Amyloid Precursor Protein Gene Expression Research Articles

Specific Targeting and Imaging of RNA G-Quadruplex (rG4) Structure Using Non-G4-Containing l-RNA Aptamer and Fluorogenic l-Aptamer.

RNA G-quadruplex structures (rG4s) play important roles in the regulation of biological processes. So far, all the l-RNA aptamers developed to target rG4 of interest contain G4 motif itself, raising the question of whether non-G4-containing l-RNA aptamer can be developed to target rG4. Furthermore, it is unclear whether an l-Aptamer-based tool can be generated for G4 detection in vitro and imaging in cells. Herein, a new strategy is designed using a low GC content template library to develop a novel non-G4-containing l-RNA aptamer with strong binding affinity and improved binding specificity to rG4 of interest. The first non-G4-containing l-Aptamer, l-Apt.1-1, is identified with nanomolar binding affinity to amyloid precursor protein (APP) D-rG4. l-Apt.1-1 is applied to control APP gene expression in cells via targeting APP D-rG4 structure. Moreover, the first l-RNA-based fluorogenic bi-functional aptamer (FLAP) system is developed, and l-Apt.1-1_Pepper is engineered for in vitro detection and cellular imaging of APP D-rG4. This work provides an original approach for developing non-G4-containing l-RNA aptamer for rG4 targeting, and the novel l-Apt.1-1 developed for APP gene regulation, as well as the l-Apt.1-1_Pepper generated for imaging of APP rG4 structure can be further used in other applications in vitro and in cells.

Expression of APP, CDK5, and AKT1 Gene Related to Alzheimer Disease in Brain of Long-tailed Macaques

Amyloid plaques and Neurofibrillary Tangles (NFTs) are known to be key pathological features of Alzheimer disease. To gain a better understanding of this disease, studies were carried out on the Indonesian primates, the long-tailed macaques, using a spontaneous Alzheimer's disease model. Examining and identifying genetic markers involved in plaque formation and NFTs in long-tailed macaques is necessary to reveal their physiological processes. In this study, the expression of genes involved in the development of amyloid plaque (Amyloid Precursor Protein (APP)) and those that control the phosphorylation of tau protein (CDK5 and AKT1) was examined in the long-tailed macaque brain. This study showed that APP, CDK5, and AKT1 may potentially be developed as genetic markers of Alzheimer's disease. Long-tailed macaques exhibited the development of amyloid plaque in the aging brain based on the analysis of the gene expression profile of its biomarker. Furthermore, long-tailed macaques can be optimized for neurodegenerative models.

Effect of Eight Weeks of Interval Training on Amyloid Precursor Protein (APP) Gene Expression in Hippocampal Tissue in Methamphetamine-dependent Rats (Crystal)

Introduction: Methamphetamine (METH) is a stimulant drug that causes memory and learning disorders. The present study aimed to investigate the effect of eight weeks of interval training on APP gene expression in hippocampal tissue and open field test in methamphetamine-dependent rats. Method: In this experimental research, 32 rats were assigned to four equal groups of saline, primary methamphetamine (METH-1), methamphetamine+training (METH+MIT), and secondary methamphetamine (METH-2). The METH was injected at the dose of 5 mg/kg body weight for 21 days. The exercise program (5 sessions per week) included interval training (4 sets of 4 minutes with moderate intensity and 2 minutes of active rest between sets) on a treadmill. At the end of the injection and training period, the hippocampus tissue of the rats was extracted to evaluate gene expression changes. An open-field behavioral test was also conducted. The data were analyzed using the one-way ANOVA at the significance level of P≥0.05. Results: Methamphetamine significantly increased APP gene expression in METH-1,2 groups compared to saline (respectively; P≥0.007 and P≥0.005). The total distance and movement speed of rats in METH-1 and 2 groups had a significant decrease compared to saline (respectively, P≥0.004 and P≥0.026). The MIT led to a significant reduction of APP compared to METH-1,2 groups (respectively, P≥0.041 and P≥0.028). Movement speed in the MIT group increased significantly compared to the METH-1 group (P≥0.008). Conclusion: Methamphetamine reduced cognitive performance (learning and memory), and according to the results, MIT probably improved cognitive performance. Nonetheless, further studies are necessary to reach definitive conclusions.

Silver Nanoparticles Induce a Size-dependent Neurotoxicity to SH-SY5Y Neuroblastoma Cells via Ferritinophagy-mediated Oxidative Stress.

Silver nanoparticles (AgNPs) are widely used in a variety of consumer products because of their antibacterial and antifungal characteristics, but little is known about their toxicity to the brain. In this study, we investigated AgNP-induced neurotoxicity using the human neuroblastoma cancer (SH-SY5Y) cell line. After a 24 h treatment of AgNPs with two primary sizes (5 and 50nm labeled as Ag-5 and Ag-50, respectively), a series of toxicological endpoints including cell viability, expression of proteins and genes in amyloid precursor protein (APP) amyloid hydrolysis process and ferritinophagy signaling pathways, oxidative stress, intracellular iron levels, and molecular regulators of iron metabolism were evaluated. Our results showed that both Ag-5 and Ag-50 induced notable neurotoxic effects on SH-SY5Y cells indicated by cell proliferation inhibition, increased BACE1 protein expression, and decreased APP and ADAM10 gene expression. Activation of nuclear receptor coactivator 4-mediated ferritinophagy and blockade of autophagic flux were induced by AgNPs, accompanied by intracellular iron accumulation and overexpression of divalent metal-ion transporter-1 and ferroportin1 in SH-SY5Y cells. In addition, AgNPs significantly decreased glutathione peroxidase 4 protein expression but increased malondialdehyde concentration, suggesting that AgNP-induced iron accumulation may trigger oxidative stress by disruption of the intracellular oxidant and antioxidant systems. In addition, compared with Ag-50, Ag-5 with higher cellular uptake efficiency caused more detrimental effects on SH-SY5Y cells. In conclusion, our findings demonstrated a size-dependent neurotoxicity in SH-SY5Y cells by AgNPs via ferritinophagy-mediated oxidative stress.

Targeting increased levels of APP in Down syndrome: Posiphen-mediated reductions in APP and its products reverse endosomal phenotypes in the Ts65Dn mouse model.

ObjectiveRecent clinical trials targeting amyloid beta (Aβ) and tau in Alzheimer's disease (AD) have yet to demonstrate efficacy. Reviewing the hypotheses for AD pathogenesis and defining possible links between them may enhance insights into both upstream initiating events and downstream mechanisms, thereby promoting discovery of novel treatments. Evidence that in Down syndrome (DS), a population markedly predisposed to develop early onset AD, increased APP gene dose is necessary for both AD neuropathology and dementia points to normalization of the levels of the amyloid precursor protein (APP) and its products as a route to further define AD pathogenesis and discovering novel treatments.BackgroundAD and DS share several characteristic manifestations. DS is caused by trisomy of whole or part of chromosome 21; this chromosome contains about 233 protein‐coding genes, including APP. Recent evidence points to a defining role for increased expression of the gene for APP and for its 99 amino acid C‐terminal fragment (C99, also known as β‐CTF) in dysregulating the endosomal/lysosomal system. The latter is critical for normal cellular function and in neurons for transmitting neurotrophic signals.New/updated hypothesisWe hypothesize that the increase in APP gene dose in DS initiates a process in which increased levels of full‐length APP (fl‐APP) and its products, including β‐CTF and possibly Aβ peptides (Aβ42 and Aβ40), drive AD pathogenesis through an endosome‐dependent mechanism(s), which compromises transport of neurotrophic signals. To test this hypothesis, we carried out studies in the Ts65Dn mouse model of DS and examined the effects of Posiphen, an orally available small molecule shown in prior studies to reduce fl‐APP. In vitro, Posiphen lowered fl‐APP and its C‐terminal fragments, reversed Rab5 hyperactivation and early endosome enlargement, and restored retrograde transport of neurotrophin signaling. In vivo, Posiphen treatment (50 mg/kg/d, 26 days, intraperitoneal [i.p.]) of Ts65Dn mice was well tolerated and demonstrated no adverse effects in behavior. Treatment resulted in normalization of the levels of fl‐APP, C‐terminal fragments and small reductions in Aβ species, restoration to normal levels of Rab5 activity, reduced phosphorylated tau (p‐tau), and reversed deficits in TrkB (tropomyosin receptor kinase B) activation and in the Akt (protein kinase B [PKB]), ERK (extracellular signal‐regulated kinase), and CREB (cAMP response element–binding protein) signaling pathways. Remarkably, Posiphen treatment also restored the level of choline acetyltransferase protein to 2N levels. These findings support the APP gene dose hypothesis, point to the need for additional studies to explore the mechanisms by which increased APP gene expression acts to increase the risk for AD in DS, and to possible utility of treatments to normalize the levels of APP and its products for preventing AD in those with DS.Major challenges for the hypothesisImportant unanswered questions are: (1) When should one intervene in those with DS; (2) would an APP‐based strategy have untoward consequences on possible adaptive changes induced by chronically increased APP gene dose; (3) do other genes present on chromosome 21, or on other chromosomes whose expression is dysregulated in DS, contribute to AD pathogenesis; and (4) can one model strategies that combine the use of an APP‐based treatment with those directed at other AD phenotypes including p‐tau and inflammation.Linkage to other major theoriesThe APP gene dose hypothesis interfaces with the amyloid cascade hypothesis of AD as well as with the genetic and cell biological observations that support it. Moreover, upregulation of fl‐APP protein and products may drive downstream events that dysregulate tau homeostasis and inflammatory responses that contribute to propagation of AD pathogenesis.

Chronic oral application of a periodontal pathogen results in brain inflammation, neurodegeneration and amyloid beta production in wild type mice.

BackgroundThe results from cross sectional and longitudinal studies show that periodontitis is closely associated with cognitive impairment (CI) and Alzhemer’s Disease (AD). Further, studies using animal model of periodontitis and human post-mortem brain tissues from subjects with AD strongly suggest that a gram-negative periodontal pathogen, Porphyromonas gingivalis (Pg) and/or its product gingipain is/are translocated to the brain. However, neuropathology resulting from Pg oral application is not known. In this work, we tested the hypothesis that repeated exposure of wild type C57BL/6 mice to orally administered Pg results in neuroinflammation, neurodegeneration, microgliosis, astrogliosis and formation of intra- and extracellular amyloid plaque and neurofibrillary tangles (NFTs) which are pathognomonic signs of AD.MethodsExperimental chronic periodontitis was induced in ten wild type 8-week old C57BL/6 WT mice by repeated oral application (MWF/week) of Pg/gingipain for 22 weeks (experimental group). Another 10 wild type 8-week old C57BL/6 mice received vehicle alone (control group) MWF per week for 22 weeks. Brain tissues were collected and the presence of Pg/gingipain was determined by immunofluorescence (IF) microscopy, confocal microscopy, and quantitative PCR (qPCR). The hippocampi were examined for the signs of neuropathology related to AD: TNFα, IL1β, and IL6 expression (neuroinflammation), NeuN and Fluoro Jade C staining (neurodegeneration) and amyloid beta1-42 (Aβ42) production and phosphorylation of tau protein at Ser396 were assessed by IF and confocal microscopy. Further, gene expression of amyloid precursor protein (APP), beta-site APP cleaving enzyme 1 (BACE1), a disintegrin and metalloproteinase domain-containing protein10 (ADAM10) for α-secretase and presenilin1 (PSEN1) for ɣ-secretase, and NeuN (rbFox3) were determined by RT-qPCR. Microgliosis and astrogliosis were also determined by IF microscopy.ResultsPg/gingipain was detected in the hippocampi of mice in the experimental group by immunohistochemistry, confocal microscopy, and qPCR confirming the translocation of orally applied Pg to the brain. Pg/gingipain was localized intra-nuclearly and peri-nuclearly in microglia (Iba1+), astrocytes (GFAP+), neurons (NeuN+) and was evident extracellularly. Significantly greater levels of expression of IL6, TNFα and IL1β were evident in experimental as compared to control group (p<0.01, p<0.00001, p<0.00001 respectively). In addition, microgliosis and astrogliosis were evident in the experimental but not in control group (p <0.01, p<0.0001 respectively). Neurodegeneration was evident in the experimental group based on a fewer number of intact neuronal cells assessed by NeuN positivity and rbFOX3 gene expression, and there was a greater number of degenerating neurons in the hippocampi of experimental mice assessed by Fluoro Jade C positivity. APP and BACE1 gene expression were increased in experimental group compared with control group (p<0.05, p<0.001 respectively). PSEN1 gene expression was higher in experimental than control group but the difference was not statistically significant (p = 0.07). ADAM10 gene expression was significantly decreased in experimental group compared with control group (p<0.01). Extracellular Aβ42 was detected in the parenchyma in the experimental but not in the control group (p< 0.00001). Finally, phospho-Tau (Ser396) protein was detected and NFTs were evident in experimental but not in the control group (p<0.00001).ConclusionsThis study is the first to show neurodegeneration and the formation of extracellular Aβ42 in young adult WT mice after repeated oral application of Pg. The neuropathological features observed in this study strongly suggest that low grade chronic periodontal pathogen infection can result in the development of neuropathology that is consistent with that of AD.

A neurodevelopmental disorder with a nonsense mutation in the Ox-2 antigen domain of the amyloid precursor protein (APP) gene

ABSTRACTWe report a patient, an infant with a neurodevelopmental disorder manifesting intractable complex partial epilepsy, bull's eye maculopathy, microcephaly, bilateral cataracts, truncal hypotonia, and spasticity of all four extremities. Sequencing of genomic DNA revealed mutations in (a) exon 8 (Ox-2 antigen domain) of the amyloid precursor protein (APP) gene: c.1075C>T, p.Arg359* (b) exon 8 of the senataxin (SETX) gene: c.4738C>T, p.Arg1580Cys, and (c) exon 2 of the ceroid-lipofuscinosis, neuronal 8 (CLN8) gene: c.685C>G, p.Pro229Ala. Using a quantitative method for measurement of various APP-mRNA isoforms, we found that the APP-mRNA isoform of 624 bp with a deletion starting after 49 bp of the 5′ end of exon 3 followed by a complete deletion of exons 4–15, mutations in exon 1: c.22C>T, p.L18F, and exon 3: c.269A>G, p.Q90R encoding APP207 isoform was the most abundant one, and would appear to be responsible for the clinical manifestations. This is the first example that may underline the role of the epigenetic regulation in the expression of APP gene leading to a neurodevelopmental disorder resulting from a nonsense mutation in the Ox-2 antigen domain.

Neprilysin Is Suppressed by Dual-Specificity Tyrosine-Phosphorylation Regulated Kinase 1A (DYRK1A) in Down-Syndrome-Derived Fibroblasts.

Amyloid-β peptide (Aβ) accumulation is a triggering event leading to the Alzheimer's disease (AD) pathological cascade. Almost all familial AD-linked gene mutations increase Aβ production and accelerate the onset of AD. The Swedish mutation of amyloid precursor protein (APP) affects β-secretase activity and increases Aβ production up to ca. 6-fold in cultured cells; the onset age is around 50. Down syndrome (DS) patients with chromosome 21 trisomy present AD-like pathologies at earlier ages (40s) compared with sporadic AD patients, because APP gene expression is 1.5-fold higher than that in healthy people, thus causing a 1.5-fold increase in Aβ production. However, when comparing the causal relationship of Aβ accumulation with the onset age between the above two populations, early DS pathogenesis does not appear to be accounted for by the increased Aβ production alone. In this study, we found that neprilysin, a major Aβ-degrading enzyme, was downregulated in DS patient-derived fibroblasts, compared with healthy people-derived fibroblasts. Treatment with harmine, an inhibitor of dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A), which is located in the DS critical region of chromosome 21, and gene knockdown of DYRK1A, upregulated neprilysin in fibroblasts. These results suggest that a decrease in the Aβ catabolic rate may be, at least in part, one of the causes for accelerated AD-like pathogenesis in DS patients if a similar event occurs in the brains, and that neprilysin activity may be regulated directly or indirectly by DYRK1A-mediated phosphorylation. DYRK1A inhibition may be a promising disease-modifying therapy for AD via neprilysin upregulation.

Tau and Alzheimer pathobiology

The neurotoxicity of amyloid beta (Aβ), a major cleavage product of the amyloid precursor protein (APP), is enhanced by iron, as found in the amyloid plaques of Alzheimer's disease (AD) patients. By contrast, the long-known neuroprotective activity of APP is evident after α-secretase cleavage of the precursor to release sAPPα, and depends on the iron export actions of APP itself. The latter underlie its neurotrophic and protective effects in facilitating the homeostatic actions of ferroportin mediated-iron export. Thus APP-dependent iron export may alleviate oxidative stress by minimizing labile iron thus protecting neurons from iron overload during stroke and hemorrhage. Consistent with this, altered phosphorylation of iron-regulatory protein-1 (IRP1) and its signaling processes play a critical role in modulating APP translation via the 5′ untranslated region (5′UTR) of its transcript. The APP 5′UTR region encodes a functional iron-responsive element (IRE) RNA stem loop that represents a potential target for modulating APP production. Targeted regulation of APP gene expression via the modulation of 5′UTR sequence function represents a novel approach for the potential treatment of AD since altering APP translation can be used to improve both the protective brain iron balance and provide anti-amyloid efficacy. Approved drugs including paroxetine and desferrioxamine and several novel compounds have been identified that suppress abnormal metal-promoted Aβ accumulation with a subset of these acting via APP 5′UTR-dependent mechanisms to modulate APP translation and cleavage to generate the non-toxic sAPPα.

Interplay between Pur? and Egr-1 in the Transcriptional Regula-tion of Amyloid Precursor Protein Gene Expression

Background: One of the pathological hallmarks of Alzheimer’s disease is the presence of fibrillary amyloid-β deposits, which result from cleavage of the amyloid precursor protein. Understanding the regulatory mechanism of the amyloid precursor protein gene expression is crucial for comprehending the genesis and development of Alzheimer’s disease. The nucleic acid binding protein, Purα, is best characterized as a transcriptional factor (TF) with affinity to singlestrand G/C-rich regions. In a previous study, we demonstrated that the Purα protein can downregulate amyloid precursor protein (APP) promoter activity, but the mechanism underlying this downregulation requires further investigation. To better understand this mechanism, we analyzed the characteristic of the APP promoter and found that another transcriptional factor, namely Egr-1, can bind the APP promoter and may exert transcriptional regulatory effects on APP gene expression. Therefore, the interaction between these two transcriptional factors may explain the mechanism in regulating APP gene expression. Methodology/Principal Findings: The binding sites of Purα and Egr-1 on the APP promoter 5’-UTR were identified, and reporter plasmids in which the binding sites for Purα and Egr-1 were deleted have been constructed. A luciferase assay was performed, and the results demonstrated that both Purα and Egr-1 lost their regulatory effects when these binding sites were deleted. The luciferase results also demonstrated that Purα can suppress the effects of Egr-1 on APP promoter activities. The electrophoresis mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay results demonstrated that both Purα and Egr- 1 can competently bind to the APP promoter. The endogenous Egr-1 expression was disturbed with the HDAC inhibitor and suramin, and the Egr-1 expression level affected the APP promoter activities and APP gene expression. Purα can also suppress the endogenous expression of Egr-1. Conclusion/Significance: The mechanism through which Purα regulates AβPP gene expression may involve its interaction with Egr-1, which is a positive regulator of the APP promoter. Because both transcriptional factors possess the binding sites in the APP promoter 5’-UTR and the position of these sites are overlapped, there may exist a displacement mechanism for these two transcriptional factors. In addition, Purα also suppresses the endogenous Egr-1 expression. All of these findings explain the mechanism through which Purα regulates APP gene expression.

Altered gene expression of amyloid precursor protein in the adipose tissue and brain of obese mice fed with long-term high-fat diet and streptozotocin-induced diabetic mice

Mid-life obesity is associated with increased risk of Alzheimer's disease (AD). Amyloid precursor protein (APP) and its processing are centrally involved in the etiology of AD. Our previous studies demonstrated that human APP is expressed in adipocytes, up-regulated with obesity, and correlated with adipokine expression. This study was to determine whether APP expression is also dysregulated in mouse models of obesity and diabetes. Six-week-old C57BL/6 mice were fed normal or high-fat diets (HFD) until 16, 26, 36, 47, or 77 weeks of age. We measured gene expression of APP and adipokines, levels of glucose and insulin, and area under the glucose curve (AUCglucose) during the glucose tolerance test. Using quantitative real-time polymerase chain reaction (PCR), we demonstrated that APP expression in subcutaneous adipose tissue (SAT) significantly increased in all HFD mice groups, and that it correlated with the levels of AUCglucose, insulin, and expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and chemokine (C-C motif) ligand 2 (CCL2) genes. Thiazolidinedione treatment significantly reduced plasma insulin levels and APP expression in SAT and epididymal adipose tissue. APP expression in the SAT and brain also decreased significantly in streptozotocin-induced diabetic mice, indicating an important role of insulin in the regulation of APP gene expression. These results demonstrate that adipose tissue APP expression is increased with obesity and regulated by insulin levels, suggesting that the regulation and role of APP are similar in humans and mice. Insights into APP regulation and processing in the adipose tissue may improve our understanding of obesity-related adipose tissue inflammation and the increased risk of AD in obese individuals.

Molecular Mechanism Of Regulation Of Extramedullary Infiltration In AML1/ETO Positive Acute Myeloid Leukemia By APP/ERK/MMP-2

Amyloid precursor protein (APP) has been reported to be highly expressed in AML1/ETO positive acute myeloid leukemia (AML1/ETO+ AML), and we found it express even higher in those with extramedullary infiltration in our previous study. But it's still unknown what role APP plays and how it works in AML1/ETO+ AML. This study was designed to investigate the effect of APP gene on the prognosis and its molecular mechanism of extramedullary infiltration in the patients with AML1/ETO+ AML.44 cases of AML1/ETO+ AML patients with median age of 29 years old, who were admitted to our hospital from February, 2006 to February, 2012 and made the diagnosis according to WHO2008 diagnosis standard, and had completed conventional induction, consolidation and intensive therapy, were investigated in this study. They were divided into high expression group (n=22) and low one (n=22) according to APP mRNA median expression level from bone marrow cells before the first chemotherapy by QRT-PCR. Some of bone marrow samples were checked by Western Blot, and 5 biopsy specimens from extramedullary infiltration were tested by APP antibody immunohistochemistry staining. Incidence of extramedullary leukemia (EML), complete response (CR), overall survival (OS), and recurrence free survival (RFS) was differentiated between the two groups. Differences of cell ultrastructure, migration, proliferation, apoptosis and expression of ERK, MMP-2, MMP-9 and CXCR4 were studied on Kasumi-1 cell line between wild, negative control (NC) and si-APP group in which the expression levels of APP gene were down regulated with application of siRNA technology.ÇåThe incidence of EML was significantly different (45.5% versus 9.1%) in the two groups (P=0.007) and it was positively correlative with the expression levels of APP mRNA (rp=0.435, P=0.004). Extramedullary infiltration site also showed high expression of APP by immunohistochemistry, while the control group was negative. Not only CR rate after two courses of chemotherapy, but also OS and RFS with median follow-up of 28(4-70) months, of high expression group was all significantly lower than that of low expression group (Table 1). Compared with the wild and NC group, cell apoptosis of si-APP group was significantly increased (12.33 ± 0.75 vs 19.80 ± 1.51, P=0.000); the number of microvilli on the surface of the cell membrane significantly reduced; the ability of the cell migration by Tanswell chamber migration assay significantly decreased (P=0.004); and expression of P-ERK, c-MYC, MMP-2 decreased significantly which was confirmed by ERK and c-MYC blocker treatment (Figure 1). [Display omitted] [Display omitted] In sum, incidence of EML is significantly higher and the prognosis is poor in the patients with AML1/ETO+ AML with high expression of APP gene. We first describe that APP gene may mediate AML1/ETO+ leukemia cells in the development of extramedullary infiltration by up-regulation of the ERK/MMP-2 pathway. Disclosures:No relevant conflicts of interest to declare.

Enhanced proteolytic clearance of plasma Aβ by peripherally administered neprilysin does not result in reduced levels of brain Aβ in mice.

Accumulation of β-amyloid (Aβ) in the brain is believed to contribute to the pathology of Alzheimer's Disease (AD). Aβ levels are controlled by the production of Aβ from amyloid precursor protein, degradation by proteases, and peripheral clearance. In this study we sought to determine whether enhancing clearance of plasma Aβ with a peripherally administered Aβ-degrading protease would reduce brain Aβ levels through a peripheral sink. Neprilysin (NEP) is a zinc-dependent metalloprotease that is one of the key Aβ-degrading enzymes in the brain. We developed a NEP fusion protein with in vitro degradation of Aβ and a 10 day plasma half-life in mouse. Intravenous administration of NEP to wild-type and APP23 transgenic mice resulted in dose-dependent clearance of plasma Aβ. However, this did not correspond to reduced levels of soluble brain Aβ with treatment up to 5 weeks in WT mice or formic acid-extractable brain Aβ with 3 month treatment in aged APP23. In contrast, intracranial injection of NEP resulted in an acute decrease in soluble brain Aβ. We found no change in amyloid precursor protein gene expression in mice treated with intravenous NEP, suggesting that the lack of effects in the brain following this route of administration was not caused by compensatory upregulation of Aβ production. Taken together, these results suggest a lack of a robust peripheral Aβ efflux sink through which brain amyloid burdens can be therapeutically reduced.

Hippocampal Neurofibromin and Amyloid Precursor Protein Expression in Dopamine D3 Receptor Knock-out Mice Following Passive Avoidance Conditioning

Passive avoidance (PA) conditioning is a fear motivated task able to initiate a cascade of altered gene expression within the hippocampus, a structure critical to learning and memory. We have previously shown that neurofibromin (NF1) and amyloid precursor protein (APP), two genes implicated in cognitive function, are differentially expressed in brain of dopamine D3 receptor knock-out mice (D(3)R(-/-)), suggesting that the receptor might have a role in their trascriptional regulation. Here in this study, we hypothesized that during acquisition of PA conditioning the expression of NF1 and APP genes could be influenced by D(3)Rs. To address this issue, we analyzed the expression of NF1 and APP in the hippocampus of both wild-type (WT) and D(3)R(-/-) mice subjected to the single trial step-through PA paradigm. Our finding demonstrated that (1) D(3)R(-/-) mice exhibit increased cognitive performance as compared to WT mice in the step-through PA trial; (2) acquisition of PA increased D(3)R and NF1, but not APP expression in WT mice hippocampus; (3) PA-driven NF1 induction in WT was abrogated in D(3)R(-/-) mice and finally that (4) the heightened basal APP expression observed in naive D(3)R(-/-) mice was totally reversed by acquisition of PA. In conclusion, the present finding show for the first time that both D(3)R and NF1 genes are upregulated following PA conditioning and suggest that hippocampal D(3)Rs might be relevant to NF1 transcriptional regulation in the hippocampus.

Morphological and functional abnormalities in neuromuscular junctions of Drosophila melanogaster induced by human APP gene expression

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by a loss of neurocortical and hippocampal synapses that precedes amyloidosis and neurodegeneration and closely correlates with memory impairment. Mutations in the amyloid precursor protein (APP) cause familial AD and result in increased production of amyloid-β-protein (Aβ). To gain insight into the synaptic effects of APP protein in AD patients, wild-type APP, its mutant form APP-Swedish responsible for familial AD, and human beta-secretase gene were expressed in motor neurons of Drosophila melanogaster larvae. It was found that targeted expression of APP (APP-Swedish) in Drosophila larval motor neurons caused significant morphological and functional changes in neuromuscular junctions (NMJs)-a dramatic increase in the number of synaptic boutons and altered exocytosis revealed by incorporation of the styryl dye FM4-64. Analysis of the number and distribution of mitochondria showed that motor neurons overexpressing APP (APP-Swedish) had a significant reduction of functional mitochondria in the presynaptic terminal. Significant synaptic abnormalities were observed with APP (APP-Swedish) expression, as well as for double transgenes bearing APP (APP-Swedish) and human beta-secretase (BACE), which caused secretion of amyloid beta protein (Aβ). We suggest that APP participates in regulation of synaptic functions and its elevated expression leads to synaptic pathology independently from Aβ neurotoxic effects.

Reduction in Inflammation and the Expression of Amyloid Precursor Protein and Other Proteins Related to Alzheimer's Disease following Gastric Bypass Surgery

Obesity and type 2 diabetes are associated with an increase in the incidence and prevalence of Alzheimer's disease (AD) and an impaired cognitive function. Because peripheral blood mononuclear cells (MNC) express amyloid precursor protein (APP), the precursor of β-amyloid, which forms the pathognomonic plaques in the brain, we hypothesized that APP expression diminishes after the marked caloric restriction and weight loss associated with Roux-en-Y gastric bypass (RYGB) surgery. Fifteen type 2 diabetic patients with morbid obesity (body mass index, 52.1 ± 13 kg/m(2)) underwent RYGB, and the expression of inflammatory and AD-related genes was examined before and after 6 months in plasma and in MNC. Body mass index fell to 40.4 ± 11.1 kg/m(2) at 6 months after RYGB. There was a significant fall in plasma concentrations of glucose and insulin and in homeostasis model of assessment for insulin resistance. The expression of APP mRNA fell by 31 ± 9%, and that of protein fell by 36 ± 14%. In addition, there was a reduction in the expression of other AD-related genes including presinilin-2, ADAM-9, GSK-3β, PICALM, SORL-1, and clusterin (P < 0.05 for all). Additionally, the expression of c-Fos, a subunit of the proinflammatory transcription factor AP-1, was also suppressed after RYGB. These changes occurred in parallel with reductions in other proinflammatory mediators including C-reactive protein and monocyte chemoattractant protein-1. Thus, the reversal of the proinflammatory state of obesity is associated with a concomitant reduction in the expression of APP and other AD-related genes in MNC. We conclude that obesity and caloric intake modulate the expression of APP in MNC. If indeed, this effect also occurs in the brain, this may have implications for the pathogenesis and the treatment of AD. It is relevant that cognitive function has been shown to improve with weight loss following bariatric surgery.

Amyloid precursor protein as a potential marker of malignancy and prognosis in papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is the most common carcinoma of the thyroid gland and has a relatively favorable prognosis. However, it is important to identify PTC characteristics that indicate a high risk for recurrence and metastasis. Recent data indicate that the amyloid precursor protein (APP) is involved in cell adhesion, motility and proliferation. At present, the expression levels of APP and their prognostic significance in PTC have not been studied. In the present study, the APP gene expression in 10 PTCs and their adjacent thyroid tissue samples was analyzed using quantitative real time-PCR. Tissue array blocks were obtained from 90 PTC cases. Tumor regions and their adjacent non-tumor regions were analyzed in tissue array blocks and immunohistochemistry was conducted using sectioned slides. Semi-quantitative scores were correlated with the clinicopathological factors of 90 PTC patients. APP-specific mRNA was increased 50-fold in PTC samples compared with their adjacent thyroid tissue. The immunohistochemistry results showed APP expression levels to be significantly increased in PTC samples compared with their adjacent non-tumor thyroid tissue (p<0.001). High APP scores were significantly correlated with large tumor size, extracapsular invasion and lymph node metastasis. The amyloid precursor protein was overexpressed in PTC and a high APP expression was associated with high malignant potential. Therefore, APP may serve as a prognostic marker and potential novel therapeutic target in PTC.

Prolyl Isomerase Pin1 Promotes Amyloid Precursor Protein (APP) Turnover by Inhibiting Glycogen Synthase Kinase-3β (GSK3β) Activity: NOVEL MECHANISM FOR Pin1 TO PROTECT AGAINST ALZHEIMER DISEASE

Alzheimer disease (AD) is characterized by the presence of senile plaques of amyloid-β (Aβ) peptides derived from amyloid precursor protein (APP) and neurofibrillary tangles made of hyperphosphorylated Tau. Increasing APP gene dosage or expression has been shown to cause familial early-onset AD. However, whether and how protein stability of APP is regulated is unclear. The prolyl isomerase Pin1 and glycogen synthase kinase-3β (GSK3β) have been shown to have the opposite effects on APP processing and Tau hyperphosphorylation, relevant to the pathogenesis of AD. However, nothing is known about their relationship. In this study, we found that Pin1 binds to the pT330-P motif in GSK3β to inhibit its kinase activity. Furthermore, Pin1 promotes protein turnover of APP by inhibiting GSK3β activity. A point mutation either at Thr-330, the Pin1-binding site in GSK3β, or at Thr-668, the GSK3β phosphorylation site in APP, abolished the regulation of GSK3β activity, Thr-668 phosphorylation, and APP stability by Pin1, resulting in reduced non-amyloidogenic APP processing and increased APP levels. These results uncover a novel role of Pin1 in inhibiting GSK3β kinase activity to reduce APP protein levels, providing a previously unrecognized mechanism by which Pin1 protects against Alzheimer disease.

Interplay between Pur α and Egr-1 in the transcriptional regulation of amyloid precursor protein gene expression

Interplay between Pur α and Egr-1 in the transcriptional regulation of amyloid precursor protein gene expression

비만 및 당뇨가 생쥐 지방조직에서의 Alzheimer's APP 유전자 발현에 미치는 영향

The aim of this study was to determine whether Alzheimer’s amyloid precursor protein (APP) is dysregulated in adipose tissues of C57BL/6 male mice by high-fat diet (HFD) induced obesity, aging, or streptozotocin (STZ)-induced diabetes. APP mRNA expression was examined by quantitative real-time PCR (QPCR) in subcutaneous (SAT) and epididymal adipose tissues (EAT) from mice in 8 different condition groups. By combining conditions of age (16 weeks/26 weeks of age), diet (normal diet (ND)/high-fat diet), and induction of diabetes (non-diabetic/diabetic), 88 mice were divided into 8 different groups. QPCR demonstrated that APP expression in SAT was significantly increased by about two-fold in HFD-induced obese mice compared to both 16 week-old and 26 week-old mice in the ND group (16 weeks p=0.001; 26 weeks p<0.0001), but no changes in EAT was found. Particular effects of aging on APP gene expression were not observed in either adipose tissue depots. Significantly decreased APP expression was found in SAT in STZ-induced diabetic mice fed on ND or HFD at 16 weeks of age (ND p<0.05; HFD p<0.01). Linear regression analysis demonstrated that APP expression levels correlated with body weight in both the non-diabetic group (R=0.657, p<0.0001, n=39) and the diabetic group (R=0.508, p=<0.0001, n=49), but did not correlate with plasma glucose levels, which suggests that decreased APP expression in STZ-induced diabetic mice is most likely due to weight loss rather than hyperglycemia. These data confirm APP dysregulation by weight changes in humans and suggest a possible role linking midlife obesity with the later development of amyloidogenesis in the brain of older patients with Alzheimer’s disease.