Plant Physiol|曲乐庆研究组揭示OsFes1C 是 OsBiP1的潜在核苷酸交换因子，参与了水稻内质网和盐胁迫反应

内质网（ER）质量控制（ERQC）系统监测蛋白质稳态，并依赖于许多分子伴侣的活性。结合免疫球蛋白（BiP）是一种主要的内腔伴侣蛋白，参与细胞器的大部分功能。BiP活性受核苷酸交换因子（NEFs）的严格调控。然而，关于植物中NEFs的信息是有限的。通过对内质网胁迫下的水稻（Oryza sativa）种子进行基于iTRAQ的蛋白质组学分析，获得了类Fes1蛋白（OsFes1C）。与酵母和哺乳动物中的同源物不同，OsFes1C位于细胞质中，对热应激有反应，它是一种内质网膜蛋白，对内质网和盐胁迫有反应。OsFes1C直接与OsBiP1相互作用，这种相互作用被ATP抑制而被ADP促进，提示OsFes1C在体内可能是OsBiP1的一种潜在的NEF。OsFes1C的过度表达或抑制导致水稻对内质网胁迫的超敏反应，影响水稻的生长。此外，我们建立了OsFes1C直接与盐反应蛋白（OsSalt）相互作用并参与盐反应。总之，我们的研究标志着阐明水稻内质网应激反应因子功能机制的重要一步。

The endoplasmic reticulum (ER) quality control (ERQC) system monitors protein homeostasis and relies on the activity of many molecular chaperones. Binding immunoglobulin protein (BiP) is a major ER luminal chaperone that is involved in most functions of the organelle. BiP activity is tightly regulated by nucleotide exchange factors (NEFs). However, information about NEFs in plants is limited. We obtained a Fes1-like protein (OsFes1C) through an iTRAQ-based proteomics analysis of ER-stressed rice (Oryza sativa) seeds. Unlike its homologs in yeast and mammals, which are located in the cytosol and respond to heat-stress, OsFes1C is an ER membrane protein and responds to ER- and salt-stresses. OsFes1C interacts directly with OsBiP1 and the interaction is inhibited by ATP but promoted by ADP, suggesting that OsFes1C acts as a potential NEF of OsBiP1 in vivo. Overexpression or suppression of OsFes1C led to hypersensitivity to ER stress and affected the growth of rice. Furthermore, we established that OsFes1C directly interacts with a putative salt response protein (OsSalt) and is involved in the salt response. Taken together, our study marks an important step toward elucidating the functional mechanisms of an identified ER stress response factor in rice.

https://academic.oup.com/plphys/advance-article-abstract/doi/10.1093/plphys/kiab263/6294938?redirectedFrom=fulltext

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