Targeting of the plant vacuolar sorting receptor BP80 is dependent on multiple sorting signals in the cytosolic tail
Targeting of the plant vacuolar sorting receptor BP80 is dependent on multiple sorting signals in the cytosolic tail
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DOI：
10.1105/tpc.105.040394
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发表时间：
2006-06-01
期刊：
影响因子：
11.6
通讯作者：
Denecke, Jurgen
中科院分区：
文献类型：
--
作者：
daSilva, Luis L. P.;Foresti, Ombretta;Denecke, Jurgen
虽然可溶性蛋白的液泡分选信号已经被很好地描述，但我们还没有了解植物液泡分选受体BP80如何到达其正确的目的地并进行循环。为了阐明受体靶向，我们使用了一种体内竞争实验，其中截断的受体（绿色荧光蛋白- bp80）特异性地与分选机制竞争，并导致烟草（Nicotiana tabacum）叶原生质体中bp80配体的高分泌。我们发现，BP80的跨膜结构域和胞质尾部都包含有效进展到泡前室（PVC）所需的信息。此外，尾巴必须暴露在正确的膜表面，以与分拣机械竞争。保守残基的突变分析表明，竞争需要多个序列基序，其中一个是典型的tyr基序（YXX Phi）。Tyr-612取代Ala会导致部分滞留在高尔基体中，错误靶向质膜（PM），并减缓向PVC的进展。通过在全长BP80上产生相应的突变，证实了其在高尔基向pvc转运中的作用。突变受体被部分错定位于PM，并诱导分泌一种共表达的bp80配体。进一步的突变表明，细胞质尾部可能包含除了YXXF基序之外的其他信息，可能用于内质网输出，PM的内吞作用以及pvc到高尔基体的再循环。
Although signals for vacuolar sorting of soluble proteins are well described, we have yet to learn how the plant vacuolar sorting receptor BP80 reaches its correct destination and recycles. To shed light on receptor targeting, we used an in vivo competition assay in which a truncated receptor (green fluorescent protein-BP80) specifically competes with sorting machinery and causes hypersecretion of BP80-ligands from tobacco (Nicotiana tabacum) leaf protoplasts. We show that both the transmembrane domain and the cytosolic tail of BP80 contain information necessary for efficient progress to the prevacuolar compartment (PVC). Furthermore, the tail must be exposed on the correct membrane surface to compete with sorting machinery. Mutational analysis of conserved residues revealed that multiple sequence motifs are necessary for competition, one of which is a typical Tyr-based motif (YXX Phi). Substitution of Tyr-612 for Ala causes partial retention in the Golgi apparatus, mistargeting to the plasma membrane ( PM), and slower progress to the PVC. A role in Golgi-to-PVC transport was confirmed by generating the corresponding mutation on full-length BP80. The mutant receptor was partially mistargeted to the PM and induced the secretion of a coexpressed BP80-ligand. Further mutants indicate that the cytosolic tail is likely to contain other information besides the YXXF motif, possibly for endoplasmic reticulum export, endocytosis from the PM, and PVC-to-Golgi recycling.