Cryo-EM defines NK2R selectivity, revealing specific residues for improved agonist design

Current incretin-based pharmacotherapies for obesity primarily reduce food intake, leaving a significant gap for interventions that also boost energy expenditure. Activating the neurokinin 2 receptor (NK2R) has shown promise in preclinical models by both lowering food intake and stimulating energy expenditure. However, the endogenous NK2R ligand, Neurokinin A (NKA), suffers from cross-reactivity with other neurokinin receptors, leading to undesirable adverse effects. Understanding the structural basis for NK2R selectivity is therefore critical to unlock its therapeutic potential and develop safer, more effective agonists.

Researchers generated cryo-electron microscopy complexes of the NK2R bound to its endogenous ligand, NKA, and several synthetic peptide agonists. The goal was to identify candidate molecular interactions responsible for driving receptor selectivity. Following structural elucidation, targeted receptor and ligand mutagenesis was employed to functionally validate the specific amino acid residues within the NK2R binding pocket. Additionally, the C-terminus of the synthetic peptide agonists was investigated to confirm its role in selective binding and activation.

Cryo-electron microscopy complexes successfully elucidated the structural interactions of NK2R with NKA and various synthetic agonists. These structures revealed distinct candidate interactions within the receptor's binding pocket that are critical for selective ligand recognition. Functional mutagenesis studies confirmed the precise roles of specific residues within the NK2R binding site. These residues were found to dictate the preferential binding of synthetic agonists over NKA's non-selective interactions. Furthermore, the C-terminus of the synthetic peptide agonists was identified as a key determinant for achieving high selectivity. > The study provides a detailed structural framework, mapping specific amino acid residues in the NK2R binding pocket and the C-terminal region of synthetic agonists that are directly responsible for driving selective activation.