TRIM65 E3 ligase targets VCAM-1 degradation to limit LPS-induced lung inflammation

Although the adhesion molecules-mediated leukocyte adherence and infiltration into tissues is an important step of inflammation,the post-translational regulation of these proteins on the endothelial cells is poorly understood.Here,we report that TRIM65,an ubiquitin E3 iigase of tripartite protein family,selectively targets vascular cell adhesion molecule 1(VCAM-1)and promotes its ubiq-uitination and degradation,by which it critically controls the duration and magnitude of sepsis-induced pulmonary inflammation.TRIM65 is constitutively expressed in human vascular endothelial cells.During TNFa-induced endothelial activation,the protein levels ofTRIM65 and VCAM-1 are inversely correlated.Expression of wild-type TRIM65,but not expression of aTRIM65 mutant that lacks E3 ubiquitin ligase function in endothelial cells,promotes VCAM-1 ubiquitination and degradation,whereas small interference RNA-mediated knockdown of TRIM65 attenuates VCAM-1 protein degradation.Further experiments show that TRIM65 directly interacts with VCAM-1 protein and directs its polyubiquitination,by which TRIM65 controls monocyte adherence and infiltration into tissues during inflammation.Importantly,TRIM65-deficient mice are more sensitive to lipopolysaccharide-induced death,due to sustained and severe pulmonary inflammation.Taken together,our studies suggest that TRIM65-mediated degradation of VCAM-1 represents a potential mechanism that controls the duration and magnitude of infiammation.