Role of Capsid anchor in the morphogenesis of Zika virus

The flavivirus capsid protein (C) is separated from the downstream pre-membrane (PrM) protein by a hydrophobic sequence named capsid anchor (Ca). During polyprotein processing, Ca is sequentially cleaved by the viral NS2B/NS3 protease on the cytosolic side and by signal peptidase on the luminal side of the ER. To date, Ca is considered important mostly for directing translocation of PrM into the ER lumen. In this study, the role of Ca in the assembly and secretion of ZIKV was investigated using a pseudovirus-based approach. Our results show that, while Ca-mediated anchoring of C to the ER membrane is not needed for the production of infective particles, Ca expression in cis with respect to PrM is strictly required to allow proper assembly of infectious particles. Finally, we show that the presence of a heterologous, but not the homologous, Ca induces degradation of E through the autophagy/lysosomal pathway.IMPORTANCE The capsid anchor (Ca) is a single pass transmembrane domain at the C-terminus of the capsid protein (C) known to function as a signal for the translocation of PrM into the ER lumen. The objective of this study was to further understand the role of Ca in ZIKV life cycle, whether involved in the formation of nucleocapsid through association with C or in the formation of viral envelope. In this study, we show that Ca has a function beyond the one of translocation signal, controlling protein E stability and therefore its availability for assembly of infectious particles

Rotavirus NS26 is modified by addition of single O-linked residues of N-acetylglucosamine

We studied the post-translational modification of NS26, the protein product of rotavirus gene 11 segment. Based on the presence of a putative N-glycosylation site and the high content of serine and threonine residues in gene 11 amino acid sequence we investigated whether NS26 is modified by carbohydrate addition. Specific antibodies raised against the gene 11 product expressed in Escherichia coli recognized in infected cells two polypeptides with apparent molecular weight of 26,000 (26-kDa polypeptide) and 28,000 (28-kDa polypeptide). Pulse-chase experiments demonstrated that the 26-kDa product was processed to the 28-kDa polypeptide. Both polypeptides were metabolically labeled with [3H]glucosamine, indicating the presence of a carbohydrate moiety on the protein. NS26 was found to be resistant to endo-β-N-acetylglucosaminidase H and endo-β-N-acetylglucosaminidase F/peptide:N-glycosidase F treatment, but sensitive to removal by alkali-induced β-elimination, suggesting that the saccharide chain was attached to the protein via an O-glycosidic linkage. Chromatographic analysis of total acid hydrolysates of [3H]glucosamine-labeled NS26-bound carbohydrate indicated the presence of N-acetylglucosamine. In addition, mild alkaline treatment of NS26 in the presence of NaB3H4 identified the O-linked carbohydrate moiety as N-acetylglucosamine. Taken together, these data demonstrate that NS26 is processed to a 28-kDa polypeptide by addition of O-linked monosaccharide residues of N-acetylglucosamine. © 1991.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Binders based on dimerised immunoglobulin VH domains

Antibody binding to antigen is mediated by the surface formed by the association of the two variable (V) regions of the L (VL) and H (VH) chains. The capacity of VL to dimerise and the high structural similarity of VL and VH domains suggested the possibility that VH could also associate. We show here that spontaneous formation of VH dimers (VHD) is in many cases permissive, producing stable molecules with antigen binding specificity. VHD were displayed on filamentous phages for the selection of antigen-specific binders. VHD were expressed and secreted efficiently from both bacteria and mammalian cells in different formats, including single-chain (VH(1)-linker-VH(2)), double chain ((VH(2)) and IgG analogues having the VL replaced by VH. The affinity (Kd,app) achieved with a VH dimer expressed in the IgG format, specific for a glutenin subunit was around 30 nM measured by two different methods, which was about 20 times higher than that corresponding to the VL/VH counterpart

A novel mechanism of resistance to α-difluoromethylornithine induced by cycloheximide. Growth with abnormally low levels of putrescine and spermidine

Treatment of the chemically transformed fibroblasts BP-A31 and other cell lines with low concentrations of cycloheximide (CHM) for 72 h followed by the removal of the protein synthesis inhibitor leads to the proliferation of α-difluoromethylornithine (DFMO)-resistant phenotypes. These drug-resistant cells contain almost no ornithine decarboxylase (ODC) activity and concomitantly very low levels of putrescine and spermidine. Southern blot analysis and measurements of ODC activity and intracellular polyamine levels showed that the described mechanism of inducing resistance to DFMO triggered by CHM does not involve ODC gene amplification, altered transport of the drug or reduced affinity of the enzyme for DFMO. © 1986.Fil:Medrano, E.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Burrone, O.R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Ferrer, M.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Algranati, I.D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Dengue e protein domain iii-based dna immunisation induces strong antibody responses to all four viral serotypes

10.1371/journal.pntd.0003947PLoS ONE97A02

Isolation of scFv antibody fragments against HER2 and CEA tumor antigens from combinatorial antibody libraries derived from cancer patients

Tumor cells expressing HER-2/neu and CEA antigens are potentially ideal targets for antibody-targeted therapy. In this study, two large human combinatorial libraries have been generated from the lymph nodes of breast cancer patients that express HER2 and CEA antigens in their tumors. These 'immune' libraries have been constructed in two different formats of scFv, differing in the length of the peptide linker connecting the two variable VH and VL domains. Libraries derived from these patients may contain a larger pool of anti-tumor antigen antibodies and are useful repertoire for isolating scFvs against any tumor markers. The results of this study showed that we were successful in obtaining human scFvs against HER-2/neu and CEA. For HER-2, cell-panning strategy was performed and resulted in two scFv binders that detected the complete HER-2 receptor on the cell membrane and internalized to the cells. Also, preliminary ELISA data showed that several anti-CEA scFv binders were isolated by panning. \ua9 2013 The International Alliance for Biological Standardization.Peer reviewed: YesNRC publication: Ye

Production of in vivo-biotinylated rotavirus particles

Although inserting exogenous viral genome segments into rotavirus particles remains a hard challenge, this study describes the in vivo incorporation of a recombinant viral capsid protein (VP6) into newly assembled rotavirus particles. In vivo biotinylation technology was exploited to biotinylate a recombinant VP6 protein fused to a 15 aa biotin-acceptor peptide (BAP) by the bacterial biotin ligase BirA contextually co-expressed in mammalian cells. To avoid toxicity of VP6 overexpression, a stable HEK293 cell line was constructed with tetracycline-inducible expression of VP6–BAP and constitutive expression of BirA. Following tetracycline induction and rotavirus infection, VP6–BAP was biotinylated, recruited into viroplasms and incorporated into newly assembled virions. The biotin molecules in the capsid allowed the use of streptavidin-coated magnetic beads as a purification technique instead of CsCl gradient ultracentrifugation. Following transfection, double-layered particles attached to beads were able to induce viroplasm formation and to generate infective viral progeny

Membrane IgE binds and activates Fc epsilon RI in an antigen-independent manner

Interaction of secretory IgE with Fc epsilon RI is the prerequisite for allergen-driven cellular responses, fundamental events in immediate and chronic allergic manifestations. Previous studies reported the binding of soluble Fc epsilon RI alpha to membrane IgE exposed on B cells. In this study, the functional interaction between human membrane IgE and human Fc epsilon RI is presented. Four different IgE versions were expressed in mouse B cell lines, namely: a truncation at the C epsilon 2-C epsilon 3 junction of membrane IgE isoform long, membrane IgE isoform long (without Ig alpha /Ig beta BCR accessory proteins), and both epsilon BCRs (containing membrane IgE isoforms short and long). All membrane IgE versions activated a rat basophilic leukemia cell line transfected with human Fc epsilon RI, as detected by measuring the release of both preformed and newly synthesized mediators. The interaction led also to Ca super(2+) responses in the basophil cell line, while membrane IgE-Fc epsilon RI complexes were detected by immunoprecipitation. Fc epsilon RI activation by membrane IgE occurs in an Ag-independent manner. Noteworthily, human peripheral blood basophils and monocytes also were activated upon contact with cells bearing membrane IgE. In humans, the presence of Fc epsilon RI in several cellular entities suggests a possible membrane IgE-Fc epsilon RI-driven cell-cell dialogue, with likely implications for IgE homeostasis in physiology and pathology