Abstract
Chemokines mediate diverse fundamental biological processes, including combating infection. Multiple chemokines are expressed at the site of infection; thus chemokine synergy by heterodimer formation may play a role in determining function. Chemokine function involves interactions with G-protein-coupled receptors and sulfated glycosaminoglycans (GAG). However, very little is known regarding heterodimer structural features and receptor and GAG interactions. Solution nuclear magnetic resonance (NMR) and molecular dynamics characterization of platelet-derived chemokine CXCL7 heterodimerization with chemokines CXCL1, CXCL4, and CXCL8 indicated that packing interactions promote CXCL7-CXCL1 and CXCL7-CXCL4 heterodimers, and electrostatic repulsive interactions disfavor the CXCL7-CXCL8 heterodimer. As characterizing the native heterodimer is challenging due to interference from monomers and homodimers, we engineered a “trapped” disulfide-linked CXCL7-CXCL1 heterodimer. NMR and modeling studies indicated that GAG heparin binding to the heterodimer is distinctly different from the CXCL7 monomer and that the GAG-bound heterodimer is unlikely to bind the receptor. Interestingly, the trapped heterodimer was highly active in a Ca2+ release assay. These data collectively suggest that GAG interactions play a prominent role in determining heterodimer function in vivo. Further, this study provides proof-of-concept that the disulfide trapping strategy can serve as a valuable tool for characterizing the structural and functional features of a chemokine heterodimer.
Highlights
Chemokines, a large family of signaling proteins, mediate diverse biological processes, including innate and adaptive immunity, organogenesis, and tissue repair [1,2,3]
We investigated the molecular basis of heterodimer formation for the chemokine CXCL7 with chemokines CXCL1, CXCL4, and CXCL8
We show that favorable packing and ionic interactions promote CXCL7-CXCL1 and CXCL7-CXCL4 heterodimers and that repulsive ionic interactions disfavor the CXCL7-CXCL8 heterodimer
Summary
Chemokines, a large family of signaling proteins, mediate diverse biological processes, including innate and adaptive immunity, organogenesis, and tissue repair [1,2,3]. Lymphotactin, the only member of the C family, shows a typical chemokine fold and yet a completely different fold as a function of pH and solution conditions [21] These properties speak to the inherent plasticity of the chemokine dimer interface. Our observation that GAG binding interactions of a heterodimer could be quite different from the monomer suggests that these differences could play important roles in fine-tuning in vivo neutrophil recruitment and function. To our knowledge, this is the very first report of receptor and GAG interactions that could be unambiguously attributed to a chemokine heterodimer
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
