Abstract
In inflammation, neutrophils and other leukocytes roll along the microvascular endothelium before arresting and transmigrating into inflamed tissues. Arrest requires conformational activation of the integrin lymphocyte function-associated antigen-1 (LFA-1). Mutations of the FERMT3 gene encoding kindlin-3 underlie the human immune deficiency known as leukocyte adhesion deficiency-III. Both kindlin-3 and talin-1, another FERM domain-containing cytoskeletal protein, are required for integrin activation, but their individual roles in the induction of specific integrin conformers are unclear. Here, we induce differential LFA-1 activation in neutrophils through engagement of the selectin ligand P-selectin glycoprotein ligand-1 or the chemokine receptor CXCR2. We find that talin-1 is required for inducing LFA-1 extension, which corresponds to intermediate affinity and induces neutrophil slow rolling, whereas both talin-1 and kindlin-3 are required for induction of the high-affinity conformation of LFA-1 with an open headpiece, which results in neutrophil arrest. In vivo, both slow rolling and arrest are defective in talin-1-deficient neutrophils, whereas only arrest is defective in kindlin-3-deficient neutrophils. We conclude that talin-1 and kindlin-3 serve distinct functions in LFA-1 activation.