title: Lipopolysaccharides Promote S-Nitrosylation and Proteasomal Degradation of Liver Kinase B1 (LKB1) in Macrophages in Vivo.
abstract: LKB1 (liver kinase B1) plays important roles in tumor suppression, energy metabolism, and, recently, in innate immune responses. However, how LKB1 is regulated under physiological or pathological conditions is still unclear. Here, we report that LKB1 protein (but not mRNA) was decreased in both LPS-treated RAW 264.7 cells and peritoneal macrophages isolated from LPS-challenged mice. Additional LPS treatment promoted protein ubiquitination and degradation of LKB1. Pharmacological inhibition or gene silencing of inducible NOS abrogated LPS-induced LKB1 degradation, whereas exposure of RAW 264.7 cells to S-nitroso-l-glutathione, a NO donor, triggered LKB1 S-nitrosylation. Consistently, mutation of one cysteine (C430S) in LKB1 prevented LPS-induced S-nitrosylation, ubiquitination, and degradation. Moreover, S-nitrosylation and ubiquitination of LKB1 were confirmed in macrophages from LPS-challenged mice in vivo. Co-administration of the inducible NOS inhibitor S-methylisothiourea or the proteasome inhibitor MG132 prevented LPS-induced LKB1 degradation and improved the survival rate. Finally, mice lacking LKB1 in macrophages had significantly lower survival rates in response to LPS challenge compared with wild-type mice. Thus, we concluded that LKB1 is degraded by LPS treatment via S-nitrosylation-dependent proteasome pathways, and this had a protective role in LPS-induced septic shock.
authors.affiliation: From the Section of Molecular Medicine, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104.
authors.forename: Zhaoyu
authors.initials: Z
authors.lastname: Liu
authors.affiliation: From the Section of Molecular Medicine, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Dai
authors.affiliation: From the Section of Molecular Medicine, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104.
authors.forename: Huaiping
authors.initials: H
authors.lastname: Zhu
authors.affiliation: From the Section of Molecular Medicine, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104.
authors.forename: Miao
authors.initials: M
authors.lastname: Zhang
authors.affiliation: From the Section of Molecular Medicine, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104 ming-hui-zou@ouhsc.edu.
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Zou
mesh_terms: D055372:AMP-Activated Protein Kinases; D000818:Animals; D002460:Cell Line; D003545:Cysteine / Q000031:analogs & derivatives* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000201:enzymology* / Q000276:immunology; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D059748:Proteolysis; D026403:S-Nitrosothiols / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D008070:Lipopolysaccharides; D026403:S-Nitrosothiols; D009569:Nitric Oxide; C021315:S-nitrosocysteine; D017346:Protein Serine-Threonine Kinases; C491654:Stk11 protein, mouse; D055372:AMP-Activated Protein Kinases; D046988:Proteasome Endopeptidase Complex; D003545:Cysteine
keywords: S-nitrosylation; liver kinase B1 (LKB1); macrophage; nitric oxide; proteasome; shock