Desialylation of Atg5 by sialidase (Neu2) enhances autophagosome formation to induce anchorage-dependent cell death in ovarian cancer cells

H1N1 swine influenza viruses upregulate NEU1 expression through histone H3 acetylation regulated by HDAC2

Mammalian membrane sialic acid is the key receptor for influenza virus. Sialidases, the main type of enzyme that can hydrolyze membrane sialic acids in mammalian cells, have the potential to affect the invasion process of influenza viruses, including H1N1. For the first time, this study focused on the regulation mechanism of sialidase NEU1 expression, and revealed that swine-origin influenza (H1N1) virus infection can promote NEU1 expression through histone H3 acetylation, which is regulated by HDAC2 in host cells. This study not only provides evidence for the regulatory mechanisms of mammalian sialase NEU1 expression, but also provides new insights into the host immune defense response against influenza virus infection.

The resistance to anoikis, mediated by Spp1, and the evasion of immune surveillance facilitate the invasion and metastasis of hepatocellular carcinoma

Anoikis-Related Genes (ARGs) lead to the organism manifesting resistance to anoikis and are associated with unfavorable prognostic outcomes across various malignancies.Therefore, it is crucial to identify the pivotal target genes related to anoikis in HCC .We found that ARGs were significantly correlated with prognosis and immune responses in HCC. The core gene, SPP1, notably promoted anoikis resistance and metastasis in HCC through both in vivo and in vitro studies. The PI3K-Akt-mTOR pathway played a critical role in anoikis suppression within HCC contexts. Our research unveiled SPP1's role in enhancing PKCα phosphorylation, which in turn activated the PI3K-Akt-mTOR cascade. Additionally, SPP1 was identified as a key regulator of MDSCs and Tregs migration, directly affecting their immunosuppressive capabilities.These findings indicate that in HCC, SPP1 promoted anoikis resistance and facilitated immune evasion by modulating MDSCs and Tregs.

Targeting the TRIM14/USP14 Axis Enhances Immunotherapy Efficacy by Inducing Autophagic Degradation of PD-L1

Immunotherapy has greatly improved cancer treatment in recent years by harnessing the immune system to target cancer cells. The first immunotherapeutic agent approved by the FDA was IFNα. Treatment with IFNα can lead to effective immune activation and attenuate tumor immune evasion, but persistent treatment has been shown to elicit immunosuppressive effects. Here, we identified an autophagy-dependent mechanism by which IFNα triggers tumor immune evasion by upregulating PD-L1 to suppress the antitumor activity of CD8+ T cells. Mechanistically, IFNα increased the transcription of TRIM14, which recruited the deubiquitinase USP14 to inhibit the autophagic degradation of PD-L1. USP14 removed K63-linked ubiquitin chains from PD-L1, impairing its recognition by the cargo receptor p62 (also known as SQSTM1) for subsequent autophagic degradation. Combining the USP14 inhibitor IU1 with IFNα and anti-CTLA4 treatment effectively suppressed tumor growth without significant toxicity. This work suggests a strategy for targeting selective autophagy to abolish PD-L1-mediated cancer immune evasion. Significance: IFNα-induced TRIM14 transcription suppresses antitumor immunity by recruiting USP14 to inhibit autophagic degradation of PD-L1, indicating that targeting this axis could be an effective immunotherapeutic approach for treating cancer.

Regulation of sialic acid metabolism in cancer

Sialic acid, the terminal structure of cell surface glycans, has essential functions in regulating immune response, cell-to-cell communication, and cell adhesion. More importantly, an increased level of sialic acid, termed hypersialylation, has emerged as a commonly observed phenotype in cancer. Therefore, targeting sialic acid ligands (sialoglycans) and their receptors (Siglecs) may provide a new therapeutic approach for cancer immunotherapy. We highlight the complexity of the sialic acid metabolism and its involvement in malignant transformation within individual cancer subtypes. In this review, we focus on the dysregulation of sialylation, the intricate nature of sialic acid synthesis, and clinical perspective. We aim to provide a brief insight into the mechanism of hypersialylation and how our understanding of these processes can be leveraged for the development of novel therapeutics.

HDAC1-Mediated Downregulation of NEU1 Exacerbates the Aggressiveness of Cervical Cancer

HDAC1 functions as an oncogene in multi-type cancers. This study aimed to investigate the roles of histone deacetylase 1 (HDAC1) in cervical cancer (CC). mRNA expression was determined using reverse transcription quantitative polymerase chain reaction. The protein-protein complexes was analyzed using co-immunoprecipitation assay. The binding sites between NRF2 and NEU1 were confirmed by chromatin immunoprecipitation assay. Cell viability was detected by CCK-8. Cell proliferation was measured using CCK-8 and colony formation assays. Cell migrative and invasive ability were determined using transwell assay. We found that HDAC1 was upregulated in CC patients and cells. Trichostatin A (TSA) treatment decreased the number of colonies and migrated and invaded cells. Moreover, HDAC1 interacted with NRF2 to downregulate NEU1 expression. NEU1 knockdown attenuated the effects of TSA and enhanced the aggressiveness of CC cells. In conclusion, HDAC1 functions as an oncogene in CC. Targeting HDAC1 may be an alternative strategy for CC.

Lactate promotes myogenesis via activating H3K9 lactylation-dependent up-regulation of Neu2 expression

BACKGROUND

Lactate, a glycolytic metabolite mainly produced in muscles, has been suggested to regulate myoblast differentiation, although the underlying mechanism remains elusive. Recently, lactate-mediated histone lactylation is identified as a novel epigenetic modification that promotes gene transcription.

METHODS

We used mouse C2C12 cell line and 2-month-old male mice as in vitro and in vivo models, respectively. These models were treated with lactate to explore the biological function and latent mechanism of lactate-derived histone lactylation on myogenic differentiation by quantitative real-time PCR, western blotting, immunofluorescence staining, chromatin immunoprecipitation, cleavage under targets and tagmentation assay and RNA sequencing.

RESULTS

Using immunofluorescence staining and western blotting, we proposed that lactylation might occur in the histones. Inhibition of lactate production or intake both impaired myoblast differentiation, accompanied by diminished lactylation in the histones. Using lactylation site-specific antibodies, we demonstrated that lactate preferentially increased H3K9 lactylation (H3K9la) during myoblast differentiation (CT VS 5, 10, 15, 20, 25 mM lactate treatment, P = 0.0012, P = 0.0007, and the rest of all P < 0.0001). Notably, inhibiting H3K9la using P300 antagonist could block lactate-induced myogenesis. Through combined omics analysis using cleavage under targets and tagmentation assay and RNA sequencing, we further identified Neu2 as a potential target gene of H3K9la. IGV software analysis (P = 0.0013) and chromatin immunoprecipitation-qPCR assay (H3K9la %Input, LA group = 9.0076, control group = 2.7184, IgG = 0.3209) confirmed that H3K9la is enriched in the promoter region of Neu2. Moreover, siRNAs or inhibitors against Neu2 both abrogated myoblast differentiation despite lactate treatment, suggesting that Neu2 is required for lactate-mediated myoblast differentiation.

CONCLUSIONS

Our findings provide novel understanding of histone lysine lactylation, suggesting its role in myogenesis, and as potential therapeutic targets for muscle diseases.

Desialylation of ATG5 by sialidase (NEU1) promotes macrophages autophagy and exacerbates inflammation under hypoxia

During the process of atherosclerosis (AS), hypoxia induces plaque macrophage inflammation, promoting lipid accumulation. Autophagy is a cell homeostasis process that increases tolerance to stressors like oxidative stress and hypoxia. However, the specific mechanism by which hypoxia initiates autophagy and the inflammation of macrophages remains to be elucidated. Here, we found that hypoxia-induced macrophage inflammation was mediated by autophagy. Then, the effect of hypoxia on autophagy was investigated in terms of post-translational modifications of proteins. The results showed that desialylation of the autophagy protein ATG5 under hypoxic conditions enhanced protein stability by affecting its charge effect and promoted the formation of the ATG5-ATG12-ATG16L complex, further increasing autophagosome formation. And NEU1, a key enzyme in sialic acid metabolism, was significantly up-regulated under hypoxic conditions and was identified as an interacting protein of ATG5, affecting the sialylation of ATG5. In addition, the knockdown or inhibition of NEU1 reversed hypoxia-induced autophagy and inflammatory responses. In conclusion, our data reveal a key mechanism of autophagy regulation under hypoxia involving ATG5 sialylation and NEU1, suggesting that NEU1 may be a potential target for the prevention and treatment of atherosclerosis.

Sialylation: A Cloak for Tumors to Trick the Immune System in the Microenvironment

The tumor microenvironment (TME), where the tumor cells incite the surrounding normal cells to create an immune suppressive environment, reduces the effectiveness of immune responses during cancer development. Sialylation, a type of glycosylation that occurs on cell surface proteins, lipids, and glycoRNAs, is known to accumulate in tumors and acts as a "cloak" to help tumor cells evade immunological surveillance. In the last few years, the role of sialylation in tumor proliferation and metastasis has become increasingly evident. With the advent of single-cell and spatial sequencing technologies, more research is being conducted to understand the effects of sialylation on immunity regulation. This review provides updated insights into recent research on the function of sialylation in tumor biology and summarizes the latest developments in sialylation-targeted tumor therapeutics, including antibody-mediated and metabolic-based sialylation inhibition, as well as interference with sialic acid-Siglec interaction.

Bidirectional regulation of structural damage on autophagy in the C. elegans epidermis

A variety of disturbances such as starvation, organelle damage, heat stress, hypoxia and pathogen infection can influence the autophagic process. However, how the macroautophagy/autophagy machinery is regulated intrinsically by structural damage of the cell remains largely unknown. In this work, we utilized the C. elegans epidermis as the model to address this question. Our results showed that structural damage by mechanical wounding exerted proximal inhibitory effect and distant promotional effect on autophagy within the same epidermal cell. By disrupting individual mechanical supporting structures, we found that only damage of the basal extracellular matrix or the underlying muscle cells activated a distinct autophagic response in the epidermis. On the contrary, structural disruption of the epidermal cells at the apical side inhibited autophagy activation caused by different stress factors. Mechanistic studies showed that the basal promotional effect of structural damage on epidermal autophagy was mediated by a mechanotransduction pathway going through the basal hemidesmosome receptor and LET-363/MTOR, while the apical inhibitory effect was mostly carried out by activation of calcium signaling. Elevated autophagy in the epidermis played a detrimental rather than a beneficial role on cell survival against structural damage. The results obtained from these studies will not only help us better understand the pathogenesis of structural damage- and autophagy-related diseases, but also provide insight into more generic rules of autophagy regulation by the structural and mechanical properties of cells across species.Abbreviations : ATG: autophagy related; BLI-1: BLIstered cuticle 1; CeHDs: C. elegans hemidesmosomes; COL-19: COLlagen 19; DPY-7: DumPY 7; ECM: extracellular matrix; EPG-5: ectopic PGL granules 5; GFP: green fluorescent protein; GIT-1: GIT1 (mammalian G protein-coupled receptor kinase InTeractor 1) homolog; GTL-2: Gon-Two Like 2 (TRP subfamily); HIS-58, HIStone 58; IFB-1: Intermediate Filament, B 1; LET: LEThal; LGG-1: LC3, GABARAP and GATE-16 family 1; MTOR: mechanistic target of rapamycin; MTORC1: MTOR complex 1; MUP-4: MUscle Positioning 4; NLP-29: Neuropeptide-Like Protein 29; PAT: Paralyzed Arrest at Two-fold; PIX-1: PIX (PAK (p21-activated kinase) Interacting eXchange factor) homolog 1; RFP: red fluorescent protein; RNAi: RNA interference; SQST-1: SeQueSTosome related 1; UNC: UNCoordinated; UV: ultraviolet; VAB-10: variable ABnormal morphology 10; WT: wild type.

Sialidase Inhibitors with Different Mechanisms

Sialidases, or neuraminidases, are enzymes that catalyze the hydrolysis of sialic acid (Sia)-containing molecules, mostly removal of the terminal Sia (desialylation). By desialylation, sialidase can modulate the functionality of the target compound and is thus often involved in biological pathways. Inhibition of sialidases with inhibitors is an important approach for understanding sialidase function and the underlying mechanisms and could serve as a therapeutic approach as well. Transition-state analogues, such as anti-influenza drugs oseltamivir and zanamivir, are major sialidase inhibitors. In addition, difluoro-sialic acids were developed as mechanism-based sialidase inhibitors. Further, fluorinated quinone methide-based suicide substrates were reported. Sialidase product analogue inhibitors were also explored. Finally, natural products have shown competitive inhibiton against viral, bacterial, and human sialidases. This Perspective describes sialidase inhibitors with different mechanisms and their activities and future potential, which include transition-state analogue inhibitors, mechanism-based inhibitors, suicide substrate inhibitors, product analogue inhibitors, and natural product inhibitors.

Non-apoptotic cell death in ovarian cancer: Treatment, resistance and prognosis

Ovarian cancer is mostly diagnosed at an advanced stage due to the absence of effective screening methods and specific symptoms. Repeated chemotherapy resistance and recurrence before PARPi are used as maintenance therapies, lead to low survival rates and poor prognosis. Apoptotic cell death plays a crucial role in ovarian cancer, which is proved by current researches. With the ongoing development of targeted therapy, non-apoptotic cell death has shown substantial potential in tumor prevention and treatment, including autophagy, ferroptosis, necroptosis, immunogenic cell death, pyroptosis, alkaliptosis, and other modes of cell death. We systematically reviewed the research progress on the role of non-apoptotic cell death in the onset, development, and outcome of ovarian cancer. This review provides a more theoretical basis for exploring therapeutic targets, reversing drug resistance in refractory ovarian cancer, and establishing risk prediction models that help realize the clinical transformation of vital drugs.

M6A-mediated upregulation of circMDK promotes tumorigenesis and acts as a nanotherapeutic target in hepatocellular carcinoma

Background

Emerging evidence suggest the critical role of circular RNAs (circRNAs) in disease development especially in various cancers. However, the oncogenic role of circRNAs in hepatocellular carcinoma (HCC) is still largely unknown.

Methods

RNA sequencing was performed to identify significantly upregulated circRNAs in paired HCC tissues and non-tumor tissues. CCK-8 assay, colony formation, transwell, and xenograft mouse models were used to investigate the role of circRNAs in HCC proliferation and metastasis. Small interfering RNA (siRNA) was used to silence gene expression. RNA immunoprecipitation, biotin pull-down, RNA pull-down, luciferase reporter assay and western blot were used to explore the underlying molecular mechanisms.

Results

Hsa_circ_0095868, derived from exon 5 of the MDK gene (named circMDK), was identified as a new oncogenic circRNA that was significantly upregulated in HCC. The upregulation of circMDK was associated with the modification of N6-methyladenosine (m⁶A) and poor survival in HCC patients. Mechanistically, circMDK sponged miR-346 and miR-874-3p to upregulate ATG16L1 (Autophagy Related 16 Like 1), resulting to the activation of PI3K/AKT/mTOR signaling pathway to promote cell proliferation, migration and invasion. Poly (β-amino esters) (PAEs) were synthesized to assist the delivery of circMDK siRNA (PAE-siRNA), which effectively inhibited tumor progression without obvious adverse effects in four liver tumor models including subcutaneous, metastatic, orthotopic and patient-derived xenograft (PDX) models.

Conclusions

CircMDK could serve as a potential tumor biomarker that promotes the progression of HCC via the miR-346/874-3p-ATG16L1 axis. The PAE-based delivery of siRNA improved the stability and efficiency of siRNA targeting circMDK. The PAE-siRNA nanoparticles effectively inhibited HCC proliferation and metastasis in vivo. Our current findings offer a promising nanotherapeutic strategy for the treatment of HCC.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01575-z.

TFEB-lysosome pathway activation is associated with different cell death responses to carbon quantum dots in Kupffer cells and hepatocytes

Background

Carbon dot has been widely used in biomedical field as a kind of nanomaterial with low toxicity and high biocompatibility. CDs has demonstrated its unique advantages in assisted drug delivery, target diagnosis and targeted therapy with its small size and spontaneous fluorescence. However, the potential biosafety of CDs cannot be evaluated. Therefore, we focused on the study of liver, the target organ involved in CDs metabolism, to evaluate the risk of CDs in vitro.

Methods and results

Liver macrophage KUP5 cells and normal liver cells AML12 cells were incubated in CDs at the same concentration for 24 h to compare the different effects under the same exposure conditions. The study found that both liver cell models showed ATP metabolism disorder, membrane damage, autophagosome formation and lysosome damage, but the difference was that, KUP5 cells exhibited more serious damage than AML12 cells, suggesting that immunogenic cell type is particularly sensitive to CDs. The underlying mechanism of CDs-induced death of the two hepatocyte types were also assessed. In KUP5 cells, death was caused by inhibition of autophagic flux caused by autophagosome accumulation, this process that was reversed when autophagosome accumulation was prevented by 3-MA. AML12 cells had no such response, suggesting that the accumulation of autophagosomes caused by CDs may be specific to macrophages.

Conclusion

Activation of the TFEB-lysosome pathway is important in regulating autophagy and apoptosis. The dual regulation of ERK and mTOR phosphorylation upstream of TFEB influences the death outcome of AML12 cells. These findings provide a new understanding of how CDs impact different liver cells and contribute to a more complete toxicological safety evaluation of CDs.

Mammalian Neuraminidases in Immune-Mediated Diseases: Mucins and Beyond

Mammalian neuraminidases (NEUs), also known as sialidases, are enzymes that cleave off the terminal neuraminic, or sialic, acid resides from the carbohydrate moieties of glycolipids and glycoproteins. A rapidly growing body of literature indicates that in addition to their metabolic functions, NEUs also regulate the activity of their glycoprotein targets. The simple post-translational modification of NEU protein targets-removal of the highly electronegative sialic acid-affects protein folding, alters protein interactions with their ligands, and exposes or covers proteolytic sites. Through such effects, NEUs regulate the downstream processes in which their glycoprotein targets participate. A major target of desialylation by NEUs are mucins (MUCs), and such post-translational modification contributes to regulation of disease processes. In this review, we focus on the regulatory roles of NEU-modified MUCs as coordinators of disease pathogenesis in fibrotic, inflammatory, infectious, and autoimmune diseases. Special attention is placed on the most abundant and best studied NEU1, and its recently discovered important target, mucin-1 (MUC1). The role of the NEU1 - MUC1 axis in disease pathogenesis is discussed, along with regulatory contributions from other MUCs and other pathophysiologically important NEU targets.

Identification of GNA12-driven gene signatures and key signaling networks in ovarian cancer

With the focus on defining the oncogenic network stimulated by lysophosphatidic acid (LPA) in ovarian cancer, the present study sought to interrogate the oncotranscriptome regulated by the LPA-mediated signaling pathway. LPA, LPA-receptor (LPAR) and LPAR-activated G protein 12 α-subunit, encoded by G protein subunit α 12 (GNA12), all serve an important role in ovarian cancer progression. While the general signaling mechanism regulated by LPA/LPAR/GNA12 has previously been characterized, the global transcriptomic network regulated by GNA12 in ovarian cancer pathophysiology remains largely unknown. To define the LPA/LPAR/GNA12-orchestrated oncogenic networks in ovarian cancer, transcriptomic and bioinformatical analyses were conducted using SKOV3 cells, in which the expression of GNA12 was silenced. Array analysis was performed in Agilent SurePrint G3 Human Comparative Genomic Hybridization 8×60 microarray platform. The array results were validated using Kuramochi cells. Gene and functional enrichment analyses were performed using Database for Annotation, Visualization and Integrated Discovery, Search Tool for Retrieval of Interacting Genes and Cytoscape algorithms. The results indicated a paradigm in which GNA12 drove ovarian cancer progression by upregulating a pro-tumorigenic network with AKT1, VEGFA, TGFB1, BCL2L1, STAT3, insulin-like growth factor 1 and growth hormone releasing hormone as critical hub and/or bottleneck nodes. Moreover, GNA12 downregulated a growth-suppressive network involving proteasome 20S subunit (PSM) β6, PSM α6, PSM ATPase 5, ubiquitin conjugating enzyme E2 E1, PSM non-ATPase 10, NDUFA4 mitochondrial complex-associated, NADH:ubiquinone oxidoreductase subunit B8 and anaphase promoting complex subunit 1 as hub or bottleneck nodes. In addition to providing novel insights into the LPA/LPAR/GNA12-regulated oncogenic networks in ovarian cancer, the present study identified several potential nodes in this network that could be assessed for targeted therapy.