C-X3-C motif chemokine ligand 1 (CX3CL1) (CX3CL1)

Fractalkine (CX3CL1) is a unique chemokine characterized by its CX3C motif and its dual role as both a cell-surface adhesion molecule and a soluble chemoattractant (UniProt P78423). It is primarily expressed by endothelial cells and neurons, signaling through its specific receptor, CX3CR1, which is expressed on various immune cells including monocytes, NK cells, and microglia (PubMed: 29038341). In its membrane-anchored form, CX3CL1 facilitates the firm adhesion of leukocytes to vascular walls, while its soluble form, released via proteolytic cleavage by ADAM10 or ADAM17, directs the migration of these cells toward sites of inflammation (PubMed: 11169396). This axis is critically involved in the pathogenesis of chronic inflammatory diseases such as rheumatoid arthritis, Crohn's disease, and atherosclerosis, where it promotes excessive leukocyte infiltration (PubMed: 28438773). Furthermore, in the central nervous system, CX3CL1-CX3CR1 signaling is vital for maintaining microglial homeostasis, and its dysregulation is linked to neurodegenerative conditions like Alzheimer's disease (PubMed: 30105151). Therapeutic development has focused on neutralizing this pathway, with agents like the monoclonal antibody quisovalimab (E6011) undergoing clinical evaluation for inflammatory bowel disease and rheumatoid arthritis (ClinicalTrials.gov: NCT03384940). By blocking the interaction between CX3CL1 and its receptor, these drugs aim to reduce the recruitment of inflammatory cells to diseased tissues. However, the dual role of CX3CL1 in both inflammation and neuroprotection presents a challenge for drug development, requiring careful consideration of systemic versus localized effects.

Other names

FractalkineNeurotactinABCD-3C3XkineSCYD1CX3C membrane-anchored chemokineSmall inducible cytokine subfamily D member 1

Neutralization of the CX3CL1 ligand to prevent binding and activation of the CX3CR1 receptor, thereby inhibiting leukocyte adhesion and chemotaxis (PubMed: 28438773).