Inflammatory bowel diseases (IBD), including Crohn’s disease (CD), remain a significant clinical challenge with increasing prevalence, affecting millions worldwide despite recent therapeutic advances. Loss-of-function polymorphisms in the Nod2 gene are strongly associated with CD, which has long created a conundrum as NOD2 is a cytosolic innate immune receptor that senses small fragments of the bacterial cell wall (muropeptides) and triggers an inflammatory response. Several non-exclusive explanations for this conundrum have been proposed in the literature, including altered TLR signaling, reduced antimicrobial peptide production, or altered barrier function in the gut in the absence of Nod2. All of these reported changes may contribute to the microbial dysbiosis observed in mouse models and patients with alterations in Nod2. While it is clear that NOD2 protects against colitis through some or all of these reported pathways, the mechanisms by which muropeptides, like the NOD2 agonist MDP, transit from the gut lumen to cytosolic NOD2 are unclear. Emerging evidence from studies of skin and skin keratinocytes suggests that solute carrier (SLC) transport proteins, especially the SLC46 family, mediate the internalization of MDP and other muropeptides, although this hypothesis has not yet been examined in the gut epithelia or macrophages. Here, we propose to examine the role of the SLC46A3 transporter in facilitating MDP transport and subsequent NOD2 activation, with implications for IBD. Preliminary data from murine colitis models show that Slc46a3 knockout mice exhibit increased susceptibility to colitis, resembling the pathology seen in Nod2-deficient animals. This suggests a critical role for SLC46A3 in NOD2 signaling and gut homeostasis. In this exploratory R21 proposal, we will investigate the role of the SLC46A3/NOD2 axis in the context of MDP transport, sensing and mouse models of IBD.