Cloning and functional analysis of autophagy-related gene 7 in Bombyx mori, silkworm

Silkworm (Bombyx mori) is an important economic insect and an attractive model system. A series of autophagy-related genes (Atgs) are involved in the autophagic process, and these Atgs have been proved to play important roles in the development. Atg7 stands at the hub of two ubiquitin-like systems involving Atg8 and Atg12 in the autophagic vesicle. In the present study, we cloned and characterized a BmAtg7 gene in Bombyx mori. The open reading frame (ORF) of BmAtg7 was 1908 bp in length, and it encoded a polypeptide of 635 amino acids. BmAtg7 was highly expressed in the posterior silk gland, fatbody, and epidermis. The expression profile of BmAtg7 in the fatbody showed an increasing tendency from day 1 of the 5th instar to the prepupal stage. After chlorantraniliprole (CAP) exposure, the transcriptional level of BmAtg7 was continuously decreased. After depletion of BmAtg7 by RNAi, the expressions of BmAtg7, BmAtg8, and BmEcr were all downregulated, while the expression of BmJHBP2 was upregulated. However, depletion of BmAtg7 did not prevent the metamorphosis of silkworm from larvae to pupae, while the occurrence of such process was delayed. After the 20-hydroxyecdysone (20E) treatment, the expression characteristics of these four genes (BmAtg7, BmAtg8, BmEcr and BmJHBP2) were contrary to the results after depletion of BmAtg7. Our results suggested that although CAP exposure could significantly inhibit the expression of BmAtg7 continuously, the changes of BmAtg7 was not the key factor in CAP-induced metamorphosis defects.

Long Non-coding RNA FENDRR Modulates Autophagy Through Epigenetic Suppression of ATG7 via Binding PRC2 in Acute Pancreatitis

Acute pancreatitis (AP) is an inflammatory, complicated pancreatic disease, carrying significant morbidity and mortality. However, the molecular and cellular mechanisms involved in AP pathogenesis remain to be elucidated. Here, we explore the role of FOXF1 adjacent non-coding developmental regulatory RNA (FENDRR) in AP progression. Caerulein with or without LPS- induced or taurolithocholic acid 3-sulfate (TLC-S)-induced AP mouse models and cell models were performed for the validation of FENDRR expression in vivo and in vitro, respectively. Histopathological examinations of pancreatic tissues were performed to evaluate the severity of AP. Transmission electron microscopy was utilized to visualize the autophagic vacuoles. siRNA specifically targeting FENDRR was further applied. Flow cytometry was employed to assess cell apoptosis. ELISA, immunoflureoscence, and western blotting analysis were also performed to determine the levels of inflammatory cytokines and autophagy activity. RNA immunoprecipitation (RIP) and chromatin immunoprecipitation (ChIP) assays were carried out to reveal the epigenetic regulation of FENDRR on ATG7. Additionally, silencing FENDRR was also verified in AP mouse models. Higher FENDRR and impaired autophagy were displayed in both AP mouse models and cell models. FENDRR knockdown dramatically attenuated caerulein- or TLC-S-induced AR42J cells apoptosis and autophagy suppression. Further mechanistic experiments implied that the action of FENDRR is moderately attributable to its repression of ATG7 via direct interaction with the epigenetic repressor PRC2. Moreover, the silencing of FENDRR significantly induced the promotion of ATG7, thus alleviating the development of AP in vivo. Our study highlights FENDRR as a novel target that may contribute to AP progression, suggesting a therapeutic target for AP treatment.

Exercise Preconditioning Promotes Autophagy to Cooperate for Cardioprotection by Increasing LC3 Lipidation-Associated Proteins

The cardioprotection of exercise preconditioning (EP) has been well documented. EP can be divided into two phases that are the induction of exercise preconditioning (IEP) and the protection of exercise preconditioning (PEP). PEP is characterized by biphasic protection, including early exercise preconditioning (EEP) and late exercise preconditioning (LEP). LC3 lipidation-mediated autophagy plays a pivotal role in cardioprotection. This study aimed to investigate the alterations of LC3 lipidation-associated proteins during EP-induced cardioprotection against myocardial injury induced by exhaustive exercise (EE) was used in a rat model of EP. These rats were subjected to an intermittent exercise consisting of four periods, with each period including 10 min of running at 30 m/min and 0% grade (approximately 75% VO_2max) followed by 10 min of intermittent rest. A model of EE-induced myocardial injury was developed by subjecting rats to a consecutive running (30 m/min, 0% grade) till exhaustion. Following EEP, the colocalization of LC3 with Atg7 was significantly increased, and LC3-I, LC3-II, LC3-II/LC3-I, Atg7, Atg4B, and Atg3 levels were significantly increased. Atg7, Atg4B, and Atg3 mRNAs were all significantly upregulated, and LC3 mRNAs tended to be higher. Following LEP, Atg4B, and Atg3 levels were significantly increased. Atg7, Atg4B, and Atg3 mRNAs were all significantly upregulated, and LC3 mRNAs tended to be higher. A group of rats were subjected to EEP followed by EE, and the co-localization of LC3 with Atg7 was significantly increased, while LC3-I, LC3-II, LC3-II/LC3-I, Atg7, Atg4B, and Atg3 levels were also significantly increased. Moreover, there was a significant increase in the co-localization of LC3 with Atg7, LC3-I, LC3-II, Atg7, and Atg4B levels during LEP followed by EE. The formation of autophagosome during LEP followed by EE may have been weaker than that during EEP followed by EE due to the lower lipidation of LC3. EP may promote autophagy to maintain cell homeostasis and survival, which cooperates for cardioprotection of alleviating exhaustive exercise-induced myocardial injury by increasing LC3 lipidation-associated proteins. There is a difference between EEP and LEP in terms of the mechanisms of cardioprotection afforded by these respective conditions. The positive regulation of transcription and translation level of LC3 lipidation-associated proteins may all be involved in the mechanism of EEP and LEP, while compared with LEP, the regulation of translation level of EEP is more positively to promote autophagy.

LncRNA CCAT1 promotes autophagy via regulating ATG7 by sponging miR-181 in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a significant clinical challenge, and the mechanisms underlying HCC pathogenesis remain incompletely understood. Colon cancer associated transcript 1 (CCAT1), is one novel long noncoding RNA (lncRNA) which is upregulated in HCC. Autophagy is a vital process in HCC progression, and it is unknown whether CCAT1 regulates autophagy in HCC.

MATERIALS AND METHODS

Immunofluorescence staining and transmission electron microscopy were used to analyze autophagy activity. Luciferase assay was performed to confirm miRNA-181a-5p (miR-181a-5p) bind CCAT1 and ATG7.

RESULTS

CCAT1 levels were higher in tissue and cell lines of HCC. In function research, we found that CCAT1 facilitates HCC cell autophagy and cell proliferation. Our results show that, mechanistically, CCAT1 promotes autophagy through functioning as a sponge for miR-181a-5p, and then regulating ATG7 expression.

CONCLUSION

Our findings indicate CCAT1 may play a role in regulating autophagy by sponging miR-181a-5p in HCC.

Autophagy is involved in aldosterone‑induced mesangial cell proliferation

The aim of the present study was to investigate whether autophagy is involved in aldosterone (Aldo)-induced mesangial cell (MC) proliferation. MCs were incubated with 10‑7 M Aldo for 24 h. Proliferation of MCs, and the underlying mechanisms, were subsequently analyzed using [3H]thymidine assay, cell counting assay, western blotting and RNA interference (RNAi). Aldo was revealed to induce autophagy, as indicated by the increased conversion from microtubule‑associated protein 1A/1B‑light chain 3 (LC3)‑I to LC3‑II, the increased expression levels of autophagy‑related gene 7 (Atg7) and the increased degradation of p62, which was accompanied by MC proliferation. Notably, pharmacological inhibition of autophagy or RNAi‑mediated knockdown of Atg7 attenuated Aldo‑induced MC proliferation, suggesting that autophagy was at least partially responsible for this effect. The results of the present study provided evidence that autophagy is critical for regulating Aldo‑induced MC proliferation.

Atg7 deficiency impairs host defense against Klebsiella pneumoniae by impacting bacterial clearance, survival and inflammatory responses in mice

Klebsiella pneumoniae (Kp) is a Gram-negative bacterium that can cause serious infections in humans. Autophagy-related gene 7 (Atg7) has been implicated in certain bacterial infections; however, the role of Atg7 in macrophage-mediated immunity against Kp infection has not been elucidated. Here we showed that Atg7 expression was significantly increased in murine alveolar macrophages (MH-S) upon Kp infection, indicating that Atg7 participated in host defense. Knocking down Atg7 with small-interfering RNA increased bacterial burdens in MH-S cells. Using cell biology assays and whole animal imaging analysis, we found that compared with wild-type mice atg7 knockout (KO) mice exhibited increased susceptibility to Kp infection, with decreased survival rates, decreased bacterial clearance, and intensified lung injury. Moreover, Kp infection induced excessive proinflammatory cytokines and superoxide in the lung of atg7 KO mice. Similarly, silencing Atg7 in MH-S cells markedly increased expression levels of proinflammatory cytokines. Collectively, these findings reveal that Atg7 offers critical resistance to Kp infection by modulating both systemic and local production of proinflammatory cytokines.