E3 ubiquitin ligase RNF128 promotes Lys63-linked polyubiquitination on SRB1 in macrophages and aggravates atherosclerosis

Macrophage-derived foam cell formation is the hallmark of atherosclerotic plaques prominently attributed to excessive lipid uptake and metabolic disorders. As a classic membrane-localized ubiquitin ligase, the role of RNF128 in atherosclerosis remains unknown. We discover that RNF128 is specifically expressed in macrophages of the lipid core based on single-cell RNA sequencing data and persistent hyperlipidemia induces the high expression of RNF128 in macrophages. RNF128 ablation in macrophages ameliorates atherosclerosis in both male and female mice under the background of ApoE and LDLR deficiency. Mechanistically, RNF128 directly binds to scavenger receptor B1 (SRB1), preventing its degradation through the lysosomal system and promoting oxidized low-density lipoprotein (oxLDL)-induced foam cell formation and inflammatory response in macrophages. In addition, RNF128 catalyzes Lys63-linked polyubiquitination on the cytoplasmic C-terminus of the SRB1 at lysine 478, which promotes the endosome SRB1 recycling to the cell membrane with the assistance of Rab11, instead of entering the lysosome for degradation. Macrophages play a key role in atherosclerosis through lipid uptake and inflammation. Here, the authors show that RNF128 promotes atherosclerosis by stabilizing scavenger receptor B1 (SRB1) via polyubiquitination, enhancing foam cell formation and inflammation, while its ablation reduces plaque formation in hyperlipidemic mice.