Structural requirement of carboxyl-terminal globular domains of laminin alpha 3 chain for promotion of rapid cell adhesion and migration by laminin-5

The basement membrane protein laminin-5, a heterotrimer of laminin alpha 3, beta 3, and gamma 2 chains, potently promotes cellular adhesion and motili ty, It has been supposed that the carboxyl-terminal globular region of the alpha 3 chain consisting of five distinct domains (G1 to G5) is important f or its interaction with integrins, To clarify the function of each G domain , we transfected cDNAs for the full-length (wild type (WT)) and five deleti on derivatives (Delta Gs) of the a3 chain into human fibrosarcoma cell line HT1080, which expressed and secreted the laminin beta 3 and gamma 2 chains but not the alpha 3 chain. The transfectants with the alpha 3 chain cDNAs lacking G5 (Delta G(5)), G4-5 (Delta G(4-5)), G3-5 (Delta G(3-5)), and G2-5 (Delta G(2-5)) secreted laminin-5 variants at levels comparable to that wi th WT cDNA However, the transfectant with the cDNA without any G domains (D elta G(1-5)) secreted little laminin-5, suggesting that the G domains are e ssential for the efficient assembly and secretion of the heterotrimer alpha 3 beta 3 gamma 2, The transfectants with WT, Delta G(5), and Delta G(4-5) cDNAs survived in serum-free medium longer than those with Delta G(3-5), De lta G(2-5), and Delta G(1-5) cDNAs, The transfectants with WT, Delta G(5), and Delta G(4-5) cDNAs secreted apparently the same size of laminin-5, whic h lacked G4 and G5 due to proteolytic cleavage between G3 and G4, and these laminin-5 forms potently promoted integrin alpha(3)beta(1)-dependent cell adhesion and migration, However, the laminin-5 forms of Delta G(3-5) and De lta G(2-5) hardly promoted the cell adhesion and motility, These findings d emonstrate that the G3 domain, but not the G4 and G5 domains, of the alpha 3 chain is essential for the potent promotion of cell adhesion and motility bg laminin-5.