TRIM13 reduces cholesterol efflux and increases oxidized LDL uptake leading to foam cell formation and atherosclerosis

Accumulation of lipids within the arterial wall is the key initiating event in the development of atherosclerosis. Impaired cholesterol efflux and/or uptake can influence arterial lipid accumulation. Here, we report that tripartite motif-containing protein 13 (TRIM13), a RING-type E3 ubiquitin ligase, plays a role in arterial lipid accumulation leading to atherosclerosis. Using molecular approaches and knockout mouse model, we found that TRIM13 expression was induced both in the aorta and peritoneal macrophages (pMφ) of ApoE-/- mice in response to western diet (WD) in vivo. Furthermore, proatherogenic cytokine IL-1β also induced TRIM13 expression both in pMφ and vascular smooth muscle cells (VSMCs). Furthermore, we found that TRIM13 via ubiquitination and degradation of LXRα/β downregulates the expression of their target genes ABCA1/G1 and thereby inhibits cholesterol efflux. In addition, TRIM13 by ubiquitinating and degrading SOCS1/3 mediates STAT1 activation, CD36 expression and foam cell formation. In line with these observations, genetic deletion of TRIM13 by rescuing cholesterol efflux and inhibiting foam cell formation protects against diet-induced atherosclerosis. We also found that while TRIM13 and CD36 levels were increased, LXRα/β, ABCA1/G1 and SOCS3 levels were decreased both in Mφ and SMCs of stenotic human coronary arteries as compared to non-stenotic arteries. More intriguingly, the expression levels of TRIM13 and its downstream signaling molecules were correlated with the severity of stenotic lesions. Together, these observations reveal for the first time that TRIM13 plays a crucial role in diet-induced atherosclerosis, and that it could be a potential drug target against this vascular lesion.