Sec61 channel subunit Sbh1/Sec61β promotes ER translocation of proteins with suboptimal targeting sequences and is fine-tuned by phosphorylation.
Sec61 channel subunit Sbh1/Sec61β promotes ER translocation of proteins with suboptimal targeting sequences and is fine-tuned by phosphorylation.
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DOI：
10.1016/j.jbc.2023.102895
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发表时间：
2023-03
影响因子：
4.8
通讯作者：
Roemisch, Karin
中科院分区：
文献类型：
--
作者：
Barbieri, Guido;Simon, Julien;Lupusella, Cristina R.;Pereira, Fabio;Elia, Francesco;Meyer, Hadar;Schuldiner, Maya;Hanes, Steven D.;Nguyen, Duy;Helms, Volkhard;Roemisch, Karin
高度保守的内质网（endoplasmic reticulum，ER）蛋白转运通道含有一个非必需亚基Sec 61 β/Sbh 1，其功能目前尚不清楚。其本质上非结构化的胞质结构域与胞质通道前庭中的ER靶向序列短暂接触，并含有多个磷酸化位点，这表明调节ER蛋白输入的潜力。在一个显微镜屏幕上，我们发现，12%的GFP标记的分泌蛋白库依赖于Sbh 1易位到ER。Sbh 1依赖性蛋白质的靶向序列具有不太明显的疏水性，并且通常没有电荷偏倚或反向电荷偏倚，这降低了它们插入Sec 61通道的效率。我们确定，突变的两个N-末端，脯氨酸侧翼的磷酸化位点在SbH 1胞质结构域丙氨酸phenocopied的温度敏感性的酵母菌株缺乏SBH 1和它的直系同源SBH 2。磷酸化位点突变减少了Sbh 1依赖性蛋白亚组转运到ER中，包括ER腔中浓度对ER蛋白稳态至关重要的酶。此外，我们发现这些蛋白质的ER输入依赖于磷酸-S/T-特异性脯氨酸异构酶PIN 1（哺乳动物中的PIN 1）的活性。我们的结论是，Sbh 1促进ER易位的基板与次优的靶向序列，其活性可以调节由N-末端磷酸化诱导的构象变化。
The highly conserved endoplasmic reticulum (ER) protein translocation channel contains one nonessential subunit, Sec61β/Sbh1, whose function is poorly understood so far. Its intrinsically unstructured cytosolic domain makes transient contact with ER-targeting sequences in the cytosolic channel vestibule and contains multiple phosphorylation sites suggesting a potential for regulating ER protein import. In a microscopic screen, we show that 12% of a GFP-tagged secretory protein library depends on Sbh1 for translocation into the ER. Sbh1-dependent proteins had targeting sequences with less pronounced hydrophobicity and often no charge bias or an inverse charge bias which reduces their insertion efficiency into the Sec61 channel. We determined that mutating two N-terminal, proline-flanked phosphorylation sites in the Sbh1 cytosolic domain to alanine phenocopied the temperature-sensitivity of a yeast strain lacking SBH1 and its ortholog SBH2. The phosphorylation site mutations reduced translocation into the ER of a subset of Sbh1-dependent proteins, including enzymes whose concentration in the ER lumen is critical for ER proteostasis. In addition, we found that ER import of these proteins depended on the activity of the phospho-S/T–specific proline isomerase Ess1 (PIN1 in mammals). We conclude that Sbh1 promotes ER translocation of substrates with suboptimal targeting sequences and that its activity can be regulated by a conformational change induced by N-terminal phosphorylation.
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DOI：
10.1016/j.bbagrm.2014.02.001
发表时间：
2014
影响因子：
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作者：
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2014-03-20
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影响因子：
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2008-07-28
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