Vertebrate Unfolded Protein Response: Mammalian Signaling Pathways Are Conserved in Medaka Fish

Cell Structure and Function

Shunichi Takeda¹  Kazutoshi Mori²  Tetsuya Okada²  Yoshihito Taniguchi¹  Tokiro Ishikawa² 

[1] Department of Radiation Genetics, Graduate School of Medicine, Kyoto University;Department of Biophysics, Graduate School of Science, Kyoto University

关键词: endoplasmic reticulum;    protein folding;    molecular chaperone;    transcription;    translation;   

DOI  :  10.1247/csf.11036

学科分类：分子生物学，细胞生物学和基因

来源: Japan Society for Cell Biology

【 摘 要 】

References(24)Cited-By(9)The accumulation of unfolded proteins in the endoplasmic reticulum (ER) activates the unfolded protein response (UPR). The ER stress signal is sensed and transmitted by a transmembrane protein(s) in the ER. The number of these transducers has increased with evolution, one in yeast, three in worm and fly, and five in mammals. Here, we examined medaka fish, Oryzias latipes, as a vertebrate model organism, and found that the medaka genome encodes five UPR transducers. Analysis of a medaka embryonic cell line revealed that the mammalian UPR signaling mechanisms are very well conserved. Thus, XBP1 mRNA, which encodes the transcription factor XBP1 downstream of the IRE1 pathway, was spliced in response to ER stress, resulting in production of the active form of XBP1. Translation was generally attenuated in response to ER stress, which paradoxically induced the translation of ATF4, the transcription factor downstream of the PERK pathway. ATF6 was constitutively synthesized as a transmembrane protein and activated by ER stress-induced proteolysis. Results obtained with the overexpression of active ATF6α, ATF6β, and XBP1 strongly suggested that ATF6α plays a major role in upregulating the major ER chaperone BiP, contrary to the case in non-vertebrates, in which the IRE1 pathway is essential to the induction of BiP. Physiological ER stress occurring during embryonic development was visualized using transgenic medaka carrying the enhanced green fluorescent protein gene under the control of the BiP promoter. Thus, analysis of the vertebrate UPR using medaka will help provide a more comprehensive understanding of the biology and physiology of the UPR.

【 授权许可】

Unknown