Integrin CD11c/CD18 α-Chain Phosphorylation Is Functionally Important

CD11c/CD18 ((X2), p150/95, or complement receptor 4, CR4) is a monocyte/macrophage-enriched integrin that has been reported to bind to a variety of ligands. These include cell surface proteins, extracellular matrix proteins, and soluble ligands. The regulation of ligand binding to CD11c/CD18 has remained poorly understood. Previous work has shown that both -chain and -chain phosphorylations of CD11a/CD18 and CD11b/CD18 are needed for activity, but no corresponding studies on CD11c/CD18 have been performed. In this study, we have identified the phosphorylation site of CD11c as Ser-1158 and show that it is pivotal for adherence and phagocytosis.