Binding of the CC-chemokine RANTES to syndecan-1 and syndecan-4 expressed on HeLa cells

It is believed that proteoglycans influence biological properties of chemokines. We show that the CC chemokine RANTES binds not only to high-affinity binding sites on CCR5-positive HeLa cells but also to low-affinity binding sites on HeLa cells expressing or lacking RANTES G protein-coupled receptors. Coimmunoprecipitation studies demonstrate that RANTES forms complexes with glycanated syndecan (SD)-1 and -4, in addition to CCR5 on the CCR5-positive HeLa cells. Moreover, confocal microscopy analysis shows the colocalization of RANTES with SD-1 and -4. Glycosaminoglycans removal from the cells by glycosaminidases treatment prevented RANTES binding to SD-1 and -4 and decreased RANTES binding to CCR5 on the CCR5-positive HeLa cells. Removal of glycosaminoglycans by glycosaminidases treatment of the complexes, RANTES/SD-1/SD-4/+/-CCR5, immobilized on beads, reversed SD-1 and -4 bindings. Therefore, RANTES bindings to SD-1 and -4 depend on glycosaminoglycans and facilitate RANTES interaction with CCR5. Extracting plasma membrane cholesterol abolished the coimmunoprecipitation of SD-1 with RANTES, suggesting that rafts are involved in RANTES association to SD-1. Confocal microscopy analysis as well as coimmunoprecipitation experiments show a RANTES-independent heteromeric complex on the CCR5-positive HeLa cells, SD-1, SD-4, and CCR5. This complex is likely a functional unit in which proteoglycans may modulate RANTES binding to CCR5.