Endoplasmic reticulum-resident proteins are constitutively transported to vacuoles for degradation.
Endoplasmic reticulum-resident proteins are constitutively transported to vacuoles for degradation.
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DOI：
10.1111/j.1365-313x.2004.02141.x
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发表时间：
2004-08
期刊：
影响因子：
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通讯作者：
K. Tamura;Kenji Yamada;T. Shimada;I. Hara-Nishimura
中科院分区：
文献类型：
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作者：
K. Tamura;Kenji Yamada;T. Shimada;I. Hara-Nishimura
可溶性内质网（ER）驻留蛋白由于其ER驻留而具有非常长的寿命。这种驻留在很大程度上取决于ER-检索信号在其C-末端。我们研究了长期命运的内源性ER居民蛋白，内腔结合蛋白（BiP）和蛋白质二硫键异构酶（PDI），与培养的细胞拟南芥。内质网居民，在相反的空泡蛋白酶，在细胞中的稳定期大大降低。亚细胞分离分析表明，ER居民被运送到空泡，积累居民缺乏ER检索信号。我们发现位于液泡中的PDI具有高甘露糖聚糖，但不具有复合聚糖，这表明ER驻留物独立于内侧/trans-Golgi复合物被转运到液泡中。为了可视化ER驻留蛋白的转运途径，用编码ER靶向绿色荧光蛋白（30 kDa GFP-HDEL）的嵌合基因转化烟草BY-2细胞。在稳定期的转化细胞中，在空泡中观察到GFP荧光。亚细胞分级显示，修剪形式的27 kDa的GFP定位在液泡。用E-64 d（抑制液泡中GFP降解的木瓜蛋白酶型半胱氨酸蛋白酶的抑制剂）处理导致液泡中27 kDa GFP的稳定积累，即使在对数期也是如此。我们的研究结果表明，内源性ER居民运输组成的液泡绕过高尔基复合体，然后降解。
Soluble endoplasmic reticulum (ER)-resident proteins have very long lives because of their ER residency. This residency depends largely on ER-retrieval signals at their C-terminus. We examined the long-term destiny of endogenous ER-resident proteins, a lumenal binding protein (BiP) and a protein disulfide isomerase (PDI), with cultured cells of Arabidopsis. ER residents, in contrast to vacuolar proteinases, were considerably degraded in cells at the stationary phase. A subcellular fractionation analysis suggested that ER residents were transported into the vacuoles, which accumulated the residents lacking the ER-retrieval signals. We showed that the PDI located in the vacuoles had high mannose glycans, but not complex glycans, which suggested that the ER resident was transported to the vacuoles independent of the medial/trans-Golgi complex. To visualize the pathway of transport of ER-resident proteins, tobacco BY-2 cells were transformed with a chimeric gene encoding an ER-targeted green fluorescent protein (30 kDa GFP-HDEL). In the transformed cells at the stationary phase, GFP fluorescence was observed in the vacuoles. A subcellular fractionation revealed that a trimmed form of 27 kDa GFP was localized in the vacuoles. Treatment with E-64d, an inhibitor of papain-type cysteine proteinases that inhibits the degradation of GFP in the vacuoles, resulted in a stable accumulation of 27 kDa GFP in the vacuoles, even in the logarithmic phase. Our results suggest that endogenous ER residents are transported constitutively to the vacuoles by bypassing the Golgi complex and are then degraded.