Lysosomal dysfunction in Down syndrome is APP-dependent and mediated by APP-βCTF (C99)
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PROVIDER: PRJNA525687 | ENA |
REPOSITORIES: ENA
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Project description:Lysosomal failure underlies pathogenesis of numerous congenital neurodegenerative disorders and is an early and progressive feature of Alzheimer’s disease (AD) pathogenesis. Here, we report that lysosomal dysfunction in Down Syndrome (Trisomy 21) requires the extra gene copy of amyloid precursor protein (APP) and is mediated by the beta cleaved carboxy terminal fragment of APP (APP-βCTF, C99). In primary fibroblasts from individuals with Down Syndrome (DS), lysosomal degradation of autophagic and endocytic substrates is selectively impaired causing them to accumulate in enlarged autolysosomes/lysosomes. Direct measurements of lysosomal pH uncovered a significant elevation (0.6 units) associated with slowed LC3 turnover and the inactivation of cathepsin D (CTSD) and other lysosomal hydrolases known to be unstable or less active when lysosomal pH is persistently elevated. RNA sequencing analysis excluded a transcriptional contribution to hydrolase declines. Normalizing lysosome pH by delivering acidic nanoparticles to lysosomes ameliorated lysosomal deficits, implicating pH elevation as their primary basis. Cortical neurons cultured from the Ts2 mouse model of DS exhibited lysosomal deficits similar to those in DS cells. Lowering APP expression with siRNA or BACE1 inhibition reversed cathepsin deficits in both fibroblasts and neurons. Deleting one BACE1 allele from adult Ts2 mice had similar rescue effects in vivo. The modest elevation of endogenous APP-βCTF needed to disrupt lysosomal function in DS is relevant to sporadic AD where APP-βCTF, but not APP, is also elevated. Our results extend evidence that impaired lysosomal acidification drives progressive lysosomal failure in multiple forms of AD.
2019-05-30 | GSE127880 | GEO
Project description:Lysosomal failure underlies pathogenesis of numerous congenital neurodegenerative disorders and is an early and progressive feature of Alzheimer's disease (AD) pathogenesis. Here, we report that lysosomal dysfunction in Down ayndrome (trisomy 21), a neurodevelopmental disorder and form of early onset AD, requires the extra gene copy of amyloid precursor protein (APP) and is specifically mediated by the β cleaved carboxy terminal fragment of APP (APP-βCTF, C99). In primary fibroblasts from individuals with DS, lysosomal degradation of autophagic and endocytic substrates is selectively impaired, causing them to accumulate in enlarged autolysosomes/lysosomes. Direct measurements of lysosomal pH uncovered a significant elevation (0.6 units) as a basis for slowed LC3 turnover and the inactivation of cathepsin D and other lysosomal hydrolases known to be unstable or less active when lysosomal pH is persistently elevated. Normalizing lysosome pH by delivering acidic nanoparticles to lysosomes ameliorated lysosomal deficits, whereas RNA sequencing analysis excluded a transcriptional contribution to hydrolase declines. Cortical neurons cultured from the Ts2 mouse model of DS exhibited lysosomal deficits similar to those in DS cells. Lowering APP expression with siRNA or BACE1 inhibition reversed cathepsin deficits in both fibroblasts and neurons. Deleting one Bace1 allele from adult Ts2 mice had similar rescue effects in vivo The modest elevation of endogenous APP-βCTF needed to disrupt lysosomal function in DS is relevant to sporadic AD where APP-βCTF, but not APP, is also elevated. Our results extend evidence that impaired lysosomal acidification drives progressive lysosomal failure in multiple forms of AD.SIGNIFICANCE STATEMENT Down syndrome (trisomy 21) (DS) is a neurodevelopmental disorder invariably leading to early-onset Alzheimer's disease (AD). We showed in cells from DS individuals and neurons of DS models that one extra copy of a normal amyloid precursor protein (APP) gene impairs lysosomal acidification, thereby depressing lysosomal hydrolytic activities and turnover of autophagic and endocytic substrates, processes vital to neuronal survival. These deficits, which were reversible by correcting lysosomal pH, are mediated by elevated levels of endogenous β-cleaved carboxy-terminal fragment of APP (APP-βCTF). Notably, similar endosomal-lysosomal pathobiology emerges early in sporadic AD, where neuronal APP-βCTF is also elevated, underscoring its importance as a therapeutic target and underscoring the functional and pathogenic interrelationships between the endosomal-lysosomal pathway and genes causing AD.
| S-EPMC6607756 | biostudies-literature
Project description:Early-onset Alzheimer’s disease-like pathology in Down syndrome (DS, trisomy 21) is commonly attributed to an increased dosage of the amyloid precursor protein (APP) gene. To test this central tenet of the amyloid-cascade hypothesis we deleted the supernumerary copy of the APP gene in trisomic DS iPSC, or upregulated APP expression in euploid human pluripotent stem cell lines with dCas9-VP64, and subjected these lines to prolonged cortical neural differentiation. Our data reveal that increased APP gene dosage and expression is necessary and sufficient for increased beta-amyloid production and pyroglutamate(E3)-containing plaque deposition, but is neither sufficient nor required for tau hyperphosphorylation, neurofibrillary tangle formation, or increased oxidative stress-induced apoptosis in neurons. Transcriptome comparisons of the isogenic neurons demonstrates that the supernumerary APP gene copy has profound temporally-modulated genome-wide effects on gene expression during differentiation and maturation of DS neuronal cultures that link APP function to regulation of genes involved in neuronal synaptic function and outgrowth of neuronal processes. Collectively, our data reveal that APP plays an important role in the amyloidogenic aspects of Alzheimer’s disease, but challenge the hypothesis that increased APP levels are solely responsible for hyperphosphorylation of tau or enhanced oxidative stress-induced neuronal cell death in Down syndrome associated AD-pathogenesis.
2018-06-12 | GSE100680 | GEO
Project description:Retromer controls cellular homeostasis through regulating integral membrane protein sorting and transport and by controlling maturation of the endo-lysosomal network. Retromer dysfunction, which is linked to neurodegenerative disorders including Parkinson’s and Alzheimer’s diseases, manifests in complex cellular phenotypes, though the precise nature of this dysfunction, and its relation to neurodegeneration, remain unclear. Here, we perform the first integrated multiomics approach to provide precise insight into the impact of Retromer dysfunction on endo-lysosomal health and homeostasis within a human neuroglioma cell model. We quantify profound changes to the lysosomal proteome, indicative of broad lysosomal dysfunction and inefficient autophagic lysosome reformation, coupled with a reconfigured cell surface proteome and secretome reflective of increased lysosomal exocytosis. Through this global proteomic approach and parallel transcriptomic analysis, we provide an unprecedented integrated view of Retromer function in regulating lysosomal homeostasis and emphasise its role in neuroprotection.
2023-04-17 | GSE223292 | GEO
Project description:Purpose: In previous work, we found that iron supplementation to cells rescues impairment of cell viability and proliferation upon lysosomal dysfunction due to inhibition of the vATPase complex. The goal of this study is to characterize the transcriptomic changes (RNA-seq) upon Bafilomycin mediated lysosomal dysfunction with and without iron (Ferric Ammonium Citrate) supplementation. Methods: mRNA profiles of wild type HEK293T cells treated +/- ferric ammonium citrate (0.1mg/ml) and +/- BafilomycinA1 (10nM) were generated by deep sequencing, in triplicate, using Illumina NextSeq500. Results: We mapped about 30-40 million sequence reads per sample to the human genome (build GRCh38). Conclusions: Our study characterizes the transcriptomic changes upon lysosomal dysfunction upon small molecule (Bafilomycin A1) inhibition of vATPase complex. We conclude that there are several notable trasncriptomic changes upon lysosomal dysfunction some of which are reversed by iron supplementation.
2019-12-06 | GSE141507 | GEO
Project description:Autophagy and lysosomal dysfunction in Tay Sachs disease are restored by mTOR modulation
| PRJNA767011 | ENA
Project description:The D620N VPS35 mutation disrupts retrograde endosome to Golgi retromer Trafficking. Thus causes lysosome dysfunction, enhances LRRK2 kinase activity and leads to Parkinson’s disease. We employed a LysoTag immunoprecipitation approach to assess how this impacts lysosomes using quantitative proteomics. The VPS35[D620N] mutation alters the expression of over 350 lysosomal proteins, and induces recruitment of LRRK2 phosphorylated Rab proteins to the lysosome, as well as the phosphoRab effector protein RILPL1.
2023-11-28 | PXD042502 | Pride
Project description:Loss of Down syndrome critical region-1 causes cholesterol-metabolic dysfunction leading to corneal opacity
| PRJNA533631 | ENA
Project description:Down syndrome SNP genotyping data
| EGAD00010000464 | EGA
Project description:Down syndrome CNV genotyping data
| EGAD00010000466 | EGA