LINC01013 Is a Determinant of Fibroblast Activation and Encodes a Novel Fibroblast-Activating Micropeptide

Abstract

Myocardial fibrosis confers an almost threefold mortality risk in heart disease. There are no prognostic therapies and novel therapeutic targets are needed. Many thousands of unannotated small open reading frames (smORFs) have been identified across the genome with potential to produce micropeptides (< 100 amino acids). We sought to investigate the role of smORFs in myocardial fibroblast activation.Analysis of human cardiac atrial fibroblasts (HCFs) stimulated with profibrotic TGFβ1 using RNA sequencing (RNA-Seq) and ribosome profiling (Ribo-Seq) identified long intergenic non-coding RNA LINC01013 as TGFβ1 responsive and containing an actively translated smORF. Knockdown of LINC01013 using siRNA reduced expression of profibrotic markers at baseline and blunted their response to TGFβ1. In contrast, overexpression of a codon-optimised smORF invoked a profibrotic response comparable to that seen with TGFβ1 treatment, whilst FLAG-tagged peptide associated with the mitochondria.Together, these data support a novel LINC01013 smORF micropeptide-mediated mechanism of fibroblast activation. Graphical Abstract TGFβ1 stimulation of atrial fibroblasts induces expression of LINC01013, whose knockdown reduces fibroblast activation. Overexpression of a smORF contained within LINC01013 localises to mitochondria and activates fibroblasts

Noncoding RNAs as Key Regulators for Cardiac Development and Cardiovascular Diseases

“…However, overexpression of LINC01013ORF induced markers of fibroblast activation to the same level as observed with TGF-β1 stimulation. Although the exact mechanism by which this micropeptide affects fibrosis has yet to be elucidated, its localization suggests that mitochondrial metabolism may play a role [97]. In addition, Chingnon et al reported that LINC01013 may induce calcification of the aortic valve via the TGF-β/CCN2/CTGF axis [98].…”

Retrospective transcriptome analyses identifyLINC01013as an activation marker in human dermal fibroblasts

“…Nevertheless, the advent of transcriptomic technologies, particularly those that can resolve single cells or spatial positioning, has revealed additional layers of complexity to myofibroblast identity, reinforcing the degree to which our understanding of these paradigms has been oversimplified and incomplete 1, 2 . A recent pair of reports identified the long noncoding RNA LINC01013 , sometimes referred to as AERRIE , as a positive regulator of myofibroblast differentiation in human valvular interstitial cells 3 and human cardiac fibroblasts 4 . These effects are purported to occur through direct potentiation of CCN2 expression by the lncRNA 3 , and/or through encoding translation of a pro-fibrotic micropeptide 4 .…”

“…A recent pair of reports identified the long noncoding RNA LINC01013 , sometimes referred to as AERRIE , as a positive regulator of myofibroblast differentiation in human valvular interstitial cells 3 and human cardiac fibroblasts 4 . These effects are purported to occur through direct potentiation of CCN2 expression by the lncRNA 3 , and/or through encoding translation of a pro-fibrotic micropeptide 4 . Since the presence and roles of myofibroblasts are somewhat conserved among fibrotic diseases of different tissues 5 , we hypothesized that LINC01013 might be overexpressed in human dermal myofibroblasts as well.…”

“…Taken together, these data collectively suggest that LINC01013 is overexpressed in fibrotic dermal fibroblasts, and that alleviation of fibroblast activation is associated with LINC01013 downregulation, denoting LINC01013 as a potential biomarker for pathological fibroblast activation. It is important to note that the scaling of LINC01013 upwards and downwards with fibroblast activation status is insufficient to conclude that its overexpression is causally involved in fibrotic pathology, but recent reports describing that LINC01013 drives fibroblast activation in cardiac fibroblasts 4 and valvular interstitial cells 3 , pathological processes analogous to persistent fibroblast activation characteristic of fibrotic dermal pathologies, suggests that this possibility is worthy of further pursuit and investigation.…”

RN7SL1 may be translated under oncogenic conditions

“…Some ncRNAs possess small open reading frames (smORFs) that encode small proteins of less than 100 amino acids ( 7 , 8 ). LINC01013 , a type of long intergenic ncRNA (lncRNA), contains smORF, and micropeptide translated from it was reported to activate myocardial fibroblasts ( 9 ). It was also reported that smORFs are also present in pri-miRNAs, which are precursors of microRNAs (miRNAs), and that smORFs regulate their expression levels in pri-miR-155 and pri-miR-497 ( 10 ).…”