MicroRNA-26 governs profibrillatory inward-rectifier potassium current changes in atrial fibrillation
Xiaobin Luo, … , Baofeng Yang, Stanley Nattel
Xiaobin Luo, … , Baofeng Yang, Stanley Nattel
Published April 1, 2013
Citation Information: J Clin Invest. 2013;123(5):1939-1951. https://doi.org/10.1172/JCI62185.
View: Text | PDF
Research Article Cardiology

MicroRNA-26 governs profibrillatory inward-rectifier potassium current changes in atrial fibrillation

Abstract

Atrial fibrillation (AF) is a highly prevalent arrhythmia with pronounced morbidity and mortality. Inward-rectifier K+ current (IK1) is believed to be an important regulator of reentrant-spiral dynamics and a major component of AF-related electrical remodeling. MicroRNA-26 (miR-26) is predicted to target the gene encoding KIR2.1, KCNJ2. We found that miR-26 was downregulated in atrial samples from AF animals and patients and this downregulation was accompanied by upregulation of IK1/KIR2.1 protein. miR-26 overexpression suppressed expression of KCNJ2/KIR2.1. In contrast, miR-26 knockdown, inhibition, or binding-site mutation enhanced KCNJ2/KIR2.1 expression, establishing KCNJ2 as a miR-26 target. Knockdown of endogenous miR-26 promoted AF in mice, whereas adenovirus-mediated expression of miR-26 reduced AF vulnerability. Kcnj2-specific miR-masks eliminated miR-26–mediated reductions in Kcnj2, abolishing miR-26’s protective effects, while coinjection of a Kcnj2-specific miR-mimic prevented miR-26 knockdown-associated AF in mice. Nuclear factor of activated T cells (NFAT), a known actor in AF-associated remodeling, was found to negatively regulate miR-26 transcription. Our results demonstrate that miR-26 controls the expression of KCNJ2 and suggest that this downregulation may promote AF.

Authors

Xiaobin Luo, Zhenwei Pan, Hongli Shan, Jiening Xiao, Xuelin Sun, Ning Wang, Huixian Lin, Ling Xiao, Ange Maguy, Xiao-Yan Qi, Yue Li, Xu Gao, Deli Dong, Yong Zhang, Yunlong Bai, Jing Ai, Lihua Sun, Hang Lu, Xiao-Yan Luo, Zhiguo Wang, Yanjie Lu, Baofeng Yang, Stanley Nattel

×

Figure 7

NFAT-dependent regulation of miR-26 in AF.

Options: View larger image (or click on image) Download as PowerPoint
NFAT-dependent regulation of miR-26 in AF. (A) EMSA to test in vitro bin...
(A) EMSA to test in vitro binding of NFATc3 to its cis-acting element in the promoter region of human host genes for miR-26a-1, miR-26a-2, and miR-26b. Note shifted band representing protein-DNA binding (arrows), abolished with excess nonlabeled probe. Supershifted band (hollow arrows) represents NFATc3-cis-acting element binding in presence of anti-NFATc3 antibody. (B) ChIP testing in vivo binding of NFAT to human host genes of miR-26a-1, miR-26a-2, and miR-26b. Top: PCR products of 5′ flanking region encompassing NFAT-binding sites following immunoprecipitation with anti-NFATc3 antibody. Bottom: host gene binding measured by qPCR following ChIP, expressed as fold-changes over IgG-negative control. Input: genomic DNA without immunoprecipitation. **P < 0.01, ***P < 0.001 vs. IgG; n = 3/group. (C) Western blot showing Kir2.1 downregulation by INCA6 (100 nM). **P < 0.01 vs. control; n = 5/group. Values in B and C are mean ± SEM. (D) Immunohistochemical images showing nuclear translocation of NFATc3 and NFATc4 in atrial samples from AF dogs (CA) and patients (HA). Blue, nuclear staining (DAPI); red, NFAT staining; violet, NFAT nuclear localization in merged images. Findings similar to those in D were obtained in 3 subjects per group. Scale bars: 25 μm.