Autophagy is suppressed by low temperatures and is dispensable for cold acclimation in Arabidopsis.

Plants have evolved various mechanisms to adapt to the ever-changing external environment. Autophagy is one such mechanism and has been suggested to play a key role in responding to and adapting to abiotic stresses in plants. However, the role of autophagy in adaptation to cold and freezing stresses remains to be characterized in detail. Here, we investigated the role of autophagy in the low-temperature response of Arabidopsis using atg mutants. Both the atg5-1 and atg10-1 mutants exhibited normal freezing tolerance, regardless of cold acclimation. A comparison of fresh weights indicated that the difference in growth between the wild-type and atg plants under cold conditions was rather small compared with that under normal conditions. Analysis of COLD-REGULATED gene expression showed no significant differences between the atg mutants and wild type. Treatment with 3-methyladenine, an inhibitor of autophagy, did not impair the induction of COR15Apro::LUC expression upon exposure to low temperature. Evaluation of autophagic activity using transgenic plants expressing RBCS-mRFP demonstrated that autophagy was rarely induced by cold exposure, even in the dark. Taken together, these data suggest that autophagy is suppressed by low temperatures and is dispensable for cold acclimation and freezing tolerance in Arabidopsis.

Pro-survival signaling regulates lipophagy essential for multiple myeloma resistance to stress-induced death.

Pro-survival metabolic adaptations to stress in tumorigenesis remain less well defined. We find that multiple myeloma (MM) is unexpectedly dependent on beta-oxidation of long-chain fatty acids (FAs) for survival under both basal and stress conditions. However, under stress conditions, a second pro-survival signal is required to sustain FA oxidation (FAO). We previously found that CD28 is expressed on MM cells and transduces a significant pro-survival/chemotherapy resistance signal. We now find that CD28 signaling regulates autophagy/lipophagy that involves activation of the Ca2+→AMPK→ULK1 axis and regulates the translation of ATG5 through HuR, resulting in sustained lipophagy, increased FAO, and enhanced MM survival. Conversely, blocking autophagy/lipophagy sensitizes MM to chemotherapy in vivo. Our findings link a pro-survival signal to FA availability needed to sustain the FAO required for cancer cell survival under stress conditions and identify lipophagy as a therapeutic target to overcome treatment resistance in MM.

Autophagy aggravates multi-walled carbon nanotube-induced ferroptosis by suppressing PGC-1 dependent-mitochondrial biogenesis in lung epithelial cells.

Multi-walled carbon nanotube (MWCNT) induced respiratory toxicity has become a growing concern, with ferroptosis emerging as a novel mechanism implicated in various respiratory diseases. However, whether ferroptosis is involved in MWCNT-elicited lung injury and the underlying molecular mechanisms warrant further exploration. In this study, we found that MWCNT-induced ferroptosis is autophagy-dependent, contributing to its cellular toxicity. Inhibiting of autophagy by pharmacological inhibitors 3-MA or ATG5 gene knockdown significantly attenuated MWCNT-induced ferroptosis, concomitant with rescued mitochondrial biogenesis. Rapamycin, the autophagy agonist, exacerbated the mitochondrial damage and MWCNT-induced ferroptosis. Moreover, lentivirus-mediated overexpression of PGC-1α inhibited ferroptosis, while inhibition of PGC-1α aggravated ferroptosis. In summary, our study unveils ferroptosis as a novel mechanism underlying MWCNT-induced respiratory toxicity, with autophagy promoting MWCNT-induced ferroptosis by hindering PGC-1α-dependent mitochondrial biogenesis.

Increased serum ATG5 as a marker of autophagy in psoriasis vulgaris patients: a cross-sectional study.

Psoriasis (PsO) is a prevalent chronic inflammatory skin disease. It is a complex condition that is affected by environmental and hereditary variables. Numerous pathogens, including viruses, bacteria, and even fungi, have been linked to PsO. One of the mechanisms that clears infections is autophagy. The mechanism by which a cell feeds itself is called autophagy by reusing cytoplasmic components in the lysosome. The autophagy-related (ATG) proteins are essential components of the system that control the strictly regulated process of autophagy. Among these 41 proteins, ATG5 is one that is required in order for autophagic vesicles to develop. This research aimed to compare ATG5 levels in serum among those suffering from psoriasis vulgaris and healthy controls. This cross-sectional research was carried out on 45 individuals with vulgaris psoriasis and 45 healthy, sex and age-matched control subjects. All participants underwent a clinical examination, a laboratory investigation, and a history taking, including lipid profiles and serum ATG5. The mean age of the control and PsO were 40.6 ± 9.6, and 43.7 ± 9.3 years respectively. The mean total PASI score was 13.9 ± 8.9, with a median of 11.7 (8.8). According to the PASI score, about 38% (n = 17) had mild disease (PASI < 10), and about 62% (n = 28) had moderate/severe disease (PASI ≥ 10). There was a significantly higher median (IQR) (25th-75th) ATG5 level in PsO 206 (97) (145-242) ng/ml than in the control 147 (98) (111-209) ng/ml (p = 0.002). An insignificant higher median level (IQR) was observed in PsO with mild disease 207(95) compared with those with moderate/severe disease 183(98.5) (p = 0.057). Dissimilarly, the median (IQR) ATG5 level was significantly lower in PsO individuals with metabolic syndrome 170(72) compared with those without 207(104) (p = 0.044). Four predictors were identified following sex and age adjustments, in the final linear regression model: PASI score, triglyceride, High-Density Lipoprotein, and presence of metabolic syndrome. There can be a connection between autophagy as measured by ATG5 and psoriasis vulgaris. ATG5 was elevated in the serum of individuals with psoriasis vulgaris. However, it decreased in patients with metabolic syndrome. No relation was found between serum ATG5 and PASI score. Psoriasis vulgaris patients may benefit from using an autophagy enhancer as a potential treatment target.

Endonucleosis mediates internalization of cytoplasm into the nucleus.

Setd8 regulates transcription elongation, mitotic DNA condensation, DNA damage response and replication licensing. Here we show that, in mitogen-stimulated liver-specific Setd8-KO mice, most of the hepatocytes are eliminated by necrosis but a significant number of them survive via entering a stage exhibiting several senescence-related features. Setd8-deficient hepatocytes had enlarged nuclei, chromosomal hyperploidy and nuclear engulfments progressing to the formation of intranuclear vesicles surrounded by nuclear lamina. These vesicles contain glycogen, cytoplasmic proteins and even entire organelles. We term this process "endonucleosis". Intranuclear vesicles are absent in hepatocytes of Setd8/Atg5 knockout mice, suggesting that the process requires the function of the canonical autophagy machinery. Endonucleosis and hyperploidization are temporary, early events in the surviving Setd8-deficient cells. Larger vesicles break down into microvesicles over time and are eventually eliminated. The results reveal sequential events in cells with extensive DNA damage, which function as part of survival mechanisms to prevent necrotic death.

Thiram exposure: Disruption of the blood-testis barrier and altered apoptosis-autophagy dynamics in testicular cells via the Bcl-2/Bax and mTOR/Atg5/p62 pathways in mice.

Thiram, a prevalent dithiocarbamate insecticide in agriculture, is widely employed as a crop insecticide and preservative. Chronic exposure to thiram has been linked to various irreversible damages, including tibial cartilage dysplasia, erythrocytotoxicity, renal issues, and immune system compromise. Limited research exists on its effects on reproductive organs. This study investigated the reproductive toxicology in mouse testes exposure to varying concentrations (0, 30, 60, and 120 mg/kg) of thiram. Our study uncovered a series of adverse effects in mice subjected to thiram exposure, including emaciation, stunted growth, decreased water intake, and postponed testicular maturation. Biochemical analysis in thiram-exposed mice showed elevated levels of LDH and AST, while ALP, TG, ALT, and urea were decreased. Histologically, thiram disrupted the testis' microarchitecture and compromised its barrier function by widening the gap between spermatogenic cells and promoting fibrosis. The expression of pro-apoptotic genes (Bax, APAF1, Cytc, and Caspase-3) was downregulated, whereas Bcl-2 expression increased in thiram-treated mice compared to controls. Conversely, the expression of Atg5 was upregulated, and mTOR and p62 expression decreased, with a trend towards lower LC3b levels. Thiram also disrupted the blood-testis barrier, significantly reducing the mRNA expression of zona occludens-1 (ZO-1) and occludin. In conclusion, chronic exposure to high thiram concentrations (120 mg/kg) caused testicular tissue damage, affecting the blood-testis barrier and modulating apoptosis and autophagy through the Bcl-2/Bax and mTOR/Atg5/p62 pathways. This study contributes to understanding the molecular basis of thiram-induced reproductive toxicity and underscores the need for further research and precautions for those chronically exposed to thiram and its environmental residuals.

Metallothionein 3 Potentiates Pulmonary Artery Smooth Muscle Cell Proliferation by Promoting Zinc-MTF1-ATG5 Axis-mediated Autophagosome Formation.

Abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs) is one of the critical pathological mechanisms of pulmonary hypertension (PH), and therefore is gradually being adopted as an important direction for the treatment of PH. Metallothioneins (MTs) have been reported to be associated with PH, but the underlying mechanisms are not fully understood. Here, we demonstrated that the expression level of metallothionein 3 (MT3) was significantly increased in pulmonary arterioles from PH patients and chronic hypoxia-induced rat and mouse PH models, as well as in hypoxia-treated human PASMCs. Knockdown of MT3 significantly inhibited the proliferation of human PASMCs by arresting the cell cycle in the G1 phase, while overexpression of MT3 had the opposite effect. Mechanistically, we found that MT3 increased the intracellular zinc (Zn2+) concentration to enhance the transcriptional activity of metal-regulated transcription factor 1 (MTF1), which promoted the expression of autophagy-related gene 5 (ATG5), facilitating autophagosome formation. More importantly, MT3-induced autophagy and proliferation of human PASMCs were largely prevented by knockdown of MTF1 and ATG5. Therefore, in this study, we identified MT3-Zinc-MTF1-ATG5 as a novel pathway that affects PASMC proliferation by regulating autophagosome formation, suggesting that MT3 may be a novel target for the treatment of PH.

The role of Atg5 gene in tumorigenesis under autophagy deficiency conditions.

Autophagy is a self-recycling machinery to maintain cellular homeostasis by degrading harmful materials in the cell. Autophagy-related gene 5 (Atg5) is required for autophagosome maturation. However, the role of Atg5 in tumorigenesis under autophagy deficient conditions remains unclear. This study focused on the autophagy-independent role of Atg5 and the underlying mechanism in tumorigenesis. We demonstrated that knockout of autophagy-related genes including Atg5, Atg7, Atg9, and p62 in mouse embryonic fibroblast (MEF) cells consistently decreased cell proliferation and motility, implying that autophagy is required to maintain diverse cellular functions. An Atg7 knockout MEF (Atg7-/- MEF) cell line representing deprivation of autophagy function was used to clarify the role of Atg5 transgene in tumorigenesis. We found that Atg5-overexpressed Atg7-/-MEF (clone A) showed increased cell proliferation, colony formation, and migration under autophagy deficient conditions. Accordingly, rescuing the autophagy deficiency of clone A by overexpression of Atg7 gene shifts the role of Atg5 from pro-tumor to anti-tumor status, indicating the dual role of Atg5 in tumorigenesis. Notably, the xenograft mouse model showed that clone A of Atg5-overexpressed Atg7-/- MEF cells induced temporal tumor formation, but could not prolong further tumor growth. Finally, biomechanical analysis disclosed increased Wnt5a secretion and p-JNK expression along with decreased ß-catenin expression. In summary, Atg5 functions as a tumor suppressor to protect the cell under normal conditions. In contrast, Atg5 shifts to a pro-tumor status under autophagy deprivation conditions.

Full-length transcriptome sequencing of Arabidopsis plants provided new insights into the autophagic regulation of photosynthesis.

Autophagy is a highly conserved eukaryotic pathway and plays a crucial role in cell survival under stress conditions. Here, we applied a full-length transcriptome approach to study an Arabidopsis autophagy mutant (atg5-1) subjected to nitrogen-starvation, using Oxford Nanopore Technologies. A total of 39,033 transcripts were identified, including 11,356 new transcripts. In addition, alternative splicing (AS) events and lncRNAs were also detected between Col-0 (WT) and atg5-1. Differentially expressed transcript enrichment showed that autophagy upregulates the expression of many stress-responsive genes and inhibits the transcription of photosynthesis-associated genes. The qRT-PCR results showed that the expression patterns of photosynthesis-related genes in the atg5-1 differed under the conditions of nitrogen starvation and carbon starvation. Under nitrogen starvation treatment, many genes related to photosynthesis also exhibited AS. Chlorophyll fluorescence images revealed that the Fv/Fm and ΦPSII of old atg5-1 leaves were significantly reduced after nitrogen starvation treatment, but the Y(NPQ) indices were significantly increased compared to those of the WT plants. The results of qRT-PCR suggest that autophagy appears to be involved in the degradation of genes related to photodamage repair in PSII. Taken together, the full-length transcriptiome sequencing provide new insights into how new transcripts, lncRNAs and alternative splicing (AS) are involved in plant autophagy through full-length transcriptome sequencing and suggest a new potential link between autophagy and photosynthesis.

Effects of selegiline on neuronal autophagy involving α-synuclein secretion.

Cell-to-cell transmission of α-synuclein (α-syn) pathology underlies the spread of neurodegeneration in Parkinson's disease. α-Syn secretion is an important factor in the transmission of α-syn pathology. However, it is unclear how α-syn secretion is therapeutically modulated. Here, we investigated effects of monoamine oxidase (MAO)-B inhibitor selegiline on α-syn secretion. Treatment with selegiline promoted α-syn secretion in mouse primary cortical neuron cultures, and this increase was kept under glial cell-eliminated condition by Ara-C. Selegiline-induced α-syn secretion was blocked by cytosolic Ca2+ chelator BAPTA-AM in primary neurons. Selegiline-induced α-syn secretion was retained in MAOA siRNA knockdown, whereas it was abrogated by ATG5 knockdown in SH-SY5Y cells. Selegiline increased LC3-II generation with a reduction in intracellular p62/SQSTM1 levels in primary neurons. The increase in LC3-II generation was blocked by co-treatment with BAPTA-AM in primary neurons. Additionally, fractionation experiments showed that selegiline-induced α-syn secretion occurred in non-extracellular vesicle fractions of primary neurons and SH-SY5Y cells. Collectively, these findings show that selegiline promotes neuronal autophagy involving secretion of non-exosomal α-syn via a change of cytosolic Ca2+ levels.

ATG5-mediated keratinocyte ferroptosis promotes M1 polarization of macrophages to aggravate UVB-induced skin inflammation.

Autophagy participates in the regulation of ferroptosis. Among numerous autophagy-related genes (ATGs), ATG5 plays a pivotal role in ferroptosis. However, how ATG5-mediated ferroptosis functions in UVB-induced skin inflammation is still unclear. In this study, we unveil that the core ferroptosis inhibitor GPX4 is significantly decreased in human skin tissue exposed to sunlight. We report that ATG5 deletion in mouse keratinocytes strongly protects against UVB-induced keratinocyte ferroptosis and skin inflammation. Mechanistically, ATG5 promotes the autophagy-dependent degradation of GPX4 in UVB-exposed keratinocytes, which leads to UVB-induced keratinocyte ferroptosis. Furthermore, we find that IFN-γ secreted by ferroptotic keratinocytes facilitates the M1 polarization of macrophages, which results in the exacerbation of UVB-induced skin inflammation. Together, our data indicate that ATG5 exacerbates UVB-induced keratinocyte ferroptosis in the epidermis, which subsequently gives rise to the secretion of IFN-γ and M1 polarization. Our study provides novel evidence that targeting ATG5 may serve as a potential therapeutic strategy for the amelioration of UVB-caused skin damage.

Study on the mechanism of miR-7562 regulating ATG5 and ATG12 genes in Penaeus monodon under Vibrio harveyi infection.

MicroRNAs (miRNAs) play a fundamental role in the post-transcriptional regulation of genes and are pivotal in modulating immune responses in marine species, particularly during pathogen assaults. This study focused on the function of miR-7562 and its regulatory effects on autophagy against Vibrio harveyi infection in the black tiger shrimp (Penaeus monodon), an economically important aquatic species. We successfully cloned and characterized two essential autophagy-related genes (ATGs) from P. monodon, PmATG5 and PmATG12, and then identified the miRNAs potentially involved in co-regulating these genes, which were notably miR-7562, miR-8485, and miR-278. Subsequent bacterial challenge experiments and dual-luciferase reporter assays identified miR-7562 as the principal regulator of both genes, particularly by targeting the 3'UTR of each gene. By manipulating the in vivo levels of miR-7562 using mimics and antagomirs, we found significant differences in the expression of PmATG5 and PmATG12, which corresponded to alterations in autophagic activity. Notably, miR-7562 overexpression resulted in the downregulation of PmATG5 and PmATG12, leading to a subdued autophagic response. Conversely, miR-7562 knockdown elevated the expression levels of these genes, thereby enhancing autophagic activity. Our findings further revealed that during V. harveyi infection, miR-7562 continued to influence the autophagic pathway by specifically targeting the ATG5-ATG12 complex. This research not only sheds light on the miRNA-dependent mechanisms governing autophagic immunity in shrimp but also proposes miR-7562 as a promising target for therapeutic strategies intended to strengthen disease resistance within the crustacean aquaculture industry.

Mild heat shock at 40 °C increases levels of autophagy: Role of Nrf2.

The exposure to low doses of stress induces an adaptive survival response that involves the upregulation of cellular defense systems such as heat shock proteins (Hsps), anti-apoptosis proteins, and antioxidants. Exposure of cells to elevated, non-lethal temperatures (39-41 °C) is an adaptive survival response known as thermotolerance, which protects cells against subsequent lethal stress such as heat shock (>41.5 °C). However, the initiating factors in this adaptive survival response are not understood. This study aims to determine whether autophagy can be activated by heat shock at 40 °C and if this response is mediated by the transcription factor Nrf2. Thermotolerant cells, which were developed during 3 h at 40 °C, were resistant to caspase activation at 42 °C. Autophagy was activated when cells were heated from 5 to 60 min at 40 °C. Levels of acidic vesicular organelles (AVOs) and autophagy proteins Beclin-1, LC3-II/LC3-I, Atg7, Atg5, Atg12-Atg5, and p62 were increased. When Nrf2 was overexpressed or depleted in cells, levels of AVOs and autophagy proteins were higher in unstressed cells, compared to the wild type. Stress induced by mild heat shock at 40 °C further increased levels of most autophagy proteins in cells with overexpression or depletion of Nrf2. Colocalization of p62 and Keap1 occurred. When Nrf2 levels are low, activation of autophagy would likely compensate as a defense mechanism to protect cells against stress. An improved understanding of autophagy in the context of cellular responses to physiological heat shock could be useful for cancer treatment by hyperthermia and the protective role of adaptive responses against environmental stresses.

Immunological synapse formation between T regulatory cells and cancer-associated fibroblasts promotes tumour development.

Cancer-associated fibroblasts (CAFs) have emerged as a dominant non-hematopoietic cell population in the tumour microenvironment, serving diverse functions in tumour progression. However, the mechanisms via which CAFs influence the anti-tumour immunity remain poorly understood. Here, using multiple tumour models and biopsies from cancer patients, we report that α-SMA+ CAFs can form immunological synapses with Foxp3+ regulatory T cells (Tregs) in tumours. Notably, α-SMA+ CAFs can phagocytose and process tumour antigens and exhibit a tolerogenic phenotype which instructs movement arrest, activation and proliferation in Tregs in an antigen-specific manner. Moreover, α-SMA+ CAFs display double-membrane structures resembling autophagosomes in their cytoplasm. Single-cell transcriptomic data showed an enrichment in autophagy and antigen processing/presentation pathways in α-SMA-expressing CAF clusters. Conditional knockout of Atg5 in α-SMA+ CAFs promoted inflammatory re-programming in CAFs, reduced Treg cell infiltration and attenuated tumour development. Overall, our findings reveal an immunosuppressive mechanism entailing the formation of synapses between α-SMA+ CAFs and Tregs in an autophagy-dependent manner.

Combining large-spot low-fluence 1064-nm and fractional 1064-nm picosecond lasers for promoting protective melanosome autophagy via the PI3K/Akt/mTOR signalling pathway for the treatment of melasma.

Melasma is a common condition of hyperpigmented facial skin. Picosecond lasers are reported to be effective for the treatment of melasma. We aimed to identify the most effective therapeutic mode and elucidate the potential molecular mechanisms of picosecond lasers for the treatment of melasma. Female Kunming mice with melasma-like conditions were treated using four different picosecond laser modes. Concurrently, in vitro experiments were conducted to assess changes in melanin and autophagy in mouse melanoma B16-F10 cells treated with these laser modes. Changes in melanin in mouse skin were detected via Fontana-Masson staining, and melanin particles were evaluated in B16-F10 cells. Real-time polymerase chain reaction and western blotting were used to analyse the expression levels of melanosome and autophagy-related messenger ribonucleic acid (mRNA) and proteins. A combination of large-spot low-fluence 1064-nm and fractional 1064-nm picosecond lasers resulted insignificant decreases in melanin as well as in mRNA and protein expression of melanin-synthesizing enzymes (TYR, TRP-1 and MITF). This combination also led to increased expression of the autophagy-related proteins, Beclin1 and ATG5, with a marked decrease in p62 expression. Intervention with the PI3K activator, 740 Y-P, increased TYR, TRP-1, MITF, p-PI3K, p-AKT, p-mTOR and p62 expression but decreased the expression of LC3, ATG5 and Beclin1. A combination of large-spot low-fluence 1064-nm and fractional 1064-nm picosecond lasers proved more effective and safer. It inhibits melanin production, downregulates the PI3K/AKT/mTOR pathway, enhances melanocyte autophagy and accelerates melanin metabolism, thereby reducing melanin content.

Hernandezine promotes cancer cell apoptosis and disrupts the lysosomal acidic environment and cathepsin D maturation.

Hernandezine (Her), a bisbenzylisoquinoline alkaloid extracted from Thalictrum flavum, is recognized for its range of biological activities inherent to this herbal medicine. Despite its notable properties, the anti-cancer effects of Her have remained largely unexplored. In this study, we elucidated that Her significantly induced cytotoxicity in cancer cells through the activation of apoptosis and necroptosis mechanisms. Furthermore, Her triggered autophagosome formation by activating the AMPK and ATG5 conjugation systems, leading to LC3 lipidation. Our findings revealed that Her caused damage to the mitochondrial membrane, with the damaged mitochondria undergoing mitophagy, as evidenced by the elevated expression of mitophagy markers. Conversely, Her disrupted autophagic flux, demonstrated by the upregulation of p62 and accumulation of autolysosomes, as observed in the RFP-GFP-LC3 reporter assay. Initially, we determined that Her did not prevent the fusion of autophagosomes and lysosomes. However, it inhibited the maturation of cathepsin D and increased lysosomal pH, indicating an impairment of lysosomal function. The use of the early-stage autophagy inhibitor, 3-methyladenine (3-MA), did not suppress LC3II, suggesting that Her also induces noncanonical autophagy in autophagosome formation. The application of Bafilomycin A1, an inhibitor of noncanonical autophagy, diminished the recruitment of ATG16L1 and the accumulation of LC3II by Her, thereby augmenting Her-induced cell death. These observations imply that while autophagy initially plays a protective role, the disruption of the autophagic process by Her promotes programmed cell death. This study provides the first evidence of Her's dual role in inducing apoptosis and necroptosis while also initiating and subsequently impairing autophagy to promote apoptotic cell death. These insights contribute to a deeper understanding of the mechanisms underlying programmed cell death, offering potential avenues for enhancing cancer prevention and therapeutic strategies.

Autophagy-related protein 5 (ATG5) interacts with bone marrow stromal cell antigen 2 (BST2) to stimulate HBV replication through antagonizing the antiviral activity of BST2.

Hepatitis B virus (HBV) infection is a major global health burden with 820 000 deaths per year. In our previous study, we found that the knockdown of autophagy-related protein 5 (ATG5) significantly upregulated the interferon-stimulated genes (ISGs) expression to exert the anti-HCV effect. However, the regulation of ATG5 on HBV replication and its underlying mechanism remains unclear. In this study, we screened the altered expression of type I interferon (IFN-I) pathway genes using RT² Profiler™ PCR array following ATG5 knock-down and we found the bone marrow stromal cell antigen 2 (BST2) expression was significantly increased. We then verified the upregulation of BST2 by ATG5 knockdown using RT-qPCR and found that the knockdown of ATG5 activated the Janus kinase/signal transducer and activator of transcription (JAK-STAT) signaling pathway. ATG5 knockdown or BST2 overexpression decreased Hepatitis B core Antigen (HBcAg) protein, HBV DNA levels in cells and supernatants of HepAD38 and HBV-infected NTCP-HepG2. Knockdown of BST2 abrogated the anti-HBV effect of ATG5 knockdown. Furthermore, we found that ATG5 interacted with BST2, and further formed a ternary complex together with HBV-X (HBx). In conclusion, our finding indicates that ATG5 promotes HBV replication through decreasing BST2 expression and interacting with it directly to antagonize its antiviral function.

Neuronal activity promotes secretory autophagy for the extracellular release of α-synuclein.

Extracellular secretion is an essential mechanism for α-synuclein (α-syn) proteostasis. Although it has been reported that neuronal activity affects α-syn secretion, the underlying mechanisms remain unclear. Here, we investigated the autophagic processes that regulate the physiological release of α-syn in mouse primary cortical neurons and SH-SY5Y cells. Stimulating neuronal activity with glutamate or depolarization with high KCl enhanced α-syn secretion. This glutamate-induced α-syn secretion was blocked by a mixture of NMDA receptor antagonist AP5 and AMPA receptor antagonist NBQX, as well as by cytosolic Ca2+ chelator BAPTA-AM. Additionally, mTOR inhibitor rapamycin increased α-syn and p62/SQSTM1 (p62) secretion, and this effect of rapamycin was reduced in primary cortical neurons deficient in the autophagy regulator beclin 1 (derived from BECN1+/- mice). Glutamate-induced α-syn and p62 secretion was suppressed by the knockdown of ATG5, which is required for autophagosome formation. Glutamate increased LC3-II generation and decreased intracellular p62 levels, and the increase in LC3-II levels was blocked by BAPTA-AM. Moreover, glutamate promoted co-localization of α-syn with LC3-positive puncta, but not with LAMP1-positive structures in the neuronal somas. Glutamate-induced α-syn and p62 secretion were also reduced by the knockdown of RAB8A, which is required for autophagosome fusion with the plasma membrane. Collectively, these findings suggest that stimulating neuronal activity mediates autophagic α-syn secretion in a cytosolic Ca2+-dependent manner, and autophagosomes may participate in autophagic secretion by functioning as α-syn carriers.

The Spermine Oxidase/Spermine Axis Coordinates ATG5-Mediated Autophagy to Orchestrate Renal Senescence and Fibrosis.

Decreased plasma spermine levels are associated with kidney dysfunction. However, the role of spermine in kidney disease remains largely unknown. Herein, it is demonstrated that spermine oxidase (SMOX), a key enzyme governing polyamine metabolism, is predominantly induced in tubular epithelium of human and mouse fibrotic kidneys, alongside a reduction in renal spermine content in mice. Moreover, renal SMOX expression is positively correlated with kidney fibrosis and function decline in patients with chronic kidney disease. Importantly, supplementation with exogenous spermine or genetically deficient SMOX markedly improves autophagy, reduces senescence, and attenuates fibrosis in mouse kidneys. Further, downregulation of ATG5, a critical component of autophagy, in tubular epithelial cells enhances SMOX expression and reduces spermine in TGF-ß1-induced fibrogenesis in vitro and kidney fibrosis in vivo. Mechanically, ATG5 readily interacts with SMOX under physiological conditions and in TGF-ß1-induced fibrogenic responses to preserve cellular spermine levels. Collectively, the findings suggest SMOX/spermine axis is a potential novel therapy to antagonize renal fibrosis, possibly by coordinating autophagy and suppressing senescence.

[Silencing GmATG5 genes accelerated senescence and enhanced disease resistance in soybean].

Autophagy plays an essential role in recycling/re-utilizing nutrients and in adaptions to numerous stresses. However, the roles of autophagy in soybean have not been investigated extensively. In this study, a virus-induced gene silencing approach mediated by bean pod mottle virus (BPMV) was used to silence autophagy-related gene 5 (ATG5) genes in soybean (referred to as GmATG5). Our results showed that ATG8 proteins were massively accumulated in the dark-treated leaves of the GmATG5-silenced plants relative to the vector control plants (BPMV-0), indicating that autophagy pathway is impaired in the GmATG5-silenced plants. Consistent with the impaired autophagy, an accelerated senescence phenotype was observed on the leaves of the dark-treated GmATG5-silenced plants, which was not shown on the leaves of the dark-treated BPMV-0 plants. In addition, the accumulation levels of both reactive oxygen species (ROS) and salicylic acid (SA) were significantly induced in the GmATG5-silenced plants compared with that of the vector control plants (BPMV-0), indicating an activated immunity. Accordingly, the GmATG5-silenced plants exhibited significantly enhanced resistance against Pseudomonas syringae pv. glycinea (Psg) in comparison with the BPMV-0 plants. Nevertheless, the activated immunity observed in the GmATG5-silenced plant was independent of the activation of mitogen-activated protein kinase (MAPK).