Degradation Pathway Research Articles

Blocking autophagosome closure manifests the roles of mammalian Atg8-family proteins in phagophore formation and expansion during nutrient starvation

ABSTRACT Macroautophagy/autophagy, an evolutionarily conserved cellular degradation pathway, involves phagophores that sequester cytoplasmic constituents and mature into autophagosomes for subsequent lysosomal delivery. The ATG8 gene family, comprising the MAP1LC3/LC3 and GABARAP/GBR subfamilies in mammals, encodes ubiquitin-like proteins that are conjugated to phagophore membranes during autophagosome biogenesis. A central question in the field is how Atg8-family proteins are precisely involved in autophagosome formation, which remains controversial and challenging, at least in part due to the short lifespan of phagophores. In this study, we depleted the autophagosome closure regulator VPS37A to arrest autophagy at the vesicle completion step and determined the roles of mammalian Atg8-family proteins (mATG8s) in nutrient starvation-induced autophagosome biogenesis. Our investigation revealed that LC3 loss hinders phagophore formation, while GBR loss impedes both phagophore formation and expansion. The defect in membrane expansion by GBR loss appears to be attributed to compromised recruitment of ATG proteins containing an LC3-interacting region (LIR), including ULK1 and ATG3. Moreover, a combined deficiency of both LC3 and GBR subfamilies nearly completely inhibits phagophore formation, highlighting their redundant regulation of this process. Consequently, cells lacking all mATG8 members exhibit defects in downstream events such as ESCRT recruitment and autophagic flux. Collectively, these findings underscore the critical roles of mammalian Atg8-family proteins in phagophore formation and expansion during autophagy.

Antibiotic amoxicillin degradation by electrochemical oxidation process: effects of process parameters and degradation pathway at environmentally relevant concentrations.

Amoxicillin (AMX) is a common antibiotic used in both human and veterinary medicine in order to both cure and avoid bacterial infections. Traces of AMX have been found in ground and surface water, urban effluents, water, and wastewater treatment facilities due to its widespread use. The level of hazard and disposal of this class of micropollutants is the reason for concern. Advanced technology is required since conventional wastewater treatment plants are ineffective at eliminating these emerging contaminants. Electrochemical oxidation is a promising method of treating wastewater, which uses electrogenerated radicals to mineralize organic pollutants. This work investigated the detailed process mechanism for AMX degradation utilizing a low-cost, thin, flexible graphite sheet with lower AMX concentrations, initial pH value, voltage, electrolyte concentration, and wastewater matrix. The degradation of AMX by in situ generated hydroxyl radicals is a function of applied voltage and follows pseudo-first-order reaction kinetics. The removal efficiencies of AMX have been achieved up to 99% within 3h. Moreover, intermediate by-products have been identified using liquid chromatography-mass spectrometry, and a plausible pathway has been proposed. This study could serve as a process reference for controlling AMX wastewater contamination via the electrochemical oxidation technique.

The role of gut microbiota and metabolomic pathways in modulating the efficacy of SSRIs for major depressive disorder

This study aims to explore the mechanism by which gut microbiota influences the antidepressant effects of serotonin reuptake inhibitors (SSRIs) through metabolic pathways. A total of 126 patients were analyzed for their gut microbiota and metabolomics. Patients received SSRI treatment and were categorized into responder and non-responder groups based on changes in their Hamilton Depression Rating Scale (HAMD-17) scores before and after treatment. The association between gut microbiota composition and the efficacy of SSRIs was investigated through 16S rRNA gene sequencing and metabolomic analysis, and a predictive model was developed. As a result, the study found significant differences in gut microbiota composition between the responder and resistant groups. Specific taxa, such as Ruminococcus, Bifidobacterium, and Faecalibacterium, were more abundant in the responder group. Functional analysis revealed upregulation of acetate degradation and neurotransmitter synthesis pathways in the responder group. The machine learning model indicated that gut microbiota and metabolites are potential biomarkers for predicting SSRIs efficacy. In conclusion, gut microbiota influences the antidepressant effects of SSRIs through metabolic pathways. The diversity and function of gut microbiota can serve as biomarkers for predicting the treatment response, providing new insights for personalized treatment.

Macronucleophagy maintains cell viability under nitrogen starvation by modulating micronucleophagy

Lysosome/vacuole-mediated intracellular degradation pathways, collectively known as autophagy, play crucial roles in the maintenance and regulation of various cellular functions. However, little is known about the relationship between different modes of autophagy. In the budding yeast Saccharomyces cerevisiae, nitrogen starvation triggers both macronucleophagy and micronucleophagy, in which nuclear components are degraded via macroautophagy and microautophagy, respectively. We previously revealed that Atg39-mediated macronucleophagy is important for cell survival under nitrogen starvation; however, the underlying mechanism remains unknown. Here, we reveal that defective Atg39-mediated macronucleophagy leads to the hyperactivation of micronucleophagy, resulting in the excessive transport of various nuclear components into the vacuole. Micronucleophagy occurs at the nucleus–vacuole junction (NVJ). We show that nuclear membrane proteins localized to the NVJ, including Nvj1, which is responsible for micronucleophagy, are degraded via macronucleophagy. Therefore, defective Atg39-mediated macronucleophagy results in the accumulation of Nvj1, which contributes to micronucleophagy enhancement. Blocking micronucleophagy almost completely suppresses cell death caused by the absence of Atg39, whereas enhanced micronucleophagy correlates with death in Atg39-mutant cells under nitrogen starvation. These results suggest that macronucleophagy modulates micronucleophagy in order to prevent the excess removal of nuclear components, thereby maintaining nuclear and cellular homeostasis during nitrogen starvation.

Degradation of cinnamic acid by the rhizosphere strain <i>Achromobacter insolitus</i> LCu2

The Achromobacter insolitus LCu2 strain, isolated from the roots of alfalfa (Medicago sativa L.), utilized cinnamic acid, as well as its methoxy derivatives ‒ vanillic and ferulic acids ‒ as the only carbon source. Weak growth was observed on m-coumaric acid, but not on o- and p-coumaric acids. Growth on cinnamic acid was slow and diauxic. The loss of substrate from the cultivation medium was 53%, the destructive efficiency was 30 μg/mg of raw biomass for 14 days. Despite the bactericidal effect of cinnamic acid, the A. insolitus LCu2 culture remained viable for a long time. Genomic analysis revealed two gene clusters, hca and mhp, responsible for dihydroxylation of the phenyl ring (hcaA1A2CDB) and its subsequent cleavage to central metabolic products (mhpACDE), as well as a transcriptional regulator (hcaR) and a putative transporter (hcaT). A putative biochemical pathway for cinnamic acid degradation by A. insolitus strain LCu2 was predicted using genomic data.

MXenes in Perovskite Solar Cells: Emerging Applications and Performance Enhancements

Perovskite solar cells (PSCs) have emerged as promising candidates for next-generation photovoltaic technology due to their remarkable power-conversion efficiencies (PCEs). Since their introduction, the PCE of PSCs has advanced from 3.8% to over 26%. Nonetheless, challenges pertaining to stability and reliability continue to impede their commercial viability. Recent progress in interface engineering and materials science has underscored the potential of two-dimensional (2D) materials, particularly MXenes, in mitigating these challenges. MXenes represent a class of two-dimensional materials with significant potential for application in PSCs, attributed to their exceptional electrical conductivity, high carrier mobility, remarkable optical transparency, chemical stability, and tunable surface chemical properties. When employed as electron transport layers, MXenes enhance charge transfer and extraction efficiency, leading to substantial improvements in PCEs. Furthermore, their integration into hole transport layers and use as interfacial modifiers contribute to the mitigation of degradation pathways, thereby enhancing device longevity. The unique structural and electronic characteristics of MXenes facilitate their application as transparent electrodes, presenting opportunities for cost reduction and improved optical properties. This review provides a comprehensive overview of the current advancements in MXene-based PSCs, emphasizing significant accomplishments and exploring future research directions aimed at enhancing the efficiency and stability of these devices.

Bilirubin Reductase Shows Host-Specific Associations in Animal Large Intestines.

Animal gastrointestinal tracts contain diverse metabolites, including various host-derived compounds that gut-associated microbes interact with. Here, we explore the diversity and evolution of bilirubin reductase, a bacterial enzyme that metabolizes the host-derived tetrapyrrole bilirubin, performing a key role in the animal heme degradation pathway. Through an analysis of the bilirubin reductase phylogeny and predicted structures, we found that the enzyme family can be divided into three distinct clades with different structural features. Using these clade definitions, we analyzed metagenomic sequencing data from multiple animal species, finding that bilirubin reductase is significantly enriched in the large intestines of animals and that the clades exhibit differences in distribution among animals. Combined with phylogenetic signal analysis, we find that the bilirubin reductase clades exhibit significant associations with specific animals and animal physiological traits like gastrointestinal anatomy and diet. These patterns demonstrate that bilirubin reductase is specifically adapted to the anoxic lower gut environment of animals and that its evolutionary history is complex, involving adaptation to a diverse collection of animals harboring bilirubin-reducing microbes. The findings suggest that bilirubin reductase evolution has been shaped by the host environment, providing a new perspective on heme metabolism in animals and highlighting the importance of the microbiome in animal physiology and evolution.

Imperatorin promotes melanin degradation in keratinocytes through facilitating autophagy via the PI3K/Akt signaling pathway.

Melanin's pivotal role in skin protection and its overproduction leading to hyperpigmentation disorders highlight the necessity of regulating melanogenesis, with autophagy identified as a key degradation pathway. Imperatorin, a compound from Angelica dahurica, has been revealed to reduce melanin in epidermal keratinocytes, with the specific effects and mechanisms unknown. The purpose of this study was to investigate the mechanism by which imperatorin, reduces melanin production in HaCaT cells, with a focus on its potential role in promoting autophagy and regulating the PI3K/Akt signaling pathway. The study used HaCaT cells to investigate the effects of imperatorin on melanin production, autophagy, and PI3K/Akt signaling. Melanin content was measured using a spectrophotometric method. Protein levels of PMEL, ATG1, ATG5, and LC3B II were assessed by Western blotting. Autophagy was further visualized by GFP-LC3B puncta formation. The autophagy inhibitor 3-MA, the PI3K/Akt inhibitor LY294002 and PI3K/Akt activator 740 Y-P were used to assess the role of autophagy and PI3K/Akt signaling in imperatorin's effects. Cell viability was monitored to ensure that imperatorin's effects were not due to cytotoxicity. Imperatorin reduced melanin content in HaCaT cells in a dose-dependent manner without compromising cell viability. This reduction in melanin was accompanied by decreased levels of PMEL protein, a key player in melanosome formation. Additionally, imperatorin promoted autophagy in HaCaT cells, as evidenced by increased levels of autophagy-associated markers ATG1, ATG5, and LC3B II, as well as an increase in GFP-LC3B puncta. The autophagy inhibitor 3-MA partially reversed the effects of imperatorin on both autophagy markers and PMEL levels, indicating that autophagy plays a crucial role in imperatorin's depigmentation action. Furthermore, imperatorin inhibited Akt and mTOR phosphorylation, which are downstream targets of PI3K/Akt signaling, enhancing autophagy and further reducing melanin levels. The PI3K/Akt inhibitor LY294002 amplified imperatorin's effects on PI3K and Akt phosphorylation, autophagy, and melanin levels. While, PI3K/Akt activator 740 Y-P reversed imperatorin's effects on these factors. Imperatorin reduces melanin in HaCaT cells via promoting autophagy and melanin degradation, possibly via the PI3K/Akt signaling. Taken together, imperatorin has the therapeutic potential for the treatment of hyperpigmentation disorders.

Temporal control of acute protein aggregate turnover by UBE3C and NRF1-dependent proteasomal pathways

A hallmark of neurodegenerative diseases (NDs) is the progressive loss of proteostasis, leading to the accumulation of misfolded proteins or protein aggregates, with subsequent cytotoxicity. To combat this toxicity, cells have evolved degradation pathways (ubiquitin-proteasome system and autophagy) that detect and degrade misfolded proteins. However, studying the underlying cellular pathways and mechanisms has remained a challenge, as formation of many types of protein aggregates is asynchronous, with individual cells displaying distinct kinetics, thereby hindering rigorous time-course studies. Here, we merge a kinetically tractable and synchronous agDD-GFP system for aggregate formation with targeted gene knockdowns, to uncover degradation mechanisms used in response to acute aggregate formation. We find that agDD-GFP forms amorphous aggregates by cryo-electron tomography at both early and late stages of aggregate formation. Aggregate turnover occurs in a proteasome-dependent mechanism in a manner that is dictated by cellular aggregate burden, with no evidence of the involvement of autophagy. Lower levels of misfolded agDD-GFP, enriched in oligomers, utilizes UBE3C-dependent proteasomal degradation in a pathway that is independent of RPN13 ubiquitylation by UBE3C. Higher aggregate burden activates the NRF1 transcription factor to increase proteasome subunit transcription and subsequent degradation capacity of cells. Loss or gain of NRF1 function alters the turnover of agDD-GFP under conditions of high aggregate burden. Together, these results define the role of UBE3C in degradation of this class of misfolded aggregation-prone proteins and reveals a role for NRF1 in proteostasis control in response to widespread protein aggregation.

Progress in the Stability of Small Molecule Acceptor-Based Organic Solar Cells.

Significant advancements in power conversion efficiency have been achieved in organic solar cells with small molecule acceptors. However, stability remains a primary challenge, impeding their widespread adoption in renewable energy applications. This review summarizes the degradation of different layers within the device structure in organic solar cells under varying conditions, including light, heat, moisture, and oxygen. For the photoactive layers, the chemical degradation pathways of polymer donors and small molecule acceptors are examined in detail, alongside the morphological stability of the bulk heterojunction structure, which plays a crucial role in device performance. The degradation mechanisms of commonly used anode and cathode interlayers and electrodes are addressed, as these layers significantly influence overall device efficiency and stability. Mitigation methods for the identified degradation mechanisms are provided in each section to offer practical insights for improving device longevity. Finally, an outlook presents the remaining challenges in achieving long-term stability, emphasizing research directions that require further investigation to enhance the reliability and performance of organic solar cells in real-world applications.

Quantifying Heterogeneous Degradation Pathways and Deformation Fields in Solid‐State Batteries

AbstractSolid‐state batteries are compelling candidates for next‐generation energy storage devices, promising both high energy density and improved safety, by utilizing metallic Li as the negative electrode. However, they suffer from poor cyclability and rate capability, which limits their wide application. Degradation in these devices occurs through complex mechanical, chemical and electrochemical pathways, all of which produce heterogeneous deformation fields. Therefore, isolating solid‐state degradation mechanisms, and explicitly linking them to the associated deformation fields requires a multimodal characterization strategy. Here, a novel 3‐D, in situ methodology for linking degradation to deformation in solid‐state cells is presented. X‐ray imaging is used to measure the morphological degradation, and combined with X‐ray diffraction to quantify (electro)chemical aspects. Finally, the heterogeneous stress fields from these various pathways are mapped in situ. This heterogeneity is shown globally, from the interface to the bulk electrolyte, as well as locally, around features such as cracks and voids. Through these analyses, it is possible to delineate the effects of solid electrolyte processing, cell assembly, and cycling on the end‐of‐life state of the cell. Moreover, the importance of stress mitigation in these cells is highlighted, with mean stresses around the interface and some cracks comfortably exceeding the elastic limit of Li.

The Arabidopsis RING-Type E3 Ligase TEAR4 Controls Seed Germination by Targeting RGA for Degradation.

Light and DELLA proteins are central factors controlling seed germination which is critical for seed plant survival and agricultural production. However, the mechanisms underlying DELLA degradation under different light conditions during seed germination remain to be clarified. Here, it is reported that TIE1-ASSOCIATED RING-TYPE E3 LIGASE4 (TEAR4) and other TEARs redundantly promote DELLA degradation to positively regulate seed germination in Arabidopsis. The tear1/2/3/4/5/6 sextuple mutant displayed delayed seed germination under the white or PhyB-dependent light condition, and nearly no seed germination under the PhyA-dependent light condition. The DELLA protein REPRESSOR OF ga1-3 (RGA) accumulated in tear1/2/3/4/5/6, and disruption of RGA and GA-INSENSITIVE (GAI) in tear1/2/3/4/5/6 rescued defective seed germination. Far-red (FR) light rapidly induced TEARs, and TEAR4 is shown to act as an E3 ligase. It is showed that both GA-dependent and TEAR-mediated DELLA degradation pathways are indispensable for PhyA-dependent germination. It is found that TEAR homologs PpTEAR1 and PpTEAR2 from the moss Physcomitrium patens interacted with Arabidopsis DELLAs to promote their degradation, and overexpression of PpTEAR1 or PpTEAR2 completely rescued defective PhyA-dependent seed germination in phya-211. This findings demonstrate that TEARs act as critical players in fine-tuning seed germination, and TEAR-mediated DELLA degradation might be an ancient pathway conserved in plant kingdom.

Advanced MicroRNA delivery for lung inflammatory therapy: surfactant protein A controls cellular internalisation and degradation of extracellular vesicles

IntroductionAlveolar macrophages (AMs) are the first line of defence against pathogens that initiate an inflammatory response in the lungs and exhibit a strong affinity for surfactant protein A (SP-A). Extracellular...

Insights into the Removal of Organic Contaminants by Co-CeO2 Nanocatalysts via CaCO3 Activation: Performance, Kinetic, and Mechanism.

The advanced oxidation process based on S(IV) has garnered increasing attention, owing to its efficiency in degrading contaminants. Here, a cobalt-doped cerium oxide catalyst (Co-CeO2) was employed to activate calcium sulfite (CaSO3) for imidacloprid degradation. The Co-CeO2 catalyst was characterized by using SEM, BET, XRD, and XPS techniques to analyze its structural and chemical properties. XPS analysis revealed the presence of Co0, Co2+, and Co3+ species in the Co-CeO2 catalyst. Compared to the CeO2/CaSO3 system, the Co-CeO2/CaSO3 system significantly enhanced the degradation rate of imidacloprid from 5.00% to 94.01%. Scavenging experiments, in conjunction with electron paramagnetic resonance spectroscopy, identified hydroxyl radicals (•OH), sulfate radicals (SO4•-), superoxide radicals (O2•-), sulfite radicals (SO3•-), and singlet oxygen (1O2) as the primary reactive species responsible for the degradation of imidacloprid within the Co-CeO2/CaSO3 system. Density functional theory calculation analysis was employed to investigate the specific sites of imidacloprid attacked by reactive oxygen species, proposing four potential degradation pathways. Furthermore, the Ecological Structure Activity Relationships (ECOSAR) program predicted a significant diminution in the toxicity of intermediate products compared to imidacloprid. Even after five cycles, Co-CeO2 maintained an excellent removal efficiency of 86.35%.

A review on recent advances in the stability study of anti-mycobacterial drugs.

Several factors, including characteristic polymer composition of the cell wall, based on peptidoglycans cross-linked with arabinogalactans, together with the lipid layer contribute to the high resistance of Mycobacterium tuberculosis to antibiotics and other anti-tuberculosis drugs, leading to the development of new treatment methods. Implementation of therapeutic drug monitoring for anti-mycobacterial drugs in routine clinical practice requires understanding of the limited stability of these drugs. Rifampicin and isoniazid are the main anti-tuberculosis drugs that generate degradation products during sample handling and storage. Therefore, analytical methods used for analysis of clinical samples collected from tuberculosis patients treated with a combination of different drugs should enable the separation of the studied analytes from their metabolites and degradation products. Moreover, the samples require strictly regulated collection and storage conditions to prevent degradation processes. The purpose of this review was to present recent data on the stability studies of anti-mycobacterial drugs, specifically used as first-line treatment in patients with tuberculosis. Detailed degradation pathway of rifampicin was described, including conditions influencing the formation of specific rifampicin related substances. Moreover, the results of the stability studies of anti-mycobacterial drugs were presented in various matrices in conditions determined by international guidance such as U.S. Food and Drug Administration (FDA) or International Council for Harmonisation (ICH) guidelines. Particular attention was given to analytical methods designed for analysis of anti-mycobacterial drugs in the presence of their degradation products. Finally, recommendations proposed by different authors for collection, processing and storage of clinical samples to increase stability of anti-mycobacterial drugs were summarized.

Degradation of Micropollutants in Water by O Atoms Produced by an Atmospheric Pressure He/O2 Plasma Jet

ABSTRACTAn atmospheric pressure He/O2 COST reference microplasma jet was used to study interactions of O atoms with four different organic micropollutants used as target compounds treated by plasma in water (atrazine, carbamazepine, 1,7‐α‐ethinylestradiol, and bisphenol A). Various ratios of O2 to He were used to achieve different exposures of reactive oxygen species to the plasma‐treated micropollutants, and their degradation efficiencies were determined. The degradation of all four micropollutants was merely associated with the variable exposure to the O atom, whereas the role of O3 was minimal. A comprehensive investigation was conducted on the degradation pathways and toxicity reduction assessment of atrazine after the treatment by plasma.

Phycogenic nanoparticles efficiently catalyse pesticide degradation through a novel metabolic pathway utilizing solar light

Cypermethrin (Cy) is a widely used insecticide, leading to significant environmental contamination in homes and agricultural areas. Effective methods to minimize or eliminate insecticidal residues are essential. Seaweeds, traditionally used in agriculture as soil conditioners, offer a promising solution for remediating pesticide-contaminated soils through biogenic nanoparticle synthesis. In this study, we synthesized biogenic silver nanoparticles (UL-AgNPs) from the green seaweed Ulva lactuca Lin (Ulvaceae) to degrade Cypermethrin. The UL-AgNPs were characterized using UV-Visible spectroscopy, Scanning Electron Microscopy equipped with Energy dispersive X-ray spectroscopy, Fourier Transform Infra-red spectroscopy, X-ray diffraction, Dynamic light scattering and zeta potential analysis, confirming their presence, size (81.29 nm), structure and stability. Response surface methodology (RSM) was used to assess the catalytic concentration of photocatalyst for degradation of pesticide including variables, Cy concentration and destined exposure time duration. The degradation efficiency of UL-AgNPs was evaluated, with the highest degradation (91.2%) achieved at pH 7 after 12 hours using 16.6 mg L-1 of UL-AgNPs, following pseudo-first order kinetics with a rate of 2.7 hour-1. GC-MS and UV-Visible spectroscopy revealed a novel degradation pathway, where Cypermethrin was broken down into compounds like Tetradecane, Dodecane, and Tetracosanoic acid through ester cleavage and benzene ring breakdown. The study also demonstrated the reusability of UL-AgNPs for four cycles, highlighting their potential for sustainable environmental management by reducing the long-term hazards of Cypermethrin.

Systematic Metabolic Engineering for Enhanced Cytidine 5'-Monophosphate Production in Escherichia coli.

Cytidine 5'-monophosphate (5'-CMP) is a key intermediate in various nucleotide derivatives and is widely used in the food and pharmaceutical industries. In this study, the titer of 5'-CMP in engineered Escherichia coli CM006, which blocks the degradation pathway of 5'-CMP, increased 134.7-fold compared to E. coli MG1655. Integrated expression of the 5'-CMP diphosphate hydrolase gene nudG significantly enhanced the 5'-CMP titer, reduced orotic acid accumulation, and alleviated feedback inhibition in the 5'-CMP synthesis pathway. By blocking cytidine degradation and increasing carbon flux from cytidine to 5'-CMP, the 5'-CMP titer in E. coli CM011 was increased to 338.2 mg/L. Furthermore, by enhancing the supply of the precursor 5-phospho-α-D-ribose 1-diphosphate (PRPP), the 5'-CMP titer in E. coli CM012 reached 417.9 mg/L, the highest value reported to date. The results and methods presented in this study are of great significance for the sustainable industrial production of 5'-CMP.

Pollution Status, Ecological Effects, and Bioremediation Strategies of Phthalic Acid Esters in Agricultural Ecosystems: A Review.

Phthalic acid esters (PAEs) are common organic contaminants in farmland soil throughout agricultural systems, posing significant threats to human health and thus closely associated with food safety concerns. Here, we consolidate the latest findings regarding the distribution, ecological effects, bioremediation methods, and microbial degradation pathways of PAEs in agricultural ecosystems. Generally, di(2-ethylhexyl) phthalate (DEHP), di-n-butyl phthalate (DnBP), and di-isobutyl phthalate (DiBP) exhibit the highest detection frequencies and concentrations in soil, air and agricultural products. The presence of these PAEs in agricultural ecosystems can significantly affect soil and plant-associated microbial communities, leading to decreased yield and quality of agricultural products. Bioremediation techniques, such as microbial degradation and phytoremediation, are frequently explored to address these issues. Overall, this review provides a comprehensive overview of current research on PAEs in China's agricultural systems and offers insights into potential problems and future research directions.

Dysregulation of protein degradation and alteration of secretome in α-synuclein-exposed astrocytes: implications for dopaminergic neuronal dysfunction

BackgroundA key factor in the propagation of α-synuclein pathology is the compromised protein quality control system. Variations in membrane association and astrocytic uptake between different α-synuclein forms suggest differences in exocytosis or membrane cleavage, potentially impacting the secretome's influence on dopaminergic neurons. We aimed to understand differences in protein degradation mechanisms of astrocytes for both wild-type (WT) and mutant forms of α-synuclein, specifically during periods of reduced degradation efficiency. We also investigated α-synuclein release into the secretome and its effects on healthy dopaminergic neurons.MethodsCellular models used were rat primary astrocytes alongside hiPSC-derived astrocytes, whose impact on rat primary dopaminergic neurons and the human SH-SY5Y cell line was investigated. We examined the release and accumulation of α-synuclein resulting from impaired degradatory pathways, including matrix metalloprotease-MMP9, the ubiquitin proteasomal pathway-UPS, and the autophagy-lysosomal pathway-ALP, using immunocytochemical analysis and flow cytometry. Additionally, we explored the effect of astrocytic secretome on dopaminergic-neuronal survival, neurite collapse and function.ResultsAt early stages, astrocytes were able to deal efficiently with monomeric α-synuclein (via UPS), and larger aggregates (through MMP9 and autophagy), clearing extracellular α-synuclein and maintaining neuronal health. However, extended exposure to extracellular monomeric and aggregated α-synuclein compromised their proteasomal activity, inhibiting MMP9 and destabilizing autophagy, transforming astrocytes from protectors to promoters of neurodegeneration. This study is the first to elucidate the astrocytes' preferred degradation pathways for both monomeric and aggregated forms of α-synuclein, along with the subsequent effects of these payloads on the cellular degradation machinery. The astrocytic transformation is characterized by α-synuclein expulsion, increased release of inflammatory cytokines, and diminished secretion of growth factors leading to dopaminergic neuronal apoptosis and dysfunction, particularly neurite collapse, intracellular Ca2+ response and vesicular dopamine release. The presence of phosphorylated and nitrated α-synuclein species in astrocytes also suggests their potential involvement in modifying both forms of the protein.ConclusionThe initial protective action of astrocytes in clearing and degrading extracellular α-synuclein is severely compromised at latter stages, leading to astrocytic dysfunction and impairing neuron-glia cross-talk. This study underscores the criticality of integrating astrocytes into treatment paradigms in synucleinopathies.