Luminal/extracellular domains of chimeric CI-M6PR-C proteins interfere with their retrograde endosome-to-TGN trafficking in the transient expression system.
Luminal/extracellular domains of chimeric CI-M6PR-C proteins interfere with their retrograde endosome-to-TGN trafficking in the transient expression system.
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嵌合 CI-M6PR-C 蛋白的管腔/胞外结构域干扰瞬时表达系统中的逆行内体到 TGN 的运输
DOI：
10.7555/jbr.32.20180044
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发表时间：
2018-07-23
影响因子：
2.3
通讯作者：
Liu Y
中科院分区：
文献类型：
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作者：
Chang F;Li N;Yan K;Huang Y;Xu H;Liu Y
阳离子非依赖性甘露糖6-磷酸受体（CI-M6 PR）在反式高尔基体网络（TGN）和内体区室之间的膜运输不仅对于维持溶酶体功能至关重要，而且对于理解逆行内体至TGN运输中的分子和细胞机制也是众所周知的事件。尽管在文献中已经很好地确定牛CI-M6 PR的C-末端决定其逆行运输，但仍不清楚蛋白质的管腔结构域是否在这些分选事件中起作用。在这项研究中，我们发现人CI-M6 PR的管腔结构域的部分缺失将突变蛋白错误定位到非TGN区室。此外，用来自不相关的膜蛋白如CD 8或Tac的管腔结构域替换牛和人CI-M6 PR的管腔结构域也改变了嵌合蛋白的TGN靶向。另一方面，与受体的跨膜结构域和C末端融合的来自HA的仅短序列HA-hCI-M6 PR-尾导致其与全长受体一样优先靶向TGN，强烈表明受体的分选可能受管腔序列的影响。此外，使用这种管腔截短形式的HA-hCI-M6 PR作为模型货物，我们发现嵌合蛋白的运输通过逆转录复合物通过与SNX 5相互作用来调节。总之，我们的研究强烈表明，来自hCI-M6 PR或其他不相关的膜蛋白的破坏的管腔结构域干扰CI-M6 PR的膜运输和TGN靶向的过程。
The membrane trafficking of cation-independent mannose 6-phosphate receptor (CI-M6PR) between the trans-Golgi network (TGN) and endosomal compartments is not only critical for maintaining lysosomal function but also a well-known event for understanding molecular and cellular mechanisms in retrograde endosome-to-TGN trafficking. Although it has been well established in literature that the C-terminus of bovine CI-M6PR determines its retrograde trafficking, it remains unclear whether the luminal domain of the protein plays a role on these sorting events. In this study, we found that partial deletion of luminal domain of human CI-M6PR mistargeted the mutant protein to non-TGN compartments. Moreover, replacing the luminal domain of both bovine and human CI-M6PR with that from irrelevant membrane proteins such as CD8 or Tac also altered the TGN targeting of the chimeric proteins. On the other hand, only short sequence from HA fused with the transmembrane domain and C-terminus of the receptor, HA-hCI-M6PR-tail, resulted in its preferential targeting to TGN as for the full length receptor, strongly suggesting that sorting of the receptor may be influenced by luminal sequence. Furthermore, using this luminal truncated form of HA-hCI-M6PR as a model cargo, we found that the trafficking of the chimeric protein was regulated by the retromer complex through interacting with SNX5. In conclusion, our study strongly suggested that the disrupted luminal domain from hCI-M6PR or other irrelevant membrane proteins interfere with the process of membrane trafficking and TGN targeting of CI-M6PR.