PDF(Pubmed)
Abstract：
Cell-cell fusion mediated by most paramyxovirus requires fusion protein (F) and attachment protein (H, HN, or G). The F protein is proteolytic cleaved to be fusogenically active. J paramyxovirus (JPV) has a unique feature in the family Paramyxoviridae: It encodes an integral membrane protein, syncytial protein (SP, formerly known as transmembrane protein, TM), which is essential in JPV-promoted cell-cell fusion (i.e., syncytial). In this study, we report that cleavage of SP is essential for its syncytial-promoting activity. We have identified the cleavage site of SP at amino acid residues 172 to 175, LKTG, and deletion of the \"LKTG\" residues abolished SP protein cleavage and its ability to promote cell-cell fusion. Replacing the cleavage site LKTG with a factor Xa protease cleavage site allows cleavage of the SP with factor Xa protease and restores its ability to promote cell-cell fusion. Furthermore, results from a hemifusion assay indicate that cleavage of SP plays an important role in the progression from the intermediate hemifusion state to a complete fusion. This work indicates that SP has many characteristics of a fusion protein. We propose that SP is likely a cell-cell fusion-promoting protein.
摘要：
大多数副粘病毒介导的细胞-细胞融合需要融合蛋白（F）和附着蛋白（H，HN,或G）。F蛋白被蛋白水解切割为具有融合活性。J副粘病毒（JPV）在副粘病毒科中具有独特的特征：它编码完整的膜蛋白，合胞蛋白(SP，以前称为跨膜蛋白，TM),这在JPV促进的细胞-细胞融合中是必不可少的(即，合胞体）。在这项研究中,我们报告说，SP的裂解对于其合胞体促进活性至关重要。我们已经确定了SP在氨基酸残基172至175，LKTG，“LKTG”残基的缺失消除了SP蛋白的裂解及其促进细胞-细胞融合的能力。用因子Xa蛋白酶切割位点替换切割位点LKTG允许用因子Xa蛋白酶切割SP并恢复其促进细胞-细胞融合的能力。此外，半融合分析的结果表明，SP的裂解在从中间半融合状态到完全融合的过程中起着重要作用。这项工作表明SP具有融合蛋白的许多特征。我们认为SP可能是一种细胞-细胞融合促进蛋白。
