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Project description:Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most frequent cause of dementia. The disease has a substantial genetic component comprising both highly penetrant familial mutations (APP, PSEN1 and PSEN2) and sporadic cases with complex genetic etiology. Mutations in APP and PSEN1/2 alter the proteolytic processing of APP to its metabolites, including Ab and APP Intracellular Domain (AICD). In this study, we use transgenic porcine models carrying the human APPsw and PSEN1M146I transgenes to demonstrate the pathobiological relevance of transcriptional regulation facilitated by APP and its AICD domain. Through molecular characterization of hippocampal tissue, we describe the differential expression of gene sets that cluster in molecular pathways with translational relevance to AD. We further identify phosphorylated and unphosphorylated AICD in differential complexes with proteins implicated in signal transduction and transcriptional regulation. Integrative genomic analysis of transcriptional changes in somatic cell cultures derived from pigs treated with g-secretase inhibitor demonstrates the importance of g-secretase APP processing in transcriptional regulation. Collectively, our data supports a model in which APP, and in particular its AICD domain, modulates gene networks associated with AD pathobiology through interaction with signaling proteins.
2024-02-04 | GSE254570 | GEO
Project description:Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most frequent cause of dementia. The disease has a substantial genetic component comprising both highly penetrant familial mutations (APP, PSEN1 and PSEN2) and sporadic cases with complex genetic etiology. Mutations in APP and PSEN1/2 alter the proteolytic processing of APP to its metabolites, including Ab and APP Intracellular Domain (AICD). In this study, we use transgenic porcine models carrying the human APPsw and PSEN1M146I transgenes to demonstrate the pathobiological relevance of transcriptional regulation facilitated by APP and its AICD domain. Through molecular characterization of hippocampal tissue, we describe the differential expression of gene sets that cluster in molecular pathways with translational relevance to AD. We further identify phosphorylated and unphosphorylated AICD in differential complexes with proteins implicated in signal transduction and transcriptional regulation. Integrative genomic analysis of transcriptional changes in somatic cell cultures derived from pigs treated with g-secretase inhibitor demonstrates the importance of g-secretase APP processing in transcriptional regulation. Collectively, our data supports a model in which APP, and in particular its AICD domain, modulates gene networks associated with AD pathobiology through interaction with signaling proteins.
2024-02-04 | GSE254548 | GEO
Project description:BackgroundA devastating aspect of Alzheimer's disease (AD) is the progressive deterioration of memory due to neuronal loss. Amyloid precursor protein (APP) occupies a central position in AD and APP-derived amyloid-beta (Abeta) peptides are thought to play a pivotal role in disease pathogenesis. Nonetheless, it is becoming clear that AD etiology is highly complex and that factors other than Abeta also contribute to AD pathogenesis. APP intracellular domain (AICD) is generated together with Abeta and we recently showed that AICD transgenic mice recapitulate pathological features of AD such as tau hyperphosphorylation, memory deficits and neurodegeneration without increasing the Abeta levels. Since impaired adult neurogenesis is shown to augment memory deficits in AD mouse models, here we examined the status of adult neurogenesis in AICD transgenic mice.Methodology/principal findingWe previously generated transgenic mice co-expressing 59-residue long AICD fragment and its binding partner Fe65. Hippocampal progenitor cell proliferation was determined by BrdU incorporation at 1.5, 3 and 12 months of age. Only male transgenic and their respective wilt type littermate control mice were used. We find age-dependent decrease in BrdU incorporation and doublecortin-positive cells in the dentate gyrus of AICD transgenic mice suggesting impaired adult neurogenesis. This deficit resulted from decreased proliferation and survival, whereas neuronal differentiation remained unaffected. Importantly, this impairment was independent of Abeta since APP-KO mice expressing AICD also exhibit reduced neurogenesis. The defects in adult neurogenesis are prevented by long-term treatment with the non-steroidal anti-inflammatory agents ibuprofen or naproxen suggesting that neuroinflammation is critically involved in impaired adult neurogenesis in AICD transgenic mice.Conclusion/significanceSince adult neurogenesis is crucial for spatial memory, which is particularly vulnerable in AD, these findings suggest that AICD can exacerbate memory defects in AD by impairing adult neurogenesis. Our findings further establish that AICD, in addition to Abeta, contributes to AD pathology and that neuroinflammation plays a much broader role in AD pathogenesis than previously thought.
| S-EPMC2912762 | biostudies-literature
Project description:The hypothesis that amyloid-beta (Abeta) peptides are the primary cause of Alzheimer's disease (AD) remains the best supported theory of AD pathogenesis. Yet, many observations are inconsistent with the hypothesis. Abeta peptides are generated when amyloid precursor protein (APP) is cleaved by presenilins, a process that also produces APP intracellular domain (AICD). We previously generated AICD-overexpressing transgenic mice that showed abnormal activation of GSK-3beta, a pathological feature of AD. We now report that these mice exhibit additional AD-like characteristics, including hyperphosphorylation and aggregation of tau, neurodegeneration and working memory deficits that are prevented by treatment with lithium, a GSK-3beta inhibitor. Consistent with its potential role in AD pathogenesis, we find AICD levels to be elevated in brains from AD patients. The in vivo findings that AICD can contribute to AD pathology independently of Abeta have important therapeutic implications and may explain some observations that are discordant with the amyloid hypothesis.
| S-EPMC2762847 | biostudies-literature
Project description:An increase in amyloid-β (Aβ) production is a major pathogenic mechanism associated with Alzheimer's disease (AD), but little is known about possible homeostatic control of the amyloidogenic pathway. Here we report that the amyloid precursor protein (APP) intracellular domain (AICD) downregulates Wiskott-Aldrich syndrome protein (WASP)-family verprolin homologous protein 1 (WAVE1 or WASF1) as part of a negative feedback mechanism to limit Aβ production. The AICD binds to the Wasf1 promoter, negatively regulates its transcription and downregulates Wasf1 mRNA and protein expression in Neuro 2a (N2a) cells. WAVE1 interacts and colocalizes with APP in the Golgi apparatus. Experimentally reducing WAVE1 in N2a cells decreased the budding of APP-containing vesicles and reduced cell-surface APP, thereby reducing the production of Aβ. WAVE1 downregulation was observed in mouse models of AD. Reduction of Wasf1 gene expression dramatically reduced Aβ levels and restored memory deficits in a mouse model of AD. A decrease in amounts of WASF1 mRNA was also observed in human AD brains, suggesting clinical relevance of the negative feedback circuit involved in homeostatic regulation of Aβ production.
| S-EPMC4560977 | biostudies-literature
Project description:Alzheimer's disease (AD) is characterized by an accumulation of Amyloid-? (A?), released by sequential proteolytic processing of the amyloid precursor protein (APP) by ? - and ?-secretase. A? peptides can aggregate, leading to toxic A? oligomers and amyloid plaque formation. A? accumulation is not only dependent on de novo synthesis but also on A? degradation. Neprilysin (NEP) is one of the major enzymes involved in A? degradation. Here we investigate the molecular mechanism of NEP regulation, which is up to now controversially discussed to be affected by APP processing itself. We found that NEP expression is highly dependent on the APP intracellular domain (AICD), released by APP processing. Mouse embryonic fibroblasts devoid of APP processing, either by the lack of the catalytically active subunit of the ?-secretase complex [presenilin (PS) 1/2] or by the lack of APP and the APP-like protein 2 (APLP2), showed a decreased NEP expression, activity and protein level. Similar results were obtained by utilizing cells lacking a functional AICD domain (APP?CT15) or expressing mutations in the genes encoding for PS1. AICD supplementation or retransfection with an AICD encoding plasmid could rescue the down-regulation of NEP further strengthening the link between AICD and transcriptional NEP regulation, in which Fe65 acts as an important adaptor protein. Especially AICD generated by the amyloidogenic pathway seems to be more involved in the regulation of NEP expression. In line, analysis of NEP gene expression in vivo in six transgenic AD mouse models (APP and APLP2 single knock-outs, APP/APLP2 double knock-out, APP-swedish, APP-swedish/PS1?exon9, and APP?CT15) confirmed the results obtained in cell culture. In summary, in the present study we clearly demonstrate an AICD-dependent regulation of the A?-degrading enzyme NEP in vitro and in vivo and elucidate the underlying mechanisms that might be beneficial to develop new therapeutic strategies for the treatment of AD.
| S-EPMC4443740 | biostudies-literature
Project description:: Brains that are affected by Alzheimer's disease (AD) are characterized by the overload of extracellular amyloid ? (A?) peptides, but recent data from cellular and animal models propose that A? deposition is preceded by intraneuronal accumulation of the direct precursor of A?, C99. These studies indicate that C99 accumulation firstly occurs within endosomal and lysosomal compartments and that it contributes to early-stage AD-related endosomal-lysosomal-autophagic defects. Our previous work also suggests that C99 accumulation itself could be a consequence of defective lysosomal-autophagic degradation. Thus, in the present study, we analyzed the influence of the overexpression of the transcription factor EB (TFEB), a master regulator of autophagy and lysosome biogenesis, on C99 accumulation occurring in both AD cellular models and in the triple-transgenic mouse model (3xTgAD). In the in vivo experiments, TFEB overexpression was induced via adeno-associated viruses (AAVs), which were injected either into the cerebral ventricles of newborn mice or administrated at later stages (3 months of age) by stereotaxic injection into the subiculum. In both cells and the 3xTgAD mouse model, exogenous TFEB strongly reduced C99 load and concomitantly increased the levels of many lysosomal and autophagic proteins, including cathepsins, key proteases involved in C99 degradation. Our data indicate that TFEB activation is a relevant strategy to prevent the accumulation of this early neurotoxic catabolite.
| S-EPMC7291113 | biostudies-literature
Project description:Cleavage of amyloid precursor protein (APP) by ?- and ?-secretase generates amyloid-? (A?) and APP intracellular domain (AICD) peptides. Presenilin (PS) 1 or 2 is the catalytic component of the ?-secretase complex. Mitochondrial dysfunction is an established phenomenon in Alzheimer's disease (AD), but the causes and role of PS1, APP, and APP's cleavage products in this process are largely unknown. We studied the effect of these AD-associated molecules on mitochondrial features. Using cells deficient in PSs expression, expressing human wild-type PS1, or PS1 familial AD (FAD) mutants, we found that PS1 affects mitochondrial energy metabolism (ATP levels and oxygen consumption) and expression of mitochondrial proteins. These effects were associated with enhanced expression of the mitochondrial master transcriptional coactivator PGC-1? and its target genes. Importantly, PS1-FAD mutations decreased PS1's ability to enhance PGC-1? mRNA levels. Analyzing the effect of APP and its ?-secretase-derived cleavage products A? and AICD on PGC-1? expression showed that APP and AICD increase PGC-1? expression. Accordingly, PGC-1? mRNA levels in cells deficient in APP/APLP2 or expressing APP lacking its last 15 amino acids were lower than in control cells, and treatment with AICD, but not with A?, enhanced PGC-1? mRNA levels in these and PSs-deficient cells. In addition, knockdown of the AICD-binding partner Fe65 reduced PGC-1? mRNA levels. Importantly, APP/AICD increases PGC-1? expression also in the mice brain. Our results therefore suggest that APP processing regulates mitochondrial function and that impairments in the newly discovered PS1/APP/AICD/PGC-1? pathway may lead to mitochondrial dysfunction and neurodegeneration.
| S-EPMC4331788 | biostudies-literature
Project description:Amyloid precursor protein (APP) is cleaved by gamma-secretase to simultaneously generate amyloid beta (A?) and APP Intracellular Domain (AICD) peptides. A? plays a pivotal role in Alzheimer's disease (AD) pathogenesis but recent studies suggest that amyloid-independent mechanisms also contribute to the disease. We previously showed that AICD transgenic mice (AICD-Tg) exhibit AD-like features such as tau pathology, aberrant neuronal activity, memory deficits and neurodegeneration in an age-dependent manner. Since AD is a tauopathy and tau has been shown to mediate A?-induced toxicity, we examined the role of tau in AICD-induced pathological features. We report that ablating endogenous tau protects AICD-Tg mice from deficits in adult neurogenesis, seizure severity, short-term memory deficits and neurodegeneration. Deletion of tau restored abnormal phosphorylation of NMDA receptors, which is likely to underlie hyperexcitability and associated excitotoxicity in AICD-Tg mice. Conversely, overexpression of wild-type human tau aggravated receptor phosphorylation, impaired adult neurogenesis, memory deficits and neurodegeneration. Our findings show that tau is essential for mediating the deleterious effects of AICD. Since tau also mediates A?-induced toxic effects, our findings suggest that tau is a common downstream factor in both amyloid-dependent and-independent pathogenic mechanisms and therefore could be a more effective drug target for therapeutic intervention in AD.
| S-EPMC4961442 | biostudies-literature
Project description:Amyloid precursor protein (APP) is best known for its involvement in the pathogenesis of Alzheimer's disease. We have previously demonstrated that APP intracellular domain (AICD) regulates neurogenesis; however, the mechanisms underlying AICD-mediated regulation of neuronal differentiation are not yet fully characterized. Using genome-wide chromatin immunoprecipitation approaches, we found that AICD is specifically recruited to the regulatory regions of several microRNA genes, and acts as a transcriptional regulator for miR-663, miR-3648 and miR-3687 in human neural stem cells. Functional assays show that AICD negatively modulates neuronal differentiation through miR-663, a primate-specific microRNA. Microarray data further demonstrate that miR-663 suppresses the expression of multiple genes implicated in neurogenesis, including FBXL18 and CDK6. Our results indicate that AICD has a novel role in suppression of neuronal differentiation via transcriptional regulation of miR-663 in human neural stem cells.
| S-EPMC4669786 | biostudies-literature