Search results for "COS cells"
showing 10 items of 111 documents
Chaperones Involved in Hepatitis B Virus Morphogenesis
1999
Little is known about host cell factors necessary for hepatitis B virus (HBV) assembly which involves envelopment of cytosolic nucleocapsids by the S, M and L transmembrane viral envelope proteins and subsequent budding into intraluminal cisternae. Central to virogenesis is the L protein that mediates hepatocyte receptor binding and envelopment of capsids. To serve these topologically conflicting roles, L protein exhibits an unusual dual membrane topology, disposing its N-terminal preS domain inside and outside of the virion lipid envelope. The mixed topology is achieved by posttranslational preS translocation of about half of the L protein molecules across a post-endoplasmic reticulum memb…
Functional incorporation of green fluorescent protein into hepatitis B virus envelope particles
2004
AbstractThe envelope of hepatitis B virus (HBV), containing the L, M, and S proteins, is essential for virus entry and maturation. For direct visualization of HBV, we determined whether envelope assembly could accommodate the green fluorescent protein (GFP). While the C-terminal addition of GFP to S trans-dominant negatively inhibited empty envelope particle secretion, the N-terminal GFP fusion to S (GFP.S) was co-integrated into the envelope, giving rise to fluorescent particles. Microscopy and topogenesis analyses demonstrated that the proper intracellular distribution and folding of GFP.S, required for particle export were rescued by interprotein interactions with wild-type S. Thereby, a…
Hepatitis B Virus Large Envelope Protein Interacts with γ2-Adaptin, a Clathrin Adaptor-Related Protein
2001
ABSTRACT For the outcome of a hepatitis B virus (HBV) infection, the viral L envelope protein with its pre-S domain performs pivotal functions by mediating attachment of HBV to liver cells, envelopment of viral capsids, release of (sub)viral particles, regulation of supercoiled DNA amplification, and transcriptional transactivation. To assess its multiple functions and host-protein assistance involved, we initiated a two-hybrid screen using the L-specific pre-S1 domain as bait. With this approach, we have identified γ2-adaptin, a putative member of the clathrin adaptor proteins responsible for protein sorting and trafficking, as a specific binding partner of L protein. Evidence for a physic…
Possible role of human interleukin-6 and soluble interleukin-6 receptor in hepatitis B virus infection
2001
Human interleukin-6 has been shown to promote hepatitis B virus (HBV) infection. However, it is not clear whether this influence is the result of a direct interaction between interleukin-6 (IL-6) and the HBV envelope proteins or of a rather indirect mechanism. A direct interaction of IL-6 and the preS region of the large envelope protein (L-protein) of HBV has been reported. In this study we assessed the binding of IL-6 and of the IL-6 receptor subunits to the preS region of the L-protein of HBV. Binding of IL-6 and IL-6 receptor subunits sIL-6R and gp130 to preS was assessed by immunoprecipitation with recombinant preS proteins. In patient sera IL-6 and sIL-6R concentrations were analysed …
The asialoglycoprotein receptor mediates hepatic binding and uptake of natural hepatitis B virus particles derived from viraemic carriers.
1994
As a putative mechanism of hepatitis B virus (HBV) uptake into hepatocytes the interaction between HBV and the hepatic, human-derived asialoglycoprotein receptor (ASGPR) was investigated. Sera from patients with different variations of hepatitis B surface antigen-(HBsAg) positive chronic hepatitis, HBV particles isolated from HBV carriers with high-titre viraemia and commercial HBsAg served as sources of HBV. ASGPR was affinity-purified from human liver. HBV that had bound to isolated ASGPR was either detected by radio-immunoassay using solid-phase bound ASGPR or enzyme immunoassay with biotin-ASGPR bound to immobilized HBV. Furthermore, binding and uptake of purified, 125I-labelled HBV par…
Polyethylenimine is a strong inhibitor of human papillomavirus and cytomegalovirus infection.
2012
ABSTRACT Polyethylenimines are cationic polymers with potential as delivery vectors in gene therapy and with proven antimicrobial activity. However, the antiviral activity of polyethylenimines has not been addressed in detail thus far. We have studied the inhibitory effects of a linear 25-kDa polyethylenimine on infections with human papillomaviruses and human cytomegaloviruses. Preincubation of cells with polyethylenimine blocked primary attachment of both viruses to cells, resulting in a significant reduction of infection. In addition, the dissemination of human cytomegalovirus in culture cells was efficiently reduced by recurrent administration of polyethylenimine. Polyethylenimine conce…
Polo-like kinase 1 as a target for human cytomegalovirus pp65 lower matrix protein
1999
ABSTRACT Human cytomegalovirus (HCMV) pp65 protein is the major constituent of viral dense bodies but is dispensable for viral growth in vitro. pp65 copurifies with a S/T kinase activity and has been implicated in phosphorylation of HCMV IE1 immediate-early protein and its escape from major histocompatibility complex 1 presentation. Furthermore, the presence of pp65 correlates with a virion-associated kinase activity. To clarify the role of pp65, yeast two-hybrid system (THS) screening was performed to identify pp65 cellular partners. A total of 18 out of 48 yeast clones harboring cDNAs for putative pp65 binding proteins encoded the Polo-like kinase 1 (Plk1) C-terminal domain. Plk1 behaved …
Highly efficient transport of carboxyfluorescein diacetate succinimidyl ester into COS7 cells using human papillomavirus-like particles
2003
AbstractHuman papillomavirus virus-like particles (VLPs) have recently been used to deliver genes into mammalian cells in vitro and in vivo. Here, we investigated whether VLPs may serve as an efficient carrier of low molecular weight compounds (e.g. hormones, vitamins, peptides etc.) into cells. COS7 cells were incubated with recombinant HPV-16L1/L2 VLPs labelled with the fluorescence dye carboxyfluorescein diacetate succinimidyl ester. Using flow cytometry, we demonstrate that labelled VLPs can specifically bind to the cell surface followed by their complete internalisation. Our results indicate that VLPs are promising vehicles for highly efficient delivery of low molecular weight compound…
Post-translational modifications in the survival motor neuron protein
2004
Spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by a progressive loss of the spinal motoneurons. The SMA-determining gene has been termed survival motor neuron (SMN) and is deleted or mutated in over 98% of patients. The encoded gene product is a protein expressed as different isoforms. In particular, we showed that the rat SMN cDNA produces two isoforms with Mr of 32 and 35 kDa, both localized in nuclear coiled bodies, but the 32 kDa form is also cytoplasmic, whereas the 35 kDa form is also microsomal. To determine the molecular relationship between these two isoforms and potential post-translational modifications, we performed transfection experiments with a …
Human papillomavirus infection requires cell surface heparan sulfate.
2001
ABSTRACT Using pseudoinfection of cell lines, we demonstrate that cell surface heparan sulfate is required for infection by human papillomavirus type 16 (HPV-16) and HPV-33 pseudovirions. Pseudoinfection was inhibited by heparin but not dermatan or chondroitin sulfate, reduced by reducing the level of surface sulfation, and abolished by heparinase treatment. Carboxy-terminally deleted HPV-33 virus-like particles still bound efficiently to heparin. The kinetics of postattachment neutralization by antiserum or heparin indicated that pseudovirions were shifted on the cell surface from a heparin-sensitive into a heparin-resistant mode of binding, possibly involving a secondary receptor. Alpha-6…