The chemokine monocyte chtemoattractant protein-1 induces functional responses through dimerization of its receptor CCRZ

摘要

Cytokines interact with hematopoietin superfamily reccptors and stimulate receptor dimerization. We demonstrate that chemoattractant cytokines (chemokines) also trigger biological responses through receptor dimerization. Functional responses are induced after pairwise crosslinking of chemokine receptors by bivalent agonistic antichemokine receptor mAb, but not by their Fab fragments. Monocyte chemoattractant protein (MCP)-1- triggered receptor dimerization was studied in human embryonic kidney (HEK)-293 cells cotransfected with genes coding for the CCRZb receptor tagged with YSK or Myc sequences. After MCP-I stimulation, immunoprecipitation with Myc-specific an tibodies revealed YSK-tagged receptors in immunobl otting. Receptor dimerization also was validated by chemical crosslinking in both HEK-293 cells and the human monocytic cell line Mono Mac l. Finally, we constructed a loss-of function CCRZbY139F mutant that acted as a dominant negative, blocking signaling through the CCRZ wild-type receptor. This study provides functional support for a model in which the MCP-l receptor is activated by ligand- induced homodimerization, allowing discussion of the similarities between bacterial and leukocyte chemotaxis.