Inhibition of Neutrophil Chemokinesis on Vitronectin by Inhibitors of Calcineurin

Migration of human polymorphonuclear neutrophils on vitronectin is dependent on repeated transient increases in the concentration of intracellular free calcium (Ca2+i). A specific peptide inhibitor of the Ca(2+)-calmodulin-dependent phosphatase calcineurin was introduced into the cytoplasm of neutrophils. The peptide inhibited neutrophil migration on vitronectin by interfering with the release of the cells from sites of attachment. A similar reduction in motility on vitronectin occurred when cells were treated with the immunosuppressant FK506, which also inhibits calcineurin when bound to its binding protein, FKBP. These results indicate that a rise in Ca2+i reduces integrin-mediated adhesion to vitronectin by a mechanism that requires calcineurin activity.