Viral infection converts the normal constitution of a cell to optimise viral entry, replication, and virion production. These conversions contain alterations or disruptions of the tight and adherens junctions between cells as part of their pathogenesis, and reorganise cellular microfilaments that initiate, sustain and spread the viral infections and so on. Using porcine epidemic diarrhoea virus (PEDV), transmissible gastroenteritis virus (TGEV) and a model of normal intestinal epithelial cells (IPEC-J2), we researched the interaction between tight and adherens junctions and microfilaments of IPEC-J2 cells with these viruses. In our work, the results showed that IPEC-J2 cells were susceptible to TGEV and PEDV infection. And TGEV could impair the barrier integrity of IPEC-J2 cells at early stages of infection through down-regulating some proteins of tight and adherens junctions, while PEDV cloud cause a slight of damage in the integrity of epithelial barrier. In addition, they also could affect the microfilaments remodelling of IPEC-J2 cells, and the drug-interfered microfilaments could inhibit viral replication and release. Furthermore, PEDV+TGEV co-infection was more aggravating to damage of tight junctions and remodelling of microfilaments than their single infection. Finally, the PEDV and TGEV infection affected the MAPK pathway, and inhibition of MAPK pathway regulated the changes of tight junctions and microfilaments of cells. These studies provide a new insight from the perspective of the epithelial barrier and microfilaments into the pathogenesis of PEDV and TGEV.

The intestinal epithelial cells contain a large number of mitochondria for persisting absorption and barrier function. Selective autophagy of mitochondria (mitophagy) plays an important role in the quality control of mitochondria and maintenance of cell homeostasis. Transmissible gastroenteritis virus (TGEV) is a porcine enteropathogenic coronavirus which induces malabsorption and lethal watery diarrhea in suckling piglets. The role of mitophagy in the pathological changes caused by TGEV infection is unclear. Here, we report that TGEV induces mitophagy to suppress oxidative stress and apoptosis induced by viral infection in porcine epithelial cells (IPEC-J2). We observe that TGEV infection induce mitochondrial injury, abnormal morphology, complete mitophagy, and without obvious apoptosis after TGEV infection. Meanwhile, TGEV also induces DJ-1 and some antioxidant genes upregulation to suppress oxidative stress induced by viral infection. Furthermore, silencing DJ-1 inhibit mitophagy and increase apoptosis after TGEV infection. In addition, we demonstrate for the first time that viral nucleocapsid protein (N) is located in mitochondria and mitophagosome during virus infection or be expressed alone. Those results provide a novel perspective for further improvement of prevention and treatment in TGEV infection. These results suggest that TGEV infection induce mitophagy to promote cell survival and possibly viral infection.

Liver fibrosis is overly exuberant wound healing that leads to portal hypertension or liver cirrhosis. Recent studies have demonstrated the functions of bone morphogenetic protein 9 (BMP9) in liver fibrosis, and thus, targeting liver-specific BMP9 abnormalities will become an attractive approach for developing therapeutics to treat liver fibrosis. Here, we reveal that BMP9 serves as a valuable serum diagnostic indicator and efficient therapeutic target to attenuate liver fibrogenesis. Our analysis of biopsies from liver fibrotic patients revealed that higher BMP9 levels accompanied advanced stages of liver fibrosis. In mouse models, recombinant Bmp9 overexpression accelerated liver fibrosis, and adenovirus-mediated Bmp9 knockdown attenuated liver fibrogenesis. Intriguingly, BMP9 directly stimulated hepatic stellate cell activation via the SMAD signaling pathway to enhance hepatic fibrosis. Moreover, an inhibitory monoclonal antibody targeting Bmp9 was efficacious in treatment of mice with liver fibrosis. These observations delineate a novel model in which BMP9 directly drives SMAD/ID1 signaling in hepatic stellate cells, which modulates liver fibrogenesis development. Moreover, the findings unveil a promising surrogate biomarker for the diagnosis of hepatic fibrosis, thereby representing an efficient "BMP9 neutralization" approach in alleviating hepatic fibrosis.

Transmissible gastroenteritis virus (TGEV), a coronavirus, causes severe diarrhea and high mortality in newborn piglets. The porcine intestinal epithelium is the target of TGEV infection, but the mechanisms that TGEV disrupts the actin cytoskeleton and invades the host epithelium remain largely unknown. We not only found that TGEV infection stimulates F-actin to gather at the cell membrane but the disruption of F-actin inhibits TGEV entry as well. Cofilin is involved in F-actin reorganization and TGEV entry. The TGEV spike protein is capable of binding with EGFR, activating the downstream phosphoinositide-3 kinase (PI3K), then causing the phosphorylation of cofilin and F-actin polymerization via Rac1/Cdc42 GTPases. Inhibition of EGFR and PI3K decreases the entry of TGEV. EGFR is also the upstream activator of mitogen-activated protein kinase (MAPK) signaling pathways that is involved in F-actin reorganization. Additionally, lipid rafts act as signal platforms for the EGFR-associated signaling cascade and correlate with the adhesion of TGEV. In conlusion, these results provide valuable data of the mechanisms which are responsible for the TGEV pathogenesis and may lead to the development of new methods about controlling TGEV.