Design and synthesis of a new environmentally sensitive small-molecule fluorescent probe for MRGPRX2

MAS-related G protein-coupled receptor X2 (MRGPRX2) is a key target receptor and an important drug target for triggering pseudo-allergic reactions. Studying its ligands will help to understand the mechanism of pseudo-allergic reactions and discover anti-allergic drugs. Small-molecule fluorescent probes are widely used to study the localization of G protein-coupled receptors (GPCRs) on the cell membrane, the transport and internalization of GPCRs, and the interaction between receptors and ligands due to their high selectivity, sensitivity and safety. MRGPRX2 is one of GPCRs with an active hydrophobic ligand binding domain, so designing small-molecule fluorescent probes with environmental sensitivity is very important for the study of MRGPRX2 ligands and the visualization of this receptor. In this study, we selected the agonist of MRGPRX2 (R)-ZINC-3573 as the recognition group and used different fluorophore skeleton structures as the luminescent group to synthesize a series of small-molecule fluorescent probes targeting MRGPRX2. Among them, PoX2-B with BODIPY FL as the fluorescent group had good photostability and environmentally sensitive properties to the hydrophobic ligand binding domain of MRGPRX2, and could be used for living cell imaging. Furthermore, PoX2-B could specifically recognize MRGPRX2, and it was expected to be used to screen effective ligands of MRGPRX2 in the future, so as to play a role in the development of anti-allergy drugs and the pathogenesis of allergic diseases.