Human CXCL17 binds and activates fish GPR25 orthologs.

Area of Science:

• Biochemistry
• Molecular Biology
• Evolutionary Biology

Background:

• C-X-C motif chemokine ligand 17 (CXCL17) is a chemoattractant with a controversial receptor.
• Recent studies identified G protein-coupled receptor 25 (GPR25) as a CXCL17 receptor.
• While GPR25 is conserved across vertebrates, CXCL17 orthologs are thought to be mammalian-specific.

Purpose of the Study:

• To investigate the interaction between human CXCL17 and non-mammalian GPR25 orthologs.
• To determine if the CXCL17-GPR25 signaling pathway is conserved across vertebrates.

Main Methods:

• Utilized NanoLuc Binary Technology (NanoBiT) for β-arrestin recruitment and binding assays.
• Employed HEK293T cells transfected with fish GPR25 orthologs (zebrafish and coelacanth).
• Tested human CXCL17 activity and binding to fish GPR25 orthologs, including a C-terminal mutant.

Main Results:

• Human CXCL17 demonstrated high activity towards zebrafish and coelacanth GPR25 orthologs.
• Human CXCL17 induced chemotaxis in HEK293T cells expressing fish GPR25.
• A C-terminal fragment of human CXCL17 was essential for GPR25 binding and activation.
• Fish GPR25 orthologs showed higher cell surface expression than human GPR25.

Conclusions:

• The CXCL17-GPR25 interaction is conserved across vertebrates, despite the apparent absence of non-mammalian CXCL17 orthologs.
• Human CXCL17 can activate GPR25 orthologs from distantly diverged species like zebrafish and coelacanth.
• This suggests a conserved vertebrate signaling pathway for CXCL17 and GPR25.