Solution structure of CXCL13 and heparan sulfate binding show that GAG binding site and cellular signalling rely on distinct domains

Open Biol. 2017 Oct;7(10):170133. doi: 10.1098/rsob.170133.


Chemokines promote directional cell migration through binding to G-protein-coupled receptors, and as such are involved in a large array of developmental, homeostatic and pathological processes. They also interact with heparan sulfate (HS), the functional consequences of which depend on the respective location of the receptor- and the HS-binding sites, a detail that remains elusive for most chemokines. Here, to set up a biochemical framework to investigate how HS can regulate CXCL13 activity, we solved the solution structure of CXCL13. We showed that it comprises an unusually long and disordered C-terminal domain, appended to a classical chemokine-like structure. Using three independent experimental approaches, we found that it displays a unique association mode to HS, involving two clusters located in the α-helix and the C-terminal domain. Computational approaches were used to analyse the HS sequences preferentially recognized by the protein and gain atomic-level understanding of the CXCL13 dimerization induced upon HS binding. Starting with four sets of 254 HS tetrasaccharides, we identified 25 sequences that bind to CXCL13 monomer, among which a single one bound to CXCL13 dimer with high consistency. Importantly, we found that CXCL13 can be functionally presented to its receptor in a HS-bound form, suggesting that it can promote adhesion-dependent cell migration. Consistently, we designed CXCL13 mutations that preclude interaction with HS without affecting CXCR5-dependent cell signalling, opening the possibility to unambiguously demonstrate the role of HS in the biological function of this chemokine.

Keywords: CXCL13; chemokine; glycosaminoglycan; heparan sulfate binding site; heparan sulfate sequence.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Binding Sites*
  • Chemokine CXCL13 / chemistry*
  • Chemokine CXCL13 / genetics
  • Chemokine CXCL13 / metabolism*
  • Heparitin Sulfate / chemistry*
  • Heparitin Sulfate / metabolism*
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Molecular Conformation*
  • Protein Binding
  • Protein Conformation, alpha-Helical
  • Protein Interaction Domains and Motifs*
  • Protein Multimerization
  • Protein Stability
  • Recombinant Proteins
  • Solutions
  • Structure-Activity Relationship


  • Chemokine CXCL13
  • Recombinant Proteins
  • Solutions
  • Heparitin Sulfate