Lipopolysaccharides Promote S-Nitrosylation and Proteasomal Degradation of Liver Kinase B1 (LKB1) in Macrophages in Vivo

Liu, Zhaoyu; Dai, Xiaoyan; Zhu, Huaqing; Zhang, Miao; Zou, Ming

doi:10.1074/jbc.m115.649210

Cited by 21 publications

(17 citation statements)

References 34 publications

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“…OxLDL is known to induce iNOS expression in macrophages 28, 29 , and we had previously found that NO-mediated s-nitrosylation could promote LKB1 degradation 30 . Thus, we first tested if OxLDL differentially induces iNOS expression in macrophages versus vascular smooth muscle cells.…”

Section: Resultsmentioning

confidence: 97%

“…We found that OxLDL can robustly induce iNOS expression in macrophages, which is consistent with a previous report 29 , however, we cannot detect iNOS expression in VSMCs after OxLDL exposure (Supplemental Fig 2). We have previously found that NO-mediated s-nitrosylation promotes LKB1 degradation 30 . It is thus possible that OxLDL-induced iNOS expression in macrophages may promote LKB1 degradation through s-nitrosylation, whereas VSMCs, which lack iNOS expression, undergo no such effect.…”

Section: Discussionmentioning

confidence: 99%

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Macrophage Liver Kinase B1 Inhibits Foam Cell Formation and Atherosclerosis

Liu

Zhu

Dai

et al. 2017

Circulation Research

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Rationale Liver kinase B1 (LKB1) is a serine/threonine kinase and tumor suppressor, which regulates the homeostasis of hematopoietic cells and immune responses. Macrophages transform into foam cells upon taking-in lipids. No role for LKB1 in foam cell formation has previously reported. Objective We sought to establish the role of LKB1 in atherosclerotic foam cell formation. Methods and Results LKB1 expression was examined in human carotid atherosclerotic plaques and in western diet fed atherosclerosis-prone Ldlr−/− and ApoE−/− mice. LKB1 expression was markedly reduced in human plaques when compared to non-atherosclerotic vessels. Consistently, time-dependent reduction of LKB1 levels occurred in atherosclerotic lesions in western diet fed Ldlr−/− and ApoE−/− mice. Exposure of macrophages to oxidized LDL downregulated LKB1 in vitro. Furthermore, LKB1 deficiency in macrophages significantly increased the expression of scavenger receptor A (SRA), modified LDL uptake and foam cell formation, all of which were abolished by blocking SRA. Further, we found LKB1 phosphorylates SRA resulting in its lysosome degradation. To further investigate the role of macrophage LKB1 in vivo, ApoE−/−LKB1fl/flLysMcre and ApoE−/−LKB1fl/fl mice were fed with western diet for 16 weeks. Compared to ApoE−/−LKB1fl/fl wild type control, ApoE−/−LKB1fl/flLysMcre mice developed more atherosclerotic lesions in whole aorta and aortic root area, with markedly increased SRA expression in aortic root lesions. Conclusions We conclude that macrophage LKB1 reduction caused by oxidized LDL promotes foam cell formation and the progression of atherosclerosis.

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Section: Resultsmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Macrophage Liver Kinase B1 Inhibits Foam Cell Formation and Atherosclerosis

Liu

Zhu

Dai

et al. 2017

Circulation Research

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“…NO-stimulated protein degradation occurs for several non-P450 proteins, such as iron regulatory protein 2 (IRP2) [33], insulin receptor substrate (IRS) -1 and -2 proteins [34][35], mouse double minute 2 homolog (Mdm2) [36], O 6 -alkylguanine-DNA alkyltransferase [37], serine/threonine-protein kinase STK11 [38], cyclin-dependent kinase 5 [39], and caspase 8 inhibitory protein [40]. In the case of IRP2, opposite effects have been reported.…”

Section: Discussionmentioning

confidence: 99%

Nitric oxide-regulated proteolysis of human CYP2B6 via the ubiquitin-proteasome system

Lee

Tripathi

Morgan

2017

Free Radical Biology and Medicine

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We showed previously that rat cytochrome P450 CYP2B1 undergoes NO-dependent proteasomal degradation in response to inflammatory stimuli, and that the related human enzyme CYP2B6 is also down-regulated by NO in primary human hepatocytes. To investigate the mechanism of CYP2B6 down-regulation, we made several cell lines (HeLa and HuH7 cells) in which native CYP2B6 or CYP2B6 with a C-terminal V5 tag (CYP2B6V5) are expressed from a lentiviral vector with a cytomegalovirus promoter. Native CYP2B6 protein was rapidly down-regulated in HeLa cells within 3 h of treatment with the NO donor (Z)-1-[2-(2-Aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate, while its mRNA level was not down-regulated. Treatment of the cells with the NO donor (Z)-1-[N-(3-aminopropyl)-N-(3-ammoniopropyl)amino]diazen-1-ium-1,2-diolate also resulted in rapid down-regulation of CYP2B6 activity, measured as the formation of 7-hydroxy-4-trifluoromethylcoumarin, as well as 2B6 protein in the CYP2B6 HeLa cell line. CYP2B6V5 was also down-regulated by NO donors in HuH7 cells. Down-regulation was observed in the presence of cycloheximide, demonstrating that this occurs via a post-translational mechanism. We generated a HeLa cell line expressing both CYP2B6V5 and human nitric oxide synthase 2 (NOS2), the latter under positive control by tetracycline. The cellular NO produced by doxycycline treatment also effectively down-regulated CYP2B6 protein, which was blocked by the co-treatment with the NOS2 competitive inhibitor L-NG-nitroarginine methyl ester (L-NAME). We next investigated the proteolytic enzymes responsible for NO-dependent CYP2B6 degradation. Neither calpain inhibitors (N-Acetyl-L-leucyl-L-leucyl-L-norleucinal, carbobenzoxy-valinyl-phenylalaninal), nor lysosomal protease inhibitors (3-methyladenine and chloroquine) inhibited the NO dependent CYP2B6V5 down-regulation. The proteasome inhibitors MG132 and bortezomib attenuated, but did not completely block the NO-induced down-regulation in the HuH7 cell line. However, when cells were co-treated with NO donor and proteasome inhibitors, high molecular mass species could be detected on native CYP2B6 as well as CYP2B6V5 Western blots. Further investigation demonstrated that CYP2B6 protein was polyubiquitinated and this was dramatically enhanced by co-treatment with NO donor and bortezomib. Taken together, our data demonstrate that CYP2B6 is down-regulated in an NO-dependent manner via ubiquitination and proteasomal degradation.

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“…LPS induces degradation of programmed cell death protein 4 (PDCD4) in a mammalian target of rapamycin signaling–dependent manner, which leads to an increased IL‐10 level (44). Liu et al (45) demonstrated that LPS accelerates liver kinase B1 decay by S‐nitrosylation–dependent proteasome pathways. Our results support the transcriptional control of Nrp1 by LPS in macrophages.…”

Section: Discussionmentioning

confidence: 99%

A novel role for myeloid cell‐specific neuropilin 1 in mitigating sepsis

et al. 2017

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Sepsis-typically caused by an uncontrolled and amplified host systemic inflammatory response to microbial infection-is a life-threatening complex clinical disorder and remains a major cause of infection-related deaths in the intensive care unit. Emerging evidence suggests that neuropilin 1 (Nrp1), an originally defined coreceptor for class 3 semaphorins and VEGF, plays important roles in the immune system; however, the function and regulation of macrophage Nrp1 in host immune defense against bacterial infection remain unknown. To address this problem, we generated myeloid cell-specific Nrp1-knockout (Nrp1) mice and applied 2 stringent animal models of sepsis: cecal ligation and puncture as well as intraperitoneal injection of LPS. Here, we reported that myeloid cell-specific Nrp1-deficient mice exhibited enhanced susceptibility to cecal ligation and puncture- and LPS-induced sepsis, which correlated with significantly decreased survival rates and heightened levels of proinflammatory cytokines in both peritoneal lavage and serum. Mechanistically, LPS specifically attenuated the expression of Nrp1 in macrophages, which was mediated by TLR4-NF-κB p50 and -65 pathways. By using isolated primary macrophages, loss of Nrp1 consistently resulted in increased production of proinflammatory cytokines, including iNOS, TNF-α, and IL-6. Together, these findings demonstrate a novel role of macrophage Nrp1 in sepsis.-Dai, X. Okon, I., Liu, Z., Wu, Y., Zhu, H., Song, P., Zou, M.-H. A novel role for myeloid cell-specific neuropilin 1 in mitigating sepsis.

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Lipopolysaccharides Promote S-Nitrosylation and Proteasomal Degradation of Liver Kinase B1 (LKB1) in Macrophages in Vivo

Cited by 21 publications

References 34 publications

Macrophage Liver Kinase B1 Inhibits Foam Cell Formation and Atherosclerosis

Macrophage Liver Kinase B1 Inhibits Foam Cell Formation and Atherosclerosis

Nitric oxide-regulated proteolysis of human CYP2B6 via the ubiquitin-proteasome system

A novel role for myeloid cell‐specific neuropilin 1 in mitigating sepsis

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