Insect cell production of a secreted form of human alpha(1)-proteinase inhibitor as a bifunctional protein which inhibits neutrophil elastase and has growth factor-like activities.

alpha(1)-proteinase inhibitor (API) is a potential therapeutic agent in all diseases in which elastase released by neutrophils has to be effectively neutralized. We ligated the cDNA of human API to the C-terminal section of an insulin-like growth factor II analogue (BOMIGF), known to be properly folded and secreted in insect cells using the baculovirus expression system. The BOMIGF-API chimera was recovered from the incubation medium of the infected cells. It shared the properties of both IGFs and API. It inhibited neutrophil elastase and formed SDS-stable complexes with the enzyme. The attachment of the large API protein to the C-terminal end of the 10 kDa IGF analogue did not destroy the IGF-mediated stimulation of thymidine incorporation into bovine fetal erythroid cells. We tested the capacity of the chimera to affect fibronectin-dependent TF-1 cell migration. BOMIGF-API significantly restored TF-1 cell migration in the presence of elastase, which is the enzyme of burn wound fluid most probably involved in fibronectin degradation. Some of the beneficial uses for this chimera may include all instances for which inhibition of elastase-mediated extracellular matrix destruction as well as stimulation of cell migration and proliferation are required for tissue repair.