CPSF6 loss mediates LDHA 3'UTR shortening to promote fibroblast glycolysis and pulmonary fibrosis

Abstract

Pulmonary fibrosis is a chronic and progressive fibrotic lung disease with a poor prognosis and few treatment options. Alternative polyadenylation (APA), an important post-transcriptional regulatory mechanism, remains poorly understood in pulmonary fibrosis. In this study, we found that cleavage and polyadenylation-specific factor 6 (CPSF6), a key regulator of APA, was downregulated in silica-induced mouse fibrotic lung tissue. AAV-mediated in vivo overexpression of CPSF6 could mitigate the progression of pulmonary fibrosis induced by silica. Moreover, CPSF6 knockdown in fibroblasts enhanced fibroblast (MRC-5 cell line and mouse primary lung fibroblast) activation and glycolytic activity. ONT-RNA-seq data and subsequent experiments indicated that CPSF6 loss favored the utilization of the proximal poly (A) site in the 3' untranslated region (UTR) of lactate dehydrogenase (LDHA), resulting in a short-3'UTR LDHA isoform that produced more protein due to avoiding miR-4317 targeting. The upregulation of LDHA mediated the profibrotic effect of CPSF6 loss by facilitating glycolysis and contributed to the transition of fibroblasts into myofibroblasts. Taken together, our findings indicate that the CPSF6 silence promotes fibroblast glycolysis and pulmonary fibrosis progression by upregulating LDHA expression through the loss of miR-4317-mediated repression resulting from alternative polyadenylation of the LDHA mRNA 3' UTR. CPSF6 and its downstream effector may represent promising targets for pulmonary fibrosis treatment.

Keywords: Alternative polyadenylation; CPSF6; LDHA; Silicosis.