Project Grant F32DK139628

F32 - BITTER CHEMOSENSATION FROM GUT TO BRAIN - PROJECT SUMMARY/ABSTRACT A SUBSTANTIAL PART OF OUR DIET AND HEALTH REGIME INVOLVES BITTER FOOD AND MEDICINE. BITTER MOLECULES BIND BITTER TASTE RECEPTORS (TAS2RS) AND ACTIVATE A SENSORY PATHWAY THAT ELICITS AN AVERSIVE TASTE SENSATION IN THE ORAL CAVITY, MAINLY TO AVOID INGESTION OF TOXINS. TAS2RS ARE ALSO FOUND THROUGHOUT THE DIGESTIVE TRACT, AND BITTER STIMULI IN THE GUT AECT FEEDING BEHAVIOR THROUGH GUT PEPTIDE SECRETION AND STIMULATION OF SENSORY REGIONS IN THE BRAIN THROUGH THE VAGUS NERVE. YET, IT REMAINS TO BE DETERMINED HOW SENSORY SIGNALING FROM INGESTED BITTER MOLECULES ARE TRANSDUCED FROM GUT TO BRAIN. OUR LAB DISCOVERED A POPULATION OF SPECIALIZED GUT ENTEROENDOCRINE CELLS, CALLED NEUROPOD CELLS, THAT DETECT LUMINAL NUTRIENTS IN THROUGH APICAL SENSORS AND TRANSDUCE SENSORY SIGNALS TO THE BRAIN IN MILLISECONDS, VIA THE VAGUS NERVE. THIS GUT SENSORY PATHWAY REGULATES FEEDING BEHAVIOR IN REAL-TIME. THE HYPOTHESIS OF THIS APPLICATION IS THAT NEUROPOD CELLS DETECT BITTER SIGNALS THROUGH TAS2RS AND TRANSDUCE THEM ONTO VAGAL NEURONS. PRELIMINARY NDINGS SHOW THAT ISOLATED SMALL INTESTINAL NEUROPOD CELLS ARE ENRICHED FOR A SUBSET OF MURINE TAS2RS, COMPARED TO ALL OTHER INTESTINAL EPITHELIAL CELLS. EXPRESSION OF THESE TAS2RS IS DYNAMIC, AS IT DECREASES IN RESPONSE TO BACTERIAL ENDOTOXINS. THEREFORE, NEUROPOD CELLS MAY ACT AS GUT SENSORS FOR BITTER COMPOUNDS TO COMMUNICATE THE VALENCE OF BITTER MOLECULES, WHICH RANGE FROM TOXIC TO MEDICINAL. SPECIC AIM 1 WILL DETERMINE WHETHER NEUROPOD CELLS ARE ACTIVATED BY BITTER STIMULI THROUGH TAS2R SIGNALING. EXPRESSION OF TAS2RS AND THEIR SIGNALING MOLECULES WILL BE CHARACTERIZED THROUGHOUT THE GUT AND ACTIVATION OF NEUROPOD CELLS IN RESPONSE TO BITTER MOLECULES WILL BE DETERMINED BY CALCIUM IMAGING. THE REQUIREMENT OF TAS2RS FOR BITTER SIGNALING IN NEUROPOD CELLS WILL BE DETERMINED THROUGH TARGETED KNOCKOUTS OF TAS2RS. SPECIC AIM 2 WILL DETERMINE WHETHER NEUROPOD CELLS SIGNAL LUMINAL BITTER STIMULI ONTO VAGAL NEURONS. THE SIGNALING MOLECULE WILL BE IDENTIED BY RELEASE ASSAYS IN INTESTINAL ORGANOIDS AND SINGLE NEUROPOD CELLS IN RESPONSE TO BITTER MOLECULES, AND THE SENSORY PATHWAY WILL BE DETERMINED BY MEASURING VAGAL ACTIVATION BY ELECTROPHYSIOLOGY, IN RESPONSE TO GUT INFUSIONS OF BITTER MOLECULES. FINALLY, PHARMACOLOGICAL AND OPTOGENETIC INHIBITION APPROACHES WILL DETERMINE THE REQUIREMENT OF NEUROPOD CELL SIGNALING FOR THIS SENSORY PATHWAY. THIS WORK WILL UNCOVER HOW BITTER STIMULI IN THE GUT ARE CONVEYED TO THE BRAIN, BRINGING FORTH A NEW ASPECT OF CHEMOSENSATION AND GUT-BRAIN COMMUNICATION FOR A VARIETY OF FOODS AND MEDICINE THAT ARE ESSENTIAL FOR OUR HEALTH.