The 11S Proteasome Subunit PSME3 Is a Positive Feedforward Regulator of NF-κB and Important for Host Defense against Bacterial Pathogens

“…Overexpression of AX2R might mutate these phosphodegron motifs, abolishing the degradation and ubiquitination of KLF2 [23, 30]. Although studies have shown that KLF2 mRNA expression is regulated by various signals, including stress, growth factors and cytokines in endothelial cells, the mechanism that regulates KLF2 abundance at the posttranslational level has remained largely unknown [31, 32]. How KLF2 protein stability is regulated in endothelial cells has also remained unknown.…”

Section: Discussionmentioning

confidence: 99%

Overexpression of Annexin A2 Receptor Inhibits Neovascularization via the Promotion of Krüppel-Like Transcription Factor 2

Guo

Song

Zhao

et al. 2018

Cell Physiol Biochem

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Background/Aims: Annexin A2 receptor (AX2R) can mediate annexin A2 signalling and induce apoptosis in a variety of cells, but its role in neovascularization (NV) remains unclear. Krüppel-like transcription factor 2 (KLF2) is known to be expressed in a range of cell types and to participate in a number of processes during development and disease, such as endothelial homeostasis, vasoregulation and vascular growth/remodelling. The aim of our study was to investigate the role of AX2R in NV and the plausible molecular mechanism. Methods: We constructed a eukaryotic overexpression plasmid for AX2R (Lenti-AX2R) by using polymerase chain reaction (PCR). The full-length human AX2R gene was transfected into human retinal endothelial cells (HRECs) and human umbilical vein endothelial cells (HUVECs) using lentivirus vectors to overexpress AX2R. All experiments were divided into three groups: control, negative control (Lenti-EGFP), and Lenti-AX2R.Cell proliferation, cell migration, tube formation, mouse aortic ring assays and mouse matrigel plug assay were applied to analyse the effect of AX2R in NV. Furthermore, we conducted flow cytometry to evaluate whether AX2R could influence the cell cycle. A series of cell cycle-related proteins including cyclin A1, cyclin B1, cyclin D1, cyclin E1, CDK1, and p-CDC2 were detected by WB. The mRNA and protein levels of KLF2, vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor 2 (VEGFR2) were further quantified by RT-PCR and WB to reveal the possible mechanism. Results: Overexpression of AX2R significantly inhibited cell proliferation, migration and tube formation in both types of endothelial cells (ECs), HRECs and HUVECs. It also suppressed vessel sprouting in the mouse aortic ring assay and NV in mouse matrigel plug assay. Furthermore, infection with Lenti-AX2R lentivirus arrested the cell cycle in S/G2 and influenced the expression of a series of cell cycle-related proteins. We also found that the overexpression of AX2R increased the expression of KLF2, mediating VEGF and VEGFR2. Conclusions: Overexpression of AX2R contributes to the inhibition of NV via suppressing KLF2 ubiquitin-dependent protein degradation, which might therefore be a therapeutic option for NV. It could be considered more broadly as an anti-angiogenic agent in the treatment of neovascular-related diseases in the future.

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“…Mouse PMs were prepared in our laboratory following procedure described previously. 25 In brief, C57BL/6 J or ICER knockout mice and littermates were injected with 3% sterile thioglycollate (Sigma, St. Louis, MO, USA) intraperitoneally (3 ml per mouse). After 3 days, mice were euthanized, and RPMI medium was injected intraperitoneally and then retrieved.…”

Section: Discussionmentioning

confidence: 99%

A negative feedback loop of ICER and NF-κB regulates TLR signaling in innate immune responses

Qiu

et al. 2016

Cell Death Differ

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The NF-κB pathway has important roles in innate immune responses and its regulation is critical to maintain immune homeostasis. Here, we report a newly discovered feedback mechanism for the regulation of this pathway by TLR ligands in macrophages. Lipopolysaccharide (LPS) induced the expression of ICER via p38-mediated activation of CREB in macrophages. ICER, in turn, inhibited the transcriptional activity of NF-κB by direct interaction with the p65 subunit of NF-κB. Deficiency in ICER elevated binding of NF-κB to promoters of pro-inflammatory genes and their subsequent gene expression. Mice deficient in ICER were hypersensitive to LPS-induced endotoxic shock and showed propagated inflammation. Whereas ICER expression in ICER KO bone marrow transplanted mice rescued the ultra-inflammation phenotype, expression of a p65 binding-deficient ICER mutant failed to do so. Our results thus establish p38-CREB-ICER as key components of a negative feedback mechanism necessary to regulate TLR-driven inflammation. Cell Death and Differentiation (2017) 24, 492-499; doi:10.1038/cdd.2016; published online 23 December 2016Activation of TLR4, a pattern recognition receptor used in the innate immune system, by lipopolysaccharide (LPS) leads to the transcription of pro-inflammatory mediators that promote innate immune responses.1 One critical pathway triggered by TLR4 is the NF-κB pathway.2 TLR4 initiates a signaling cascade through adapter molecules MyD88 and TRIF, resulting in TRAF6 activation. TRAF6 in turn triggers the phosphorylation of IκB by IKK and proteosomal degradation of IκB. Subsequently, NF-κB disassociates from IκB and translocates to the nucleus where it promotes the transcription of genes involved in pro-inflammatory responses.3,4 Activation of TRAF6 also leads to downstream activation of the MAPK cascade, including JNKs and p38 isoforms. 5 The p38 pathway has attracted considerable interest as a possible target for antiinflammatory drugs. Activation of p38 results in the activation of CREB, a transcription factor that regulates diverse cellular responses including proliferation, survival and immune responses. CREB is phosphorylated and activated by MSK1/2, a downstream kinase of p38, and subsequently mediates the transcription of genes containing a cAMP-responsive element. Several anti-inflammatory genes possess this cAMPresponsive element, including Dusp1 and IL-10. 6 In addition, phosphorylated CREB has been proposed to directly inhibit NF-κB activation by blocking the binding of CREB binding protein to the NF-κB complex, thereby limiting proinflammatory responses. 7Inducible cAMP early repressors (ICERs) are members of the cAMP-response element (CRE) modulator family and are induced by CREB.8 ICER is transcribed via an alternative internal promoter in the CREM gene and consists of four different isoforms generated by alternative splicing of its transcript (ICERI, ICERIγ, ICERII, ICERIIγ). 9 The isoforms encode either CREB-like (ICERI) or CREM-like (ICERII) DNA-binding domains (DBDs) with or without the alternat...

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The 11S Proteasome Subunit PSME3 Is a Positive Feedforward Regulator of NF-κB and Important for Host Defense against Bacterial Pathogens

Cited by 37 publications

References 57 publications

p38 inhibition provides anti–DNA virus immunity by regulation of USP21 phosphorylation and STING activation

p38 inhibition provides anti–DNA virus immunity by regulation of USP21 phosphorylation and STING activation

Overexpression of Annexin A2 Receptor Inhibits Neovascularization via the Promotion of Krüppel-Like Transcription Factor 2

A negative feedback loop of ICER and NF-κB regulates TLR signaling in innate immune responses

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