Chemosensation of the pheromone spermine by the olfactory TAAR-like receptor TAAR348

This is the authors' abstract. We don't add key points for this paper.

Trace amine-associated receptors (TAARs) are a vertebrate-specific subfamily of G protein-coupled receptors (GPCRs) that are broadly expressed in the mammalian central nervous system and involved in olfaction, behavior, and emotional regulation 1 . Since their initial cloning in 2001, TAARs have been identified across diverse species, exhibiting notable evolutionary diversity 2 . The TAAR family can be divided into three major evolutionary clades: Clade I consists of conserved single-copy genes; Clade II shows species-specific expansions; and Clade III is primarily found in teleosts 3 . Additionally, a group of TAAR-like genes, although evolutionarily distinct from canonical TAARs, retains chemosensory functions 4 (Fig. 1a ; Supplementary Fig. S1a ). Recent structural elucidation of TAAR1 5 , 6 , TAAR9 7 , and TAAR7f 8 has significantly advanced our understanding of ligand recognition mechanisms in the TAAR family. This advancement is particularly important for guiding drug discovery efforts targeting this unique class of aminergic receptors, which are significantly involved in a range of behavioral and neurological disorders. However, structural studies on the more abundant olfactory TAAR-like receptors remain limited, and their ligand recognition mechanisms and structural features are still poorly understood. Fig. 1: Structural and functional characterization of spermine recognition by TAAR348. a The TAAR family is divided into distinct classes based on phylogenetic analysis. TAAR348 belongs to the TAAR-like branch in sea lampreys. b Phylogenetic tree depicting the relationships among a total of 10 species, including both jawed and jawless vertebrates. Red line indicates the nodes containing TAAR348 and its orthologs. Branch lengths indicate divergence time (million years ago, MYA). c Conceptual model of spermine sensing by TAAR348 in sea lampreys, highlighting the potential role of TAAR348 in modulating behaviors through spermine sensation. Figure created with http://BioRender.com . d The dose-response curve illustrates the BRET2 assay results for spermine activating TAAR348, conducted in HEK293 cells overexpressing TAAR348 and G s sensors. e Cryo-EM density map of the spermine–TAAR348–G s complex. The complex density map is shown at a contour level of 0.14. Blue, spermine-bound TAAR348; green, Gα s ; pink, Gβ; yellow, Gγ; gray, NB35; orange, ScFv16. f The non-polar interactions between spermine and residues from TAAR348. g Key polar interactions between spermine and residues from TAAR348. The hydrogen-bonding network to stabilize the interaction is depicted. Sequential designation of the four amine groups of spermine as N1 to N4. h BRET ratios measured for increasing concentrations of the agonist spermine for the wild-type TAAR348 (WT) and 11 mutants, and normalized with respect to cell surface expression levels. Experiments were performed independently three times (see Supplementary Table S3 for details), with a single measurement per experiment; error bars represent the SEM. Each mutant response was normalized to the corresponding TAAR348 (WT), which was set to 100%. i Structural comparison highlighting key hydrogen bonds and salt bridges between the amine groups of the ligand and receptor residues in TAAR348–spermine, mTAAR7f–DMCHA, mTAAR9–spermidine, and hTAAR1–β-PEA complexes. The conserved salt bridge formed by D 3.32 with the central amine is shown in all complexes. In the spermine–TAAR348 complex, the terminal amines N1 and N4 also form key interactions, further stabilizing spermine’s extended conformation. Interactions are depicted as dashed lines. j Barcode representation of interaction patterns in the ligand pockets of TAAR348–spermine, mTAAR7f–DMCHA, mTAAR9–spermidine, and hTAAR1–β-PEA complexes. The conserved residues forming the generic motif for amine recognition across the three complexes are indicated by orange circles. Residues exhibiting no interaction with the respective ligands are shown as gray circles. k Structural representation of the spermine–TAAR348 interactions highlighting the critical role of the E 6.58 -W 7.35 motif in ligand recognition. Full size image