ID: 41580402
Title: Micro-nanoplastics and Parkinson's disease: evidence and perspectives.
Abstract: With the intensification of global plastic pollution, the potential threats posed by micro- and nanoplastics (MPs/NPs) to human health have become a major concern. MPs/NPs enter the organism through ingestion, inhalation, and skin contact, subsequently accumulating in multiple organs-particularly the brain. Increasing experimental and epidemiological evidence implicates MPs/NPs in the development of Parkinson's disease (PD). Preclinical research models indicate that MPs/NPs may accelerate both the initiation and progression of PD by facilitating α-synuclein misfolding and aggregation, triggering neuroinflammatory cascades, elevating oxidative stress, and impairing mitochondrial function. To further investigate the causal role of MPs/NPs in PD, upcoming studies should emphasize well-designed, large-scale prospective cohorts to assess individual exposure to plastic-related pollutants, elucidate the pathways of MPs/NPs into the central nervous system, establish safety thresholds for their neurotoxicity, explore the correlation between exposure levels and central nervous system accumulation, clarify the temporal relationship between MPs/NPs accumulation and PD pathology and symptom onset, and identify the neuropathological mechanisms triggered by relevant concentrations of MPs/NPs. Such data will be instrumental in informing preventive and potentially interventional strategies, while offering actionable insights into the interaction between MPs/NPs and PD.

ID: 41643617
Title: Early-life exposure to polystyrene nanoplastics at ambient doses induces neurotoxicity via mTOR-mediated autophagy-lysosomal dysfunction and proteostasis imbalance.
Abstract: Nanoplastics are an emerging global environmental concern, with increasing evidence of their neurotoxic effects. Recent findings suggest that abnormal aggregation of pathogenic proteins within the nervous system may contribute to the neurotoxicity induced by nanoplastics, yet the molecular mechanisms regulating this pathological cascade remain unclear. Here, we used immature mice as an experimental model to represent infants and young children who are at higher risk of nanoplastics exposure, to elucidate the molecular mechanisms underlying neurotoxicity induced by exposure to polystyrene nanoplastics (PS-NPs) during early life. The results showed that environmentally relevant doses of PS-NPs penetrated the brains of immature mice and induced behavioral and emotional disorders. Proteomic analysis identified the mTOR signaling pathway as a candidate pathway responding to PS-NPs exposure in the immature mouse brain. Rapamycin intervention and quantitative validation further demonstrated that PS-NPs exposure upregulated mTOR signaling, thereby leading to lysosomal dysfunction and a blockade of autophagic flux, which in turn disrupted proteostasis and ultimately caused neurotoxicity. Furthermore, treatment with sodium 4-phenylbutyrate (4-PBA) confirmed that proteostasis imbalance, characterized by activation of the unfolded protein response, was a direct driver of this neurotoxicity. Notably, both rapamycin and 4-PBA treatments alleviated neurotoxicity resulting from PS-NPs exposure by restoring proteostasis. Together, these findings highlight dysregulation of the autophagy-lysosome pathway mediated by mTOR as a central mechanism of PS-NPs-induced neurotoxicity in immature mice and suggest lysosomal regulation for proteostasis remodeling as a prospective therapeutic strategy against neurological hazards related to nanoplastics.

ID: 41659462
Title: PLCβs are recruited to the plasma membrane in macrophages by both Gβγ and Gαq.
Abstract: PLCβ enzymes cleave PIP2 from the plasma membrane, producing IP3 and DAG, which regulate intracellular Ca2+ levels and protein kinase C activity, respectively. They are regulated by GPCR signaling through the G proteins Gβγ and Gαq and have been shown to function as coincidence detectors for dual stimulation of Gαq and Gαi-coupled receptors via these G proteins. PLCβs are aqueous-soluble enzymes, but partition onto the membrane surface to access their lipid substrate. We previously demonstrated that membrane recruitment and orientation of the catalytic core on the membrane surface underlie Gβγ-dependent regulation of PLCβ enzymes. Using macrophages as a model system, where PLCβ signaling is essential for responses to infection and tissue injury, we investigated the contribution of Gβγ-dependent regulation and membrane recruitment of PLCβ in the context of endogenous signaling. By measuring Ca2+ mobilization, we demonstrate that both Gαi and Gαq-coupled receptors independently stimulate PLCβ activity, illustrating that Gβγ alone is sufficient to activate PLCβ in certain contexts. Using total internal reflection and stimulated emission depletion microscopy, we demonstrate that most of the PLCβ3 in the cell is localized away from the plasma membrane at rest but is rapidly recruited to the plasma membrane upon stimulation by both Gαi and Gαq-coupled receptors, illustrating that both Gβγ and Gαq recruit PLCβ to the plasma membrane. These results support an updated model for G protein-dependent regulation of PLCβ enzymes, where Gβγ-induced regulation in the absence of Gαq is context dependent and dictated by the local concentration of receptor, G proteins, and PLCβ. PLCβ enzymes are critical mediators of signal transduction with roles in neuronal, cardiac, and immunological signaling. Despite this importance, many aspects of their function and regulation remain poorly understood. PLCβs are aqueous soluble but must partition onto the membrane surface to access their lipid substrate, which enables regulation at the partitioning step, the catalytic step, or both. We previously demonstrated that membrane recruitment and orientation of the catalytic core on the membrane surface underlie the PLCβ regulation by one effector, Gβγ. Using macrophages as a model system for physiological signaling, we demonstrate that Gβγ is capable of independently activating PLCβ via membrane recruitment under the conditions of endogenous signaling.

ID: 41707395
Title: Polystyrene nanoplastics disrupt ovarian development via cytoskeletal remodeling and epigenetic reprogramming particularly in granulosa cells.
Abstract: Emerging environmental health issues posed by micro- and nanoplastics (M/NPs) have raised significant concerns. Accumulating evidence suggested that M/NPs can bioaccumulate in gonads and impair fertility in animals, yet the underlying cellular mechanisms and tissue-specific responses remain poorly understood. In this study, we employed in vivo and in vitro models to systematically investigate the impact of polystyrene micro- and nanoplastics (PS-M/NPs, 100 nm and 5 µm) on ovarian development and function in pubertal female mice. Following 35-day exposure, we observed size-dependent reproductive toxicity, with 100 nm PS-NPs causing reduced body weight gain and ovarian size, disrupted folliculogenesis, and altered hormone levels. Leveraging single-cell RNA-sequencing (scRNA-seq), we uncovered profound alterations in intracellular communication networks across seven ovarian cell types. Granulosa cells (GCs) were identified as the primary target of PS-NPs, exhibiting marked transcriptional changes, including dysregulation of FSCN1, a critical actin cytoskeleton regulator. In vitro experiments confirmed that only 100 nm PS-NPs were internalized by GCs, leading to cell cycle arrest, necroptosis, and hormonal dysfunction. Mechanistically, PS-NPs triggered F-actin cytoskeleton remodeling, increasing cell stiffness and histone modifications (H3K4me3, H3K27ac) associated with chromatin accessibility. Integrated ATAC-seq and RNA-seq analyses implicated STAT1 as a key transcriptional regulator driving PS-NP-induced epigenetic and transcriptional changes. Overall, our findings establish the first single-cell resolution atlas of PS-NP-mediated ovarian toxicity, revealing that NPs disrupt reproduction through cytoskeletal damage and epigenetic reprogramming. This work provides unprecedented insights into the molecular and epigenetic consequences of M/NPs in mammalian reproduction, emphasizing the potential health risks of environmental M/NP exposure.

ID: 41779229
Title: Palmitoylation Induced Activation of SMAD3 Exacerbates Colitis by Promoting Tissue-resident Memory T Cells Differentiation.
Abstract: Tissue-resident memory T cells (TRM cells) have been shown to play an instrumental role in driving the onset and relapse of inflammatory bowel diseases (IBD). However, the underlying mechanism of TRM cells differentiation and its regulation in intestines remain to be unveiled. Mothers against decapentaplegic homolog 3 (SMAD3) is translocated from nucleus to membrane and activated in response to transforming growth factor beta (TGF-β), which is a key cytokine in the process of TRM cells polarization. Cysteine palmitoylation (S-palmitoylation) is a post-translational modification catalyzed by the DHHC family, regulating protein membrane associations. Genes associated with the classic SMAD3 signaling pathway, along with most genes in the DHHC family, were upregulated in TRM cells. Our study demonstrated that SMAD3 underwent reversible S-palmitoylation on Cys31 by DHHC6, leading to SMAD3 endomembrane recruitment and its subsequent colocalization with TGF-β receptor I (TGF-βRI) under TRM polarization conditions. The membrane recruitment of SMAD3 activated SMAD3 and subsequently upregulated the expression of its target genes, inducing the differentiation of TRM cells. In contrast, perturbation in DHHC6-induced palmitoylation with MYD-4 inhibited TRM cells differentiation and alleviated colitis in IBD model mice. Our work provides an example how the immune responses are regulated through the S-palmitoylation-dependent SMAD3 signaling in TRM cells differentiation and reveals protein S-palmitoylation as a potential target in IBD treatment, which could be of greater application considering the wide involvement of protein S-palmitoylation in the signal transduction in mammalian cells.

ID: 41812834
Title: Brain lipidomics identifies mitochondrial redox dysfunction and metabolic trade-offs associated with Parkinson's disease-like pathology induced by Nanoplastics exposure.
Abstract: Growing nanoplastics exposure raises concern for neurotoxicity, particularly given recent evidence of plastic accumulation within human brain tissue a highly lipid enriched organ, yet effects on brain lipid metabolism remain poorly understood. Here, we employed high-resolution untargeted lipidomics to map brain lipid perturbations in Drosophila melanogaster chronically exposed to polystyrene nanoplastics (PS- NPs). PS-NPs accumulated in fly brains and induced dose-dependent remodeling of mitochondrial membrane lipids, notably cardiolipins and phosphatidylethanolamines, accompanied by increased diacylglycerols/triacylglycerols and monounsaturated fatty acids and by lipid droplet expansion. Guided by these lipidomic signatures, targeted biochemical assays demonstrated depolarized mitochondrial membrane potential, elevated mitochondrial reactive-oxygen species, inhibition of respiratory-chain complexes I and IV, and a shift in NAD(H) and NADP(H) redox couples toward a reduced state and increasing lipid peroxidation. This redox imbalance was accompanied by decreased tyrosine-hydroxylase expression, dopamine depletion, and impaired locomotor behavior, hallmarks of Parkinson's disease (PD)-like neurodegeneration. Dopaminergic neurochemistry was impaired (tyrosine hydroxylase and dopamine decreased), with concomitant reduction of GABA, and locomotor and circadian deficits emerged. Remarkably, co-treatment with the antioxidant N-acetylcysteine (NAC) restored mitochondrial membrane potential, reduced mitochondrial ROS and lipid peroxidation, normalized neutral lipid and MUFA accumulation, and rescued neurotransmitter levels and behavior. Stable-isotope tracing confirmed disrupted TCA cycle flux after NPs exposure that was rescued by NAC. Collectively, these findings reveal lipidomic remodeling as a critical link between environmental NPs exposure and PD-like pathology, highlighting mitochondrial redox-lipid interactions as early determinants and support redox-directed interventions to mitigate risk.

ID: 41886456
Title: UFMylation-dependent inhibition of AKT signaling by PHLDA3 in lung adenocarcinoma.
Abstract: UFMylation, a recently identified ubiquitin-like modification mediated by the E3 ligase UFL1, plays context-specific roles in cancers, but its substrates and functions in lung adenocarcinoma (LUAD) remain poorly defined. Here, we identify the AKT signaling repressor PHLDA3 as a substrate of UFL1 in LUAD. UFMylation of PHLDA3 at Lys51 and Lys106 promotes its membrane localization, thereby blocking AKT membrane recruitment and suppressing downstream signaling. Tumor-associated PHLDA3 mutations F41L, E82G, and K106N impair its UFMylation and membrane translocation, resulting in AKT hyperactivation and enhanced tumor growth. In samples from patients with LUAD, UFL1 expression inversely correlates with phospho-AKT levels. Functionally, the UFL1-PHLDA3 axis inhibits LUAD progression in both cell line-based and patient-derived xenograft models. These findings define a tumor-suppressive UFMylation pathway that modulates AKT activity and provides a mechanistic rationale for targeting UFL1-PHLDA3 signaling in LUAD.

ID: 41919495
Title: Lysosomal homeostasis at the crossroads of neurodegeneration.
Abstract: Lysosomes function as metabolic control centers that integrate degradation, nutrient sensing, and stress signaling. In neurons, which must maintain proteostasis and energetic balance throughout life, lysosomal homeostasis determines cellular resilience. Emerging evidence identifies lysosomal injury and defective repair as common denominators across neurodegenerative diseases. Damage to the lysosomal membrane caused by oxidative stress, lipid imbalance, or genetic mutations triggers a hierarchical quality control cascade. Early lesions recruit the endosomal sorting complex required for transport (ESCRT) machinery for mechanical resealing, while larger ruptures activate lipid-centered recovery modules. When repair fails, lysophagy eliminates irreparable organelles and a TFEB-dependent transcriptional program regenerates the lysosomal pool. These tightly coupled responses safeguard neurons from catastrophic proteostatic collapse. Their impairment, through mutations in lysosomal proteins, or through aging, produces the lysosomal fragility that underlies Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis/frontotemporal dementia, and Huntington disease. Crosstalk between lysosomes, mitochondria, and ER integrates local damage with systemic metabolic adaptation, while dysregulated lysosomal exocytosis and inflammation propagate pathology. Understanding how ESCRT complexes, lipid transport, and transcriptional renewal cooperate to preserve lysosomal integrity reveals unifying principles of neurodegeneration and defines molecular targets for intervention. Restoring lysosomal repair and renewal offers a rational path toward preventing neuronal loss.

ID: 41957923
Title: Enteric Nervous System Damage by Food Contaminants: A Pathway to Neurodegeneration?
Abstract: The enteric nervous system (ENS), a key component of the gut-brain axis, has emerged as a critical player in the pathogenesis of Parkinson's disease (PD). It is the first neural system exposed to food contaminants (FCs)-a diverse group of ubiquitous toxic compounds fortuitously present in food derived from production, processing, storage, or environmental contamination. Emerging evidence suggests that FCs may initiate or amplify neurodegenerative processes, yet their effects on the ENS and their impact in gut-to-brain communication remain insufficiently characterized. This systematic review synthesizes current evidence on FCs-induced effects on the ENS and its involvement in mediating neurotoxicity from dietary toxicants exposure. Following PRISMA guidelines, 67 studies were included pertaining to cellular or mammalian experimental models exposed to FCs via enteral routes, reporting ENS-related outcomes or studying vagal involvement in modulating FC toxicity. The main FCs evaluated were pesticides, toxins, bisphenols, acrylamide, manganese, and micro-/nanoplastics. Across studies, FCs consistently induced neurochemical remodeling of the ENS, activation of enteric glia, often coupled with intestinal alterations. Rotenone, paraquat, and polystyrene micro-/nanoplastics promote α-synuclein aggregation within the ENS and its vagal propagation to the brain. Vagotomy models confirmed that disrupting ENS-CNS communication attenuates FC-related central neurotoxicity, supporting the involvement of food toxicants in gut-to-brain propagation of neurotoxic signals. These findings support the body-first hypothesis of PD and position the ENS as a critical, yet underinvestigated interface in exposome-related neurotoxicology. The review highlights research gaps and the need for improved models and long-term, low-dose studies reflecting realistic FC exposure.

ID: 41980172
Title: Polystyrene Microplastics Induced Hepatocytes Pyroptosis, Apoptosis and Ferroptosis via GSDMD-N-Mediated Mitochondrial Damage.
Abstract: Microplastics (MPs), as emerging food contaminants, have been established to exert adverse effects on the liver. However, the precise toxicological mechanisms remain elusive. Our results demonstrated that MPs triggered mitochondrial dysfunction and mitochondrial ROS (mtROS) accumulation, which subsequently activated NLRP3/caspase-1/GSDMD-N-dependent pyroptosis in hepatocytes. Notably, beyond its canonical translocation to the plasma membrane, GSDMD-N was observed to form pores on the mitochondrial outer membrane, exacerbating mitochondrial damage. The mitochondrial GSDMD-N pores amplified mtROS overproduction, triggering lysosomal membrane permeabilization (LMP) and facilitating lysosomal iron efflux, which ultimately initiated ferroptosis. Concurrently, mitochondrial GSDMD-N mediated mitochondrial intrinsic apoptosis by promoting cytochrome c release and caspase-3 activation. Collectively, our findings revealed that MPs induced GSDMD-N activation and its mitochondrial translocation, which in turn initiated pyroptosis, ferroptosis, and apoptosis in hepatocytes. This study provided novel mechanistic insights into MPs-induced hepatotoxicity, identifying GSDMD-N as a potential central hub coordinating multiple cell death modalities.

ID: 41993512
Title: WDR44 drives de novo α-synuclein aggregation at the lysosomal membrane and promotes neuronal dysfunction in Parkinson's Disease.
Abstract: The aggregation of α-synuclein (α-SYN) into Lewy bodies (LBs) is a central event in the pathogenesis of Parkinson's disease (PD) and related synucleinopathies1,2. Despite significant advances in understanding α-SYN self-assembly, the precise sequence of early aggregation steps has not been directly visualized in living neurons. Here, we use an optogenetic-induced protein aggregation system with a high temporal resolution to monitor the onset of α-SYN assembly in neurons. We found that the initiation and accumulation of α-SYN aggregates occur predominantly at the lysosomal membrane, an event driven by the α-SYN N-terminus and modulated by the membrane-associated adaptor protein WD repeat-containing protein 44 (WDR44). Remarkably, we demonstrate that WDR44 knockdown markedly reduced de novo α-SYN aggregation in both neuronal cultures and in vivo, whereas WDR44 overexpression enhances α-SYN aggregation in PD patient-derived iPSC neurons. Consistent with its potential pathogenic involvement, WDR44 aberrantly accumulates in vivo and in the brains of PD patients, where it colocalizes with LB inclusions. Finally, we show that lysosome-associated α-SYN aggregates compromised lysosomal structure and function, leading to neuronal impairment, a phenotype worsened by WDR44 overexpression, linking early aggregation events to downstream toxicity. Together, these findings reveal the earliest dynamic stages of α-SYN oligomerization in living neurons and identify the WDR44-α-SYN interaction as a promising therapeutic target for reducing α-SYN pathology and enabling early intervention in PD.

ID: 42093006
Title: The emerging role and therapeutic targeting of autophagy-lysosome pathway in the pathogenesis of Parkinson's disease.
Abstract: Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by dopaminergic neuron loss and the accumulation of misfolded α-synuclein, yet the underlying mechanisms remain incompletely understood. Over the past two decades, genetic discoveries have highlighted the convergence of multiple familial PD genes on the autophagy-lysosome pathway (ALP), a key cellular system responsible for the degradation and recycling of intracellular components. Recent studies have further revealed that components of the ALP not only mediate the clearance of α-synuclein aggregates but also, under certain pathological conditions, contribute to their propagation via lysosomal exocytosis or secretory autophagy. The precise functions of autophagy are highly context-dependent, with neuronal and glial cells exhibiting distinct ALP dynamics that shift with development, stress, and aging. In this review, we summarize current knowledge on the physiological regulation of autophagy in the brain and critically examine its involvement in PD pathogenesis, incorporating mechanistic insights from familial models and emerging evidence from sporadic PD. We also explore translational implications, focusing on efforts to identify ALP-related biomarkers in cerebrospinal fluid and urine, and on the therapeutic potential of modulating ALP activity. Although the causality between ALP dysfunction and PD remains elusive, mounting evidence supports its contribution to disease progression, particularly through impaired lysosomal homeostasis and disrupted intracellular trafficking. Future research should aim to define cell type-specific ALP alterations, clarify the bidirectional interactions between α-synuclein and autophagic machinery, and develop in vivo tools to monitor autophagy activity and secretory signatures. A deeper understanding of these processes will be crucial for refining PD models, discovering robust fluid biomarkers, and designing targeted therapies capable of modifying disease trajectory.

ID: 42162239
Title: Atg18 interaction positions Atg2 for efficient lipid transfer into phagophore elongation.
Abstract: During macroautophagy, the de novo formation of the autophagosome at a membrane contact site (MCS) with the endoplasmic reticulum requires directional lipid flux for the growth of the initial phagophore before its sealing into an autophagosome and subsequent fusion with the lysosome/vacuole. It remains unclear, however, how the formation of this specialized MCS and the directionality of the lipid flux are controlled. Here, we present the structure of the key lipid transfer protein Atg2 from yeast solved together with its Atg18 binding partner, a phosphatidylinositol-3-phosphate (PtdIns3P) effector, using cryo-electron microscopy. We reveal a new interface in Atg2 that, together with PtdIns3P, is required for Atg18 recruitment and lipid transfer activity. Furthermore, we visualize lipid densities along the internal hydrophobic cavity of Atg2, providing structural evidence that Atg2 cavity is filled with lipids throughout the entire length, even when Atg2 is cytosolic. Finally, molecular dynamics simulations show that the complex generates membrane curvature, efficiently positioning the lipid channel of Atg2 towards the membrane to promote lipid transfer into the elongating phagophore.

ID: 42165414
Title: High-fat diet exacerbates experimental colitis by inhibiting lysosomal function via the STAT3-TFEB Axis.
Abstract: An elevated risk for inflammatory bowel disease (IBD) has been linked to the intake of high-fat diet (HFD), yet the underlying molecular mechanisms remain unclear. The lysosome and the macroautophagy/autophagy-lysosome pathway (ALP) are critical for maintaining the intestinal epithelial barrier. By employing both an in vivo model of dextran sulfate sodium (DSS)-induced colitis in mice and an in vitro model using lipopolysaccharide (LPS)-treated NCM460 cells, we established that HFD in vivo and palmitic acid (PA) in vitro profoundly impair epithelial barrier function and amplify inflammation, which was linked to the suppression of lysosomal function and the ALP. Mechanistically, HFD in vivo and PA in vitro activated STAT3 (p-STAT3[Y705]) under DSS- and LPS-associated inflammatory stress, respectively. This led to a dual suppression of TFEB: on the one hand, activated STAT3 directly bound to the TFEB promoter to inhibit its transcription; on the other hand, it facilitated the lysosomal recruitment of MTOR and activated MTORC1, which promoted TFEB phosphorylation (p-TFEB[S211]) and hindered its nuclear translocation. This cascade resulted in lysosomal membrane permeabilization (LMP), loss of acidification, and impaired degradative function. Intestinal epithelial-specific knockout of Stat3 or pharmacological activation of TFEB restored lysosomal function, repaired the epithelial barrier, and ameliorated colitis. Conversely, rectal administration of AAV9-shTfeb reversed the protective effects conferred by stat3 knockout. Our study reveals that HFD in vivo and PA in vitro disrupt lysosomal function and the intestinal barrier through the STAT3-TFEB axis, suggesting this signaling pathway as a promising avenue for intervention in diet-associated IBD.Abbreviations: AB-PAS: Alcian blue-periodic acid-Schiff; ALP: autophagy-lysosome pathway; CD: Crohn disease; ChIP: chromatin immunoprecipitation; CLEAR: coordinated lysosomal expression and regulation; DSS: dextran sulfate sodium; HFD: high-fat diet; IBD: inflammatory bowel disease; IF: immunofluorescence; IHC: immunohistochemistry; LAMP: lysosome associated membrane protein; LGALS3/Gal3: galectin 3; LMP: lysosomal membrane permeabilization; LPS: lipopolysaccharide; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin kinase complex 1; PA: palmitic acid; RRAG: Ras-related GTP binding; RRAG-CA: constitutively active RRAG GTPase; RT-qPCR: reverse transcription quantitative PCR; SQSTM1/p62: sequestosome 1; STAT3: signal transducer and activator of transcription 3; TA1: TFEB activator 1; TEM: transmission electron microscopy; TFEB: transcription factor EB; TJ: tight junction; TUNEL: terminal deoxynucleotidyl transferase dUTP nick-end labeling; UC: ulcerative colitis; WB: western blot; WT: wild-type.

ID: 42203786
Title: A PI(3,5)P2/CHMP4B axis on lysosomes is essential for microautophagic degradation of STING.
Abstract: Stimulator of interferon genes (STING) is critical for the type I interferon responses to pathogen- or self-derived cytosolic DNA. STING signalling is terminated by ESCRT-driven lysosomal microautophagy. How STING is directly encapsulated by lysosomes has not yet been understood. Here we show that two lysosomal components, a phosphoinositide PI(3,5)P2 and CHMP4B (a subunit of ESCRT-III subcomplex) are essential for STING encapsulation by lysosomes. Liposome sedimentation assay reveals that CHMP4B binds to PI(3,5)P2. The forced recruitment of the catalytic core of Pikfyve (a lipid kinase generating PI(3,5)P2) to early endosomes, recruits a fraction of CHMP4B to early endosomes. CHMP4B mutant, defective in the binding to PI(3,5)P2, cannot restore the microautophagic degradation of STING or the resolution of the STING signalling in cells depleted of Chmp4b. Our results reveal a molecular mechanism that terminates innate immune signalling at the lysosomal membrane.

ID: 42215790
Title: The C9orf72/SMCR8 complex maintains microglial homeostasis via RAB8A-ESCRT-mediated lysosomal repair.
Abstract: Microglia are critical regulators of neuroinflammation and neurodegeneration. Haploinsufficiency of C9orf72, the most frequently mutated gene in amyotrophic lateral sclerosis and frontotemporal dementia, has been linked to autophagy-lysosomal pathway defects, but the role of C9orf72 in microglia remains unclear. Here, we identify the C9orf72/SMCR8 complex as a key regulator of microglial homeostasis through promoting lysosomal membrane repair. Loss of C9orf72 and SMCR8 in mice causes age‑dependent neuroinflammation and microgliosis, with microglia adopting a disease-associated state. In aged brain and spinal cord tissue, microglia display lysosomal damage marked by galectin‑3 accumulation. Using a lysosomotropic agent to induce lysosomal damage in microglia, we find that C9orf72/SMCR8-deficient cells accumulate damaged lysosomes and show defective recruitment of phosphorylated RAB8A and the Endosomal Sorting Complexes Required for Transport (ESCRT) machinery to damaged lysosomes. Notably, mutant microglia accumulate GTP‑bound RAB8A, which becomes hyperphosphorylated and mislocalized to RAB7-positive, LAMP1-negative vesicles. The GTPase-activating activity of the C9orf72/SMCR8 complex is essential for lysosomal repair. Our findings reveal that the C9orf72/SMCR8 complex coordinates RAB8A-ESCRT-mediated lysosomal repair to safeguard microglial homeostasis and limit neuroinflammation.

ID: 42236937
Title: LASER couples damage sensing to ESCRT assembly for lysosome repair.
Abstract: Lysosomal membrane integrity is essential for cell survival, but how damage sensing is spatiotemporally coupled to repair remains poorly understood. Recruitment and assembly of endosomal sorting complex required for transport (ESCRT) I-III rapidly counteracts membrane damage, but it is unclear how ESCRT-I recognizes defective lysosomal membranes. Here, leveraging genome-wide CRISPRi screens in a damage-sensitized genetic background, we identified LC3/GABARAP-assisted stimulator for ESCRT recruitment (LASER), a multicomponent protein assembly that forms rapidly upon calcium release from damaged lysosomes and couples sensing of lysosomal membrane damage to ESCRT-dependent repair. At the core of LASER is TFG, an endoplasmic reticulum exit-site-resident protein that translocates to damaged lysosomes by binding to ATG8 family proteins (LC3 and GABARAP) conjugated to lysosomal phospholipids. ATG8-bound TFG forms oligomeric assemblies that directly recruit the essential ESCRT-I subunit TSG101 via conserved motif recognition enhanced by avidity-driven interactions. TFG binding to TSG101 stimulates sequential ESCRT-I-II-III polymerization and promotes membrane repair. TFG mutations that drive hereditary spastic paraplegia disrupt its oligomerization and impair lysosomal ESCRT recruitment and membrane resealing, implicating defective repair as a driver of TFG-associated neurodegeneration. Thus, LASER promotes ESCRT polymerization at damaged lysosomes and couples damage sensing to membrane repair.

ID: 42325197
Title: Small bites for big problems: stepwise aggregate degradation by autophagy.
Abstract: Protein aggregates are a pathological hallmark of diverse disorders, including many neurodegenerative diseases, but also cardiometabolic disease and cancer. While the ubiquitin-proteasome system efficiently removes many soluble misfolded proteins, large or persistent assemblies often require the autophagy-lysosome pathway for their degradation. In the present mini-review, we summarize our knowledge of aggrephagy, the selective clearance of protein aggregates by autophagy, and discuss two recent manuscripts that argue that some aggregates must be primed for autophagosomal degradation, through chaperone-mediated remodeling. Aggrephagy substrates are defined by aggregate architecture, biophysical state, surface accessibility, and the physical constraints of membrane capture. These features help to explain why recruitment of selective autophagy receptors is necessary yet insufficient for clearance. Receptor clustering is required to concentrate early autophagy factors to establish initiation hubs, but successful degradation often requires upstream generation of smaller 'aggrephagy-competent' cargo units, which contain autophagy receptor clusters that successfully initiate autophagosome formation. Recent work supports a model in which larger aggregates are cleared through stepwise degradation enabled by prior remodeling steps that involve p97/VCP-driven disintegration or a chaperone module (DNAJB6-HSP70-HSP110) cooperating with the proteasomal 19S regulatory particle.

ID: 42327061
Title: Lipid transfer protein ORP3 mediates lysosomal repair via LC3B and ubiquitin-TAK1-p38 signaling.
Abstract: Lysosomal membrane damage triggers a multi-stage repair response essential for cellular homeostasis. Here we identify the oxysterol-binding protein-related protein ORP3 as a critical mediator of late-stage lysosomal membrane repair. Following lysosomal damage induced by L-leucine-leucine methyl ester (LLOME) or cationic amphiphilic drugs (CADs), ORP3 is phosphorylated and recruited to ER-lysophagosome contact sites via a signaling cascade initiated by lysosomal membrane ubiquitination, TAK1, p38 MAPK, and, to a lesser extent, IKK. p38-dependent phosphorylation promotes direct interaction between ORP3 and LC3B, which together with PI(4,5)P₂ binding, is required for autophagic lysosome recruitment. ORP3 depletion impairs late-stage lysosomal recovery, elevates lysosomal lipid peroxidation, and reduces cell survival. A lipid transfer-deficient ORP3 mutant fails to restore lysosome function despite normal recruitment, indicating that ER-to-lysophagosome transfer of phosphatidylcholine by ORP3 is functionally required. ORP3 activity is subsequently terminated by VCP/p97-mediated deubiquitination of lysosomes. These findings define ORP3 as a MAPK regulated lipid transfer protein during the late autophagic phase of the endolysosomal damage response. Lysosomal membrane damage triggers ubiquitination that activates a TAK1-p38 signaling cascade, phosphorylating the lipid transfer protein ORP3 and recruiting it to damaged lysosomes via LC3B interaction. ORP3-mediated phosphatidylcholine transfer from the ER is essential for late-stage lysosomal repair and cell survival.

ID: 42477140
Title: Mitochondrial-derived vesicles drive budding-type fission of damaged lysosomes.
Abstract: Lysosomes are central degradative organelles essential for cellular homeostasis, yet the mechanisms that maintain their integrity and function under stress remain incompletely understood. Here we identify a previously unrecognized lysosomal renewal process, termed budding-type fission (B-fission), which restores lysosomal function during hypoxia-reoxygenation stress. During B-fission, damaged lysosomes generate membrane buds that undergo scission to form small, fully functional lysosomes, independently of autophagic lysosome reformation. Mechanistically, mitochondrial-derived vesicles (MDVs) deliver the fission adaptor MFF to lysosomes, where MFF recruits the dynamin-related GTPase DRP1 to drive membrane scission. MIRO2 promotes the formation of MFF+ MDVs through direct interaction with MFF, while the lysosomal membrane protein ITM2C binds MIRO2 to tether and guide MFF+ MDVs to lysosomes, enabling efficient MFF delivery and subsequent B-fission. Notably, AMPK activation by 991 or metformin promotes MFF-dependent lysosomal B-fission under normoxic conditions, whereas AMPK inhibition by dorsomorphin suppresses B-fission during hypoxia-reoxygenation. This stress-responsive ITM2C-MIRO2-MFF-DRP1 axis co-opts the mitochondrial division machinery to drive lysosomal fission from damaged lysosomes, thereby enabling the undamaged components to reorganize into daughter lysosomes and promote lysosomal renewal. Thus, our findings uncover a fundamental mode of lysosomal renewal and reveal an unexpected role for MDV-mediated mitochondria-lysosome communication in mediating lysosomal quality control during ischaemia-reperfusion and related stresses.