bims-axbals 2025-03-16 papers

bims-axbals

Biomed News

on Axonal biology and ALS

Issue of 2025–03–16
nineteen papers selected by
TJ Krzystek

Puromycin Proximity Ligation Assay (Puro-PLA) to Assess Local Translation in Axons From Human Neurons.
LRRK2 in Drosophila Melanogaster Model: Insights into Cellular Dysfunction and Neuroinflammation in Parkinson's Disease.
PTPσ-mediated PI3P regulation modulates neurodegeneration in C9ORF72-ALS/FTD.
Novel subcellular regulatory mechanisms of protein homeostasis and its implications in amyotrophic lateral sclerosis.
Loss of Sarm1 Mitigates Axonal Degeneration and Promotes Neuronal Repair After Ischemic Stroke.
Intersecting impact of CAG repeat and Huntingtin knockout in stem cell-derived cortical neurons.
Neurofilament accumulation disrupts autophagy in giant axonal neuropathy.
Tubulin Regulates the Stability and Localization of STMN2 by Binding Preferentially to Its Soluble Form.
How does autophagy impact neurological function?
Phagocytosis-driven neurodegeneration through opposing roles of an ABC transporter in neurons and phagocytes.
Derivation of functional neurons from induced pluripotent stem cells using a simple neuromesodermal progenitor generation and rapid spinal cord neuron differentiation process.
Mitochondrial dysfunction drives a neuronal exhaustion phenotype in methylmalonic aciduria.
Cellular homeostatic responses to lysosomal damage.
Subcellular proteomics and iPSC modeling uncover reversible mechanisms of axonal pathology in Alzheimer's disease.
Oxidized protein aggregate lipofuscin impairs cardiomyocyte contractility via late-stage autophagy inhibition.
Lysosomal acidification impairment in astrocyte-mediated neuroinflammation.
Autophagy in skeletal muscle dysfunction of chronic obstructive pulmonary disease: implications, mechanisms, and perspectives.
SNAP-25: A biomarker of synaptic loss in neurodegeneration.
Labeling of mitochondria for detection of intercellular mitochondrial transfer.

Bio Protoc. 2025 Mar 05. 15(5): e5224

Puromycin Proximity Ligation Assay (Puro-PLA) to Assess Local Translation in Axons From Human Neurons.

Raffaella De Pace, Juan S Bonifacino, Saikat Ghosh.

  Local mRNA translation in axons is crucial for the maintenance of neuronal function and homeostasis, particularly in processes such as axon guidance and synaptic plasticity, due to the long distance from axon terminals to the soma. Recent studies have shown that RNA granules can hitchhike on the surface of motile lysosomal vesicles, facilitating their transport within the axon. Accordingly, disruption of lysosomal vesicle trafficking in the axon, achieved by knocking out the lysosome-kinesin adaptor BLOC-one-related complex (BORC), decreases the levels of a subset of mRNAs in the axon. This depletion impairs the local translation of mitochondrial and ribosomal proteins, leading to mitochondrial dysfunction and axonal degeneration. Various techniques have been developed to visualize translation in cells, including translating RNA imaging by coat protein knock-off (TRICK), SunTag, and metabolic labeling using the fluorescent non-canonical amino acid tagging (FUNCAT) systems. Here, we describe a sensitive technique to detect newly synthesized proteins at subcellular resolution, the puromycin proximity ligation assay (Puro-PLA). Puromycin, a tRNA analog, incorporates into nascent polypeptide chains and can be detected with an anti-puromycin antibody. Coupling this method with the proximity ligation assay (PLA) allows for precise visualization of newly synthesized target proteins. In this article, we describe a step-by-step protocol for performing Puro-PLA in human induced pluripotent stem cell (iPSC)-derived neuronal cultures (i3Neurons), offering a powerful tool to study local protein synthesis in the axon. This tool can also be applied to rodent neurons in primary culture, enabling the investigation of axonal protein synthesis across species and disease models. Key features • Establishment of quantitative local translation assay in axons of human iPSC-derived neurons. • Microscopy-based direct visualization of local translation events in neurons. • Puro-PLA is a sensitive method for detecting new protein synthesis occurring within minutes in neurons, enabling precise temporal analysis of translation dynamics.

Keywords:  Axon; Human i3Neurons; Local translation; Lysosome; Proximity ligation assay (PLA); Puromycin

DOI:  https://doi.org/10.21769/BioProtoc.5224
Int J Mol Sci. 2025 Feb 27. pii: 2093. [Epub ahead of print]26(5):

LRRK2 in Drosophila Melanogaster Model: Insights into Cellular Dysfunction and Neuroinflammation in Parkinson's Disease.

Cristina Ciampelli, Grazia Galleri, Manuela Galioto, Paolo Mereu, Monica Pirastru, Roberto Bernardoni, Diego Albani, Claudia Crosio, Ciro Iaccarino.

  Parkinson's disease (PD) is a fatal neurodegenerative disease for which there are no still effective treatments able to stop or slow down neurodegeneration. To date, pathological mutations in the leucine-rich repeat kinase 2 (LRRK2) gene have been identified as the major genetic cause of PD, although the molecular mechanism responsible for the loss of dopaminergic neurons is still cryptic. In this review, we explore the contribution of Drosophila models to the elucidation of LRRK2 function in different cellular pathways in either neurons or glial cells. Importantly, recent studies have shown that LRRK2 is highly expressed in immunocompetent cells, including astrocytes and microglia in the brain, compared to neuronal expression. LRRK2 mutations are also strongly associated with the development of inflammatory diseases and the production of inflammatory molecules. Using Drosophila models, this paper shows that a genetic reduction of the inflammatory response protects flies from the neurodegeneration induced by LRRK2 pathological mutant expression.

Keywords:  Attacin-A; Drosophila; LRRK2; Parkinson’s disease

DOI:  https://doi.org/10.3390/ijms26052093
Neuron. 2025 Mar 10. pii: S0896-6273(25)00118-7. [Epub ahead of print]

PTPσ-mediated PI3P regulation modulates neurodegeneration in C9ORF72-ALS/FTD.

Zhe Zhang, Xiujuan Fu, Noelle Wright, Weiren Wang, Yingzhi Ye, Julie Asbury, Yini Li, Chengzhang Zhu, Rong Wu, Shaopeng Wang, Shuying Sun.

  The most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is the repeat expansion in C9ORF72. Dipeptide repeat (DPR) proteins translated from both sense and antisense repeats, especially arginine-rich DPRs (R-DPRs), contribute to neurodegeneration. Through CRISPR interference (CRISPRi) screening in human-derived neurons, we identified receptor-type tyrosine-protein phosphatase S (PTPσ) as a strong modifier of poly-GR-mediated toxicity. We showed that reducing PTPσ promotes the survival of both poly-GR- and poly-PR-expressing neurons by elevating phosphatidylinositol 3-phosphate (PI3P), accompanied by restored early endosomes and lysosomes. Remarkably, PTPσ knockdown or inhibition substantially rescues the PI3P-endolysosomal defects and improves the survival of C9ORF72-ALS/FTD patient-derived neurons. Furthermore, the PTPσ inhibitor diminishes GR toxicity and rescues pathological and behavioral phenotypes in mice. Overall, these findings emphasize the critical role of PI3P-mediated endolysosomal deficits induced by R-DPRs in disease pathogenesis and reveal the therapeutic potential of targeting PTPσ in C9ORF72-ALS/FTD.

Keywords:  ALS; C9ORF72; CRISPR screening; FTD; PI3P; PTPσ; endosome; lysosome; poly-GR/PR

DOI:  https://doi.org/10.1016/j.neuron.2025.02.005
Biochem Biophys Res Commun. 2025 Mar 03. pii: S0006-291X(25)00296-7. [Epub ahead of print]756 151582

Novel subcellular regulatory mechanisms of protein homeostasis and its implications in amyotrophic lateral sclerosis.

Aisheng Zhan, Keke Zhong, Kejing Zhang.

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron degenerative disorder. Protein aggregates induce various forms of neuronal dysfunction and represent pathological hallmarks in ALS patients. Reducing protein aggregates could be a promising therapeutic strategy for ALS. While most studies have focused on cytoplasmic protein homeostasis, neurons adaptively reduce aggregates across subcellular compartments during stress through previously uncharacterized mechanisms. Here, we summarize novel compartment-specific proteostatic mechanisms: (1) the ERAD/RESET pathways, (2) HSPs-mediated nuclear sequestration, (3) mitochondrial aggregate import (MAGIC), (4) neurite-localized UPS/autophagosome and NMP, and (5) exopher-mediated extracellular disposal. These mechanisms collectively ensure cellular stress adaptation and provide novel therapeutic targets for ALS treatment.

DOI: https://doi.org/10.1016/j.bbrc.2025.151582
bioRxiv. 2025 Feb 25. pii: 2025.02.20.639171. [Epub ahead of print]

Loss of Sarm1 Mitigates Axonal Degeneration and Promotes Neuronal Repair After Ischemic Stroke.

Jack T Wang, Brian Toh, Jennifer An, Yutaro Komuro, Marlesa I Godoy, Jennifer Putman, S Thomas Carmichael, Robert Damoiseaux, Jason D Hinman.

Axonal degeneration is a core feature of ischemic brain injury that limits functional recovery (1). The pro-degenerative molecule Sarm1 is required for Wallerian axon degeneration after traumatic and chemotoxic nerve injuries (2), however it is unclear if a similar mechanism mediates axonal degradation after ischemic injury. Here we show that loss of Sarm1 results in profound attenuation of axonal degeneration after focal ischemia to the subcortical white matter. Moreover, absence of Sarm1 significantly promotes the survival of neurons remote from but connected to the infarct after ischemic injuries to the subcortical white matter as well as to the cortex. To further understand the mechanism of Sarm1-/- mediated neuronal protection, we performed differential gene expression analyses of wildtype and Sarm1-/- stroke-injured neurons and found that the loss of Sarm1 activates a pro-growth molecular program that promotes new axon and synapse formation after white matter ischemia. Using a functional genomics approach to recapitulate such a molecular program in Sarm1-/- neurons, we identify molecular compounds sufficient to enhance cortical neurite outgrowth in vitro , and all of which elicit a conserved epigenetic signature promoting axonogenesis. These results indicate that Sarm1 promotes axonal degeneration and concurrently inhibits an axonal reparative program encoded at the level of the epigenome that can be modulated pharmacologically. Our findings thus reveal a novel role for Sarm1 as a crucial regulator of both axonal degeneration and axonal remodeling after ischemic stroke.
SIGNIFICANCE STATEMENT: Axon degeneration is a pivotal event following ischemic stroke, however the mechanism of white matter loss in stroke is unknown. We demonstrate that the pro-degenerative molecule Sarm1 is required for axonal and neuronal degeneration after ischemic injuries, and that loss of Sarm1 surprisingly induces the activation of a reparative program driving new axon and synapse formation. Using functional genomics, we uncover molecular candidates that phenocopy this pro-growth molecular signature in Sarm1-/- neurons, and show that these compounds are sufficient to promote de novo axonal growth via an epigenetic mechanism. Our results thus reveal a novel role for Sarm1 as a regulator of both axonal degeneration and axonal remodeling after ischemia, and identify pharmacologic candidates to promote axonal repair in stroke.

DOI: https://doi.org/10.1101/2025.02.20.639171
bioRxiv. 2025 Feb 24. pii: 2025.02.24.639958. [Epub ahead of print]

Intersecting impact of CAG repeat and Huntingtin knockout in stem cell-derived cortical neurons.

Jennifer T Stocksdale, Matthew J Leventhal, Stephanie Lam, Yu-Xin Xu, Yang Oliver Wang, Keona Q Wang, Reuben Tomas, Zohreh Faghihmonzavi, Yogi Raghav, Charlene Smith, Jie Wu, Ricardo Miramontes, Kanchan Sarda, Heather Johnson, Min-Gyoung Shin, Terry Huang, Mikelle Foster, Mariya Barch, Naufa Armani, Chris Paiz, Lindsay Easter, Erse Duderstadt, Vineet Vaibhav, Niveda Sundararaman, Dan P Felsenfeld, Thomas F Vogt, Jennifer Van Eyk, Steve Finkbeiner, Julia A Kaye, Ernest Fraenkel, Leslie M Thompson.

Huntington's Disease (HD) is caused by a CAG repeat expansion in the gene encoding Huntingtin (HTT ) . While normal HTT function appears impacted by the mutation, the specific pathways unique to CAG repeat expansion versus loss of normal function are unclear. To understand the impact of the CAG repeat expansion, we evaluated biological signatures of HTT knockout ( HTT KO) versus those that occur from the CAG repeat expansion by applying multi-omics, live cell imaging, survival analysis and a novel feature-based pipeline to study cortical neurons (eCNs) derived from an isogenic human embryonic stem cell series (RUES2). HTT KO and the CAG repeat expansion influence developmental trajectories of eCNs, with opposing effects on the growth. Network analyses of differentially expressed genes and proteins associated with enriched epigenetic motifs identified subnetworks common to CAG repeat expansion and HTT KO that include neuronal differentiation, cell cycle regulation, and mechanisms related to transcriptional repression and may represent gain-of-function mechanisms that cannot be explained by HTT loss of function alone. A combination of dominant and loss-of-function mechanisms are likely involved in the aberrant neurodevelopmental and neurodegenerative features of HD that can help inform therapeutic strategies.

DOI: https://doi.org/10.1101/2025.02.24.639958
JCI Insight. 2025 Mar 10. pii: e177999. [Epub ahead of print]10(5):

Neurofilament accumulation disrupts autophagy in giant axonal neuropathy.

Jean-Michel Paumier, James Zewe, Chiranjit Panja, Melissa R Pergande, Meghana Venkatesan, Eitan Israeli, Shikha Prasad, Natasha Snider, Jeffrey N Savas, Puneet Opal.

  Neurofilament accumulation is associated with many neurodegenerative diseases, but it is the primary pathology in giant axonal neuropathy (GAN). This childhood-onset autosomal recessive disease is caused by loss-of-function mutations in gigaxonin, the E3 adaptor protein that enables neurofilament degradation. Using a combination of genetic and RNA interference approaches, we found that dorsal root ganglia from mice lacking gigaxonin have impaired autophagy and lysosomal degradation through 2 mechanisms. First, neurofilament accumulations interfere with the distribution of autophagic organelles, impairing their maturation and fusion with lysosomes. Second, the accumulations attract the chaperone 14-3-3, which is responsible for the proper localization of the key autophagy regulator transcription factor EB (TFEB). We propose that this dual disruption of autophagy contributes to the pathogenesis of other neurodegenerative diseases involving neurofilament accumulations.

Keywords:  Autophagy; Cell biology; Neurological disorders; Neuroscience; Ubiquitin-proteosome system

DOI:  https://doi.org/10.1172/jci.insight.177999
bioRxiv. 2025 Feb 28. pii: 2025.02.27.640326. [Epub ahead of print]

Tubulin Regulates the Stability and Localization of STMN2 by Binding Preferentially to Its Soluble Form.

Xiang Deng, Gary Bradshaw, Marian Kalocsay, Timothy Mitchison.

Loss of the tubulin-binding protein STMN2 is implicated in amyotrophic lateral sclerosis (ALS) but how it protects neurons is not known. STMN2 is known to turn over rapidly and accumulate at axotomy sites. We confirmed fast turnover of STMN2 in U2OS cells and iPSC-derived neurons and showed that degradation occurs mainly by the ubiquitin-proteasome system. The membrane targeting N-terminal domain of STMN2 promoted fast turnover, whereas its tubulin binding stathmin-like domain (SLD) promoted stabilization. Proximity labeling and imaging showed that STMN2 localizes to trans-Golgi network membranes and that tubulin binding reduces this localization. Pull-down assays showed that tubulin prefers to bind to soluble over membrane-bound STMN2. Our data suggest that STMN2 interconverts between a soluble form that is rapidly degraded unless bound to tubulin and a membrane-bound form that does not bind tubulin. We propose that STMN2 is sequestered and stabilized by tubulin binding, while its neuroprotective function depends on an unknown molecular activity of its membrane-bound form.

DOI: https://doi.org/10.1101/2025.02.27.640326
Neuroscientist. 2025 Mar 13. 10738584251324459

How does autophagy impact neurological function?

Angeleen Fleming, Ana Lopez, Matea Rob, Sarayu Ramakrishna, So Jung Park, Xinyi Li, David C Rubinsztein.

  Autophagies describe a set of processes in which cells degrade their cytoplasmic contents via various routes that terminate with the lysosome. In macroautophagy (the focus of this review, henceforth autophagy), cytoplasmic contents, including misfolded proteins, protein complexes, dysfunctional organelles, and various pathogens, are captured within double membranes called autophagosomes, which ultimately fuse with lysosomes, after which their contents are degraded. Autophagy is important in maintaining neuronal and glial function; consequently, disrupted autophagy is associated with various neurologic diseases. This review provides a broad perspective on the roles of autophagy in the CNS, highlighting recent literature that furthers our understanding of the multifaceted role of autophagy in maintaining a healthy nervous system.

Keywords:  aggregates; autophagy; glia; neural stem cell; neuroinflammation; neuron

DOI:  https://doi.org/10.1177/10738584251324459
Sci Adv. 2025 Mar 14. 11(11): eadr5448

Phagocytosis-driven neurodegeneration through opposing roles of an ABC transporter in neurons and phagocytes.

Xinchen Chen, Bei Wang, Ankita Sarkar, Zixian Huang, Nicolas Vergara Ruiz, Ann T Yeung, Rachael Chen, Chun Han.

Lipid homeostasis is critical to neuronal survival. ATP-binding cassette A (ABCA) proteins are lipid transporters associated with neurodegenerative diseases. How ABCA transporters regulate lipid homeostasis in neurodegeneration is an outstanding question. Here we report that the Drosophila ABCA protein engulfment ABC transporter in the ovary (Eato) regulates phagocytosis-dependent neurodegeneration by playing opposing roles in neurons and phagocytes: In neurons, Eato prevents dendrites and axons from being attacked by neighboring phagocytes; in phagocytes, Eato sensitizes the cell for detecting neurons as engulfment targets. Thus, Eato deficiency in neurons alone causes phagocytosis-dependent neurite degeneration, but additional Eato loss from phagocytes suppresses the neurite degeneration. Mechanistically, Eato functions by removing the eat-me signal phosphatidylserine from the cell surface in both neurons and phagocytes. Multiple human and worm ABCA homologs can rescue Eato loss in phagocytes but not in neurons, suggesting both conserved and cell type-specific activities of ABCA proteins. These results imply possible mechanisms of neuron-phagocyte interactions in neurodegenerative diseases.

DOI: https://doi.org/10.1126/sciadv.adr5448
Hum Cell. 2025 Mar 13. 38(3): 69

Derivation of functional neurons from induced pluripotent stem cells using a simple neuromesodermal progenitor generation and rapid spinal cord neuron differentiation process.

Selinay Şenkal-Turhan, Ezgi Bulut-Okumuş, Fikrettin Şahin, Yavuz Yavuz, Bayram Yılmaz, Hatice Burcu Şişli, Sadık Kalaycı, Hüseyin Buğra Özgün, Zehra Ömeroğlu Ulu, Pınar Akkuş Süt, Ayşegül Doğan.

  To generate spinal cord neurons from pluripotent stem cells via neuromesodermal progenitors (NMPs) is not only an important step for regenerative purposes but also required for human developmental research. This study describes a protocol to obtain spinal cord neurons in culture using induced pluripotent stem-cell-derived NMPs. The protocol starts with a 3D culture of NMPs and continues with the transfer of 3D NMPs to monolayer culture in which retinoic acid and sonic hedgehog pathways were triggered sequentially. The established protocol enabled generation of spinal cord neurons with active calcium signaling, electrophysiological activity, axon elongation capacity, and synaptic vesicle trafficking. The expression profile of marker proteins, including β-Tubulin, NeuroD1, Pax6, NeuN, Mnx-1, Isl1, Isl2, Map2, NF, Sox2 was detected to explore the production of developmental regulatory transcription factors and terminal differentiation markers in a time-dependent manner. Cells during differentiation process acquired a fully neural phenotype, which was confirmed by RNA sequencing at the molecular level. The protein expression profile showed neural differentiation induction pathways based on LS-MS/MS analysis. Since NMPs differentiate into spinal cord neuron cells at the developmental stage, the results of this study highlight the further potential of NMP-derived spinal cord neurons in disease modeling and treatment in the clinics.

Keywords:  Cell differentiation; Induced pluripotent stem cells; Neuromesodermal progenitors; Spinal cord neurons

DOI:  https://doi.org/10.1007/s13577-025-01200-3
Commun Biol. 2025 Mar 11. 8(1): 410

Mitochondrial dysfunction drives a neuronal exhaustion phenotype in methylmalonic aciduria.

Matthew C S Denley, Monique S Straub, Giulio Marcionelli, Miriam A Güra, David Penton, Igor Delvendahl, Martin Poms, Beata Vekeriotaite, Sarah Cherkaoui, Federica Conte, Ferdinand von Meyenn, D Sean Froese, Matthias R Baumgartner.

Methylmalonic aciduria (MMA) is an inborn error of metabolism resulting in loss of function of the enzyme methylmalonyl-CoA mutase (MMUT). Despite acute and persistent neurological symptoms, the pathogenesis of MMA in the central nervous system is poorly understood, which has contributed to a dearth of effective brain specific treatments. Here we utilised patient-derived induced pluripotent stem cells and in vitro differentiation to generate a human neuronal model of MMA. We reveal strong evidence of mitochondrial dysfunction caused by deficiency of MMUT in patient neurons. By employing patch-clamp electrophysiology, targeted metabolomics, and bulk transcriptomics, we expose an altered state of excitability, which is exacerbated by application of dimethyl-2-oxoglutarate, and we suggest may be connected to metabolic rewiring. Our work provides first evidence of mitochondrial driven neuronal dysfunction in MMA, which through our comprehensive characterisation of this paradigmatic model, enables first steps to identifying effective therapies.

DOI: https://doi.org/10.1038/s42003-025-07828-z
Trends Cell Biol. 2025 Mar 10. pii: S0962-8924(25)00041-8. [Epub ahead of print]

Cellular homeostatic responses to lysosomal damage.

Jingyue Jia, Suttinee Poolsup, Jay E Salinas.

  Lysosomes are essential membrane-bound organelles that control cellular homeostasis by integrating intracellular functions with external signals. Their critical roles make lysosomal membranes vulnerable to rupture under various stressors, leading to cellular dysfunction. However, the mechanisms by which cells respond to lysosomal damage have only recently begun to be explored. In this review, we summarize the cellular mechanisms activated by lysosomal damage, emphasizing those that restore lysosomal integrity and sustain homeostasis, including recognition, repair, removal, replacement, and remodeling. Drawing on our expertise, we provide an in-depth focus on the remodeling process involved in these responses, including metabolic signaling and stress granule formation. Finally, we discuss the implications of lysosomal damage in human diseases, underscoring potential therapeutic strategies to preserve lysosomal function and alleviate related disorders.

Keywords:  damaged lysosomes; recognition; remodeling; removal; repair; replacement

DOI:  https://doi.org/10.1016/j.tcb.2025.02.007
Nat Aging. 2025 Mar 10.

Subcellular proteomics and iPSC modeling uncover reversible mechanisms of axonal pathology in Alzheimer's disease.

Yifei Cai, Jean Kanyo, Rashaun Wilson, Shveta Bathla, Pablo Leal Cardozo, Lei Tong, Shanshan Qin, Lukas A Fuentes, Iguaracy Pinheiro-de-Sousa, Tram Huynh, Liyuan Sun, Mohammad Shahid Mansuri, Zichen Tian, Hao-Ran Gan, Amber Braker, Hoang Kim Trinh, Anita Huttner, TuKiet T Lam, Evangelia Petsalaki, Kristen J Brennand, Angus C Nairn, Jaime Grutzendler.

Dystrophic neurites (also termed axonal spheroids) are found around amyloid deposits in Alzheimer's disease (AD), where they impair axonal electrical conduction, disrupt neural circuits and correlate with AD severity. Despite their importance, the mechanisms underlying spheroid formation remain incompletely understood. To address this, we developed a proximity labeling approach to uncover the proteome of spheroids in human postmortem and mouse brains. Additionally, we established a human induced pluripotent stem cell (iPSC)-derived AD model enabling mechanistic investigation and optical electrophysiology. These complementary approaches revealed the subcellular molecular architecture of spheroids and identified abnormalities in key biological processes, including protein turnover, cytoskeleton dynamics and lipid transport. Notably, the PI3K/AKT/mTOR pathway, which regulates these processes, was activated in spheroids. Furthermore, phosphorylated mTOR levels in spheroids correlated with AD severity in humans. Notably, mTOR inhibition in iPSC-derived neurons and mice ameliorated spheroid pathology. Altogether, our study provides a multidisciplinary toolkit for investigating mechanisms and therapeutic targets for axonal pathology in neurodegeneration.

DOI: https://doi.org/10.1038/s43587-025-00823-3
Redox Biol. 2025 Feb 19. pii: S2213-2317(25)00072-2. [Epub ahead of print]81 103559

Oxidized protein aggregate lipofuscin impairs cardiomyocyte contractility via late-stage autophagy inhibition.

Sophia Walter, Steffen P Häseli, Patricia Baumgarten, Stefanie Deubel, Tobias Jung, Annika Höhn, Christiane Ott, Tilman Grune.

  Aging of the heart is accompanied by impairment of cardiac structure and function. At molecular level, autophagy plays a crucial role in preserving cardiac health. Autophagy maintains cellular homeostasis by facilitating balanced degradation of cytoplasmic components including organelles and misfolded or aggregated proteins. The age-related decline in autophagy favors an accumulation of protein aggregates such as lipofuscin particularly in the heart, which is composed primarily of non-proliferating cells. Therefore, this study investigates whether lipofuscin accumulation contributes to age-related functional decline of primary adult cardiomyocytes isolated from C57BL/6J mice and examines the role of autophagic flux in mediating these effects. Results showed an age-associated reduction in cardiomyocyte contraction amplitude and an increase in autofluorescence, indicating the accumulation of lipofuscin with age. In vitro treatment of adult primary cardiomyocytes with artificial lipofuscin increased autofluorescence and decreased both contraction amplitude and cellular autophagic flux. Induction of autophagy with rapamycin mitigated contractile dysfunction in lipofuscin-treated cardiomyocytes, whereas inhibition of autophagic flux revealed stage-dependent effects. Late-stage autophagy inhibition using chloroquine or concanamycin A reduced cardiomyocyte contraction amplitude, whereas early-stage autophagy inhibition via 3-methyladenine did not affect contraction within 24 h. In conclusion, our results indicate that lipofuscin directly impairs cardiomyocyte function by diminishing late-stage autophagic flux. These findings highlight the essential role of the autophagy-lysosomal system in preserving age-related loss of cardiomyocyte function caused by accumulating protein aggregates.

Keywords:  Aging; Contraction; Heart; Lysosome

DOI:  https://doi.org/10.1016/j.redox.2025.103559
J Neuroinflammation. 2025 Mar 10. 22(1): 72

Lysosomal acidification impairment in astrocyte-mediated neuroinflammation.

Jialiu Zeng, Jonathan Indajang, David Pitt, Chih Hung Lo.

  Astrocytes are a major cell type in the central nervous system (CNS) that play a key role in regulating homeostatic functions, responding to injuries, and maintaining the blood-brain barrier. Astrocytes also regulate neuronal functions and survival by modulating myelination and degradation of pathological toxic protein aggregates. Astrocytes have recently been proposed to possess both autophagic activity and active phagocytic capability which largely depend on sufficiently acidified lysosomes for complete degradation of cellular cargos. Defective lysosomal acidification in astrocytes impairs their autophagic and phagocytic functions, resulting in the accumulation of cellular debris, excessive myelin and lipids, and toxic protein aggregates, which ultimately contributes to the propagation of neuroinflammation and neurodegenerative pathology. Restoration of lysosomal acidification in impaired astrocytes represent new neuroprotective strategy and therapeutic direction. In this review, we summarize pathogenic factors, including neuroinflammatory signaling, metabolic stressors, myelin and lipid mediated toxicity, and toxic protein aggregates, that contribute to lysosomal acidification impairment and associated autophagic and phagocytic dysfunction in astrocytes. We discuss the role of lysosomal acidification dysfunction in astrocyte-mediated neuroinflammation primarily in the context of neurodegenerative diseases along with other brain injuries. We then highlight re-acidification of impaired lysosomes as a therapeutic strategy to restore autophagic and phagocytic functions as well as lysosomal degradative capacity in astrocytes. We conclude by providing future perspectives on the role of astrocytes as phagocytes and their crosstalk with other CNS cells to impart neurodegenerative or neuroprotective effects.

Keywords:  Acidic nanoparticles; Autophagy; Glial crosstalk; Lysosomal acidification; Lysosomal alkalization; Metabolic dysfunction; Neurodegeneration; Neuroinflammation; Neuroprotective; Phagocytosis

DOI:  https://doi.org/10.1186/s12974-025-03410-w
J Zhejiang Univ Sci B. 2025 Mar 01. pii: 1673-1581(2025)03-0227-13. [Epub ahead of print]26(3): 227-239

Autophagy in skeletal muscle dysfunction of chronic obstructive pulmonary disease: implications, mechanisms, and perspectives.

Xiaoyu Han, Peijun Li, Meiling Jiang, Yuanyuan Cao, Yingqi Wang, Linhong Jiang, Xiaodan Liu, Weibing Wu.

  Skeletal muscle dysfunction is a common extrapulmonary comorbidity of chronic obstructive pulmonary disease (COPD) and is associated with decreased quality-of-life and survival in patients. The autophagy lysosome pathway is one of the proteolytic systems that significantly affect skeletal muscle structure and function. Intriguingly, both promoting and inhibiting autophagy have been observed to improve COPD skeletal muscle dysfunction, yet the mechanism is unclear. This paper first reviewed the effects of macroautophagy and mitophagy on the structure and function of skeletal muscle in COPD, and then explored the mechanism of autophagy mediating the dysfunction of skeletal muscle in COPD. The results showed that macroautophagy- and mitophagy-related proteins were significantly increased in COPD skeletal muscle. Promoting macroautophagy in COPD improves myogenesis and replication capacity of muscle satellite cells, while inhibiting macroautophagy in COPD myotubes increases their diameters. Mitophagy helps to maintain mitochondrial homeostasis by removing impaired mitochondria in COPD. Autophagy is a promising target for improving COPD skeletal muscle dysfunction, and further research should be conducted to elucidate the specific mechanisms by which autophagy mediates COPD skeletal muscle dysfunction, with the aim of enhancing our understanding in this field.

Keywords:  Autophagy; Chronic obstructive pulmonary disease; Mitochondria; Muscle satellite cell; Skeletal muscle dysfunction

DOI:  https://doi.org/10.1631/jzus.B2300680
Clin Chim Acta. 2025 Mar 07. pii: S0009-8981(25)00115-9. [Epub ahead of print] 120236

SNAP-25: A biomarker of synaptic loss in neurodegeneration.

Chaoqun Zhang, Shanshan Xie, Melika Malek.

  Synaptic dysfunction is one of the most important markers of neurodegenerative diseases, which contribute to cognitive decline and the loss of neurons. Synaptosomal-associated protein 25 (SNAP-25) is a member of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, which plays a significant role in the exocytosis of synaptic vesicles and the release of neurotransmitters. Recent studies have shown that expression levels of SNAP-25 are altered in various neurodegenerative disorders, including Alzheimer's disease (AD), Huntington's disease (HD), and Creutzfeldt-Jakob disease (CJD). These investigations led to the consideration of SNAP-25 as a potential biomarker of synaptic degeneration. Understanding the role of SNAP-25 in neurodegeneration will aid in early diagnosis, disease monitoring, and therapeutic development, and will also provide new insights into synaptic dysfunction as a main feature of neurodegenerative diseases. Therefore, this paper explores the physiological role of SNAP-25, its involvement in synaptic pathology, and the implications of its dysregulation in neurodegenerative conditions, such as AD, HD, and CJD. Literature regarding cerebrospinal fluid (CSF) SNAP-25 levels as a diagnostic marker were reviewed and its applications in detecting the progression of the disease have been discussed. Additionally, the limitations of SNAP-25 as a biomarker, including variability across studies and the need for further validation have been addressed.

Keywords:  Biomarker; Diagnosis; Neurodegenerative diseases; Prognostic factor; SNAP-25

DOI:  https://doi.org/10.1016/j.cca.2025.120236
Methods Cell Biol. 2025 ;pii: S0091-679X(24)00143-2. [Epub ahead of print]194 1-17

Labeling of mitochondria for detection of intercellular mitochondrial transfer.

Isamu Taiko, Chika Takano, Shingo Hayashida, Kazunori Kanemaru, Toshio Miki.

  The phenomenon of intercellular transfer of mitochondria has been reported and has attracted significant interest in recent years. The phenomena involve a range of physiological and pathological conditions, such as tumor growth, immunoregulation, and tissue regeneration. There is speculation on the potential restoration of cellular energy status through the transfer of healthy mitochondria from donor cells to cells with impaired mitochondria. Multiple mechanisms and routes of mitochondria transfer have been suggested, including direct cell-to-cell connections, extracellular vesicles, and cell fusion. However, there is limited understanding regarding the precise mechanisms behind mitochondrial transfer, particularly the initiation signals and the associated processes. In order to explore these fundamental mechanisms of mitochondrial transfer, it is imperative to employ techniques that enable direct labeling of mitochondria. Here, we present a detailed methodology utilizing fluorescent protein tagging to visualize mitochondria. The molecular biological techniques applied in this study entail the precise localization of mitochondria with reduced cytotoxicity. This approach facilitates the direct observation of transferred mitochondria through fluorescent and confocal microscopy. The described method can be readily implemented in other mammalian cell types with few modifications, enabling the continuous monitoring of mitochondrial trafficking processes over an extended period.

Keywords:  Amniotic epithelial cells; Mitochondria; Mitochondrial transfer

DOI:  https://doi.org/10.1016/bs.mcb.2024.05.001