Identification of a heparin binding site and the biological activities of the laminin α1 chain carboxy-terminal globular domain

The carboxy-terminal globular domain (G-domain) of the laminin alpha 1 chain has been shown to promote heparin binding, cell adhesion, and neurite outgrowth. In this study, we defined the potential sequences originating from the G-domain of laminin alpha 1 chain which possess these functional activities. A series of peptides were synthesized from the G-domain, termed LG peptides (LG-1 to LG-6) and were tested far their various biological activities. In the direct [H-3]heparin binding assays, LG-6 (residues 2,335-2,348: KDFLSIELVRGRVK) mediated high levels of [H-3]heparin binding, and this peptide also directly promoted cell adhesion and spreading, including B16F10, M2, HT1080, and PC12 cells. The peptide LG-6 also promoted the neurite outgrowth of PC12 cells, mouse granule cells and chick telencephalic cells. An anti-peptide LG-6 antibody inhibited laminin-1 and peptide LG-6-mediated cell adhesion and neurite outgrowth. Furthermore, an anti-integrin alpha 2 antibody also inhibited the cell adhesion activity. These results suggest that peptide LG-6 plays a functional role as a heparin binding site in the G-domain of the laminin alpha 1 chain, and this sequence was thus concluded to play a crucial role in regulating cell adhesion and spreading and neurite outgrowth which is related to integrin alpha 2. J. Cell. Physiol. 179:18-28, 1999. (C) 1999 Wiley-Liss, Inc.