Investigating the potential role of USP18 in atherosclerosis based on bioinformatics analysis

Abstract Background: Ubiquitin-specific protease 18 (USP18), is a member of the ubiquitin-specific protease family. Previous studies have shown that USP18 expression is upregulated in the patients with heart failure and USP18 is considered as a novel target for the treatment of heart failure. However, the role of USP18 in atherosclerosis remains unclear. In this study, we aimed to investigate the expression pattern of USP18 in atherosclerosis and its relationship between the extent of atherosclerotic and the cholesterol transporter protein ABCG1. Methods: GSE6054 dataset was obtained from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were analyzed by using the "limma" package in R (version 4.1.3). H-DOCK was applied to perform protein-protein docking for predicting the interaction between USP18 and ATP-binding cassette transporter protein G1 (ABCG1). Immunohistochemistry(IHC), immunofluorescence(IF), and Western blot were used to assess the protein expression of USP18 and ABCG1 in human coronary arteries. Dual immunofluorescencewas performed for co-localization analysis of USP18 and ABCG1 Results: Bioinformatics analysis identified 462 DEGs including 239 upregulated and 223 downregulated genes in familial hypercholesterolaemia (FH) patients, of which USP18 was upregulated in monocytes. Gene Ontology enrichment analysis indicated that the biological functions of USP18 were mainly enriched in endopeptidase activity and cytokine-mediated signaling. Protein-protein docking by H-DOCK showed that USP18 and ABCG1 interacted at a free energy of -20 kcal/mol (free energy < 0 was considered meaningful). USP18 expression is upregulated in patients with coronary artery disease and negatively correlates with the extent of atherosclerosis. At the same time, The expression of ABCG1 is downregulated in CHD and SCD patients and is more pronounced in SCD patients. In atherosclerotic tissues, USP18 and ABCG1 expression were positively correlated. In addition, double immunofluorescence assay showed co-localization of USP18 and ABCG1. Conclusions: USP18 is a differentially expressed gene of FH, and its expression in atherosclerosis is closely related to the extent of atherosclerosis.