Investigating the potential role of USP18 in atherosclerosis by regulating cholesterol efflux based on bioinformatics analysis

Abstract

Abstract Background Ubiquitin-specific protease 18 (USP18), also known as UBP43, is a member of the ubiquitin-specific protease family involved in suppressing viral activity and promoting tumor migration. 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 sought to explore the role of USP18 on ATP-binding cassette transporter protein G1 (ABCG1)-dependent cholesterol efflux. 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 ABCG1. Immunohistochemistry(IHC), immunofluorescence(IF), and Western blot were used to assess the protein expression of USP18 and ABCG1 in human coronary arteries. Dual immunofluorescence was performed for co-localization analysis of USP18 and ABCG1 Results Bioinformatics analysis identified 462 differentially expressed genes 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). IHC, IF and Western blot analyses revealed an increased expression level of USP18 in coronary arteries from patients with coronary atherosclerotic heart disease (CHD) , but Western blot analyses revealed a decreased expression level of USP18 in coronary arteries from patients with sudden cardiac death (SCD) compared with controls. At the same time, ABCG1 expression was decreased in coronary arteries from both CHD and SCD patients with a higher significance in SCD patients. In addition, double immunofluorescence assay showed no significant co-localization of USP18 and ABCG1. Conclusions USP18 may contribute to the development of atherogenesis through regulating ABCG1-dependent cholesterol efflux from macrophages.