Abstract 11607: Protein Citrullination Landscape of Human Coronary Atherosclerosis

Abstract

Introduction: Recently, an irreversible enzymatic post-translational modification, citrullination, has been shown to be present in the cardiovascular system (e.g. aorta). Citrullination, in which arginine is converted to citrulline, can alter protein structure and function, and produce autoantigens Hypothesis: Emerging evidence suggest a potential role for autoimmunity in the pathogenesis of atherosclerosis. However, it remains unknown whether of post-translational citrullination of arterial proteins contributes to local inflammatory processes that initiate or accelerate the atherosclerotic process. The aim of this study was to investigate changes in protein citrullination in human left anterior descending (LAD) coronary artery specimens with and without early atherosclerosis obtained from autopsied young adults with no clinical manifestations of coronary disease. Methods: Segments of the mid-LAD from 74 autopsied individuals (age range:15-55 yrs., 75% male, 67% White) were graded by a pathologist for percent of surface area involved with fatty streaks (FS) or fibrous plaque (FP). The frozen samples were homogenized and digested with Lys-C for subsequent proteomic mass-spectrometry using a data-independent acquisition (DIA) proteomic strategy with a hyper-citrullinated spectral library approach and our published CitFinder software. Results: We found 133 differentially expressed proteins (FDR<0.05) between control, FS and FP groups. Among them, 19 citrullinated proteins with 26 modified amino acid residues were identified. Citrullinated peptides from fibrinogen alpha chain (R84) and transgelin (R146) were upregulated in FP samples in comparison to FS and normal samples. Similarly, the citrullination site (R269) on alpha-enolase was significantly increased in the FP samples compared to normal. Interestingly, citrullination (R110) on myosin light polypeptide 6 was downregulated in FP samples. Conclusions: These data represent the most comprehensive interrogation of citrullinated proteins in human arterial samples to-date and suggest a possible association between this modification of several key proteins involved in tight junction, vascular smooth muscle contraction and inflammation and early atherosclerosis.