The collagenous domain of class A scavenger receptors is involved in macrophage adhesion to collagens.

Class A macrophage scavenger receptors (MSRs) have a remarkably broad ligand specificity and are well-known for their roles in atherogenesis and host defense. Recently, we demonstrated that these receptors also recognize and mediate adhesion to denatured forms of type I collagen. In this study, the involvement of the collagenous domain of MSRs in binding to denatured type I collagen was investigated. Transient expression of full-length, native type II MSR in COS-1 cells conferred adhesion to denatured type I collagens, whereas expression of a truncated receptor lacking the distal portion of the collagenous domain did not. Further, a synthetic peptide derived from the collagenous domain was effective in abrogating Mphi adhesion to denatured forms of type I collagen. We also addressed collagen-type specificity by examining MSR affinity for type III and type IV collagens. As with type I collagen, Mphis adhered only to denatured forms of type III collagen. Moreover, the adhesion was mediated by MSRs. In contrast, adhesion to denatured type IV collagen was not shown to be MSR-dependent, but adhesion to the native form was. MSR-mediated adhesion to types III and IV collagens was also shown to be dependent on the collagenous domain. Taken together, these data strongly suggest that the collagenous domain is involved in MSR-mediated adhesion to denatured forms of types I and III collagens and native, but not denatured, type IV collagen.