Hypusination regulates the antibacterial response of macrophages

Abstract

Abstract Introduction Hypusine is an amino acid found only in the eukaryotic translation initiation factor 5A (EIF5A). Hypusine is synthesized by the enzyme deoxyhypusine synthase (DHPS) that transfers the N-moiety of spermidine to a lysine residue in EIF5A. This post-translational modification (hypusination) is essential to binding specific mRNAs. The EIF5AHyp/mRNA complex is translocated to the cytoplasm, reaches ribosomes, and allows for translation. We analyzed the role of hypusination in the innate response of macrophages. Results The gastric pathogen Helicobacter pylori stimulated DHPS expression and hypusination in murine bone marrow-derived macrophages (BMmacs). We generated myeloid-specific Dhps knockout mice (DhpsΔmye) by crossing Dhpsfl/fl mice to Lyz2-cre mice. By iTRAQ proteomics, 29 of the proteins induced by H. pylori in BMmacs from Dhpsfl/fl mice were significantly less expressed in infected DhpsΔmye mice. These included antibacterial effectors (IRG1, NOS2), cytokines (TNF-α, IL-1β), and mediators of autophagy (SQSTM, IRGM1). These findings were confirmed by Western blot. DhpsΔmye mice infected with H. pylori exhibited increased colonization (p<0.01) and gastritis (p<0.05) compared to Dhpsfl/fl mice. DhpsΔmye mice were also more colonized by the intestinal pathogen Citrobacter rodentium than Dhpsfl/fl mice (p<0.05). EIF5AHyp and NOS2 were more expressed in gastric and colonic CD68+ macrophages from H. pylori- and C. rodentium-infected Dhpsfl/fl mice versus uninfected animals, respectively. The staining for EIF5AHyp and NOS2 was markedly reduced in infected DhpsΔmye mice. Conclusions Hypusination in myeloid cells is critical for host innate immunity to limit the infectivity of pathogenic bacteria.