX2 in the normal brain.

Wernicke's encephalopathy in nonalcoholic patients: clinical and pathologic features of three cases and literature reviewed.

Three cases of Wernicke's encephalopathy in nonalcoholic patients diagnosed by postmortem examination were reported to improve the recognition of this disease. All three cases were male, ages ranged from 33 to 73 years old. All the cases had a clinical history of malnutrition but no history of chronic alcoholism. Routine autopsy and neuropathologic investigations examining the histological changes of the brain were performed. Pathological findings included recent petechial and local hemorrhages in the mamillary bodies, periventricular regions around the third and fourth ventricles and aqueduct. Under light microscopy the proliferation and dilatation of the capillaries was particularly prominent in the mamillary bodies and pericapillary hemorrhages were present in the periventricular regions. Neuronal losses were found only in the medial nucleus of the thalamus and inferior olive, myelin staining demonstrated demyelination and gliosis in those areas. The diagnosis of Wernicke's encephalopathy was made. In combination with the reviewed literature, our cases suggest that Wernicke's encephalopathy can occur not only in patients with alcohol abuse, but also in those who have suffered thiamine deficiency due to metabolic and nutritional disorders.

Insulin receptor signaling in long-term memory consolidation following spatial learning.

Evidence has shown that the insulin and insulin receptor (IR) play a role in cognitive function. However, the detailed mechanisms underlying insulin's action on learning and memory are not yet understood. Here we investigated changes in long-term memory-associated expression of the IR and downstream molecules in the rat hippocampus. After long-term memory consolidation following a water maze learning experience, gene expression of IR showed an up-regulation in the CA1, but a down-regulation in the CA3 region. These were correlated with a significant reduction in hippocampal IR protein levels. Learning-specific increases in levels of downstream molecules such as IRS-1 and Akt were detected in the synaptic membrane accompanied by decreases in Akt phosphorylation. Translocation of Shc protein to the synaptic membrane and activation of Erk1/2 were also observed after long-term memory formation. Despite the clear memory-correlated alterations in IR signaling pathways, insulin deficits in experimental diabetes mellitus (DM) rats induced by intraperitoneal injections of streptozotocin resulted in only minor memory impairments. This may be due to higher glucose levels in the DM brain, and to compensatory mechanisms from other signaling pathways such as the insulin-like growth factor-1 receptor (IGF-1R) system. Our results suggest that insulin/IR signaling plays a modulatory role in learning and memory processing, which may be compensated for by alternative pathways in the brain when an insulin deficit occurs.

Impairment of phosphatase 2A contributes to the prolonged MAP kinase phosphorylation in Alzheimer's disease fibroblasts.

The serine/threonine phosphatase 2A (PP2A) has been implicated in the pathogenesis of Alzheimer's disease (AD) due to its important role in regulating dephosphorylation of the microtubule-associated protein tau and mitogen-activated protein (MAP) kinase. In the present study, we show that PP2A was responsible for dephosphorylation of the extracellular signal-regulated kinase 1/2 (Erk1/2) following its activation by BK stimulation. Abnormal gene and protein expressions of PP2A, as well as its activity, were found to contribute to the abnormally prolonged Erk1/2 phosphorylation in the AD fibroblasts. Inhibition of PP2A with okadiac acid produced enhanced and more lasting Erk1/2 phosphorylation after BK stimulation, whereas FK506, an inhibitor of PP2B and FK-binding protein, inhibited the BK-stimulated Erk1/2 phosphorylation. Furthermore, while the phosphorylated Erk1/2 was concentrated in the nucleus of AC cells, it was mainly distributed in the extranuclear compartments of AD cells. These results suggest that the delayed dephosphorylation of Erk1/2 in AD cells following its BK-stimulated activation may be due to deficits of PP2A activity and impaired nuclear translocation of phosphorylated Erk1/2.

Specific localization of the annexin II heterotetramer in brain lipid raft fractions and its changes in spatial learning.

Annexin-II (AII) is a Ca(2+)-dependent phospholipid-binding protein that is present in both intracellular and extracellular compartments. In the present study AII immunoreactivity was found in a subpopulation of neurons in specific brain regions, including the cerebral cortex and the surface of hippocampal pyramidal neurons from adult rats. AII from synaptic membranes was detected by immunoblotting as multiple species containing the monomer (AII36) and heterotetramer (AIIt). AIIt was resistant to beta-mercaptoethanol and dithiothreitol in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but was completely reduced to monomers (36 kDa) by two-dimensional electrophoresis. AIIt resided exclusively in the detergent-resistant lipid rafts concentrated in neuronal dendrites, and its recruitment to those structures was enhanced by antibody cross-link. AII abundantly distributed on the outer leaflet of neuronal membranes and between spaces of neurons appeared to be neuronal adhesive. The formation of AIIt required synthesis of sphingolipids and cholesterol, and its stability depended on Ca2+. Increases in neuronal activities such as depolarization and learning were shown to promote formation of AIIt. Our results suggest that, via a dynamic association with dendritic lipid rafts, AII may play a role in synaptic signal transduction and remodeling. This probably involves focal adhesion and interactions with actin that are associated with brain development and memory consolidation.

c-Src protein tyrosine kinase activity is required for muscarinic receptor-mediated DNA synthesis and neurogenesis via ERK1/2 and c-AMP-responsive element-binding protein signaling in neural precursor cells.

The G protein-coupled muscarinic acetylcholine receptor (mAChR) isoforms have been identified in neural stem/progenitor (or precursor) cells. In previous studies, activation of these receptors induced elevations in intracellular Ca(2+) signals and mitogen-activated protein (MAP) kinase activity that led to enhanced DNA synthesis along with neurogenesis in neural precursor cells. Here we report that the nonreceptor protein tyrosine kinase c-src activity is required for the muscarinic receptor-activated MAP kinase and cAMP-responsive element-binding protein (CREB). Stimulation of neural precursor cells dissociated from embryonic day 13 rat cortical neuroepithelium with the muscarinic receptor agonist carbachol (CCh) induced phosphorylations of c-src that were detected by antibodies raised against phospho-Tyr416 (Ptyr416), phospho-Tyr527 (Ptyr527), and phospho-Tyr215 (Ptyr215) of the kinase. Although an increase in Ptyr416 suggested direct activation of c-src, Ptyr215 may serve as an alternative mechanism underlying activation of c-src without dephosphorylation of Ptyr-527. Both extracellular signal-regulated kinase (Erk1/2) and CREB were significantly activated after CCh treatment indicated by increases in phosphorylation of these two proteins. The c-Src inhibitor PP1 abolished the CCh-induced activation of Erk1/2 and CREB in a dose-dependent manner. Moreover, CCh stimulated expression of the neuronal specific marker MAP2, which was inhibited by PP1. Cell proliferation assays and immunocytochemistry revealed that PP1 inhibited the CCh-induced DNA synthesis and MAP2(+) production. These results suggest that c-src activity is essential for the muscarinic receptor-mediated proliferation and neurogenesis in neural precursor cells via Erk1/2 and CREB signaling pathways.