The E protein of the Severe Acute Respiratory Syndrome Coronavirus binds the tight junction protein PALS1 through a novel PDZ domain-binding motif/PDZ domain interaction. Expression of E delays formation of tight junctions and alters cyst morphogenesis of MDCKII epithelial cells.

BackgroundEntry of Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) and its envelope fusion with host cell membrane are controlled by a series of complex molecular mechanisms, largely dependent on the viral envelope glycoprotein Spike (S). There are still many unknowns on the implication of cellular factors that regulate the entry process.Methodology/Principal FindingsWe performed a yeast two-hybrid screen using as bait the carboxy-terminal endodomain of S, which faces the cytosol during and after opening of the fusion pore at early stages of the virus life cycle. Here we show that the ezrin membrane-actin linker interacts with S endodomain through the F1 lobe of its FERM domain and that both the eight carboxy-terminal amino-acids and a membrane-proximal cysteine cluster of S endodomain are important for this interaction in vitro. Interestingly, we found that ezrin is present at the site of entry of S-pseudotyped lentiviral particles in Vero E6 cells. Targeting ezrin function by small interfering RNA increased S-mediated entry of pseudotyped particles in epithelial cells. Furthermore, deletion of the eight carboxy-terminal amino acids of S enhanced S-pseudotyped particles infection. Expression of the ezrin dominant negative FERM domain enhanced cell susceptibility to infection by SARS-CoV and S-pseudotyped particles and potentiated S-dependent membrane fusion.Conclusions/SignificanceEzrin interacts with SARS-CoV S endodomain and limits virus entry and fusion. Our data present a novel mechanism involving a cellular factor in the regulation of S-dependent early events of infection.

Liver cancer (hepatocellular carcinoma, HCC) is one of the most prevalent malignancies worldwide. Because of the late diagnosis of the disease, the prognosis of HCC patient is often undesirable. Cancer Stem Cell (CSC), which represents a subpopulation of cancer cells with stem-like properties, plays a critical role in tumorigenesis and contributes significantly to the relapse and chemo-drug resistance of cancers. The cell surface marker, CD133/Prominin-1, has been identified as a biomarker for CSC in various cancers, including HCC. To understand the role of CD133 in hepatocarcinogenesis, we expressed CD133 in HCC cells and showed that CD133 significantly promoted cell growth. Interestingly, our data also indicated that expression of CD133 led to chromosomal instability indicated by elevation of aneuploidy population and centrosome numbers in CD133 expressing cells. To understand the molecular mechanism, we observed that a putative tumour suppressor in HCC, called TAX1-binding protein 2 (TAX1BP2), which functions as a centrosome over-duplication suppresser, was downregulated by CD133. Taken together, these data suggest that CD133 plays an oncogenic role in HCC and may downregulate TAX1BP2 to promote chromosome instability, centrosome duplication and hepatocarcinogenesis. Citation Format: Yick Pang Ching, Wing Lim Chan. The oncogenic role of CD133 in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3386.