Alphavirus Assembly andEntry: RoleoftheCytoplasmic Tail oftheElSpike Subunit (original) (raw)
Related papers
Alphavirus assembly and entry: role of the cytoplasmic tail of the E1 spike subunit
Journal of Virology
The alphavirus Semliki Forest virus (SFV) matures by budding at the cell surface. This process is driven by interactions of its membrane protein heterodimer E2-E1 and the nucleocapsid. The virus penetrates into new cells by an E1-mediated membrane fusion event. The E1 subunit has a short, strongly positively charged cytoplasmic tail peptide (Arg-Arg) which is very conserved among different alphavirus E1 proteins. In this work, we have used in vitro mutagenesis of a full-size cDNA clone of SFV to study the role of the tail peptide of the E1 subunit in virus budding and fusion processes in baby hamster kidney cell culture. Our results suggest that the E1 tail plays no major role in SFV multiplication in animal cell culture.
Semliki forest virus entry and the endocytic pathway
Biochemical Society Transactions
Membrane-containing (enveloped) animal viruses introduce their genomes into host cells by membrane fusion. The reaction is catalysed by specific fusogenic spike glycoproteins on the surface of the virions and for many enveloped viruses, including toga-, rhabdo-and orthomyxoviruses, mildly acidic conditions (pH 6.2 and below) are required to trigger the fusion activity. In the normal course of entering cells a virus will only encounter a low pH in the endocytic pathway, and consequently the fusion occurs, after endocytosis of intact virions, with the membrane of an acidic intracellular organelle (for recent reviews see White et al., .
Formation of the Semliki Forest virus membrane glycoprotein complexes in the infected cell
Journal of General …, 1980
In Semliki Forest virus (SFV)-infected cells, all structural proteins are translated from a 26S mRNA using a single initiation site. The capsid protein which is made first is released into the cytoplasm whereas the two membrane proteins, p62 (the precursor for E2 and E3) and El, are inserted into the rough endoplasmic reticulum membrane. Based on gradient centrifugation and cross-linking studies, it can be seen that the p62 and Et polypeptides form a compleximmediately after synthesis and migrate to the plasma membrane in the form of a p62-EI complex. The processing of p62 to E2 and E3 is first seen 25 to 30 min after a IO min pulse of radioactive amino acids. This cleavage can be inhibited by addition of antisera specific for EI and E3, thus supporting the view that, as in the case of the related Sindbis virus, this cleavage occurs on the external face of the plasma membrane. Proteolytic digestion of crude vesicle preparations derived from plasma membranes, combined with peptide mapping, indicate that the carboxy-terminal end of E2 spans the cell plasma membrane, there being a portion of mol. wt about 3ooo located towards the cytosol.
Archives of Virology, 1997
During the initial stages of Semliki Forest virus (SFV) infection in mammalian (baby hamster kidney, BHK) cells, the cleavage of SFV capsid protein could be detected. Analysis of subcellular fractions from SFV-infected BHK cells showed that (a) cleavage of the capsid protein occurred within a prelysosomal compartment of the endocytotic pathway, and (b) following release of the nucleocapsid into the cytoplasm, a 17.5 kD capsid protein fragment could be detected in the subcellular fraction which contained ribosomes. We have previously reported the cleavage of incoming SFV capsid protein in mosquito cells, too. Thus, the proteolytic cleavage of incoming SFV capsid protein is a feature which is common to both invertebrate and mammalian cells. These data further support our hypothesis that the cleavage of incoming capsid protein might provide the conformational change which primes the SFV nucleocapsid for uncoating.
Journal of virology, 1981
When Semliki Forest virus temperature-sensitive mutant ts-3 was grown at the restrictive temperature an aberrant nascent cleavage of the 130,000-dalton structural polyprotein took place relatively frequently. This cleavage yielded an abnormal 86,000-dalton fusion protein (p86) consisting of the amino-terminal capsid protein linked to the amino acid sequences of envelope protein p62 (a precursor of E3 and E2). The other cleavage product was the carboxy-terminal envelope protein E1. p86 was not glycosylated and was sensitive to the action of protease in the microsomal fraction, whereas E1 was glycosylated and protected from proteases, indicating that it had been segregated into the cysternal side of the microsomal vesicles. All attempts to show the E1 protein at the cell surface have failed so far, suggesting that it remains associated with intracellular membranes. When ts-3-infected cells labeled at the restrictive temperature were shifted to the permissive temperature the only label...
Interactions of Semliki Forest virus spike glycoprotein rosettes and vesicles with cultured cells
The Journal of Cell Biology
Semliki Forest virus (SFV)-derived spike glycoprotein rosettes (soluble octameric complexes), virosomes (lipid vesicles with viral spike glycoproteins), and liposomes (proteinfree lipid vesicles) have been used to investigate the interaction of subviral particles with BHK-21 cells. Cell surface binding, internalization, degradation, and low pH-dependent membrane fusion were quantitatively determined. Electron microscopy was used to visualize the interactions.