Biochimica et Biophysica Acta 2015-07-01

p-SMAD2/3 and DICER promote pre-miR-21 processing during pressure overload-associated myocardial remodeling.

Raquel García, J Francisco Nistal, David Merino, Nathan L Price, Carlos Fernández-Hernando, Javier Beaumont, Arantxa González, María A Hurlé, Ana V Villar

Index: Biochim. Biophys. Acta 1852 , 1520-30, (2015)

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Abstract

Transforming growth factor-β (TGF-β) induces miR-21 expression which contributes to fibrotic events in the left ventricle (LV) under pressure overload. SMAD effectors of TGF-β signaling interact with DROSHA to promote primary miR-21 processing into precursor miR-21 (pre-miR-21). We hypothesize that p-SMAD-2 and -3 also interact with DICER1 to regulate the processing of pre-miR-21 to mature miR-21 in cardiac fibroblasts under experimental and clinical pressure overload. The subjects of the study were mice undergoing transverse aortic constriction (TAC) and patients with aortic stenosis (AS). In vitro, NIH-3T3 fibroblasts transfected with pre-miR-21 responded to TGF-β1 stimulation by overexpressing miR-21. Overexpression and silencing of SMAD2/3 resulted in higher and lower production of mature miR-21, respectively. DICER1 co-precipitated along with SMAD2/3 and both proteins were up-regulated in the LV from TAC-mice. Pre-miR-21 was isolated bound to the DICER1 maturation complex. Immunofluorescence analysis revealed co-localization of p-SMAD2/3 and DICER1 in NIH-3T3 and mouse cardiac fibroblasts. DICER1-p-SMAD2/3 protein-protein interaction was confirmed by in situ proximity ligation assay. Myocardial up-regulation of DICER1 constituted a response to pressure overload in TAC-mice. DICER mRNA levels correlated directly with those of TGF-β1, SMAD2 and SMAD3. In the LV from AS patients, DICER mRNA was up-regulated and its transcript levels correlated directly with TGF-β1, SMAD2, and SMAD3. Our results support that p-SMAD2/3 interacts with DICER1 to promote pre-miR-21 processing to mature miR-21. This new TGFβ-dependent regulatory mechanism is involved in miR-21 overexpression in cultured fibroblasts, and in the pressure overloaded LV of mice and human patients. Copyright © 2015 Elsevier B.V. All rights reserved.