Wolfram syndrome 1 gene negatively regulates ER stress signaling in rodent and human cells
Sonya G. Fonseca, Shinsuke Ishigaki, Christine M. Oslowski, Simin Lu, Kathryn L. Lipson, Rajarshi Ghosh, Emiko Hayashi, Hisamitsu Ishihara, Yoshitomo Oka, M. Alan Permutt, Fumihiko Urano
Sonya G. Fonseca, Shinsuke Ishigaki, Christine M. Oslowski, Simin Lu, Kathryn L. Lipson, Rajarshi Ghosh, Emiko Hayashi, Hisamitsu Ishihara, Yoshitomo Oka, M. Alan Permutt, Fumihiko Urano
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Research Article Metabolism

Wolfram syndrome 1 gene negatively regulates ER stress signaling in rodent and human cells

Abstract

Wolfram syndrome is an autosomal-recessive disorder characterized by insulin-dependent diabetes mellitus, caused by nonautoimmune loss of β cells, and neurological dysfunctions. We have previously shown that mutations in the Wolfram syndrome 1 (WFS1) gene cause Wolfram syndrome and that WFS1 has a protective function against ER stress. However, it remained to be determined how WFS1 mitigates ER stress. Here we have shown in rodent and human cell lines that WFS1 negatively regulates a key transcription factor involved in ER stress signaling, activating transcription factor 6α (ATF6α), through the ubiquitin-proteasome pathway. WFS1 suppressed expression of ATF6α target genes and repressed ATF6α-mediated activation of the ER stress response element (ERSE) promoter. Moreover, WFS1 stabilized the E3 ubiquitin ligase HRD1, brought ATF6α to the proteasome, and enhanced its ubiquitination and proteasome-mediated degradation, leading to suppression of ER stress signaling. Consistent with these data, β cells from WFS1-deficient mice and lymphocytes from patients with Wolfram syndrome exhibited dysregulated ER stress signaling through upregulation of ATF6α and downregulation of HRD1. These results reveal a role for WFS1 in the negative regulation of ER stress signaling and in the pathogenesis of diseases involving chronic, unresolvable ER stress, such as pancreatic β cell death in diabetes.

Authors

Sonya G. Fonseca, Shinsuke Ishigaki, Christine M. Oslowski, Simin Lu, Kathryn L. Lipson, Rajarshi Ghosh, Emiko Hayashi, Hisamitsu Ishihara, Yoshitomo Oka, M. Alan Permutt, Fumihiko Urano

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Figure 1

WFS1 interacts with ATF6α in an ER stress–dependent manner and suppresses ATF6α transcriptional activation.

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WFS1 interacts with ATF6α in an ER stress–dependent manner and suppresse...
(A) COS7 cells were transfected with a full-length ATF6α expression plasmid or ΔATF6α with a WFS1 plasmid together with the following luciferase reporter genes: ATF6α binding site reporter gene ATF6GL3, ATF6α mutant site reporter ATF6m1GL3, and GRP78 promoter reporter gene ERSE. Relative intensity of luciferase was then measured (n = 3). (B) Protein lysates from the luciferase assay were analyzed by IB using anti-HA (ATF6α), anti-Flag (WFS1), and anti-actin antibodies. ATF6α and ΔATF6α are denoted by single and double asterisks, respectively. (C) COS7 cells were transfected with a full-length ATF6α expression plasmid with a BiP expression plasmid, WFS1 expression plasmid, or WFS1 and BiP expression plasmid together with the GRP78 reporter gene (n = 3). (D) An anti-WFS1 antibody was used to IP WFS1 protein from INS1 832/13 cells untreated (UT) or treated with the ER stress inducer DTT (1 mM) for 0.5, 1.5, or 3 hours. IPs were then subject to IB analysis using anti-ATF6α, anti-WFS1, and anti-actin antibodies (n = 3). (E) INS1 832/13 cells were treated with DTT (1 mM) for 2 hours and then chased in normal media for 0, 1, or 2 hours. WFS1 was subjected to IP from cell lysates, and IPs were analyzed by IB using anti-ATF6α, anti-WFS1, and anti-actin antibodies (n = 3).