ENHANCED TGF-BETA-1 MATURATION IN HIGH 5 CELLS COINFECTED WITH RECOMBINANT BACULOVIRUS ENCODING THE CONVERTASE FURIN PACE - IMPROVED TECHNOLOGY FOR THE PRODUCTION OF RECOMBINANT PROPROTEINS IN INSECT CELLS/

One important limitation of the widely used insect baculovirus overexp ression system is its inefficiency to properly process heterologous pr oteins which are initially biosynthesized as larger inactive precursor proteins. One example is transforming growth factor beta 1 (TGF beta 1), a 25-kDa homodimeric protein with pleiotropic functions. As many g rowth factors, the inactive TGF beta 1 precursor molecule needs to be proteolytically cleaved C-terminal to a basic sequence to yield the ma ture and active homodimer. In insect cells, a large proportion of over expressed TGF beta 1 was found in an inactive precursor form suggestin g that the levels of endogenous convertases are limiting for the produ ction of mature and bioactive TGF beta 1 in this system. We have demon strated that furin, a member of a novel family of mammalian prohormone convertases (PCs) can efficiently process TGF beta 1 precursor result ing in the production of the mature and active growth factor. Taking a dvantage of this observation, we have developed an improved overproduc tion system for TGF beta 1 by coexpressing prohTGF beta 1 and human fu rin convertase in High Five cells. Using this system, the production o f mature active TGF beta 1 increased in a dose-dependent fashion reach ing up to 7.8-fold the amount obtained with the growth factor only. Th us, eliminating the rate-limiting step in recombinant TGF beta 1 produ ction maximizes its processing efficiency and the yield of the mature active growth factor. Such simple and efficient technology could be us eful for large scale production of other proproteins which undergo sim ilar maturation processes and share furin recognition sequences at the junction between the proregion and the mature polypeptide. (C) 1998 J ohn Wiley & Sons, Inc.