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Biosynthesis of measles virus hemagglutinin in persistently infected cells
Abstract:
The synthesis of the hemagglutinin (HA) glycoprotein of measles virus was investigated in a persistently infected cell line using a monoclonal anti-HA. The synthesis of the HA protein was shown to be associated with the rough endoplasmic reticulum. The unglycosylated (HA0) apoprotein is synthesized as a 65,000 dalton peptide and is inserted into the rough endoplasmic reticulum as a transmembrane protein with approximately 2 to 3000 daltons of the peptide exposed to the cytoplasmic membrane surface. Primary glycosylation of the HA protein was found to occur through the lipid-linked carrier, dolichol-phosphate, as determined by inhibition of glycosylation by tunicamycin. Glycosylation, however, was not a prerequisite for membrane insertion. Endo-beta-N-acetylglucosaminidase H digestion of the fully glycosylated HA protein indicated that both simple and complex oligosaccharides are present on the surface glycoprotein.
Insights
Measles virus hemagglutinin (HA) glycoprotein synthesis occurs in the endoplasmic reticulum. Glycosylation is not required for membrane insertion, and the final protein contains both simple and complex oligosaccharides.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Measles virus hemagglutinin (HA) is crucial for viral entry.
- Understanding HA synthesis provides insights into viral pathogenesis.
Purpose of the Study:
- To investigate the synthesis pathway of measles virus HA glycoprotein.
- To determine the role of glycosylation in HA membrane insertion.
Main Methods:
- Utilized a persistently measles virus-infected cell line.
- Employed monoclonal anti-HA antibodies for detection.
- Applied tunicamycin to inhibit glycosylation.
- Used Endo-beta-N-acetylglucosaminidase H for oligosaccharide analysis.
Main Results:
- HA protein synthesis is associated with the rough endoplasmic reticulum.
- The unglycosylated HA0 apoprotein (65 kDa) inserts into the ER membrane as a transmembrane protein.
- Primary glycosylation occurs via dolichol-phosphate, independent of membrane insertion.
- Fully glycosylated HA contains both simple and complex oligosaccharides.
Conclusions:
- The synthesis and membrane insertion of measles HA are complex processes.
- Glycosylation is a post-insertion modification event for HA.
- Characterization of HA synthesis aids in understanding measles virus replication.