Abstract 13188: Co-Translational Profiling in the Cardiac Endothelium During the Development of Sepsis

Abstract

Introduction: The production of functional proteins is a multistep process whereby key maturation and regulatory processes occur co-translationally by coupling mRNA translation and nascent polypeptide chain maturation on the ribosome. However, limited data exist regarding co-translational regulation in the cells of the intact cardiovascular system. To overcome this limitation, we adapted the translating ribosome affinity purification (TRAP) approach using the HA-tagged ribosomal protein L22 reporter mouse (RiboTag) crossed with an inducible endothelial-specific Cdh5creERT2 mouse ( RiboTag EC ). Hypothesis: We hypothesized this model would permit the simultaneous immunoprecipitation (IP) of mRNA and nascent proteins for RNAseq and proteomic analysis from the coronary endothelium. Methods: Mice were injected with E. coli lipopolysaccharide (LPS) (6mg/Kg, i.p. 12 hours) to induce sepsis and perturb endothelial cell function. Hearts were homogenized, a small amount (~10%) was used for RNA-Seq and proteomics input controls (IN), and the remainder was used to IP ribosomal bound polyA+ mRNA and nascent proteins. Eluted proteins were digested, labeled with isobaric tags for quantification, and analyzed by MS3 with a Thermo Scientific Fusion Lumos Orbitrap. Results: Principal components analysis of the RNAseq data showed clear separation of the IP (endothelial cells) and IN (whole heart) transcriptomes between control and LPS groups. Transcripts characteristic of endothelial cells (EC) were enriched, whereas markers characteristic of cardiomyocytes, fibroblasts, and smooth muscle cells were depleted. Overall, >7000 proteins were identified, and initial analysis showed similar depletion and enrichment of proteins in the control and LPS hearts. Alignment of transcript and protein datasets was used for bioinformatic analysis. A hierarchical view of one of the top networks in which concordant expression of both EC transcripts and proteins identified interferon-gamma (IFNG) as an upstream signal in the pathogenesis of sepsis. Conclusions: Our “functional translatome” approach is a new discovery platform for a deeper predictive analysis of functionally relevant signaling networks and disease pathways in the intact cardiovascular system.