Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China.
CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, 518057, China.
J Integr Plant Biol. 2020 Feb;62(2):181-200. doi: 10.1111/jipb.12872. Epub 2019 Nov 19.
The endoplasmic reticulum (ER) is the major site for protein folding in eukaryotic cells. ER homeostasis is essential for the development of an organism, whereby the unfolded protein response (UPR) within the ER is precisely regulated. ER-phagy is a newly identified selective autophagic pathway for removal of misfolded or unfolded proteins within the ER in mammalian cells. Sec62, a component of the translocon complex, was recently characterized as an ER-phagy receptor during the ER stress recovery phase in mammals. In this study, we demonstrated that the Arabidopsis Sec62 (AtSec62) is required for plant development and might function as an ER-phagy receptor in plants. We showed that AtSec62 is an ER-localized membrane protein with three transmembrane domains (TMDs) with its C-terminus facing to the ER lumen. AtSec62 is required for plant development because atsec62 mutants display impaired vegetative growth, abnormal pollen and decreased fertility. atsec62 mutants are sensitive towards tunicamycin (TM)-induced ER stress, whereas overexpression of AtSec62 subsequently enhances stress tolerance during the ER stress recovery phase. Moreover, YFP-AtSec62 colocalizes with the autophagosome marker mCh-Atg8e in ring-like structures upon ER stress induction. Taken together, these data provide evidence for the pivotal roles of AtSec62 in plant development and ER-phagy.
内质网（ER）是真核细胞中蛋白质折叠的主要场所。内质网的内稳态对于生物体的发育至关重要，内质网中的未折叠蛋白反应（UPR）被精确调控。ER 自噬是一种新发现的哺乳动物细胞内质网中错误折叠或未折叠蛋白质的选择性自噬途径。Sec62，易位子复合物的一个组成部分，最近在哺乳动物的内质网应激恢复阶段被描述为 ER 自噬受体。在本研究中，我们证明了拟南芥 Sec62（AtSec62）是植物发育所必需的，并且可能在植物中作为 ER 自噬受体发挥作用。我们表明，AtSec62 是一种内质网定位的膜蛋白，具有三个跨膜结构域（TMD），其 C 末端朝向内质网腔。AtSec62 是植物发育所必需的，因为 atsec62 突变体表现出营养生长受损、花粉异常和生育力下降。atsec62 突变体对衣霉素（TM）诱导的内质网应激敏感，而过表达 AtSec62 随后增强了内质网应激恢复阶段的应激耐受性。此外，在 ER 应激诱导时，YFP-AtSec62 与自噬体标记 mCh-Atg8e 在环状结构中共定位。总之，这些数据为 AtSec62 在植物发育和 ER 自噬中的关键作用提供了证据。
