A MODEL OF GAG:MIP-2:CXCR2 INTERFACES AND ITS FUNCTIONAL EFFECTS

摘要

MIP-2/CXCL2 is a murine chemokine related to human chemokines that possess the Glu-Leu-Arg (ELR) activation motif and activates CXCR2 for neutrophil chemotaxis. We determined the structure of MIP-2 to 1.9Å resolution and created a model with its receptor murine CXCR2 based on the coordinates of human CXCR4. Chemokine-induced migration of cells through specific G protein-coupled receptors is regulated by glycosaminoglycans (GAGs) that oligomerize chemokines. MIP-2 GAG-binding residues were identified that interact with heparin disaccharide I-S by NMR spectroscopy. A model a GAG:MIP-2:CXCR2 complex that supports a 2:2 complex between chemokine and receptor was created. Mutants of these disaccharide-binding residues were made and tested for heparin binding, in vitro neutrophil chemotaxis, and in vivo neutrophil recruitment to the mouse peritoneum and lung. The mutants have a 10-fold decrease in neutrophil chemotaxis in vitro. There is no difference in neutrophil recruitment between wild-type MIP-2 and mutants in the peritoneum but all activity of the mutants is lost in the lung supporting the concept that GAG regulation of chemokines is tissue-dependent.