Analysis and function of prototype foamy virus envelope N glycosylation
Analysis and function of prototype foamy virus envelope N glycosylation
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DOI：
10.1128/jvi.79.12.7664-7672.2005
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发表时间：
2005-06-01
影响因子：
5.4
通讯作者：
Lindemann, D
中科院分区：
文献类型：
--
作者：
Lüftenegger, D;Picard-Maureau, M;Lindemann, D
原型泡沫病毒（PFV）糖蛋白是PFV颗粒释放所必需的，其显示出高度不寻常的生物合成，导致前体蛋白翻译后切割成三个颗粒相关亚基，即，前导肽（LP）、表面肽（SU）和跨膜肽（TM）。糖苷酶消化代谢标记的PFV颗粒显示N-连接的碳水化合物的存在下，所有的亚基。对特定糖苷酶的差异敏感性表明，LP和TM上的所有寡糖都是高甘露糖或杂交型的，而大多数与SU相连的寡糖（占其分子量的约50%）是复合型的。PFV Env中所有15个潜在N-糖基化位点的单独失活证明使用了14个，即，LP为1/2，SU为10，TM为3。个别改变的糖蛋白的分析显示缺陷的细胞内加工，支持颗粒释放，和感染性的三个突变体，具有进化上保守的糖基化位点N8在SU或N13和N15中的半胱氨酸丰富的中央“片和环”区域的TM失活。在这些位点上具有影响糖基化或周围序列的突变的替代突变体的检查表明，N8和N13处的糖基化抑制最有可能是观察到的复制缺陷的原因，而N15周围序列似乎有助于温度敏感型。总之，这些数据表明，PFV Env，特别是SU亚基是严重的N糖基化，并表明，虽然大多数碳水化合物是单独的，一些进化上保守的网站是重要的正常Env功能的FV分离株从不同的物种。
The prototype foamy virus (PFV) glycoprotein, which is essential for PFV particle release, displays a highly unusual biosynthesis, resulting in posttranslational cleavage of the precursor protein into three particle-associated subunits, i.e., leader peptide (LP), surface (SU), and transmembrane (TM). Glycosidase digestion of metabolically labeled PFV particles revealed the presence of N-linked carbohydrates on all subunits. The differential sensitivity to specific glycosidases indicated that all oligosaccharides on LP and TM are of the high-mannose or hybrid type, whereas most of those attached to SU, which contribute to about 50% of its molecular weight, are of the complex type. Individual inactivation of all 15 potential N-glycosylation sites in PFV Env demonstrated that 14 are used, i.e., 1 out of 2 in LP, 10 in SU, and 3 in TM. Analysis of the individual altered glycoproteins revealed defects in intracellular processing, support of particle release, and infectivity for three mutants, having the evolutionarily conserved glycosylation sites N8 in SU or N13 and N15 in the cysteine-rich central "sheets-and-loops" region of TM inactivated. Examination of alternative mutants with mutations affecting glycosylation or surrounding sequences at these sites indicated that inhibition of glycosylation at N8 and N13 most likely is responsible for the observed replication defects, whereas for N15 surrounding sequences seem to contribute to a temperature-sensitive phenotype. Taken together these data demonstrate that PFV Env and in particular the SU subunit are heavily N glycosylated and suggest that although most carbohydrates are dispensable individually, some evolutionarily conserved sites are important for normal Env function of FV isolates from different species.