scholarly journals Modulation of Gamma-Secretase for the Treatment of Alzheimer's Disease

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Barbara Tate ◽  
Timothy D. McKee ◽  
Robyn M. B. Loureiro ◽  
Jo Ann Dumin ◽  
Weiming Xia ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Gamma Secretase ◽  
Synaptic Loss ◽  
App Processing ◽  
Protein Substrates ◽  
Secretase Activity ◽  
Small Molecule Modulators ◽  
Multiple Chemical

The Amyloid Hypothesis states that the cascade of events associated with Alzheimer's disease (AD)—formation of amyloid plaques, neurofibrillary tangles, synaptic loss, neurodegeneration, and cognitive decline—are triggered by Aβpeptide dysregulation (Kakuda et al., 2006, Sato et al., 2003, Qi-Takahara et al., 2005). Sinceγ-secretase is critical for Aβproduction, many in the biopharmaceutical community focused onγ-secretase as a target for therapeutic approaches for Alzheimer's disease. However, pharmacological approaches to controlγ-secretase activity are challenging because the enzyme has multiple, physiologically critical protein substrates. To lower amyloidogenic Aβpeptides without affecting otherγ-secretase substrates, the epsilon (ε) cleavage that is essential for the activity of many substrates must be preserved. Small molecule modulators ofγ-secretase activity have been discovered that spare theεcleavage of APP and other substrates while decreasing the production of Aβ42. Multiple chemical classes ofγ-secretase modulators have been identified which differ in the pattern of Aβpeptides produced. Ideally, modulators will allow theεcleavage of all substrates while shifting APP cleavage from Aβ42and other highly amyloidogenic Aβpeptides to shorter and less neurotoxic forms of the peptides without altering the total Aβpool. Here, we compare chemically distinct modulators for effects on APP processing andin vivoactivity.

scholarly journals Modeling the β secretase cleavage site and humanizing Amyloid-Beta Precursor Protein in rat and mouse to study Alzheimer Disease.

2020 ◽  
Author(s):  
Lutgarde Serneels ◽  
Dries T'Syen ◽  
Laura Perez-Benito ◽  
Tom Theys ◽  
Bart De Strooper
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amino Acid ◽  
Alzheimer Disease ◽  
Early Onset ◽  
Computational Modelling ◽  
Original Strain ◽  
Rodent Models ◽  
App Processing

Abstract Background Three amino acid differences between rodent and human APP affect medically important features including β-secretase cleavage of APP and aggregation of the Aβ peptide(1–3). Most rodent models for Alzheimer’s disease (AD) are therefore based on the human APP sequence expressed from artificial mini-genes randomly inserted in the rodent genome. While these models mimic rather well biochemical aspects of the disease such as Aβ-aggregation, they are also prone to overexpression artifacts and to complex phenotypical alterations due to genes affected in or close to the insertion sites of the mini-genes(4,5). Knock-in strategies introducing clinical mutants in a humanized endogenous rodent APP sequence(6) represent useful improvements, but need to be compared with appropriate humanized wild type (WT) mice.Methods Computational modelling of the human β-CTF bound to BACE1 was used to study the differential processing of rodent and human APP. We humanized the three pivotal residues G676R, F681Y and R684H (labeled according to the human APP770 isoform) in the mouse as well as in the rat by a CRISPR-Cas9 approach. These new models, termed mouse and rat App hu/hu , express APP from the endogenous promotor. We also introduced the early-onset familial Alzheimer’s disease (FAD) mutation M139T into the endogenous Rat Psen 1 gene.Results We show that the three amino acid substitutions in the rodent sequence lower the affinity of APP substrate for BACE1 cleavage. The effect on β-secretase processing was confirmed as both humanized rodent models produce three times more (human) Aβ compared to their WT rodent original strain. These models represent suitable controls or starting points for studying the effect of transgenes or knock-in mutations on APP processing(6). We introduced the early-onset familial Alzheimer disease (FAD) mutation M139T into the endogenous Rat Psen 1 gene and provide an initial characterization of Aβ processing in this novel rat AD model.Conclusion The different humanized APP models (rat and mouse) expressing human Aβ and PSEN1 M139T are valuable controls to study APP processing in vivo and allow to implement the use of human Aβ Elisa which is more sensitive than their rodent counterpart. These animals will be made available to the research community.

scholarly journals Neuronal aging potentiates beta-amyloid generation via amyloid precursor protein endocytosis

2019 ◽  
Author(s):  
Tatiana Burrinha ◽  
Ricardo Gomes ◽  
Ana Paula Terrasso ◽  
Cláudia Guimas Almeida
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Precursor Protein ◽  
Precursor Protein ◽  
App Processing ◽  
Early Endosomes ◽  
Primary Mouse ◽  
Β Amyloid ◽  
Aβ Production

AbstractAging increases the risk of Alzheimer’s disease (AD). During normal aging synapses decline and β-Amyloid (Aβ) accumulates. An Aβ defective clearance with aging is postulated as responsible for Aβ accumulation, although a role for increased Aβ production with aging can also lead to Aβ accumulation. To test this hypothesis, we established a long-term culture of primary mouse neurons that mimics neuronal aging (lysosomal lipofuscin accumulation and synapse decline). Intracellular endogenous Aβ42 accumulated in aged neurites due to increased amyloid-precursor protein (APP) processing. We show that APP processing is up-regulated by a specific age-dependent increase in APP endocytosis. Endocytosed APP accumulated in early endosomes that, in turn were found augmented in aged neurites. APP processing and early endosomes up-regulation was recapitulated in vivo. Finally, we found that inhibition of Aβ production reduced the decline in synapses in aged neurons. We propose that potentiation of APP endocytosis by neuronal aging increases Aβ production, which contributes to aging-dependent decline in synapses.SummaryHow aging increases the risk of Alzheimer’s disease is not clear. We show that normal neuronal aging increases the intracellular production of β-amyloid, due to an upregulation of the amyloid precursor protein endocytosis. Importantly, increased Aβ production contributes to the aging-dependent synapse loss.

scholarly journals In vivo imaging of synaptic loss in Alzheimer’s disease with [18F]UCB-H positron emission tomography

2019 ◽  
Vol 47 (2) ◽  
pp. 390-402 ◽  
Author(s):  
Christine Bastin ◽  
Mohamed Ali Bahri ◽  
François Meyer ◽  
Marine Manard ◽  
Emma Delhaye ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Positron Emission Tomography ◽  
In Vivo Imaging ◽  
Emission Tomography ◽  
Synaptic Loss ◽  
Positron Emission

Selecting cells with different Alzheimer's disease gamma-secretase activity using FACS. Differential effect of presenilin exon 9 deletion on gamma- and epsilon-cleavage

2003 ◽  
Vol 270 (3) ◽  
pp. 495-506 ◽  
Author(s):  
M. Fleur Sernee ◽  
Genevieve Evin ◽  
Janetta G. Culvenor ◽  
Jose A. Villadangos ◽  
Konrad Beyreuther ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Differential Effect ◽  
Gamma Secretase ◽  
Secretase Activity ◽  
Exon 9

scholarly journals In vivo measurement of widespread synaptic loss and associated tau accumulation in early Alzheimer’s disease

2020 ◽  
Vol 16 (S4) ◽  
Author(s):  
Adam P. Mecca ◽  
Ryan S. O'Dell ◽  
Ming‐Kai Chen ◽  
Mika Naganawa ◽  
Takuya Toyonaga ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Synaptic Loss ◽  
In Vivo Measurement ◽  
Early Alzheimer’S Disease

P3-225: Role of presenilin-dependent gamma-secretase activity in the control of P53-mediated cell death in Alzheimer's disease

2006 ◽  
Vol 2 ◽  
pp. S441-S442
Author(s):  
Cristine Alves da Costa ◽  
Claire Sunyach ◽  
Raphaelle Pardossi-Piquard ◽  
Bruno Vincent ◽  
Jean Sevalle ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cell Death ◽  
Gamma Secretase ◽  
Secretase Activity

scholarly journals Loss of Hsp110 Leads to Age-Dependent Tau Hyperphosphorylation and Early Accumulation of Insoluble Amyloid β

2010 ◽  
Vol 30 (19) ◽  
pp. 4626-4643 ◽  
Author(s):  
Binnur Eroglu ◽  
Demetrius Moskophidis ◽  
Nahid F. Mivechi
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Critical Role ◽  
Amyloid Β ◽  
Tau Phosphorylation ◽  
Critical Function ◽  
App Processing ◽  
Phosphorylation State ◽  
Brain Extracts

ABSTRACT Accumulation of tau into neurofibrillary tangles is a pathological consequence of Alzheimer's disease and other tauopathies. Failures of the quality control mechanisms by the heat shock proteins (Hsps) positively correlate with the appearance of such neurodegenerative diseases. However, in vivo genetic evidence for the roles of Hsps in neurodegeneration remains elusive. Hsp110 is a nucleotide exchange factor for Hsp70, and direct substrate binding to Hsp110 may facilitate substrate folding. Hsp70 complexes have been implicated in tau phosphorylation state and amyloid precursor protein (APP) processing. To provide evidence for a role for Hsp110 in central nervous system homeostasis, we have generated hsp110 − / − mice. Our results show that hsp110 − / − mice exhibit accumulation of hyperphosphorylated-tau (p-tau) and neurodegeneration. We also demonstrate that Hsp110 is in complexes with tau, other molecular chaperones, and protein phosphatase 2A (PP2A). Surprisingly, high levels of PP2A remain bound to tau but with significantly reduced activity in brain extracts from aged hsp110 − / − mice compared to brain extracts from wild-type mice. Mice deficient in the Hsp110 partner (Hsp70) also exhibit a phenotype comparable to that of hsp110 − / − mice, confirming a critical role for Hsp110-Hsp70 in maintaining tau in its unphosphorylated form during aging. In addition, crossing hsp110 − / − mice with mice overexpressing mutant APP (APPβsw) leads to selective appearance of insoluble amyloid β42 (Aβ42), suggesting an essential role for Hsp110 in APP processing and Aβ generation. Thus, our findings provide in vivo evidence that Hsp110 plays a critical function in tau phosphorylation state through maintenance of efficient PP2A activity, confirming its role in pathogenesis of Alzheimer's disease and other tauopathies.

Understanding the function of ABCA7 in Alzheimer's disease

2015 ◽  
Vol 43 (5) ◽  
pp. 920-923 ◽  
Author(s):  
Hongyun Li ◽  
Tim Karl ◽  
Brett Garner
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Association Studies ◽  
Chinese Hamster Ovary Cells ◽  
Amyloid Β ◽  
Mutant Form ◽  
Genome Wide Association Studies ◽  
App Processing ◽  
The Brain

ATP-binding cassette transporter A7 (ABCA7) is highly expressed in the brain. Recent genome-wide association studies (GWAS) identify ABCA7 single nt polymorphisms (SNPs) that increase Alzheimer's disease (AD) risk. It is now important to understand the true function of ABCA7 in the AD context. We have begun to address this using in vitro and in vivo AD models. Our initial studies showed that transient overexpression of ABCA7 in Chinese hamster ovary cells stably expressing human amyloid precursor protein (APP) resulted in an approximate 50% inhibition in the production of the AD-related amyloid-β (Aβ) peptide as compared with mock-transfected cells. This increased ABCA7 expression was also associated with alterations in other markers of APP processing and an accumulation of cellular APP. To probe for a function of ABCA7 in vivo, we crossed Abca7−/− mice with J20 mice, an amyloidogenic transgenic AD mouse model [B6.Cg-Tg(PDGFB-APPSwInd)20Lms/J] expressing a mutant form of human APP bearing both the Swedish (K670N/M671L) and Indiana (V717F) familial AD mutations. We found that ABCA7 loss doubled insoluble Aβ levels and amyloid plaques in the brain. This did not appear to be related to changes in APP processing (C-terminal fragment analysis), which led us to assess other mechanism by which ABCA7 may modulate Aβ homoeostasis. As we have shown that microglia express high levels of ABCA7, we examined a role for ABCA7 in the phagocytic clearance of Aβ. Our data indicated that the capacity for bone marrow-derived macrophages derived from Abca7−/− mice to phagocytose Aβ was reduced by 51% compared with wild-type (WT) mice. This suggests ABCA7 plays a role in the regulation of Aβ homoeostasis in the brain and that this may be related to Aβ clearance by microglia.

scholarly journals Nutrient signaling pathways regulate amyloid clearance and synaptic loss in Alzheimer’s disease

2020 ◽  
Author(s):  
Mrityunjoy Mondal ◽  
Jitin Bali ◽  
Makis Tzioras ◽  
Rosa C. Paolicelli ◽  
Ali Jawaid ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Β ◽  
Pathological State ◽  
Amyloid Formation ◽  
Synaptic Loss ◽  
Synapse Loss ◽  
Human Neurons ◽  
Nutrient Signaling

SummaryExtra-cellular accumulation of Amyloid-β (Aβ) plaques is causatively associated with Alzheimer’s disease (AD). However, mechanisms that mediate the pre-pathological state of amyloid plaque formation remain elusive. Here, using paired RNAi and kinase inhibitor screens, we discovered that AKT-mediated insulin/nutrient signaling suppresses lysosomal clearance of Aβ and promotes amyloid formation. This mechanism is cell-autonomous and functions in multiple systems, including iPSC-derived human neurons and in vivo. Nutrient signaling regulates amyloid formation via distinct lysosomal functional mechanisms, while enhanced amino acid signaling promotes amyloid formation by transcriptionally suppressing lysosome biogenesis, and high intracellular cholesterol levels suppress lysosomal clearance of amyloid by increasing the number of non-functional lysosomes. The nutrient signaling pathway, present in both neurons and microglia, regulates lysosomal clearance of amyloid and microglia mediated synapse loss, both in vitro and in vivo. Clinically, older hyperlipidemic patients showed less synapse loss through microglia and performed better in cognitive tests. Thus, our results reveal a bi-partite cellular quality control system regulated by the insulinnutrient signaling that in neurons regulates Aβ peptide clearance and in microglia regulates synaptic loss, both processes causally associated with AD. Our results also caution against reducing amyloid through such processes as this might also result in synapse loss.

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