IDENTIFICATION AND MOLECULAR CHARACTERIZATION OF FRACTALKINE RECEPTORCX(3)CR1, WHICH MEDIATES BOTH LEUKOCYTE MIGRATION AND ADHESION

Leukocyte trafficking at the endothelium requires both cellular adhesi on molecules and chemotactic factors. Fractalkine, a novel transmembra ne molecule with a CX3C-motif chemokine domain atop a mucin stalk, ind uces both adhesion and migration of leukocytes. Here we identify a sev en-transmembrane high-affinity receptor for fractalkine and show that it mediates both the adhesive and migratory functions of fractalkine. The receptor, now termed CX(3)CR1, requires pertussis toxin-sensitive G protein signaling to induce migration but not to support adhesion, w hich also occurs without other adhesion molecules but requires the arc hitecture of a chemokine domain atop the mucin stalk. Natural killer c ells predominantly express CX(3)CR1 and respond to fractalkine in both migration and adhesion. Thus, fractalkine and CX(3)CR1 represent new types of leukocyte trafficking regulators, performing both adhesive an d chemotactic functions.