Hanton Sally L, Renna Luciana, Bortolotti Lauren E, Chatre Laurent, Stefano Giovanni, Brandizzi Federica
Department of Biology, University of Saskatchewan, Saskatoon SK S7N 5E2, Saskatchewan, Canada.
Plant Cell. 2005 Nov;17(11):3081-93. doi: 10.1105/tpc.105.034900. Epub 2005 Oct 7.
In yeast and mammals, amino acid motifs in the cytosolic tails of transmembrane domains play a role in protein trafficking by facilitating export from the endoplasmic reticulum (ER). However, little is known about ER export signals of membrane proteins in plants. Therefore, we investigated the role of diacidic motifs in the ER export of Golgi-localized membrane proteins. We show that diacidic motifs perform a significant function in the export of transmembrane proteins to the Golgi apparatus, as mutations of these signals impede the efficient anterograde transport of multispanning, type II, and type I proteins. Furthermore, we demonstrate that diacidic motifs instigate the export of proteins that reside in the ER due to the lengths of their transmembrane domains. However, not all of the diacidic motifs in the cytosolic tails of the proteins studied were equally important in ER export. Transport of Golgi proteins was disrupted only by mutagenesis of specific diacidic signals, suggesting that the protein environment of these signals affects their function. Our findings indicate that diacidic ER export motifs are present and functional in plant membrane proteins and that they are dominant over transmembrane domain length in determining the export of proteins from the ER in plant cells.
在酵母和哺乳动物中，跨膜结构域胞质尾中的氨基酸基序通过促进从内质网（ER）输出，在蛋白质运输中发挥作用。然而，对于植物中膜蛋白的内质网输出信号了解甚少。因此，我们研究了双酸性基序在高尔基体定位膜蛋白的内质网输出中的作用。我们发现双酸性基序在跨膜蛋白向高尔基体的输出中发挥着重要作用，因为这些信号的突变会阻碍多跨膜、II型和I型蛋白的有效顺向运输。此外，我们证明双酸性基序促使因跨膜结构域长度而滞留在内质网中的蛋白输出。然而，所研究蛋白胞质尾中的并非所有双酸性基序在内质网输出中都同等重要。高尔基体蛋白的运输仅通过特定双酸性信号的诱变而受到干扰，这表明这些信号的蛋白质环境会影响其功能。我们的研究结果表明，双酸性内质网输出基序存在于植物膜蛋白中并发挥作用，并且在决定植物细胞中蛋白质从内质网输出方面，它们比跨膜结构域长度更具主导性。
