Fractalkine/CX3CL1, Human, Recombinant

Fractalkine, CX3CL1, is a novel multidomain chemokine expressed as a membrane-spanning adhesion molecule that can be cleaved from the cell surface to produce a soluble chemoattractant. Human fractalkine cDNA encodes a 397 amino acid residue membrane protein with a 24 amino acid residue predicted signal peptide, a 76 amino acid residue chemokine domain, a 241 amino acid residue stalk region containing 17 degenerate mucin-like repeats, a 19 amino acid residue transmembrane segment and a 37 amino acid residue cytoplasmic domain. The extracellular domain of human fractalkine can be released, possibly by proteolysis at the dibasic cleavage site proximal to the membrane, to generate soluble fractalkine. This release can be inhibited by the zinc metalloproteinase inhibitor batimastat. Fractalkine mRNA has been detected in various tissues including the brain and heart. Fractalkine is produced by endothelial cells, microglia and smooth muscle in response to inflammatory signals. Membrane-bound fractalkine has been shown to promote adhesion of leukocytes. The soluble chemokine domain of human fractalkine was reported to be chemotactic for T cells, monocytes and dendritic cells. It also induces cell survival, immunomodulation and actin polymerization. The gene for human fractalkine has been mapped to chromosome 16q. The 76 amino acid residue recombinant protein has a predicted molecular mass of approximately 8.5 kDa.