Cell Research | Researchers Reveal Structural Basis of Itching Neuropeptides Action on Bombesin Receptors
Update time：2022-11-03
Itch, as one of the most primal sensations, is an essentially protective mechanism to remind animals of impairment and expel noxious environmental substances, but often exists in patients with allergic skin diseases and/or systemic and neuropathic problems. On occasions, persistent itch (or chronic pruritus) significantly affects sleep, mood and individual health, and reduces life quality of patients. Unfortunately, the biological mechanism under itch is still indistinct and antipruritic drug research has been hindered.
On 3rd November, 2022, the research group of YIN Wanchao from the Zhongshan Institute for Drug Discovery, together with Prof. H. Eric Xu and his colleagues from the Shanghai Institute of Materia Medica (SIMM) of the Chinese Academy of Sciences (CAS), published the latest study entitled "Molecular recognition of itch-associated neuropeptides by bombesin receptors" online in Cell Research (IF=46.297). For the first time, this work reports the near-atomic-resolution structures of Gq-coupled neuromedin B receptor (NMBR) and gastrin-releasing peptide receptor (GRPR) binding to endogenous polypeptide ligands, neuromedin B (NMB) and gastrin-releasing peptide (GRP), respectively, and reveals the unique ligand-binding characteristics, receptor-selective recognition, as well as molecular mechanisms mediating itch signaling.
Bombesin (Bn) is an amphibian tetradecapeptide found in the skin of European Bombina. Both NMB and GRP, the two mammalian Bn-like peptides, are involved in a variety of physiological and pathological processes, including itch induced by histaminergic or nonhistaminergic pruritogens. As itch-specific neuropeptide receptors in the spinal cord, both NMBR and GRPR are at the core of itch transmission and play a pivotal role in itch biology; accordingly, they are attractive targets for antipruritic intervention (fig. 1a).
To explore the mechanism of peptide recognition by itch receptors, Researchers assembled agonist-bombesin receptor-Gq complexes for cryo-electron microscopy (cryo-EM) studies using approaches of BRIL fusion, NanoBiT tethering, Gq engineering, and antibody scFv16, which had previously been used successfully in solving several GPCR/G-protein complexes. The cryo-EM structures of NMBR and GRPR, both complexed with the engineered Gq and selective peptide agonists NMB30 and GRP (14-27), were solved at global resolutions of 3.15 ? and 3.30 ?, respectively (fig. 1b-g).
In the two structures, both NMB and GRP present a dumbbell-shaped overall conformation and adopts a binding pose perpendicular to the membrane plane, with its C terminus inserted deep into the transmembrane domain (TMD) bundle, while its N terminus pointing to the extracellular surface (fig. 1d, g). Researchers performed functional assays and then revealed that the C-terminal amide of the amidated NMB and GRP forms an additional hydrogen bond, which partially explains the phenomenon that the amidated bombesin peptides presented nearly 100-fold higher potencies than the nonamidated forms for their corresponding receptors.
In summary, this study provides a detailed description of the recognition characteristics and structural basis between the endogenous ligands and bombesin receptors. With the in-depth knowledge of ligand binding and selectivity of bombesin receptors, new opportunities may arise to design potent and efficacious modulators of bombesin receptors for the treatment of itch and other diseases.
Fig. 1 Cryo-EM structures of the NMB30-NMBR-Gq and GRP (14-27)-GRPR-Gq complexes and analyses of the binding and selectivity for two itching neuropeptides.
a A schematic illustration of the chemical itch pathways, showing the pivotal roles of the two itching neuropeptides (NMB and GRP) and receptors (NMBR and GRPR) in itch transmission.
b-g Cryo-EM structures of the NMB30-NMBR-Gq complex and GRP (14-27)-GRPR-Gq complex.
h-k Binding mode comparison of the NMB30-binding pocket in NMBR and the GRP (14-27)-binding pocket in GRPR.
l-n Detailed interactions between L3N and F9N with residues in NMBR and H3G and L9G with residues in GRPR.
o Structural superposition of two active bombesin receptors, active CCKAR and inactive CCKAR from the side views.
DOI: https://doi.org/10.1038/s41422-022-00743-6
Link to article: https://www.nature.com/articles/s41422-022-00743-6
Contributing Department: Research Group of YIN Wanchao