Expression of human plasminogen in Drosophila Schneider S2 cells

The cDNA that encodes full-length human plasminogen (Glu(1)-hPg) has been expressed in Drosophila Schneider S2 cells under the influence of the Drosophila BiP protein signal sequence, which allowed the protein to be secreted into the medium. A procedure was devised for clonal selection of high-expressing cells, which were then used for large-scale expression of 10-15 mg/liter of the protein in the culture medium. The protein produced using this system was extensively characterized and contained full-length recombinant (r) Glu(1)-hPg plasminogen. As with human plasma Glul-hPg, the SE-expressed protein underwent the Cl--induced transition to the tight conformation, which resulted in a weakly activatable zymogen. The addition of the ligand, E-amino caproic acid, induced the relaxed conformation of r-Glu(1)-hPg, which was highly activatable, again in agreement with similar data for human plasma Glu(1)-hPg. The thermal stability of the S2-expressed r-Glu(1)-hPg also correlated well with that of human plasma hPg, These studies show that intact r-Glu(1)-hPg can be produced in high yield in Drosophila Schneider S2 cells, which possesses similar properties to its human plasma counterpart. (C) 1999 Academic Press.