Isolation and activity of proteolytic fragment of laminin-5 alpha 3 chain

Laminin-5 (alpha3 beta3 gamma2) is an important component of epithelial bas ement membranes. The 190-kDa alpha3 chain undergoes extracellular cleavage within the carboxyl (C) terminus consisting of five globular domains (G1 to G5), producing the mature laminin-5 with the 160-kDa alpha3 chain. To unde rstand the physiological meaning of this processing, we isolated the C-term inal fragments of the alpha3 chain from the conditioned media of two kinds of human cell lines. The amino-terminal sequence of the fragments suggested that the cleavage occurs at Gln(1337)-Asp(1338) in the spacer region betwe en the G3 and G4 domains. The G4-G5 fragment itself did not show significan t activity, but it stimulated cell migration in the presence of a low conce ntration of the mature laminin-5, suggesting its regulatory role in cell mi gration. (C) 2000 Academic Press.