Cranin: a laminin-binding protein of cell membranes

We report that a 120-kDa glycoprotein is the predominant laminin-binding protein detected within plasma membranes of rodent NG108-15 neural hybrid cells, embryonic chicken brain, and mouse 3T3 fibroblasts. This protein was detected when membrane extracts were separated by PAGE, transferred to nitrocellulose, and incubated with laminin at concentrations as low as 2.8 X 10(-11) M, under conditions of physiological ionic strength and pH and in the presence of calcium ions. It behaves as an integral membrane component, and its laminin-binding moiety is accessible to the external face of the cell surface. Moreover, it appears to bind to a site on laminin that is very sensitive to proteolysis. The properties of this protein, which we have termed "cranin," distinguish it from other known laminin receptors and make it a candidate to mediate some of the effects of laminin upon cells.