Carrara Marta, Prischi Filippo, Nowak Piotr R, Ali Maruf Mu
Department of Life Sciences, Imperial College, London, UK.
Department of Life Sciences, Imperial College, London, UK
EMBO J. 2015 Jun 3;34(11):1589-600. doi: 10.15252/embj.201489183. Epub 2015 Apr 28.
Stress caused by accumulation of misfolded proteins within the endoplasmic reticulum (ER) elicits a cellular unfolded protein response (UPR) aimed at maintaining protein-folding capacity. PERK, a key upstream component, recognizes ER stress via its luminal sensor/transducer domain, but the molecular events that lead to UPR activation remain unclear. Here, we describe the crystal structures of mammalian PERK luminal domains captured in dimeric state as well as in a novel tetrameric state. Small angle X-ray scattering analysis (SAXS) supports the existence of both crystal structures also in solution. The salient feature of the tetramer interface, a helix swapped between dimers, implies transient association. Moreover, interface mutations that disrupt tetramer formation in vitro reduce phosphorylation of PERK and its target eIF2α in cells. These results suggest that transient conversion from dimeric to tetrameric state may be a key regulatory step in UPR activation.
内质网（ER）中错误折叠蛋白的积累所引起的应激会引发细胞内未折叠蛋白反应（UPR），旨在维持蛋白质折叠能力。PERK作为一个关键的上游组件，通过其腔内传感器/转导结构域识别内质网应激，但导致UPR激活的分子事件仍不清楚。在这里，我们描述了处于二聚体状态以及一种新型四聚体状态的哺乳动物PERK腔内结构域的晶体结构。小角X射线散射分析（SAXS）支持这两种晶体结构在溶液中也存在。四聚体界面的显著特征，即二聚体之间交换的一个螺旋，意味着瞬时缔合。此外，在体外破坏四聚体形成的界面突变会减少细胞中PERK及其靶标eIF2α的磷酸化。这些结果表明，从二聚体状态到四聚体状态的瞬时转变可能是UPR激活中的一个关键调节步骤。
