STRUCTURE AND FUNCTION OFLAMININ αa G DOMAIN

摘要

Laminin α4 chain is a component of laminin-8 (α4β1γ1) synthesized by endothelial cells and adipocytes. In order to study the function of laminin-8 during angiogenesis and adipogenesis, we focused on the G domain of α4 chain and found that the subdomain LG4 has highest affinity to heparin among LG1-LG5 subdomain forming the G domain. In order to specify the functional amino acid for the heparin-binding, we produced a fusion protein of α4LG4 with glutathione S-transferase in E. coli and introduced site-directed mutagenesis at 19 basic amino acids (K, R, H). Mapping of the functional basic amino acids on a 3D structure model of α4LG4 showed the heparin-binding surface locating at opposite side of the calcium-binding site. We also found that addition of recombinant α4LG I-LG5 is inhibitory to the de novo adipogenesis induced by subcutaneous injection of Matrigel and basic fibroblast growth factor into mice. α4LG4-5 and α4LGi-LG3 showed stronger inhibition than α4LG1-LG5, suggesting that theG domain of α4 chain in laminin-8 may be cleaved after secretion from endothelial cells and preadipocytes at the boundary between LG3 and LG4 for its function of supporting the adipogenesis by the interaction between endothelial cells and preadipocytes.