Adenosine-to-inosine RNA editing controls cathepsin S expression in atherosclerosis by enabling HuR-mediated post-transcriptional regulation

Abstract

Adenosine-to-inosine (A-to-I) RNA editing, which is catalyzed by a family of adenosine deaminase acting on RNA (ADAR) enzymes, is important in the epitranscriptomic regulation of RNA metabolism. However, the role of A-to-I RNA editing in vascular disease is unknown. Here we show that cathepsin S mRNA (CTSS), which encodes a cysteine protease associated with angiogenesis and atherosclerosis, is highly edited in human endothelial cells. The 3' untranslated region (3' UTR) of the CTSS transcript contains two inverted repeats, the AluJo and AluSx regions, which form a long stem-loop structure that is recognized by ADAR1 as a substrate for editing. RNA editing enables the recruitment of the stabilizing RNA-binding protein human antigen R (HuR; encoded by ELAVL1) to the 3' UTR of the CTSS transcript, thereby controlling CTSS mRNA stability and expression. In endothelial cells, ADAR1 overexpression or treatment of cells with hypoxia or with the inflammatory cytokines interferon-γ and tumor-necrosis-factor-α induces CTSS RNA editing and consequently increases cathepsin S expression. ADAR1 levels and the extent of CTSS RNA editing are associated with changes in cathepsin S levels in patients with atherosclerotic vascular diseases, including subclinical atherosclerosis, coronary artery disease, aortic aneurysms and advanced carotid atherosclerotic disease. These results reveal a previously unrecognized role of RNA editing in gene expression in human atherosclerotic vascular diseases.

A-to-I RNA Editing Up-regulates Human Dihydrofolate Reductase in Breast Cancer

“…The RNA editing sites were identified in inverted Alu repeats, which can form perfectly matched dsRNA structure. These results were consistent with a recent report showing that ADAR1, but not ADAR2, is the main RNA editing enzyme for reversely oriented Alu repeats (Stellos et al, 2016). In this study, knockdown of ADAR2 marginally increased RNA editing levels in the 3'-UTR of DHFR.…”

“…It is highly possible that miR-92a-3p and miR-92b-3p have the similar role as miR-25-3p, because these miRNAs shares the seed sequence. Beside miRNAs, a recent study revealed that RNA editing within reversely oriented Alu repeats in the 3'-UTR of cathepsin S enables to recuit RNAbinding protein human antigen R to this region, thereby increasing its mRNA stability (Stellos et al, 2016). Further studies are needed to uncover the significance of these factors on DHFR expression.…”

ADAR2 regulates RNA stability by modifying access of decay-promoting RNA-binding proteins

“…Previous studies have suggested that ADAR1 enhances the stability of mRNAs by facilitating the recruitment of HuR/ELAVL1 to these mRNAs (8,41). HuR/ELAVL1 is a U-/AU-rich element binding protein, is an established regulator of mRNA stability and potentially binds to ∼26 000 sites across the transcriptome (42–44).…”

Dynamic landscape and regulation of RNA editing in mammals

“…1c). The importance of RNA editing in vascular disease was demonstrated in a recent study 18 . We further validated the results obtained from the GTEx data by applying a targeted sequencing approach (microfluidics-based multiplex PCR and deep sequencing; mmPCR–seq) 19 (Supplementary Note 2) to examine 12,871 exonic sites in 672 loci (Supplementary File 2) on independent tissue samples from two individuals (Extended Data Fig.…”