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Astrovirus-induced epithelial-mesenchymal transition via activated TGF-β increases viral replication.

ABSTRACT: Human astroviruses (HAstV), positive sense single-stranded RNA viruses, are one of the leading causes of diarrhea worldwide. Despite their high prevalence, the cellular mechanisms of astrovirus pathogenesis remain ill-defined. Previous studies showed HAstV increased epithelial barrier permeability by causing a re-localization of the tight junction protein, occludin. In these studies, we demonstrate that HAstV replication induces epithelial-mesenchymal transition (EMT), by upregulating the transcription of EMT-related genes within 8 hours post-infection (hpi), followed by the loss of cell-cell contacts and disruption of polarity by 24 hpi. While multiple classical HAstV serotypes, including clinical isolates, induce EMT, the non-classical genotype HAstV-VA1 and two strains of reovirus are incapable of inducing EMT. Unlike the re-localization of tight junction proteins, HAstV-induced EMT requires productive replication and is dependent transforming growth factor-β (TGF-β) activity. Finally, inhibiting TGF-β signaling and EMT reduces viral replication, highlighting its importance in the viral life cycle. This finding puts classical strains of HAstV-1 in an exclusive group of non-oncogenic viruses triggering EMT.

SUBMITTER: Hargest V

PROVIDER: S-EPMC9067694 | biostudies-literature | 2022 Apr

REPOSITORIES: biostudies-literature

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Astrovirus-induced epithelial-mesenchymal transition via activated TGF-β increases viral replication.

Hargest Virginia V Bub Theresa T Neale Geoffrey G Schultz-Cherry Stacey S

PLoS pathogens 20220422 4

Human astroviruses (HAstV), positive sense single-stranded RNA viruses, are one of the leading causes of diarrhea worldwide. Despite their high prevalence, the cellular mechanisms of astrovirus pathogenesis remain ill-defined. Previous studies showed HAstV increased epithelial barrier permeability by causing a re-localization of the tight junction protein, occludin. In these studies, we demonstrate that HAstV replication induces epithelial-mesenchymal transition (EMT), by upregulating the transc ...[more]

PMID: 35452499

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Project description:Background: Ovarian cancer (OC) is the second most common gynecological malignancy and has a high mortality rate. The current chemotherapeutic drugs have the disadvantages of drug resistance and side effects. Myricetin, a kind of natural compound, has the advantages of easy extraction, low price, and fewer side effects. Multiple studies have demonstrated the anti-cancer properties of myricetin. However, its impact on OC is still unknown and needs further investigation. Therefore, this study aimed to elucidate the mechanism by which myricetin suppresses transforming growth factor-β (TGF-β) -induced epithelial-to-mesenchymal transition (EMT) in OC through in vivo and in vitro experiments. Methods: In vitro experiments were conducted to evaluate the effects of myricetin on cell proliferation and apoptosis using CCK8 assay, plate clonal formation assay, and flow cytometry. Western blot was employed to evaluate the expression levels of caspase-3, PARP, and the MAPK/ERK and PI3K/AKT signaling pathways. Wound healing, transwell, western blot and immunofluorescence assay were used to detect TGF-β-induced cell migration, invasion, EMT and the levels of Smad3, MAPK/ERK, PI3K/AKT signaling pathways. Additionally, a mouse xenograft model was established to verify the effects of myricetin on OC in vivo. Results: Myricetin inhibited OC proliferation through MAPK/ERK and PI3K/AKT signaling pathways. Flow cytometry and western blot analyses demonstrated that myricetin promoted apoptosis by increasing the expression of cleaved-PARP and cleaved-caspase-3 and the ratio of Bax/Bcl-2 in OC. Furthermore, myricetin suppressed the TGF-β-induced migration and invasion by transwell and wound healing assays. Mechanistically, western blot indicated that myricetin reversed TGF-β-induced metastasis through Smad3, MAPK/ERK and PI3K/AKT signaling pathway. In vivo, myricetin significantly repressed OC progression and liver and lung metastasis. Conclusion: Myricetin exhibited inhibitory effects on OC progression and metastasis both in vivo and in vitro. And it also reversed TGF-β-induced EMT through the classical and non-classical Smad signaling pathways.

Project description:A growing body of evidence supports that the epithelial-to-mesenchymal transition (EMT), which occurs during cancer development and progression, has a crucial role in metastasis by enhancing the motility of tumor cells. Transforming growth factor-β (TGF-β) is known to induce EMT in a number of cancer cell types; however, the mechanism underlying this transition process is not fully understood. In this study we have demonstrated that TGF-β upregulates the expression of tumor suppressor protein Par-4 (prostate apoptosis response-4) concomitant with the induction of EMT. Mechanistic investigations revealed that exogenous treatment with each TGF-β isoform upregulates Par-4 mRNA and protein levels in parallel levels of phosphorylated Smad2 and IκB-α increase. Disruption of TGF-β signaling by using ALK5 inhibitor, neutralizing TGF-β antibody or phosphoinositide 3-kinase inhibitor reduces endogenous Par-4 levels, suggesting that both Smad and NF-κB pathways are involved in TGF-β-mediated Par-4 upregulation. NF-κB-binding sites in Par-4 promoter have previously been reported; however, using chromatin immunoprecipitation assay we showed that Par-4 promoter region also contains Smad4-binding site. Furthermore, TGF-β promotes nuclear localization of Par-4. Prolonged TGF-β3 treatment disrupts epithelial cell morphology, promotes cell motility and induces upregulation of Snail, vimentin, zinc-finger E-box binding homeobox 1 and N-Cadherin and downregulation of Claudin-1 and E-Cadherin. Forced expression of Par-4, results in the upregulation of vimentin and Snail expression together with increase in cell migration. In contrast, small interfering RNA-mediated silencing of Par-4 expression results in decrease of vimentin and Snail expression and prevents TGF-β-induced EMT. We have also uncovered a role of X-linked inhibitor of apoptosis protein in the regulation of endogenous Par-4 levels through inhibition of caspase-mediated cleavage. In conclusion, our findings suggest that Par-4 is a novel and essential downstream target of TGF-β signaling and acts as an important factor during TGF-β-induced EMT.

Dataset Information

Astrovirus-induced epithelial-mesenchymal transition via activated TGF-β increases viral replication.

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Astrovirus-induced epithelial-mesenchymal transition via activated TGF-β increases viral replication.

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