Glycosaminoglycan binding and oligomerization are essential for the in vivo activity of certain chemokines

Abstract

During organogenesis, immunosurveillance, and inflammation, chemokines selectively recruit leukocytes by activating seven-transmembrane-spanning receptors. It has been suggested that an important component of this process is the formation of a haptotactic gradient by immobilization of chemokines on cell surface glycosaminoglycans (GAGs). However, this hypothesis has not been experimentally demonstrated in vivo . In the present study we investigated the effect of mutations in the GAG binding sites of three chemokines, monocyte chemoattractant protein-1/CC chemokine ligand (CCL)2, macrophage-inflammatory protein-1β/CCL4, and RANTES/CCL5, on their ability to recruit cells in vivo . These mutant chemokines retain chemotactic activity in vitro , but they are unable to recruit cells when administered intraperitoneally. Additionally, monomeric variants, although fully active in vitro , are devoid of activity in vivo . These data demonstrate that both GAG binding and the ability to form higher-order oligomers are essential for the activity of particular chemokines in vivo , although they are not required for receptor activation in vitro . Thus, quaternary structure of chemokines and their interaction with GAGs may significantly contribute to the localization of leukocytes beyond migration patterns defined by chemokine receptor interactions.