Binding of ADAM28 to P-selectin glycoprotein ligand-1 enhances P-selectin-mediated leukocyte adhesion to endothelial cells

ADAMs (a disintegrin and metalloproteinases) are a recently discovered gene family of multifunctional proteins with the disintegrin-like and metalloproteinase domains. To analyze the biological functions of ADAM28, we screened binding molecules to secreted-type ADAM28 (ADAM28s) by the yeast two-hybrid system and identified P-selectin glycoprotein ligand-1 (PSGL-1). Binding between the disintegrin-like domain of ADAM28s and the extracellular portion of PSGL-1 was determined by yeast two-hybrid assays, binding assays of the domain-specific recombinant ADAM28s species using PSGL-1 stable transfectants and leukocyte cell lines expressing native PSGL-1 (HL-60 cells and Jurkat cells), and co-immunolocalization and co-immunoprecipitation of the molecules in these cells. Incubation of HL-60 cells with recombinant ADAM28s enhanced the binding to P-selectin-coated wells and P-selectin-expressing endothelial cells. In addition, intravenous injection of ADAM28s-treated HL-60 cells increased their accumulation in the pulmonary microcirculation and alveolar spaces in a mouse model of endotoxin-induced inflammation. These data suggest a novel function that ADAM28s promotes PSGL-1/P-selectin-mediated leukocyte rolling adhesion to endothelial cells and subsequent infiltration into tissue spaces through interaction with PSGL-1 on leukocytes under inflammatory conditions.