BACULOVIRAL EXPRESSION OF A NATURAL INHIBITOR OF THE HUMAN INSULIN-RECEPTOR TYROSINE KINASE

We had earlier reported that the human serum alpha(2)-HS glycoprotein (1) is a physiological and specific inhibitor of the human insulin rec eptor tyrosine kinase (IR-TK). We have now expressed this human protei n in the baculoviral expression system using the Sf-9 and High Five in sect cells. The protein was optimally expressed at 72 h post infection . alpha(2)-HSG(bac) completely inhibited the insulin-stimulated autoph osphorylation and TK activity of partially purified IR preparations. I t also abolished insulin-induced DNA synthesis in the H-35 rat hepatom a cell line. The effective concentration of the baculoviral derived al pha(2)-HSG necessary for inhibiting IR-TK activity was significantly l ower than that of the protein purified from human plasma. (C) 1995 Aca demic Press, Inc.