The capacity of macrophages to interact with basement membrane (BM) glycoproteins (laminin and Type IV collagen) is essential for their normal emigration from blood to tissue, and for their involvement in many pathological situations. Laminin may also stimulate phagocytosis and it has been implicated in the cytotoxic recognition of tumor cells. The ability of macrophages to interact with BM glycoproteins requires prior activation with either PMA or interferon-gamma and lipopolysaccharide. This proposal focuses on the structural and functional characterization of three distinct laminin binding proteins (LBPs) present on the macrophage surface: a 67kD laminin receptor, a novel 36kD (LBP), and an 80kD LBP related to the muscle LBP aspartactin. These studies will involve both mouse macrophages and human monocytes. Structural data on the 67kD and 36kD LBPs will be obtained by sequencing peptides derived from LBPs purified by laminin-Sepharose chromatography. cDNA clones for the 67kD and 36kD LBPs will be obtained by screening both macrophage and monocyte libraries with specific antibodies and oligonucleotide probes. The peptide and cDNA sequence data should elucidate the primary structure of these LBPs, as well as their homology with each other and other matrix receptors. The biosynthesis and post-translational modifications of the LBPs will be examined using a variety of biochemical methods. Data obtained should contribute to an understanding of their inter-relationships and possible functions. The 67kD LBP, and possibly other LBPs, are peripheral membrane proteins. Chemical cross-linking methods will be used to determine if they associate with each other or with integral membrane proteins. The possibility that macrophage activation induces laminin interactions by promoting such associations will be examined. Other molecules (integrins and sulfated glycolipids) that may contribute to the laminin binding capacity of macrophages and monocytes will be identified and characterized. Finally, the data and reagents obtained from the above studies will be used to study the involvement of LBPs in two biological systems: macrophage/monocyte interactions with reconstituted basement membranes and macrophage interactions with tumor cells.
