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APP
Kinds of APP Terms modified by APP Selected AbstractsTenuifolin, an extract derived from tenuigenin, inhibits amyloid-, secretion in vitroACTA PHYSIOLOGICA, Issue 4 2009J. Lv Abstract Aim:, Previous studies have shown that tenuigenin, a crude extract of Polygala tenuifolia Willd. that is commonly used in traditional Chinese herbal medicine for memory loss, can reduce the secretion of A, from cultured cells. However, the mechanism underlying this effect and the active compound derived from tenuigenin is unknown. In this study, a purified component of tenuigenin, tenuifolin, was examined and revealed to be an effective compound in vitro. Methods:, A, secretion from three sets of COS-7 cells, each carrying a plasmid expressing a different form of APP was examined following the treatment with tenuifolin. Initially, tenuifolin was determined to have no inherent toxicity to either the transfected or wild type cells at the effective concentrations. Cells were then treated with 0.5,2.0 ,g mL,1 tenuifolin for 12 h and their media were examined via an ELISA for A,1-40 and A,-42. Results:, We found that treatment with 2.0 ,g mL,1 tenuifolin significantly decreased A, secretion from COS-7 cells without altering the ratio of A,1-40 and A,-42. This effect is most probably due to inhibition of the ,-site APP cleaving enzyme as A, secretion was not inhibited from cells expressing the C99 fragment. Conclusion:, Tenuifolin is an effective compound from tenuigenin. We believe that this finding should lead the way for future experiments to determine the exact mechanism for tenuifolin's effect on A, secretion. [source] Atypical papillary proliferation in gynecologic patients: A study of 32 pelvic washes,DIAGNOSTIC CYTOPATHOLOGY, Issue 2 2005Karyna C. Ventura M.D. Abstract Papillary clusters in gynecologic pelvic washes frequently cause diagnostic challenges because they can be associated with borderline or malignant ovarian tumors, as well as benign pelvic diseases. The objective of our study was to review all pelvic washes with atypical papillary proliferation (APP) and investigate whether cytomorphology and/or immunohistochemistry on cell block could determine their origin. Thirty-two pelvic washes from 31 patients containing APP were reviewed and correlated with their corresponding gynecologic or pelvic disease. Previously obtained cell blocks with immunohistochemical (IHC) stains were reviewed also. Nine of 32 washes (28%) were overcalled as malignant and were from patients with 5 borderline serous ovarian tumors (BSTO), 1 ovarian follicular cyst, 1 serous cystadenofibroma, and 1 endometrial carcinoma with ovarian seromucinous cystadenoma. BSTO and endometriosis were the most common sources of APP. Cell blocks could not discriminate further the etiology of APP. Immunohistochemistry was performed rarely and not fully contributory. Caution in interpreting papillary groups and cytohistological correlation is recommended to prevent a high false positive rate. Diagn. Cytopathol. 2005;32:76,81. © 2005 Wiley-Liss, Inc. [source] Cytosolic protein-protein interactions that regulate the amyloid precursor proteinDRUG DEVELOPMENT RESEARCH, Issue 2 2002Shasta L. Sabo Abstract Alzheimer disease (AD), a progressive neurodegenerative disease, is the most common cause of dementia in the elderly and is among the leading causes of death in adults. AD is characterized by two major pathological hallmarks, amyloid plaques and neurofibrillary tangles. For a number of reasons, amyloid plaque accumulation is widely thought to be the probable cause of AD. The amyloid plaque core is largely composed of an approximately 4-kDa peptide referred to as A,. A, is derived from its precursor, the Alzheimer amyloid protein precursor (APP), by endoproteolytic processing. APP is a type I integral membrane protein, with a long extracellular domain, one transmembrane domain, and a short (,50 amino acid) cytoplasmic tail. Despite intense efforts to decipher the function of APP, its normal physiological role has remained elusive. The carboxy-terminus of APP contains the sequence YENPTY, which is absolutely conserved across APP homologues and across species. The YENPTY sequence is important for regulation of APP processing and trafficking. Given the importance of the cytoplasmic domain in APP physiology, a number of laboratories have hypothesized that proteins that bind to the YENPTY sequence in the cytoplasmic domain of APP might regulate APP processing, trafficking, and/or function. In this article, we will discuss data revealing which proteins bind to the cytoplasmic domain of APP, how these binding-proteins regulate APP metabolism and function, and why such protein-protein interactions provide an exciting new target for therapeutic intervention in AD. Drug Dev. Res. 56:228,241, 2002. © 2002 Wiley-Liss, Inc. [source] Widespread axonal damage in the brain of drug abusers as evidenced by accumulation of ,-amyloid precursor protein (,-APP): an immunohistochemical investigationADDICTION, Issue 9 2006Andreas Büttner ABSTRACT Background In drug abusers, white matter changes have been described by neuroimaging analyses in different brain regions. A specific pattern of involvement or a predominance of a specific brain region could not be drawn. Aims To examine alterations of the white matter as a possible morphological substrate of the neuroimaging findings. Methods Brain specimens of 30 polydrug abusers and 20 controls were obtained at autopsy. The white matter from 11 different brain regions was analysed by means of immunohistochemistry for ,-amyloid precursor protein (,-APP), a marker of axonal damage. Findings In the white matter of polydrug abusers, ,-APP-immunopositive accumulations were increased significantly compared to controls. They were more prominent in the brains of younger drug abusers than in those of the elderly. With the exception of five cases (four polydrug abusers and one control case), there were no significant white matter changes seen on myelin-stained sections, but there was a concomitant microglial activation. Conclusions Our results show a significant axonal damage in the brains of polydrug abusers, which might represent the morphological substrate of a chronic-progressive drug-induced toxic-metabolic process. It is yet to be established if the observed changes are responsible for the alterations seen in different neuroimaging analyses and which drugs of abuse might be of major pathogenetic significance. [source] Interaction of a novel mitochondrial protein, 4-nitrophenylphosphatase domain and non-neuronal SNAP25-like protein homolog 1 (NIPSNAP1), with the amyloid precursor protein familyEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2010Hemachand Tummala Abstract Amyloid precursor protein (APP) and its paralogs, amyloid precursor-like protein-1 and amyloid precursor-like protein-2, appear to have redundant but essential role(s) during development. To gain insights into the physiological and possibly pathophysiological functions of APP, we used a functional proteomic approach to identify proteins that interact with the highly conserved C-terminal region of APP family proteins. Previously, we characterized an interaction between APP and ubiquitous mitochondrial creatine kinase. Here, we describe an interaction between APP and a novel protein, 4-nitrophenylphosphatase domain and non-neuronal SNAP25-like protein homolog 1 (NIPSNAP1). The interaction between APP and NIPSNAP1 was confirmed both in transiently transfected COS7 cells and in the mouse brain, where NIPSNAP1 is expressed at a high level. We demonstrate that NIPSNAP1 is targeted to the mitochondria via its N-terminal targeting sequence, and interacts with mitochondrial chaperone translocase of the outer membrane 22. Mitochondrial localization of NIPSNAP1 appears to be critical for its interaction with APP, and overexpression of APP appeared to disrupt NIPSNAP1 mitochondrial localization. Moreover, APP overexpression resulted in downregulation of NIPSNAP1 levels in cultured cells. Our data suggest that APP may affect mitochondrial function through a direct interaction with NIPSNAP1 as well as with other mitochondrial proteins. [source] Overexpression of APP provides neuroprotection in the absence of functional benefit following middle cerebral artery occlusion in ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2007Jared Clarke Abstract Cerebral ischaemia leads to a transient accumulation of ,-amyloid precursor protein (APP) and ,-amyloid (A,) peptides adjacent to the ischaemic lesion. There is conflicting evidence that APP/A, fragments may either enhance neuronal plasticity or be neurotoxic. The aim of the current study was to assess the effect of overexpression of human APP in rats on functional recovery following cerebral ischaemia. Adult APP-overexpressing (hAPP695 Tg) rats subjected to transient middle cerebral artery occlusion (MCAO) had significantly smaller infarct volumes than non-transgenic littermates, yet did not perform better on a series of sensorimotor or learning tests during a 6-month follow-up period. In fact, transgenic animals were found to be significantly more impaired in both the beam-walking and Morris water maze tests following MCAO. Immunohistochemistry showed human A,-positive staining in the cortex and hippocampus of APP transgenic rats. The present data suggest that while overexpression of APP in rats may provide some histological neuroprotection in the event of cerebral ischaemia, this does not translate into significant functional recovery. [source] The cytosolic domain of APP induces the relocalization of dynamin 3 in hippocampal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2006X. Meckler Abstract Amyloid precursor protein (APP) has been the subject of intense research to uncover its implication in Alzheimer's disease. Its physiological function is, however, still poorly understood. Herein, we investigated its possible influence on the development of cultured hippocampal neurons. A peptide corresponding to the APP intracellular domain linked to a cell-penetrating peptide was used to alter the interactions of APP with its cytosolic partners. This treatment promoted the concentration of the cytosolic GTPase dynamin 3 (Dyn3) in neurite segments when most untreated cells displayed a homogenous punctate distribution of Dyn3. The Dyn3-labelled segments were excluded from those revealed by APP staining after aldehyde fixation. Interestingly, after aldehyde fixation MAP2 also labelled segments excluded from APP-stained segments. Thus APP is also a marker for the spacing pattern of neurites demonstrated by Taylor & Fallon (2006)J. Neurosci., 26, 1154,4463. [source] Comparison of the aggregation properties, secondary structure and apoptotic effects of wild-type, Flemish and Dutch N-terminally truncated amyloid , peptidesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2001N. Demeester Abstract The Dutch (E22Q) and Flemish (A21G) mutations in the ,APP region of the amyloid precursor protein (APP) are associated with familial forms of Alzheimer dementia. However, patients with these mutations express substantially different clinical phenotypes. Therefore, secondary structure and cytotoxic effects of the three A,(12,42) variants [wild-type (WT), Dutch and Flemish] were tested. At a concentration of 5 µm the aggregation of these peptides followed the order: A,(1,42) WT > A,(12,42) WT > A,(12,42) Flemish >,A,(12,42) Dutch. The stability of the secondary structure of these peptides upon decreasing the trifluoroethanol (TFE) concentration in the buffer was followed by circular dichroism measurements. WT peptides progressively lost their ,-helical structure; this change occurred faster for both the Flemish and Dutch peptides, and at higher percentages of TFE in the buffer, and was accompanied by an increase in ,-sheet and random coil content. Apoptosis was induced in neuronal cells by the A,(12,42) WT and Flemish peptides at concentrations as low as 1,5 µm, as evidenced by propidium iodide (PI) staining, DNA laddering and caspase-3 activity measurements. Even when longer incubation times and higher peptide concentrations were applied the N-truncated Dutch peptide did not induce apoptosis. Apoptosis induced by the full length A,(1,42) peptide was weaker than that induced by its N-truncated variant. These data suggest that N-truncation enhanced the cytotoxic effects of A, WT and Flemish peptides, which may play a role in the accelerated progression of dementia. [source] APP is required during an early phase of memory formationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2000R. Mileusnic Abstract The amyloid ,/A4 protein precursor (APP) has been shown to be implicated in age-associated plastic changes at synapses that might contribute to memory loss in Alzheimer's disease. As APP has previously been reported to have multiple functions during normal development, we have employed a one-trial passive avoidance task in day-old chicks to study its role in the process of memory formation. Administration of anti-APP antibodies, injected 30 min pretraining, prevented memory for a one-trial passive avoidance task in day-old chicks without effects on general behaviour or initial acquisition. Amnesia was apparent by 30 min post-training and lasted for at least 24 h. The same result was obtained by down-regulation of APP expression by APP-antisense, injected 8,12 h pretraining. However, injections of anti-APP antibodies or APP antisense at later post-training time did not cause amnesia for the task. Unlike antibodies and antisense, injection of the APP328,332 pentapeptide, in either orientation, 30 min pretraining, rescued the memory and prevented antisense-induced amnesia. The post-training time within which the antibody- and antisense-induced amnesia, and within which the APP peptides prevent amnesia, correspond to that during which memory formation is vulnerable to disruption of the putative signal transduction functions of APP. These results suggest that: (i) APP is required during an early phase of memory formation, and (ii) the memory enhancing effect of secretory APP is localized within a 5-mer sequence of growth-promoting domain. [source] Two-stage detection of partitioned random CDMAEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2008Lukasz Krzymien Random Code Division Multiple Access (CDMA) with low complexity two-stage joint detection/decoding is considered. A sequence partitioning approach is used for modulation, where every spreading sequence is divided into M sections (partitions) which are interleaved prior to transmission. This setup, called partitioned CDMA, can be understood as a generalisation of (chip) interleave division multiple access (IDMA). An analysis of a low-complexity iterative cancellation receiver is presented for arbitrary received power distributions. It is shown that for equal rate and equal power users the asymptotic performance of partitioned CDMA is equal to the performance of CDMA with optimal a posteriori probability (APP) detection for system loads K/N,<,1.49. Effects of asynchronous signal transmission are quantified for standard pulse shaping filters and it is shown that the signal-to-noise ratios achievable in an asynchronous system are improved with respect to fully synchronous transmission. The effect of unequal received powers is examined and considerable gains in performance are obtained by judicious choices of power distributions. For certain power distribution, partitioned CDMA with iterative detection can achieve arbitrary system loads, that is detection is no longer fundamentally interference limited. The practical near-far resistance of the proposed system is illustrated using an example of a receiver with a circular receive footprint and uniformly distributed transmitters (single cell system). Copyright © 2008 John Wiley & Sons, Ltd. [source] The role of ADAM10 and ADAM17 in the ectodomain shedding of angiotensin converting enzyme and the amyloid precursor proteinFEBS JOURNAL, Issue 12 2004Tobias M. J. Allinson Numerous transmembrane proteins, including the blood pressure regulating angiotensin converting enzyme (ACE) and the Alzheimer's disease amyloid precursor protein (APP), are proteolytically shed from the plasma membrane by metalloproteases. We have used an antisense oligonucleotide (ASO) approach to delineate the role of ADAM10 and tumour necrosis factor-, converting enzyme (TACE; ADAM17) in the ectodomain shedding of ACE and APP from human SH-SY5Y cells. Although the ADAM10 ASO and TACE ASO significantly reduced (> 81%) their respective mRNA levels and reduced the ,-secretase shedding of APP by 60% and 30%, respectively, neither ASO reduced the shedding of ACE. The mercurial compound 4-aminophenylmercuric acetate (APMA) stimulated the shedding of ACE but not of APP. The APMA-stimulated secretase cleaved ACE at the same Arg-Ser bond in the juxtamembrane stalk as the constitutive secretase but was more sensitive to inhibition by a hydroxamate-based compound. The APMA-activated shedding of ACE was not reduced by the ADAM10 or TACE ASOs. These results indicate that neither ADAM10 nor TACE are involved in the shedding of ACE and that APMA, which activates a distinct ACE secretase, is the first pharmacological agent to distinguish between the shedding of ACE and APP. [source] A trans -acting factor, isolated by the three-hybrid system, that influences alternative splicing of the amyloid precursor protein minigeneFEBS JOURNAL, Issue 13 2000Andrej Poleev Two clones were isolated in a three-hybrid screen of a rat fetal brain P5 cDNA library with an intronic splicing enhancer of the amyloid precursor protein (APP) gene as RNA bait. These clones represent the rat homologues of the previously described genes CUG-binding protein (CUG-BP) and Siah-binding protein (Siah-BP). Both interact in a sequence-specific manner with the RNA bait used for library screening as well as with the CUG repeat. In contrast, no interactions were observed in the three-hybrid assay with other baits tested. In two-hybrid assays, Siah-BP interacts with U2AF65 as well as with itself. EWS, an RGG-type RNA-binding protein associated with Ewing sarcoma, was identified as an interacting partner for the CUG-BP homologue in a two-hybrid assay for protein,protein interactions performed with various factors involved in RNA metabolism. Splicing assays performed by RT-PCR from cells cotransfected with certain cDNAs and an APP minigene, used as a reporter, indicate exclusion of exon 8 if the CUG-BP homologue is present. We conclude that clone AF169013 and its counterpart in human CUG-BP could be the trans -acting factors that interact with the splicing enhancer downstream of exon 8, and in this way influence alternative splicing of the APP minigene. [source] Intracellular site of ,-secretase cleavage for A,42 generation in Neuro 2a cells harbouring a presenilin 1 mutationFEBS JOURNAL, Issue 7 2000Shinji Sudoh Previously, we reported that mutations in presenilin 1 (PS1) increased the intracellular levels of amyloid ,-protein (A,)42. However, it is still not known at which cellular site or how PS1 mutations exert their effect of enhancing A,42,,-secretase cleavage. In this study, to clarify the molecular mechanisms underlying this enhancement of A,42,,-secretase cleavage, we focused on determining the intracellular site of the cleavage. To address this issue, we used APP,C100 encoding the C-terminal ,-amyloid precursor protein (APP) fragment truncated at the N terminus of A, (C100); C100 requires only ,-secretase cleavage to yield A,. Mutated PS1 (M146L)-induced Neuro 2a cells showed enhanced A,1,42 generation from transiently expressed C100 as well as from full-length APP, whereas the generation of A,1,40 was not increased. The intracellular generation of A,1,42 from transiently expressed C100 in both mutated PS1 -induced and wild-type Neuro 2a cells was inhibited by brefeldin A. Moreover, the generation of A,1,42 and A,1,40 from a C100 mutant containing a di-lysine endoplasmic reticulum retention signal was greatly decreased, indicating that the major intracellular site of ,-secretase cleavage is not the endoplasmic reticulum. The intracellular generation of A,1,42/40 from C100 was not influenced by monensin treatment, and the level of A,1,42/40 generated from C100 carrying a sorting signal for the trans -Golgi network was higher than that generated from wild-type C100. These results using PS1 -mutation-harbouring and wild-type Neuro 2a cells suggest that A,42/40,,-secretase cleavages occur in the Golgi compartment and the trans -Golgi network, and that the PS1 mutation does not alter the intracelluar site of A,42,,-secretase cleavage in the normal APP proteolytic processing pathway. [source] Characterization of a mouse model overexpressing beta-site APP-cleaving enzyme 2 reveals a new role for BACE2GENES, BRAIN AND BEHAVIOR, Issue 2 2010G. Azkona BACE2 is homologous to BACE1, a ,-secretase that is involved in the amyloidogenic pathway of amyloid precursor protein (APP), and maps to the Down syndrome critical region of chromosome 21. Alzheimer disease neuropathology is common in Down syndrome patients at relatively early ages, and it has thus been speculated that BACE2 co-overexpression with APP would promote the early neurodegenerative phenotype. However, the in vivo function of BACE2 has not yet been elucidated. The aim of the present work has been to analyse the impact of in vivo BACE2 overexpression using a transgenic mouse model. Our results suggest that BACE2 is not involved in the amyloidogenic pathway, cognitive dysfunction or cholinergic degeneration. However, TgBACE2 animals showed increased anxiety-like behaviour along with increased numbers of noradrenergic neurones in locus coeruleus, thus suggesting an unexpected role of BACE2 overexpression. [source] One-year longitudinal evaluation of sensorimotor functions in APP751SL transgenic miceGENES, BRAIN AND BEHAVIOR, Issue 2008C. Le Cudennec Intracerebral amyloid-beta (A,) peptide deposition is considered to play a key role in Alzheimer's disease and is designated as a principal therapeutic target. The relationship between brain A, levels and clinical deficits remains, however, unclear, both in human patients and in animal models of the disease. The purpose of the present study was to investigate, in a transgenic mouse model of brain amyloidosis, the consequences of A, deposition on basic neurological functions using a longitudinal approach. Animals were phenotyped at different ages corresponding to graded neuropathological stages (from no extracellular A, deposition to high amyloid loads). Sensory functions were evaluated by assessing visual and olfactory abilities and did not show any effects of the amyloid precursor protein (APP) transgene. Motor functions were assessed using multiple experimental paradigms. Results showed that motor strength was considerably reduced in APP transgenic mice compared with control animals. No deficit was noted in a motor coordination test although APP transgenic mice displayed decreased locomotion on a stationary beam. Hypolocomotion was also observed in the standard open-field test. Measures of anxiety obtained in the elevated plus-maze show some evidence of hyperanxiety in 15-month-old transgenic mice. Some of the neurological impairments showed by APP mice had an early onset and worsened with progressive aging, in parallel to gradual accumulation of A, in brain parenchyma. Relationships between neuropathologically assessed amyloid loads and behavioral deficits were further explored, and it was observed that motor strength deficits were correlated with cortical amyloid burden. [source] Alzheimer's disease: Mechanisms and development of therapeutic strategiesGERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 4 2003Takeshi Tabira Senile plaques are the most characteristic change in Alzheimer's disease (AD). In senile plaques, , amyloid is deposited, which is composed of aggregated amyloid , protein (A,) derived from amyloid precursor protein (APP). Therefore, it is suggested that there exists a mechanism of increase of A, production or a decrease of A, degradation and/or clearance of , amyloid in AD. Mutations in familial Alzheimer's disease (FAD) genes such as APP, presenilin 1 (PS1) and presenilin 2 (PS2) result in an increase of A, production. Apolipoprotein E (ApoE), a genetic risk factor for AD, is involved in A, production and/or its clearance. Thus, it is suggested that an inhibition of A, production and a facilitation of , amyloid degradation and clearance delay the clinical onset and progression of AD, and it is possible to cure AD even after an onset of the disease, if it is still at an early phase. Researchers studied the fine mechanisms of A, production and identified enzymes that cleave-out A, from APP. Inhibitors of the cleaving enzymes are proven to be effective in ameliorating AD-like conditions in its animal models and are now being applied to humans. Researchers also found an efficient way of clearing , amyloid deposits using the immune system, which was effective in animal models. When it was applied to humans, some patients developed meningoencephalitis as a side-effect. Therefore, safer vaccines are now being developed. It did not require 20 years for researchers to develop therapeutic strategies since the discovery of A, in 1984. Now that AD is becoming a treatable disease, early diagnosis and early treatment will soon become the rule. Notably, AD may not be a psychiatric disorder any more, and mainly neurologists and geriatricians will see patients. Thus, neurogeriatrics will become more and more important. [source] A Protein Appears in a Different LightGERMAN RESEARCH, Issue 1 2005Volker Herzog Prof. Dr. APP is assumed to play a role in causing Alzheimer,s disease. Its biological functions in the human body are currently unknown but of increasing interest in basic research, especially in investigating the process of wound healing [source] Transplanted astrocytes internalize deposited ,-amyloid peptides in a transgenic mouse model of Alzheimer's diseaseGLIA, Issue 2 2008Rea Pihlaja Abstract Alzheimer's disease (AD) is one of the most devastating neurodegenerative disorders. The neuropathological hallmarks include extracellular senile plaques consisting of deposited ,-amyloid (A,) peptides and intraneuronal neurofibrillary tangles. Neuroinflammation and activation of astrocytes are also well-established features of AD neuropathology; however, the relationships between astrocytes and A, deposition remain unclear. Previous studies have shown that adult mouse astrocytes internalize and degrade A, deposits in brain sections prepared from human amyloid precursor protein (APP) transgenic mice. In the present study, we demonstrate that cultured adult, but not neonatal mouse astrocytes, respond morphologically and degrade A, deposits present in human AD brain. We also transplanted astrocytes isolated from enhanced green fluorescent protein expressing adult and neonatal mice into the hippocampi of human A, plaque-bearing transgenic APPSwe+PS1dE9 (APdE9) mice and their wild-type littermates and followed the migration and localization of these astrocytes by confocal microscopy upto 7 days after transplantation. Posttransplantation the astrocytes localized as aggregates or thin strings of many cells within the hippocampi of APdE9 and wild-type mice and showed limited migration from the injection site. Interestingly, most of the transplanted astrocytes were found near A, deposits in the hippocampi of APdE9 mice. In contrast to findings in ex vivo degradation assay, confocal microscopy revealed that both adult and neonatal transplanted astrocytes internalized human A, immunoreactive material in vivo. These results support the role of astrocytes as active A, clearing cells in the CNS that may have important implications for future development of therapeutic strategies for AD. © 2007 Wiley-Liss, Inc. [source] Mean age-of-onset of familial alzheimer disease caused by presenilin mutations correlates with both increased A,42 and decreased A,40,,§HUMAN MUTATION, Issue 7 2006Samir Kumar-Singh Abstract The varied ways in which mutations in presenilins (PSEN1 and PSEN2) affect amyloid b precursor protein (APP) processing in causing early-onset familial Alzheimer disease (FAD) are complex and not yet properly understood. Nonetheless, one useful diagnostic marker is an increased ratio of Ab42 to Ab40 (Ab42/Ab40) in patients' brain and biological fluids as well as in transgenic mice and cells. We studied Ab and APP processing for a set of nine clinical PSEN mutations on a novel and highly reproducible enzyme-linked immunosorbent assay (ELISA)-based in vitro method and also sought correlation with brain Ab analyzed by image densitometry and mass spectrometry. All mutations significantly increased Ab42/Ab40 in vitro by significantly decreasing Ab40 with accumulation of APP C-terminal fragments, a sign of decreased PSEN activity. A significant increase in absolute levels of Ab42 was observed for only half of the mutations tested. We also showed that age-of-onset of PSEN1-linked FAD correlated inversely with Ab42/Ab40 (r=,0.89; P=0.001) and absolute levels of Ab42 (r=,0.83; P=0.006), but directly with Ab40 levels (r=0.69; P=0.035). These changes also partly correlated with brain Ab42 and Ab40 levels. Together, our data suggested that Ab40 might be protective by perhaps sequestering the more toxic Ab42 and facilitating its clearance. Also, the in vitro method we describe here is a valid tool for assaying the pathogenic potential of clinical PSEN mutations in a molecular diagnostic setting. Hum Mutat 27(7), 686,695, 2006. Published 2006 Wiley-Liss, Inc. [source] Unveiling the molecular basis of intrinsic skin aging,INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 5 2005O. Holtkötter Synopsis The process of skin aging is a combination of an extrinsic and intrinsic aspect, and knowing the molecular changes underlying both is a prerequisite to being able to effectively counter it. However, despite its importance for a deeper understanding of skin aging as a whole, the process of intrinsic skin aging in particular has barely been investigated. In this study, the molecular changes of intrinsic skin aging were analyzed by applying ,Serial Analysis of Gene Expression' (SAGETM) to skin biopsies of young and aged donors. The analysis resulted in several hundred differentially expressed genes with varying statistical significance. Of these, several genes were identified that either have never been described in skin aging before (e.g. APP) or have no identified function, e.g. EST sequences. This is the first time that intrinsic skin aging has been analyzed in such a comprehensive manner, offering a new and partially unexpected set of target genes that have to be analyzed in more detail in terms of their contribution to the skin aging process. Résumé Le mécanisme de vieillissement de la peau repose sur un ensemble de phénomènes intrinsèques et extrinsèques. La connaissance des modifications moléculaires s'y rattachant est un pré requis pour tenter de le combattre. Cependant, malgré son importance pour une meilleure connaissance du vieillissement cutané dans son ensemble, le mécanisme du vieillissement cutané intrinsèque, n'a été que peu étudié. Dans cette étude, les changements moléculaires du vieillissement cutané intrinsèque ont été analysés à l'aide de la technique SAGETM, Serial Analysis of Gene Expression , appliquée à des biopsies de peau de donneurs jeunes et âgés. L'analyse montre plusieurs centaines de gènes exprimés de façon statistiquement différente. Parmi ceux-ci, plusieurs gènes n'ayant jamais été décrits dans le vieillissement cutané (par exemple l'amyloid precursor protein), ou ne possédant pas de fonction connue, par exemple les séquences EST, ont été identifiés. C'est la première fois que le vieillissement intrinsèque de la peau a été analysé de manière aussi approfondie; on découvre une nouvelle série de gènes cibles en partie inattendus dont la contribution au mécanisme du vieillissement de la peau doit être analysée plus en détails. [source] Seasonal Dynamics of Picocyanobacteria and Picoeukaryotes in a Large Shallow Lake (Lake Balaton, Hungary)INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2006Andrea Mózes Abstract The abundance and composition of autotrophic picoplankton (APP) were studied between February 2003 and March 2004 in Lake Balaton. Water samples were taken fortnightly in the eutrophic western basin and mesotrophic eastern basin. Our study, which took more than one year, revealed pronounced seasonal pattern of the picoplankton abundance and composition. According to our results there were three types of picoplankton in Lake Balaton: 1. Phycoerythrin-rich coccoid cyanobacteria (PE), dominant summer picoplankters in the mesotrophic lake area; 2. Phycocyanin-rich cyanobacteria (PC), the most abundant summer picoplankters in the eutrophic lake area; 3. Picoeukaryotes, dominant winter picoplankters in the whole lake. The observed abundance of picoeukaryotes (3 × 105 cells ml,1) was one of the highest ever found. Our study confirms that in Lake Balaton the colonial autotrophic picoplankton (colonial APP) become dominant in summer in the nutrient limited period. We have found strong negative relationship between the concentrations of available nitrogen forms (NH4,N, NO3,N, urea-N) and the colonial APP abundance. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Picophytoplankton contribution to phytoplankton community structure in the Gulf of Venice (NW Adriatic Sea)INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2006Fabrizio Bernardi Aubry Abstract The size distribution of the phytoplankton community has been analyzed on a monthly basis in the Gulf of Venice (NW Adriatic Sea), with the aim to assess the seasonal variation of the contribution of autotrophic picoplankton (APP) to total phytoplankton. The investigation was carried out in two stations characterized by different influences of fluvial inputs. APP was mainly made up of Synechococcus , the larger fraction (Utermöhl Fraction Phytoplankton, UFP: µm as maximum linear dimension) of diatoms and nanoflagellates. The average APP abundance (46 × 103 cells ml,1) and biomass (8.1 µg C dm,3) indicate that APP was a persistent and significant component of the NW Adriatic phytoplankton. The highest APP abundance (up to 270 × 103 cells ml,1) and biomass (up to 49 µg C dm,3) were recorded from summer to autumn, UFP peaked from late winter to late spring. The mean APP contribution to total phytoplankton abundance and biomass was 98% and 31% respectively. The seasonal variation of total phytoplankton biomass was mainly driven by the UFP fraction; however, a seasonal shift in the relative importance of UFP and APP occurred from spring to summer. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Autotrophic and Heterotrophic Picoplankton in Wetlands: Differences with Lake PatternsINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 5 2003María A. Rodrigo Abstract This study describes the occurrence, importance and seasonal patterns of picoplankton in two wetlands (TDNP and La Safor), and compares them to a system of fifteen interconnected lakes (Ruidera). In TDNP we performed a six-year monthly study in three sites of the wetland. Bacterial abundance increased throughout time and the autotrophic picoplankton (APP) range was wide (up to 33 × 106 cells/ml). The annual averaged APP contribution to total picoplankton and phytoplankton biovolumes was 0.5,22% and 0.03,6% respectively. There were large differences among sites in terms of APP absolute and relative abundance and seasonal patterns. In La Safor, the APP relative contribution to picoplankton and phytoplankton biovolumes was 0,25% and 0,40%, respectively, while in the Ruidera lakes was 0,47% and 0,5%, respectively. In the three systems there was a significant correlation between bacterial abundance and chlorophyll a but the slopes of the linear regressions were different. No significant relationships were found of APP abundance and trophic status in the wetlands, but were noted in the lake system. There was no clear relationship of APP contribution to total phytoplankton biomass to the trophic gradient in wetlands. In the lakes, the higher contribution of APP was found in those with higher trophic levels. [source] C-terminal 37 residues of LRP promote the amyloidogenic processing of APP independent of FE65JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 6b 2008Madepalli K. Lakshmana Abstract The major defining pathological hallmark of Alzheimer's disease (AD) is the accumulation of amyloid , protein (A,), a small peptide derived from ,- and ,-secretase cleavages of the amyloid precursor protein (APP). Recent studies have shown that the Low-density lipoprotein receptor-related protein (LRP) plays a pivotal role in the trafficking of APP and generation of A,. In particular, we recently showed that the soluble cytoplasmic tail of LRP (LRP-ST) without a membrane tether was sufficient to promote A, generation. In this study, we demonstrate that the last 37 residues of LRP cytoplasmic tail (LRP-C37) lacking the NPxY motifs and FE65 binding mediate the core pro-amyloidogenic activity of LRP-ST. Moreover, we show that the conserved dileucine motif within the LRP-C37 region is a key determinant of its A, promoting activity. Finally, results from a yeast two-hybrid screen using LRP-C37 region as bait reveal four new LRP-binding proteins implicated in intracellular signalling and membrane protein trafficking. Our findings indicate that the LRP-C37 sequence represents a new protein-binding domain that may be useful as a therapeutic target and tool to lower A, generation in AD. [source] Altered longevity-assurance activity of p53:p44 in the mouse causes memory loss, neurodegeneration and premature deathAGING CELL, Issue 2 2010Mariana Pehar Summary The longevity-assurance activity of the tumor suppressor p53 depends on the levels of ,40p53 (p44), a short and naturally occurring isoform of the p53 gene. As such, increased dosage of p44 in the mouse leads to accelerated aging and short lifespan. Here we show that mice homozygous for a transgene encoding p44 (p44+/+) display cognitive decline and synaptic impairment early in life. The synaptic deficits are attributed to hyperactivation of insulin-like growth factor 1 receptor (IGF-1R) signaling and altered metabolism of the microtubule-binding protein tau. In fact, they were rescued by either Igf1r or Mapt haploinsufficiency. When expressing a human or a ,humanized' form of the amyloid precursor protein (APP), p44+/+ animals developed a selective degeneration of memory-forming and -retrieving areas of the brain, and died prematurely. Mechanistically, the neurodegeneration was caused by both paraptosis- and autophagy-like cell deaths. These results indicate that altered longevity-assurance activity of p53:p44 causes memory loss and neurodegeneration by affecting IGF-1R signaling. Importantly, Igf1r haploinsufficiency was also able to correct the synaptic deficits of APP695/swe mice, a model of Alzheimer's disease. [source] Alpha2 macroglobulin elevation without an acute phase response in depressed adults with Down's syndrome: implications,JOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 6 2000J. A. Tsiouris Abstract Studies of immune function during depression in persons without intellectual disability (ID) have revealed elevated levels of ,2 macroglobulin (,2M) and an acute phase protein (APP) response. Clinical observation suggests that people with Down's syndrome (DS) may have associated genetic abnormalities in their immune systems. The APP response and ,2M changes in depressed versus non-depressed adults with DS was the subject of the present study. The serum pan-proteinase inhibitor ,2M, and the AP proteins c-reactive protein (CRP), ,1 antitrypsin (,1AT), ceruloplasmin (Cp), ,2 Macroglobulin (,2M), transthyretin (Trans), serum amyloid protein (SAP), and albumin (Alb) were measured in 38 adults with DS, 19 of whom were diagnosed with and 19 without depression using a sandwich enzyme-linked immunosorbent assay (ELISA). The DSM-IV criteria were used for diagnoses. Medical and neurological examinations excluded medical disorders associated with APP response. Only ,2M and CRP were significantly different in the depressed versus non-depressed groups. The ,2M was higher, a response similar to one observed in depressed people without ID, but the CRP was lower in the depressed group, especially in those subjects not on psychotropic medications, contrary to the expected APP response to depression. The results suggest that ,2M elevation in depressed adults with DS is independent of the APP response. An alternative explanation for its elevation is proposed linking the core symptom of depression with the mammalian dormancy/hibernation process. Further studies are needed to confirm that ,2M elevation is specific to depression and that it might provide a helpful marker for the diagnosis of depression in people with ID. [source] Abnormal post-translational and extracellular processing of brevican in plaque-bearing mice over-expressing APPswJOURNAL OF NEUROCHEMISTRY, Issue 3 2010Joanne M. Ajmo J. Neurochem. (2010) 113, 784,795. Abstract Aggregation of amyloid-, (A,) in the forebrain of Alzheimer's disease (AD) subjects may disturb the molecular organization of the extracellular microenvironment that modulates neural and synaptic plasticity. Proteoglycans are major components of this extracellular environment. To test the hypothesis that A,, or another amyloid precursor protein (APP) dependent mechanism modifies the accumulation and/or turnover of extracellular proteoglycans, we examined whether the expression and processing of brevican, an abundant extracellular, chondroitin sulfate (CS)-bearing proteoglycan, were altered in brains of A,-depositing transgenic mice (APPsw , APP gene bearing the Swedish mutation) as a model of AD. The molecular size of CS chains attached to brevican was smaller in hippocampal tissue from APPsw mice bearing A, deposits compared to non-transgenic mice, likely because of changes in the CS chains. Also, the abundance of the major proteolytic fragment of brevican was markedly diminished in extracts from several telencephalic regions of APPsw mice compared to non-transgenic mice, yet these immunoreactive fragments appeared to accumulate adjacent to the plaque edge. These results suggest that A, or APP exert inhibitory effects on proteolytic cleavage mechanisms responsible for synthesis and turnover of proteoglycans. As proteoglycans stabilize synaptic structure and inhibit molecular plasticity, defective brevican processing observed in A,-bearing mice and potentially end-stage human AD, may contribute to deficient neural plasticity. [source] A novel effect of rivastigmine on pre-synaptic proteins and neuronal viability in a neurodegeneration model of fetal rat primary cortical cultures and its implication in Alzheimer's diseaseJOURNAL OF NEUROCHEMISTRY, Issue 4 2010Jason A. Bailey J. Neurochem. (2010) 112, 843,853. Abstract Alzheimer's disease (AD) is characterized by deposition of amyloid-, peptide plaque, disrupted amyloid-,-precursor protein (APP) metabolism, hyperphosphorylation of Tau leading to neurofibrillary tangles and associated neurotoxicity. Moreover, there is synaptic loss in AD, which occurs early and may precede frank amyloidosis. The central cholinergic system is especially vulnerable to the toxic events associated with AD, and reduced acetylcholine levels in specific brain regions is thought to be central to memory deficits in AD. First-generation cholinesterase inhibitors have provided only symptomatic relief to patients with AD by prolonging the action of remaining acetylcholine with little or no change in the course of the disease. Some second-generation cholinesterase inhibitors are multifunctional drugs that may provide more than purely palliative results. To evaluate the effects of the dual acetylcholinesterase and butyrylcholinesterase inhibitor rivastigmine on key aspects of AD, embryonic day 16 rat primary cortical cultures were treated with rivastigmine under media conditions observed to induce time-dependent neurodegeneration. Samples were subjected to western blotting and immunocytochemistry techniques to determine what influence this drug may have on synaptic proteins and neuronal morphology. There was a strong increase in relative cell viability associated with rivastigmine treatment. Significant dose-dependent increases were observed in the levels of synaptic markers synaptosomal-associated protein of 25 kDa (SNAP-25) and synaptophysin, as well as the neuron-specific form of enolase. Together with an observed enhancement of neuronal morphology, our results suggest a rivastigmine-mediated novel neuroprotective and/or neurorestorative effects involving the synapse. Our observations may explain the potential for rivastigmine to alter the course of AD, and warrant further investigations into using butyrylcholinesterase inhibition as a therapeutic strategy for AD, especially with regard to restoration of synaptic function. [source] Interleukin-1, enhances nucleotide-induced and ,-secretase-dependent amyloid precursor protein processing in rat primary cortical neurons via up-regulation of the P2Y2 receptorJOURNAL OF NEUROCHEMISTRY, Issue 5 2009Qiongman Kong Abstract The heterologous expression and activation of the human P2Y2 nucleotide receptor (P2Y2R) in human 1321N1 astrocytoma cells stimulates ,-secretase-dependent cleavage of the amyloid precursor protein (APP), causing extracellular release of the non-amyloidogenic protein secreted amyloid precursor protein (sAPP,). To determine whether a similar response occurs in a neuronal cell, we analyzed whether P2Y2R-mediated production of sAPP, occurs in rat primary cortical neurons (rPCNs). In rPCNs, P2Y2R mRNA and receptor activity were virtually absent in quiescent cells, whereas overnight treatment with the pro-inflammatory cytokine interleukin-1, (IL-1,) up-regulated both P2Y2R mRNA expression and receptor activity by four-fold. The up-regulation of the P2Y2R was abrogated by pre-incubation with Bay 11-7085, an I,B-, phosphorylation inhibitor, which suggests that P2Y2R mRNA transcript levels are regulated through nuclear factor-,-B (NF,B) signaling. Furthermore, the P2Y2R agonist Uridine-5,-triphosphate (UTP) enhanced the release of sAPP, in rPCNs treated with IL-1, or transfected with P2Y2R cDNA. UTP-induced release of sAPP, from rPCNs was completely inhibited by pre-treatment of the cells with the metalloproteinase inhibitor TACE inhibitor (TAPI-2) or the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, and was partially inhibited by the MAPK/extracellular signal-regulated kinase inhibitor U0126 and the protein kinase C inhibitor GF109203. These data suggest that P2Y2R-mediated release of sAPP, from cortical neurons is directly dependent on a disintegrin and metalloproteinase (ADAM) 10/17 and PI3K activity, whereas extracellular signal-regulated kinase 1/2 and PI3K activity may indirectly regulate APP processing. These results demonstrate that elevated levels of pro-inflammatory cytokines associated with neurodegenerative diseases, such as IL-1,, can enhance non-amyloidogenic APP processing through up-regulation of the P2Y2R in neurons. [source] Enhanced generation of Alzheimer's amyloid-, following chronic exposure to phorbol ester correlates with differential effects on alpha and epsilon isozymes of protein kinase CJOURNAL OF NEUROCHEMISTRY, Issue 2 2009Odete A. B. Da Cruz e Silva Abstract Alzheimer's amyloid precursor protein (APP) sorting and processing are modulated through signal transduction mechanisms regulated by protein phosphorylation. Notably, protein kinase C (PKC) appears to be an important component in signaling pathways that control APP metabolism. PKCs exist in at least 11 conventional and unconventional isoforms, and PKC, and PKC, isoforms have been specifically implicated in controlling the generation of soluble APP and amyloid-, (A,) fragments of APP, although identification of the PKC substrate phospho-state-sensitive effector proteins remains challenging. In the current study, we present evidence that chronic application of phorbol esters to cultured cells in serum-free medium is associated with several phenomena, namely: (i) PKC, down-regulation; (ii) PKC, up-regulation; (iii) accumulation of APP and/or APP carboxyl-terminal fragments in the trans Golgi network; (iv) disappearance of fluorescence from cytoplasmic vesicles bearing a green fluorescent protein tagged form of APP; (v) insensitivity of soluble APP release following acute additional phorbol application; and (vi) elevated cellular APP mRNA levels and holoprotein, and secreted A,. These data indicate that, unlike acute phorbol ester application, which is accompanied by lowered A, generation, chronic phorbol ester treatment causes differential regulation of PKC isozymes and increased A, generation. These data have implications for the design of amyloid-lowering strategies based on modulating PKC activity. [source] | |||||||||||||||||||||||||