Cytosolic N-terminal arginine-based signals together with a luminal signal target a type II membrane protein to the plant ER
Cytosolic N-terminal arginine-based signals together with a luminal signal target a type II membrane protein to the plant ER
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DOI：
10.1186/1471-2229-9-144
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发表时间：
2009-12-08
影响因子：
5.3
通讯作者：
Gomord, Veronique
中科院分区：
文献类型：
--
作者：
Boulaflous, Aurelia;Saint-Jore-Dupas, Claude;Gomord, Veronique
背景资料：在真核细胞中，脂质和蛋白质的恒定流动穿过构成胞外途径的膜隔室。这对于内质网（ER）尤其如此，内质网是主要的“分泌途径的门户”，在内质网中发生固醇、脂质、膜结合蛋白和可溶性蛋白以及糖蛋白的生物合成。在该隔室中的驻留蛋白质的维持意味着它们必须与分泌性货物区分开。为此，它们必须具有特定的ER定位决定子，以防止它们从ER中退出，和/或与负责从高尔基体中检索它们的受体相互作用。非常少的信息是有关的信号（S）参与在ER中的膜II型蛋白质的保留，但人们普遍认为，ER II型货物膜蛋白的分选主要取决于位于其cytosolic tails.Results：在这里，使用拟南芥葡萄糖苷酶I作为模型，我们已经确定了两种类型的信号足以在ER中的II型膜蛋白的位置。第一个信号位于管腔结构域中，而第二个信号对应于位于膜蛋白的胞质尾部中的短氨基酸序列。胞质尾部在其N-末端含有四个精氨酸残基，其由三个二精氨酸基序（RR、RXR或RXXR）组成，独立地足以赋予ER定位。有趣的是，当只有一个二精氨酸基序存在时，融合蛋白位于ER和移动的点状结构中，不同但靠近高尔基体。可溶性和膜ER蛋白标记物被排除在这些点状结构之外，其也不与ER出口位点标记物共定位。据推测，他们对应的网站参与高尔基体ER retrotransport.Conclusion：总而言之，这些结果清楚地表明，负责ER保留的胞质和管腔信号可以共存于同一个II型膜蛋白。这些数据还表明，检索和保留机制支配蛋白质驻留在ER膜。我们假设，移动的点状结构尚未描述在ER/高尔基体接口，暂时命名为GERES，可能参与检索机制从高尔基体的ER。
Background: In eukaryotic cells, the membrane compartments that constitute the exocytic pathway are traversed by a constant flow of lipids and proteins. This is particularly true for the endoplasmic reticulum ( ER), the main "gateway of the secretory pathway", where biosynthesis of sterols, lipids, membrane-bound and soluble proteins, and glycoproteins occurs. Maintenance of the resident proteins in this compartment implies they have to be distinguished from the secretory cargo. To this end, they must possess specific ER localization determinants to prevent their exit from the ER, and/or to interact with receptors responsible for their retrieval from the Golgi apparatus. Very few information is available about the signal(s) involved in the retention of membrane type II protein in the ER but it is generally accepted that sorting of ER type II cargo membrane proteins depends on motifs mainly located in their cytosolic tails.Results: Here, using Arabidopsis glucosidase I as a model, we have identified two types of signals sufficient for the location of a type II membrane protein in the ER. A first signal is located in the luminal domain, while a second signal corresponds to a short amino acid sequence located in the cytosolic tail of the membrane protein. The cytosolic tail contains at its N-terminal end four arginine residues constitutive of three di-arginine motifs (RR, RXR or RXXR) independently sufficient to confer ER localization. Interestingly, when only one di-arginine motif is present, fusion proteins are located both in the ER and in mobile punctate structures, distinct but close to Golgi bodies. Soluble and membrane ER protein markers are excluded from these punctate structures, which also do not colocalize with an ER-exit-site marker. It is hypothesized they correspond to sites involved in Golgi to ER retrotransport.Conclusion: Altogether, these results clearly show that cytosolic and luminal signals responsible for ER retention could coexist in a same type II membrane protein. These data also suggest that both retrieval and retention mechanisms govern protein residency in the ER membrane. We hypothesized that mobile punctate structures not yet described at the ER/Golgi interface and tentatively named GERES, could be involved in retrieval mechanisms from the Golgi to the ER.