Endoplasmic reticulum retention, degradation, and aggregation of olfactory G-protein coupled receptors
Endoplasmic reticulum retention, degradation, and aggregation of olfactory G-protein coupled receptors
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DOI：
10.1034/j.1600-0854.2003.00097.x
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发表时间：
2003-06-01
期刊：
影响因子：
4.5
通讯作者：
Moyer, BD
中科院分区：
文献类型：
--
作者：
Lu, M;Echeverri, F;Moyer, BD
哺乳动物嗅觉g蛋白偶联受体家族由数百种蛋白质组成，这些蛋白质介导气味结合并启动导致嗅觉的信号转导级联反应。然而，在异源系统中，嗅觉受体表面表达不佳严重阻碍了功能性表达嗅觉受体和识别特定气味配体-嗅觉受体相互作用的努力。因此，我们进行了实验来阐明嗅觉受体细胞表面表达效率低下的细胞机制。我们确定小鼠气味受体mI7和mOREG没有选择从内质网输出，因此在高尔基体或质膜上无法检测到。具体来说，嗅觉受体与内质网伴侣钙连联素相互作用，被排除在内质网输出位点之外，在15度的内质网高尔基转运中间体中不积累，并且含有内糖苷酶h敏感的低聚糖，这与嗅觉受体被排除在内质网后腔室中一致。一个不稳定的er保留嗅觉受体池被翻译后的多泛素化修饰，并被蛋白酶体降解。此外，嗅觉受体被隔离在内质网聚集体中，内质网聚集体被自噬降解。综上所述，这些数据表明，异源细胞中嗅觉受体的表面表达不佳是由于低效率折叠导致的内质网保留，以及通过蛋白酶体和自噬途径与内质网输出机制、聚集和降解的耦合不良。
The mammalian olfactory G-protein coupled receptor family is comprised of hundreds of proteins that mediate odorant binding and initiate signal transduction cascades leading to the sensation of smell. However, efforts to functionally express olfactory receptors and identify specific odorant ligand-olfactory receptor interactions have been severely impeded by poor olfactory receptor surface expression in heterologous systems. Therefore, experiments were performed to elucidate the cellular mechanism(s) responsible for inefficient olfactory receptor cell surface expression. We determined that the mouse odorant receptors mI7 and mOREG are not selected for export from the ER and therefore are not detectable at the Golgi apparatus or plasma membrane. Specifically, olfactory receptors interact with the ER chaperone calnexin, are excluded from ER export sites, do not accumulate in ER-Golgi transport intermediates at 15degreesC, and contain endoglycosidase H-sensitive oligosaccharides, consistent with olfactory receptor exclusion from post-ER compartments. A labile pool of ER-retained olfactory receptors are post-translationally modified by polyubiquitination and targeted for degradation by the proteasome. In addition, olfactory receptors are sequestered into ER aggregates that are degraded by autophagy. Collectively, these data demonstrate that poor surface expression of olfactory receptors in heterologous cells is attributable to a combination of ER retention due to inefficient folding and poor coupling to ER export machinery, aggregation, and degradation via both proteasomal and autophagic pathways.