It Takes Two: Understanding the Role of Protein‐protein Interaction in the Regulation of an Innate Immune Receptor

Nucleotide‐binding oligomerization domain‐containing protein 2 (NOD2) is an intracellular innate immune receptor expressed in epithelial cells and macrophages. NOD2 is activated and stabilized upon binding the peptidoglycan fragment muramyl dipeptide (MDP). The binding process initiates an innate immune response leading to the release of proinflammatory molecules via the activation of transcription factors including NF‐kB pathway. Three Single‐nucleotide polymorphisms of NOD2 are correlated with an increased susceptibility to Crohn's disease, one of the known forms of Inflammatory bowel diseases (IBD). NOD2 CD variants are inherently unstable; however, stability can be rescued by overexpressing NOD2 interacting partner, HSP70 and through thiamet G induced increase of global O ‐GlcNAc level. This study is focused on identifying O ‐GlcNAc sites of NOD2, revealing other binding partners, and understanding how these processes, guide NOD2 regulation. In working towards this goal, mass spectrometry and co‐immunoprecipitation experiments were performed to identify O ‐GlcNAc modification site and a novel interacting partner of NOD2 respectively. Initial data obtained demonstrated that OGT is a novel binding partner of NOD2, in complex with HSP70 and guides OGT to the NOD2 substrate. Interestingly, the data suggest the complex is changed upon NOD2 engagement with peptidoglycan fragment, MDP. This highlights that there are multiple control mechanisms involved in NOD2 regulation. Future work will investigate the position of OGT and HSP70 binding on NOD2.