Protein Domains Involved in Assembly in the Endoplasmic Reticulum Promote Vacuolar Delivery when Fused to Secretory GFP, Indicating a Protein Quality Control Pathway for Degradation in the Plant Vacuole
Protein Domains Involved in Assembly in the Endoplasmic Reticulum Promote Vacuolar Delivery when Fused to Secretory GFP, Indicating a Protein Quality Control Pathway for Degradation in the Plant Vacuole
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DOI：
10.1093/mp/ssn066
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发表时间：
2008-11-01
期刊：
影响因子：
27.5
通讯作者：
Vitale, Alessandro
中科院分区：
文献类型：
--
作者：
Foresti, Ombretta;De Marchis, Francesca;Vitale, Alessandro
新合成的分泌蛋白的正确折叠和组装由内质网（ER）的蛋白质质量控制系统监测。通过与伴侣蛋白如结合蛋白（BiP）和其他折叠助手的相互作用，质量控制有利于生产性折叠和降解缺陷蛋白的分类。在酵母、植物和动物中鉴定的质量控制降解的主要途径是由从ER到胞质溶胶的逆易位和随后由泛素/蛋白酶体系统的处置构成，但在酵母中已鉴定出涉及液泡的替代途径。在这项研究中，我们研究了sGFP 418的命运，GFP的分泌形式和空泡蛋白菜豆蛋白的结构域之间的融合，参与菜豆蛋白的正确组装和未组装亚基的BiP识别。我们发现，sGFP 418，尽管缺乏菜豆蛋白空泡分选信号，交付到空泡和破碎，在一个过程中，被抑制的分泌交通抑制剂布雷菲德菌素A。此外，GFP与玉米贮藏蛋白γ-玉米醇溶蛋白的参与玉米醇溶蛋白聚合的结构域之间的融合也经历类似于sGFP 418的翻译后片段化。这些结果表明，有缺陷的分泌蛋白质与永久暴露的序列通常参与寡聚化可以交付到液泡的分泌交通。这有力地表明存在一种植物液泡分选机制，专门用于处理有缺陷的分泌蛋白。
The correct folding and assembly of newly synthesized secretory proteins are monitored by the protein quality control system of the endoplasmic reticulum (ER). Through interactions with chaperones such as the binding protein (BiP) and other folding helpers, quality control favors productive folding and sorts for degradation defective proteins. A major route for quality control degradation identified in yeast, plants, and animals is constituted by retrotranslocation from the ER to the cytosol and subsequent disposal by the ubiquitin/proteasome system, but alternative routes involving the vacuole have been identified in yeast. In this study, we have studied the destiny of sGFP418, a fusion between a secretory form of GFP and a domain of the vacuolar protein phaseolin that is involved in the correct assembly of phaseolin and in BiP recognition of unassembled subunits. We show that sGFP418, despite lacking the phaseolin vacuolar sorting signal, is delivered to the vacuole and fragmented, in a process that is inhibited by the secretory traffic inhibitor brefeldin A. Moreover, a fusion between GFP and a domain of the maize storage protein gamma-zein involved in zein polymerization also undergoes post-translational fragmentation similar to that of sGFP418. These results show that defective secretory proteins with permanently exposed sequences normally involved in oligomerization can be delivered to the vacuole by secretory traffic. This strongly suggests the existence of a plant vacuolar sorting mechanism devoted to the disposal of defective secretory proteins.