RUVBL1/2 Complex Regulates Pro-Inflammatory Responses in Macrophages via Regulating Histone H3K4 Trimethylation.

Rui Zhang,Ah Ra Lee,Larry M C Chow,Yixiang Wang,Sheng Chen,Chris Y Cheung,Woon Yong Kwon,Bill Kwan-Wai Chan,Mary P Chau,Ben C B Ko,Sang-Uk Seo,Koon Ho Wong,Hang Liu,Lakhansing Pardeshi,Kenneth Wong,Richard K W Choy

doi:10.3389/fimmu.2021.679184

Abstract

Macrophages play an important role in the host defense mechanism. In response to infection, macrophages activate a genetic program of pro-inflammatory response to kill any invading pathogen, and initiate an adaptive immune response. We have identified RUVBL2 - an ATP-binding protein belonging to the AAA+ (ATPase associated with diverse cellular activities) superfamily of ATPases - as a novel regulator in pro-inflammatory response of macrophages. Gene knockdown of Ruvbl2, or pharmacological inhibition of RUVBL1/2 activity, compromises type-2 nitric oxide synthase (Nos2) gene expression, nitric oxide production and anti-bacterial activity of mouse macrophages in response to lipopolysaccharides (LPS). RUVBL1/2 inhibitor similarly inhibits pro-inflammatory response in human monocytes, suggesting functional conservation of RUVBL1/2 in humans. Transcriptome analysis further revealed that major LPS-induced pro-inflammatory pathways in macrophages are regulated in a RUVBL1/2-dependent manner. Furthermore, RUVBL1/2 inhibition significantly reduced the level of histone H3K4me3 at the promoter region of Nos2 and Il6, two prototypical pro-inflammatory genes, and diminished the recruitment of NF-kappaB to the corresponding enhancers. Our study reveals RUVBL1/2 as an integral component of macrophage pro-inflammatory responses through epigenetic regulations, and the therapeutic potentials of RUVBL1/2 inhibitors in the treatment of diseases caused by aberrant activation of pro-inflammatory pathways.

Highlights

Macrophages are innate immune cells that play a central role in host defense against pathogens
LPS (10 ng/ml) treatment resulted in an 800-fold increase in Nos2 expression in the siControl transfected mouse macrophages, whereas Nos2 induction was significantly reduced in the cells transfected with SP-siRuvbl2 or individual siRNAs (Figure 1B)
We found that gene knockdown of Ruvbl1 (Figure 1D, left) resulted in significant reduction of both LPS-induced Nos2 expression (Figure 1D, middle) and nitric oxide (NO) production (Figure 1D, right), suggesting that RUVBL2 works together with RUVBL1 in this context

Summary

Introduction

Macrophages are innate immune cells that play a central role in host defense against pathogens. They are involved in tissue homeostasis, tissue repair, and disease pathogenesis Among other functions, they sense invading pathogens and respond swiftly via induction of pro-inflammatory response characterized by the release of anti-microbial mediators including nitric oxide (NO), chemokines (CXCL8, CXCL10, CCL3, CCL4, and CCL5) and pro-informatory cytokines (IL-1 beta, IL-6, and TNF-alpha) respectively. RUVBL1 and RUVBL2 (RUVBL1/2) are involved in diverse cellular processes They regulate transcription by modulating the transcriptional activities of MYC and b-catenin [4, 5], and act as a component of chromatin remodeling complexes TIP60, INO80, and SWR1, all of which regulates DNA damage response and chromatin remodeling [6,7,8,9]. They are an integral component of the R2TP/Prefoldin-like cochaperone complex involved in the assembly of protein complexes including snoRNPs, RNA polymerase, telomerase, and members of the phosphatidylinositol 3-kinase-related protein kinase (PIKK) family [10]

Methods

Results

Conclusion