Type IV collagen-binding proteins of neutrophils: possible involvement of L-selectin in the neutrophil binding to type IV collagen

To isolate type IV collagen-binding proteins, 125I-labeled human- neutrophil extracts were chromatographed on a type IV collagen- Sepharose column. The affinity chromatography-separated fraction contained the four radioactive proteins with apparent molecular masses of 28, 49, 67, and 95 kD on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Western blot analysis indicated that the 95-kD proteins contained both L-selectin and nonspecific cross-reacting antigen 90 (NCA90), and that the 67-kD protein was the 67-kD elastin/laminin-binding protein (67BP). The data obtained with the type IV collagen-affinity chromatography and the immunoaffinity chromatographies using anti-L-selectin and anti-NCA90 monoclonal antibodies (MoAbs) have shown that L-selectin is closely associated with 67BP and the 49-kD protein, and that NCA90 is associated with 67BP, the 28-kD and 49-kD proteins. Among these binding proteins, sialic acid residues were contained in 67BP, L-selectin, and NCA90, but not in the 28-kD and 49-kD proteins. Sialidase treatment completely abolished both the binding affinity of the type IV collagen-binding proteins to type IV collagen and the neutrophil adherence to type IV collagen-coated plastic. Thus, the sialic acid residues of 67BP, L- selectin, and NCA90 seem to be important for the binding of neutrophils to type IV collagen. Furthermore, L-selectin IgG chimeric protein directly bound to type IV collagen-Sepharose column, and anti-L- selectin MoAb DREG56 inhibited the neutrophil adherence to type IV collagen-coated plastic by 51%. These observations suggest that L- selectin likely plays a role in the neutrophil binding to type IV collagen, although neutrophils have several kinds of adhesion molecules for type IV collagen such as L-selectin, NCA90, 67BP, and the 28-kD and 49-kD proteins.