INVOLVEMENT OF THE MOLECULAR CHAPERONE BIP IN MATURATION OF SINDBIS-VIRUS ENVELOPE GLYCOPROTEINS
INVOLVEMENT OF THE MOLECULAR CHAPERONE BIP IN MATURATION OF SINDBIS-VIRUS ENVELOPE GLYCOPROTEINS
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DOI：
10.1128/jvi.69.3.1621-1627.1995
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发表时间：
1995-03-01
影响因子：
5.4
通讯作者：
BROWN, DT
中科院分区：
文献类型：
--
作者：
MULVEY, M;BROWN, DT
Sindbis病毒编码两种膜糖蛋白E1和PE2，它们在内质网内组装成异源二聚体。我们研究了分子伴侣BiP （grp78）在这两种蛋白成熟过程中的作用。E1通过至少三个不同二硫键构型的中间体折叠成其成熟的构象，在合成后被发现与BiP发生强烈而短暂的相互作用，羰基氰化物间氯苯腙处理介导的ATP消耗导致BiP和E1之间的配合物稳定。细胞内ATP水平的消耗也极大地抑制了E1折叠中间体之间的转化，并导致E1缓慢地并入二硫稳定的聚集体。这些结果表明，ATP调节BiP的结合和释放在E1折叠过程中具有调节二硫键形成的作用。与E1相比，与BiP相关的PE2通常很少恢复。然而，在E1折叠异常的条件下，增加的PE2数量与BiP直接相关，这些BiP-PE2相互作用的形成发生在E1开始错误折叠或不能有效折叠之后。我们认为新生的PE2在与E1配对之前只有有限的一段时间是稳定的，之后未配对的PE2就会被BiP识别。这意味着PE2和E1的有效结合必须发生在有限的时间框架内，并且只有在E1完成了由BiP结合和释放介导的某些折叠步骤之后。动力学研究表明，易位后E1与PE2的配对延迟，支持了这一结论。
Sindbis virus codes for two membrane glycoproteins, E1 and PE2, which assemble into heterodimers within the endoplasmic reticulum. We have examined the role of the molecular chaperone BiP (grp78) in the maturation of these two proteins. E1, which folds into its mature conformation via at least three intermediates differing in the configurations of their disulfide bonds, was found to interact strongly and transiently with BiP after synthesis, ATP depletion mediated by carbonyl cyanide m-chlorophenylhydrazone treatment results in the stabilization of complexes between BiP and E1. The depletion of intracellular ATP levels also greatly inhibits conversions between the E1 folding intermediates and results in the slow incorporation of E1 into disulfide-stabilized aggregates. These results suggest that the ATP regulated binding and release of BiP have a role in modulating disulfide bond formation during E1 folding. in comparison with E1, very little PE2 is normally recovered in association with BiP. However, under conditions in which E1 folding is aberrant, increased amounts of PE2 become directly associated with BiP, The formation of these BiP-PE2 interactions occurs after E1 begins to misfold or fails to fold efficiently. We propose that nascent PE2 is stable prior to pairing with E1 for only a limited period of time, after which unpaired PE2 becomes recognized by BiP. This implies that the productive association of PE2 and E1 must occur within a restricted time frame and only after E1 has accomplished certain folding steps mediated by BiP binding and release. Kinetic studies which show that the pairing of E1 with PE2 is delayed after translocation support this conclusion.