Autophagosome-Lysosome Fusion

Lysosomal dysfunction-derived autophagy impairment of gingival epithelial cells in diabetes-associated periodontitis with altered protein acetylation

Diabetes-associated periodontitis (DP) presents severe inflammation and resistance to periodontal conventional treatment, presenting a significant challenge in clinical management. In this study, we investigated the underlying mechanism driving the hyperinflammatory response in gingival epithelial cells (GECs) of DP patients. Our findings indicate that lysosomal dysfunction under high glucose conditions leads to the blockage of autophagy flux, exacerbating inflammatory response in GECs. Single-cell RNA sequencing and immunohistochemistry analyses of clinical gingival epithelia revealed dysregulation in the lysosome pathway characterized by reduced levels of lysosome-associated membrane glycoprotein 2 (LAMP2) and V-type proton ATPase 16 kDa proteolipid subunit c (ATP6V0C) in subjects with DP. In vitro stimulation of human gingival epithelial cells (HGECs) with a hyperglycemic microenvironment showed elevated release of proinflammatory cytokines, compromised lysosomal acidity and blocked autophagy. Moreover, HGECs with deficiency in ATP6V0C demonstrated impaired autophagy and heightened inflammatory response, mirroring the effects of high glucose stimulation. Proteomic analysis of acetylation modifications identified altered acetylation levels in 28 autophagy-lysosome pathway-related proteins and 37 sites in HGECs subjected to high glucose stimulation or siATP6V0C. Overall, our finding highlights the pivotal role of lysosome impairment in autophagy obstruction in DP and suggests a potential impact of altered acetylation of relevant proteins on the interplay between lysosome dysfunction and autophagy blockage. These insights may pave the way for the development of effective therapeutic strategies against DP.

Exploring the Underlying Mechanisms of Qingxing Granules Treating H1N1 Influenza Based on Network Pharmacology and Experimental Validation

BACKGROUND

H1N1 is one of the major subtypes of influenza A virus (IAV) that causes seasonal influenza, posing a serious threat to human health. A traditional Chinese medicine combination called Qingxing granules (QX) is utilized clinically to treat epidemic influenza. However, its chemical components are complex, and the potential pharmacological mechanisms are still unknown.

METHODS

QX's effective components were gathered from the TCMSP database based on two criteria: drug-likeness (DL ≥ 0.18) and oral bioavailability (OB ≥ 30%). SwissADME was used to predict potential targets of effective components, and Cytoscape was used to create a "Herb-Component-Target" network for QX. In addition, targets associated with H1N1 were gathered from the databases GeneCards, OMIM, and GEO. Targets associated with autophagy were retrieved from the KEGG, HAMdb, and HADb databases. Intersection targets for QX, H1N1 influenza, and autophagy were identified using Venn diagrams. Afterward, key targets were screened using Cytoscape's protein-protein interaction networks built using the database STRING. Biological functions and signaling pathways of overlapping targets were observed through GO analysis and KEGG enrichment analysis. The main chemical components of QX were determined by high-performance liquid chromatography (HPLC), followed by molecular docking. Finally, the mechanism of QX in treating H1N1 was validated through animal experiments.

RESULTS

A total of 786 potential targets and 91 effective components of QX were identified. There were 5420 targets related to H1N1 and 821 autophagy-related targets. The intersection of all targets of QX, H1N1, and autophagy yielded 75 intersecting targets. Ultimately, 10 core targets were selected: BCL2, CASP3, NFKB1, MTOR, JUN, TNF, HSP90AA1, EGFR, HIF1A, and MAPK3. Identification of the main chemical components of QX by HPLC resulted in the separation of seven marker ingredients within 195 min, which are amygdalin, puerarin, baicalin, phillyrin, wogonoside, baicalein, and wogonin. Molecular docking results showed that BCL2, CASP3, NFKB1, and MTOR could bind well with the compounds. In animal studies, QX reduced the degenerative alterations in the lung tissue of H1N1-infected mice by upregulating the expression of p-mTOR/mTOR and p62 and downregulating the expression of LC3, which inhibited autophagy.

CONCLUSIONS

According to this study's network pharmacology analysis and experimental confirmation, QX may be able to treat H1N1 infection by regulating autophagy, lowering the expression of LC3, and increasing the expression of p62 and p-mTOR/mTOR.

Functional role of autophagy in testicular and ovarian steroidogenesis

Autophagy is an evolutionarily conserved cellular recycling process that maintains cellular homeostasis. Despite extensive research in endocrine contexts, the role of autophagy in ovarian and testicular steroidogenesis remains elusive. The significant role of autophagy in testosterone production suggests potential treatments for conditions like oligospermia and azoospermia. Further, influence of autophagy in folliculogenesis, ovulation, and luteal development emphasizes its importance for improved fertility and reproductive health. Thus, investigating autophagy in gonadal cells is clinically significant. Understanding these processes could transform treatments for endocrine disorders, enhancing reproductive health and longevity. Herein, we provide the functional role of autophagy in testicular and ovarian steroidogenesis to date, highlighting its modulation in testicular steroidogenesis and its impact on hormone synthesis, follicle development, and fertility therapies.

Mangiferin attenuates lipopolysaccharide-induced neuronal injuries in primary cultured hippocampal neurons

Mangiferin, a naturally occurring potent glucosylxanthone, is mainly isolated from the Mangifera indica plant and shows potential pharmacological properties, including anti-bacterial, anti-inflammation, and antioxidant in sepsis-induced lung and kidney injury. However, there was a puzzle as to whether mangiferin had a protective effect on sepsis-associated encephalopathy. To answer this question, we established an in vitro cell model of sepsis-associated encephalopathy and investigated the neuroprotective effects of mangiferin in primary cultured hippocampal neurons challenged with lipopolysaccharide (LPS). Neurons treated with 20 μmol/L or 40 μmol/L mangiferin for 48 h can significantly reverse cell injuries induced by LPS treatment, including improved cell viability, decreased inflammatory cytokines secretion, relief of microtubule-associated light chain 3 expression levels and several autophagosomes, as well as attenuated cell apoptosis. Furthermore, mangiferin eliminated pathogenic proteins and elevated neuroprotective factors at both the mRNA and protein levels, showing strong neuroprotective effects of mangiferin, including anti-inflammatory, anti-autophagy, and anti-apoptotic effects on neurons in vitro.

Antioxidants activities of phytochemicals perspective modulation of autophagy and apoptosis to treating cancer

The study of chemicals extracted from natural sources should be encouraged due to the significant number of cancer deaths each year and the financial burden imposed by this disease on society. The causes of almost all cancers involve a combination of lifestyle, environmental factors, and genetic and inherited factors. Modern medicine researchers are increasingly interested in traditional phytochemicals as they hold potential for new bioactive compounds with medical applications. Recent publications have provided evidence of the antitumor properties of phytochemicals, a key component of traditional Chinese medicine, thereby opening new avenues for their use in modern medicine. Various studies have demonstrated a strong correlation between apoptosis and autophagy, two critical mechanisms involved in cancer formation and regulation, indicating diverse forms of crosstalk between them. Phytochemicals have the ability to activate both pro-apoptotic and pro-autophagic pathways. Therefore, understanding how phytochemicals influence the relationship between apoptosis and autophagy is crucial for developing a new cancer treatment strategy that targets these molecular mechanisms. This review aims to explore natural phytochemicals that have demonstrated anticancer effects, focusing on their role in regulating the crosstalk between apoptosis and autophagy, which contributes to uncontrolled tumor cell growth. Additionally, the review highlights the limitations and challenges of current research methodologies while suggesting potential avenues for future research in this field.

Mitochondrial derived vesicle-carrying protein MIGA2 promotes copper-induced autophagosomes-lysosomes fusion by regulating ATG14

As an environmental pollution metal, copper (Cu) exposure-induced toxicity is closely related to mitochondrial damage. Mitochondrial-derived vesicles (MDVs) plays an essential role in mitochondrial quality control and cellular metabolism. However, the mechanism by which MDVs are involved in cellular metabolism under Cu exposure remains unclear. Here, the MDV-carrying protein MIGA2 was identified as a crucial molecule involved in the Cu-induced autophagosomes-lysosomes fusion. Furthermore, Cu exposure significantly promoted MDVs secretion, accompanied by a markedly increased MIGA2 expression in MDVs, as well as accelerated the autophagosomes-lysosomes fusion. However, small RNA interference of SNX9 (the MDVs secretion inductor) and MIGA2 blocked autophagic flux induced by Cu, leading to failure of autophagosomes degradation. Co-immunoprecipitation assay further demonstrated that ATG14 was a regulation target protein of MIGA2. Overexpression and knockdown of ATG14 significantly affected the autophagosomes-lysosomes fusion induced by Cu. Meanwhile, knockdown of ATG14 dramatically reversed the effect of MIGA2-overexpression in promoting autophagosomes-lysosomes fusion, while overexpression of ATG14 shows the opposite effect. These results demonstrated that MDVs-carrying MIGA2 protein promoted autophagosomes-lysosomes fusion induced by Cu. This study demonstrated that MDVs is involved in regulating organelles-to-organelles communication, providing a new insight into the toxicity mechanism of Cu exposure on hepatocytes.

A conserved requirement for RME-8/DNAJC13 in neuronal autophagic lysosome reformation

Autophagosomes fuse with lysosomes, forming autolysosomes that degrade engulfed cargo. To maintain lysosomal capacity, autophagic lysosome reformation (ALR) must regenerate lysosomes from autolysosomes using a membrane tubule-based process. Maintaining lysosomal capacity is required to maintain cellular health, especially in neurons where lysosomal dysfunction has been repeatedly implicated in neurodegenerative disease. The DNA-J domain HSC70 co-chaperone RME-8/DNAJC13 has been linked to endosomal coat protein regulation and to neurological disease. We report new analysis of the requirements for the RME-8/DNAJC13 protein in neurons, focusing on intact C. elegans mechanosensory neurons, and primary mouse cortical neurons in culture. Loss of RME-8/DNAJC13 in both systems results in accumulation of grossly elongated autolysosomal tubules. Further C. elegans analysis revealed a similar autolysosome tubule accumulation defect in mutants known to be required for ALR in mammals, including mutants lacking bec-1/BECN1/Beclin1 and vps-15/PIK3R4/p150 that regulate the class III phosphatidylinositol 3-kinase (PtdIns3K) VPS-34, and dyn-1/dynamin that severs ALR tubules. Clathrin is also an important ALR regulator implicated in autolysosome tubule formation and release. In C. elegans we found that loss of RME-8 causes severe depletion of clathrin from neuronal autolysosomes, a phenotype shared with bec-1 and vps-15 mutants. We conclude that RME-8/DNAJC13 plays a previously unrecognized role in ALR, likely affecting autolysosome tubule severing. Additionally, in both systems, loss of RME-8/DNAJC13 reduced macroautophagic/autophagic flux, suggesting feedback regulation from ALR to autophagy. Our results connecting RME-8/DNAJC13 to ALR and autophagy provide a potential mechanism by which RME-8/DNAJC13 could influence neuronal health and the progression of neurodegenerative disease.Abbreviation: ALR, autophagic lysosome reformation; ATG-13/EPG-1, AuTophaGy (yeast Atg homolog)-13; ATG-18, AuTophaGy (yeast Atg homolog)-18; AV, autophagic vacuole; CLIC-1, Clathrin Light Chain-1; EPG-3, Ectopic P Granules-3; EPG-6, Ectopic P Granules-6; LGG-1, LC3, GABARAP and GATE-16 family-1; MAP1LC3/LC3, microtubule-associated protein 1 light chain 3; PD, Parkinson disease; PtdIns3P, phosphatidylinositol-3-phosphate; PtdIns(4,5)P2, phosphatidylinositol-4,5-bisphosphate; RME-8, Receptor Mediated Endocytosis-8; SNX-1, Sorting NeXin-1; VPS-34, related to yeast Vacuolar Protein Sorting factor-34.

Recent insights about autophagy in pancreatitis

Acute pancreatitis is a common inflammatory gastrointestinal disease without any successful treatment. Pancreatic exocrine acinar cells have high rates of protein synthesis to produce and secrete large amounts of digestive enzymes. When the regulation of organelle and protein homeostasis is disrupted, it can lead to endoplasmic reticulum (ER) stress, damage to the mitochondria and improper intracellular trypsinogen activation, ultimately resulting in acinar cell damage and the onset of pancreatitis. To balance the homeostasis of organelles and adapt to protect themselves from organelle stress, cells use protective mechanisms such as autophagy. In the mouse pancreas, defective basal autophagy disrupts ER homoeostasis, leading to ER stress and trypsinogen activation, resulting in spontaneous pancreatitis. In this review, we discuss the regulation of autophagy and its physiological role in maintaining acinar cell homeostasis and function. We also summarise the current understanding of the mechanisms and the role of defective autophagy at multiple stages in experimental pancreatitis induced by cerulein or alcohol.

Molecular Mechanism of Autophagosome-Lysosome Fusion in Mammalian Cells

In eukaryotes, targeting intracellular components for lysosomal degradation by autophagy represents a catabolic process that evolutionarily regulates cellular homeostasis. The successful completion of autophagy initiates the engulfment of cytoplasmic materials within double-membrane autophagosomes and subsequent delivery to autolysosomes for degradation by acidic proteases. The formation of autolysosomes relies on the precise fusion of autophagosomes with lysosomes. In recent decades, numerous studies have provided insights into the molecular regulation of autophagosome-lysosome fusion. In this review, an overview of the molecules that function in the fusion of autophagosomes with lysosomes is provided. Moreover, the molecular mechanism underlying how these functional molecules regulate autophagosome-lysosome fusion is summarized.

Lysosomes in Cancer-At the Crossroad of Good and Evil

Although it has been known for decades that lysosomes are central for degradation and recycling in the cell, their pivotal role as nutrient sensing signaling hubs has recently become of central interest. Since lysosomes are highly dynamic and in constant change regarding content and intracellular position, fusion/fission events allow communication between organelles in the cell, as well as cell-to-cell communication via exocytosis of lysosomal content and release of extracellular vesicles. Lysosomes also mediate different forms of regulated cell death by permeabilization of the lysosomal membrane and release of their content to the cytosol. In cancer cells, lysosomal biogenesis and autophagy are increased to support the increased metabolism and allow growth even under nutrient- and oxygen-poor conditions. Tumor cells also induce exocytosis of lysosomal content to the extracellular space to promote invasion and metastasis. However, due to the enhanced lysosomal function, cancer cells are often more susceptible to lysosomal membrane permeabilization, providing an alternative strategy to induce cell death. This review summarizes the current knowledge of cancer-associated alterations in lysosomal structure and function and illustrates how lysosomal exocytosis and release of extracellular vesicles affect disease progression. We focus on functional differences depending on lysosomal localization and the regulation of intracellular transport, and lastly provide insight how new therapeutic strategies can exploit the power of the lysosome and improve cancer treatment.

Targeting autophagy drug discovery: Targets, indications and development trends

Autophagy plays a vital role in sustaining cellular homeostasis and its alterations have been implicated in the etiology of many diseases. Drugs development targeting autophagy began decades ago and hundreds of agents were developed, some of which are licensed for the clinical usage. However, no existing intervention specifically aimed at modulating autophagy is available. The obstacles that prevent drug developments come from the complexity of the actual impact of autophagy regulators in disease scenarios. With the development and application of new technologies, several promising categories of compounds for autophagy-based therapy have emerged in recent years. In this paper, the autophagy-targeted drugs based on their targets at various hierarchical sites of the autophagic signaling network, e.g., the upstream and downstream of the autophagosome and the autophagic components with enzyme activities are reviewed and analyzed respectively, with special attention paid to those at preclinical or clinical trials. The drugs tailored to specific autophagy alone and combination with drugs/adjuvant therapies widely used in clinical for various diseases treatments are also emphasized. The emerging drug design and development targeting selective autophagy receptors (SARs) and their related proteins, which would be expected to arrest or reverse the progression of disease in various cancers, inflammation, neurodegeneration, and metabolic disorders, are critically reviewed. And the challenges and perspective in clinically developing autophagy-targeted drugs and possible combinations with other medicine are considered in the review.

Protein turnover in pigs: A review of interacting factors

Protein turnover defines the balance between two continuous and complex processes of protein metabolism, synthesis and degradation, which determine their deposition in tissues. Although the liver and intestine have been studied extensively for their important roles in protein digestion, absorption and metabolism, the study of protein metabolism has focused mainly on skeletal muscle tissue to understand the basis for its growth. Due to the high adaptability of skeletal muscle, its protein turnover is greatly affected by different internal and external factors, contributing to carcass lean-yield and animal growth. Amino acid (AA) labelling and tracking using isotope tracer methodology, together with the study of myofiber type profiling, signal transduction pathways and gene expression, has allowed the analysis of these mechanisms from different perspectives. Positive stimuli such as increased nutrient availability in the diet (e.g., AA), physical activity, the presence of certain hormones (e.g., testosterone) or a more oxidative myofiber profile in certain muscles or pig genotypes promote increased upregulation of translation and transcription-related genes, activation of mTORC1 signalling mechanisms and increased abundance of satellite cells, allowing for more efficient protein synthesis. However, fasting, animal aging, inactivity and stress, inflammation or sepsis produce the opposite effect. Deepening the understanding of modifying factors and their possible interaction may contribute to the design of optimal strategies to better control tissue growth and nutrient use (i.e., protein and AA), and thus advance the precision feeding strategy.

Biomarker cystatin B expression correlates with pathogenesis in cervical cancer

OBJECTIVE

Cervical cancer (CC) is one of the most common gynecologic malignancies worldwide. Although rapid improvements have been made regarding its prevention and treatment, little is known about disease pathogenesis and the clinical relevance of reliable biomarkers. The present study evaluated the expression of cystatin B (CSTB) as a potential biomarker of CC.

METHODS

Tissue microarray analysis and immunohistochemical staining were performed to detect CSTB expression, while CSTB mRNA and protein expression levels of freshly isolated CC tissue were measured by quantitative real-time PCR and western blot, respectively. Bioinformatics were used to analyze the CSTB co-expression network and functional enrichments.

RESULTS

We observed high CSTB mRNA and protein expression levels in CC tissues, which was confirmed by tissue microarray in a comparison with paired adjacent non-cancerous cervical tissue samples. CSTB gene enrichments and associations with co-expressed genes were also observed. Further analysis showed that elevated CSTB expression was associated with pathological progress in CC.

CONCLUSION

Our data demonstrate that CSTB has the potential to be used as a tissue biomarker with clinical value in patients with CC, which may aid the development of intervention strategies.

Lysosomes as coordinators of cellular catabolism, metabolic signalling and organ physiology

Every cell must satisfy basic requirements for nutrient sensing, utilization and recycling through macromolecular breakdown to coordinate programmes for growth, repair and stress adaptation. The lysosome orchestrates these key functions through the synchronised interplay between hydrolytic enzymes, nutrient transporters and signalling factors, which together enable metabolic coordination with other organelles and regulation of specific gene expression programmes. In this Review, we discuss recent findings on lysosome-dependent signalling pathways, focusing on how the lysosome senses nutrient availability through its physical and functional association with mechanistic target of rapamycin complex 1 (mTORC1) and how, in response, the microphthalmia/transcription factor E (MiT/TFE) transcription factors exert feedback regulation on lysosome biogenesis. We also highlight the emerging interactions of lysosomes with other organelles, which contribute to cellular homeostasis. Lastly, we discuss how lysosome dysfunction contributes to diverse disease pathologies and how inherited mutations that compromise lysosomal hydrolysis, transport or signalling components lead to multi-organ disorders with severe metabolic and neurological impact. A deeper comprehension of lysosomal composition and function, at both the cellular and organismal level, may uncover fundamental insights into human physiology and disease.

Loss of the HOPS complex disrupts early-to-late endosome transition, impairs endosomal recycling and induces accumulation of amphisomes

The multisubunit HOPS tethering complex is a well-established regulator of lysosome fusion with late endosomes and autophagosomes. However, the role of the HOPS complex in other stages of endo-lysosomal trafficking is not well understood. To address this, we made HeLa cells knocked out for the HOPS-specific subunits Vps39 or Vps41, or the HOPS-CORVET-core subunits Vps18 or Vps11. In all four knockout cells, we found that endocytosed cargos were trapped in enlarged endosomes that clustered in the perinuclear area. By correlative light-electron microscopy, these endosomes showed a complex ultrastructure and hybrid molecular composition, displaying markers for early (Rab5, PtdIns3P, EEA1) as well as late (Rab7, CD63, LAMP1) endosomes. These "HOPS bodies" were not acidified, contained enzymatically inactive cathepsins and accumulated endocytosed cargo and cation-independent mannose-6-phosphate receptor (CI-MPR). Consequently, CI-MPR was depleted from the TGN, and secretion of lysosomal enzymes to the extracellular space was enhanced. Strikingly, HOPS bodies also contained the autophagy proteins p62 and LC3, defining them as amphisomes. Together, these findings show that depletion of the lysosomal HOPS complex has a profound impact on the functional organization of the entire endosomal system and suggest the existence of a HOPS-independent mechanism for amphisome formation.

α-Synuclein: Multiple pathogenic roles in trafficking and proteostasis pathways in Parkinson's disease

Parkinson's disease (PD) is a common age-related neurodegenerative disorder characterized by the loss of dopaminergic neurons in the midbrain. A hallmark of both familial and sporadic PD is the presence of Lewy body inclusions composed mainly of aggregated α-synuclein (α-syn), a presynaptic protein encoded by the SNCA gene. The mechanisms driving the relationship between α-syn accumulation and neurodegeneration are not completely understood, although recent evidence indicates that multiple branches of the proteostasis pathway are simultaneously perturbed when α-syn aberrantly accumulates within neurons. Studies from patient-derived midbrain cultures that develop α-syn pathology through the endogenous expression of PD-causing mutations show that proteostasis disruption occurs at the level of synthesis/folding in the endoplasmic reticulum (ER), downstream ER-Golgi trafficking, and autophagic-lysosomal clearance. Here, we review the fundamentals of protein transport, highlighting the specific steps where α-syn accumulation may intervene and the downstream effects on proteostasis. Current therapeutic efforts are focused on targeting single pathways or proteins, but the multifaceted pathogenic role of α-syn throughout the proteostasis pathway suggests that manipulating several targets simultaneously will provide more effective disease-modifying therapies for PD and other synucleinopathies.

The crustacean DNA virus tegument protein VP26 binds to SNAP29 to inhibit SNARE complex assembly and autophagic degradation

Autophagy generally functions as a cellular surveillance mechanism to combat invading viruses, but viruses have evolved various strategies to block autophagic degradation and even subvert it to promote viral propagation. White spot syndrome virus (WSSV) is the most highly pathogenic crustacean virus, but little is currently known about whether crustacean viruses such as WSSV can subvert autophagic degradation for escape. Here, we show that even though WSSV proliferation triggers the accumulation of autophagosomes, autophagic degradation is blocked in the crustacean species red claw crayfish. Interestingly, the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex including CqSNAP29, CqVAMP7, and the novel autophagosome SNARE protein CqSyx12 is required for autophagic flux to restrict WSSV replication, as revealed by gene silencing experiments. Simultaneously, the expressed WSSV tegument protein VP26, which likely localizes on autophagic membrane mediated by its transmembrane region, binds the Qb-SNARE domain of CqSNAP29 to competitively inhibit the binding of CqSyx12-Qa-SNARE with CqSNAP29-Qb-SNARE; this in turn disrupts the assembly of the CqSyx12-SNAP29-VAMP7 SNARE complex, which is indispensable for the proposed fusion of autophagosomes and lysosomes. Consequently, the autophagic degradation of WSSV is likely suppressed by the expressed VP26 protein in vivo in crayfish, thus probably protecting WSSV components from degradation via the autophagosome-lysosome pathway, resulting in evasion by WSSV. Collectively, these findings highlight how a DNA virus can subvert autophagic degradation by impairing the assembly of the SNARE complex to achieve evasion, paving the way for understanding host-DNA virus interactions from an evolutionary point of view, from crustaceans to mammals.IMPORTANCEWhite spot syndrome virus (WSSV) is one of the largest animal DNA viruses in terms of its genome size and has caused huge economic losses in the farming of crustaceans such as shrimp and crayfish. Detailed knowledge of WSSV-host interactions is still lacking, particularly regarding viral escape from host immune clearance. Intriguingly, we found that the presence of WSSV-VP26 might inhibit the autophagic degradation of WSSV in vivo in the crustacean species red claw crayfish. Importantly, this study is the first to show that viral protein VP26 functions as a core factor to benefit WSSV escape by disrupting the assembly of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, which is necessary for the proposed fusion of autophagosomes with lysosomes for subsequent degradation. These findings highlight a novel mechanism of DNA virus evasion by blocking SNARE complex assembly and identify viral VP26 as a key candidate for anti-WSSV targeting.

Molecular structures and function of the autophagosome-lysosome fusion machinery

Macroautophagy (also known as autophagy) plays a pivotal role in maintaining cellular homeostasis. The terminal step of the multi-step autophagy degradation pathway involves fusion between the cargo-laden, double-membraned autophagosome and the lytic organelle lysosome/vacuole. Over the past decade, various core components of the molecular machinery that execute this critical terminal autophagy event have been identified. This review highlights recent advances in understanding the molecular structures, biochemical functions, and regulatory mechanisms of key components of this highly sophisticated machinery including the SNARE fusogens, tethering factors, Rab GTPases and associated guanine nucleotide exchange factors, and other accessory factors.

Ksp1 is an autophagic receptor protein for the Snx4-assisted autophagy of Ssn2/Med13

Ksp1 is a casein II-like kinase whose activity prevents aberrant macroautophagy/autophagy induction in nutrient-rich conditions in yeast. Here, we describe a kinase-independent role of Ksp1 as a novel autophagic receptor protein for Ssn2/Med13, a known cargo of Snx4-assisted autophagy of transcription factors. In this pathway, a subset of conserved transcriptional regulators, Ssn2/Med13, Rim15, and Msn2, are selectively targeted for vacuolar proteolysis following nitrogen starvation, assisted by the sorting nexin heterodimer Snx4-Atg20. Here we show that phagophores also engulf Ksp1 alongside its cargo for vacuolar proteolysis. Ksp1 directly associates with Atg8 following nitrogen starvation at the interface of an Atg8-family interacting motif (AIM)/LC3-interacting region (LIR) in Ksp1 and the LIR/AIM docking site (LDS) in Atg8. Mutating the LDS site prevents the autophagic degradation of Ksp1. However, deletion of the C terminal canonical AIM still permitted Ssn2/Med13 proteolysis, suggesting that additional non-canonical AIMs may mediate the Ksp1-Atg8 interaction. Ksp1 is recruited to the perivacuolar phagophore assembly site by Atg29, a member of the trimeric scaffold complex. This interaction is independent of Atg8 and Snx4, suggesting that Ksp1 is recruited early to phagophores, with Snx4 delivering Ssn2/Med13 thereafter. Finally, normal cell survival following prolonged nitrogen starvation requires Ksp1. Together, these studies define a kinase-independent role for Ksp1 as an autophagic receptor protein mediating Ssn2/Med13 degradation. They also suggest that phagophores built by the trimeric scaffold complex are capable of receptor-mediated autophagy. These results demonstrate the dual functionality of Ksp1, whose kinase activity prevents autophagy while it plays a scaffolding role supporting autophagic degradation.Abbreviations: 3-AT: 3-aminotriazole; 17C: Atg17-Atg31-Atg29 trimeric scaffold complex; AIM: Atg8-family interacting motif; ATG: autophagy related; CKM: CDK8 kinase module; Cvt: cytoplasm-to-vacuole targeting; IDR: intrinsically disordered region; LIR: LC3-interacting region; LDS: LIR/AIM docking site; MoRF: molecular recognition feature; NPC: nuclear pore complex; PAS: phagophore assembly site; PKA: protein kinase A; RBP: RNA-binding protein; UPS: ubiquitin-proteasome system. SAA-TF: Snx4-assisted autophagy of transcription factors; Y2H: yeast two-hybrid.

Driving autophagy - the role of molecular motors

Most of the vesicular transport pathways inside the cell are facilitated by molecular motors that move along cytoskeletal networks. Autophagy is a well-explored catabolic pathway that is initiated by the formation of an isolation membrane known as the phagophore, which expands to form a double-membraned structure that captures its cargo and eventually moves towards the lysosomes for fusion. Molecular motors and cytoskeletal elements have been suggested to participate at different stages of the process as the autophagic vesicles move along cytoskeletal tracks. Dynein and kinesins govern autophagosome trafficking on microtubules through the sequential recruitment of their effector proteins, post-translational modifications and interactions with LC3-interacting regions (LIRs). In contrast, myosins are actin-based motors that participate in various stages of the autophagic flux, as well as in selective autophagy pathways. However, several outstanding questions remain with regard to how the dominance of a particular motor protein over another is controlled, and to the molecular mechanisms that underlie specific disease variants in motor proteins. In this Review, we aim to provide an overview of the role of molecular motors in autophagic flux, as well as highlight their dysregulation in diseases, such as neurodegenerative disorders and pathogenic infections, and ageing.

Autophagy in spinal muscular atrophy: from pathogenic mechanisms to therapeutic approaches

Spinal muscular atrophy (SMA) is a devastating neuromuscular disorder caused by the depletion of the ubiquitously expressed survival motor neuron (SMN) protein. While the genetic cause of SMA has been well documented, the exact mechanism(s) by which SMN depletion results in disease progression remain elusive. A wide body of evidence has highlighted the involvement and dysregulation of autophagy in SMA. Autophagy is a highly conserved lysosomal degradation process which is necessary for cellular homeostasis; defects in the autophagic machinery have been linked with a wide range of neurodegenerative disorders, including amyotrophic lateral sclerosis, Alzheimer's disease and Parkinson's disease. The pathway is particularly known to prevent neurodegeneration and has been suggested to act as a neuroprotective factor, thus presenting an attractive target for novel therapies for SMA patients. In this review, (a) we provide for the first time a comprehensive summary of the perturbations in the autophagic networks that characterize SMA development, (b) highlight the autophagic regulators which may play a key role in SMA pathogenesis and (c) propose decreased autophagic flux as the causative agent underlying the autophagic dysregulation observed in these patients.

A variety of death modes of neutrophils and their role in the etiology of autoimmune diseases

Neutrophils are important in the context of innate immunity and actively contribute to the progression of diverse autoimmune disorders. Distinct death mechanisms of neutrophils may exhibit specific and pivotal roles in autoimmune diseases and disease pathogenesis through the orchestration of immune homeostasis, the facilitation of autoantibody production, the induction of tissue and organ damage, and the incitement of pathological alterations. In recent years, more studies have provided in-depth examination of various neutrophil death modes, revealing nuances that challenge conventional understanding and underscoring their potential clinical utility in diagnosis and treatment. This review explores the multifaceted processes and characteristics of neutrophil death, with a focus on tailored investigations within various autoimmune diseases. It also highlights the potential interplay between neutrophil death and the landscape of autoimmune disorders. The review encapsulates the pertinent pathways implicated in various neutrophil death mechanisms across diverse autoimmune diseases while also charts possible avenues for future research.

New insight of the pathogenesis in osteoarthritis: the intricate interplay of ferroptosis and autophagy mediated by mitophagy/chaperone-mediated autophagy

Ferroptosis, characterized by iron accumulation and lipid peroxidation, is a form of iron-driven cell death. Mitophagy is a type of selective autophagy, where degradation of damaged mitochondria is the key mechanism for maintaining mitochondrial homeostasis. Additionally, Chaperone-mediated autophagy (CMA) is a biological process that transports individual cytoplasmic proteins to lysosomes for degradation through companion molecules such as heat shock proteins. Research has demonstrated the involvement of ferroptosis, mitophagy, and CMA in the pathological progression of Osteoarthritis (OA). Furthermore, research has indicated a significant correlation between alterations in the expression of reactive oxygen species (ROS), adenosine monophosphate (AMP)-activated protein kinase (AMPK), and hypoxia-inducible factors (HIFs) and the occurrence of OA, particularly in relation to ferroptosis and mitophagy. In light of these findings, our study aims to assess the regulatory functions of ferroptosis and mitophagy/CMA in the pathogenesis of OA. Additionally, we propose a mechanism of crosstalk between ferroptosis and mitophagy, while also examining potential pharmacological interventions for targeted therapy in OA. Ultimately, our research endeavors to offer novel insights and directions for the prevention and treatment of OA.

Depletion of β-arrestin-1 in macrophages enhances atherosclerosis in ApoE-/- mice

Autophagy in atherosclerotic plaque macrophage contributes to the alleviation of atherosclerosis through the promotion of lipid metabolism. β-arrestins are multifunctional proteins participating various kinds of cellular signaling pathways. Here we aimed to determine the role of β-arrestin-1, an important member of β-arrestin family, in atherosclerosis, and whether autophagy was involved in this process. ApoE-/-β-arrestin-1fl/flLysM-Cre mice were created through bone marrow transplantation for the atherosclerosis model with conditional myeloid knocking out β-arrestin-1. Bone marrow-derived macrophages (BMDMs) were used for the in vitro studies. Oil red O staining was used to detect the lesional area. F4/80, Masson trichrome and picro-Sirius red staining were applied for the determination of plaque stability. Real-time PCR was used for the detection of levels of lipid metabolism-related receptors. Electron microscopy and tandem fluorescent mRFP-GFP-LC3 plasmid was applied to test autophagy level. We found that β-arrestin-1 was highly increased in expression in plaque macrophage on the occurrence of atherosclerosis. Conditional myeloid knocking out β-arrestin-1 largely promotes plaque formation and vulnerability. In murine macrophage with lipid loading, knocking down β-arrestin-1 enhanced foam cell formation and levels of plasma and cellular cholesterol, while overexpressing β-arrestin-1 led to the opposite effects. The alleviative effects induced by macrophage β-arrestin-1 in atherosclerosis were involved in autophagy, based on the reduction of autophagy level with the knocking down of macrophage β-arrestin-1 and administration of autophagy inhibitors which largely attenuated the decreasing effect on foam cell formation. Our results demonstrated for the first time that macrophage β-arrestin-1 protected against atherosclerosis through the induction of autophagy.

Probing the dynamic crosstalk of lysosomes and mitochondria with structured illumination microscopy

Structured illumination microscopy (SIM) is a super-resolution technology for imaging living cells and has been used for studying the dynamics of lysosomes and mitochondria. Recently, new probes and analyzing methods have been developed for SIM imaging, enabling the quantitative analysis of these subcellular structures and their interactions. This review provides an overview of the working principle and advances of SIM, as well as the organelle-targeting principles and types of fluorescence probes, including small molecules, metal complexes, nanoparticles, and fluorescent proteins. Additionally, quantitative methods based on organelle morphology and distribution are outlined. Finally, the review provides an outlook on the current challenges and future directions for improving the combination of SIM imaging and image analysis to further advance the study of organelles. We hope that this review will be useful for researchers working in the field of organelle research and help to facilitate the development of SIM imaging and analysis techniques.

p62 and NBR1 functions are dispensable for aggrephagy in mouse ESCs and ESC-derived neurons

Accumulation of protein aggregates is a hallmark of various neurodegenerative diseases. Selective autophagy mediates the delivery of specific cytoplasmic cargo material into lysosomes for degradation. In aggrephagy, which is the selective autophagy of protein aggregates, the cargo receptors p62 and NBR1 were shown to play important roles in cargo selection. They bind ubiquitinated cargo material via their ubiquitin-associated domains and tether it to autophagic membranes via their LC3-interacting regions. We used mouse embryonic stem cells (ESCs) in combination with genome editing to obtain further insights into the roles of p62 and NBR1 in aggrephagy. Unexpectedly, our data reveal that both ESCs and ESC-derived neurons do not show strong defects in the clearance of protein aggregates upon knockout of p62 or NBR1 and upon mutation of the p62 ubiquitin-associated domain and the LC3-interacting region motif. Taken together, our results show a robust aggregate clearance in ESCs and ESC-derived neurons. Thus, redundancy between the cargo receptors, other factors, and pathways, such as the ubiquitin-proteasome system, may compensate for the loss of function of p62 and NBR1.

Cytotoxic n-Hexane Fraction of the Egyptian Pteris vittata Functions as Anti-breast Cancer Through Coordinated Actions on Apoptotic and Autophagic Pathways

We investigated the possible anticancer mechanisms of Pteris vittata [PV] n-hexane extract on MCF-7 [breast cancer cell line]. Cultured cell lines were treated with various concentrations of this extract ± Baf-A1 [autophagic inhibitor]. Cells' viability, apoptotic markers [caspase-7, Bax, and Bcl-2], autophagic markers [light chain 3 [LC-3] and P62/SQSTM1]], and the tumor suppressor P53 and its mRNA were checked by their corresponding methods. Treated cell lines showed significant concentration and time-dependent reductions in cell viability in response to PV-n-hexane extract and also exhibited a concomitant induction of apoptosis [increased chromatin condensation, nuclear fragmentation, and pro-apoptotic Bax, and cleaved caspase-7 levels while decreased Bcl-2 levels] and autophagy [increased autophagosomes vacuoles, and LC3B II levels while decreased P62/SQSTM1 levels]. Moreover, PV-n-hexane extract-treated cells showed significant increases in the P53 and its mRNA levels. The addition of Baf-A1 reversed the PV-n-hexane extract autophagic effects and increased apoptotic cell percentage with a much increase in the cleaved caspase-7 and P53 protein and its mRNA levels. We concluded that the PV-n-hexane extract exhibits cytotoxic effects on the MCF-7 cell line with significant reductions in cell viability and concomitant autophagy and apoptosis induction. Inhibition of autophagy in the PV-treated MCF-7 cells enhances apoptosis via a p35-dependent pathway.

Dissecting the Role of Autophagy-Related Proteins in Cancer Metabolism and Plasticity

Modulation of autophagy as an anticancer strategy has been widely studied and evaluated in several cell models. However, little attention has been paid to the metabolic changes that occur in a cancer cell when autophagy is inhibited or induced. In this review, we describe how the expression and regulation of various autophagy-related (ATGs) genes and proteins are associated with cancer progression and cancer plasticity. We present a comprehensive review of how deregulation of ATGs affects cancer cell metabolism, where inhibition of autophagy is mainly reflected in the enhancement of the Warburg effect. The importance of metabolic changes, which largely depend on the cancer type and form part of a cancer cell's escape strategy after autophagy modulation, is emphasized. Consequently, pharmacological strategies based on a dual inhibition of metabolic and autophagy pathways emerged and are reviewed critically here.

CCDC50 promotes tumor growth through regulation of lysosome homeostasis

The maintenance of lysosome homeostasis is crucial for cell growth. Lysosome-dependent degradation and metabolism sustain tumor cell survival. Here, we demonstrate that CCDC50 serves as a lysophagy receptor, promoting tumor progression and invasion by controlling lysosomal integrity and renewal. CCDC50 monitors lysosomal damage, recognizes galectin-3 and K63-linked polyubiquitination on damaged lysosomes, and specifically targets them for autophagy-dependent degradation. CCDC50 deficiency causes the accumulation of ruptured lysosomes, impaired autophagic flux, and superfluous reactive oxygen species, consequently leading to cell death and tumor suppression. CCDC50 expression is associated with malignancy, progression to metastasis, and poor overall survival in human melanoma. Targeting CCDC50 suppresses tumor growth and lung metastasis, and enhances the effect of BRAFV600E inhibition. Thus, we demonstrate critical roles of CCDC50-mediated clearance of damaged lysosomes in supporting tumor growth, hereby identifying a potential therapeutic target of melanoma.

The Golgi stacking protein GRASP55 is targeted by the natural compound prodigiosin

BACKGROUND

The bacterial secondary metabolite prodigiosin has been shown to exert anticancer, antimalarial, antibacterial and immunomodulatory properties. With regard to cancer, it has been reported to affect cancer cells but not non-malignant cells, rendering prodigiosin a promising lead compound for anticancer drug discovery. However, a direct protein target has not yet been experimentally identified.

METHODS

We used mass spectrometry-based thermal proteome profiling in order to identify target proteins of prodigiosin. For target validation, we employed a genetic knockout approach and electron microscopy.

RESULTS

We identified the Golgi stacking protein GRASP55 as target protein of prodigiosin. We show that prodigiosin treatment severely affects Golgi morphology and functionality, and that prodigiosin-dependent cytotoxicity is partially reduced in GRASP55 knockout cells. We also found that prodigiosin treatment results in decreased cathepsin activity and overall blocks autophagic flux, whereas co-localization of the autophagosomal marker LC3 and the lysosomal marker LAMP1 is clearly promoted. Finally, we observed that autophagosomes accumulate at GRASP55-positive structures, pointing towards an involvement of an altered Golgi function in the autophagy-inhibitory effect of this natural compound.

CONCLUSION

Taken together, we propose that prodigiosin affects autophagy and Golgi apparatus integrity in an interlinked mode of action involving the regulation of organelle alkalization and the Golgi stacking protein GRASP55. Video Abstract.

Lipid-hybrid cell-derived biomimetic functional materials: A state-of-the-art multifunctional weapon against tumors

Tumors are among the leading causes of death worldwide. Cell-derived biomimetic functional materials have shown great promise in the treatment of tumors. These materials are derived from cell membranes, extracellular vesicles and bacterial outer membrane vesicles and may evade immune recognition, improve drug targeting and activate antitumor immunity. However, their use is limited owing to their low drug-loading capacity and complex preparation methods. Liposomes are artificial bionic membranes that have high drug-loading capacity and can be prepared and modified easily. Although they can overcome the disadvantages of cell-derived biomimetic functional materials, they lack natural active targeting ability. Lipids can be hybridized with cell membranes, extracellular vesicles or bacterial outer membrane vesicles to form lipid-hybrid cell-derived biomimetic functional materials. These materials negate the disadvantages of both liposomes and cell-derived components and represent a promising delivery platform in the treatment of tumors. This review focuses on the design strategies, applications and mechanisms of action of lipid-hybrid cell-derived biomimetic functional materials and summarizes the prospects of their further development and the challenges associated with it.

TMEM175 downregulation participates in impairment of the autophagy related lysosomal dynamics following neonatal hypoxic-ischemic brain injury

The mechanism underlying long-term cognitive impairment caused by neonatal hypoxic-ischemic brain injury (HIBI) remains unclear. Autophagy is a closely related mechanism and may play a role in this process. We aimed to investigate the role of lysosomal transmembrane protein 175 (TMEM175) in the autophagy-lysosome pathway in neonatal rats with HIBI. A neonatal rat model of HIBI was established, hypoxia was induced, followed by left common carotid artery ligation. Expression levels of TMEM175 and the corresponding proteins involved in autophagy flux and the endolysosomal system fusion process were measured. Rats were administered TMEM175 plasmid via intracerebroventricular injection to induce overexpression. Brain damage and cognitive function were then assessed. TMEM175 was downregulated in the hippocampal tissue, and the autophagy-lysosome pathway was impaired following HIBI in neonatal rats. Overexpression of TMEM175 significantly mitigated neuronal injury and improved long-term cognitive and memory function in neonatal rats with HIBI. We found that improvement in the autophagy-lysosome pathway and endolysosomal system homeostasis, which are TMEM175 related, occurred via regulation of lysosomal membrane dynamic fusion. TMEM175 plays a critical role in maintaining the autophagy-lysosome pathway and endolysosomal homeostasis, contributing to the amelioration of neuronal injury and impaired long-term cognitive function following neonatal HIBI.

Stub1 ameliorates ER stress-induced neural cell apoptosis and promotes locomotor recovery through restoring autophagy flux after spinal cord injury

Endoplasmic reticulum (ER) stress-induced apoptosis and autophagy flux blockade significantly contribute to neuronal pathology of spinal cord injury (SCI). Yet, the molecular interplay between these two distinctive pathways in mediating the pathology of SCI remains largely unexplored. Currently, we aimed at exploring the crucial role of Stub1 in maintaining ER homeostasis and regulating autophagic flux after SCI. Our results demonstrate that Stub1 reduces ER stress induced neuronal apoptosis, promotes axonal regeneration, inhibits glial scar formation and fosters functional recovery by restoring autophagic flux following SCI. Stub1 enhances autophagic flux following SCI by alleviating the permeabilization of lysosomal membrane through activating TFEB. Importantly, we showed that Stub1 promotes the activation of TFEB by targeting HDAC2 for ubiquitination and degradation. Furthermore, the neuroprotective effect of Stub1 on SCI was abrogated by chloroquine administration, underscoring the essential role of Stub1-mediated enhancement of autophagic flux in its protective effects against SCI. Collectively, our data highlights the vital role of Stub1 in regulating ER stress and autophagy flux after SCI, and propose its potential as a promising target for neuroprotective interventions in SCI.

MARCH7-mediated ubiquitination decreases the solubility of ATG14 to inhibit autophagy

Autophagy is a fundamental biological process critical to all eukaryotic cellular life. Although autophagy has been increasingly studied, how its process is precisely coordinated remains an open question. ATG14 (ATG14L/Barkor) is known to play a crucial role in both autophagosome formation and autophagosome-lysosome fusion. However, how ATG14 is regulated, especially at the post-translation level, is still not clear. Here, we report that MARCH7 (membrane-associated ring-CH-type finger 7), an E3 ubiquitin ligase, inhibits autophagy by ubiquitinating ATG14. MARCH7 significantly promotes K6-, K11-, and K63-linked mixed polyubiquitination on ATG14, triggering the aggregation of ATG14 and reducing its solubility in cells. Functionally, we find that MARCH7 depletion decreases the number of aggresome-like induced structures (ALISs). Mechanistically, we show that ubiquitinated ATG14 has fewer interactions with STX17, leading to the inhibition of autophagy flux. Collectively, our study reveals a mechanism in regulating autophagy and suggests a potential strategy for the treatment of autophagy-related diseases.

Chlorpromazine affects autophagy in association with altered Rag GTPase-mTORC1-TFEB signaling

Autophagy is a critical protein and organelle quality control system, which regulates cellular homeostasis and survival. Growing pieces of evidence suggest that autophagic dysfunction is strongly associated with many human diseases, including neurological diseases and cancer. Among various autophagic regulators, microphthalmia (MiT)/TFE transcription factors, including transcription factor EB (TFEB), have been shown to act as the master regulators of autophagosome and lysosome biogenesis in both physiological and pathological conditions. According to the previous studies, chlorpromazine (CPZ), an FDA-approved antipsychotic drug, affects autophagy in diverse cell lines, but the underlying mechanism remains elusive. In our present study, we find that CPZ treatment induces TFEB nuclear translocation through Rag GTPases, the upstream regulators of mechanistic target of rapamycin complex 1 (mTORC1) signaling. Meanwhile, CPZ treatment also blocks autophagosome-lysosome fusion. Notably, we find a significant accumulation of immature autophagosome vesicles in CPZ-treated cells, which may impede cellular homeostasis due to the dysfunction of the autophagy-lysosome pathway. Interestingly and importantly, our data suggest that the expression of the active form of Rag GTPase heterodimers helps in reducing the accumulation of autophagosomes in CPZ-treated cells, further suggesting a major contribution of the Rag GTPase-mTORC1-TFEB signaling axis in CPZ-induced autophagic impairment.

Cyclophilin D as a potential therapeutic target of liver ischemia/reperfusion injury by mediating crosstalk between apoptosis and autophagy

Background

Liver ischemia/reperfusion (I/R) injury is a complex and multifactorial pathophysiological process. It is well recognized that the membrane permeability transition pore (mPTP) opening of mitochondria plays a crucial role in cell death after I/R injury. Cyclophilin D (CypD) is a critical positive regulator of mPTP. However, the effect of CypD on the pathogenesis of liver I/R injury and whether CypD is a potential therapeutic target are still unclear.

Methods

We constructed liver-specific CypD knockout and AAV8-peptidyl prolyl isomerase F (PPIF) overexpression mice. Then, a 70% liver I/R injury model was established in mice, with 90 min of ischemia and 6 h of reperfusion. The liver function was detected by the level of serum glutamic pyruvic transaminase (alanine transaminase) and glutamic oxaloacetic transaminase (aspartate aminotransferase), the liver damage score and degree of necrosis were measured by hematoxylin and eosin (H&E) staining of liver tissues. Reactive oxygen species (ROS) staining, apoptosis, and autophagy-related molecules were used to detect apoptosis and autophagy during liver I/R.

Results

The liver-specific knockout of CypD alleviated necrosis and dysfunction in liver I/R injury, by reducing the excessive production of ROS, and inhibiting cell apoptosis and autophagy. On the contrary, overexpression of CypD exacerbated I/R-induced liver damage.

Conclusion

We found that the downregulation of CypD expression alleviated liver I/R injury by reducing apoptosis and autophagy through caspase-3/Beclin1 crosstalk; in contrast, the upregulation of CypD expression aggravated liver I/R injury. Therefore, interfering with the expression of CypD seems to be a promising treatment for liver I/R injury.

The Beneficial and Adverse Effects of Autophagic Response to Caloric Restriction and Fasting

Each cell is equipped with a conserved housekeeping mechanism, known as autophagy, to recycle exhausted materials and dispose of injured organelles via lysosomal degradation. Autophagy is an early-stage cellular response to stress stimuli in both physiological and pathological situations. It is thought that the promotion of autophagy flux prevents host cells from subsequent injuries by removing damaged organelles and misfolded proteins. As a correlate, the modulation of autophagy is suggested as a therapeutic approach in diverse pathological conditions. Accumulated evidence suggests that intermittent fasting or calorie restriction can lead to the induction of adaptive autophagy and increase longevity of eukaryotic cells. However, prolonged calorie restriction with excessive autophagy response is harmful and can stimulate a type II autophagic cell death. Despite the existence of a close relationship between calorie deprivation and autophagic response in different cell types, the precise molecular mechanisms associated with this phenomenon remain unclear. Here, we aimed to highlight the possible effects of prolonged and short-term calorie restriction on autophagic response and cell homeostasis.

Bidirectional interplay between SARS-CoV-2 and autophagy

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as the causative agent of the recent COVID-19 pandemic, continues representing one of the main health concerns worldwide. Autophagy, in addition to its role in cellular homeostasis and metabolism, plays an important part for the host antiviral immunity. However, viruses including SARS-CoV-2 have evolved diverse mechanisms to not only overcome autophagy's antiviral pressure but also manipulate its machinery in order to enhance viral replication and propagation. Here, we discuss our current knowledge on the impact that autophagy exerts on SARS-CoV-2 replication, as well as the different counteracting measures that this virus has developed to manipulate autophagy's complex machinery. Some of the elements regarding this interplay may become future therapeutic targets in the fight against SARS-CoV-2.

Ubiquitination in the regulation of autophagy

Autophagy, an efficient and effective approach to clear rapidly damaged organelles, macromolecules, and other harmful cellular components, enables the recycling of nutrient materials and supply of nutrients to maintain cellular homeostasis. Ubiquitination plays an important regulatory role in autophagy. This paper summarizes the most recent progress in ubiquitin modification in various stages of autophagy, including initiation, elongation, and termination. Moreover, this paper shows that ubiquitination is an important way through which selective autophagy achieves substrate specificity. Furthermore, we note the distinction between monoubiquitination and polyubiquitination in the regulation of autophagy. Compared with monoubiquitination, polyubiquitination is a more common strategy to regulate the activity of the autophagy molecular machinery. In addition, the role of ubiquitination in the closure and fusion of autophagosomes warrants further study. This article not only clarifies the regulatory mechanism of autophagy but also contributes to a deeper understanding of the importance of ubiquitination modification.

Dipeptidyl-Aminopeptidases 8 and 9 Regulate Autophagy and Tamoxifen Response in Breast Cancer Cells

The cytosolic dipeptidyl-aminopeptidases 8 (DPP8) and 9 (DPP9) belong to the DPPIV serine proteases with the unique characteristic of cleaving off a dipeptide post-proline from the N-termini of substrates. To study the role of DPP8 and DPP9 in breast cancer, MCF-7 cells (luminal A-type breast cancer) and MDA.MB-231 cells (basal-like breast cancer) were used. The inhibition of DPP8/9 by 1G244 increased the number of lysosomes in both cell lines. This phenotype was more pronounced in MCF-7 cells, in which we observed a separation of autophagosomes and lysosomes in the cytosol upon DPP8/9 inhibition. Likewise, the shRNA-mediated knockdown of either DPP8 or DPP9 induced autophagy and increased lysosomes. DPP8/9 inhibition as well as the knockdown of the DPPs reduced the cell survival and proliferation of MCF-7 cells. Additional treatment of MCF-7 cells with tamoxifen, a selective estrogen receptor modulator (SERM) used to treat patients with luminal breast tumors, further decreased survival and proliferation, as well as increased cell death. In summary, both DPP8 and DPP9 activities confine macroautophagy in breast cancer cells. Thus, their inhibition or knockdown reduces cell viability and sensitizes luminal breast cancer cells to tamoxifen treatment.

Chronic inflammation and the hallmarks of aging

BACKGROUND

Recently, the hallmarks of aging were updated to include dysbiosis, disabled macroautophagy, and chronic inflammation. In particular, the low-grade chronic inflammation during aging, without overt infection, is defined as "inflammaging," which is associated with increased morbidity and mortality in the aging population. Emerging evidence suggests a bidirectional and cyclical relationship between chronic inflammation and the development of age-related conditions, such as cardiovascular diseases, neurodegeneration, cancer, and frailty. How the crosstalk between chronic inflammation and other hallmarks of aging underlies biological mechanisms of aging and age-related disease is thus of particular interest to the current geroscience research.

SCOPE OF REVIEW

This review integrates the cellular and molecular mechanisms of age-associated chronic inflammation with the other eleven hallmarks of aging. Extra discussion is dedicated to the hallmark of "altered nutrient sensing," given the scope of Molecular Metabolism. The deregulation of hallmark processes during aging disrupts the delicate balance between pro-inflammatory and anti-inflammatory signaling, leading to a persistent inflammatory state. The resultant chronic inflammation, in turn, further aggravates the dysfunction of each hallmark, thereby driving the progression of aging and age-related diseases.

MAIN CONCLUSIONS

The crosstalk between chronic inflammation and other hallmarks of aging results in a vicious cycle that exacerbates the decline in cellular functions and promotes aging. Understanding this complex interplay will provide new insights into the mechanisms of aging and the development of potential anti-aging interventions. Given their interconnectedness and ability to accentuate the primary elements of aging, drivers of chronic inflammation may be an ideal target with high translational potential to address the pathological conditions associated with aging.

Combined exposure to benzo(a)pyrene and dibutyl phthalate aggravates pro-inflammatory macrophage polarization in spleen via pyroptosis involving cathepsin B

Humans are often simultaneously exposed to benzo(a)pyrene (BaP) and dibutyl phthalate (DBP) through consumption of food and water. Yet, direct evidence of the link between BaP and DBP co-exposure and the risk of splenic injury is lacking. In the present study, we established the rats and primary splenic macrophages models to evaluate the effects of BaP or/and DBP exposure on spleen and underlying mechanisms. Compared to the single exposure or control groups, the co-exposure group showed more severe spleen damage and higher production of pro-inflammatory cytokines. Co-exposure to BaP and DBP resulted in a 1.79-fold, 2.11-fold and 1.9-fold increase in the M1 macrophage markers iNOS, NLRP3 (pyroptosis marker protein) and cathepsin B (CTSB), respectively, and a 0.8-fold decrease in the M2 macrophage marker Arg1 in vivo. The more prominent effects in perturbation of imbalance in M1/M2 polarization (iNOS, 2.25-fold; Arg1, 0.55-fold), pyroptosis (NLRP3, 1.43-fold), and excess CTSB (1.07-fold) in macrophages caused by BaP and DBP co-exposure in vitro were also found. Notably, MCC950 (the NLRP3-specific inhibitor) treatment attenuated the pro-inflammatory macrophage polarization and following pro-inflammatory cytokine production triggered by BaP and DBP co-exposure. Furthermore, CA-074Me (the CTSB-specific inhibitor) suppressed the macrophages pyroptosis, pro-inflammatory macrophage polarization, and secretion of pro-inflammatory cytokine induced by BaP and DBP co-exposure. In conclusion, this study indicates co-exposure to BaP and DBP poses a higher risk of spleen injury. Pro-inflammatory macrophage polarization regulated by pyroptosis involving CTSB underlies the spleen injury caused by BaP and DBP co-exposure.

Mechanisms of metabolic stress induced cell death of human oligodendrocytes: relevance for progressive multiple sclerosis

Oligodendrocyte (OL) injury and loss are central features of evolving lesions in multiple sclerosis. Potential causative mechanisms of OL loss include metabolic stress within the lesion microenvironment. Here we use the injury response of primary human OLs (hOLs) to metabolic stress (reduced glucose/nutrients) in vitro to help define the basis for the in situ features of OLs in cases of MS. Under metabolic stress in vitro, we detected reduction in ATP levels per cell that precede changes in survival. Autophagy was initially activated, although ATP levels were not altered by inhibitors (chloroquine) or activators (Torin-1). Prolonged stress resulted in autophagy failure, documented by non-fusion of autophagosomes and lysosomes. Consistent with our in vitro results, we detected higher expression of LC3, a marker of autophagosomes in OLs, in MS lesions compared to controls. Both in vitro and in situ, we observe a reduction in nuclear size of remaining OLs. Prolonged stress resulted in increased ROS and cleavage of spectrin, a target of Ca²⁺-dependent proteases. Cell death was however not prevented by inhibitors of ferroptosis or MPT-driven necrosis, the regulated cell death (RCD) pathways most likely to be activated by metabolic stress. hOLs have decreased expression of VDAC1, VDAC2, and of genes regulating iron accumulation and cyclophilin. RNA sequencing analyses did not identify activation of these RCD pathways in vitro or in MS cases. We conclude that this distinct response of hOLs, including resistance to RCD, reflects the combined impact of autophagy failure, increased ROS, and calcium influx, resulting in metabolic collapse and degeneration of cellular structural integrity. Defining the basis of OL injury and death provides guidance for development of neuro-protective strategies.

Hereditary spastic paraplegias proteome: common pathways and pathogenetic mechanisms

INTRODUCTION

Hereditary spastic paraplegias (HSPs) are a group of inherited neurodegenerative disorders characterized by progressive spasticity and weakness of the lower limbs. These conditions are caused by lesions in the neuronal pyramidal tract and exhibit clinical and genetic variability. Ongoing research focuses on understanding the underlying mechanisms of HSP onset, which ultimately lead to neuronal degeneration. Key molecular mechanisms involved include axonal transport, cytoskeleton dynamics, myelination abnormalities, membrane trafficking, organelle morphogenesis, ER homeostasis, mitochondrial dysfunction, and autophagy deregulation.

AREAS COVERED

This review aims to provide an overview of the shared pathogenetic mechanisms in various forms of HSPs. By examining disease-causing gene products and their associated functional pathways, this understanding could lead to the discovery of new therapeutic targets and the development of treatments to modify the progression of the disease.

EXPERT OPINION

Investigating gene functionality is crucial for identifying shared pathogenetic pathways underlying different HSP subtypes. Categorizing protein function and identifying pathways aids in finding biomarkers, predicting early onset, and guiding treatment for a better quality of life. Targeting shared mechanisms enables efficient and cost-effective therapies. Prospects involve identifying new disease-causing genes, refining molecular processes, and implementing findings in diagnosis, key for advancing HSP understanding and developing effective treatments.

A perspective on autophagy and transcription factor EB in Alcohol-Associated Alzheimer's disease

Alzheimer's disease (AD) is the most common form of progressive dementia and there is no truly efficacious treatment. Accumulating evidence indicates that impaired autophagic function for removal of damaged mitochondria and protein aggregates such as amyloid and tau protein aggregates may contribute to the pathogenesis of AD. Epidemiologic studies have implicated alcohol abuse in promoting AD, yet the underlying mechanisms are poorly understood. In this review, we discuss mechanisms of selective autophagy for mitochondria and protein aggregates and how these mechanisms are impaired by aging and alcohol consumption. We also discuss potential genetic and pharmacological approaches for targeting autophagy/mitophagy, as well as lysosomal and mitochondrial biogenesis, for the potential prevention and treatment of AD.

Nanoplastics exposure disrupts circadian rhythm associated with dysfunction of the endolysosomal pathway and autophagy in Caenorhabditis elegans

Nanoplastics (NPs), an emerging pollutant, have raised great safety concerns due to their widespread applications and continuous release into the environment, which lead to potential human and environmental risks. Recently, polystyrene NPs (100 nm; 100 mg/L) exposure has been reported to disrupt circadian rhythms under five days temperature entrainment and be associated with stress resistance decline in Caenorhabditis elegans. This study explored the possible relationship between circadian rhythm disruption and endocytosis and autophagy under polystyrene NPs exposure in C. elegans. We show that the disrupted circadian rhythm induced by NPs exposure reduced stress resistance via endocytosis and autophagy impairment. Furthermore, we found that most NPs taken up by intestinal cells were localized to early endosomes, late endosomes, and lysosomes and delivered to autophagosomes. In addition, the disruption of circadian rhythm inhibited NPs localization to these organelles. These findings indicate that NPs exposure disrupts circadian rhythm and alters its subcellular trafficking, leading to enhanced toxicity in C. elegans. Our results shed light on the prominent role of NPs exposure in circadian rhythm disruption associated with endocytosis and autophagy impairments, which may be conserved in higher animals such as humans.

Inhibition of autophagy; an opportunity for the treatment of cancer resistance

The process of macroautophagy plays a pivotal role in the degradation of long-lived, superfluous, and damaged proteins and organelles, which are later recycled for cellular use. Normal cells rely on autophagy to combat various stressors and insults to ensure survival. However, autophagy is often upregulated in cancer cells, promoting a more aggressive phenotype that allows mutated cells to evade death after exposure to therapeutic treatments. As a result, autophagy has emerged as a significant factor in therapeutic resistance across many cancer types, with underlying mechanisms such as DNA damage, cell cycle arrest, and immune evasion. This review provides a comprehensive summary of the role of autophagy in therapeutic resistance and the limitations of available autophagic inhibitors in cancer treatment. It also highlights the urgent need to explore new inhibitors that can synergize with existing therapies to achieve better patient treatment outcomes. Advancing research in this field is crucial for developing more effective treatments that can help improve the lives of cancer patients.

Puerarin Prevents Cadmium-Induced Neuronal Injury by Alleviating Autophagic Dysfunction in Rat Cerebral Cortical Neurons

Autophagic dysfunction is one of the main mechanisms of cadmium (Cd)-induced neurotoxicity. Puerarin (Pue) is a natural antioxidant extracted from the medicinal and edible homologous plant Pueraria lobata. Studies have shown that Pue has neuroprotective effects in a variety of brain injuries, including Cd-induced neuronal injury. However, the role of Pue in the regulation of autophagy to alleviate Cd-induced injury in rat cerebral cortical neurons remains unclear. This study aimed to elucidate the protective mechanism of Pue in alleviating Cd-induced injury in rat cerebral cortical neurons by targeting autophagy. Our results showed that Pue alleviated Cd-induced injury in rat cerebral cortical neurons in vitro and in vivo. Pue activates autophagy and alleviates Cd-induced autophagic blockade in rat cerebral cortical neurons. Further studies have shown that Pue alleviates the Cd-induced inhibition of autophagosome-lysosome fusion, as well as the inhibition of lysosomal degradation. The specific mechanism is related to Pue alleviating the inhibition of Cd on the expression levels of the key proteins Rab7, VPS41, and SNAP29, which regulate autophagosome-lysosome fusion, as well as the lysosome-related proteins LAMP2, CTSB, and CTSD. In summary, these results indicate that Pue alleviates Cd-induced autophagic dysfunction in rat cerebral cortical neurons by alleviating autophagosome-lysosome fusion dysfunction and lysosomal degradation dysfunction, thereby alleviating Cd-induced neuronal injury.

In Response to Precision Medicine: Current Subcellular Targeting Strategies for Cancer Therapy

Emerging as a potent anticancer treatment, subcellular targeted cancer therapy has drawn increasing attention, bringing great opportunities for clinical application. Here, two targeting strategies for four main subcellular organelles (mitochondria, lysosome, endoplasmic reticulum, and nucleus), including molecule- and nanomaterial (inorganic nanoparticles, micelles, organic polymers, and others)-based targeted delivery or therapeutic strategies, are summarized. Phototherapy, chemotherapy, radiotherapy, immunotherapy, and "all-in-one" combination therapy are among the strategies covered in detail. Such materials are constructed based on the specific properties and relevant mechanisms of organelles, enabling the elimination of tumors by inducing dysfunction in the corresponding organelles or destroying specific structures. The challenges faced by organelle-targeting cancer therapies are also summarized. Looking forward, a paradigm for organelle-targeting therapy with enhanced therapeutic efficacy compared to current clinical approaches is envisioned.

Dasatinib in combination with BMS-754807 induce synergistic cytotoxicity in lung cancer cells through inhibiting lung cancer cell growth, and inducing autophagy as well as cell cycle arrest at the G1 phase

Lung cancer is the leading cause of cancer-related deaths worldwide. Combination of drugs targeting independent signaling pathways would effectively block the proliferation of cancer cells with lower concentrations and stronger synergy effects. Dasatinib, a multi-targeted protein tyrosine kinase inhibitor targeting BCR-ABL and kinases of SRC family, has been successfully applied in the treatment of chronic myeloid leukemia (CML). BMS-754807, an inhibitor targeting the insulin-like growth factor 1 receptor (IGF-IR) and insulin receptor (IR) family kinases, has been in phase I development for the treatment of a variety of human cancers. Herein, we demonstrated that dasatinib in combination with BMS-754807 inhibited lung cancer cell growth, while induced autophagy as well as cell cycle arrest at the G1 phase. Dasatinib in combination with BMS-754807 suppressed the expression of cell cycle marker proteins, Rb, p-Rb, CDK4, CDK6 and Cyclin D1, and the PI3K/Akt/mTOR signaling pathway. Dasatinib in combination with BMS-754807 induced autophagy in lung cancer cells, evidenced by the upregulation of LC3B II and beclin-1, the downregulation of LC3B I and SQSTM1/p62, and the autophagic flux observed with a confocal fluorescence microscopy. Furthermore, dasatinib (18 mg/kg) in combination with BMS-754807 (18 mg/kg) inhibited the growth of tumors in NCI-H3255 xenografts without changing the bodyweight. Overall, our results suggest that dasatinib in combination with BMS-754807 inhibits the lung cancer cell proliferation in vitro and tumor growth in vitro, which indicates promising evidence for the application of the drug combination in lung cancer therapy.