ADP-ribosylation in the innate immune response

Authors

• CM Daniels
• J Sun
• R Gottschalk
• A Nuccio
• NP Manes
• I Fraser
• A Nita-Lazar

Abstract

ADP-ribosylation is a post-translational modification (PTM) important for DNA repair and inflammatory signaling. While inhibition of poly(ADP-ribose) polymerases (PARPs) – the enzymes responsible for ADP-ribosylation – is known to protect animal models from sepsis, the molecular mechanisms behind this response are unknown. In order to investigate the role of this PTM in the innate immune response, we have characterized ADP-ribosylation in macrophages, both before and after activation by lipopolysaccharide (LPS). The macrophage ADP-ribosylated proteome changes in response to LPS treatment, which we have shown by western blot and mass spectrometry, for both human and mouse cells – this dataset represents the first draft of the macrophage PARylated proteome. Furthermore, we have shown by both fluorescent microscopy and Cytometric Bead Array technology that NFkB and the cytokines associated with its activation are altered in response to PARP inhibition, an effect which is dramatized by macrophage activation with LPS. Finally, we have shown that TLR4 is ADP-ribosylated on its TIR domain, an otherwise unknown modification on an important regulatory domain for all TLR signaling. The presence of this modification site, the importance of TLR4 signaling in sepsis pathogenesis, and the protective effect of PARP inhibition against sepsis, suggests that ADP-ribosylation may be a major player in TLR4 signaling. Our dataset represents the first proteome-wide assessment of both human and mouse macrophage ADP-ribosylation, and implicates PARP biology in the early innate immune response.

Scientific Focus Area: Systems Biology

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