The endoplasmic reticulum stress response is stimulated through the continuous activation of transcription factors ATF6 and XBP1 in Ins2+/Akita pancreatic beta cells.
The dominant C96Y mutation of one of the two murine insulin genes, Ins2, causes diabetes mellitus in 'Akita' mice. Here we established pancreatic islet beta cell lines from heterozygous mice (Ins2+/Akita). Western blot analysis of endoplasmic reticulum (ER) molecular chaperones indicated that Grp78, Grp94 and Orp150 are significantly increased in Ins2+/Akita cells compared with wild-type (Ins2+/+) cells. Reporter gene assays using the human GRP78 promoter with or without the ER stress response element (ERSE) showed that Ins2+/Akita cells exhibit significantly stronger ERSE-dependent transcriptional activity than Ins2+/+ cells. Transient over-expression of the Ins2 C96Y mutant in wild-type beta cells induces a stronger ERSE-dependent stress response than does wild-type Ins2 over-expression. The ERSE-binding transcription factor ATF6 is strongly activated in Ins2+/Akita cells. The activity of a reporter containing the specific binding sequence of another ERSE-binding transcription factor, XBP1, is also enhanced in Ins2+/Akita cells. Levels of active forms of XBP1 mRNA and protein are both markedly elevated in Ins2+/Akita cells. These results indicate that this cell line is subject to continuous ER stress and that the Ins2 C96Y mutation induces the expression of ER chaperones through the activation of ATF6 and XBP1.
Department of Molecular and Cellular Biology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8397, Japan.
Jun ichi
Ji
Nozaki
Hiroshi
H
Kubota
Hiderou
H
Yoshida
Motoko
M
Naitoh
Junko
J
Goji
Takeo
T
Yoshinaga
Kazutoshi
K
Mori
Akio
A
Koizumi
Kazuhiro
K
Nagata
D051702:Activating Transcription Factor 6; D000818:Animals; D018929:Cell Culture Techniques; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D017930:Genes, Reporter; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics*; D007328:Insulin / Q000096:biosynthesis / Q000235:genetics*; D007515:Islets of Langerhans / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D018832:Molecular Chaperones / Q000235:genetics; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012326:RNA Splicing / Q000235:genetics; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000235:genetics; D000071717:X-Box Binding Protein 1
D051702:Activating Transcription Factor 6; C497112:Atf6 protein, mouse; D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D007328:Insulin; D018832:Molecular Chaperones; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C000605544:Xbp1 protein, mouse