Biology subjects

Yao, J.-J.

Publications and source records attributed to Yao, J.-J..

3 recordsLinked to original sources

bioRxiv2026

Origin of the GPR15LG-GPR15 signaling axis in ancient fish ancestors

The chemokine-like peptide GPR15LG is a known agonist of G protein-coupled receptor 15 (GPR15), a ligand-receptor pair primarily implicated in mammalian mucosal immunity and lymphocyte homing. However, the evolutionary origin and phylogenetic distribution of this signaling system remain poorly understood due to the extreme sequence diversity of GPR15LG orthologs. In this study, we identified GPR15LG orthologs in several fish species for the first time according to their conserved gene synteny, genomic organization, and amino acid sequence features. A representative ortholog from the spotted gar (Lepisosteus oculatus), termed Lo-GPR15LG, was recombinantly prepared and functionally characterized using NanoLuc Binary Technology (NanoBiT)-based {beta}-arrestin recruitment assay and homogenous ligand-receptor binding assay. Our results demonstrated that Lo-GPR15LG directly binds to and efficiently activates its cognate receptor, Lo-GPR15, with a dissociation constant (Kd) of approximately 60 nM and an EC50 value of approximately 10 nM. Functional assays further revealed that receptor activation is critically dependent on the conserved C-terminal residues. Notably, human and fish orthologs exhibited no cross-species activity, consistent with their high sequence divergence. These findings reveal that the GPR15LG-GPR15 signaling system originated in ancient fish ancestors and has remained a conserved signaling axis throughout vertebrate evolution, suggesting a fundamental role in immunity across all vertebrate lineages.

biochemistry↗

bioRxiv2026

Identification and Functional Characterization of CXCL17 Orthologs in Amphibians

C-X-C motif chemokine ligand 17 (CXCL17) has recently been identified as an agonist of the poorly characterized G protein-coupled receptor 25 (GPR25). Although GPR25 orthologs are widely distributed across vertebrates, non-mammalian CXCL17 orthologs have only been identified in some fish species in our recent studies. In this study, we systematically searched public databases for amphibian CXCL17 orthologs based on conserved C-terminal motif, gene synteny, and genomic architecture. Using this approach, we identified up to eighteen CXCL17 orthologs from diverse amphibian species. These amphibian CXCL17s exhibit no significant overall sequence similarity to known mammalian or fish CXCL17s, thus they were previously classified as uncharacterized proteins or even unannotated. Compared with known mammalian or fish CXCL17s, most amphibian CXCL17s display distinctive features, including four cysteine residues in their mature peptide and an additional residue following the conserved C-terminal Xaa-Pro-Yaa motif. A representative ortholog from the tropical clawed frog (Xenopus tropicalis) was recombinantly expressed and functionally characterized using cell-based assays, inducing ligand-receptor binding, {beta}-arrestin recruitment, and chemotactic cell migration. The recombinant amphibian CXCL17 directly bound to and efficiently activated its cognate GPR25 receptor and induced chemotactic migration of the transfected human embryonic kidney (HEK) 293T cells, but deletion of four C-terminal residues largely abolished its activity, indicating that all CXCL17 orthologs employ a conserved mechanism for receptor binding and activation. These findings establish the presence of a functional CXCL17-GPR25 signaling system in amphibians and provide new insights into the phylogenetic distribution and sequence diversity of CXCL17 orthologs across vertebrate lineages.

biochemistry↗

bioRxiv2025

Human CXCL17 Activates and Binds to Fish GPR25 Orthologs

C-X-C motif chemokine ligand 17 (CXCL17) functions as a chemoattractant, though its receptor has been controversial. Recent independent studies, including our own, identified CXCL17 as an agonist for the orphan G protein-coupled receptor 25 (GPR25). While GPR25 orthologs are found across fishes to mammals, CXCL17 orthologs appear to be mammalian-specific, leaving the endogenous ligand for non-mammalian GPR25 orthologs unknown. This study unexpectedly found that human CXCL17 exhibits high activity towards GPR25 orthologs from the zebrafish (Danio rerio) and coelacanth (Latimeria chalumnae). Recombinant human CXCL17 efficiently activated both fish GPR25 orthologs in a NanoLuc Binary Technology (NanoBiT)-based {beta}-arrestin recruitment assay, and induced chemotactic movement in transfected human embryonic kidney (HEK) 293T cells expressing fish GPR25. A human CXCL17 mutant lacking three C-terminal residues showed no such effect. A NanoBiT-based binding assay revealed that a SmBiT-tagged human CXCL17 C-terminal fragment specifically bound to secretory large NanoLuc fragment (sLgBiT)-fused fish GPR25 orthologs. Fish GPR25 orthologs had significantly higher cell surface expression in transfected HEK293T cells compared to human GPR25, improving {beta}-arrestin recruitment assay data quality. Despite approximately 400 million years of divergence between humans and fishes, the high activity of human CXCL17 on fish GPR25 orthologs suggests that the CXCL17-GPR25 pair may be conserved across all vertebrates, even though non-mammalian CXCL17 orthologs remain unidentified.

biochemistry↗