Heparin oligosaccharides inhibit chemokine (CXC motif) ligand 12 (CXCL12) cardioprotection by binding orthogonal to the dimerization interface, promoting oligomerization, and competing with the chemokine (CXC motif) receptor 4 (CXCR4) N terminus. J Biol Chem 2013 Jan 04;288(1):737-46
Date
11/14/2012Pubmed ID
23148226Pubmed Central ID
PMC3537072DOI
10.1074/jbc.M112.394064Scopus ID
2-s2.0-84872066189 (requires institutional sign-in at Scopus site) 76 CitationsAbstract
The ability to interact with cell surface glycosaminoglycans (GAGs) is essential to the cell migration properties of chemokines, but association with soluble GAGs induces the oligomerization of most chemokines including CXCL12. Monomeric CXCL12, but not dimeric CXCL12, is cardioprotective in a number of experimental models of cardiac ischemia. We found that co-administration of heparin, a common treatment for myocardial infarction, abrogated the protective effect of CXCL12 in an ex vivo rat heart model for myocardial infarction. The interaction between CXCL12 and heparin oligosaccharides has previously been analyzed through mutagenesis, in vitro binding assays, and molecular modeling. However, complications from heparin-induced CXCL12 oligomerization and studies using very short oligosaccharides have led to inconsistent conclusions as to the residues involved, the orientation of the binding site, and whether it overlaps with the CXCR4 N-terminal site. We used a constitutively dimeric variant to simplify the NMR analysis of CXCL12-binding heparin oligosaccharides of varying length. Biophysical and mutagenic analyses reveal a CXCL12/heparin interaction surface that lies perpendicular to the dimer interface, does not involve the chemokine N terminus, and partially overlaps with the CXCR4-binding site. We further demonstrate that heparin-mediated enzymatic protection results from the promotion of dimerization rather than direct heparin binding to the CXCL12 N terminus. These results clarify the structural basis for GAG recognition by CXCL12 and lend insight into the development of CXCL12-based therapeutics.
Author List
Ziarek JJ, Veldkamp CT, Zhang F, Murray NJ, Kartz GA, Liang X, Su J, Baker JE, Linhardt RJ, Volkman BFAuthors
John E. Baker PhD Professor in the Surgery department at Medical College of WisconsinBrian F. Volkman PhD Professor in the Biochemistry department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
AnimalsBinding Sites
Biophysics
Cardiotonic Agents
Chemokine CXCL12
Chemokines
Dimerization
Glycosaminoglycans
Heparin
Humans
Inhibitory Concentration 50
Kinetics
Magnetic Resonance Spectroscopy
Models, Molecular
Molecular Conformation
Myocardial Infarction
Oligosaccharides
Perfusion
Protein Structure, Tertiary
Rats
Receptors, CXCR4
