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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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 3

A role for MAGI1-S741 phosphorylation in EC activation.

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A role for MAGI1-S741 phosphorylation in EC activation. (A) D-flow–induc...
(A) D-flow–induced NF-κB activation is reduced in HUVECs expressing the MAGI1-S741A mutant. ECs expressing MAGI1-WT or -S741A were subjected to an NF-κB activity assay with exposure to d-flow for 24 hours, and the relative NF-κB luciferase activity in the cells was measured. Data represent mean ± SEM (n = 4). *P < 0.05; **P < 0.01. (B–F) p90RSK phosphorylates MAGI1-S741 and mediates expression of adhesion molecules. ECs transduced (MOI, 20) with Ad-Flag MAGI1-WT or -S741A (B, E–G), and Ad-LacZ or Flag DN-p90RSK (C) were exposed to d-flow (B, C, E, and F) or Thb (10 U/ml, 24 h) (G), and phosphorylation of MAGI1-S741 (B and C) and expression of MAGI1, DN-p90RSK, VCAM-1, E selectin, and tubulin (B, C, E, and F) were assayed using IB. (D) In vitro phosphorylation of MAGI1 by p90RSK was performed, and MAGI1 was immunoprecipitated and immunoblotted with anti-phospho-MAGI1 (S741) (top). The same amount of MAGI1 was immunoprecipitated by anti-MAGI1, but not by non-immune IgG (bottom). The graph shows densitometric quantification of phosphorylated MAGI1-S741, which was normalized by total MAGI1 protein levels. Data represent mean ± SEM (n = 3). **P < 0.01. (F) Densitometric data for immunoblots of VCAM-1 (n = 4), which were similar to those shown in E. Data represent mean ± SEM. **P < 0.01. (G) Levels of VCAM-1, ICAM-1, and E selectin RNA expression were quantified. Data represent mean ± SEM (n = 4–6). **P < 0.01. Statistical differences between 2 independent groups (D) were assessed using the 2-tailed Student’s t test and 1-way ANOVA followed by Bonferroni’s post hoc testing for multiple groups (A, F, and G).