Biology subjects

Ankarcrona, M.

Publications and source records attributed to Ankarcrona, M..

6 recordsLinked to original sources

bioRxiv2026

Modulation of mitochondria-ER contacts decrease inflammasome formation and restores amyloid β-peptide phagocytosis in adult mouse microglia

BackgroundAlzheimers disease (AD) is the most prevalent neurodegenerative disease, currently devoid of a cure. ADs clinical manifestations stem from a multitude of dysfunctional cellular processes, regulated by mitochondria-endoplasmic contact sites (MERCS), which undergo physical alterations and malfunction in AD brain. Despite ongoing research, the understanding of MERCS in AD remains in its nascent stages. We postulate that these subcellular interfaces are responsible for AD progression. Neuroinflammation contributes significantly to neurodegeneration and is primarily driven by microglia, the innate immune cells in the brain. In AD, activated microglia secrete pro-inflammatory cytokines that compromise neuronal vitality. The production of these cytokines is promoted by NLRP3 inflammasome. Although inflammasome activation has been observed at MERCS, the underlying MERCS-mediated mechanisms governing regulation of inflammasome activation remain to be elucidated. MethodsPrimary microglia were isolated from 3-4 months old wild-type (WT) and AppNL-G-F mice (AD). MERCS ultrastructure was analyzed by transmission electron microscopy. Mitochondrial Ca2+ level and metabolic function were assessed using Rhod-2 AM fluorescence and Seahorse extracellular flux analysis respectively. Inflammasome activation was induced by lipopolysaccharide and nigericin and evaluated by IL-1{beta} ELISA, caspase-1 activity assay, and ASC immunocytochemistry. MERCS were genetically modulated via siRNA-mediated knockdown of MERCS-associated proteins, and ER-to-mitochondria Ca{superscript 2} transfer was pharmacologically inhibited using Xestospongin C and MCU-i11. Microglial A{beta} phagocytosis was quantified using fluorescence-conjugated A{beta}1-42. ResultsAD microglia exhibited increased MERCS number and contact length, accompanied by a reduction in mitochondria-ER proximity. These structural changes were associated with elevated mitochondrial Ca2+ levels and enhanced respiratory activity, indicating metabolic reprogramming and functional change. Structural and functional decrease of microglial MERCS attenuated NLRP3 inflammasome activation and restored inflammasome-associated impairments in A{beta} phagocytosis. Pharmacological inhibition of Ca2+ channels at MERCS identified ER-to-mitochondria Ca2+transfer as a key regulatory mechanism for inflammasome activation. ConclusionsOur findings identify microglial MERCS remodeling as an early event in AD and establish ER-mitochondria coupling as an upstream regulator of energy metabolism, inflammation, and A{beta} clearance. Targeting MERCS may therefore represent a promising strategy to modulate neuroinflammation while preserving essential microglial functions in AD.

neuroscience↗

bioRxiv2026

Astrocyte-neuron mitochondrial transfer via mitoEVs supports neuronal energy metabolism and is impaired in early Alzheimer's disease

BackgroundMitochondrial dysfunction is an early and central feature of Alzheimers disease (AD). In particular, intercellular mitochondrial transfer has emerged as a mechanism of neuronal support in brain injury and neurodegeneration. However, pathways governing astrocyte-to-neuron transfer and its role in AD pathogenesis remain unknown. MethodsUsing the AppNL-G-F knock-in AD model, we combined high-resolution 4D live-cell imaging with quantitative fluorescence-based reporters to assess synaptic function and mitochondrial network dynamics in neurons and astrocytes. Direct and extracellular vesicle (EV)-restricted neuron-astrocyte co-culture systems were used to investigate bidirectional mitochondrial transfer. We performed the first in-depth structural, proteomic, and functional characterization of astrocyte-derived mitochondrial extracellular vesicles (mitoEVs) using cryo-electron microscopy, quantitative mass spectrometry, and bioenergetic analyses to define their cargo composition and metabolic effects. ResultsWe identified cell-type-specific mitochondrial remodeling in early AD, with compartmentalized synaptic energy deficits in neurons and hyperdynamic, less interconnected, yet metabolically preserved networks in astrocytes, preceding global bioenergetic decline. Bidirectional mitochondrial transfer between astrocytes and neurons, also at axonal terminals, was mediated by specialized mitoEVs but significantly reduced in the AppNL-G-Fmodel. Comprehensive proteomic and functional profiling revealed that WT astrocyte-derived mitoEVs are enriched in inner membrane and matrix proteins, supporting oxidative phosphorylation, lipid and amino acid metabolism, and redox homeostasis. In contrast, AppNL-G-F mitoEVs are selectively depleted of respiratory and fatty acid oxidation components and exhibit impaired respiration with reduced Complex IV activity. Functionally, WT mitoEVs promote mobilization of abnormal accumulation of lipid droplets in AppNL-G-Fneurons, restore fatty acid oxidation, and increase neuronal bioenergetics, including at the synapses. In contrast, disease-derived mitoEVs fail to engage these pathways. ConclusionsTogether, these findings identify mitoEV-mediated mitochondrial transfer as a glia-to-neuron metabolic pathway compromised in early AD and reveal a coordinated role for oxidative phosphorylation and fatty acid oxidation in supporting synaptic energy homeostasis.

neuroscience↗

bioRxiv2025

Integrating simulated and experimental data to identify mitochondrial bioenergetic defects in Parkinson's Disease models

Mitochondrial bioenergetics are vital for ATP production and are associated with several diseases, including Parkinsons Disease. Here, we simulated a computational model of mitochondrial ATP production to interrogate mitochondrial bioenergetics under physiological and pathophysiological conditions, and provide a data resource that can be used to interpret mitochondrial bioenergetics experiments. We first characterised the impact of several common respiratory chain impairments on experimentally-observable bioenergetic parameters. We then established an analysis pipeline to integrate simulations with experimental data and predict the molecular defects underlying experimental bioenergetic phenotypes. We applied the pipeline to data from Parkinsons Disease models. We verified that the impaired bioenergetic profile previously measured in Parkin knockout neurons can be explained by increased mitochondrial uncoupling. We then generated primary cortical neurons from a Pink1 KO mouse model of Parkinsons, and measured reduced OCR capacity and increased resistance to Complex III inhibition. Here, our pipeline predicted that multiple respiratory chain impairments are required to explain this bioenergetic phenotype. Finally, we provide all simulated data as a user-friendly resource that can be used to interpret mitochondrial bioenergetics experiments, predict underlying molecular defects, and inform experimental design. HighlightsO_LIThe complexity of mitochondrial bioenergetics can make experimental data difficult to interpret. C_LIO_LIWe simulated a computational model of mitochondrial bioenergetics in healthy and pathological conditions, and established an analysis pipeline to integrate model simulations with experimental data. C_LIO_LIWe applied the pipeline to data from Parkinsons Disease models to predict the molecular defects underlying Parkinsons-related pathology. C_LIO_LIWe provide all outputs in a user-friendly Excel file, which serves as a valuable resource to the community for insight into the effects of pathology on mitochondrial bioenergetics and for interpretation of experimental results. C_LI

neuroscience↗

bioRxiv2025

Mitochondria serve as a Holdout Compartment for Aggregation-Prone Proteins hindering Efficient Ubiquitin-Dependent Degradation

The accumulation of protein aggregates has been causatively linked to the pathogenesis of neurodegenerative diseases. In this study, we have conducted a genome-wide CRISPR-Cas9 screen to identify cellular factors that stimulate the degradation of an aggregation-prone reporter protein. Our findings revealed that genes encoding proteins involved in mitochondrial homeostasis, including the translation factor eIF5A, were highly enriched among suppressors of degradation of an aggregation-prone reporter. Conversely, endoplasmic reticulum (ER)-associated ubiquitin ligases facilitated degradation, indicating opposing roles for these cellular compartments in the clearance of aggregation-prone proteins. Genetic or chemical inhibition of eIF5A led to the dissociation of the aggregation-prone substrate from mitochondria, which was accompanied by enhanced degradation through ER-associated ubiquitination. The presence of an aggregation-prone, amphipathic helix that localized the reporter to mitochondria was crucial for the stimulatory effect of eIF5A inhibition. Additionally, the steady-state levels of -synuclein, a disease-associated protein containing an amphipathic helix that mislocalizes to mitochondria, were reduced upon eIF5A inhibition. We propose that mitochondria behave as a holdout compartment for aggregation-prone proteins, keeping them out of reach of ubiquitin ligases that target them for proteasomal degradation. Therefore, preventing mitochondrial localization of aggregation-prone proteins may offer a viable therapeutic strategy for reducing their levels in neurodegenerative disorders.

cell biology↗

bioRxiv2023

Simultaneous detection of membrane contact dynamics and associated Ca2+ signals by reversible chemogenetic reporters

Membrane contact sites (MCSs) are hubs allowing various cell organelles to coordinate their activities. The dynamic nature of these sites and their small size hinder analysis by current imaging techniques. To overcome these limitations, we here designed a series of reversible chemogenetic reporters incorporating improved, low-affinity variants of splitFAST, and studied the dynamics of different MCSs at high spatiotemporal resolution, both in vitro and in vivo. We demonstrated that these versatile reporters suit different experimental setups well, allowing one to address challenging biological questions. Using these novel probes, we identified a hitherto unknown pathway, in which calcium (Ca2+) signalling dynamically regulates endoplasmic reticulum-mitochondria juxtaposition, characterizing the underlying mechanism. Finally, by integrating Ca2+-sensing capabilities into the splitFAST technology, we introduced PRINCESS (PRobe for INterorganelle Ca2+-Exchange Sites based on SplitFAST), an unprecedented class of reporters to simultaneously detect MCSs and measure the associated Ca2+ dynamics using a single biosensor.

cell biology↗

bioRxiv2023

Early mitochondrial dysfunction proceeds neuroinflammation, synaptic alteration, and autophagy impairment in hippocampus of App knock-in Alzheimer mouse models

Increased amyloid {beta}-peptide (A{beta}) level is one of the drivers of Alzheimers disease (AD). Amyloid precursor protein (App) knock-in mice recapitulate the human A{beta} pathology, allowing the elucidation of the downstream effects of A{beta} and their temporal appearance upon disease progression. Here we have investigated the sequential onset of AD-like pathologies in the AppNL-F and AppNL-G-F knock-in mouse models by time-course transcriptome analysis of the hippocampus, a region severely affected in AD. Energy metabolism emerged as one of the most significantly altered pathways at an early stage of the development of the pathologies. Functional experiments in mitochondria isolated from AppNL-G-F brain subsequently identified upregulation of oxidative phosphorylation driven by the activity of mitochondrial complexes I, IV and V, combined with higher susceptibility to Ca2+-overload. This was followed by a strong neuroinflammatory response and impaired autophagy. Accumulation of autophagosomes and reduced number of mitochondria content in presynaptic terminals could account for the altered synapse morphology including increased number of synaptic vesicles and lowered thickness of post synaptic density in AppNL-G-F mice. This shows that A{beta}-induced pathways in the App knock-in mice recapitulate some key pathologies observed in AD brain, and our data herein contributes to the understanding of their timewise appearance and potential role in new therapeutic approaches.

neuroscience↗