Characterizing purinergic receptors in the gastrointestinal epithelium and immune cells
Authors: Engevik Kristen , Hyser Joseph 
Published: May 2023

Background: Extracellular release of nucleotides (e.g., ATP, ADP, UTP, UDP) are well established as potent intercellular signaling molecules during homeostasis but are also released from cells during pathogenic microbial infection and tissue injury to serve as danger signals. These important extracellular signaling molecules activate purinergic receptors, of which there are 19 different purinergic receptor subtypes that are classified into P1 and P2 receptors. P1 receptor subtypes are activated by adenosine, while P2 receptors are differentially activated by ATP, ADP, UTP, UDP, and UP-glucose. P2 receptors are further divided into P2Y receptors (P2YRs) and P2X receptors (P2XRs) based on their structures and distinct signal-transduction mechanisms. Several studies have revealed crucial roles for P2 receptors during inflammatory and infectious diseases, yet the majority of work to date has focused on purinergic signaling in immune cells. Our group has previously identified a role for P2Y1 in mediating ADP-driven calcium waves during rotavirus infection. While purinergic signaling is a well-established mode of signaling in the enteric nervous system, the functional roles of purinergic signaling in the gastrointestinal tract remain incompletely understood. Hypothesis: Since epithelial cells serve as the first barrier against irritants and infection, we hypothesized that gut epithelium express multiple purinergic receptors that regulate cellular responses to extracellular nucleotide signals. Methods & Results: Using the Human Protein Atlas, we queried single cell RNA sequencing data for the P2 purinergic receptors. We examined these receptors along the length of the gastrointestinal tract, including esophagus, small intestine, colon, and rectum as well as in flow-sorted immune cells, peripheral blood mononuclear cells and and bone marrow derived immune cells. In silico analysis revealed high expression of P2Y1, P2Y2, P2Y11 and P2X4 among the purinergic receptors throughout the gastrointestinal tract. Interestingly, P2Y1 showed highest expression in esophageal epithelial cells, small intestinal enterocytes, and goblet cells. P2Y6 was also observed in promixal enterocytes of the small intestine, but was largely absent from the colon and rectum. In contrast, we found that immune cells from bone marrow, peripheral blood and flow sorted cells had relatively high expression of P2X1 and P2X4. We noted P2X5 expression in plasma cells and B -cells in all sets. Pathway analysis from the Reactome database revealed P2Y receptors are associated with signal transduction, metabolism and hemostasis pathways, while P2X receptors were primarily involved in immune response and infectious disease pathways. Conclusions: These findings confirm that the gastrointestinal tract possess robust P2Y1, P2Y2, P2Y11 and P2X4 receptor expression and can participate in purinergic signaling pathways. R01 DK115507 (Hyser); R01 AI158683 (Hyser); APS Postdoctoral Fellowship (Engevik); F32 DK130288 (Engevik) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.