Functional interactions between the fusion protein and hemagglutinin-neuraminidase of human parainfluenza viruses.
The fusion glycoprotein (F) and hemagglutinin-neuraminidase (HN) genes of human parainfluenza virus type 2 (PI2) were molecularly cloned and expressed in HeLa-T4 cells by using the vaccinia virus-T7 transient expression system. Expression of the F and HN proteins was detected by using immunoprecipitation and surface immunofluorescence staining. Although the F protein was found to be cleaved into F1 and F2 and expressed on cell surfaces, no cell fusion was observed. However, cotransfection of the F-protein gene together with the P12 HN gene resulted in significant levels of cell fusion. Cell fusion was also observed when separate cell cultures were transfected with the HN and F genes and the F-expressing cells were mixed with the HN-expressing cells. Surprisingly, when the PI2 F protein was expressed together with the parainfluenza virus type 3 (PI3) HN protein, no fusion was detectable in the transfected cells. Similarly, no fusion was found upon coexpression of the PI2 HN and PI3 F proteins. However, coexpression of the PI3 F and HN proteins resulted in extensive cell fusion, which resembled the PI2 coexpression result. These results indicate that under the conditions used, the F protein is unable to cause fusion by itself and the HN protein provides a specific function in cell fusion which cannot be provided by another paramyxovirus attachment protein. Further, the results suggest that a type-specific functional interaction between the F and HN proteins is involved in mediating cell fusion.
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Department of Microbiology, University of Alabama, Birmingham 35294.
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D000818:Animals; D002459:Cell Fusion; D002478:Cells, Cultured; D006224:Cricetinae; D015707:HN Protein / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D011233:Precipitin Tests; D018108:Respirovirus / Q000378:metabolism*; D012703:Serotyping; D014162:Transfection; D014760:Viral Fusion Proteins / Q000378:metabolism*
D015707:HN Protein; D014760:Viral Fusion Proteins