Subcellular localization of DAXX influence ox-LDL induced apoptosis in macrophages

The death domain-associated protein suppresses porcine epidemic diarrhea virus replication by interacting with signal transducer and activator of transcription 1 and inducing downstream ISG15 expression

Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus that causes acute enteric disease in piglets and severely threatens the pig industry all over the world. Death domain-associated protein (DAXX) is a classical chaperone protein involved in multiple biological processes, such as cell apoptosis, transcriptional regulation, DNA damage repair, and host innate immunity. However, whether DAXX functions in the anti-PEDV innate immune responses remains unclear. In this study, we found that PEDV infection upregulated DAXX expression and induced its nucleocytoplasmic translocation in IPEC-J2 cells. Furthermore, we found that DAXX overexpression was inhibitory to PEDV replication, while downregulation of DAXX by RNA interference facilitated PEDV replication. The antiviral activity of DAXX was due to its positive effect on IFN-λ3-STAT1 signaling, as DAXX positively regulated STAT1 activation through their interaction in cytoplasm and enhancing the downstream ISG15 expression. Mutation of tryptophan at 621 to alanine in DAXX increased its abundance in the cytoplasm, leading to the upregulation of STAT1 phosphorylation and ISG15 expression. It indicated that cytoplasmic fraction of DAXX was advantageous for the STAT1-ISG15 signaling axis and PEDV inhibition. In summary, these results show that DAXX inhibits PEDV infection by increasing IFN-λ3-induced STAT1 phosphorylation and the downstream ISG15 expression.

HPV16 E7 protein antagonizes TNF-α-induced apoptosis of cervical cancer cells via Daxx/JNK pathway

Human papillomavirus (HPV) E7 protein as an important viral factor was involved in the progression of cervical cancer by mediating the cellular signaling pathways. Daxx (Death domain-associated protein) can interact with a variety of proteins to affect the viral infection process. However, the interaction and its related function between HPV16 E7 and Daxx have not been adequately investigated. Here, it was found that HPV16 E7 can interact with Daxx in HeLa or C33A cells by co-immunoprecipitation. HPV16 E7 protein treatment can up-regulate Daxx protein expression, while the interference in Daxx expression and the agonists for JNK can both reduce the antagonistic effects of HPV16 E7 on TNF-α-induced apoptosis, suggesting that Daxx/JNK pathway may be involved in the anti-apoptotic activity of HPV16 E7.

[Daxx overexpression inhibits AngⅡ-induced proliferation and migration in vascular smooth muscle cells]

OBJECTIVE

To construct a recombinant lentiviral expression vector pCDH-Daxx-EGFP to investigate the effect of Daxx on the proliferation of vascular smooth muscle cells (VSMCs).

METHODS

The recombinant lentiviral expression vector pCDHDaxx-EGFP was constructed using PCR-based accurate synthesis method. After identification by sequencing and enzyme digestion, the recombinant lentiviral vector was contransfected into 293T cells with lentivirus packaging vector. The recombinant lentivirus particles were collected and purified to infect VSMCs, whose expression of Daxx was detected with Western boltting. The cells infected with the empty vector pCDH-EGFP or pCDH-Daxx-EGFP were incubated in serum-free medium or in the presence of angiotensin Ⅱ (AngⅡ). The cell viability was determined with MTT assay, and the cell cycle changes were analyzed with flow cytometry. The cell migration ability was assessed using a scratch wound healing assay. The expression of p-Akt protein in the cells was detected using Western blotting.

RESULTS

Double enzyme digestion and sequencing confirmed successful construction of the recombinant plasmid. Compared with the cells infected with the empty vector, the cells infected with pCDH-Daxx-EGFP exhibited significantly increased expressions of Daxx protein (P < 0.05). AngⅡ treatment of the cells infected with the pCDH-Daxx-EGFP, as compared with the cells infected with the empty vector, significantly lowered the cell viability, S phase cell ratio and cell migration ability (P < 0.05), and significantly decreased the expression level of p-Akt protein (P < 0.05).

CONCLUSIONS

We successfully constructed the recombinant lentiviral vector pCDH-Daxx-EGFP and overexpressed Daxx in primary cultured VSMCs using this vector. Daxx overexpression can inhibit AngⅡ-induced proliferation and migration in VSMCs probably by regulating p-Akt protein.

Death domain associated protein (Daxx), a multi-functional protein

Death domain associated protein (Daxx), a multi-functional protein, plays an important role in transcriptional regulation, cell apoptosis, carcinogenesis, anti-virus infection and so on. However, its regulatory mechanisms for both cell survival and apoptosis remain largely obscure. Our review of recent studies shows that Daxx has many interesting functional dualities and can provide a reference for further research on Daxx.

Protective effect of rosuvastatin treatment by regulating oxidized low-density lipoprotein expression in a rat model of liver fibrosis

The present study aimed to evaluate the protective effect of rosuvastatin treatment on the mechanism of oxidized low-density lipoprotein (Ox-LDL) in rats with liver fibrosis. In total, 72 male Sprague-Dawley rats were divided into 3 groups: 24 in the control group (A), 24 in the obstructive jaundice models group (B) and 24 in the rosuvastatin group (C). Each group was further divided into four subgroups for assessment at different time-points. The obstructive jaundice models were established and rosuvastatin was administered by gavage. Liver fibrosis indicators, Ox-LDL, malonaldehyde (MDA) and superoxide dismutase (SOD), were measured and liver pathological changes were observed at weeks 1, 2, 3 and 4 after model induction. In groups B and C, the rat models were successfully established, and there were significant changes in the expression of Ox-LDL and the three liver fibrosis indicators when compared to group A (P<0.01). However, the expression of Ox-LDL and the three liver fibrosis indicators in group C were decreased compared with group B (P<0.05), while SOD increased (P<0.05) and MDA decreased (P<0.05). The three liver fibrosis indicators were different in comparison to group B (P<0.05). Thus, there appeared to be an association between the expression of Ox-LDL and liver fibrosis. Treatment with rosuvastatin could regulate the expression of Ox-LDL and improve liver fibrosis in rat models with obstructive jaundice.

Pro-inflammatory effects of a litchi protein extract in murine RAW264.7 macrophages

It has been observed that the consumption of litchi often causes symptoms characterized by itching or sore throat, gum swelling, oral cavity ulcers and even fever and inflammation, which significantly impair the quality of life of a large population. Using the RAW264.7 cell line, a step-by-step strategy was used to screen for the components in litchi fruits that elicited adverse reactions. The adverse reaction fractions were identified by mass spectrometry and analyzed using the SMART program, and a sequence alignment of the homologous proteins was performed. MTT tests were used to determine the cytotoxicity of a litchi protein extract in RAW264.7 macrophages, and real-time PCR was applied to analyze the expression of inflammatory genes in the RAW264.7 cells treated with lipopolysaccharide or the litchi protein extract. The results showed that the litchi water-soluble protein extract could increase the production of the pro-inflammatory mediators IL-1β, iNOS and COX-2, and the anti-inflammatory mediator HO-1 in the RAW264.7 cell line. The 14-3-3-like proteins GF14 lambda, GF14 omega and GF14 upsilon were likely the candidate proteins that caused the adverse effects.