Inhibition of receptor binding stabilizes Newcastle disease virus HN and F protein-containing complexes.
Receptor binding of paramyxovirus attachment proteins and the interactions between attachment and fusion (F) proteins are thought to be central to activation of the F protein activity; however, mechanisms involved are unclear. To explore the relationships between Newcastle disease virus (NDV) HN and F protein interactions and HN protein attachment to sialic acid receptors, HN and F protein-containing complexes were detected and quantified by reciprocal coimmunoprecipitation from extracts of transfected avian cells. To inhibit HN protein receptor binding, cells transfected with HN and F protein cDNAs were incubated with neuraminidase from the start of transfection. Under these conditions, no fusion was observed, but amounts of HN and F protein complexes increased twofold over amounts detected in extracts of untreated cells. Stimulation of attachment by incubation of untransfected target cells with neuraminidase-treated HN and F protein-expressing cells resulted in a twofold decrease in amounts of HN and F protein complexes. In contrast, high levels of complexes containing HN protein and an uncleaved F protein (F-K115Q) were detected, and those levels were unaffected by neuraminidase treatment of cell monolayers or by incubation with target cells. These results suggest that HN and F proteins reside in a complex in the absence of receptor binding. Furthermore, the results show that not only receptor binding but also F protein cleavage are necessary for disassociation of the HN and F protein-containing complexes.
McGinnes
L W
LW
Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Ave. North, Worcester, Massachusetts 01655, USA.
Morrison
T G
TG
D000818:Animals; D002460:Cell Line; D002642:Chick Embryo; D015707:HN Protein / Q000235:genetics / Q000378:metabolism*; D047468:Immunoprecipitation; D008561:Membrane Fusion; D009522:Newcastle disease virus / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D011956:Receptors, Cell Surface / Q000378:metabolism*; D014162:Transfection; D014760:Viral Fusion Proteins / Q000235:genetics / Q000378:metabolism*
D015707:HN Protein; D011956:Receptors, Cell Surface; D014760:Viral Fusion Proteins; C092488:sialic acid receptor