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Biosynthesis of mumps virus F glycoprotein: non-fusing strains efficiently cleave the F glycoprotein precursor
Abstract:
Mumps virus infection of the CV-1 cell line results either in no cytopathic effect or extensive cell fusion, depending upon the infecting mumps virus strain. Growth cycle analyses indicated that both types of infection were the result of multiple cycle replication of mumps virus. Intracellular virus-specific polypeptide synthesis was examined by pulse- and pulse-chase-labelling with radioactive amino acids and sugars. The major polypeptides seen on SDS-polyacrylamide gels were NP (69 000 mol. wt.), P (45 000 mol. wt.) and M (40 000 mol. wt.); a non-structural polypeptide (22 000 mol. wt.) was also present in infected cell lysates. The HN (74 000 to 79 000 mol. wt.) glycopolypeptide was detected in [3H]glucosamine- and [3H]mannose-labelled infected cells. A 65 000 mol. wt. species that had incorporated these precursors was seen in pulse-labelled infected cell lysates, and this glycopolypeptide vanished during the chase interval with the concomitant appearance of two glycopolypeptides (59 000 mol. wt. and 14 000 to 15 000 mol. wt.) which represented the F1 and F2 subunits of the F glycoprotein. Immunological data confirmed the relatedness of the 65 000 mol. wt. glycopolypeptide to the F glycoprotein and identified it as the precursor F0. The F0 precursor glycopolypeptide was seen in cells infected with both fusing and non-fusing strains, and F0 was processed completely to F glycoprotein for all infections. Thus, the lack of cell fusion after infection with certain mumps strains is not the consequence of incomplete processing of the F0 precursor.
Insights
Mumps virus infection causes cell fusion or no effect, depending on the strain. The F0 precursor protein is processed correctly in both cases, meaning incomplete processing does not explain the lack of cell fusion.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- Mumps virus infection of cell cultures can lead to varying cytopathic effects, including cell fusion or no observable damage.
- The outcome of infection depends on the specific mumps virus strain used.
- Understanding the molecular mechanisms behind these different outcomes is crucial for comprehending viral pathogenesis.
Purpose of the Study:
- To investigate the synthesis and processing of intracellular virus-specific polypeptides during mumps virus infection.
- To determine the role of the F0 precursor protein and its processing into the F glycoprotein in mediating cell fusion.
- To elucidate why certain mumps virus strains cause cell fusion while others do not.
Main Methods:
- Utilizing CV-1 cell lines infected with different mumps virus strains.
- Employing pulse- and pulse-chase-labeling techniques with radioactive amino acids and sugars to track protein synthesis.
- Analyzing intracellular polypeptides using SDS-polyacrylamide gel electrophoresis.
- Characterizing glycopolypeptides and their processing.
- Performing immunological assays to confirm protein identities and relationships.
Main Results:
- Identified major viral polypeptides including NP, P, and M, as well as a non-structural polypeptide.
- Detected the HN glycopolypeptide in infected cells.
- Observed a 65,000 mol. wt. precursor glycopolypeptide (F0) that was processed into F1 and F2 subunits of the F glycoprotein.
- Confirmed that F0 precursor processing to F glycoprotein occurs in infections with both fusing and non-fusing mumps virus strains.
- Found no evidence of incomplete F0 processing in non-fusing infections.
Conclusions:
- The lack of cell fusion in infections with certain mumps virus strains is not due to incomplete processing of the F0 precursor to the F glycoprotein.
- The processing of the F0 precursor is a complete process regardless of the fusion phenotype of the mumps virus strain.
- Further research is needed to identify the specific viral or cellular factors responsible for the differential cell fusion outcomes.