Role of disulfide bridges formed in the luminal domain of ATF6 in sensing endoplasmic reticulum stress
Role of disulfide bridges formed in the luminal domain of ATF6 in sensing endoplasmic reticulum stress
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DOI：
10.1128/mcb.00408-06
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发表时间：
2007-02-01
影响因子：
5.3
通讯作者：
Mori, Kazutoshi
中科院分区：
文献类型：
--
作者：
Nadanaka, Satomi;Okada, Tetsuya;Mori, Kazutoshi
ATF6是一种膜结合转录因子，在内质网（ER）应激时通过蛋白水解作用被激活，以诱导内质网伴侣基因的转录。我们在此表明，由于在腔结构域中两个保守的半胱氨酸残基之间形成了分子内和分子间二硫键，ATF6在未受应激的内质网中以单体、二聚体和寡聚体形式存在。用还原剂二硫苏糖醇以及糖基化抑制剂衣霉素处理细胞时，二硫键连接的ATF6会被还原，并且还原程度与激活程度相关。尽管还原对于激活是不够的，但分级分离研究表明，只有还原的单体ATF6能够到达高尔基体，在那里它被两种蛋白酶S1P和S2P依次作用而切割。发现还原的单体ATF6是比二硫键连接形式更好的S1P底物。内质网应激诱导的还原对ATF6是特异的，因为第二种内质网膜结合转录因子LZIP/Luman的寡聚状态在衣霉素处理时没有改变，并且LZIP/Luman在没有内质网应激的情况下也能被S1P很好地切割。这种机制确保了调节的严格性，即细胞只能处理经历了内质网变化的ATF6。
ATF6 is a membrane-bound transcription factor activated by proteolysis in response to endoplasmic reticulum (ER) stress to induce the transcription of ER chaperone genes. We show here that, owing to the presence of intra- and intermolecular disulfide bridges formed between the two conserved cysteine residues in the luminal domain, ATF6 occurs in unstressed ER in monomer, dimer, and oligomer forms. Disulfide-bonded ATF6 is reduced upon treatment of cells with not only the reducing reagent dithiothreitol but also the glycosylation inhibitor tunicamycin, and the extent of reduction correlates with that of activation. Although reduction is not sufficient for activation, fractionation studies show that only reduced monomer ATF6 reaches the Golgi apparatus, where it is cleaved by the sequential action of the two proteases S1P and S2P. Reduced monomer ATF6 is found to be a better substrate than disulfide-bonded forms for S1P. ER stress-induced reduction is specific to ATF6 as the oligomeric status of a second ER membrane-bound transcription factor, LZIP/Luman, is not changed upon tunicamycin treatment and LZIP/Luman is well cleaved by S1P in the absence of ER stress. This mechanism ensures the strictness of regulation, in that the cell can only process ATF6 which has experienced the changes in the ER.