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TRIM65 E3 ligase targets VCAM-1 degradation to limit LPS-induced lung inflammation
Yong Li1 , Xuan Huang1,2 , Fang Guo1,3 , Tianhua Lei1 , Shitao Li4 , Paula Monaghan-Nichols1 , Zhisheng Jiang3 , Hong-Bo Xin2,* , Mingui Fu1,*
1Department of Biomedical Science, School of Medicine, University of Missouri-Kansas City, Kansas City, MO 64108, USA
2Institute of Translational Medicine, Nanchang University, Nanchang 330031, China
3Institute of Cardiovascular Diseases, Department of Pathophysiology, Hengyang Medical College, University of South China, Hengyang 421001, China
4Department of Physiological Sciences, Center for Veterinary and Health sciences, Oklahoma State University, Stillwater, OK 74078, USA
*Correspondence to:Hong-Bo Xin , Email:hongboxin@yahoo.com Mingui Fu , Email:fum@umkc.edu
J Mol Cell Biol, Volume 12, Issue 3, March 2020, 190-201,  https://doi.org/10.1093/jmcb/mjz077
Keyword: TRIM65, VCAM-1, endothelial activation, lung inflammation, ubiquitination

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 ligase of tripartite protein family, selectively targets vascular cell adhesion molecule 1 (VCAM-1) and promotes its ubiquitination 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 TNFα-induced endothelial activation, the protein levels of TRIM65 and VCAM-1 are inversely correlated. Expression of wild-type TRIM65, but not expression of a TRIM65 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 inflammation.