Abstract
Endocrine fibroblast growth factors (FGFs) require Klotho transmembrane proteins as necessary co-receptors to activate FGF receptor (FGFR) signaling. In particular, FGF19 and FGF21 function through β-Klotho to regulate glucose and lipid metabolism. Recent research has focused on elucidating how these two FGFs interact with β-Klotho and FGFRs to activate downstream signaling. In this study, using hydrogen deuterium exchange coupled to mass spectrometry (HDX-MS), we identified regions on the β-Klotho protein that likely participate in ligand interaction, and vice versa. Alanine and arginine mutagenesis were carried out to further probe the contributions of individual residues to receptor/ligand interactions. Using biochemical and cell-based signaling assays with full-length proteins, we show that both the KL1 and KL2 domains of β-Klotho participate in ligand interaction, and these binding sites on β-Klotho are shared by FGF19 and FGF21. In addition, we show that two highly conserved regions in the C-terminal tail of FGF19 and FGF21 are responsible for interaction with the co-receptor. Our results are consistent with recent publications on the crystal structures of the Klotho proteins and provide insight into how endocrine FGFs interact with co-receptors for signal transduction.
Highlights
Fibroblast growth factors (FGFs) are a group of structurally-related, secreted signaling molecules that regulate diverse cellular functions including cell survival, growth, differentiation and migration[1]
Amides buried in the interface with binding partners will be protected against hydrogen-deuterium exchange, and sequence-specific measurements using mass spectrometry (MS) reveal the location of these protected regions, making hydrogen deuterium exchange coupled to mass spectrometry (HDX-MS) a sensitive method for probing protein-protein interactions[44,45]
Two recent reports were published; one describing the crystal structure of the β-Klotho extracellular domain (ECD) bound to the C-terminal peptide of FGF21, and another describing the trimeric complex structure of α-Klotho ECD, FGFR1c ligand binding domain, and FGF2314,15
Summary
Fibroblast growth factors (FGFs) are a group of structurally-related, secreted signaling molecules that regulate diverse cellular functions including cell survival, growth, differentiation and migration[1]. Endocrine FGFs, on the other hand, have intrinsically poor affinity for their cognate FGFRs and require two transmembrane proteins, α-Klotho and β-Klotho, as necessary co-receptors for signaling[2,10]. Recent breakthroughs have revealed the crystal structure of the ligand-bound β-Klotho ECD, as well as a trimeric complex structure composed of α-Klotho ECD, the ligand-binding domain of FGFR1c, together with FGF2314,15. While these structures greatly enhanced our understanding of receptor interaction and signaling of the endocrine FGFs, the ligand-bound β-Klotho ECD structure only contained FGF21’s C-terminal domain, and FGF19 co-receptor interactions remain to be fully characterized. Through systematic dissection of binding elements between β-Klotho and its ligands at the amino acid level, we propose a model for the assembly of the ligand/receptor complexes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
