CX3CL1 gene is located on the long arm of chromosome 16 at position 13 and contains three exons. This gene encodes for a protein of 397 aa. The first 24 aa represents the peptide signal.

Only one type of transcript has been described. The 1194-nucleotide transcript encodes a protein of 397 amino acid residues. The primary structure of human CX3CL1 consists of an N-terminal 24-amino acid signal sequence followed by the chemokine domain of CX3CL1, a mucin-like stalk, a transmembrane domain and an intracellular part.

None described so far.

CX3CL1 is synthesized as a membrane protein consisting of the chemokine domain, a highly glycosylated mucin-like stalk, a transmembrane domain and an intracellular part. Cleavage by some metalloproteinases like ADAM-10 (Hundhausen et al., 2003), ADAM-17 (Garton et al., 2001; Tsou et al., 2001), MMP-2 (Bourd-Boittin et al., 2009) and cathepsin-S (Clark et al., 2009) gives raise to the soluble form of CX3CL1 consisting of the chemokine domain and the glycosylated mucin-like stalk (Bazan et al., 1997; Schulte et al., 2007). The C-terminal part contains two putative adaptor protein-2 (AP-2)-binding motifs, that control the constitutive endocytosis of the whole protein (Huang et al., 2009) mediated by clathrin and dynamin-1 (Robinson et al., 2002).

The chemokine CX3CL1 is constituvely expressed in microglial cells (Cross and Woodroofe, 1999), astrocytes (Hatori et al., 2002) and some neurons (Harrison et al., 1998; Cross and Woodroofe, 1999; Maciejewski-Lenoir et al., 1999; Deiva et al., 2004). Its expression is stimulated by inflammatory ligands in vascular endothelial cells (Fong et al., 1998; Imaizumi et al., 2000; Fraticelli et al., 2001; Schäfer et al., 2007), renal endothelial (Cross and Woodroofe, 1999) and epithelial cells (Chakravorty et al., 2002), in aortic (Ludwig et al., 2002; Ollivier et al., 2003) and pulmonary (Sukkar et al., 2004) smooth muscle cells and in dendritic cells (Papadopoulos et al., 1999; Dichmann et al., 2001; Pallandre et al., 2008).

The chemokine CX3CL1 is mainly localized at the plasma membrane (Bazan et al., 1997; Fong et al., 2000). Its biosynthesis in the Golgi and/or ER organelles starts as an non glycosylated and intracellular.

The function of CX3CL1 relies on both of its forms: the soluble form, released by metalloproteinases, is chemoattractant while the membrane form mediates stable adhesion of leukocytes such as integrins (Fong et al., 1998; Haskell et al., 1999).