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Localization of nucleocapsid associated polypeptides in measles virus-infected cells by immunogold labelling after
1Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie, Hamburg, Federal Republic of Germany.
Abstract:
The nucleo-, phospho- and matrix protein of measles virus were localized at high resolution within infected cells by use of post-embedding immunogold labelling techniques. In general, labelling with monospecific antibodies as well as with a polyvalent rabbit anti-measles hyperimmune antiserum revealed measles virus polypeptides to be distributed non-randomly within infected cells with the label largely confined to specific sites, namely inclusions of nucleocapsids and assembled virus structures at the plasma membrane. Immunogold double labelling indicated that the phosphoprotein strictly co-localized with the nucleoprotein in cytoplasmic inclusions of nucleocapsids and in budding virions, whereas intranuclear inclusions of nucleocapsids were devoid of phosphoprotein labelling. Antibodies to the matrix protein clearly labelled assembled virus structures at the plasma membrane but exhibited no significant cytoplasmic or intranuclear reaction. The data indicate that the composition of nucleocapsids varies with the cellular compartment with which they are associated, supporting the view of a rapid assembly of paramyxovirus nucleocapsid polypeptides, and emphasize the proposed selective role of the matrix protein in virus assembly and budding at the plasma membrane.
Insights
Measles virus proteins localize to specific cellular sites, including nucleocapsids and the plasma membrane. Protein localization reveals distinct roles in virus assembly and budding, particularly for the matrix protein.
Area of Science:
- Virology
- Cell Biology
Background:
- Measles virus is a significant human pathogen.
- Understanding viral protein localization is crucial for comprehending its replication cycle.
Purpose of the Study:
- To high-resolution localize measles virus nucleo-, phospho-, and matrix proteins within infected cells.
- To elucidate the roles of these proteins in viral assembly and budding.
Main Methods:
- Post-embedding immunogold labeling techniques were employed.
- Monospecific and polyvalent antisera were used for high-resolution labeling.
- Immunogold double labeling was performed to assess co-localization.
Main Results:
- Viral proteins were non-randomly distributed, primarily in nucleocapsid inclusions and at the plasma membrane.
- Phosphoprotein co-localized with nucleoprotein in cytoplasmic inclusions and budding virions, but not intranuclear inclusions.
- Matrix protein was localized to assembled virus structures at the plasma membrane, with minimal cytoplasmic or intranuclear presence.
Conclusions:
- Nucleocapsid composition varies depending on the cellular compartment.
- This supports rapid assembly of paramyxovirus nucleocapsid polypeptides.
- The matrix protein plays a selective role in measles virus assembly and plasma membrane budding.