Abstract 106: Ribosomal Protein Rpl17 Controls Endothelial Cell Translation: A Key Mediator Of Intima Growth And Vascular Disease

Abstract

Background: Carotid intima-media thickening (IMT) is a significant risk factor for cardiovascular disease (CVD). Using genetic analysis of the partial carotid ligation (PCL) model of disturbed flow induced IMT, we identified a strong association between decreased expression of the large ribosomal subunit protein 17 (RpL17) and increased IMT. RpL17 is located at the exit tunnel of the ribosome, making it critical for processing of newly translated proteins. To define the mechanism by which RpL17 inhibits IMT, we generated EC-restricted (Cdh5-Cre) conditional RpL17 heterozygous mice (EC-RpL17). Results: 1) PCL of EC-RpL17 increased IMT vs wild type (Control) littermates. 2) EM analysis revealed decreases in total ribosome number and polysomes in EC-RpL17, consistent with decreased global translation. 3) RNA-seq showed major changes in two pathways: Eukaryotic Initiation Factor 2 (eIF2α) that promotes adaptive translational responses to stress, and oxidative phosphorylation (OXPHOS), the electron transport metabolic pathway that produces ATP. 4) Profiling of mRNAs bound to polysomes in RpL17-EC revealed increased translational efficiency (TE) of selective redox regulators, pro-inflammatory mediators, matrix metalloproteases, and endothelial to mesenchymal transition (endMT) factors; consistent with processes that promote IMT. 5) Increased levels of RNA binding proteins (RBPs) in EC-RpL17, such as QKI, HuR, and hn-RNP, correlated with enhanced stability of specific mRNAs and their TE. 6) Increased TE of glycolytic enzymes and the lactate transporter was consistent with increased EC glycolysis and OXPHOS dysfunction. 7) Increased glycolysis correlated with greater cell proliferation, suggesting RpL17 is a growth suppressor. Conclusion: These data define a new mechanism for control of EC function via selective changes in mRNA stability and ribosome profile and number that decreased OXPHOS and global protein translation, leading to EC-proliferation and endMT, which enhanced IMT in the PCL model of disturbed flow.