Food-Derived l -tryptophan and α-Casein (90–95) Differentially Potentiate Porcine Calcium-Sensing Receptor Signaling and Improve Enteroendocrine–Epithelial Responses Under Peptidoglycan Challenge

Abstract

Abstract The calcium-sensing receptor (CaSR) is a nutrient-sensing class C G protein-coupled receptor implicated in intestinal hormone release, yet the signaling pharmacology of the porcine receptor and its relevance to epithelial homeostasis remain poorly defined. Here, a stable Flp-In-293 reporter platform expressing porcine CaSR was combined with structure-based docking, molecular dynamics simulations, secretin tumor cell line-1 (STC-1) enteroendocrine assays, and an STC-1/IPEC-J2 co-culture system challenged with peptidoglycan. Extracellular Ca2+ activated porcine CaSR through NFAT, SRE, SRF, and cAMP readouts, whereas l-tryptophan and α-casein (90–95) differentially potentiated Ca2+-dependent signaling and docked within the extracellular Venus flytrap domain. Both ligands stimulated CaSR-sensitive glucagon-like peptide-1 (GLP-1) secretion and recruited ERK1/2, IP1, and cAMP signaling. In co-culture, ligand exposure attenuated inflammatory transcription, preserved selected transporter and tight-junction programs, and improved barrier function under peptidoglycan challenge. Together, these data identify food-derived ligands that couple porcine CaSR signaling to enteroendocrine–epithelial responses.