Abstract
Interactions of chemokines and chemokine receptors are extensively involved in blood coagulation, inflammatory and cancer metastasis. Most chemokines have distinct oligomerization states that are correlated with their biological functions. CXCL4 (PF4) is the first chemokine identified to be anti-angiogenic chemokine and its activity is mediated through its receptor CXCR3. To understand the detail mechanism of different CXCL4 oligomers in regulating CXCR3 function, we prepared CXCL4 monomer, dimer and tetramer and monitored the interaction with CXCR3 N-terminal sequence (residue 18-36). CXCL4 oligomer status was controlled by pH, NaCl concentration and mutation(s). By titrating the CXCR3 N-terminus-derived peptide into CXCL4 solutions, we characterized the critical role of post-translational modification of tyrosine sulfation for chemokine interaction. The sulfated CXCR3 N-terminus-derived peptide showed different extents in interacting CXCL4 monomer, dimer and tetramer. Furthermore, we focused on CXCL4L1, a CXCL4 variant that has three substitutions at P58L, K66E and L67H. CXCL4L1 possesses higher anti-angiogenetic activity than CXCL4. We revealed that CXCL4L1 contained a C-terminal helix with disordered property. Because of the role of C-terminal helix in stabilizing dimer interface, CXCL4L1 have greater ability to dissociate itself into monomer. We believe the different oligomer tendencies to change CXCL4 and CXCL4L1 anti-angiogensis activity.