Alzheimer-associated neuronal thread protein-induced apoptosis and impaired mitochondrial function in human central nervous system-derived neuronal cells

Is liquid biopsy mature enough for the diagnosis of Alzheimer's disease?

The preclinical diagnosis and clinical practice for Alzheimer's disease (AD) based on liquid biopsy have made great progress in recent years. As liquid biopsy is a fast, low-cost, and easy way to get the phase of AD, continual efforts from intense multidisciplinary studies have been made to move the research tools to routine clinical diagnostics. On one hand, technological breakthroughs have brought new detection methods to the outputs of liquid biopsy to stratify AD cases, resulting in higher accuracy and efficiency of diagnosis. On the other hand, diversiform biofluid biomarkers derived from cerebrospinal fluid (CSF), blood, urine, Saliva, and exosome were screened out and biologically verified. As a result, more detailed knowledge about the molecular pathogenesis of AD was discovered and elucidated. However, to date, how to weigh the reports derived from liquid biopsy for preclinical AD diagnosis is an ongoing question. In this review, we briefly introduce liquid biopsy and the role it plays in research and clinical practice. Then, we summarize the established fluid-based assays of the current state for AD diagnostic such as ELISA, single-molecule array (Simoa), Immunoprecipitation-Mass Spectrometry (IP-MS), liquid chromatography-MS, immunomagnetic reduction (IMR), multimer detection system (MDS). In addition, we give an updated list of fluid biomarkers in the AD research field. Lastly, the current outstanding challenges and the feasibility to use a stand-alone biomarker in the joint diagnostic strategy are discussed.

Urinary AD7c-NTP Evaluates Cognition Impairment and Differentially Diagnoses AD and MCI

The AD7c-NTP is a promising biomarker for AD diagnosis. However, the exact urinary AD7c-NTP concentration to differentiate AD from the mild cognitive impairment (MCI) remains inconclusive. We enrolled 98 and 90 clinical defined AD and MCI patients, respectively, and access their cognition impairment with Neuropsychiatric Inventory (NPI) and Mental State Examination (MMSE) along with their urinary AD7c-NTP. We demonstrated that urinary AD7c-NTP level in sequence from high to low was AD, MCI, and healthy groups (P < .01), and the AD7c-NTP was positively and negatively correlated with the NPI and MMSE scores, respectively. Additionally, AD7c-NTP well-matched NPI subscale scores, including agitation, depression, and apathy (P < .05). Importantly, the optimal cut-off AD7c-NTP level to distinguish the AD and MCI was .94 ng/mL (sensitivity 85.71% & specificity 73.91%). Conclusively, urinary AD7c-NTP could be used for cognition impairment evaluation and differentiated diagnosis of AD and MCI.

Alzheimer-Associated Neuronal Thread Protein: Research Course and Prospects for the Future

Alzheimer's disease (AD) is the leading cause of dementia. With aging societies, the prevalence of AD is increasing dramatically worldwide. The onset of AD is often not identified, and currently no available treatments are capable of stopping the disease process and its effect on cognitive decline. Thus, well-validated biomarkers of the preclinical stages of AD are needed. Alzheimer-associated neuronal thread protein (AD7c-NTP) is a member of the neuronal thread protein family and has a molecular weight of approximately 41 kD. AD7c-NTP has been identified as a biomarker for its specifically elevated levels in putative brain domains, cerebrospinal fluid (CSF), and the urine of AD and mild cognitive impairment (MCI) patients. Since the urine test is non-invasive, easy to perform, and patients accept it more easily than other methods, the urinary AD7c-NTP concentration has been recommended as a practical diagnostic tool for diagnosing AD and MCI. AD7c-NTP has undergone nearly 25 years of research course from its initial discovery to pathological verification, multi-center clinical evaluation, improvement of detection methods, epidemiological investigation, and combined application with other biomarkers. However, as a fluid biomarker, AD7c-NTP can be detected in urine instead of the traditional biomarker sources-CSF or blood, which has made the use of AD7c-NTP as a biomarker controversial. In this article, we review the research course of AD7c-NTP and suggest directions for future research.

AD7c-NTP Impairs Adult Striatal Neurogenesis by Affecting the Biological Function of MeCP2 in APP/PSl Transgenic Mouse Model of Alzheimer's Disease

The processes by which neural stem cells (NSCs) and neural precursor cells (NPCs) transform into the characteristic lineages observed in Alzheimer's disease (AD) are poorly characterized. Understanding these processes is of critical importance due to the increased prevalence of AD and the lack of effective AD strategies. Here, we used immunohistochemistry and Western blot to find out if MeCP2 was phosphorylated at a specific amino acid residue, Serine 421 (S421), and activated in response to AD-induced damage in amyloid precursor protein (APP)/PSl transgenic mice, altering its nuclear to cytoplasmic shuttling. Epigenetic examinations combined with chromatin immunoprecipitation and methylated DNA immunoprecipitation revealed that the translocation of MeCP2 from the nucleus to cytoplasm led to the loss of lineage-specific gene promoters (such as Gfap, Nestin, and Dcx), decreased transcriptional repression, and the activation of gene expression. Immunofluorescence data demonstrated that neurogenic progenitors with high levels of active phosphorylated MeCP2 at S421 (MeCP2 pS421) possessed a high probability of development into doublecortin (DCX)-expressing cells. AD7c-NTP will control neurogenic progenitor regeneration through its effects on MeCP2 pS421, leading to altered lineage-specific gene expression. This adds to the growing list of biological effects of AD7c-NTP in the brain and highlights MeCP2 as relevant to the plasticity of neural cells in the AD mice striatum.

Interaction of opioid with insulin/IGFs signaling in Alzheimer's disease

Alzheimer's disease is associated with biochemical and histopathological changes characterized by molecular abnormalities. Due to the lack of effective treatments for Alzheimer's disease, many attempts have been made to find potential therapies to reduce or even return neuronal loss after disease initiation. Alzheimer's disease is also touted as type III diabetes, showing an association with insulin signaling. The large distribution of the insulin receptor on the cell surface and its regulatory role in the central nervous system suggests that the pathogenesis of Alzheimer's disease could be ascribed to insulin signaling. The interference of opioids, such as morphine with insulin signaling pathways, is thought to occur via direct crosstalk between the signaling pathways of the insulin receptor and the mu-opioid receptor. In this review article, we discuss the possible crosstalk between the mu-opioid receptor and insulin signaling pathways. The association of these two signaling pathways with Alzheimer's disease is also debated.

Oxidative Damage in Human Periodontal Ligament Fibroblast (hPLF) after Methylmercury Exposure

Human exposure to mercury (Hg) is primary associated with its organic form, methylmercury (MeHg), through the ingestion of contaminated seafood. However, Hg contamination is also positively correlated with the number of dental restorations, total surface of amalgam, and organic mercury concentration in the saliva. Among the cells existing in the oral cavity, human periodontal ligament fibroblast (hPLF) cells are important cells responsible for the production of matrix and extracellular collagen, besides sustentation, renewal, repair, and tissue regeneration. In this way, the present study is aimed at investigating the potential oxidative effects caused by MeHg on hPLF. Firstly, we analyzed the cytotoxic effects of MeHg (general metabolism status, cell viability, and mercury accumulation) followed by the parameters related to oxidative stress (total antioxidant capacity, GSH levels, and DNA damage). Our results demonstrated that MeHg toxicity increased in accordance with the rise of MeHg concentration in the exposure solutions (1-7 μM) causing 100% of cell death at 7 μM MeHg exposure. The general metabolism status was firstly affected by 2 μM MeHg exposure (43.8 ± 1.7%), while a significant decrease of cell viability has arisen significantly only at 3 μM MeHg exposure (68.7 ± 1.4%). The ratio among these two analyses (named fold change) demonstrated viable hPLF with compromised cellular machinery along with the range of MeHg exposure. Subsequently, two distinct MeHg concentrations (0.3 and 3 μM) were chosen based on LC50 value (4.2 μM). hPLF exposed to these two MeHg concentrations showed an intracellular Hg accumulation as a linear-type saturation curve indicating that metal accumulated diffusively in the cells, typical for metal organic forms such as methyl. The levels of total GSH decreased 50% at exposure to 3 μM MeHg when compared to control. Finally, no alteration in the DNA integrity was observed at 0.3 μM MeHg exposure, but 3 μM MeHg caused significant damage. In conclusion, it was observed that MeHg exposure affected the general metabolism status of hPLF with no necessary decrease on the cell death. Additionally, although the oxidative imbalance in the hPLF was confirmed only at 3 μM MeHg through the increase of total GSH level and DNA damage, the lower concentration of MeHg used (0.3 μM) requires attention since the intracellular mercury accumulation may be toxic at chronic exposures.

The association between urinary Alzheimer-associated neuronal thread protein and cognitive impairment in late-life depression: a controlled pilot study

Accumulation of tau protein is associated with both Alzheimer's disease (AD) and late-life depression (LLD). Alzheimer-associated neuronal thread protein (AD7c-NTP), which is closely linked with the tau protein, is elevated in the cerebrospinal fluid and urine of AD patients. This study examined the association between urinary AD7c-NTP and late-life depression with cognitive impairment. One hundred and thirty-eight subjects were recruited into late-life depression with cognitive impairment (LLD-CI, n=52), late-life depression without cognitive impairment (LLD-NCI, n=29), AD (n=27), and healthy control (HC, n=30) groups. The level of urinary AD7c-NTP was measured using the enzyme-linked immunosorbent assay method. The Montreal Cognitive Assessment scale (MoCA), Hamilton Rating Scale for Depression (HRSD) and Hamilton Anxiety Rating Scale (HAMA) were used to assess cognitive functions and depressive and anxiety symptoms in the AD and LLD groups. Urinary levels of AD7c-NTP in the LLD-CI group (1.0±0.7ng/ml) were significantly higher than both the LLD-NCI (0.5±0.3ng/ml) and HC groups (0.5±0.3ng/ml), but lower than in the AD group (1.6±1.7 ng/ml). No significant associations were found in the level of urinary AD7c-NTP in relation to age, gender, education and MoCA in the LLD-CI group. The level of urinary AD7c-NTP appears to be associated with cognitive impairment in late-life depression and may be a potential biomarker for early identification of cognitive impairment in LLD.

Urine AD7c-NTP Predicts Amyloid Deposition and Symptom of Agitation in Patients with Alzheimer's Disease and Mild Cognitive Impairment

Background:

Expression of neuronal thread protein (NTP), which is considered to be related to neuritic sprouting and neuronal death, may be elevated in brain tissue, cerebrospinal fluid, and even urine in patients with Alzheimer’s disease (AD).

Objective:

In this study, we analyzed the correlation between urine AD-associated NTP (AD7c-NTP) level, and amyloid-β (Aβ) deposition, and clinical symptoms in AD and mild cognitive impairment (MCI).

Methods:

Twenty-two patients with mild to moderate AD and 8 subjects with MCI were recruited. Aβ deposition was measured with [¹¹C]-labeled Pittsburgh compound B (PiB)-positron emission tomography (PET) in all participants. Urine AD7c-NTP levels were measured using enzyme-linked immunosorbent assay. Mini-Mental State Examination (MMSE) and Neuropsychiatric Inventory (NPI) were used to evaluate cognitive function and behavioral psychological symptoms, respectively.

Results:

Fourteen (63.6%) of AD patients and 2 (25.0%) of MCI subjects were Aβ positive on PiB-PET. There was a significant difference in urine AD7c-NTP level between Aβ positive (2.27±2.22 ng/ml) and negative (0.55±0.60 ng/ml) subjects (p = 0.018). Using 1.46 ng/ml as a cut-off value, 68.8% of Aβ positive subjects showed elevated urine AD7c-NTP level, and 92.9% of Aβ negative subjects showed normal urine AD7c-NTP level. There were no relationships between urine AD7c-NTP level and MMSE and total NPI scores. However, AD7c-NTP level positively correlated with agitation score on NPI.

Conclusions:

Urine AD7c-NTP had high specificity and moderate sensitivity in predicting Aβ deposition among patients with cognitive impairment. Furthermore, urine AD7c-NTP level strongly correlated with the symptom of agitation.

A literature review of AD7c-ntp as a biomarker for Alzheimer's disease

The cornerstone of diagnosis of Alzheimer's disease (AD) is still the clinical criteria for probable and possible AD established by the NINCDS-ADRDA Work Group in 1984, which had survived for over 27 years. However, with the increase in people's knowledge of clinical manifestations and biology of AD, this standard is gradually proving to be insufficient; the early diagnosis of AD is thus particularly important. Therefore, in 2011, the National Institute on Aging and the Alzheimer's Association revised the criteria and integrated biomarker evidence into it. Biomarker evidence is expected to enhance the pathophysiological specificity of the diagnosis of AD. According to Consensus Report of the Working Group on Molecular and Biochemical Markers of Alzheimer's Disease, a qualified biomarker for AD should have the following abilities: It should detect a fundamental feature of neuropathology and be validated in neuropathologically confirmed cases, reliably with an sensitivity >80% for detecting AD and a specificity >80% for distinguishing other dementias; be reproducible and non-invasive; and be simple to perform and inexpensive. Alzheimer-associated neuronal thread protein (AD7c-NTP) is a member of “neuronal thread proteins” (NTPs); it can be detected in increased concentration in cortical neurons, brain-tissue extracts, cerebrospinal fluid, and urine in the early course of AD neurodegeneration, and it level is proportional to the degree of dementia, which makes it a promising biomarker for AD. In this review, we have evaluated the feasibility of developing AD7c-NTP as a biomarker for AD.

Opioid system and Alzheimer's disease

The opioid system may be involved in the pathogenesis of AD, including cognitive impairment, hyperphosphorylated tau, Aβ production, and neuroinflammation. Opioid receptors influence the regulation of neurotransmitters such as acetylcholine, norepinephrine, GABA, glutamate, and serotonin which have been implicated in the pathogenesis of AD. Opioid system has a close relation with Aβ generation since dysfunction of opioid receptors retards the endocytosis and degradation of BACE1 and γ-secretase and upregulates BACE1 and γ-secretase, and subsequently, the production of Aβ. Conversely, activation of opioid receptors increases the endocytosis of BACE1 and γ-secretase and downregulates BACE1 and γ-secretase, limiting the production of Aβ. The dysfunction of opioid system (opioid receptors and opioid peptides) may contribute to hyperphosphorylation of tau and neuroinflammation, and accounts for the degeneration of cholinergic neurons and cognitive impairment. Thus, the opioid system is potentially related to AD pathology and may be a very attractive drug target for novel pharmacotherapies of AD.

Differences in abundances of cell-signalling proteins in blood reveal novel biomarkers for early detection of clinical Alzheimer's disease

BACKGROUND

In November 2007 a study published in Nature Medicine proposed a simple test based on the abundance of 18 proteins in blood to predict the onset of clinical symptoms of Alzheimer's Disease (AD) two to six years before these symptoms manifest. Later, another study, published in PLoS ONE, showed that only five proteins (IL-1, IL-3, EGF, TNF- and G-CSF) have overall better prediction accuracy. These classifiers are based on the abundance of 120 proteins. Such values were standardised by a Z-score transformation, which means that their values are relative to the average of all others.

METHODOLOGY

The original datasets from the Nature Medicine paper are further studied using methods from combinatorial optimisation and Information Theory. We expand the original dataset by also including all pair-wise differences of z-score values of the original dataset ("metafeatures"). Using an exact algorithm to solve the resulting Feature Set problem, used to tackle the feature selection problem, we found signatures that contain either only features, metafeatures or both, and evaluated their predictive performance on the independent test set.

CONCLUSIONS

It was possible to show that a specific pattern of cell signalling imbalance in blood plasma has valuable information to distinguish between NDC and AD samples. The obtained signatures were able to predict AD in patients that already had a Mild Cognitive Impairment (MCI) with up to 84% of sensitivity, while maintaining also a strong prediction accuracy of 90% on a independent dataset with Non Demented Controls (NDC) and AD samples. The novel biomarkers uncovered with this method now confirms ANG-2, IL-11, PDGF-BB, CCL15/MIP-1; and supports the joint measurement of other signalling proteins not previously discussed: GM-CSF, NT-3, IGFBP-2 and VEGF-B.

Urine neural thread protein measurements in Alzheimer disease

OBJECTIVES

Neural thread protein (NTP), a membrane-associated phosphoprotein, was selectively elevated in the urine of patients with Alzheimer disease (AD). To demonstrate the potential utility of urine NTP assays for the diagnosis of AD, we performed this study.

DESIGN

A prospective blinded multicentered study.

PARTICIPANTS

Individuals diagnosed as having probable AD (n = 49), Parkinson's disease (PD) (n = 20), and healthy controls (n = 22) were enrolled consecutively in 4 neurology centers.

MEASUREMENTS

A first morning urine sample was obtained from each subject. Urine NTP measurement using competitive ELISA was tested at the central laboratory and compared with AD and PD patients and healthy controls (HC). The testing laboratory was blinded to clinical information.

RESULTS

The mean assay value in AD (n = 49, 26.8 ± 9.4 μg/mL) was significantly higher than in HC (n = 22, 18.1 ± 6.7 μg/mL) (P ≤ .001) and than in PD (n = 20, 21.0 ± 8.5 μg/mL) (P ≤ .05). Levels of 21.6 μg/mL or higher were found in 81.6% of all AD cases, in 30.0% of PD cases, and in 13.6% of HC. Urine NTP assay measurements of AD with a Clinical Dementia Rate (CDR) of 0.5 (n = 10, 24.2 ± 5.9 μg/mL, P = .063) or of 1.0 (n = 24, 30.1 ± 10.9 μg/mL, P = .000) were significantly higher than in HC. However, the AD patients with CDR of 2.0 (n = 9, 23.1 ± 7.3 μg/mL, P = .136) were not significant.

CONCLUSION

Urine NTP could be used as a safe and promising biochemical marker of early AD.

Practical utility of urinary assay in the diagnosis of Alzheimer's disease: AlzheimAlert

Urinary assay (Alzheimer's disease reaction titer [ADRT]) adds significant information in the diagnosis of Alzheimer's disease (AD), particularly for the nonspecialist. Clinical studies of ADRT in series of AD and non-AD patients have found sensitivity of 89-92.3%, specificity of 90-96.8%, positive predictive value (PPV) of 94.8-97.4% and negative predictive value (NPV) of 78.9-91.8%. The added information from the improvements of PPV and NPV are particularly helpful for the nonspecialist in the community. As a laboratory assay that requires a first-morning noncontaminated sample, ADRT is noninvasive, convenient and safe. ADRT is based on reagents derived from human AD brain cDNA. The pathophysiological roles of these genetic fragments and reagents are still under investigation. ADRT should have a positive impact on primary-care AD clinical practice.

Competitive ELISA studies of neural thread protein in urine in Alzheimer's disease

A specific and reliable competitive affinity assay kit has been developed to quantitatively measure neural thread protein (NTP) in first morning urine samples. This assay, called the urine neural thread protein test (UNTP), is a competitive enzyme-linked immunosorbent assay (ELISA) format affinity assay using 32-well microtiter plates. The assay detects UNTP in the 10-60 microg/mL range (an improvement over earlier assays of 10(3) x ), is linear and more reproducible (average coefficient of variation [CV] 6.2% in precision studies). The utility of the assay has been demonstrated in urine samples from patients with Alzheimer's disease (AD) and controls (sensitivity of 90% and specificity of 91%). Test-retest assays of subjects with AD and controls were comparatively stable at intervals of 2 days to 4.5 years, which suggests that positive (elevated) or negative (normal) NTP levels do not fluctuate significantly over time with respect to the cutoff.

Does the AD7c-NTP locus encode a protein?

AD7c-NTP, the only known protein entirely encoded by tandem and nested cassettes of Alu repetitive elements, is reportedly over-expressed in brains of Alzheimer's disease patients [de la Monte et al., J. Clin. Invest. 15 (1997)]. Based on these findings a commercial diagnostic assay ("7c Gold"/"AlzheimAlert" ) has been developed. We analyzed the published cDNA sequence and compared it to corresponding EST clones as well as the genomic sequences of human and chimpanzee. We come to the conclusion that the existence of the gene and in particular the predicted protein is inconsistent with EST and genomic data. Previously published data need to be reassessed.

Cloning and identification of a novel human gene PDLIM5, a homolog of AD-associated neuronal thread protein (AD7c-NTP)

A novel human gene cDNA was successfully cloned from the human fetal brain cDNA library constructed by our lab, and this gene was termed PDLIM5 after acquiring the agreement of HUGO. BLASTX searching revealed that the hypothetical protein is a homolog of AD-associated neuronal thread protein (AD7c-NTP), which is over-expressed in Alzheimer disease (AD) beginning early in the course of disease, and over-expression of the AD7c-NTP gene would cause neuritic sprouting and cell death. SMART analysis showed that both our predicted protein and AD7c-NTP comprise BCL domain (only contains BH1 and BH2 regions). RT-PCR experiment revealed that the expression level of PDLIM5 in brain, skeletal muscle, prostate, colon and leukocyte is obviously higher than that in other tissues.

Dietary lipids in the aetiology of Alzheimer's disease: implications for therapy

Amyloid plaques and neurofibrillary tangles are the neuropathological hallmarks of Alzheimer's disease (AD), but no conclusive evidence has emerged showing that these hallmarks are the cause and not a product of the disease. Many studies have implicated oxidation and inflammation in the AD process, and there is growing evidence that abnormalities of lipid metabolism also play a role. Using epidemiology to elucidate risk factors and histological changes to suggest possible mechanisms, the hypothesis is advanced that dietary lipids are the principal risk factor for the development of late-onset sporadic AD. The degree of saturation of fatty acids and the position of the first double bond in essential fatty acids are the most critical factors determining the effect of dietary fats on the risk of AD, with unsaturated fats and n-3 double bonds conferring protection and an overabundance of saturated fats or n-6 double bonds increasing the risk. The interaction of dietary lipids and apolipoprotein E isoforms may determine the risk and rate of sustained autoperoxidation within cellular membranes and the efficacy of membrane repair. Interventions involving dietary lipids and lipid metabolism show great promise in slowing or possibly averting the development of AD, including dietary changes, cholesterol-modifying agents and antioxidants.

Association of phosphorylation site of tau protein with neuronal apoptosis in Alzheimer's disease

In addition to neuritic changes and amyloid deposits, neuronal and glial cell apoptosis is an important pathological feature of Alzheimer's disease (AD). Several factors have been postulated as causes or triggers of cellular apoptotic change. This study focused on a quantifiable relationship between phosphorylation sites of tau protein in the neurofibrillary tangles (NFT) and neuronal apoptosis. Five monoclonal anti-tau antibodies (AT180, AT8, HT7, Tau2 and Tau5) for NFT labeling and TdT-mediated UTP nick-end labeling (TUNEL) for localizing apoptotic change were employed. TUNEL-stained neuronal nuclei showed significantly high density in the entorhinal cortex, cornu ammonis (CA) and the parietal cortex. In all regions, density of TUNEL-stained neuronal nuclei showed significantly direct correlation with that of AT8-, AT180- and Tau2-positive neurons. Correlation of TUNEL-stained neuronal nuclei with tau-positive neurons differed depending on the cerebral regions. Density of TUNEL-stained neuronal nuclei showed inverse correlation with that of both AT8-positive and Gallyas-stained NFT in the CA and showed significantly direct correlation with AT8- and HT7-positive neurons in the frontal cortex. Density of tau-positive and Gallyas-stained NFT was higher than that of TUNEL-stained nuclei. We conclude that phosphorylation sites of tau, 159-163 and 202-205, are probably associated with neuronal apoptosis and apoptotic change follows abnormal phosphorylation of tau.

Nitric oxide synthase-3 overexpression causes apoptosis and impairs neuronal mitochondrial function: relevance to Alzheimer's-type neurodegeneration

Dementia in Alzheimer's disease (AD) is correlated with cell loss that is mediated by apoptosis, mitochondrial (Mt) dysfunction, and possibly necrosis. Previous studies demonstrated increased expression of the nitric oxide synthase 3 (NOS3) gene in degenerating neurons of AD brains. For investigating the role of NOS3 overexpression as a mediator of neuronal loss, human PNET2 central nervous system-derived neuronal cells were infected with recombinant adenovirus vectors that expressed either human NOS3 or green fluorescent protein cDNA under the control of a CMV promoter. NOS3 overexpression resulted in apoptosis accompanied by increased levels of p53, p21/Waf1, Bax, and CD95. In addition, NOS3 overexpression impaired neuronal Mt function as demonstrated by the reduced levels of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide and nicotinamide adenine dinucleotide (reduced form)-tetrazolium reductase activities and MitoTracker Red fluorescence. These adverse effects of NOS3 were associated with increased cellular levels of reactive oxygen species and impaired membrane integrity and were not produced in cells that were transfected with a cDNA encoding catalytically inactive NOS3. Importantly, modest elevations in NOS3 expression, achieved by infection with low multiplicities of adenovirus-NOS3 infection, did not cause apoptosis but rendered the cells more sensitive to oxidative injury by H(2)O(2) or diethyldithiocarbamate. In contrast, treatment with NO donors did not enhance neuronal sensitivity to oxidative injury. These results suggest that NOS3-induced neuronal death is mediated by Mt dysfunction, oxidative injury, and impaired membrane integrity, rather than by NO production, and that neuroprotection from these adverse effects of NOS3 may be achieved by modulating intracellular levels of oxidative stress.

A two-hybrid screening of human Tau protein: interactions with Alu-derived domain

The microtubule associated protein tau has been implicated in several neurodegenerative diseases, grouped as tauopathies. To search for tau-associated proteins, the two-hybrid system was used with tau as a bait and an adult human brain cDNA library as a source of putative interacting proteins. We have identified two positive clones consisting of an Alu-derived amino acid sequence that binds to tau and show moderate homology with a motif found in several neuronal proteins related to neurodegenerative disorders. We have also demonstrated that the Alu-derived motif interacts in vitro with tau and may be involved in modulation of its phosphorylation. These findings suggest the existence of tau-binding proteins that are able to bind to tau through their Alu-derived sequence in a direct way. The possible interaction of these proteins with tau could play a role in its cellular localization, regulate the amount of phosphorylated tau and also be involved in the pathological processes of tauopathies.