Recombinant Canine CCL2/MCP-1 Protein

Canine MCP-1 (monocyte chemotactic protein-1) is an 8 kDa member of the CC chemokine family of chemotactic factors (1, 2). It is synthesized as a 101 amino acid (aa) precursor that contains a 23 aa signal sequence and a 78 aa mature segment (3). It contains no potential N-linked glycosylation sites and is not known for any posttranslational modifications. Based on human studies, MCP-1 will primarily circulate as a monomer. Noncovalent dimers are likely to be found, however. MCP‑1 activity has been localized to the N-terminus (1). Cell types known to secrete MCP-1 are considerable in number, and include keratinocytes, fibroblasts, endothelium, osteoblasts, macrophages, mast cells, smooth muscle cells and astrocytes (1, 2). In the mature MCP-1 segment, there is 82% and 83% aa identity, canine to human and porcine MCP-1, respectively. When mature canine MCP-1 is compared to (125 aa) extended rodent MCP-1, there is 55% and 56% aa identity, canine to mouse and rat MCP-1, respectively. MCP-1 has three possible receptors. The first two are CCR2 (1) and CCR11 (4). The third receptor has only been identified in mice and is called L-CCR (5). Its function is unknown. MCP-1 is best known as a chemotactic agent for mononuclear cells. It also, however, induces enzyme and cytokine release in monocytes, NK cells, and lymphocytes and histamine release by basophils (1). Additionally, it is believed to reduce IL-12 production by dendritic cells and promote a Th2 phenotype in CD4⁺ T cells (6).