Biology subjects

Fowler, S. L.

Publications and source records attributed to Fowler, S. L..

4 recordsLinked to original sources

bioRxiv2026

Brain mitovesicles undergo stage-specific remodelling during the progression of amyloid-β pathology

Mitochondrial dysfunction is an early feature of Alzheimer's disease that shows nonlinear changes as the disease progresses. However, how these changes are reflected in the mitochondrial material released by brain cells remains poorly understood. Mitovesicles are a recently described extracellular vesicle subpopulation of mitochondrial origin that provide a unique insight into mitochondrial alterations in the brain and could potentially show how nonlinear changes evolve across disease stages of amyloid-beta pathology. Here, we isolated forebrain-derived small extracellular vesicles and mitovesicles from wild-type and Amyloid precursor protein (App) knock-in (AppKI) mice, carrying familial AD mutations and progressively accumulating amyloid-beta plaques, at presymptomatic (2-month) and symptomatic (12-month) stages using high-resolution density gradient fractionation. Vesicle identity and composition were assessed by morphological, biophysical and quantitative proteomic analyses, and mitovesicle respiratory function was measured by extracellular flux analysis. We show that mitovesicles carry a distinct, predominantly mitochondrial inner membrane proteome that is remodelled by age and disease in a stage-specific manner. Compared with small extracellular vesicles, mitovesicle proteomic profiles captured disease progression more clearly, with symptomatic AppKI mice forming the most molecularly distinct group. At the presymptomatic stage, AppKI mitovesicles showed reduced mitochondrial protein representation, most notably of fatty acid {beta}-oxidation and lipid-metabolism proteins associated with astroglial and vascular signatures, preceding any detectable respiratory impairment. At the symptomatic stage this reversed: AppKI mitovesicles were enriched for oxidative phosphorylation, mitochondrial membrane and transporter proteins, yet showed reduced Complex IV-linked respiration, revealing a dissociation between mitochondrial cargo abundance and respiratory function. Selected cargo changes were not mirrored in whole-brain tissue, indicating selective remodelling of mitovesicle content. Comparison with mitovesicles from post-mortem human Alzheimer's disease frontotemporal cortex and hippocampus identified a conserved 62-protein mitovesicle core, dominated by oxidative phosphorylation subunits and mitochondrial carriers. In addition, 25 of these proteins were enriched in mitovesicles derived from Alzheimer's and AppKI forebrains, defining a conserved mitovesicular disease signature. Together, these findings establish forebrain-derived mitovesicles as a dynamically remodelled vesicle population that reflects progressive mitochondrial dysfunction in the Alzheimer's disease brain and provides a cross-species resource for future biomarker and mechanistic studies.

neuroscience↗

bioRxiv2026

Population-scale subcellular proteomics reveals intracellular remodelling across the Alzheimer's disease-resilience spectrum

Proteome-wide analyses of human tissue have transformed our understanding of disease, but provide limited insight into protein localisation, a functionally informative dimension of the proteome. In Alzheimer's disease, amyloid-{beta} and tau exhibit aberrant localisation, yet whether spatial reorganisation extends proteome-wide has remained inaccessible to abundance-based proteomics. Here, we develop comparative subcellular proteomics applied to dorsolateral prefrontal cortex from 75 individuals spanning the Alzheimer's disease-resilience spectrum, modelling protein localisation across disease. We identify 217 disease-associated localisation shifts enriched for endolysosomal function, intracellular trafficking, and RNA processing, and resolve tau proteoforms within insoluble aggregates. Our strongest localisation candidates show only modest differences in whole-tissue abundance, highlighting disease biology inaccessible to conventional proteomics. We validate co-localisation of CSNK1A1 with pathological tau and identify an unexpected neuronal localisation pattern for SCAI, a cancer-associated protein not previously characterised in human brain, highlighting the discovery potential of subcellular proteomics in tissue.

neuroscience↗

bioRxiv2023

Tau filaments are tethered within brain extracellular vesicles in Alzheimer's disease

The abnormal assembly of tau protein in neurons is the pathological hallmark of multiple neurodegenerative diseases, including Alzheimers disease (AD). In addition, assembled tau associates with extracellular vesicles (EVs) in the central nervous system of patients with AD, which is linked to its clearance and prion-like propagation between neurons. However, the identities of the assembled tau species and the EVs, as well as how they associate, are not known. Here, we combined quantitative mass spectrometry, cryo-electron tomography and single-particle cryo-electron microscopy to study brain EVs from AD patients. We found filaments of truncated tau enclosed within EVs enriched in endo-lysosomal proteins. We observed multiple filament interactions, including with molecules that tethered filaments to the EV limiting membrane, suggesting selective packaging. Our findings will guide studies into the molecular mechanisms of EV-mediated secretion of assembled tau and inform the targeting of EV-associated tau as potential therapeutic and biomarker strategies for AD.

neuroscience↗

bioRxiv2020

GPCR-mediated clearance of tau in post-synaptic compartments attenuates tau pathology in vivo

Accumulation of pathological tau in synapses has been identified as an early pathogenic event in Alzheimers disease (AD) and correlates strongly with cognitive decline in patients with AD. Tau is a cytosolic, axonal protein. However, in the disease condition, tau accumulates in post-synaptic compartments and pre-synaptic terminals, either due to missorting within neurons, trans-synaptic transfer between neurons or due to failure of clearance systems in synapses. Using a sub-cellular fractionation assay, we show that progressive deposition of seed competent tau occurs predominantly in post-synaptic compartments in a tau transgenic mouse and in AD patient brain, making these neuronal structures particularly vulnerable to tau toxicity. Tau-mediated post-synaptic toxicity could be further exacerbated by impaired proteasome activity which we detected by measuring the levels of polyubiquitin chains that target proteins to proteasomal degradation. To combat the accumulation of tau and proteasome impairment at the subcellular level, we devised a therapeutic strategy of proteasome-mediated clearance of tau restricted to the post-synaptic compartment. Utilizing the pharmacology of GPCRs, we show that in vivo stimulation of the PAC1R receptor by its ligand can propagate intracellular PKA signaling leading to enhanced synaptic proteasome activity and reduced tau in the post-synaptic compartment. Over time, clearance of post-synaptic tau led to reduced tauopathy and cognitive decline in rTg4510 mice. Together, these results highlight a novel therapeutic strategy of targeting GPCRs that propagate cAMP/PKA signaling as a tool to activate proteolysis restricted to synapses to prevent the accumulation of tau in the early stages of AD.

neuroscience↗