MAGI1 as a link between endothelial activation and ER stress drives atherosclerosis
Jun-ichi Abe, … , Scott E. Evans, Nhat-Tu Le
Jun-ichi Abe, … , Scott E. Evans, Nhat-Tu Le
Published April 4, 2019
Citation Information: JCI Insight. 2019;4(7):e125570. https://doi.org/10.1172/jci.insight.125570.
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Categories: Research Article Cardiology Cell biology

MAGI1 as a link between endothelial activation and ER stress drives atherosclerosis

Abstract

The possible association between the membrane-associated guanylate kinase with inverted domain structure-1 (MAGI1) and inflammation has been suggested, but the molecular mechanisms underlying this link, especially during atherogenesis, remain unclear. In endothelial cells (ECs) exposed to disturbed flow (d-flow), p90 ribosomal S6 kinase (p90RSK) bound to MAGI1, causing MAGI1-S741 phosphorylation and sentrin/SUMO-specific protease 2 T368 phosphorylation-mediated MAGI1-K931 deSUMOylation. MAGI1-S741 phosphorylation upregulated EC activation via activating Rap1. MAGI1-K931 deSUMOylation induced both nuclear translocation of p90RSK-MAGI1 and ATF-6-MAGI1 complexes, which accelerated EC activation and apoptosis, respectively. Microarray screening revealed key roles for MAGI1 in the endoplasmic reticulum (ER) stress response. In this context, MAGI1 associated with activating transcription factor 6 (ATF-6). MAGI1 expression was upregulated in ECs and macrophages found in atherosclerotic-prone regions of mouse aortas as well as in the colonic epithelia and ECs of patients with inflammatory bowel disease. Further, reduced MAGI1 expression in Magi1–/+ mice inhibited d-flow–induced atherogenesis. In sum, EC activation and ER stress–mediated apoptosis are regulated in concert by two different types of MAGI1 posttranslational modifications, elucidating attractive drug targets for chronic inflammatory disease, particularly atherosclerosis.

Authors

Jun-ichi Abe, Kyung Ae Ko, Sivareddy Kotla, Yin Wang, Jesus Paez-Mayorga, Ik Jae Shin, Masaki Imanishi, Hang Thi Vu, Yunting Tao, Miguel M. Leiva-Juarez, Tamlyn N. Thomas, Jan L. Medina, Jong Hak Won, Yuka Fujii, Carolyn J. Giancursio, Elena McBeath, Ji-Hyun Shin, Liliana Guzman, Rei J. Abe, Jack Taunton, Naoki Mochizuki, William Faubion, John P. Cooke, Keigi Fujiwara, Scott E. Evans, Nhat-Tu Le

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Figure 1

MAGI1 expression is required for d-flow–induced EC activation.

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MAGI1 expression is required for d-flow–induced EC activation. (A and B)...
(A and B) Expression of VCAM-1, MAGI1, and α-tubulin in NLC and Magi1–/– MECs treated with TNF-α (10 ng/ml) for 0–6 hours was determined by Western blotting. (B) VCAM-1 expression quantified by densitometry. Data represent mean ± SEM (n = 3). P < 0.0001 between NLC and Magi1–/– groups. (C) MAGI1 depletion inhibits NF-κB activation. MECs were subjected to an NF-κB activity assay in the presence (right) or absence (left) of p90RSK overexpression. Cells were then treated with TNF-α for 24 hours (10 ng/ml, left), and their NF-κB activity was measured. Data represent mean ± SEM (n = 6). **P < 0.01. (D) MAGI1 expression is reduced in HUVECs treated with siRNA-targeted Magi1 (siMAGI1). siCont, control siRNA. (E) MAGI1 depletion inhibits NF-κB activation. HUVECs were transfected with the indicated siRNAs and then treated with or without d-flow (left), TNF-α (10 ng/ml, middle), or Thb (10 U/ml, right) for 24 hours, and their relative NF-κB luciferase activity was measured. Data represent mean ± SEM (n = 6). **P < 0.01. (F) MAGI1 depletion inhibits NF-κB activation in human colonic epithelial cells (HCnEpC). Cells were transfected with the indicated siRNAs and treated with or without Thb (10 U/ml for 24 hours), and their relative level of NF-κB luciferase activity was measured. Data represent mean ± SEM (n = 6). (G) MAGI1 depletion inhibits d-flow–induced expression of adhesion molecules. siRNA-treated ECs were exposed to d-flow, total RNA was obtained from the cells, and levels of VCAM-1, ICAM-1, and E selectin RNA expression were quantified using qRT-PCR. Data represent mean ± SEM (n = 3). *P < 0.05; **P < 0.01. (H) Reduced intensity of VCAM-1 staining in the d-flow region in the Magi1+/– mouse group. En face preparations of mouse aortas were coimmunostained with anti–VE-cadherin and –VCAM-1 antibodies. Fluorescent images of anti–VCAM-1 staining in aorta areas exposed to l-flow and d-flow were recorded using confocal laser scanning microscopy (left). Scale bars: 20 μm. Data represent mean ± SEM (n = 3). **P < 0.01. Statistical differences between 2 independent groups (H) were assessed using the 2-tailed Student’s t test and 1-way ANOVA followed by Bonferroni’s post hoc testing for multiple groups (B, C, E, F, and G).