Mouse Macrophage Derived Monocyte Chemotactic Protein-3: cDNA Cloning and Identification as MARC/FIC

When the mouse macrophage cell line WEHI-3 is triggered with LPS it produces proteases and secondary cytokines including interleukin-6 and chemokines. In an attempt to isolate the mouse homologue of the human monocyte chemotactic protein-3 (MCP-3), a cDNA library from LPS-stimulated WEHI-3 cells was screened with the full-size human MCP-3 cDNA. The longest cDNA out of several positive clones was sequenced and encoded a protein of 97 residues. Except for a third codon letter mismatch it was identical to the mouse MARC cDNA and encoded the MARC protein. The murine Fic cDNA, which encodes a Marc-mutant protein with an arginine substition for alanine, was not identified in the other sequenced homologous isolates. Similar to the human system, in which MCP-3 is most related to MCP-1, MURINE MCP-3 was found to be more homologous to mouse MCP-1/JE than to other murine C-C chemokines. We therefore postulate that MARC/FIC is the mouse MCP-3.