Biology subjects

Checler, F.

Publications and source records attributed to Checler, F..

6 recordsLinked to original sources

bioRxiv2026

APP metabolism is regulated by p97/VCP through an autophagy and endolysosome-dependent mechanism

Deregulation of amyloid precursor protein (APP) metabolism leads to the production of pathological proteoforms of A{beta} peptides, which ultimately form amyloid deposits, a primary pathological feature of Alzheimers disease (AD). The accumulation of misfolded proteins and alterations in protein degradation systems, such as the ubiquitin-proteasome system, endoplasmic reticulum-associated degradation, and autophagy-lysosomal pathways, also contribute to AD development. The Valosin-Containing Protein AAA-ATPase (p97/VCP) is a crucial regulator of proteostasis, facilitating the clearance of misfolded proteins by the proteasome and other protein degradation systems. Here, we investigated whether VCP influences APP processing. Reducing VCP expression or inhibiting its ATPase activity led to the accumulation of mature, full-length APP in cells, thereby decreasing APP trafficking to the cell surface. Downstream of APP-CTFs secretase processing, p97/VCP modulates APP-CTFs cleavage and degradation via autophagy and endolysosomal-dependent mechanisms. Our findings demonstrate that VCP is involved in APP metabolism at two levels: controlling APP trafficking within the cell secretory pathway and regulating autophagy-dependent degradation of APP-CTFs, suggesting a potential role for VCP in the APP deregulation observed in AD.

cell biology↗

bioRxiv2025

Large extracellular vesicles containing mitochondria (EVMs) derived from Alzheimer disease cells harbor pathologic functional and molecular profiles and spread mitochondrial dysfunctions

In addition to small extracellular vesicles known as exosomes, cells release large extracellular vesicles containing mitochondria (EVMs). However, the molecular and functional characteristics of EVMs, as well as the impact of EVM secretion on the spreading of mitochondrial dysfunction between cells, remain unknown in the context of Alzheimers Disease (AD). Here, we provide an ultrastructural, biochemical, and functional characterization of EVMs isolated from cells expressing the amyloid precursor protein (APP) with the familial Swedish mutation (APPswe). We identified differential proteomic and lipidomic signatures in APPswe-derived EVMs compared to control EVMs and revealed a specific proteomic profile in EVMs isolated from conditioned media of fibroblasts from AD patients at the prodromal stage of the disease. Our findings show that APP-C terminal fragments (APP-CTFs) pathogenic accumulation in cells potentiates EVM secretion through the budding of the plasma membrane. We lastly demonstrated that APP-CTFs loaded EVMs are active carriers of dysfunctional mitochondria that transfer mitochondrial pathology to naive control recipient cells.

neuroscience↗

bioRxiv2024

Hampered AMPK-ULK1 cascade in Alzheimer disease (AD) instigates mitochondria dysfunctions and AD-related alterations that are alleviated by metformin

BackgroundMitochondrial structure and function alterations are key pathological features in Alzheimers disease (AD) brains. The adenosine monophosphate-activated protein kinase (AMPK) and its downstream effector Unc-51 like autophagy activating kinase 1 (ULK1) represent a key node controlling mitochondria health, the alteration of which likely contribute to AD development. MethodsWe designed this study to investigate AMPK-ULK1 activation state in post-mortem human sporadic AD brains, in 3xTgAD mice that recapitulate most of human AD features, and in neuronal cells expressing the amyloid precursor protein with the familial Swedish mutation (APPswe). We examined the impact of the pharmacological and genetic modulation of AMPK-ULK1 cascade on mitochondria structure and functions in APPswe cells. We evaluated the potential beneficial impact of AMPK-ULK1 activation by Metformin (Met) on mitochondria defects, as well as on early- and late-stage AD-related alterations in vivo and ex vivo. ResultsAt first, we show that AMPK-ULK1 cascade is defective in murine and human AD brains as well as in APPswe cells. We then report that Met administration to 3xTgAD mice alleviates the alterations of neuronal mitochondria structure and function and we consolidate these results in cells using both pharmacological and genetic tools to modulate AMPK-ULK1 cascade. In mice brains, Met reduces the early accumulation of APP C-terminal fragments (APP-CTFs) as well as the amyloid beta (A{beta}) burden present in aged mice. Mechanistically, we show that Met increases the localization of APP-CTFs within cathepsin D-positive lysosomal compartments in vivo and enhances cathepsin D activity in vitro. The reduction of A{beta} load by Met occurs through an increased recruitment of Iba1+ cells to A{beta} plaques and an enhancement of the phagocytic activity of microglia. Accordingly, in symptomatic 3xTgAD mice, Met alleviates microgliosis and astrogliosis, modulates microglia morphology, reduces peripheral proinflammatory cytokines levels, and regulates the expression of a set of inflammatory genes. In addition, Met normalizes dendritic spines shape in organotypic hippocampal slice cultures modeling AD and improves learning performance of 3xTgAD mice. ConclusionsOur study demonstrates potential therapeutic benefits of targeting AMPK-ULK1 cascade to reverse both early and late AD-related alterations, deserving further investigation in fundamental research and in human clinical studies.

neuroscience↗

bioRxiv2023

Mitochondria alterations in fibroblasts from sporadic Alzheimer's disease (AD) patients correlate with AD-related clinical hallmarks

INTRODUCTIONMitochondria dysfunctions are key features in Alzheimers disease (AD). The occurrence of these disturbances in AD patients peripheral cells and their potential correlation with disease progression are under investigated. METHODSWe studied mitochondrial structure, function and mitophagy in fibroblasts including healthy volunteers and AD patients at the prodromal (AD-MCI) or demented (AD-D) stages. We carried out correlation studies with clinical cognitive scores, A{beta} plaques burden and the accumulation of peripheral amyloid precursor protein C-terminal fragments (APP-CTFs). RESULTSWe unveiled progressive alteration of mitochondria structure as well as specific mitochondrial dysfunctions signatures in AD-MCI and AD-D fibroblasts and show defective mitophagy and autophagy linked to impaired lysosomal activity in AD-D fibroblasts. We reported on significant correlations of a subset of these dysfunctions with cognitive decline, AD-related clinical hallmarks and peripheral APP-CTFs accumulation. DISCUSSIONThis study emphasizes the potential use of peripheral cells for investigating AD pathophysiology and likely diagnosis.

cell biology↗

bioRxiv2020

MT5-MMP controls APP metabolism and the fate of beta-CTF/C99 and Abeta through proteolytic-dependent and -independent mechanisms relevant for Alzheimer's disease

We previously discovered the implication of membrane-type 5-matrix metalloproteinase (MT5-MMP) in Alzheimers disease AD pathogenesis. Here we shed new light on pathogenic mechanisms by which MT5-MMP controls APP processing and the fate of amyloid beta peptide (A{beta}), its precursor C99 and C83. We found in HEK carrying the APP Swedish familial mutation (HEKswe) that MT5-MMP-mediated processing of APP that releases the soluble 95 kDa form (sAPP95), was hampered by the removal of the C-terminal non-catalytic domains of MT5-MMP. Catalytically inactive MT5-MMP variants increased the levels of A{beta} and promoted APP/C99 sorting in the endo-lysosomal system. We found interaction of C99 with the C-terminal portion of MT5-MMP, the deletion of which caused a strong degradation of C99 by the proteasome, preventing A{beta} accumulation. These findings reveal novel mechanisms for MT5-MMP control of APP metabolism and C99 fate involving proteolytic and non-proteolytic actions mainly mediated by the C-terminal part of the proteinase.

neuroscience↗

bioRxiv2019

Pyk2 Overexpression in Postsynaptic Neurons Blocks Aβ1-42-induced Synaptotoxicity in a Microfluidic Co-Culture Model

Recent meta-analyses of genome-wide association studies identified a number of genetic risk factors of Alzheimers disease; however, little is known about the mechanisms by which they contribute to the pathological process. As synapse loss is observed at the earliest stage of Alzheimers disease, deciphering the impact of Alzheimers risk genes on synapse formation and maintenance is of great interest. In this paper, we report a microfluidic co-culture device that physically isolates synapses from pre- and postsynaptic neurons and chronically exposes them to toxic amyloid-beta (A{beta}) peptides secreted by model cell lines overexpressing wild-type or mutated (V717I) amyloid precursor protein (APP). Co-culture with cells overexpressing mutated APP exposed the synapses of primary hippocampal neurons to A{beta}1-42 molecules at nanomolar concentrations and induced a significant decrease in synaptic connectivity, as evidenced by distance-based assignment of postsynaptic puncta to presynaptic puncta. Treating the cells with antibodies that target different forms of A{beta} suggested that low molecular weight oligomers are the likely culprit. As proof of concept, we demonstrate that overexpression of protein tyrosine kinase 2 beta (Pyk2) -an Alzheimers disease genetic risk factor involved in synaptic plasticity and shown to decrease in Alzheimers disease brains at gene expression and protein levels-selectively in postsynaptic neurons is protective against A{beta}1-42-induced synaptotoxicity. In summary, our lab-on-a-chip device provides a physiologically-relevant model of Alzheimers disease-related synaptotoxicity, optimal for assessing the impact of risk genes in pre- and postsynaptic compartments.

neuroscience↗