Inhibition of Protein Synthesis by TOR Inactivation Revealed a Conserved Regulatory Mechanism of the BiP Chaperone in Chlamydomonas
Inhibition of Protein Synthesis by TOR Inactivation Revealed a Conserved Regulatory Mechanism of the BiP Chaperone in Chlamydomonas
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DOI：
10.1104/pp.111.179861
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发表时间：
2011-10-01
期刊：
影响因子：
7.4
通讯作者：
Crespo, Jose L.
中科院分区：
文献类型：
--
作者：
Diaz-Troya, Sandra;Esther Perez-Perez, Maria;Crespo, Jose L.
雷帕霉素（TOR）激酶的靶标整合营养和应激信号以协调控制所有真核生物中的细胞生长。TOR与高度保守的蛋白质结合，构成两种不同的信号复合物，称为TORC 1和TORC 2。在大多数真核生物中，雷帕霉素对TORC 1的失活负调节蛋白质合成。在这里，我们报告说，下调TOR信号的雷帕霉素在模型绿色衣藻莱因哈德导致明显的磷酸化内质网伴侣BiP。我们的研究结果表明，衣原体TOR通过控制蛋白质合成来调节BiP磷酸化，因为雷帕霉素和放线菌酮对BiP修饰和蛋白质合成抑制具有相似的作用。在需要BiP伴侣活性的条件下，例如热休克应激或衣霉素处理，磷酸化对BiP的修饰被抑制，从而抑制内质网中新生蛋白质的N-连接糖基化。在用雷帕霉素处理的衣原体细胞中鉴定了位于BiP的底物结合结构域中的磷酸肽。该肽含有一个高度保守的苏氨酸残基，可以调节BiP功能，如酵母功能测定所示。因此，我们的研究揭示了衣原体中BiP通过磷酸化/去磷酸化事件的调节机制，并在BiP修饰的控制中分配了TOR通路的作用。
The target of rapamycin (TOR) kinase integrates nutritional and stress signals to coordinately control cell growth in all eukaryotes. TOR associates with highly conserved proteins to constitute two distinct signaling complexes termed TORC1 and TORC2. Inactivation of TORC1 by rapamycin negatively regulates protein synthesis in most eukaryotes. Here, we report that down-regulation of TOR signaling by rapamycin in the model green alga Chlamydomonas reinhardtii resulted in pronounced phosphorylation of the endoplasmic reticulum chaperone BiP. Our results indicated that Chlamydomonas TOR regulates BiP phosphorylation through the control of protein synthesis, since rapamycin and cycloheximide have similar effects on BiP modification and protein synthesis inhibition. Modification of BiP by phosphorylation was suppressed under conditions that require the chaperone activity of BiP, such as heat shock stress or tunicamycin treatment, which inhibits N-linked glycosylation of nascent proteins in the endoplasmic reticulum. A phosphopeptide localized in the substrate-binding domain of BiP was identified in Chlamydomonas cells treated with rapamycin. This peptide contains a highly conserved threonine residue that might regulate BiP function, as demonstrated by yeast functional assays. Thus, our study has revealed a regulatory mechanism of BiP in Chlamydomonas by phosphorylation/dephosphorylation events and assigns a role to the TOR pathway in the control of BiP modification.