Autophagy reports最新文献

Autophagy is an evolutionarily conserved cellular process that is prominent during bacterial infections. In this review article, we discuss how direct pathogen clearance via xenophagy and regulation of inflammatory products represent dual functions of autophagy that coordinate an effective antimicrobial response. We detail the molecular mechanisms of xenophagy, including signals that indicate the presence of an intracellular pathogen and autophagy receptor-mediated cargo targeting, while highlighting pathogen counterstrategies, such as bacterial effector proteins that inhibit autophagy initiation or exploit autophagic membranes for replication. Pathways that are related to autophagy, including LC3-associated phagocytosis (LAP) and conjugation of ATG8 to single membranes (CASM), are expanding the role of autophagy in antimicrobial defense beyond traditional double-membrane autophagosomes. Examination of Crohn disease-associated genes links impaired autophagy to inflammation and defective bacterial handling. We propose emerging concepts, such as effector-triggered immunity, where autophagy inhibition by pathogens triggers inflammatory defenses and discusses the therapeutic potential of modulating autophagy in infectious and inflammatory diseases.

Psoriasis is a chronic inflammatory skin disease characterized by abnormal differentiation and hyperproliferation of epidermal keratinocytes. Autophagy plays a critical role in regulating the functions of immune cells, endothelial cells, and especially keratinocytes, contributing to the pathogenesis of psoriasis. However, the role of chaperone-mediated autophagy (CMA) in psoriatic keratinocytes has not been fully explored. Our study, for the first time, revealed that defective CMA is present in imiquimod (IMQ)-induced psoriasiform lesions. Importantly, activation of CMA significantly attenuated IMQ-induced phenotypes both in vitro and in vivo, including reduced skin lesion severity, decreased keratinocyte proliferation and differentiation, and lower cytokine secretion. Mechanistically, toll-like receptor 7 (TLR7), containing a specific KFERQ-like motif, is a substrate for CMA-mediated degradation. This process modulates IMQ-TLR7 signal activation in keratinocytes. CMA deficiency in psoriasis leads to increased TLR7 levels, which, in turn, enhances TLR7-NF-κB signaling pathway activation, ultimately contributing to dysregulated keratinocyte proliferation, differentiation, and cytokine secretion. This study provides novel evidence that defective CMA is present in IMQ-induced psoriasiform lesions and that CMA activation can attenuate IMQ-induced phenotypes by modulating TLR7 signaling in keratinocytes. These findings highlight the potential of CMA as a therapeutic target for psoriasis.

Protein mislocalization and aggregation are hallmark features in neurodegeneration. As proteins mislocalize, proteostasis deficiency and protein aggregation typically follow. Autophagy is a crucial pathway for the removal of protein aggregates to maintain neuronal health, but is impaired in various neurodegenerative diseases, including Huntington disease (HD). We identified S-acylation, a reversible lipid modification of proteins, as an important regulator in protein trafficking and autophagy. SQSTM1 (sequestosome 1/p62) is an essential selective autophagy receptor for the sequestration of ubiquitinated cargoes within autophagosomes and subsequent delivery into lysosomes for degradation. Recently, we reported that S-acylation of SQSTM1 at the di-cysteine motif C289,290 directs SQSTM1 to lysosomes. We further showed that SQSTM1 S-acylation is significantly reduced in brains from both HD patients and mouse HD model, which may result in the cargo sequestration defect within autophagosomes in HD. Treatment with palmostatin B, a deacylation inhibitor, significantly increases SQSTM1 localization to lysosomes. Our work highlights SQSTM1 S-acylation as a novel potential therapeutic strategy in HD. As a crucial autophagy component, our work suggests S-acylation of SQSTM1 may have a broader role in neurodegeneration.

During chronic infections, biofilms are resistant to both antimicrobial agents as well as the host immune system, often giving rise to recalcitrant persister cells with reduced mitochondrial function rendering biofilm infections difficult to cure. How mitochondrial dynamics and fate are regulated during fungal biofilm formation is poorly understood. In this study, we used live cell microscopy to track mitochondrial morphology during Aspergillus nidulans in vitro biofilm formation. We show that mitochondria undergo fragmentation during early biofilm development, and that externally induced oxidative stress similarly induces mitochondrial fragmentation, indicating a role for redox regulation in this process. Deletion of core components of the mitochondrial fission machinery resulted in a swollen mitochondrial phenotype. Mitochondria in the fission-mutant strains are known not to complete fragmentation in response to externally induced oxidative stress, and we show that this results in a "beads on a string" phenotype. We further show that mitochondria remain unfragmented during biofilm formation in the fission-mutant strains, although other biofilm cellular modifications, like disassembly of microtubules, are unaffected. We report that mitophagy is triggered during biofilm development in nitrogen-limiting conditions independently of mitochondrial fission. This indicates mitochondrial fission is dispensable for mitophagy during biofilm development with limiting nitrogen. We further note that general autophagy, but notably not mitophagy, is triggered during biofilm development in carbon-limiting conditions, demonstrating differential regulation of mitochondrial fate in response to specific nutritional limitations during fungal biofilm formation.

Macroautophagy (referred to here as autophagy) is thought to play a critical role in aging and age-related disease, making it a priority for development of targeted human therapies. We developed a flow cytometry-based method to measure autophagic flux in 19 subpopulations from whole blood, using chloroquine (CQ) to inhibit lysosomal degradation, and the autophagy protein MAP1LC3B (microtubule associated protein 1 light chain 3 beta) isoform II/LC3B-II to measure autophagic flux (the acquisition and degradation of autophagic cargo over time). Autophagic flux varies by cell type and is higher in whole blood compared with RPMI culture media. Basal autophagic flux shows sex- and age-specific variations. Further, monocytes, but not T cells, respond robustly to amino acid starvation by increasing autophagy, with older individuals exhibiting stronger responses, particularly in non-classical monocytes. These findings underscore the importance of cell type-specific autophagy measurements to understand the effects of aging, sex and nutrition, to develop targeted interventions for age-related diseases.

Targeting autophagy is believed to hold great promise for the treatment of various diseases, including cancer. However, since the therapeutic efficacy of currently available autophagy-modulating drugs is limited by off-target effects and the requirement of high dosage, there is an urgent need to develop novel autophagy-targeting compounds. In this study, we report molecules of the biarylacetamide class as novel autophagy inhibitors. These molecules were identified via phenotypic high-throughput screening, and a series of analogues was subsequently synthesized. Among these, 5d and 5j were retained as potent autophagy blockers in HeLa and LNCaP cells. Both compounds inhibited autophagy at a late-stage in the pathway, as evidenced by the strong accumulation of RFP-GFP-LC3 puncta as well as LC3-II, GABARAP-II and SQSTM1 protein levels, resembling the effects obtained with the well-known late-stage autophagy inhibitor Bafilomycin A1. Quantitative proteome profiling combined with metabolomic and lipidomic studies revealed that 5j significantly altered lipid metabolism. These alterations included activation of the cholesterol biosynthesis pathway and changes in the distribution of key lipid classes, such as phospholipids, ceramides and triglycerides. Further mechanistic studies indicated that 5d and 5j triggered an ER stress response and may impair lysosomal function, as suggested by the accumulation of pro-cathepsin D. Collectively, these findings demonstrate that 5j is a novel and potent late-stage autophagy inhibitor with a distinct mechanism of action compared to currently available inhibitors.

Autophagy is a crucial cellular process responsible for the degradation and recycling of damaged or unnecessary components, maintaining cellular homeostasis and protecting against stress. Dysregulation of autophagy has been implicated in a variety of neurodegenerative diseases, including multiple sclerosis, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease. Various types of autophagy exist, each with distinct mechanisms, such as macroautophagy, mitophagy, lipophagy, and chaperone-mediated autophagy. These processes are essential for the removal of toxic substrates like protein aggregates and dysfunctional mitochondria, which are vital for neuronal health. In neurodegenerative diseases, the impairment of these clearance mechanisms leads to the accumulation of harmful substances, which accelerate disease progression. Modulating autophagy has emerged as a promising therapeutic strategy, with ongoing studies investigating molecules that can either stimulate or regulate this process. However, despite its potential, significant challenges remain in translating preclinical findings into clinically effective treatments. In this review, we will explore the different types of autophagy, their roles in neurodegenerative diseases, and the therapeutic potential associated with modulating these processes.

Huntington's disease (HD) is caused by the expansion of poly-glutamine repeats in the Huntingtin (Htt) gene and is associated with a wide variety of motor and physiological (sleep, metabolism, etc.) perturbations. Studies from diverse model organisms have proposed that modulation of autophagy (a key protein homeostatic pathway) can mitigate the toxic effects of mutant HTT protein. However, consistent changes are not observed across studies, and the improvements in phenotypes can be associated with changes in specific circuits/neurons affected by the mutant HTT protein. They suggest that not all neurons respond effectively to autophagy modulation. Hence, it remains to be understood whether diverse circuits/neurons affected by mutant HTT protein respond effectively to this intervention. Using a genetic approach, we expressed mutant HTT protein independently in diverse sets of neurons in male Drosophila melanogaster and asked whether genetic modulation of autophagy pathway through Atg8a overexpression can mitigate the toxic effect of mutant HTT protein. We found that in male flies, not all neurons/circuits expressing mutant HTT protein respond effectively to ATG8a protein. Circadian neurons and neurons regulating carbohydrate and lipid metabolism (Dilp2 ^+ve) showed improvement, while motor and neurons responding to temperature changes showed no improvement. Using cellular markers we also showed that these phenotypes can be attributed to specific changes in mutant HTT and Ref(2)P proteins (autophagy marker). Our study suggests that not all circuits respond effectively to autophagy modulation and suggests a potential cause for low success of autophagy modulators in clinical trials..

The prenylated Rab acceptor protein 1 (PRA1) domain is a conserved domain encompassing four transmembrane domains (TMDs). ARL6IP5 (ADP ribosylation factor-like GTPase 6-interacting protein 5) is a member of the PRA1 family and interacts with the reticulon-homology domain (RHD)-containing proteins including ARL6IP1 (ADP ribosylation factor-like GTPase 6-interacting protein 1) and FAM134B. The RHD is a conserved domain encompassing two short hairpin TMDs and acts as a membrane-shaping unit for endoplasmic reticulum (ER) morphology and ER-phagy. However, the involvement of ARL6IP5 in ER morphology and ER-phagy remains unclear. We recently characterized ARL6IP5 as an ER membrane-shaping protein and found that ARL6IP5 constricts the ER membrane in a manner similar to ARL6IP1, possibly via short hairpin configuration of the TMDs in the PRA1 domain. ARL6IP5 also plays a redundant role with ARL6IP1 in shaping the ER membrane. Importantly, depletion of ARL6IP5 impaired FAM134B-meadited ER-phagy, which is reminiscent of ARL6IP1 depletion. These results suggested that ARL6IP5 acts as an ER membrane-shaping protein that regulates ER-phagy, underscoring the importance of the PRA1 domain. Although ARL6IP5 and ARL6IP1 are confusable protein names and seem to have similar roles in ER-phagy, we clarify in this punctum that they are distinct classes of ER membrane-shaping proteins.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of Coronavirus disease 19 (COVID-19), continues to circulate globally despite the widespread vaccination and therapeutics like Paxlovid, remdesivir, and molnupiravir. COVID-19 is associated with both respiratory and gastrointestinal manifestations, with persistent intestinal pathology contributing to the post-COVID-19 condition. We have previously demonstrated the antiviral activity of autophagy-blocking drugs, such as Berbamine dihydrochloride, against intestinal SARS-CoV-2 acquisition. In addition, the autophagy blockers restored the barrier function of infected intestinal epithelium. In this addendum, using human intestinal organoids, we present evidence for a protective role of intrinsic higher levels of autophagy flux in limiting intestinal SARS-CoV-2 infection. Pharmacological treatment with Akt inhibitor MK-2206 hydrochloride suppressed viral entry into the intestinal epithelium. This antiviral effect of MK-2206 was shown to be dependent on Synaptosomal-associated protein 29-dependent (SNAP-29)-mediated autophagy flux. Furthermore, extrinsically enhanced autophagy with MK-2206 also prevented SARS-CoV-2-induced intestinal barrier damage. Our findings thus underscore the intricate role of autophagy pathways in the dissemination and pathogenesis of intestinal SARS-CoV-2, highlighting the therapeutic potential of host-directed therapies targeting autophagy to intervene in COVID-19-associated sequelae and improve intestinal health.