The amino-terminal extracellular domain of the MCP-1 receptor, but not the RANTES/MIP-1alpha receptor, confers chemokine selectivity. Evidence for a two-step mechanism for MCP-1 receptor activation

J Biol Chem. 1996 Aug 9;271(32):19084-92. doi: 10.1074/jbc.271.32.19084.


The chemoattractant cytokines, MCP-1 (monocyte chemoattractant protein) and MIP-1alpha (macrophage inflammatory protein), are recognized by highly homologous but distinct receptors. To identify receptor domains involved in determining ligand specificity, we created a series of chimeric MCP-1 and RANTES (regulated on activation, normal T cell expressed and secreted)/MIP-1alpha receptors that progressively interchanged the amino terminus and each of the three extracellular loops. Radiolabeled MCP-1 bound with high affinity to the wild-type MCP-1 receptor, but not to the RANTES/MIP-1alpha receptor (C-C CKR-1). Chimeras that retained the amino-terminal extension of the MCP-1 receptor bound MCP-1 with high affinity. In contrast, chimeric MCP-1 receptors, in which the wild-type amino terminus was replaced with the corresponding portion of the RANTES/MIP-1alpha receptor, bound MCP-1 with low affinity. These data indicate that the amino terminus of the MCP-1 receptor is necessary for high affinity binding of the ligand. Very different results were obtained using the RANTES/MIP-1alpha receptor. Radiolabeled MIP-1alpha bound with high affinity to chimeras that expressed the extracellular loops of the RANTES/MIP-1alpha receptor. In contrast to the MCP-1 receptor, substitution of the wild-type amino-terminal extension had little or no effect on MIP-1alpha binding. For the MCP-1, but not the RANTES/MIP-1alpha receptor, the presence of the wild-type amino terminus also significantly lowered the ligand concentration required for maximal signaling. We conclude that the amino-terminal extension of the MCP-1 receptor, but not the RANTES/MIP-1alpha receptor, is critically involved in ligand binding and signal transduction. These data reveal significant functional differences between the two C-C chemokine receptors and suggest a two-step mechanism for activation of the MCP-1 receptor.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Line
  • Chemokine CCL2 / metabolism*
  • Chemokines / metabolism*
  • Humans
  • Protein Binding
  • Receptors, CCR2
  • Receptors, CCR5
  • Receptors, Chemokine*
  • Receptors, Cytokine / genetics
  • Receptors, Cytokine / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction


  • CCR2 protein, human
  • Chemokine CCL2
  • Chemokines
  • Receptors, CCR2
  • Receptors, CCR5
  • Receptors, Chemokine
  • Receptors, Cytokine
  • Recombinant Fusion Proteins
  • macrophage inflammatory protein 1alpha receptor