In silico design of novel probes for the atypical opioid receptor MRGPRX2

Abstract

The primate-exclusive MRGPRX2 G protein-coupled receptor (GPCR) has been suggested to modulate pain and itch. Despite putative peptide and small molecule MRGPRX2 agonists, selective nanomolar potency probes have not yet been reported. To identify a MRGPRX2 probe, we first screened 5,695 small molecules and found many opioid compounds activated MRGPRX2, including (−)- and (+)-morphine, hydrocodone, sinomenine, dextromethorphan and the prodynorphin-derived peptides, dynorphin A, dynorphin B, and α- and β-neoendorphin. We used these to select for mutagenesis-validated homology models and docked almost 4 million small molecules. From this docking, we predicted ZINC-3573, which represents a potent MRGPRX2-selective agonist, showing little activity against 315 other GPCRs and 97 representative kinases, and an essentially inactive enantiomer. ZINC-3573 activates endogenous MRGPRX2 in a human mast cell line inducing degranulation and calcium release. MRGPRX2 is a unique atypical opioid-like receptor important for modulating mast cell degranulation, which can now be specifically modulated with ZINC-3573.

Discovery of new GPCR ligands to illuminate new biology

“…A similar screen has suggested that the oGPCR MRGPRX2 is an atypical opioid receptor, responding to drugs like morphine, codeine, and dextromethorphan, as well as to the endogenous opioid peptide dynorphin 44 . MRGPRX2 is expressed in mast cells and sensory neurons, consistent with its role as an opioid itch receptor.…”

“…In our own lab, the platform has been used to screen for ligands that illuminate the function of orphan and understudied GPCRs (oGPCRs) 40 , such as MRGPRX2 (ref. 44). …”

How Ligands Illuminate GPCR Molecular Pharmacology

“…One GPR68 PAM, ogerin, was demonstrated to have on-target activity in vivo by modulating conditioned fear responses in mice. A similar approach has recently been used to identify small molecule ligands for the oGPCRs GPR171 (Wardman et al, 2016) and MRGPRX2 (Lansu et al, 2017), and these compounds were subsequently used to further characterize the receptor’s role in feeding behavior and itch, respectively.…”

Relationship between MRGPRX2 and pethidine hydrochloride- or fentanyl citrate-induced LAD2 cell degranulation

“…Mast cells play a critical role in the host defence, and they are tissue‐resident multifunctional immune cells best known for their roles in allergic and inflammatory diseases . MRGPRX2 is a novel GPCR for the neuropeptide SP, antimicrobial host defence peptides (HDPs), FDA‐approved cationic drugs, and opioids, and is expressed at high levels in the human skin (MC TC ) . LAD2 cells are skin‐derived mast cells that express high levels of MRGPRX2 .…”