McGinnes L W, Morrison T G
Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Ave. North, Worcester, Massachusetts 01655, USA.
J Virol. 2006 Mar;80(6):2894-903. doi: 10.1128/JVI.80.6.2894-2903.2006.
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.
副粘病毒附着蛋白的受体结合以及附着蛋白与融合（F）蛋白之间的相互作用被认为是激活F蛋白活性的核心；然而，其中涉及的机制尚不清楚。为了探究新城疫病毒（NDV）HN与F蛋白相互作用以及HN蛋白与唾液酸受体附着之间的关系，通过从转染禽细胞提取物中进行相互免疫共沉淀来检测和定量含HN和F蛋白的复合物。为了抑制HN蛋白与受体的结合，从转染开始就将转染了HN和F蛋白cDNA的细胞与神经氨酸酶一起孵育。在这些条件下，未观察到融合现象，但HN和F蛋白复合物的量比未处理细胞提取物中检测到的量增加了两倍。用神经氨酸酶处理过的表达HN和F蛋白的细胞与未转染的靶细胞孵育以刺激附着，导致HN和F蛋白复合物的量减少了两倍。相反，检测到高水平的含有HN蛋白和未切割的F蛋白（F-K115Q）的复合物，并且这些水平不受细胞单层的神经氨酸酶处理或与靶细胞孵育的影响。这些结果表明，在没有受体结合的情况下，HN和F蛋白存在于复合物中。此外，结果表明，不仅受体结合，而且F蛋白的切割对于含HN和F蛋白的复合物的解离都是必要的。
