Alzheimer's Amyloid Precursor Protein Research Articles

Iron response elements (IREs)-mRNA of Alzheimer's amyloid precursor protein binding to iron regulatory protein (IRP1): a combined molecular docking and spectroscopic approach

The interaction between the stem-loop structure of the Alzheimer's amyloid precursor protein IRE mRNA and iron regulatory protein was examined by employing molecular docking and multi-spectroscopic techniques. A detailed molecular docking analysis of APP IRE mRNA∙IRP1 reveals that 11 residues are involved in hydrogen bonding as the main driving force for the interaction. Fluorescence binding results revealed a strong interaction between APP IRE mRNA and IRP1 with a binding affinity and an average binding sites of 31.3 × 106 M−1 and 1.0, respectively. Addition of Fe2+(anaerobic) showed a decreased (3.3-fold) binding affinity of APP mRNA∙IRP1. Further, thermodynamic parameters of APP mRNA∙IRP1 interactions were an enthalpy-driven and entropy-favored event, with a large negative ΔH (–25.7 ± 2.5 kJ/mol) and a positive ΔS (65.0 ± 3.7 J/mol·K). A negative ΔH value for the complex formation suggested the contribution of hydrogen bonds and van der Waals forces. The addition of iron increased the enthalpic contribution by 38% and decreased the entropic influence by 97%. Furthermore, the stopped-flow kinetics of APP IRE mRNA∙IRP1 also confirmed the complex formation, having the rate of association (kon) and the rate of dissociation (koff) as 341 μM−1 s−1, and 11 s−1, respectively. The addition of Fe2+ has decreased the rate of association (kon) by ~ three-fold, whereas the rate of dissociation (koff) has increased by ~ two-fold. The activation energy for APP mRNA∙IRP1 complex was 52.5 ± 2.1 kJ/mol. The addition of Fe2+ changed appreciably the activation energy for the binding of APP mRNA with IRP1. Moreover, circular dichroism spectroscopy has confirmed further the APP mRNA∙IRP1 complex formation and IRP1 secondary structure change with the addition of APP mRNA. In the interaction between APP mRNA and IRP1, iron promotes structural changes in the APP IRE mRNA∙IRP1 complexes by changing the number of hydrogen bonds and promoting a conformational change in the IRP1 structure when it is bound to the APP IRE mRNA. It further illustrates how IRE stem-loop structure influences selectively the thermodynamics and kinetics of these protein-RNA interactions.

The role of Amyloid precursor protein (APP) in Alzheimer’s disease (AD)

Alzheimer’s disease (AD) is a neurodegenerative disease, which endangered human life expectancy. Since 2020, approximately 50 million people worldwide had got AD. With the increase of longevity of the whole population, the potential threat of AD Also increase. Although the pathogeny of AD is still not entirely clear, there have developed several hypotheses for AD. One of them is Aβ hypothesis. It suggests the deposition of Aβ plaques outside the neuron cells. This may cause a series of problems. It may induce ER stress, oxidative stress, neuro-inflammation and inhabited LTP in patients’ hippocampus. These all stimulate the neuron cell death. The loss of neuron cells will further induce these symptoms and then triggered the loss of memory. Although there are still a lot of debates on the now existing drugs about AD, the further studies on the role of Aß on AD is needed.

Implicative role of epidermal growth factor receptor and its associated signaling partners in the pathogenesis of Alzheimer's disease.

Epidermal growth factor receptor (EGFR) plays a pivotal role in early brain development, although its expression pattern declines in accordance with the maturation of the active nervous system. However, recurrence of EGFR expression in brain cells takes place during neural functioning decline and brain atrophy in order to maintain the homeostatic neuronal pool. As a consequence, neurotoxic lesions such as amyloid beta fragment (Aβ1-42) formed during the alternative splicing of amyloid precursor protein in Alzheimer's disease (AD) elevate the expression of EGFR. This inappropriate peptide deposition on EGFR results in the sustained phosphorylation of the downstream signaling axis, leading to extensive Aβ1-42 production and tau phosphorylation as subsequent pathogenesis. Recent reports convey that the pathophysiology of AD is correlated with EGFR and its associated membrane receptor complex molecules. One such family of molecules is the annexin superfamily, which has synergistic relationships with EGFR and is known for membrane-bound signaling that contributes to a variety of inflammatory responses. Besides, Galectin-3, tissue-type activated plasminogen activator, and many more, which lineate the secretion of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-18) result in severe neuronal loss. Altogether, we emphasized the perspectives of cellular senescence up-regulated by EGFR and its associated membrane receptor molecules in the pathogenesis of AD as a target for a therapeutical alternative to intervene in AD.

Amyloid precursor protein in Alzheimer's disease.

Amyloid precursor protein (APP) is a membrane protein expressed in several tissues. The occurrence of APP is predominant in synapses of nerve cells. It acts as a cell surface receptor and plays a vital role as a regulator of synapse formation, iron export and neural plasticity. It is encoded by the APP gene that is regulated by substrate presentation. APP is a precursor protein activated by proteolytic cleavage and thereby generating amyloid beta (Aβ) peptides which eventually form amyloid plaques that accumulate in Alzheimer's disease patients' brains. In this chapter, we highlight basic mechanism, structure, expression patterns and cleavage of amyloid plaques, and its diagnosis and potential treatment for Alzheimer's disease.

Abstract 1397: Targeting the Iron Response Element (IRE)-mRNA of Alzheimer's Amyloid Precursor Protein for Binding to Iron Response Protein (IRP1)

Abstract 1397: Targeting the Iron Response Element (IRE)-mRNA of Alzheimer's Amyloid Precursor Protein for Binding to Iron Response Protein (IRP1)

Temporal and spatially controlled APP transgene expression using Cre-dependent alleles.

ABSTRACTAlthough a large number of mouse models have been made to study Alzheimer's disease, only a handful allow experimental control over the location or timing of the protein being used to drive pathology. Other fields have used the Cre and the tamoxifen-inducible CreER driver lines to achieve precise spatial and temporal control over gene deletion and transgene expression, yet these tools have not been widely used in studies of neurodegeneration. Here, we describe two strategies for harnessing the wide range of Cre and CreER driver lines to control expression of disease-associated amyloid precursor protein (APP) in modeling Alzheimer's amyloid pathology. We show that CreER-based spatial and temporal control over APP expression can be achieved with existing lines by combining a Cre driver with a tetracycline-transactivator (tTA)-dependent APP responder using a Cre-to-tTA converter line. We then describe a new mouse line that places APP expression under direct control of Cre recombinase using an intervening lox-stop-lox cassette. Mating this allele with a CreER driver allows both spatial and temporal control over APP expression, and with it, amyloid onset. This article has an associated First Person interview with the first author of the paper.

Regulation of PPARα by APP in Alzheimer disease affects the pharmacological modulation of synaptic activity.

Among genetic susceptibility loci associated with late-onset Alzheimer disease (LOAD), genetic polymorphisms identified in genes encoding lipid carriers led to the hypothesis that a disruption of lipid metabolism could promote disease progression. We previously reported that amyloid precursor protein (APP) involved in Alzheimer disease (AD) physiopathology impairs lipid synthesis needed for cortical networks’ activity and that activation of peroxisome proliferator–activated receptor α (PPARα), a metabolic regulator involved in lipid metabolism, improves synaptic plasticity in an AD mouse model. These observations led us to investigate a possible correlation between PPARα function and full-length APP expression. Here, we report that PPARα expression and activation were inversely related to APP expression both in LOAD brains and in early-onset AD cases with a duplication of the APP gene, but not in control human brains. Moreover, human APP expression decreased PPARA expression and its related target genes in transgenic mice and in cultured cortical cells, while opposite results were observed in APP-silenced cortical networks. In cultured neurons, APP-mediated decrease or increase in synaptic activity was corrected by a PPARα-specific agonist and antagonist, respectively. APP-mediated control of synaptic activity was abolished following PPARα deficiency, indicating a key function of PPARα in this process.

Altered metabolic pathways in a transgenic mouse model suggest mechanistic role of amyloid precursor protein overexpression in Alzheimer's disease.

The mechanistic role of amyloid precursor protein (APP) in Alzheimer's disease (AD) remains unclear. Here, we aimed to identify alterations in cerebral metabolites and metabolic pathways in cortex, hippocampus and serum samples from Tg2576 mice, a widely used mouse model of AD. Metabolomic profilings using liquid chromatography-mass spectrometry were performed and analysed with MetaboAnalyst and weighted correlation network analysis (WGCNA). Expressions of 11 metabolites in cortex, including hydroxyphenyllactate-linked to oxidative stress-and phosphatidylserine-lipid metabolism-were significantly different between Tg2576 and WT mice (false discovery rate < 0.05). Four metabolic pathways from cortex, including glycerophospholipid metabolism and pyrimidine metabolism, and one pathway (sulphur metabolism) from hippocampus, were significantly enriched in Tg2576 mice. Network analysis identified five pathways, including alanine, aspartate and glutamate metabolism, and mitochondria electron transport chain, that were significantly correlated with AD genotype. Changes in metabolite concentrations and metabolic pathways are present in the early stage of APP pathology, and may be important for AD development and progression.

Targeting Amyloidogenic Processing of APP in Alzheimer's Disease.

Alzheimer’s disease (AD) is the most common type of senile dementia, characterized by neurofibrillary tangle and amyloid plaque in brain pathology. Major efforts in AD drug were devoted to the interference with the production and accumulation of amyloid-β peptide (Aβ), which plays a causal role in the pathogenesis of AD. Aβ is generated from amyloid precursor protein (APP), by consecutive cleavage by β-secretase and γ-secretase. Therefore, β-secretase and γ-secretase inhibition have been the focus for AD drug discovery efforts for amyloid reduction. Here, we review β-secretase inhibitors and γ-secretase inhibitors/modulators, and their efficacies in clinical trials. In addition, we discussed the novel concept of specifically targeting the γ-secretase substrate APP. Targeting amyloidogenic processing of APP is still a fundamentally sound strategy to develop disease-modifying AD therapies and recent advance in γ-secretase/APP complex structure provides new opportunities in designing selective inhibitors/modulators for AD.

Protein-Protein interactions uncover candidate 'core genes' within omnigenic disease networks.

Genome wide association studies (GWAS) of human diseases have generally identified many loci associated with risk with relatively small effect sizes. The omnigenic model attempts to explain this observation by suggesting that diseases can be thought of as networks, where genes with direct involvement in disease-relevant biological pathways are named 'core genes', while peripheral genes influence disease risk via their interactions or regulatory effects on core genes. Here, we demonstrate a method for identifying candidate core genes solely from genes in or near disease-associated SNPs (GWAS hits) in conjunction with protein-protein interaction network data. Applied to 1,381 GWAS studies from 5 ancestries, we identify a total of 1,865 candidate core genes in 343 GWAS studies. Our analysis identifies several well-known disease-related genes that are not identified by GWAS, including BRCA1 in Breast Cancer, Amyloid Precursor Protein (APP) in Alzheimer's Disease, INS in A1C measurement and Type 2 Diabetes, and PCSK9 in LDL cholesterol, amongst others. Notably candidate core genes are preferentially enriched for disease relevance over GWAS hits and are enriched for both Clinvar pathogenic variants and known drug targets-consistent with the predictions of the omnigenic model. We subsequently use parent term annotations provided by the GWAS catalog, to merge related GWAS studies and identify candidate core genes in over-arching disease processes such as cancer-where we identify 109 candidate core genes.

Reduction of aluminum ion neurotoxicity through a small peptide application – NAP treatment of Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia in late life. It is difficult to precisely diagnose AD at early stages, making biomarker search essential for further developments. The objective of this study was to identify protein biomarkers associated with aluminum ions toxicity (AD-like toxicity) in a human neuroblastoma cell model, SH-SY5Y and assess potential prevention by NAP (NAPVSIPQ). Complete proteomic techniques were implemented. Four proteins were identified as up-regulated with aluminum ion treatment, CBP80/20-dependent translation initiation factor (CTIF), Early endosome antigen 1 (EEA1), Leucine-rich repeat neuronal protein 4 (LRRN4) and Phosphatidylinositol 3-kinase regulatory subunit beta (PI3KR2). Of these four proteins, EEA1 and PI3KR2 were down-regulated after NAP-induced neuroprotective activity in neuroblastoma cells. Thus, aluminum ions may increase the risk for neurotoxicity in AD, and the use of NAP is suggested as a treatment to provide additional protection against the effects of aluminum ions, via EEA1 and PI3KR2, associated with sorting and processing of the AD amyloid precursor protein (APP) through the endosomal system.

Proteins as the molecular markers of male fertility

Proteins play a key role in many functions such as metabolic activity, differentiation, as cargos, and cell fate regulators. It is necessary to know about the proteins involved in male fertility to develop remedies for the treatment of male infertility. However, the role of the proteins is not limited to particular aspect in the biological systems. Some of the proteins act as ion channels such as catsper, and protein such as Nanos is a translational repressor in germ cells and expressed in prenatal period whose role in male fertility is not clearly understood. Rbm5 is a pre-mRNA splicing factor necessary for sperm differentiation whose loss results in deficit in sperm production. DEFB114 is a beta-defensin family protein necessary for sperm motility in lipopolysaccharide-challenged mice. TEX101 is a plasma membrane specific germ cell protein whose function is not clearly identified. Gpr56 is an another adhesion protein whose null mutation leads to arrest of production of pupps. Amyloid precursor protein in Alzheimer's disease plays a role in male fertility whose function is uncertain which has to be considered while targeting them. The study on amyloid precursor protein in male fertility is a novel thing, but requires further study in correlation to Alzheimer's disease.

Physiological effects of amyloid precursor protein and its derivatives on neural stem cell biology and signaling pathways involved.

The pathological implication of amyloid precursor protein (APP) in Alzheimer’s disease has been widely documented due to its involvement in the generation of amyloid-β peptide. However, the physiological functions of APP are still poorly understood. APP is considered a multimodal protein due to its role in a wide variety of processes, both in the embryo and in the adult brain. Specifically, APP seems to play a key role in the proliferation, differentiation and maturation of neural stem cells. In addition, APP can be processed through two canonical processing pathways, generating different functionally active fragments: soluble APP-α, soluble APP-β, amyloid-β peptide and the APP intracellular C-terminal domain. These fragments also appear to modulate various functions in neural stem cells, including the processes of proliferation, neurogenesis, gliogenesis or cell death. However, the molecular mechanisms involved in these effects are still unclear. In this review, we summarize the physiological functions of APP and its main proteolytic derivatives in neural stem cells, as well as the possible signaling pathways that could be implicated in these effects. The knowledge of these functions and signaling pathways involved in the onset or during the development of Alzheimer’s disease is essential to advance the understanding of the pathogenesis of Alzheimer’s disease, and in the search for potential therapeutic targets.

Osthole suppresses amyloid precursor protein expression by up-regulating miRNA-101a-3p in Alzheimer's disease cell model

To investigate the effect of osthole on the expression of amyloid precursor protein (APP) in Alzheimer's disease (AD) cell model and its mechanism. The SH-SY5Y cell with over expression of APP was established by transfection by liposome 2000. The cells were treated with different concentrations of osthole, and the cell viability was determined by MTT and lactate dehydrogenase (LDH) assay. The differentially expressed miRNAs with and without osthole treatment were detected by miRNA array, and the target genes binding to the differentially expressed miRNAs were identified and verified by databases and Cytoscape. After the inhibitor of the differentially expressed miRNA was transduced into cells, the changes of APP and amyloid β (Aβ) protein were determined by immunofluorescence cytochemistry, and the mRNA expression of APP was determined by RT-PCR. The AD cell model with over expression of APP was established successfully. The results of MTT and LDH assay showed that osthole had a protective effect on cells and alleviated cell damage. miR-101a-3p was identified as the differentially expressed miRNA, which was binding to the 3'-UTR of APP. Compared with APP group, the expression of APP and Aβ protein and APP mRNA increased in the miR-101a-3p inhibitor group (all P<0.01), while the expression of APP and Aβ protein and APP mRNA decreased in the cells with osthole treatment (all P<0.01). Osthole inhibits the expression of APP by up-regulating miR-101a-3p in AD cell model.

"Lipid raft aging" in the human frontal cortex during nonpathological aging: gender influences and potential implicationsin Alzheimer's disease.

Lipid rafts are highly dynamic membrane domains featured by distinctive biochemical composition and physicochemical properties compared with the surrounding plasma membrane. These microstructures are associated not only with cellular signaling and communication in normal nerve cells but also with pathological processing of amyloid precursor protein in Alzheimer's disease. Using lipid rafts isolated from human frontal cortex in nondemented subjects aging 24 to 85years, we demonstrate here that lipid structure of lipid rafts undergo significant alterations of specific lipid classes and phospholipid-bound fatty acids as brain cortex correlating with aging. Main changes affect levels of plasmalogens, polyunsaturated fatty acids (especially docosahexaenoic acid and arachidonic acid), total polar lipids (mainly phosphatidylinositol, sphingomyelin, sulfatides, and cerebrosides), and total neutral lipids (particularly cholesterol and sterol esters). Besides, relevant relationships between main fatty acids and/or lipid classes were altered in an age-related manner. This "lipid raft aging" exhibits clear gender differences and appear to be more pronounced in women than in men, especially in older (postmenopausal) women. The outcomes led us to conclude that human cortical lipid rafts are modified by aging in a gender-dependent fashion. Given the central role of bilayer lipid matrix in lipid rafts functionality and neuronal signaling, we hypothesize that these findings might underlie the higher prevalence of cognitive decline evolving toward Alzheimer's disease in postmenopausal women.

Human Brain-Derived Aβ Oligomers Bind to Synapses and Disrupt Synaptic Activity in a Manner That Requires APP.

Compelling genetic evidence links the amyloid precursor protein (APP) to Alzheimer's disease (AD) and several theories have been advanced to explain the relationship. A leading hypothesis proposes that a small amphipathic fragment of APP, the amyloid β-protein (Aβ), self-associates to form soluble aggregates that impair synaptic and network activity. Here, we used the most disease-relevant form of Aβ, protein isolated from AD brain. Using this material, we show that the synaptotoxic effects of Aβ depend on expression of APP and that the Aβ-mediated impairment of synaptic plasticity is accompanied by presynaptic effects that disrupt the excitatory/inhibitory (E/I) balance. The net increase in the E/I ratio and inhibition of plasticity are associated with Aβ localizing to synapses and binding of soluble Aβ aggregates to synapses requires the expression of APP. Our findings indicate a role for APP in AD pathogenesis beyond the generation of Aβ and suggest modulation of APP expression as a therapy for AD.SIGNIFICANCE STATEMENT Here, we report on the plasticity-disrupting effects of amyloid β-protein (Aβ) isolated from Alzheimer's disease (AD) brain and the requirement of amyloid precursor protein (APP) for these effects. We show that Aβ-containing AD brain extracts block hippocampal LTP, augment glutamate release probability, and disrupt the excitatory/inhibitory balance. These effects are associated with Aβ localizing to synapses and genetic ablation of APP prevents both Aβ binding and Aβ-mediated synaptic dysfunctions. Our results emphasize the importance of APP in AD and should stimulate new studies to elucidate APP-related targets suitable for pharmacological manipulation.

NeuronRead, an open source semi-automated tool for morphometric analysis of phase contrast and fluorescence neuronal images.

Neurons are specialized cells of the Central Nervous System whose function is intricately related to the neuritic network they develop to transmit information. Morphological evaluation of this network and other neuronal structures is required to establish relationships between neuronal morphology and function, and may allow monitoring physiological and pathophysiologic alterations. Fluorescence-based microphotographs are the most widely used in cellular bioimaging, but phase contrast (PhC) microphotographs are easier to obtain, more affordable, and do not require invasive, complicated and disruptive techniques. Despite the various freeware tools available for fluorescence-based images analysis, few exist that can tackle the more elusive and harder-to-analyze PhC images. To surpass this, an interactive semi-automated image processing workflow was developed to easily extract relevant information (e.g. total neuritic length, average cell body area) from both PhC and fluorescence neuronal images. This workflow, named 'NeuronRead', was developed in the form of an ImageJ macro. Its robustness and adaptability were tested and validated on rat cortical primary neurons under control and differentiation inhibitory conditions. Validation included a comparison to manual determinations and to a golden standard freeware tool for fluorescence image analysis. NeuronRead was subsequently applied to PhC images of neurons at distinct differentiation days and exposed or not to DAPT, a pharmacological inhibitor of the γ-secretase enzyme, which cleaves the well-known Alzheimer's amyloid precursor protein (APP) and the Notch receptor. Data obtained confirms a neuritogenic regulatory role for γ-secretase products and validates NeuronRead as a time- and cost-effective useful monitoring tool.

Amyloid precursor protein and endosomal-lysosomal dysfunction in Alzheimer's disease: inseparable partners in a multifactorial disease.

Abnormalities of the endosomal-lysosomal network (ELN) are a signature feature of Alzheimer's disease (AD). These include the earliest known cytopathology that is specific to AD and that affects endosomes and induces the progressive failure of lysosomes, each of which are directly linked by distinct mechanisms to neurodegeneration. The origins of ELN dysfunction and β-amyloidogenesis closely overlap, which reflects their common genetic basis, the established early involvement of endosomes and lysosomes in amyloid precursor protein (APP) processing and clearance, and the pathologic effect of certain APP metabolites on ELN functions. Genes that promote β-amyloidogenesis in AD (APP, PSEN1/2, and APOE4) have primary effects on ELN function. The importance of primary ELN dysfunction to pathogenesis is underscored by the mutations in more than 35 ELN-related genes that, thus far, are known to cause familial neurodegenerative diseases even though different pathogenic proteins may be involved. In this article, I discuss growing evidence that implicates AD gene-driven ELN disruptions as not only the antecedent pathobiology that underlies β-amyloidogenesis but also as the essential partner with APP and its metabolites that drive the development of AD, including tauopathy, synaptic dysfunction, and neurodegeneration. The striking amelioration of diverse deficits in animal AD models by remediating ELN dysfunction further supports a need to integrate APP and ELN relationships, including the role of amyloid-β, into a broader conceptual framework of how AD arises, progresses, and may be effectively therapeutically targeted.-Nixon, R. A. Amyloid precursor protein and endosomal-lysosomal dysfunction in Alzheimer's disease: inseparable partners in a multifactorial disease.

Amyloid precursor like protein-1 promotes JNK-mediated cell migration in Drosophila.

The amyloid precursor like protein-1 (APLP1) is a member of the amyloid precursor protein (APP) family in mammals. While many studies have been focused on the pathologic role of APP in Alzheimer's disease, the physiological functions of APLP1 have remained largely elusive. Here we report that ectopic expression of APLP1 in Drosophila induces cell migration, which is suppressed by the loss of JNK signaling and enhanced by the gain of JNK signaling. APLP1 activates JNK signaling through phosphorylation of JNK, which up-regulates the expression of matrix metalloproteinase MMP1 required for basement membranes degradation and promotes actin remodeling essential for cell migration. Our data thus provide the first in vivo evidence for a cell-autonomous role of APLP1 protein in migration.

Crosstalk between angiotensin and the nonamyloidogenic pathway of Alzheimer's amyloid precursor protein

The association between hypertension and an increased risk for Alzheimer's disease (AD) and dementia is well established. Many data suggest that modulation of the renin-angiotensin system may be meaningful for the prevention and therapy of neurodegenerative disorders, in particular AD. Proteolytic cleavage of the amyloid precursor protein (APP) by α-secretase precludes formation of neurotoxic Aβ peptides and is expected to counteract the development of AD. An established approach for the up-regulation of α-secretase cleavage is the activation of G protein-coupled receptors (GPCRs). Therefore, our study aimed to analyze whether stimulation of angiotensin AT1 or AT2 receptors stably expressed in HEK cells influence the nonamyloidogenic pathway of APP processing. Treatment of both receptors with angiotensin II clearly showed that only activation of the AT1 receptor increased several fold the α-secretase-mediated shedding of APP. This effect was completely abolished by treatment with the AT1 receptor-specific antagonist telmisartan. Using the BIM-46187 inhibitor, we demonstrate that the Gαq protein-mediated pathway is involved in this stimulation process. Stimulation of AT1 receptors with the β-arrestin-biased agonist SII was ineffective regarding α-secretase-mediated APP shedding. This result discloses that only the G protein-dependent pathway is involved in the Ang II-induced APP shedding. Blocking of Gβγ subunits by the inhibitor gallein completely prevented constitutive and Ang II-induced APP shedding. Our findings provide evidence that induction of APP shedding via Ang II/AT1 receptor stimulation is effected by G protein activation with Gβγ subunits playing important roles.