Reduction of disulfide bridges in the lumenal domain of ATF6 in response to glucose starvation.
Mammalian transcription factor ATF6 is constitutively synthesized as a type II transmembrane protein embedded in the endoplasmic reticulum (ER). Upon ER stress ATF6 is transported to the Golgi apparatus where it is cleaved to release its cytoplasmic domain. This is then translocated into the nucleus where it activates transcription of ER-localized molecular chaperones and folding enzymes to maintain the homeostasis of the ER. We recently found that, owing to the presence of intra- and intermolecular disulfide bridges, ATF6 occurs in unstressed ER in monomer, dimer and oligomer forms. Disulfide-bonded ATF6 is reduced on treatment of cells with various chemical ER stress inducers, and only the reduced monomer ATF6 reaches the Golgi apparatus. In this study, we evoked ER stress under more physiological conditions, namely, glucose starvation, and analyzed its consequence for ATF6 activation. Glucose starvation activated ATF6 and induced the ER chaperone BiP, albeit weakly. ATF6 was thus dissociated from BiP, transported to the Golgi apparatus, and cleaved. Glucose starvation enhanced the synthesis of ATF6 approximately two-fold, probably via transcriptional induction. Importantly, reduction of disulfide bridges and transport of reduced monomer occurred in response to glucose starvation. We conclude that ER stress-induced reduction of ATF6 represents a general feature of the ATF6 activation process.
Nadanaka
Satomi
S
Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto 606-8502, Japan.
Yoshida
Hiderou
H
Mori
Kazutoshi
K
D051702:Activating Transcription Factor 6 / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004220:Disulfides / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D005947:Glucose / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D010084:Oxidation-Reduction; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D014162:Transfection
D051702:Activating Transcription Factor 6; D004220:Disulfides; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D005947:Glucose