Peptide fragments of the fractalkine chemokine domain: Influence on migration of human monocytes

The CX3CL1 Fractalkine is the sole cytokine of the CX3C family. Its molecule consists of an extracellular N-terminal chemokine domain, a mucin-like rod, a transmembrane domain, and an intracellular domain. Fractalkine exhibits the properties of an adhesion molecule in the membrane-bound state. The fractalkine chemokine domain (FCD) is proteolytically released from a cellular membrane in a soluble form. It acts as a chemoattractant for leukocytes which express the CX3CR1 fractalkine receptor. Fractalkine participates in the development of a number of pathological inflammation-mediated processes. Therefore, a search for its inhibitors is an urgent problem. We determined the FCD antigenic determinants and synthesized the corresponding peptides: P41-52 H-Leu-Glu-Thr-Arg-Gln-His-Arg-Leu-Phe-Cys-Ala-Asp-NH₂, P53-60 H-Pro-Lys-Glu-Gln-Trp-Val-Lys-Asp-NH₂, and P60-71 H-Asp-Ala-Met-Gln-His-Leu-Asp-Arg-Gln-Ala-Ala-Ala-NH₂. The biological activity of these peptides was evaluated according to their action on the adhesion and migration of human peripheral blood monocytes which expressed the fractalkine receptor. FCD and the P41-52 peptide significantly increased monocyte adhesion and migration in comparison with the corresponding spontaneous adhesion and migration of the cells. The P53-60 and P60-71 peptides inhibited the FCD-stimulated monocyte adhesion and migration. We analyzed the influence of the prepared peptides on the interaction of FCD with heparin by EIA, because binding of chemokines to glycosaminoglycans of cellular surface and extracellular matrix was one of the conditions of the chemokine migration activity. The P41?C52 peptide competed with FCD for the heparin binding, whereas the P53?C60 and P60?C71 peptides had no significant effect.