Yamamoto-Goshima F, Maeno K
Laboratory of Virology, Nagoya University School of Medicine, Aichi, Japan.
Microbiol Immunol. 1994;38(10):819-22. doi: 10.1111/j.1348-0421.1994.tb01864.x.
ts7, a temperature-sensitive mutant defective in neuraminidase (NA) of influenza B/Kanagawa/73, lacks NA enzymatic activity at the nonpermissive temperature (37.5 C). When MDCK cells were infected with the mutant at the permissive temperature (32 C) and exposed to pH 5.2 medium, extensive cell fusion occurred. In contrast, at the nonpermissive temperature cells did not show cell fusion at all unless they were pretreated with trypsin, suggesting that at 37.5 C the hemagglutinin (HA) of ts7 is expressed at the cell surface in an uncleaved form. It was also found that the replacement of RNA segment 6 of ts7 with that of wild-type B/Lee resulted in the emergence of low pH-induced fusion activity as well as NA enzymatic activity at the incubation temperature of 37.5 C and that the addition of bacterial NA to the cultures infected with ts7 at 37.5 C early in infection brought about low pH-induced cell fusion. We suggest that the removal of neuraminic acid from the carbohydrate moiety of HA by NA is essential for the cleavage of HA by cellular protease.
ts7是乙型流感病毒/神奈川/73株神经氨酸酶（NA）缺陷的温度敏感突变体，在非允许温度（37.5℃）下缺乏NA酶活性。当MDCK细胞在允许温度（32℃）下感染该突变体并暴露于pH 5.2的培养基中时，会发生广泛的细胞融合。相反，在非允许温度下，除非用胰蛋白酶预处理，细胞根本不会出现细胞融合，这表明在37.5℃时，ts7的血凝素（HA）以未切割的形式在细胞表面表达。还发现，用野生型B/Lee株的第6节段RNA替换ts7的第6节段RNA，会在37.5℃的孵育温度下产生低pH诱导的融合活性以及NA酶活性，并且在感染早期将细菌NA添加到在37.5℃感染ts7的培养物中会导致低pH诱导的细胞融合。我们认为，NA从HA的碳水化合物部分去除神经氨酸对于细胞蛋白酶切割HA至关重要。
