Cells in G2／M phase increased in human nasopharyngeal carcinoma cellline by EBV-LMP1 through activation of NF-kB and AP-1

Although previous studies showed that the principal oncoprotein encoded by Epstein-Barr virus, latent membrane protein 1 (LMP1), could induce the nasopharyngeal carcinoma cells in G2/M phase increased, littleis known about the target molecules and mechanisms. The present study demonstrated that LMP1 couldinduce the accumulation of p53 protein and upregulate its transactivity in a dose dependent manner, whichresulted in the decrease of the kinase activity of cdc2/cyclin B complex and inducing arrest at G2/M phasethrough the activation of NF-kB and AP-1 signaling pathways, and the effect of NF-kB was more obviousthan that of AP-1. This study provided some significant evidence for further elucidating the molecular mechanisms that LMP1 had effects on the surveillance mechanism of cell cycle and promoting the survivalof transformed cells and tumorigenesis.     

TLR4 signaling induced TLR2 expression in the process of mimic cerebral ischemia/reperfusion in vitro

Both TLR4 and TLR2 participated in the mediation of the inflammatory injury in the process of partial cerebral ischemia/reperfusion.However,it still remains unclear whether a crosstalk exists between TLR2 and TLR4 in ischemic cerebral damage.In the present study,we investigated the effect of TLR4 signaling on TLR2 expression during mimic cerebral I/R in vitro.BV-2 cells were cultured and treated with ischemia/reperfusion,then transfected with the plasmid pEGFP-H1/TLR4-siRNA,the plasmid pEGFP-H1/control sequence-siRNA and the blank plasmid,respectively.Interestingly,the expression of TLR2 and TLR4 mRNA and protein,NF-κB p65 mRNA and supernatant TNF-α level were significantly higher in ischemia/reperfusion treated cells than those lack of ischemia/reperfusion treatment,and as compared with those in ischemia/reperfusion treated cells without transfection,no significant differences about the above mentioned gene and protein expression were found in the blank plasmid tranfected cells and the plasmid pEGFP-H1/control sequence-siRNA transfected cells respectively,while the expression levels in the plasmid pEGFP-H1/TLR4-siRNA transfected cells were significantly lower.Additionally,in order to determine the effects of pyrrolidinediethyldithiocarbamate (PDTC),an NF-κB inhibitor,on the TLR4-induced TLR2 expression in BV-2 cells treated with ischemia/reperfusion,it was found that TLR4 and TLR2 mRNA expressions in PDTC pretreated cells were significantly lower in comparison with normal saline pretreated cells and non-pretreated cells.The data suggested that TLR2 activation,signaled by TLR4 and regulated by NF-κB,might be directly involved play an important role in ischemia/reperfusion induced brain damage.     

Oncoprotein p28^GANK binds to RelA and retains NF-κB in the cytoplasm through nuclear export

p28^GANK （also known as PSMD 10, p28 and gankyrin） is an ankyrin repeat anti-apoptotic oncoprotein that is commonly overexpressed in hepatocellular carcinomas and increases the degradation of p53 and Rb. NF-IκB （nuclear factor-κB） is known to be sequestered in the cytoplasm by IκB （inhibitor of NF-κB） proteins [1, 2], but much less is known about the cytoplasmic retention of NF-κB by other cellular proteins. Here we show that p28^GANK inhibits NF-κB activity. As a nuclear-cytoplasmic shuttling protein, p28^GANK directly binds to NF-κB/RelA and exports RelA from nucleus through a chromosomal region maintenance-1 （CRM-1） dependent pathway, which results in the cytoplasmic retention of NF- κB/RelA. We demonstrate that all the ankyrin repeats of p28^GANK are required for the interaction with RelA and that the N terminus of p28^GANK, which contains the nuclear export sequence （NES）, is responsible for suppressing NF-κB/RelA nuclear translocation. These results suggest that overexpression of p28^GANK prevents the nuclear localization and inhibits the activity of NF-κB/RelA.     

Regulation of survivin and CDK4 by Epstein-Barr virus encoded latent membrane protein 1 in nasopharyngeal carcinoma cell lines

Latent membrane protein 1 （LMP1）, an important protein encoded by Epstein Barr virus （EBV）, has been implied to link with the pathogenesis of nasopharyngeal carcinoma （NPC）. Its dual effects of increasing cell proliferation and inhibiting cell apoptosis have been confirmed. In this study, we showed that the expression of Survivin and CDK4 protein in CNE-LMP1, a LMP1 positive NPC epithelial cell line, is higher than in LMP1 negative NPC epithelial cell line- CNE1, and the expression is LMP1 dosage-dependent. Although it was reported that Survivin specifically expressed in cell cycle G2/M phase, our studies suggested that LMP1 could promote the expression of Survivin in G0/G1, S and G2/ M phase. It also showed that Survivin and CDK4 could be accumulated more in the nuclei triggered by LMP1. More interestingly, Survivin and CDK4 could form a protein complex in the nuclei of CNE-LMP1 rather than in that of CNE1, which demonstrated that the interaction between these two proteins could be promoted by LMPI. These results strongly suggested that the role of LMP1 in the regulation of Survivin and CDK4 may also shed some light on the mechanism research of LMP1 in NPC.     

Involvement of ayu NOD2 in NF-κB and MAPK signaling pathways: Insights into functional conservation of NOD2 in antibacterial innate immunity

Nucleotide oligomerization domain 2(NOD2) is a major cytoplasmic sensor for pathogens and is critical for the clearance of cytosolic bacteria in mammals.However, studies regarding NOD2, especially the initiated signaling pathways, are scarce in teleost species. In this study, we identified a NOD2 molecule(PaNOD2) from ayu(Plecoglossus altivelis).Bioinformatics analysis showed the structure of NOD2 to be highly conserved during vertebrate evolution. Dual-luciferase reporter assays examined the activation of NF-κB signaling and Western blotting analysis detected the phosphorylation of three MAP kinases(p-38, Erk1/2, and JNK1/2).Functional study revealed that, like its mammalian counterparts, PaNOD2 was the receptor of the bacterial cell wall component muramyl dipeptide(MDP), and the leucine-rich repeat motif was responsible for the recognition and binding of Pa NOD2 with the ligand. Overexpression of PaNOD2 activated the NF-κB signaling pathway, leading to the upregulation of inflammatory cytokines, including TNF-α and IL-1β in HEK293 T cells and ayu head kidney-derived monocytes/macrophages(MO/MΦ).Particularly, we found that PaNOD2 activated the MAPK signaling pathways, as indicated by the increased phosphorylation of p-38, Erk1/2, and JNK1/2, which have not been characterized in any teleost species previously. Our findings proved that the NOD2 molecule and initiated pathways are conserved between mammals and ayu. Therefore, ayu could be used as an animal model to investigate NOD2-based diseases and therapeutic applications.     

TMEM43-S358L mutation enhances NF-κBTGFp signal cascade in arrhythmogenic right ventricular dysplasia/cardiomyopathy

Arrhythmogenic right ventricular dysplasia/cardiomyopathy(ARVD/C)is a genetic cardiac muscle disease that accounts for approximately 30%sudden cardiac death in young adults.The Ser358Leu mutation of transmembrane protein 43(TMEM43)was commonly identified in the patients of highly lethal and fully penetrant ARVD subtype,ARVD5.Here,we generated TMEM43 S358L mouse to explore the underlying mechanism.This mouse strain showed the classic patholo.gies of ARVD patients,including structural abnormalities and cardiac fibrofatty.TMEM43 S358L mutation led to hyper-activated nuclear factor kB(NFkB)activation in heart tissues and primary cardiomy.ocyte cells.Importantly,this hyper activation of NF-κB directly drove the expression of pro-fibrotic gene,transforming growth factor beta(TGFβ),and enhanced downstream signal,indicating that TMEM43 S358L mutation up-regulates NF-κB-TGFβ signal cascade during ARVD cardiac fibrosis.Our study partially reveals the regulatory mechanism of ARVD development.