Secretion of single-chain urokinase-type plasminogen activator from insect cells.

Abstract A cDNA encoding human urokinase-type plasminogen activator was inserted downstream from the polyhedrin promoter of the baculovirus Autographa californica nuclear polyhedrosis virus. A protein of similar M r to urokinase (UK) was synthesized and approx. 90% was secreted from recombinant virus-infected Spodoptera frugiperda cells. Zymography and Western blotting analysis of the insect-derived protein demonstrated that it was comprised solely of the high- M r ,- form of UK. No low- M r - UK was detected. Amidolytic activity assays showed that 96 % of the insect cell-derived UK was in the single-chain proenzyme form. The yield of UK from insect cells was 1986 international units/ml/106 infected cells.