PRODUCTION OF ACTIVE HUMAN INTERLEUKIN-1-BETA-CONVERTING ENZYME IN A BACULOVIRUS EXPRESSION SYSTEM

The cDNA coding for the precursor form of human interleukin-1 beta-con verting enzyme (proICE) was expressed in Spodoptera frugiperda (Sf9) i nsect cells using a baculovirus expression system. The 45-kDa recombin ant protein was further processed to several smaller forms of 32, 24, 20, 13 and 10 kDa. Active recombinant ICE derived from the baculovirus expression system (bvICE) was found to be present in soluble lysates of insect cells as an associated heterodimer consisting of 10- and 20- kDa subunits. The activity of bvICE was determined by conversion of pr ecursor interleukin-1 beta (preIL-1 beta) to the mature form (mIL-1 be ta) and via site-specific cleavage of a decapeptide which spans the IC E cleavage site in preIL-1 beta The bvICE system was inhibited by an I CE inhibitor to the same extent as native ICE from the monocytic cell line THP-1. Expression of an active-site mutant (Cys(285) to Ser) of p roICE in insect cells resulted in the accumulation of partially proces sed (32-kDa) ICE. The availability of a facile expression system will permit further characterization of the biochemical properties and proc essing pathway of this unique protease.