[1FT-3] Protein/cellular functions, Imaging (1P-49～1P-61)

[1P-55*] Mechanisms of ER-associated degradation pathway mediated by the cooperation of ERdj5 and BiP

^○Xiaohan Cai¹, Shogo Ito¹, Kentaro Noi³, Michio Inoue², Ryo Ushioda⁴, Kazuhiro Nagata⁴, Kenji Inaba^1,2 (1.Graduate School of Life Sciences, Tohoku University, 2.Institute of Multidisciplinary Research for Advanced Material, Tohoku University, 3.Institute for Nano Science Design, Osaka University, 4.Department of Molecular Biosciences, Kyoto Sangyo University)

ER-associate degradation (ERAD) is an ER quality control process that eliminates terminally misfolded proteins. ERdj5, a member of the PDI family, has been reported to play a key role in the clearance of aberrant proteins with the help of an ER-resident chaperone BiP. However, until now, the detailed molecular mechanism by which ERdj5 fulfills its function in concert with BiP in the ERAD pathway is still poorly understood. Here, we use disulfide-linked J-chain oligomers as a substrate, and succeeded in monitoring the sequential reduction of J-chain oligomers catalyzed by the cooperation of ERdj5 and BiP. ERdj5 consists of the N-terminal and C-terminal clusters with six tandem thioredoxin (Trx)-like domains and an inter-cluster flexible linker loop. Our biochemical studies showed that the C-terminal Trx4 domain catalyzes disulfide reduction of J-chain oligomers most efficiently, and that the restricted cluster dynamics led to the prevention of this reaction. Our results indicate a distinct role of each Trx-like domain of ERdj5 and the essentiality of ERdj5 conformational dynamics in promotion of ERAD.