Biology subjects

Sasaguri, H.

Publications and source records attributed to Sasaguri, H..

6 recordsLinked to original sources

bioRxiv2021

An isogenic panel of single App knock-in mouse models of Alzheimer's disease confers differential profiles of β-secretase inhibition and endosomal abnormalities

We previously developed single App knock-in mouse models of Alzheimers disease (AD) that harbor the Swedish and Beyreuther/Iberian mutations with or without the Arctic mutation (AppNL- G-F and AppNL-F mice). These models showed the development of amyloid {beta} peptide (A{beta}) pathology, neuroinflammation and cognitive impairment with aging. We have now generated App knock-in mice devoid of the Swedish mutations (AppG-F mice) and some additional mutants to address the following two questions: [1] Do the Swedish mutations influence the mode of {beta}-secretase inhibitor action in vivo? [2] Does the quantity of C-terminal fragment of amyloid precursor protein (APP) generated by {beta}-secretase (CTF-{beta}) affect endosomal properties as previously reported as well as other pathological events? A{beta} pathology was exhibited by AppG-F mice from 6 to 8 months of age, and was accompanied by microglial and astrocyte activation. We found that a {beta}-secretase inhibitor, verubecestat, inhibited A{beta} production in AppG-F mice, but not in AppNL-G-F mice, indicating that the AppG-F mice are more suitable for preclinical studies of {beta}-secretase inhibition given that most AD patients do not carry Swedish mutations. We also found that the quantity of CTF-{beta} generated by various App knock-in mutants failed to correlate with endosomal alterations or enlargement, implying that CTF-{beta}, endosomal abnormalities, or both are unlikely to play a major role in AD pathogenesis. This is the first AD mouse model ever described that recapitulates amyloid pathology in the brain without the presence of Swedish mutations and without relying on the overexpression paradigm. Thus, experimental comparisons between different App knock-in mouse lines will potentially provide new insights into our understanding of the etiology of AD.

neuroscience↗

bioRxiv2021

Neprilysin-sensitive amyloidogenic Aβ versus IDE-sensitive soluble Aβ: a probable mechanistic cause for sporadic Alzheimer's disease

Neprilysin (NEP) and insulin-degrading enzyme (IDE) are considered the two major catabolic enzymes that degrade amyloid {beta} peptide (A{beta}), the primary cause of Alzheimers disease (AD). However, their roles in A{beta} metabolism in vivo have never been compared in an impartial and side-by-side manner. Here, we crossbred single App knock-in mice with NEP (Mme) KO mice and with IDE (Ide) KO mice to generate double mutants that were analyzed for their biochemical and A{beta} pathology properties. We found that NEP is responsible for the metabolism of amyloidogenic insoluble A{beta} whereas IDE affects soluble A{beta}. A deficiency of NEP, but not of IDE, augmented the formation of A{beta} plaques, dystrophic neurites, and astrocytic and microglial activation, all of which are key pathological events in the development of AD. In addition, a deficiency of NEP had no significant impact on the levels of various neuropeptides (somatostatin, substance P, cholecystokinin, and neuropeptide Y), well known to be in vitro substrates for NEP, presumably because NEP is expressed in secretory vesicles and on the presynaptic membranes of excitatory neurons while most if not all neuropeptides are secreted from inhibitory neurons. This argues against the concern that NEP up-regulation for treatment of preclinical AD would reduce the levels of these neuropeptides. These findings indicate that NEP relatively selectively degrades A{beta} in the brain. Whereas familial AD (FAD) is unambiguously caused by an increased anabolism of A{beta}, and of A{beta} 42 and A{beta} 43 in particular, the anabolism of A{beta} appears unaffected before its deposition in the brain that subsequently leads to the onset of sporadic AD (SAD). These observations thus suggest that NEP-sensitive amyloidogenic A{beta} likely plays a primary pathogenic role in the etiology of SAD. Our findings are consistent with the aging-dependent decline of NEP expression in human brain and with recent genome-wide association studies (GWAS) indicating that variants of the gene encoding NEP (MME) are associated with the risk of SAD development. Taken together, our results imply that the aging-associated decrease in NEP expression is a primary cause of SAD and could thus be a target for the treatment of preclinical AD once other factors such as apolipoprotein E genotypes have also been considered.

neuroscience↗

bioRxiv2021

New App knock-in mice that accumulate wild-type human Aβ as rapidly as AppNL-G-F mice exhibit intensive cored plaque pathology and neuroinflammation.

We previously developed single App knock-in mouse models of Alzheimers disease (AD), harboring the Swedish and Beyreuther/Iberian mutations with or without the Arctic mutation (AppNL-G-F and AppNL-F mice). These models showed amyloid {beta} peptide (A{beta}) pathology, neuroinflammation and cognitive impairment in an age-dependent manner. The former line exhibits extensive pathology as early as 6 months but is unsuitable for investigating A{beta} metabolism and clearance because the Arctic mutation renders A{beta} resistant to proteolytic degradation and prone to aggregation. In particular, it is inapplicable to preclinical immunotherapy studies due to its discrete affinity for anti-A{beta} antibodies. The weakness of the latter model is that it may take as long as 18 months for the pathology to become prominent. We have thus generated a new model that exhibits early deposition of wild-type human A{beta} by crossbreeding the AppNL-F line with the Psen1P117L/WT line. We show that the effects of the pathogenic mutations in the App and Psen1 genes are additive or synergistic. This new mouse model showed more cored plaque pathology and neuroinflammation than AppNL-G-F mice and will help accelerate the development of disease-modifying therapies to treat preclinical AD.

neuroscience↗

bioRxiv2020

α-Endosulfine regulates amyloid β42 via the modulation of neprilysin activity

The neuropeptide somatostatin (SST) regulates amyloid {beta} peptide (A{beta}) catabolism by enhancing neprilysin (NEP)-catalyzed proteolytic degradation. However, the mechanism by which SST regulates NEP activity remains unclear. Here we report the identification by differential proteomics of -endosulfine (ENSA), an endogenous ligand of the ATP-sensitive potassium (KATP) channel, as a negative regulator of NEP activity downstream of SST signaling. Genetic deficiency of ENSA resulted in enhanced NEP activity and decreased A{beta} deposition in the brains of wild-type and Alzheimers disease (AD) model mice. Pharmacological intervention to increase the probability of KATP channel opening reduced A{beta} deposition in AD model mice. Our findings provide new insights into possible mechanisms to prevent AD.

neuroscience↗

bioRxiv2020

A non-human primate model of familial Alzheimer's disease

Alzheimers disease (AD) is a major cause of dementia, with the number of patients with this condition anticipated to exceed 50 million worldwide in the near future. Despite extensive research efforts, no effective measures are available to facilitate the prevention or treatment of AD, which is due in part to a lack of animal models able to closely replicate a human-like disease state. Here, we describe the generation of three mutant marmoset individuals in which exon 9 of PSEN1 gene product has been deleted (PSEN1-{Delta}E9). Such {Delta}E9 mutations have been reported to cause early on-set familial AD (references1-5). We used Transcription Activator-Like Effector Nuclease (TALEN) to destroy the 3 splice site of exon 9 in the marmoset PSEN1 gene. To this end, TALEN exhibits high genome-editing efficacy, generates few off-target effects, and produces minimal mosaicism. Indeed, whole genome sequencing and other analyses illustrated an absence of off-target effects and an apparent absence of mosaicism. Fibroblasts obtained from newborn marmosets exhibited uncleaved full-length presenilin 1 protein (PS1) caused by the perturbation of PS1 endoproteolysis as well as an increased ratio of A{beta}42/A{beta}40 production, a signature of familial AD pathogenesis. To our knowledge, this is the first non-human primate model of familial AD. We intend to make our marmoset model available to the research community to facilitate the global fight against AD.

neuroscience↗

bioRxiv2020

Somatostatin receptor subtypes 1 and 4 redundantly regulate neprilysin, the major amyloid beta-degrading enzyme, in brain

Alzheimers disease (AD) brains are characterized by increased levels of the pathogenic amyloid beta (A{beta}) peptide, which accumulates into extracellular plaques. Finding a way to lower A{beta} levels is fundamental for the prevention and treatment of AD. Neprilysin is the major A{beta} degrading enzyme which is regulated by the neuropeptide somatostatin. Here we used a combination of in vitro and in vivo approaches to identify the subtype specificity of the five somatostatin receptors (SSTs) expressed in the brain, involved in the regulation of neprilysin. Using a battery of Sst double knockout (dKO) mice we show that neprilysin is regulated by SST1 and SST4 in a redundant manner. Sst1 and Sst4 dKO mice exhibit a specific decrease of presynaptic neprilysin in the Lacunosum molecular layer. Moreover, a genetic deficiency of Sst1 and Sst4 in amyloid beta precursor protein (App) knock-in mice, an AD mouse model, aggravates the A{beta} pathology in the hippocampus. As a first proof of concept towards an A{beta}-lowering strategy involving neprilysin, we demonstrate that treatment with an agonist selective for SST1 and SST4 ameliorates the A{beta} pathology and improves cognition in the App knock-in AD mouse model.

neuroscience↗